TOXICOLOGICAL PROFILE FOR NITROPHENOLS: 2-NITROPHENOL 4 -NITROPHENOL Prepared by: Syracuse Research Corporation Under Subcontract to: Clement International Corporation Under Contract No. 205-88-0608 Prepared for: Agency for Toxic Substances and Disease Registry U.S. Public Health Service July 1992 pueL ii DISCLAIMER The use of company or product name(s) is for identification only and does not imply endorsement by the Agency for Toxic Substances and Disease Registry. iii iA (242 FOREWORD Ns ¥ T6897 The Superfund Amendments and Reauthorization Act (SARA) of 1986 | 992 (Public Law 99-499) extended and amended the Comprehensive Environmental puBL Response, Compensation, and Liability Act of 1980 (CERCLA or Superfund). 2 This public law directed the Agency for Toxic Substances and Disease Registry (ATSDR) to prepare toxicological profiles for hazardous substances which are most commonly found at facilities on the CERCLA National Priorities List and which pose the most significant potential threat to human health, as determined by ATSDR and the Environmental Protection Agency (EPA). The lists of the 250 most significant hazardous substances were published in the Federal Register on April 17, 1987; on October 20, 1988; on October 26, 1989; and on October 17, 1990. A revised list of 275 substances was published on October 17, 1991. Section 104(i)(3) of CERCLA, as amended, directs the Administrator of ATSDR to prepare a toxicological profile for each substance on the lists. Each profile must include the following content: (A) An examination, summary, and interpretation of available toxicological information and epidemiological evaluations on the hazardous substance in order to ascertain the levels of significant human exposure for the substance and the associated acute, subacute, and chronic health effects. (B) A determination of whether adequate information on the health effects of each substance is available or in the process of development to determine levels of exposure which present a significant risk to human health of acute, subacute, and chronic health effects. (C) Where appropriate, an identification of toxicological testing needed to identify the types or levels of exposure that may present significant risk of adverse health effects in humans. This toxicological profile is prepared in accordance with guidelines developed by ATSDR and EPA. The original guidelines were published in the Federal Register on April 17, 1987. Each profile will be revised and republished as necessary. The ATSDR toxicological profile is intended to characterize succinctly the toxicological and adverse health effects information for the hazardous substance being described. Each profile identifies and reviews the key literature (that has been peer-reviewed) that describes a hazardous substance’s toxicological properties. Other pertinent literature is also presented but described in less detail than the key studies. The profile is not intended to be an exhaustive document; however, more comprehensive sources of specialty information are referenced. iv Foreword Each toxicological profile begins with a public health statement, which describes in nontechnical language a substance’s relevant toxicological properties. Following the public health statement is information concerning levels of significant human exposure and, where known, significant health effects. The adequacy of information to determine a substance’s health effects is described in a health effects summary. Data needs that are of significance to protection of public health will be identified by ATSDR, the National Toxicology Program (NTP) of the Public Health Service, and EPA. The focus of the profiles is on health and toxicological information; therefore, we have included this information in the beginning of the document. The principal audiences for the toxicological profiles are health professionals at the federal, state, and local levels, interested private sector organizations and groups, and members of the public. This profile reflects our assessment of all relevant toxicological testing and information that has been peer reviewed. It has been reviewed by scientists from ATSDR, the Centers for Disease Control, the NTP, and other federa. agencies. It has also been reviewed by a panel of nongovernment peer reviewers. Final responsibility for the contents and views expressed in this toxicological profile resides with ATSDR. William L. Roper, M.D., M.P.H. Administrator Agency for Toxic Substances and Disease Registry FOREWORD CONTENTS LIST OF FIGURES LIST OF TABLES 1. PUBLIC HEALTH STATEMENT . = kL, 1. 1:1 1. 1.3 2 4 5 6 7 WHAT ARE 2-NITROPHENOL AND 4- NITROPHENOL? HOW MIGHT I BE EXPOSED TO 2-NITROPHENOL AND 4- NITROPHENOL? HOW CAN 2-NITROPHENOL AND 4-NITROPHENOL ENTER AND LEAVE MY BODY? HOW CAN 2- NITROPHENOL AND 4: NITROPHENOL AFFECT MY HEALTH? IS THERE A MEDICAL TEST TO DETERMINE WHETHER I HAVE BEEN EXPOSED TO 2-NITROPHENOL AND 4-NITROPHENOL? . WHAT RECOMMENDATIONS HAS THE FEDERAL GOVERNMENT MADE TO PROTECT HUMAN HEALTH? . WHERE CAN I GET MORE INFORMATION? 2. HEALTH EFFECTS 2. 1 INTRODUCTION . 2.2 DISCUSSION OF HEALTH EFFECTS BY ROUTE OF EXPOSURE 2.2.1 Inhalation Exposure .1. Death . Systemic gfiects Immunological Effects Neurological Effects Developmental Effects Reproductive Effects Genotoxic Effects Cancer . posure Death ‘ Systemic Effects Immunological Effects Neurological Effects Developmental Effects Reproductive Effects Genotoxic Effects Cancer . 1 Exposure Death ' Systemic gltects Immunological Effects Neurological Effects Developmental Effects Reproductive Effects Genotoxic Effects EEE 1 E No. NNN NONNNNNNNOERE RONNNNNNNNNNND NDNNNDNNNDDNDNDDNDN 2.2.2 ONO PH WN X ONL E WN WWWwwwwwwp DMN NDNDN Nouv P wD om - 2.2.3 NRNNNNNNNNNNNONNNNONNMNNNDNNNNONDNDNNDNDNNDNDNDN iii ix xi = 2:3 NNN O 00d vi 2.2.3.8 Cancer . TOXICOKINETICS 2.3.1 Absorption . £m m= wow es 2.3.1.1 Inhalation Exposure 2.3.1.2 Oral Exposure 2.3.1.3 Dermal Exposure 2.3.2 Distribution . . . 2.3.2.1 trhelation Exposure 2.3.2.2 Oral Exposure 2.3.2.3 Dermal Exposure 2.3.2.4 Other Routes of Exposare 2.3.3 Metabolism . 2.3.4 Excretion mom + mow ow Inhalation Exposure Oral Exposure Dermal Exposure Other Routes of Exposure RELEVANCE TO PUBLIC HEALTH . . BIOMARKERS OF EXPOSURE AND EFFECT xX 2 2, 2 2 Wwwwn Ab. oC “A 4, I 2.5.1 Biomarkers Used to Identify and/or Quantify Exposure to 2-Nitrophenol and 4-Nitrophenol . 2.5.2 Biomarkers Used to Characterize Effects Caused "by 2-Nitrophenol and 4-Nitrophenol INTERACTIONS WITH OTHER CHEMICALS : POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE . MITIGATION OF EFFECTS ADEQUACY OF THE DATABASE . . . 2.9.1 Existing Information on Health ‘Effects of 2-Nitrophenol and 4-Nitrophenol 2.9.2 Data Needs 2.9.3 On-going Studies CHEMICAL AND PHYSICAL INFORMATION . 3.1 3.2 PRO 4.1 4.2 4.3 4.4 CHEMICAL IDENTITY PHYSICAL AND CHEMICAL PROPERTIES DUCTION, IMPORT, USE, AND DISPOSAL . PRODUCTION . IMPORT/EXPORT USE DISPOSAL . POTENTIAL FOR HUMAN EXPOSURE 5.1 5.2 OVERVIEW . ’ RELEASES TO THE ENVIRONMENT 5.2.1 Air 5.2.2 Water 5.2.3 Soil . 23 23 23 23 23 24 24 24 24 24 24 25 26 26 26 29 29 29 36 37 37 37 38 38 39 39 40 47 49 49 49 53 53 53 53 55 57 57 58 58 61 61 5.3 5.4 0 Un ~N oy» ANA 6.1 6.2 6.3 vii ENVIRONMENTAL FATE . ‘ 5.3.1 Transport and Peveivioning ; . 5.3.2 Transformation and Degradation . 5.3.2.1 Air 5.3.2.2 Water 5.3.2.3 Soil ELS or Mzases OR ESTIMATED N THE ENVIRONMENT 5. 4. 4 Other Environmental "Media ; GENERAL POPULATION AND OCCUPATIONAL EXPOSURE . POPULATIONS WITH POTENTIALLY HIGH EXPOSURES ADEQUACY OF THE DATABASE . 5.7.1 Data Needs . 5.7.2 On-going Studies LYTICAL METHODS BIOLOGICAL MATERIALS ENVIRONMENTAL SAMPLES ADEQUACY OF THE DATABASE 6.3.1 Data Needs . 6.3.2 On-going Studies REGULATIONS AND ADVISORIES REFERENCES GLOSSARY A. B. C. APPENDICES USER'S GUIDE . ACRONYMS, ABBREVIATIONS, AND SYMBOLS PEER REVIEW 62 62 64 64 65 66 67 67 68 68 69 69 70 70 71 73 75 75 77 77 79 80 81 83 101 B-1 Cc-1 2-6 5-1 ix LIST OF FIGURES Levels of Significant Exposure to 4-Nitrophenol - Inhalation . Levels of Significant Exposure to 2- and 4-Nitrophenol - Oral Proposed Metabolic Pathway for 2-Nitrophenol Proposed Metabolic Pathway for 4-Nitrophenol Existing Information on Health Effects of 2-Nitrophenol Existing Information on Health Effects of 4-Nitrophenol Frequency of NPL Sites with Nitrophenols Contamination . 15 27 28 41 42 59 2-1 2-2 2-3 2-4 3-1 3-2 5-1 6-1 7-1 xi LIST OF TABLES Levels of Significant Exposure to 4-Nitrophenol - Inhalation Levels of Significant Exposure to Nitrophenols - Oral Levels of Significant Exposure to Nitrophenols - Dermal Genotoxicity of 2-Nitrophenol In Vitro Genotoxicity of 4-Nitrophenol In Vitro Chemical Identities of 2-Nitrophenol and 4-Nitrophenol Physical and Chemical Properties of 2-Nitrophenol and 4-Nitrophenol Facilities that Manufacture or Process Nitrophenols Releases to the Environment from Facilities that Manufacture or Process Nitrophenols Analytical Methods for Determining 2-Nitrophenol and 4-Nitrophenol in Biological Materials Lo Analytical Methods for Determining 2-Nitrophenol and 4-Nitrophenol in Environmental Samples Regulations and Guidelines Applicable to 2-Nitrophenol and 4-Nitrophenol 13 19 34 35 50 51 54 60 76 78 82 1. PUBLIC HEALTH STATEMENT This Statement was prepared to give you information about 2-nitrophenol and 4-nitrophenol and to emphasize the human health effects that may result from exposure to them. The Environmental Protection Agency (EPA) has identified 1,177 National Priorities List (NPL) sites. Nitrophenols have been found at 14 of these sites. However, we do not know how many of the 1,177 NPL sites have been evaluated for 2-nitrophenol and 4-nitrophenol. As EPA evaluates more sites, the number of sites at which nitrophenols are found may change. This information is important for you because nitrophenols may cause harmful effects and because these sites are potential or actual sources of human exposure to 2-nitrophenol and 4-nitrophenol. When a chemical is released from a large area, such as an industrial plant, or from a container, such as a drum or bottle, it enters the environment as a chemical emission. This emission, which is also called a release, does not always lead to exposure. You can be exposed to a chemical only when you come into contact with it. You may be exposed to it in the environment by breathing, eating, or drinking substances containing the chemical, or from skin contact with it. If you are exposed to a hazardous substance such as nitrophenols, several factors will determine whether harmful health effects will occur and what the type and severity of those health effects will be. These factors include the dose (how much), the duration (how long), the route or pathway by which you are exposed (breathing, eating, drinking, or skin contact), the other chemicals to which you are exposed, and your individual characteristics such as age, sex, nutritional status, family traits, life style, and state of health. 1.1 WHAT ARE 2-NITROPHENOL AND 4-NITROPHENOL? The two nitrophenols are very similar in their chemical properties. The manufacture of one almost always produces at least a little of the other. Therefore, we include them both in one profile. 2-Nitrophenol is a light yellow solid with a peculiar aromatic smell. 4-Nitrophenol is a colorless to light yellow solid with very little odor. 2-Nitrophenol is slightly soluble in cold water, but 4-nitrophenol is moderately soluble in cold water. Neither chemical evaporates at room temperature. These are man-made chemicals with no evidence of their formation from any natural source. Therefore, humans are solely responsible for the presence of the chemicals in the environment. The main sources of the two chemicals are industrial manufacturing and processing. 2-Nitrophenol is used mainly to produce dyes, paint coloring, rubber chemicals, and substances that kill molds (fungicides). 4-Nitrophenol is used mainly to manufacture drugs, fungicides, and dyes, and to darken leather. The time needed for these two chemicals to disappear chemically in air is not known. They both break down (degrade) in water and surface soil, but the breakdown takes longer at lower soil depths and groundwater. Therefore, they are expected to stay longer in the deep soil of dump sites compared to surface 1. PUBLIC HEALTH STATEMENT soil and may even stay indefinitely in these soils. For more information about their use, disposal methods, and the time needed for environmental breakdown, see Chapters 4 and 5 of this profile. 1.2 HOW MIGHT I BE EXPOSED TO 2-NITROPHENOL AND 4-NITROPHENOL? Small amounts of the two substances can be found in the air, water, and soil. Therefore, breathing air, drinking water, and eating foods grown in soils that contain these substances can expose you to them. The background levels (when no apparent sources of pollution are present) of the two nitrophenols in air are not known. However, in one case, the level of 2-nitrophenol in the air in Portland, Oregon, was 4 parts per trillion (ppt by volume). Its level in the air in Dubendorf, Switzerland, was 61 ppt. These are very small numbers, and exposure from breathing air containing such low levels of these substances may not be very harmful. Except for one case of polluted water, these two substances have not been found in U.S. public drinking waters. The background levels of these compounds in foods eaten by humans are not known either. Because the chemicals break down rapidly, any exposure from these levels will be small. 4-Nitrophenol has been found in the urine of people who did not have any known exposure to this substance. The 4-nitrophenol found in human urine comes from the breakdown within the body of a pesticide, parathion, that is commonly used on certain agricultural products that many of us eat. Some people may be exposed to higher than background levels of nitrophenols. Workers who produce or process these chemicals may be exposed to higher doses, particularly during spills or accidents. Workers involved in cleaning up hazardous waste or spills that contain these chemicals and pesticide applicators are especially subjected to higher than background levels of exposure. People who use certain pesticides or who drink well water near farming areas where certain pesticides are used may also be exposed to higher than background levels of 4-nitrophenol. The two nitrophenols and their mixture have been found in at least 14 of the 1,177 hazardous waste sites on the National Priorities List (NPL). People who live near these sites may be subjected to exposure at higher doses than background. Except for the high levels of 4-nitrophenol found in the urine of persons exposed to the pesticide, parathion, we have no evidence of exposure to 2-nitrophenol and 4-nitrophenol that is higher than background levels. For more information on environmental levels and the possibilities for exposure to these substances, see Chapter 5 of this profile. 1.3 HOW CAN 2-NITROPHENOL AND 4-NITROPHENOL ENTER AND LEAVE MY BODY? 2-Nitrophenol and 4-nitrophenol can enter your body through your lungs and pass into the blood stream if you breathe contaminated air. If you swallow 2-nitrophenol or 4-nitrophenol, most of it probably enters your body and passes from the stomach into the blood stream very quickly (in minutes). If you spill 2-nitrophenol or 4-nitrophenol on your skin, some of it might 3 1. PUBLIC HEALTH STATEMENT pass through the skin into the blood stream, but we do not know how much or how fast. Once inside your body, 2-nitrophenol and 4-nitrophenol change (we call this change metabolism) into other chemicals that will be quickly (in hours) released from the body in your urine. We do not have enough information available to determine which will be the most likely way that 2-nitrophenol or 4-nitrophenol will enter your body if you are exposed at hazardous waste sites. For more information on how 2-nitrophenol and 4-nitrophenol can enter and leave your body, see Chapter 2. 1.4 HOW CAN 2-NITROPHENOL AND 4-NITROPHENOL AFFECT MY HEALTH? How a chemical affects your health depends on how much you are exposed to and for how long. As the level and length of your exposure increase, the effects are likely to become more severe. Rats that breathed dusts of 4-nitrophenol for 2 weeks developed a blood disorder which reduces the ability of the blood to carry oxygen to tissues and organs. However, these abnormalities disappeared a few days after exposure stopped. Chemicals like the nitrophenols cause a similar blood disorder in humans, and so humans exposed for weeks or longer to high levels of nitrophenols may develop the same types of blood disorders that animals do. Experimental studies have shown that 4-nitrophenol is more harmful than 2-nitrophenol in animals. There is no information on the effects on human health from breathing dusts of 2-nitrophenol or 4-nitrophenol. Some rats, mice, and rabbits that swallowed large amounts of 2-nitrophenol or 4-nitrophenol died within a few days, but we do not know the cause of death. Some rats that swallowed smaller amounts of 4-nitrophenol for a few weeks also died, but those that survived had no apparent harmful health effects. No birth defects were found in the offspring of pregnant mice that swallowed 4-nitrophenol. We do not know if swallowing very small amounts of 2-nitrophenol or 4-nitrophenol for many months or years leads to serious disease or death. There is no information on their health effects from humans who ate food or drank water contaminated with these chemicals. Rats and rabbits that had relatively large amounts of 4-nitrophenol applied to their skin for a day or less had skin irritation. Rats that had a small amount of 4-nitrophenol on their skin for a few months also had skin irritation. 4-Nitrophenol also caused eye irritation in rabbits when it was applied to the eye. It appears that exposure of animals to very small amounts of 2-nitrophenol or 4-nitrophenol by skin contact for many months does not lead to serious disease or death. We do not know whether breathing dusts of these chemicals or spilling them on your skin can cause birth defects, affect fertility, or cause cancer. More information on how 2-nitrophenol and 4-nitrophenol can affect health can be found in Chapter 2. 4 1. PUBLIC HEALTH STATEMENT 1.5 IS THERE A MEDICAL TEST TO DETERMINE WHETHER I HAVE BEEN EXPOSED TO 2-NITROPHENOL AND 4-NITROPHENOL? Although methods are available for measuring levels of &4-nitrophenol in the urine and blood, they are probably not useful unless the exposure was very recent. 4-Nitrophenol passes out of the body through urine within a few hours. Because the effects usually seen on the blood may also result from causes besides 4-nitrophenol, these effects alone cannot be used to prove exposure. No tests are available to tell whether you have been exposed to 2-nitrophenol. For more information, see Chapters 2 and 6. 1.6 WHAT RECOMMENDATIONS HAS THE FEDERAL GOVERNMENT MADE TO PROTECT HUMAN HEALTH? In order to minimize exposure to nitrophenols by humans the Environmental Protection Agency (EPA) says that industry must tell the National Response Center when 100 pounds or more of 2-nitrophenol or 4-nitrophenol have been disposed of. For more information on federal and state recommendations, see Chapter 7. 1.7 WHERE CAN I GET MORE INFORMATION? If you have any more questions or concerns not covered here, please contact your state health or environmental department or: Agency for Toxic Substances and Disease Registry Division of Toxicology 1600 Clifton Road, E-29 Atlanta, Georgia 30333 This agency can also provide you with information on the location of the nearest occupational and environmental health clinic. Such clinics specialize in recognizing, evaluating, and treating illnesses that result from exposure to hazardous substances. 2. HEALTH EFFECTS 2.1 INTRODUCTION The primary purpose of this chapter is to provide public health officials, physicians, toxicologists, and other interested individuals and groups with an overall perspective of the toxicology of 2-nitrophenol and 4-nitrophenol and a depiction of significant exposure levels associated with various adverse health effects. It contains descriptions and evaluations of studies and presents levels of significant exposure for 2-nitrophenol and 4-nitrophenol based on toxicological studies and epidemiological investigations. Mononitrophenols exist in three isomeric forms: 2-nitrophenol (or o-nitrophenol), 3-nitrophenol (or m-nitrophenol), and 4-nitrophenol (or p-nitrophenol). Because of a scarcity of toxicological data regarding 3-nitrophenol and because this isomer is much less prevalent in industry and in the environment, only 2-nitrophenol and 4-nitrophenol are discussed in this document. 2.2 DISCUSSION OF HEALTH EFFECTS BY ROUTE OF EXPOSURE To help public health professionals address the needs of persons living or working near hazardous waste sites, the information in this section is organized first by route of exposure--inhalation, oral, and dermal--and then by health effect--death, systemic, immunological, neurological, developmental, reproductive, genotoxic, and carcinogenic effects. These data are discussed in terms of three exposure periods--acute (less than 15 days), intermediate (15-364 days), and chronic (365 days or more). Levels of significant exposure for each route and duration are presented in tables and illustrated in figures. The points in the figures showing no-observed-adverse-effect levels (NOAELs) or lowest-observed-adverse-effect levels (LOAELs) reflect the actual doses (levels of exposure) used in the studies. LOAELs have been classified into "less serious" or "serious" effects. These distinctions are intended to help the users of the document identify the levels of exposure at which adverse health effects start to appear. They should also help to determine whether or not the effects vary with dose and/or duration, and place into perspective the possible significance of these effects to human health. The significance of the exposure levels shown in the tables and figures may differ depending on the user’s perspective. For example, physicians concerned with the interpretation of clinical findings in exposed persons may be interested in levels of exposure associated with "serious" effects. Public health officials and project managers concerned with appropriate actions to take at hazardous waste sites may want information on levels of exposure associated with more subtle effects in humans or animals (LOAEL) or exposure levels below which no adverse effects (NOAEL) have been observed. Estimates 6 2. HEALTH EFFECTS of levels posing minimal risk to humans (Minimal Risk Levels, MRLs) may be of interest to health professionals and citizens alike. Estimates of exposure levels posing minimal risk to humans (MRLs) have been made, where data were believed reliable, for the most sensitive noncancer effect for each exposure duration. MRLs include adjustments to reflect human variability from laboratory animal data to humans. Although methods have been established to derive these levels (Barnes et al. 1988; EPA 1989), uncertainties are associated with these techniques. Furthermore, ATSDR acknowledges additional uncertainties inherent in the application of the procedures to derive less than lifetime MRLs. As an example, acute inhalation MRLs may not be protective for health effects that are delayed in development or are acquired following repeated acute insults, such as hypersensitivity reactions, asthma, or chronic bronchitis. As these kinds of health effect data become available and methods to assess levels of significant human exposure improve, these MRLs will be revised. 2.2.1 Inhalation Exposure Two studies were identified that examined the effects of inhalation exposure to nitrophenols (Hazleton 1983; Smith et al. 1988). These studies described the effects of acute- and intermediate-duration exposure to 4-nitrophenol in rats. The results are presented in relevant sections below. 2.2.1.1 Death No studies were located regarding lethality in humans or animals following inhalation exposure to 2-nitrophenol or in humans following inhalation exposure to 4-nitrophenol. No lethality was observed in male rats exposed to dust atmospheres of 4-nitrophenol (sodium salt) at concentrations of 4,033 mg 4-nitrophenol/m> for a single 4-hour period (Smith et al. 1988), to 2,119 mg 4-nitrophenol/m> for 6 hours/day for 10 days (Smith et al. 1988), or in rats (both sexes) exposed to 30 mg 4-nitrophenol dust/m> for 6 hours/day, 5 days/week for 4 weeks (Hazleton 1983). The NOAELs are recorded in Table 2-1 and plotted in Figure 2-1. 2.2.1.2 Systemic Effects No studies were located regarding systemic effects in humans or animals following inhalation exposure to 2-nitrophenol or in humans following inhalation exposure to 4-nitrophenol. Data regarding systemic effects of 4-nitrophenol following inhalation exposure were limited to two studies. These studies examined the effects of acute- and intermediate-duration exposure of rats to 4-nitrophenol for the following systemic categories: respiratory, cardiovascular, gastrointestinal, TABLE 2-1. Levels of Significant Exposure to 4-Nitrophenol - Inhalation LOAEL (effect) Exposure Key to frequency/ NOAEL Less serious Serious figure? Species duration System (mg/m) (mg/m) (mg/m) Reference ACUTE EXPOSURE Death 1 Rat 2 wk 2,119 Smith et al. 1988 5 d/wk 6 hr/d 2 Rat 1d 4,033 Smith et al. 1988 4 hr/d Systemic 3 Rat 2 wk Resp 2,119 Smith et al. 1988 5 d/wk Cardio 2,119 6 hr/d Gastro 2,119 Hemato 26 112 (methemoglobinemia) Hepatic 2.119 Renal 2,119 Derm/oc 2,119 4 Rat 1d Derm/oc 4,033 (corneal opacity) Smith et al. 1988 4 hr/d INTERMEDIATE EXPOSURE Death 5 Rat 4 wk 30 Hazleton 1983 5 d/wk 6 hr/d Systemic 6 Rat 4 wk Resp 30 Hazleton 1983 5 d/wk Cardio 30 6 hr/d Gastro 30 Musc/sk 30 Hepatic 30 Renal 30 Derm/oc 5 30 (anterior capsular cataract 11/30) Other 30 3The number corresponds to entries in Figure 2-1. d = day; Cardio = cardiovascular; Derm/oc = respiratory; wk = weeks = dermal/ocular; Gastro = gastrointestinal; Hemato = hematological; hr = hours; LOAEL = lowest- observed-adverse-effect level; mg/m” = milligram per cubic meter; Musc/sk = musculoskeletal; NOAEL = no-observed-adverse-effect level; Resp 2 S10344d HITVIH FIGURE 2-1. Levels of Significant Exposure to 4-Nitrophenol - Inhalation ACUTE INTERMEDIATE (<14 Days) 15-364 Days Y y Systemic Systemic CCA @ y SF ® < F & & & & S$ & & & © & : 0 o > A 2 S Xe © 3 X A > , & & & & & & & & & & & & & & & & & (mg/m*) 10,000 p= Qa P+ Or Ox Ox Ox Ox Qa» Ox 1,000 p= 100 | Qo Ox Oss Qs Q& Qs Q& Qs Os @s QO 10 Qer 1 & Key r Rat @ LOAEL for serous effects (animals) (D LOAEL for less serious effects (animals) QO NOAEL (animals) The number next to each point corresponds to entries in Table 2-1. "Z S10d443 HLIVIH 9 2. HEALTH EFFECTS hematological, musculoskeletal, hepatic, renal, dermal/ocular, and other systemic. The highest NOAEL values and all reliable LOAEL values for each systemic effect are recorded in Table 2-1 and plotted in Figure 2-1. Respiratory Effects. Rats exposed to dust atmospheres of 4-nitrophenol (sodium salt) at a concentration of 2,119 mg 4-nitrophenol/m3, 6 hours/day for 10 days showed a decrease in absolute and relative lung weights after a l4-day recovery period (Smith et al. 1988). Since no histopathological changes were noticed, the biological significance of this finding is unclear. A concentration of 292 mg/m? was without effect. The concentration of 2,119 mg/m3, is considered a NOAEL for respiratory effects for acute-duration exposure. Male and female rats exposed to 30 mg 4-nitrophenol dust/m3 6 hours/day, 5 days/week for 4 weeks showed no exposure-related effects on lung weight, or on gross and histological appearance of the lungs, trachea, and nasal turbinates (Hazleton 1983). This exposure level represents a NOAEL for respiratory effects for intermediate-duration exposure. Cardiovascular Effects. No exposure-related histopathological lesions or increased weights were observed in the hearts of male rats exposed for 2 weeks to up to 2,119 mg 4-nitrophenol/m® as dusts of the sodium salt (Smith et al. 1988). Similarly, no cardiac effects were observed in male and female rats exposed intermittently to up to 30 mg of 4-nitrophenol dust/m®> for 4 weeks (Hazleton 1983). These two exposure levels are considered NOAELs for cardiovascular effects for acute- and intermediate-duration exposure, respectively, although no further tests for cardiovascular function were performed. Gastrointestinal Effects. Male rats exposed for 2 weeks to up to 2,119 mg 4-nitrophenol/m3 as dusts of the sodium salt had no histopathological alterations in the esophagus, stomach, small intestine, colon, and cecum (Smith et al. 1988). Similar results were reported in male and female rats exposed to up to 30 mg of 4-nitrophenol dusts/m® for 4 weeks (Hazleton 1983). Hematological Effects. Rats exposed to 112 mg of 4-nitrophenol/m® as 4-nitrophenol sodium salt for 2 weeks showed a significant (p<0.05) increase in methemoglobin, but exposure to 26 mg/m’ was without effect (Smith et al. 1988). After a 14-day recovery period, methemoglobin levels were reduced but had not reached preexposure values. In a similar experimental series, which used exposure concentrations of 292 and 2,119 mg 4-nitrophenol/m3, the increase in methemoglobin was dose-related. Rats exposed to up to 30 mg 4-nitrophenol dusts/m> 6 hours/day, 5 days/week for 4 weeks showed no significant alterations in hematology parameters (Hazleton 1983). Methemoglobin values, however, determined after 2 weeks of exposure, showed great variability, and appeared to be unusually high (greater than 3%) for some unexposed animals (normal is about 0.5%). 10 2. HEALTH EFFECTS Musculoskeletal Effects. Rats exposed to up to 30 mg 4-nitrophenol dusts/m® for 6 hours/day, 5 days/week for 4 weeks showed no exposure-related effects on the gross or microscopical appearance of the femur and skeletal muscles (Hazleton 1983). Hepatic Effects. Slightly increased levels of serum glutamic oxaloacetic transaminase (SGOT) were found in rats exposed for 2 weeks to a dust of 4-nitrophenn) sodium salt at concentrations of 292 and 2,119 mg 4-nitrophenol/m’ (Smith et al. 1988). However, the toxicological significance of the increase is unclear. In addition, no histological evidence of liver damage was found. No exposure-related effects on liver weight or on the gross and histological appearance of the liver was observed in rats exposed to up to 30 mg 4-nitrophenol dusts/m3, 6 hours/day for 4 weeks (Hazleton 1983). In addition, this exposure protocol did not alter serum levels of SGOT or serum glutamic pyruvic transaminase (SGPT). Renal Effects. Rats exposed to 292 or 2,119 mg 4-nitrophenol/m> of 4-nitrophenol dust (sodium salt) for 2 weeks had darker urine and proteinuria (Smith et al. 1988). In the absence of further information, and because no histopathological changes were noticed in the kidneys, the significance of this finding is unclear. Rats exposed to up 30 mg 4-nitrophenol dust/m> for 4 weeks showed no exposure-related effects on kidney weight, or on the gross and microscopical appearance of the kidneys (Hazleton 1983). Dermal/Ocular Effects. Corneal opacity was described in 4 of 6 rats exposed to a concentration of 4,033 mg 4-nitrophenol/m> as 4-nitrophenol dust (sodium salt) for 4 hours (Smith et al. 1988) (see Table 2-1 and Figure 2-1). The effect persisted through a l4-day observation period in one rat. This effect may be due to direct contact of 4-nitrophenol with the cornea and, as such, could also be classified under effects caused by dermal exposure. Exposure to a concentration of 2,119 mg 4-nitrophenol/m® 6 hours/day for 2 weeks was without effect. Unilateral and bilateral diffuse anterior capsular cataracts were observed in male and female rats exposed to 30 mg 4-nitrophenol dust/m? for 4 weeks (Hazleton 1983). This exposure level is presented as a LOAEL for intermediate duration exposure in Table 2-1. An exposure level of 5 mg/m’ was without effect. Other Systemic Effects. No histological alterations were reported in the spleens and thyroid glands of male rats exposed for 2 weeks to up to 2,119 mg 4-nitrophenol/m’ as 4-nitrophenol dust (Smith et al. 1988), but no additional information was provided. No consistent exposure-related effects on Body weight were reported in rats exposed to up to 30 mg &4-nitrophenol dust/m> for 4 weeks (Hazleton 1983). In addition, no gross or histological alterations were observed in the urinary bladder, thyroid and parathyroid glands, pituitary, salivary glands, adrenals, pancreas, and mammary glands (Hazleton 1983). 11 2. HEALTH EFFECTS 2.2.1.3 Immunological Effects No studies were located regarding immunological effects in humans or animals following inhalation exposure to 2-nitrophenol or in humans following inhalation exposure to 4-nitrophenol. No histological alterations were observed in lymph nodes, thymus, and sternal bone marrow of rats exposed for 2 weeks to up to 2,119 mg 4-nitrophenol/m3 as dust of the sodium salt (Smith et al. 1988). Similar results were reported in rats exposed to up to 30 mg 4-nitrophenol dust/m> for 4 weeks (Hazleton 1983). However, since no immunological tests were performed in these studies, reliable NOAELs for immunological effects cannot be determined. 2.2.1.4 Neurological Effects No studies were located regarding neurological effects in humans or animals following inhalation exposure to 2-nitrophenol or in humans following inhalation exposure to 4-nitrophenol. No histological alterations were observed in the brains of rats exposed for 2 weeks to a dust of 4-nitrophenol sodium salt at concentrations of up to 2,119 mg 4-nitrophenol/m3 (Smith et al. 1988). Gross and histological examination of the brain, spinal cord, and peripheral nerves of rats exposed to up to 30 mg 4-nitrophenol dust/m’ for 4 weeks revealed no treatment-related effects (Hazleton 1983). However, since neurological tests were not performed in these studies, reliable NOAELs for neurological effects cannot be determined. 2.2.1.5 Developmental Effects No studies were located regarding developmental effects in humans or animals following inhalation exposure to 2-nitrophenol or 4-nitrophenol. 2.2.1.6 Reproductive Effects No studies were located regarding reproductive effects in humans or animals following inhalation exposure to 2-nitrophenol or in humans following inhalation exposure to 4-nitrophenol. Male rats exposed for 2 weeks to a dust of 4-nitrophenol sodium salt at concentrations of up to 2,119 mg 4-nitrophenol/m? showed no histological alterations in the testes and epididymides (Smith et al. 1988). Rats exposed to up to 30 mg 4-nitrophenol dust/m> for 4 weeks showed no exposure-related effects on the gross or microscopical appearance of the prostate, seminal vesicles, ovaries, or uterus (Hazleton 1983). Nevertheless, since tests for reproductive performance were not conducted in these studies, reliable NOAELs for reproductive effects cannot be determined. 12 2. HEALTH EFFECTS 2.2.1.7 Genotoxic Effects No studies were located regarding genotoxic effects in humans or animals following inhalation exposure to 2-nitrophenol or 4-nitrophenol. Genotoxicity studies are discussed in Section 2.4. 2.2.1.8 Cancer No studies were located regarding the carcinogenic effects in humans or animals following inhalation exposure to 2-nitrophenol or 4-nitrophenol. 2.2.2 Oral Exposure 2.2.2.1 Death No studies were located regarding lethality in humans following oral exposure to 2-nitrophenol or 4-nitrophenol. In rats, the reported oral LDy, values after gavage administration of 2-nitrophenol and 4-nitrophenol in corn oil were 2,830 and 620 mg/kg, respectively (Vernot et al. 1977). An LDs, value of 230 mg/kg was reported in albino rats for 4-nitrophenol administered in propylene glycol (Monsanto 1983a); clinical observations prior to death included convulsions, prostration, and dyspnea. Twenty-three percent lethality was reported in pregnant rats administered a single dose of 667 mg 4-nitrophenol/kg on day 11 of gestation; a dose of 333 mg/kg was without effect (Kavlock 1990). Early mortality was reported in rats administered 70 mg 4-nitrophenol/kg or more by gavage in water for 13 weeks (Hazleton 1989); prostration, wheezing, and dyspnea were noticed prior to death. In mice, LDg, values of 470 mg/kg (Vernot et al. 1977) and 626 mg/kg (Plasterer et al. 1985) have been reported for 4-nitrophenol and 1300 mg/kg for 2-nitrophenol (Vernot et al. 1977) after gavage administration of the chemicals in corn oil. In addition to determining an LDgy in mice, Plasterer et al. (1985) reported that daily gavage doses of 400 mg of 4-nitrophenol/kg administered to pregnant mice during gestation days 7-15 caused 19% lethality. Three deaths were reported in eight female rabbits given 4-nitrophenol in single gavage doses between 182 and 322 mg/kg (Williams 1938); the lowest lethal dose was 220 mg 4-nitrophenol/kg. The cause of death was not indicated in any of these studies. Although the data regarding lethality are limited, 4-nitrophenol is apparently more lethal than 2-nitrophenol. The LDg, values and other doses causing death are recorded in Table 2-2 and plotted in Figure 2-2. 2.2.2.2 Systemic Effects No studies were located regarding systemic effects in humans or animals following oral exposure to 2-nitrophenol. Data regarding systemic effects of TABLE 2-2. Levels of Significant Exposure to Nitrophenols - Oral LOAEL (effect) Exposure Key to frequency/ NOAEL Less serious Serious figure? Species Route duration System (mg/kg/day) (mg/kg/day) (mg/kg/day) Reference Isomer ACUTE EXPOSURE Death 1 Rat (GO) NS 2830 (LDgg) Vernot et al. 1977 2- 2 Rat (GW) 1x 333 667 (3/13 dezths) Kavlock 1920 b= Gd 11 3 Rat (GW) 1x 110 230 (LDgqp) Monsanto 1983a 4= 4 Rat (GO) NS 620 (LDgq) Vernot et al. 1977 4- 5 Rabbit (GW) 1x 220 (3/8) Williams 1938 4- 6 Mouse (GO) 8d 626 (LDgq) Plasterer et al. 4- 1x/d 1985 7 Mouse (GO) NS 1300 (LDgq) Vernot et al. 1977 2- 8 Mouse (GO) 8 d 400 (19%) Plasterer et al. 4- 1x/d 1985 9 Mouse (GO) NS 470 (LDgq) Vernot et al. 1977 4- Developmental 10 Rat (GW) 1x 1000 Kavlock 1990 4- Gd 11 INTERMEDIATE EXPOSURE Death 11 Rat (GW) 13 wk 25 70 (3/13) Hazleton 1989 4- 7 d/wk C $1034143 HITVIH eT TABLE 2-2 (Continued) LOAEL (effect) Exposure Key to frequency/ NOAEL Less serious Serious figure? Species Route duration System (mg/kg/day) (mg/kg/day) (mg/kg/day) Reference Isomer 12 Rat (GW) 13 wk Resp 25 70 (wheezing, Hazleton 1988 4- 7 d/wk dyspnea) Cardio 140 Gastro 140 Musc/sk 140 Hepatic 140 Renal 140 Derm/oc 140 Other 140 The number corresponds to entries in Figure 2-2. Cardio = cardiovascular; d = day; Derm/oc = dermal/ocular; Gastro = gastrointestinal; Gd = gestation day; GO = gavage, oil; GW = gavage, water; LDgq = lethal dose 50% kill; LOAEL = lowest-observed-adverse-effect level; Musc/sk = musculoskeletal; NOAEL = no-observed-adverse- effect level; NS = not specified; Resp = respiratory; wk = week; x = times Z S10d443 HITIVAH KA! FIGURE 2-2. Levels of Significant Exposure to 2- and 4-Nitrophenol - Oral LOAEL for less serious effects (animals) ACUTE INTERMEDIATE (<14 Days) (15-364 Days) Systemic > . > > & AQ Ff # 5 £ © & 2 & &F $ & s ££ & FFF oe & oe Xr 2 > & § S © J & &® &¢ F& & FF ¥ Ff & & (mg/kg/day) 10,000 = Jr Bm 1,000 p= Qtor Hem ox | El am Ox Har @®sh Qt Qiz Qi Ox Qt Ox Ot Oar 100 @r Qi Or Ox Key 105 ro Ra WB 1050 m Moise @ LOAEL for serious effects (animals) h Rabbit 0 O The number next to each point corresponds to entries in Table 2-2. NOAEL (animals) i S103443 HITV3H ST 16 2. HEALTH EFFECTS 4-nitrophenol following oral exposure were limited to a single study (Hazleton 1989). This study examined the effects of intermediate-duration exposure in rats in the following systemic categories: respiratory, cardiovascular, gastrointestinal, hematological, musculoskeletal, hepatic, renal, dermal/ocular, and other systemic. The highest NOAEL values and all reliable LOAEL values for each systemic effect are recorded in Table 2-2 and plotted in Figure 2-2. Respiratory Effects. No histological alterations were observed in the trachea and lungs of rats administered daily doses of up to 140 mg 4-nitrophenol/kg by gavage for 13 weeks (Hazleton 1989). However, wheezing and dyspnea were observed in rats given doses of 70 mg/kg or more that died prematurely during the study. A dose of 25 mg 4-nitrophenol/kg was without effect. Cardiovascular Effects. No gross or histological alterations were reported in the heart and aorta of rats administered up to 140 mg 4-nitrophenol/kg/day by gavage in water for 13 weeks (Hazleton 1989). Gastrointestinal Effects. No treatment-related effects were observed on the gross or microscopical appearance of the esophagus, stomach, duodenum, jejunum, ileum, colon, cecum, and rectum of rats administered up to 140 mg 4-nitrophenol/kg/day by gavage in water for 13 weeks (Hazleton 1989). Hematological Effects. No significant alterations were observed in hematological and clinical chemistry parameters of rats administered up to 140 mg 4-nitrophenol/kg/day for 13 weeks (Hazleton 1989). Methemoglobin values of untreated rats determined at week 7 were unacceptably high, which led the investigators to suggest that the analytical method was not totally reliable; therefore, methemoglobin was not measured at sacrifice. Since methemoglobin formation appears to be the end point with the lowest threshold in rats following inhalation exposure to 4-nitrophenol (Smith et al. 1988), a reliable NOAEL for hematological effects due to oral exposure cannot be determined based on the findings reported by Hazleton (1989). Musculoskeletal Effects. Rats administered up to 140 mg 4-nitrophenol/kg/day by gavage in water for 13 weeks showed no gross or histological alterations in the sternum (Hazleton 1989). In addition, no gross alterations were observed in the cranial cavity. Hepatic Effects. Dark, enlarged, and thicker liver lobes were observed in some rats that died prematurely in a 13-week gavage study with 4-nitrophenol (Hazleton 1989). Early deaths occurred with doses of 70 mg 4-nitrophenol/kg/day or more. However, no gross or histological alterations were observed at sacrifice (13 weeks) in rats that received doses of up to 140 mg 4-nitrophenol/kg/day. Furthermore, serum levels of liver enzymes and bilirubin were unaffected by treatment with 4-nitrophenol. 17 2. HEALTH EFFECTS Renal Effects. Some rats that died early in a 13-week gavage study with 4-nitrophenol had kidney congestion (Hazleton 1989). Early deaths were observed at doses of 70 mg 4-nitrophenol/kg/day or more. Rats administered up to 140 mg 4-nitrophenol/kg/day, and sacrificed at week 13, however, showed no treatment-related effects on gross or histological appearance of the kidneys. Dermal/Ocular Effects. No treatment-related ophthalmological alterations were reported throughout the experimental period in rats administered up to 140 mg 4-nitrophenol/kg/day by gavage for 13 weeks (Hazleton 1989). Other Systemic Effects. Rats administered up to 140 mg 4-nitrophenol/kg/day by gavage for 13 weeks showed no significant effects on body weight gain, or on the gross or microscopical appearance of the salivary glands, pituitary, thyroid and parathyroid glands, adrenals, pancreas, and urinary bladder (Hazleton 1989). 2.2.2.3 Immunological Effects No exposure-related effects were reported on spleen weight, or on the microscopical appearance of spleen, thymus, and lymph nodes of rats administered up to 140 mg 4-nitrophenol/kg/day by gavage for 13 weeks (Hazleton 1989). However, since no immunological tests were performed, a reliable NOAEL for immunological effects cannot be determined. 2.2.2.4 Neurological Effects No exposure-related effects were reported on brain weight, or on the histological appearance of the brain and sciatic nerve of rats given up to 140 mg 4-nitrophenol/kg/day by gavage for 13 weeks (Hazleton 1989). However, since neurological tests were not performed, a reliable NOAEL for neurological effects cannot be determined. 2.2.2.5 Developmental Effects No studies were located regarding developmental effects in humans or animals following oral exposure to 2-nitrophenol or in humans following oral exposure to 4-nitrophenol. No significant effects on litter size, perinatal loss, pup weight, and litter biomass were observed in rats treated with a single gavage dose of up to 1,000 mg/kg of &4-nitrophenol on day 11 of gestation (Kavlock 1990). In addition, no overt malformations were observed, but the pups were not examined for internal malformations. No changes were observed in the reproductive index of pregnant mice given daily doses of 400 mg 4-nitrophenol/kg by gavage during gestation days 7-14 (Plasterer et al. 1985). The 400 mg/kg dose, however, caused 19% maternal lethality. The reproductive index was defined as 18 2. HEALTH EFFECTS the ratio between survivors that delivered and survivors pregnant and is a measure of prenatal lethality. Furthermore, 4-nitrophenol did not affect the number of live pups or the average weight of the pups, and produced no gross anomalies. However, the pups were not examined for internal malformations. The NOAEL value of 1,000 mg/kg for developmental effects is recorded in Table 2-2 and plotted in Figure 2-2. 2.2.2.6 Reproductive Effects No treatment-related effects were observed on testes weight, or on the histological appearance of the testes, ovaries, and uterus of rats administered up to 140 mg 4-nitrophenol/kg/day by gavage for 13 weeks (Hazleton 1989). However, since tests for reproductive performance were not conducted, a reliable NOAEL for reproductive effects cannot be determined. 2.2.2.7 Genotoxic Effects No studies were located regarding genotoxic effects in humans or animals following oral exposure to 2-nitrophenol or 4-nitrophenol. Genotoxicity studies are discussed in Section 2.4. 2.2.2.8 Cancer No studies were located regarding cancer effects in humans or animals following oral exposure to 2-nitrophenol or 4-nitrophenol. 2.2.3 Dermal Exposure 2.2.3.1 Death No studies were located regarding lethality in humans following dermal exposure to 2-nitrophenol or 4-nitrophenol. No lethality was reported among rabbits when a saline suspension of 5,000 mg 4-nitrophenol/kg was applied to the abraded dorsal surface for 24 hours (Monsanto 1983b). The animals were observed for 15 days. No treatment-related deaths were observed in rats treated dermally with doses between 50 and 250 mg/kg/day of 4-nitrophenol for 120 days (Angerhofer 1985). In mice, application of a 47 mg/kg/day dose of 2-nitrophenol or 4-nitrophenol to shaved skin for 12 weeks did not alter the survival rate (Boutwell and Bosch 1959). The NOAELs are recorded in Table 2-3. 2.2.3.2 Systemic Effects No studies were located regarding respiratory, cardiovascular, gastrointestinal, hematological, musculo/skeletal, hepatic, renal, dermal/ocular, or other systemic effects in humans or animals after dermal exposure to 2-nitrophenol or in humans after dermal exposure to 4-nitrophenol. TABLE 2-3. Levels of Significant Exposure to Nitrophenols - Dermal LOAEL (effect) Exposure frequency/ NOAEL Less serious Serious Species duration System (mg/kg/day) (mg/kg/day) (mg/kg/day) Reference Isomer ACUTE EXPOSURE Death Rabbit 24 hr 5,000 Monsanto 1983b 4- Systemic Rabbit 24 hr Derm/oc 181 (skin scabbine Monsanto 1983d 4- and scarring) Rabbit 4 hr Derm/oc 147 (skin erythema Monsanto 1984 4- and edema) Rabbit 1x Derm/oc 27 (corneal Monsanto 1983c 4- cloudiness) Rabbit 24 hr Derm/oc 5,000 (erythema and Monsanto 1983b 4- edema) INTERMEDIATE EXPOSURE Rat 120 d 250 Angerhofer 1985 4- Mouse 12 wk 47 Boutwell and 4- 2 d/wk Bosch 1959 Mouse 12 wk 47 Boutwell and 2=- 2 d/wk Bosch 1958 Systemic Rat 120 d Resp 250 Angerhofer 1985 4- Cardio 250 Gastro 250 Musc/sk 250 Hepatic 250 Renal 250 Derm/oc 50 (skin irritation) A S10344d HITVIH 61 TABLE 2-3 (Continued) LOAEL (effect) Exposure frequency/ NOAEL Less serious Serious Species duration System (mg/kg/day) (mg/kg/day) (mg/kg/day) Reference Isomer Developmental Rat 120 d 250 Angerhofer 1985 by Reproductive Rat 120 d 250 Angerhofer 1985 4- Cardio = cardiovascular; d = day; Derm/oc = level; Musc/sk = musculoskeletal; NOAEL = no-observed-adverse-effect level; Resp = respiratory; wk = week; x = times dermal/ocular; Gastro = gastrointestinal; hr = hour; LOAEL = lowest-observed-adverse-effect "2 S10dd443 HIIVIH 0¢ 21 2. HEALTH EFFECTS No studies were located regarding hematological effects in animals after dermal exposure to 4-nitrophenol. Limited information is available regarding systemic effects in animals following dermal exposure to 4-nitrophenol. The highest NOAEL values and all reliable LOAEL values for each systemic effect are recorded in Table 2-1. Respiratory Effects. No gross or histopathological alterations were observed in the lungs of rats treated dermally with doses of 50-250 mg 4-nitrophenol/kg/day for 120 days (Angerhofer 1985). Cardiovascular Effects. No gross or histological alterations in the heart or changes in heart weight were observed in rats treated dermally with doses of 50-250 mg 4-nitrophenol/kg/day for 120 days (Angerhofer 1985). Gastrointestinal Effects. No gross or histological alterations were seen in the gastrointestinal tract of rats treated dermally with doses of 50-250 mg &4-nitrophenol/kg/day for 120 days (Angerhofer 1985). Musculo/Skeletal. No gross or histological alterations were seen in skeletal muscles and bones of rats treated dermally with doses of 50-250 mg 4-nitrophenol/kg/day for 120 days (Angerhofer 1985). Hepatic Effects. No gross or histological alterations in the liver or changes in liver weight were observed in rats treated dermally with doses of 50-250 mg 4-nitrophenol/kg/day for 120 days (Angerhofer 1985). Renal Effects. No gross or histological alterations in the kidneys or changes in kidneys weight were seen in rats treated dermally with doses of 50-250 mg 4-nitrophenol/kg/day for 120 days (Angerhofer 1985). Dermal/Ocular Effects. Moderate to severe corneal cloudiness, blistered conjunctival tissue, and corneal neovascularization were observed in rabbits after a single application of 27 mg of solid 4-nitrophenol/kg into the conjunctival sac (Monsanto 1983c). Only in one of six rabbits the effects appeared to be reversible during a 21-day observation period. Erythema and edema at the site of application were the most prevalent signs of exposure in rabbits when a saline suspension of 5,000 mg 4-nitrophenol was applied to the abraded dorsal surface for 24 hours (Monsanto 1983b). No adverse effects were noticed in the shaved dorsal surface of rabbits after application of 147 mg of dry solid 4-nitrophenol/kg for 4 hours (Monsanto 1984). However, when the solid 4-nitrophenol was applied moistened with saline, skin erythema and edema were observed. Skin scabbing and scarring were reported in rabbits 14 days after application of 181 mg 4-nitrophenol/kg moistened with saline for 24 hours (Monsanto 1983d). Partial recovery was observed by day 21. Application of 4-nitrophenol in daily doses of 50-250 mg 4-nitrophenol/kg to the skin of rats for 120 days resulted in dose-related dermal irritation 22 2. HEALTH EFFECTS consisting of erythema, scaling, scabbing, and cracking of the skin (Angerhofer 1985). It is possible, however, that the solvent, ethanol, may have contributed to the development of these effects. 2.2.3.3 Immunological Effects No studies were located regarding immunological effects in humans or animals following dermal exposure to 2-nitrophenol or 4-nitrophenol. 2.2.3.4 Neurological Effects No studies were located regarding neurological effects in humans or animals following dermal exposure to 2-nitrophenol or in humans following dermal exposure to 4-nitrophenol. Application of 50-250 mg/kg/day of 4-nitrophenol to the skin of rats for 120 days had no effect on the weight or the gross and microscopic appearance of the brain (Angerhofer 1985). Information regarding the areas of the brain examined was not provided. However, since neurological tests were not performed, a reliable NOAEL for neurological effects cannot be determined. 2.2.3.5 Developmental Effects No studies were located regarding developmental effects in humans or animals following dermal exposure to 2-nitrophenol or in humans following dermal exposure to 4-nitrophenol. In a 2-generation study, dermal application of 4-nitrophenol to rats in doses of 50-250 mg/kg/day for 120 days did not affect the appearance, behavior, or growth of the offspring (Angerhofer 1985). The NOAEL of 250 mg/kg is recorded in Table 2-3. 2.2.3.6 Reproductive Effects No studies were located regarding reproductive effects in humans or animals following dermal exposure to 2-nitrophenol or in humans following dermal exposure to 4-nitrophenol. Reproductive performance was assessed in rats in a 2-generation study in which 4-nitrophenol was applied to the skin of the F. and F, generations in doses of 50-250 mg/kg/day for 120 days (Angerhofer 1985). Fertility (number of pregnancies/number mated), gestation (percentage of pregnancies resulting in birth of live litters), viability (pups surviving at least to day 4 of life), and lactation (pups surviving at least to day 21 of life) were unaffected by treatment with 4-nitrophenol. Histological examination of the reproductive organs of males and females revealed no treatment-related effects. The NOAEL of 250 mg/kg is recorded in Table 2-3. 23 2. HEALTH EFFECTS 2.2.3.7 Genotoxic Effects No studies were located regarding genotoxic effects in humans or animals following dermal exposure to 2-nitrophenol or 4-nitrophenol. Genotoxicity studies are discussed in Section 2.4. 2.2.3.8 Cancer No studies were located regarding carcinogenic effects in humans following dermal exposure to 2-nitrophenol or 4-nitrophenol. Application of 2-nitrophenol or 4-nitrophenol (dissolved in dioxane) to the shaved backs of mice in doses of 47 mg nitrophenol/kg/day for 12 weeks did not induce skin tumors or lesions that could be considered precancerous in nature (Boutwell and Bosch 1959). These results should be interpreted with caution, since no other site was examined and the duration of the study may have been too short for evaluating carcinogenic potential. 2.3 TOXICOKINETICS 2.3.1 Absorption 2.3.1.1 Inhalation Exposure No studies were located regarding the rate and extent of absorption in humans or animals following inhalation exposure to 2-nitrophenol or in humans after inhalation exposure to 4-nitrophenol. Evidence of absorption of 4-nitrophenol by the inhalation route may be inferred from the fact that rats exposed to dusts of 4-nitrophenol (sodium salt) for 2 weeks developed adverse systemic effects (Smith et al. 1988). 2.3.1.2 Oral Exposure No studies were located regarding absorption in humans following oral exposure to 2-nitrophenol or 4-nitrophenol. Indirect evidence of absorption of 2-nitrophenol and 4-nitrophenol has been presented in several animal studies. The sulfate conjugate of 4-nitrophenol was detected in the urine of rabbits after gavage administration of single doses between 182 and 264 mg/kg (Williams 1938). A similar finding was reported by Robinson et al. (195la), who monitored the excretion of nitro compounds and conjugates in the urine of rabbits after gavage doses of both 2-nitrophenol (200-330 mg/kg) and 4-nitrophenol (150-200 mg/kg). Based on excretion data, it was apparent that at least 80%-90% of the dose was rapidly absorbed. In a monkey, oral absorption of 4-nitrophenol was fast since peak blood concentrations of the compound were achieved within minutes after a 24 2. HEALTH EFFECTS gavage dose of 20 mg/kg (Lawford et al. 1954). The extent of absorption was not determined. 2.3.1.3 Dermal Exposure No studies were located regarding absorption in humans or animals following dermal exposure to 2-nitrophenol or in humans following dermal exposure to 4-nitrophenol. In animals, absorption efficiency appeared to be species-specific. In rabbits and beagle dogs, 35% and 11%, respectively, of a dose of “C-labeled 4-nitrophenol dissolved in ethanol and applied to the skin under a patch, was recovered in the urine over 7 days, indicating absorption through the skin (Snodgrass 1983). In the rabbits, the absorption rate was approximately 16% of the dose/day for 2 days, whereas in the dogs the absorption rate was 3% of the dose/day for 2 days. Thus, absorption was more extensive and more rapid in rabbits than in dogs. Unabsorbed 4-nitrophenol accounted for 53% and 86% of the applied dose in the rabbits and dogs, respectively (Snodgrass 1983). 2.3.2 Distribution 2.3.2.1 Inhalation Exposure No studies were located regarding distribution in humans or animals following inhalation exposure to 2-nitrophenol or 4-nitrophenol. 2.3.2.2 Oral Exposure No studies were located regarding distribution in humans or animals following oral exposure to 2-nitrophenol or 4-nitrophenol. 2.3.2.3 Dermal Exposure No studies were located regarding distribution in humans or animals following dermal exposure to 2-nitrophenol or in humans following exposure to 4-nitrophenol. Application of "C-labeled 4-nitrophenol to the skin of rabbits (0.12 mg/kg) and dogs (0.06 mg/kg) resulted in no detectable radioactivity in specimens of all major tissues and organs 7 days later (Snodgrass 1983). No attempt was made to determine distribution at an earlier time following exposure. 2.3.2.4 Other Routes of Exposure Intravenous injection of “C-labeled 4-nitrophenol to rabbits (0.12 mg/kg) or dogs (0.06 mg/kg) resulted in undetectable levels of radioactivity in all major tissues and organs 7 days after treatment (Snodgrass 1983). No 25 2. HEALTH EFFECTS attempt was made to determine distribution at an earlier time. The study by Snodgrass (1983) suggests that following dermal or parenteral exposure, 4-nitrophenol does not bioaccumulate. 2:3.3 Metabolism No studies were located regarding metabolism in humans following inhalation, oral, or dermal exposure to 2-nitrophenol or 4-nitrophenol. Other data, extracted from studies with cultured human cells and perfused human tissues in vitro, are discussed below. The major metabolic route for 2-nitrophenol and 4-nitrophenol is conjugation, with the resultant formation of either glucuronide or sulfate conjugates. Conjugates are more polar than the parent compounds and, therefore, are easier to excrete in the urine. Other possible routes of metabolism include reduction to amino compounds or oxidation to dihydric nitrophenols (catechols). In humans, the evidence is indirect and comes from studies of exposure to the pesticide parathion, of which 4-nitrophenol is a metabolite (Fatiadi 1984). The metabolism of 2-nitrophenol and 4-nitrophenol in rabbits was studied by Robinson et al. (195la), who showed that, with oral doses of 200-300 mg/kg, conjugation with glucuronic and sulfuric acids was almost complete. With both isomers, the major conjugation product excreted in the urine was nitrophenyl- glucuronide, accounting for approximately 70% of the dose. The corresponding sulfate conjugates were also excreted. Slight reduction to amino compounds occurred, 15% of the dose for the 4-isomer and 2%-3% for the 2-isomer. Oxidation products were also found in the urine; less than 1% of the 4-nitrophenol dose was oxidized to 4-nitrocatechol, whereas less than 1% of the 2-nitrophenol dose was detected as nitroquinone. Similar results have been obtained in rats after intravenous administration of 4-nitrophenol (Machida et al. 1982). The glucuronide and sulfate conjugates could be detected in the plasma within 1 minute after the injection of doses between 1.6 and 8.0 mg/kg. Machida et al. (1982) also demonstrated that rat liver homogenates had the greatest amount of glucuronidation activity, followed by the kidney, lung, and small intestine homogenates, in decreasing order. Sulfation, however, was detected almost exclusively in the liver. No differences in conjugation mechanisms for 4-nitrophenol between male and female rats have been reported (Meerman et al. 1987). The metabolism of 4-nitrophenol has also been studied in perfused organ preparations. Perfusion of human kidneys (isolated from cadavers) with 4-nitrophenol resulted in the formation of the glucuronide and sulfate conjugates (Diamond et al. 1982). Sulfate conjugates were found predominantly in mice livers perfused with low concentrations (4 pM) of 4-nitrophenol (Sultatos and Minor 1985). However, as the concentration of 4-nitrophenol was 26 2. HEALTH EFFECTS increased, unchanged 4-nitrophenol and the glucuronide appeared in the effluent, indicating the presence of saturation kinetics. In perfused rat livers, three factors appeared to act as rate-determining for conjugation of 4-nitrophenol: concentration of &4-nitrophenol, supply of uridine diphosphate- glucuronic acid from carbohydrates for glucuronyltransferase, and activity of the enzyme (Reinke et al. 1981). Furthermore, the extent of liver conjugation in the rat was found to be modulated by the sympathetic nervous system through the hepatic nerves (Beuers et al. 1986). Conjugation of 4-nitrophenol also occurred in cultured skin epithelial cells from humans (Rugstad and Dybing 1975), in isolated rat hepatocytes (Araya et al. 1986; Moldeus et al. 1976; Tonda and Hirata 1983), and in microsomes isolated from dog livers (Nakano et al. 1986). Schemes of tentative metabolic pathways for 2-nitrophenol and 4-nitrophenol are presented in Figures 2-3 and 2-4, respectively. 2.3.4 Excretion 2.3.4.1 Inhalation Exposure No studies were located regarding excretion in humans or animals following inhalation exposure to 2-nitrophenol or 4-nitrophenol. 2.3.4.2 Oral Exposure No studies were located regarding excretion in humans following oral exposure to 2-nitrophenol or 4-nitrophenol. As part of a study to compare the extent of sulfonation between phenol and substituted phenols, Williams (1938) reported that administration of doses between 182 and 264 mg/kg of 4-nitrophenol by gavage to rabbits resulted in excretion of approximately 25% of the dose in the urine as sulfate conjugate in less than a week. This finding was later confirmed by Robinson et al. (1951a), who showed that a dose of 150-200 mg 4-nitrophenol/kg given to rabbits was excreted in the urine, 70% as glucuronide and 12-20% as ethereal sulfate. In another experimental series, Robinson et al. (195la) showed that in rabbits the urinary excretion of nitro compounds is almost complete in 1 day after oral administration of a dose of 200 mg/kg of 4-nitrophenol by gavage. The unchanged nitro group accounted for nearly 90% of the dose, whereas approximately 15% was reduced to amino compounds. In another series, Robinson et al. (195la) found that less than 1% of a dose of 250 mg/kg of 4-nitrophenol was excreted in the urine oxidized to 4-nitrocatechol. Using the same experimental protocols, Robinson et al. (195la) demonstrated that when the rabbits were given 2-nitrophenol, the unchanged nitro group accounted for approximately 80% of the dose and 2-3% was detected as amino compounds. Nearly 70% of the dose was excreted as glucuronide and 27 2. HEALTH EFFECTS FIGURE 2-3. Proposed Metabolic Pathway for 2-Nitrophenol* OH 2-Aminophenol fo) NH, NO, Nitroquinone pd ’ Reduction OH ~~ Oxidation NO, OY 2-Nitrophenol UDP - g'ucuronyltransferase 0 Sulfotransferase Mixed Function ~~ Mixed Function HO -S- © Oxygenase Oxygenase o-CHP ; Il NO NO Sulfate oY 2 or 2 conjugale G lucuronyl conjugate *Adapted from Robinson et al. 1951a 28 2. HEALTH EFFECTS FIGURE 2-4. Proposed Metabolic Pathway for 4-Nitrophenol* OH OH OH 4-Aminophenol 4-Nitrocatechol NH, NO, Reouutio) OH Hydroxylation 4-Nitrophenol NO, 0 Sulfotransferase UDP - glucuronyltransferase I Mixed Function Mixed Function HO -S- O Oxygenase Oxygenase o- CH 0, I Sulfate Glucuronyl conjugate conjugate NO NO *Adapted from Robinson et al. 1951a 29 2. HEALTH EFFECTS 10% as ethereal sulfate. Less than 1% was found oxidized to nitroquinone. The rapid elimination of nitrophenols may be due to the formation of conjugates, which, by being more polar than the parent compounds, are readily excreted in the urine. 2.3.4.3 Dermal Exposure No studies were located regarding excretion in humans or animals following dermal exposure to 2-nitrophenol or humans following dermal exposure to 4-nitrophenol. Dermal application of '“C-labeled 4-nitrophenol to dogs resulted in 11% of the dose (radioactive label) excreted in the urine over a period of 7 days. Fecal elimination was negligible. In rabbits, 78% of an absorbed dermal dose of 4C-labeled 4-nitrophenol appeared in the urine in 1 day. As in dogs, fecal elimination accounted for less than 1% of the absorbed dose (Snodgrass 1983). 2.3.4.4, Other Routes of Exposure Rats injected intravenously with a dose of 8.3 mg/kg of 4-nitrophenol excreted 35% of the dose as sulfate conjugate and 40% as glucuronide over a period of 24 hours (Meerman et al. 1987). No differences were noticed between males and females. Dogs given an intravenous dose (0.06 mg/kg) of “C-labeled 4-nitrophenol excreted 92% of the dose (labeled C) in the urine in the first day (Snodgrass 1983). Radioactivity in the feces accounted for approximately 1% over a 7-day period. Snodgrass (1983) used the same protocol in rabbits and found that 78% of the dose (0.12 mg/kg) was recovered in the urine within day 1; excretion was essentially complete by day 4. Fecal elimination accounted for less than 1% of the dose. 2.4 RELEVANCE TO PUBLIC HEALTH No information was located regarding the effects of 2-nitrophenol or 4-nitrophenol in humans after inhalation, oral, or dermal exposure. The only toxicological signs of probable relevance are hematological effects observed in animals exposed to 2-nitrophenol or &4-nitrophenol. These effects were reported in an acute duration inhalation study. Limited longer-term inhalation and oral data were available for 4-nitrophenol. Oral lethal doses for the two isomers have been identified. From acute lethality studies, it appears that 2-nitrophenol is less toxic than 4-nitrophenol, but little additional information was available regarding the 2-isomer. Aside from the hematological effects, no other specific systems or organs have been identified as targets for 2-nitrophenol or 4-nitrophenol. Dermal and ocular effects of 4-nitrophenol have been identified, but are most likely nonspecific irritation. Since no human data were available, the relevance to public health of the effects observed in animals is not known. Studies that examined the effects of nitrophenols in animals used exposure levels that are several 30 2. HEALTH EFFECTS orders of magnitude higher than those at which humans will be generally exposed. Lack of adequate data precluded the derivation of an MRL for acute inhalation exposure to 4-nitrophenol. A concentration-related increase in methemoglobin was reported in rats in the acute inhalation study by Smith et al. (1988). However, inconsistencies in the values obtained in two different experimental series, the unknown toxicological significance of the methemoglobin increase, and the preliminary nature of the report were factors that greatly diminished the power of the study. Although supporting studies with 4-nitrophenol in other species were not located, nitroaromatic compounds are known inducers of methemoglobin both in humans and animals (Beard and Noe 1981; Ellenhorn and Barceloux 1988). An MRL for intermediate-duration inhalation exposure to 4-nitrophenol was not derived due to inconsistent methemoglobin values among the various subgroups of rats in the Hazleton (1983) study. Furthermore, methemoglobin was not monitored at terminal sacrifice (after 20 exposures). Since methemoglobin formation appears to be the most sensitive end point affected by 4-nitrophenol (Smith et al. 1988), other end points examined in this study were not selected for derivation of an intermediate-duration inhalation MRL. MRLs for chronic-duration inhalation exposure for 4-nitrophenol, or for any inhalation exposure duration for 2-nitrophenol are precluded by the lack of data. MRLs for acute- and chronic- duration oral exposure to 2-nitrophenol and 4-nitrophenol, and for intermediate-duration oral exposure to 2-nitrophenol could not be derived due to lack of data. Results from the study by Hazleton (1989) were not used for derivation of an MRL for intermediate-duration oral exposure to 4-nitrophenol due to uncertainty regarding the monitoring of methemoglobin. In this study, unexposed rats had unusually high methemoglobin values, suggesting that problems existed with the analytical method used. Increased methemoglobin was the most sensitive end point in rats exposed to 4-nitrophenol for 2 weeks (Smith et al. 1988). Acute-duration, intermediate-duration, and chronic- duration dermal MRLs were not derived for 2-nitrophenol or 4-nitrophenol due to the lack of an appropriate methodology for the development of dermal MRLs. Death. No information regarding human fatalities due to inhalation, oral, or dermal exposure to 2-nitrophenol or 4-nitrophenol was located in the literature. Concentrations and doses causing death in animals have been reported for acute oral exposure to 2-nitrophenol and 4-nitrophenol, subchronic oral exposure to 4-nitrophenol, and acute dermal exposure to 4-nitrophenol. The cause of death was not reported. Acute oral toxicity data (LDgq) reveal that 4-nitrophenol is considerably more toxic than 2-nitrophenol. No reports of lethality related to inhalation exposure to either 2-nitrophenol or 4-nitrophenol were located. The available information on the lethality of the nitrophenols is insufficient to assess the relevance to human health. 31 2. HEALTH EFFECTS Systemic Effects. No studies were located regarding systemic effects in humans after inhalation, oral, or dermal exposure to 2-nitrophenol or 4-nitrophenol. Respiratory Effects. A decrease in absolute and relative lung weight was noted in rats exposed to 2,119 mg 4-nitrophenol dust/m? for two weeks (Smith et al. 1988). Since histological examination of the lungs failed to reveal any morphological damage, the significance of the weight change is unclear. The existing evidence suggests that the respiratory system is not a target for acute or intermediate inhalation exposure to 4-nitrophenol. Wheezing, dyspnea, and lung congestion reported in rats receiving 70 mg 4-nitrophenol/kg/day or more orally were most likely due to terminal hypoxia and not to a specific effect on the respiratory system (Hazleton 1983). This conclusion is supported by the fact that rats surviving until sacrifice (13 weeks) did not show gross or microscopical alterations in the respiratory tract. The available information on respiratory effects of 4-nitrophenol is insufficient to assess the relevance to human health. Hematological Effects. A relevant hematological effect, observed in rats, is the induction of methemoglobinemia after acute inhalation exposure to 112 mg 4-nitrophenol dust/m3 for 2 weeks (Smith et al. 1988). Although this finding was reported in only one study, it appears relevant because aromatic amino and nitro compounds are known for causing the formation of methemoglobin in humans and animals (Beard and Noe 1981). Inconsistent methemoglobin values arising from possible analytical problems precluded a reliable assessment of hematological effects of intermediate-duration exposure of rats to 4-nitrophenol dust (Hazleton 1983) or to oral doses of 4-nitrophenol in an intermediate-duration study (Hazleton 1989). Hepatic Effects. Rats exposed to a dust of 4-nitrophenol at concentrations of 292 and 2,119 mg 4-nitrophenol/m? for 2 weeks had a slight increase in serum levels of SGOT (Smith et al. 1988). However, the significance of this effect is unclear. Furthermore, no histological evidence of liver damage was observed. Similar results were reported in rats exposed to 30 mg 4-nitrophenol dust/m3 for 4 weeks (Hazleton 1983) and in rats administered oral doses of up to 140 mg 4-nitrophenol/kg for 13 weeks (Hazleton 1989). The existing evidence indicates that the liver is not a target for 4-nitrophenol after acute- and intermediate-duration exposures. The available information regarding hepatic effects of 4-nitrophenol in animals is insufficient to assess the potential for hepatic effects in humans exposed to 2-nitrophenol or 4-nitrophenol. Renal Effects. Proteinuria and darker urine were observed in rats that inhaled a dust of 4-nitrophenol at concentrations of 292 and 2,119 mg 4-nitrophenol/m3 for 2 weeks (Smith et al. 1988). These findings could not be interpreted as unequivocal evidence of kidney damage since they can also be present under unrelated conditions. Furthermore, no histological alterations 32 2. HEALTH EFFECTS were found in the kidneys. Similar findings were reported in rats exposed to 30 mg 4-nitrophenol dust/m> for 4 weeks (Hazleton 1983). Kidney congestion was reported in rats that died prematurely in a 13-week gavage study (Hazleton 1989), but this effect was most likely caused by terminal hypoxia, since rats that survived did not exhibit kidney lesions at sacrifice. The available information regarding renal effects of 4-nitrophenol in animals is insufficient to assess the potential for renal effects in humans exposed to 2-nitrophenol or 4-nitrophenol. Dermal/Ocular Effects. Two studies were located that described dermal/ocular effects in rats after inhalation exposure. In one study, rats exposed to 4,033 mg 4-nitrophenol dust/m? for 4 hours developed corneal opacity (Smith et al. 1988). The second study reported anterior capsular cataracts in rats exposed to 30 mg 4-nitrophenol dust/m® for 4 weeks (Hazleton 1983). Corneal opacity was also reported in rabbits after a single local application of 27 mg 4-nitrophenol/kg (Monsanto 1983c). It is, therefore, possible that the effect seen in the Smith et al. (1988) study was caused by direct contact of the 4-nitrophenol dusts with the cornea rather than by inhalation of the 4-nitrophenol. Similarly, cataracts reported by Hazleton (1983) are likely to have been caused by direct contact with 4-nitrophenol; however, a systematic effect cannot be totally excluded. Application of single doses of 147 mg 4-nitrophenol or more to the skin of rabbits (Monsanto 1984), or of 50 mg 4-nitrophenol/kg/day or more for 120 days to the skin of rats (Angerhofer 1985) resulted in skin irritation. It is important to point out that 4-nitrophenol was much more toxic to the skin when applied moistened with saline than when the dry solid was used. The evidence available suggests that 4-nitrophenol may cause dermal and eye irritation when applied locally in humans. Neurological Effects. No information was identified regarding neurological effects in humans or animals following exposure to 2-nitrophenol or in humans following exposure to 4-nitrophenol. Inhalation exposure of rats to 2,119 mg 4-nitrophenol dust/m3 (sodium salt) for 2 weeks (Smith et al. 1988) or to 30 mg 4-nitrophenol dust/m3 for 4 weeks (Hazleton 1983) did not affect brain weight or the gross or histological appearance of the central and peripheral nervous system. Similar lack of effects were reported in rats administered oral doses of 140 mg 4-nitrophenol/kg/day for 13 weeks (Hazleton 1989). It must be mentioned, however, that none of these studies conducted tests for neurological function. The available information is insufficient to assess the potential for neurological effects in humans exposed to 2-nitrophenol or 4-nitrophenol. Developmental Effects. No studies were located that examined the developmental effects of 2-nitrophenol in humans or animals or 4-nitrophenol in humans. In a 3-generation study, dermal application of 4-nitrophenol to rats, in doses of 50-250 mg/kg for 120 days that included the gestation period, did not affect the appearance, behavior or growth of the offspring 33 2. HEALTH EFFECTS (Angerhofer 1985). Oral administration of 400 mg/kg of 4-nitrophenol to mice during gestation did not alter the reproductive index, a measure of prenatal death (Plasterer et al. 1985). However, in the latter study, the teratogenic potential of 4-nitrophenol could not be dismissed. In the absence of further information, no inference regarding possible effects in humans can be made. Reproductive Effects. It is not known whether 2-nitrophenol or 4-nitrophenol could cause reproductive effects in humans. Rats exposed to 30 mg 4-nitrophenol/m3 for 4 weeks (Hazleton 1983) or administered 140 mg 4-nitrophenol/kg/day for 13 weeks (Hazleton 1989) had no treatment-related effects on the weight or histopathology of the reproductive organs, but reproductive performance was not assessed. In a 2-generation study in rats, dermal application of 4-nitrophenol in doses of 50-250 mg/kg for 120 days did not alter reproductive performance. The relevance of this information to human health is not known. Data regarding the reproductive effects of 2-nitrophenol were not available. Genotoxic Effects. No studies were located regarding the genotoxic effects of 2-nitrophenol or 4-nitrophenol in humans or animals by inhalation, oral, or dermal routes. 4-Nitrophenol was not mutagenic in vivo as judged by the dominant lethal assay and the host-mediated assay in mice (Buselmaier et al. 1973). No information was available regarding mutagenicity of 2-nitrophenol in vivo. As indicated in Table 2-4, 2-nitrophenol did not increase the frequency of reverse mutations in Salmonella typhimurium or in Escherichia coli in the presence or absence of metabolic activation, nor did it induce DNA damage when tested in Bacillus subtilis. No data were available regarding genotoxic properties of 2-nitrophenol in eukaryotic organisms. The in vitro genotoxicity of 4-nitrophenol has been investigated in prokaryotic organisms and in mammalian cell systems. The overall evidence indicates that 4-nitrophenol is not mutagenic in the presence or absence of activating systems in S. typhimurium and E. coli (Table 2-5). One positive result was reported by Shimizu and Yano (1986), who showed that 4-nitrophenol induced DNA damage when tested in B. subtilis by the rec assay. According to the authors (Shimizu and Yano 1986), this assay appears to be more sensitive for nitro compounds in general than the standard Ames Test. Weaker genotoxic effects were reported in two studies (Adler et al. 1976; Garrett and Lewtas 1983). The hypothesis that reduction of the nitro group is required to observe mutagenic effects was tested by Dellarco and Prival (1989). These authors did not observe an increase in mutagenicity when 2-nitrophenol or 4-nitrophenol was incubated in the presence of $-9 and flavin mononucleotide mixture in S. typhimurium. 4-Nitrophenol was not mutagenic when tested in mammalian cells with or without metabolic activation. The in vitro and in vivo information, negative data or lack of data, respectively, would suggest that 2-nitrophenol or 4-nitrophenol does not pose a genotoxic threat to humans. TABLE 2-4. Genotoxicity of 2-Nitrophenol In Vitro Result With Without Species (test system) End point activation activation Reference Prokaryotic organisms: Salmonella typhimurium (plate incorporation) Gene mutation No data - Chiu et al. 1978 S. typhimurium (plate incorporation) Gene mutation - = Suzuki et al. 1983 S. typhimurium (plate incorporation) Gene mutation - = Dellarco and Prival 1989 S. typhimurium (plate incorporation) Gene mutation - - Shimizu and Yano 1986 Escherichia coli sd-4-73 (spot test) Gene mutation No data - Szybalski 1958 Bacillus subtilis (plate incorporation) DNA damage No data - Shimizu and Yano 1986 - = negative result C S10dd43 HITIVAH ve TABLE 2-5. Genotoxicity of &4-Nitrophenol In Vitro Result With Without Species (test system) End point activation activation Reference Prokaryotic organisms: Salmonella typhimurium (plate incorporation) Gene mutation - Suzuki et al. 1983 S. typhimurium (plate incorporation) Gene mutation - = Probst. et al. 1981 S. typhimurium (plate incorporation) Gene mutation = - Haworth et al. 1983 S. typhimurium (plate incorporation) Gene mutation - ~ Shimizu and Yano 1986 S. typhimurium (plate incorporation) Gene mutation - - Dellarco and Prival 1989 Escherichia coli (plate incorporation) Gene mutation - = Probst et al. 1981 E. coli (spot test) Gene mutation - > Syzbalski 1958 E. coli (plate incorporation) Prophage induction - No data Ho and Ho 1981 Proteus mirabilis (plate incorporation) DNA damage No data (t+) Adler et al. 1976 E.coli (disc assay) DNA repair No data - Rashid and Mumma 1986 S. typhimurium (disc assay) DNA repair No data = Rashid and Mumma 1986 Bacillus subtilis (plate incorporation) DNA damage No data + Shimizu and Yano 1986 Mammalian cells: Rat hepatocytes (culture) DNA repair No data = Probst et al. 1981 Mouse lymphoma cells Forward mutation - - Oberly et al. 1984 Mouse lymphoma cells Forward mutation - No data Amacher and Turner 1982 Chinese hamster ovary cells (culture) Inhibition of No data (+) Garrett and Lewtas 1983 DNA synthesis positive result negative result (+) = weakly positive result + non C S10344d HITVIH Gg 36 2. HEALTH EFFECTS Cancer. No studies were located regarding the carcinogenic potential of 2-nitrophenol or 4-nitrophenol in humans by any route of exposure or in animals by the inhalation or oral route. Neither isomer induced tumors when applied to the backs of mice in doses of 47 mg/kg/day for 12 weeks (Boutwell and Bosch 1959). However, since no other site was examined and the duration of the study was only 12 weeks, the results should be interpreted with caution. The relevance of this information to human health is unknown. NTP (1991) recently conducted a review of a 2-year skin painting study with 4-nitrophenol in mice. The panel concluded that under the conditions of the study, there was no evidence of carcinogenic activity in male or female Swiss- Webster mice receiving doses of up to 160 mg 4-nitrophenol/kg for 78 weeks. 2.5 BIOMARKERS OF EXPOSURE AND EFFECT Biomarkers are broadly defined as indicators signaling events in biologic systems or samples. They have been classified as markers of exposure, markers of effect, and markers of susceptibility (NAS/NRC 1989). A biomarker of exposure is a xenobiotic substance or its metabolite(s) or the product of an interaction between a xenobiotic agent and some target molecule(s) or cell(s) that is measured within a compartment of an organism (NAS/NRC 1989). The preferred biomarkers of exposure are generally the substance itself or substance-specific metabolites in readily obtainable body fluid(s) or excreta. However, several factors can confound the use and interpretation of biomarkers of exposure. The body burden of a substance may be the result of exposures from more than one source. The substance being measured may be a metabolite of another xenobiotic substance (e.g., high urinary levels of phenol can result from exposure to several different aromatic compounds). Depending on the properties of the substance (e.g., biologic half-life) and environmental conditions (e.g., duration and route of exposure), the substance and all of its metabolites may have left the body by the time biologic samples can be taken. It may be difficult to identify individuals exposed to hazardous substances that are commonly found in body tissues and fluids (e.g., essential mineral nutrients such as copper, zinc, and selenium). Biomarkers of exposure to 2-nitrophenol and 4-nitrophenol are discussed in Section 2.5.1. Biomarkers of effect are defined as any measurable biochemical, physiologic, or other alteration within an organism that, depending on magnitude, can be recognized as an established or potential health impairment or disease (NAS/NRC 1989). This definition encompasses biochemical or cellular signals of tissue dysfunction (e.g., increased liver enzyme activity or pathologic changes in female genital epithelial cells), as well as physiologic signs of dysfunction such as increased blood pressure or decreased lung capacity. Note that these markers are often not substance specific. They also may not be directly adverse, but can indicate potential health 37 2. HEALTH EFFECTS impairment (e.g., DNA adducts). Biomarkers of effects caused by 2-nitrophenol and 4-nitrophenol are discussed in Section 2.5.2. A biomarker of susceptibility is an indicator of an inherent or acquired limitation of an organism's ability to respond to the challenge of exposure to a specific xenobiotic substance. It can be an intrinsic genetic or other characteristic or a preexisting disease that results in an increase in absorbed dose, biologically effective dose, or target tissue response. If biomarkers of susceptibility exist, they are discussed in Section 2.7, "POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE." 2.5.1 Biomarkers Used to Identify and/or Quantify Exposure to 2-Nitrophenol and 4-Nitrophenol No studies were located regarding levels of 2-nitrophenol or 4-nitrophenol in human tissues, fluids, or excreta that were associated with exposure to nitrophenols. To assess exposure to the pesticide parathion, of which 4-nitrophenol is a metabolite, several methods have been developed to monitor 4-nitrophenol in human urine (Arterberry et al. 1961; Fatiadi 1984). In general, it is agreed that these methods are not suitable indicators for studying the severity of the intoxication caused by parathion (or perhaps nitrophenols) or the appearance of toxic signs; rather, these methods indicate acute exposure to the pesticide (or nitrophenols) (Arterberry et al. 1961; Pena-Egido et al. 1988). The reason is that 2-nitrophenol and 4-nitrophenol conjugates are completely and rapidly excreted in the urine. Therefore, unless a very high dose is given, urinary levels will fall to near zero in a short time (48 hours). It is not known if urinary excretion of 2-nitrophenol or 4-nitrophenol (or their conjugates) can be associated quantitatively with exposure to these chemicals. 2.5.2 Biomarkers Used to Characterize Effects Caused by 2-Nitrophenol and 4-Nitrophenol No toxic signs specific to 2-nitrophenol or 4-nitrophenol exposure have yet been identified. However, nitro aromatic and amino compounds in general are known to induce formation of methemoglobin in humans and experimental animals (Beard and Noe 1981). Although response varies considerably among species, it appears that 2-nitrophenol and 4-nitrophenol are not among the most potent methemoglobin inducers. Furthermore, methemoglobinemia can also be caused by inherited disorders and a number of drugs including sulfonamides and benzocaine. 2.6 INTERACTIONS WITH OTHER CHEMICALS No studies were located regarding interactions of 2-nitrophenol or 4-nitrophenol with other chemicals in vitro or regarding interactions of 2-nitrophenol with other chemicals in vivo. However, it was reported that, in ethanol-treated rats, 4-nitrophenol is rapidly metabolized to 4-nitrocatechol, which competes with 4-nitrophenol for the formation of sulfate and glucuronide conjugates (Reinke and Moyer 1985). This prevention of the conjugation of 38 2. HEALTH EFFECTS 4-nitrophenol may lead to the formation of amino derivatives, which can then induce methemoglobinemia. 2.7 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE Human populations that have experienced health effects from exposure to 2-nitrophenol or 4-nitrophenol have not been identified, but little research has been conducted on this subject. Based on results from animal studies, as described in Section 2.6, it is possible that individuals who consume ethanol may have slower rates of clearance of 4-nitrophenol. This subpopulation, if exposed to 4-nitrophenol, may be considered potentially susceptible. Furthermore, newborn infants utilize fetal hemoglobin, which has reduced oxygen-carrying capacity, and also have low levels of nicotinamide adenine dinucleotide diaphorase, which continuously reduces methemoglobin; therefore, infants (as well as individuals congenitally deficient in this enzyme) may represent unusually susceptible subpopulations. Data regarding health effects in humans exposed to 2-nitrophenol were not available. 2.8 MITIGATION OF EFFECTS This section will describe clinical practice and research concerning methods for reducing toxic effects of exposure to nitrophenols. However, because some of the treatments discussed may be experimental and unproven, this section should not be used as a guide for treatment of exposures to nitrophenols. When specific exposures have occurred, poison control centers and medical toxicologists should be consulted for medical advice. No studies were located regarding health effects induced by nitrophenols in humans. However, studies in animals exposed to nitrophenols (Smith et al. 1988) and data regarding toxicity of other related compounds (nitrates/nitrites) in humans and animals (see ATSDR 1991) indicate that the major effect of absorption of high amounts of nitrophenols would be an increased formation of methemoglobin in red blood cells. Methemoglobin results from iron in the ferrous state being oxidized to the ferric state. Methemoglobin is unable to combine reversibly with oxygen and carbon dioxide and also causes a shift in the oxygen dissociation curve toward increased oxygen affinity, preventing the transfer of oxygen from the blood to the tissues. Clinical effects of methemoglobinemia are closely related to the percentage of methemoglobin in the blood (see ATSDR 1991). Concentrations up to 20% cause central cyanosis, but are usually asymptomatic. With higher methemoglobin concentrations, CNS depression (headache, dizziness, fatigue, lethargy) and dyspnea may develop. Methemoglobin levels over 45% lead to hypotension, cardiac arrhythmias, metabolic acidosis, and shock. Further CNS depression may cause convulsions, coma, and eventually death. Newborn infants are especially susceptible to methemoglobin induced effects (see Section 2.7). 39 2. HEALTH EFFECTS In addition, ethanol consumers and individuals with certain enzyme deficiencies may be susceptible (see Section 2.6 and 2.7). The initial steps following removal of the individual from the exposure source are skin- cleansing, if dermal exposure is suspected. A caution should be employed with the administration of emetics (syrup of ipecac) in cases when ingestion of nitrophenols is suspected (Ellenhorn and Barceloux 1988; Stutz and Janusz 1988). Emesis has been suggested to be followed by administration of a suspension of activated charcoal in water to bind any toxicant remaining in the gastrointestinal tract. Subsequent steps have been aimed at chemically reducing methemoglobin back to oxyhemoglobin. A commonly used intervention for reducing methemoglobin is intravenous infusion of a solution of methylene blue (Ellenhorn and Barceloux 1988). Methylene blue acts as a cofactor to increase the chemical reduction of methemoglobin in the red blood cells in the presence of nicotinamide adenine dinucleotide (NADPH) (Ellenhorn and Barceloux 1988). Methylene blue is oxidized to leukomethylene blue, which donates electrons for the nonenzymatic reduction of methemoglobin to oxyhemoglobin. Administration of oxygen has been suggested in all cases of nitrophenols poisoning. In addition, standard control for convulsions and arrhythmias has been proposed. In life-threatening situations, hyperbaric oxygen therapy and blood transfusion have been recommended (see ATSDR 1991). 2.9 ADEQUACY OF THE DATABASE Section 104(i) (5) of CERCLA, as amended, directs the Administrator of ATSDR (in consultation with the Administrator of EPA and agencies and programs of the Public Health Service) to assess whether adequate information on the health effects of 2-nitrophenol and 4-nitrophenol is available. Where adequate information is not available, ATSDR, in conjunction with the National Toxicology Program (NTP), is required to assure the initiation of a program of research designed to determine the health effects (and techniques for developing methods to determine such health effects) of 2-nitrophenol and 4-nitrophenol. The following categories of possible data needs have been identified by a joint team of scientists from ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that, if met, would reduce or eliminate the uncertainties of human health assessment. In the future, the identified data needs will be evaluated and prioritized, and a substance-specific research agenda will be proposed. 2.9.1 Existing Information on Health Effects of 2-Nitrophenol and 4-Nitrophenol The existing data on health effects of inhalation, oral, and dermal exposure of humans and animals to 2-nitrophenol and 4-nitrophenol are summarized in Figures 2-5 and 2-6, respectively. The purpose of these figures is to illustrate the existing information concerning the health effects of 2-nitrophenol and 4-nitrophenol. Each dot in the figure indicates that one or 40 2. HEALTH EFFECTS more studies provide information associated with that particular effect. The dot does not imply anything about the quality of the study or studies. Gaps in this figure should not be interpreted as "data needs" information. As seen from Figures 2-5 and 2-6, no information is available regarding the health effects of either 2-nitrophenol or 4-nitrophenol in humans. The only information available regarding 2-nitrophenol is provided by two studies that determined the oral LD;, in rats and mice, and a dermal cancer study. Data are available in animals for lethality after inhalation, oral, or dermal exposure to 4-nitrophenol. One study reported effects of 4-nitrophenol after acute inhalation exposure; however, assessing the significance of most of the effects, such as immunological, neurological, and developmental (or lack thereof), is difficult due to the incomplete examination of some end points. Data were available for systemic effects after oral exposure to 4-nitrophenol, and one pilot study examined developmental effects of this isomer. A limited number of dermal studies provided information concerning lethality, systemic effects after intermediate exposure, and developmental and reproductive effects of 4-nitrophenol. Information regarding the carcinogenicity of 4-nitrophenol was available from a single dermal study. 2.9.2 Data Needs Acute-Duration Exposure. No data were located indicating specific organs or systems as targets for 2-nitrophenol or 4-nitrophenol in humans by any route of exposure. However, amino and nitro aromatic compounds in general have been known to induce methemoglobinemia in humans (Beard and Noe 1981). The data in experimental animals were insufficient to derive oral and inhalation MRLs. Information is lacking regarding the cause of death in the acute- duration studies, most of which have been conducted in rats. The significance of the renal effects, identified in the only acute-duration inhalation study available (Smith et al. 1988), could be clarified with a better designed acute inhalation study. Additional acute-duration studies by the oral and dermal routes would provide information on interspecies differences seen for dermal absorption and on the mechanisms of lethality, as well as on the thresholds for systemic toxicity due to acute-duration exposure for both 2-nitrophenol and 4-nitrophenol, particularly 2-nitrophenol. Careful dose-response studies on the effect of nitrophenols on the development of methemoglobinemia, in multiple species, both sexes, and at multiple doses, would provide information on an effect that is relevant to humans. Studies in rabbits could provide data on what appears to be the most sensitive species, as judged by data on acute lethality by the oral route (Williams 1938). The limited pharmacokinetic data do not suggest route- specific target organs. Because 2-nitrophenol and 4-nitrophenol are rapidly removed from the circulation and excreted (see Chapter 2.3), they will not 41 2. HEALTH EFFECTS FIGURE 2-5. Existing Information on Health Effects of 2-Nitrophenol EYSISMIC oS & o/ &//E < & & & & / & <7 5 Inhalation Oral Dermal HUMAN S SST / or S/S : 5°, & ) & & & &, Inhalation Oral ® Dermal ® ANIMAL @ Existing Studies 42 2. HEALTH EFFECTS FIGURE 2-6. Existing Information on Health Effects of 4-Nitrophenol SYSTEMIC > -O & Cd & © & & LO s/o ESS SESS ESS 5 ed & & 5 & & & K & & Q AS & O £ ~F 38 (4-NP) Diamond and Quebbemann (4-NP and its conjugates) >35 1979 (conjugates) Plasma Vortexed with methanol and HPLC-UV no data >98 (4-NP) Diamond and Quebbemann supernatant concentrated >95 1979 (4-NP and its conjugates) (conjugates) Urine 4-Ethoxynitrobenzene obtained GC-EC 10 ug/L No data Kirby et al. 1979 by method of Shafik et al. (1973) reduced and converted to amide by heptafluorobutyric anhydride (4-NP) Urine Acid hydrolysis, extraction, spectrophotometric 30 pg in 92-100 Fatiadi 1984 and complexation with o-cresol sample in presence of TiCly (4-NP) GC-EC = gas chromatography-electron capture detection HPLC-UV = high-pressure liquid chromatography-ultraviolet detection 4-NP = 4-nitrophenol 9 SAQOHLIAW TVOILATVNV 9L 77 6. ANALYTICAL METHODS 6.2 ENVIRONMENTAL SAMPLES Analytical methods for determining 2-nitrophenol and 4-nitrophenol in environmental samples are given in Table 6-2. The handling methods for environmental samples are given in EPA, 1982. The nitrophenols probably exist predominantly in the vapor phase in the air (see Chapter 5.3.1), but small amounts of both compounds have been detected in the particulate phase (Leuenberger et al. 1985; Nojima et al. 1983). Therefore, the best method for collecting nitrophenols in air is to use an air sampler that uses glass-fiber filters to collect the particulate matter, followed by adsorption cartridges for trapping the volatile components (Leuenberger et al. 1985). Methods that are designed for multicomponent analysis use sample extraction with organic solvent(s) under both acidic and basic conditions. Nitrophenols, being acidic, are found in the acidic extract. In a recent evaluation of the EPA- approved method 625, a single continuous extraction at pH 2 was most efficient for determining both acidic and basic/neutral components in a sample. Additionally, the use of fused silica capillary columns may enhance both the efficiency and detection limits of various components, including nitrophenols, in multicomponent analytical methods such as the EPA method 625 (Valkenburg et al. 1989). Among the commonly used methods, GC with electron capture detection of the heptafluorobutyryl derivative provides the greatest sensitivity. However, the GC-MS method has the most versatility and is more suitable where multicomponent analysis is required. Several other less commonly used methods are available for determining 2-nitrophenol and 4-nitrophenol in environmental samples. Some of these methods are spectrometric measurement in the presence of crown ethers (Papadoyannis et al. 1983), coulometric measurement with methylviologen radical cation (Lozano et al. 1989), HPLC-surface-enhanced resonance Raman scattering (Ni et al. 1989), GC-FID (flame ionization detector) with a special graphitized carbon black as the GC stationary phase (Mangani et al. 1986), remote fluorescence analysis of ground water with UV lasers and fiber optics (Chudyk et al. 1985), HPLC with diode-array UV-visible detector (Nielen et al. 1985), and cyclic voltammetric determination by the addition of a-cyclodextrin (Matsue et al. 1981). 6.3 ADEQUACY OF THE DATABASE Section 104(i) (5) of CERCLA, as amended, directs the Administrator of ATSDR (in consultation with the Administrator of EPA and agencies and programs of the Public Health Service) to assess whether adequate information on the health effects of 2-nitrophenol and 4-nitrophenol is available. Where adequate information is not available, ATSDR, in conjunction with the National Toxicology Program (NTP), is required to assure the initiation of a program of research designed to determine the health effects (and techniques for developing methods to determine such health effects) of 2-nitrophenol and 4-nitrophenol. TABLE 6-2. Analytical Methods for Determining 2-Nitrophenol and 4-Nitrophenol in Environmental Samples Sample detection Percent Sample matrix Preparation method Analytical method limit recovery Reference Air Thermal desorption of cartidge FSCC-MS/DS No data No data Leuenberger et al. 1985 Air Extract filter, clean extract, GC-MS No data No data Nojima et al. 1983 treated with diazomethane and concentrated Waste water Extract, clean extract, GC-EC 0.77 ug/L 67 (2-NP) EPA 1982 derivatized with pentafluoro- (EPA Method 604) (2-NP) 45 (4-NP) benzyl bromide 0.70 ug/L (4-NP) Water Extract, concentrated and HPLC-UV 1 ug/L 81-88 Roseboom et al. 1981 mixed with hexadecyltrimethyl- (4-NP) ammonium bromide and K,CO, Water Resin sorption, desorption, and HPLC-UV 0.18 ug/L 97.4-105.7 Borys 1981 concentration (for 10 mL) Water Sample reacted with iodine Absorbance at 240 nm 3 ug/L No data Bosch et al. 1987 monobromide, extract (4-nitrophenol) Water Extract, derivatized with GC-EC 0.01 ug/L 73 (2-NP) Bengtsson 1985 heptafluorobutyryl anhydride (2-NP) 40-43 and concentrate 0.01 ug/L (4-NP) (4-NP) Water Extract, clean extract, GC-MS/Ds 1 ug/L No data Sporstoel et al. 1985 concentrate (2-NP) 5 ug/L (4-NP) Water, waste water Extract, concentrate GC-MS (EFA Method 625) 3.6 ng/L 75 both EPA 1982 (2-NP) in water and 2.4 ug/L waste water (4-NP) (for 2-NP) 41 in water and 43 in waste water (for 4-NP) Sediment/soil Extract, concentrate, and GC-MS (EPA CLP method) 330 ng/kg No data EPA 1988b clean-up (2-NP) 1600 pg/kg (4-NP) CLP = contract laboratory program; EC = electron capture detection; FSCC-MS/DS = fused silica capillary, mass spectrometry/data system; GC = gas chromatography; HPLC-UV = high-resolution liquid chromatography - ultraviolet detection; 2-NP = 2-nitrophenol; 4-NP = 4-nitrophencol ‘9 SAOHLIAW TVOILATVNV 8L 79 6. ANALYTICAL METHODS The following categories of possible data needs have been identified by a joint team of scientists from ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that, if met, would reduce or eliminate the uncertainties of human health assessment. In the future, the identified data needs will be evaluated and prioritized, and a substance-specific research agenda will be proposed. 6.3.1 Data Needs Methods for Determining Biomarkers of Exposure and Effect. No biomarker that can be associated quantitatively with exposure to 2-nitrophenol or 4-nitrophenol has been identified (see Section 2.5). If a biomarker for these compounds in a human tissue or fluid were available and a correlation were found to exist between the level of biomarker and exposure/health effect, the biomarker could be used as an indication of health effects caused by the exposure of these chemicals. No specific effects of 2-nitrophenol or 4-nitrophenol exposure have yet been identified (see Section 2.5.2). Methods for Determining Parent Compounds and Degradation Products in Environmental Media. Analytical methods with good sensitivity and specificity for determining the two compounds in contaminated water and soil are available (see Table 6-2). Dr. Milton Lee of Brigham Young University has recently developed an analytical method for the quantification of femtogram quantities of nitrophenols in air using time-of-flight mass spectrometer (Sin et al. 1991). Besides this method, analytical methods for the determination of low levels of nitrophenols found in ambient air and data on the accuracies, precisions, and sensitivities of such methods are lacking. The levels of these two compounds in drinking water have very rarely been measured. It is not clear whether this limitation in data is due to lack of effort directed to measure the levels, lack of method sensitivity, or the presence of these compounds at extremely low levels. Analytical methods are available for determining most of the final biodegradation and photodegradation products of these compounds (Raymond and Alexander 1971; Sethunathan 1973; Zeyer and Kearney 1984). However, the accuracy and precision of these methods have rarely been established. The intermediate products remain unknown or unidentified in many cases. The levels of the parent compounds in different environmental media can be used to indicate exposure to these compounds by humans through the inhalation of air and ingestion of foods and drinking water, when the typical volume of air inhaled and drinking water consumed daily and the daily average amount and composition of adult total diet samples are known (Gartell et al. 1986). If a correlation between the levels of these compounds in human tissue and the levels of exposure could be found, the exposure levels from different environmental sources could be used to estimate human body burden. Similarly, determining degradation products is important because it may assist in the need for evaluating the toxicity of the products 80 6. ANALYTICAL METHODS and determining the persistence of the parent compound. In instances where the products of an environmental reaction are more toxic than the parent compound, it is important that the level of the degradation products in the environment be known. 6.3.2 On-going Studies The Environmental Health Laboratory Sciences Division of the Center for Environmental Health and Injury Control, Centers for Disease Control, is developing methods for the analysis of 2-nitrophenol and 4-nitrophenol and other phenolic compounds in urine. These methods use high resolution gas chromatography and magnetic sector mass spectrometry which gives detection limits in the low parts per billion range. No other on-going studies pertaining to the determination of the nitrophenols in biological or environmental media were found. 81 7. REGULATIONS AND ADVISORIES Table 7-1 summarizes national and state regulations and guidelines on human exposure to 2-nitrophenol and 4-nitrophenol. The Clean Water Effluent Guidelines regulate 2-nitrophenol and 4-nitrophenol for the following industrial point sources: electroplating, organic chemicals production, steam electric power generation, asbestos product manufacturing, timber products processing, metal finishing, paving and roofing, ink formulating, carbon black manufacturing, and electrical and electronic components manufacturing (EPA, 1988a). In addition, 4-nitrophenol is regulated for the following industrial point sources: metal molding and casting, paint formulating, and gum and wood chemicals manufacturing (EPA 1988a). 82 7. REGULATIONS AND ADVISORIES TABLE 7-1. Regulations and Guidelines Applicable to 2-Nitrophenol and 4-Nitrophenol Agency Description Information References NATIONAL a. Water: EPA OWRS Priority pollutant effluent limitations EPA 1888c (40 and pretreatment standards for BAT, CFR 414) NSPS and PSES Maximum for any 1 day 231 ug/L (2-nitrophenol) Maximum monthly average 65 ug/L (2-nitrophenol) Maximum for any 1 day 576 ug/L (4-nitrophenol) Maximum monthly average 162 ug/L (4-nitrophenol) b. Other: EPA OERR Keportable quantity, final rule 100 1b EPA 1888d (40 (2-nitrophenol and 4-nitrophenol) CFR 302.4) EPA OSW Designation of Hazardous Substances Yes EPA 1888e (40 (mixture) CFR 116.4) Listing as hazardous waste: Discarded Yes EPA 1888f (40 commercial chemical products CFR 261.33) off-specification species, container residues, and spill residues thereof (4-nitrophenol) Listing as Hazardous Waste Contituent Yes EPA 1988f (4C (4-nitrophenol) CFR 261, Appendix VIII) EPA OTS Toxic Chemical Release Reporting; Yes EPA 1988g (40 Community Right-to-Know CFR 372.65) (2-nitrophenol and 4-nitrophenol) STATE Regulations and Guidelines: a. Air: Acceptable ambient air concentrations New York (4-nitrophenol) South Carolina (4-nitrophenol) b. 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Ecotoxicol Environ Safety 7:179-190. 99 8. REFERENCES *Young DR. 1978. Priority pollutants in municipal wastewaters. Annual Report. South California Coastal Water Research Project, University of California, La Jolla, CA, 103-112. *Zaidi BR, Murakami Y, Alexander M. 1988. Factors limiting success of inoculation to enhance biodegradation of low concentrations of organic chemicals. Environ Sci Technol 22:1419-1425. *Zaidi BR, Murakami Y, Alexander M. 1989. Predation and inhibitors in lake water affect the success of inoculation to enhance biodegradation of organic chemicals. Environ Sci Technol 23:859-863. *Zeyer J, Kearney PC. 1984. Degradation of o-nitrophenol and m-nitrophenol by a Pseudomonas putida. J Agric Food Chem 32:238-242. 101 9. GLOSSARY Acute Exposure -- Exposure to a chemical for a duration of 14 days or less, as specified in the Toxicological Profiles. Adsorption Coefficient (K, ) -- The ratio of the amount of a chemical adsorbed per unit weight of organic carbon in the soil or sediment to the concentration of the chemical in solution at equilibrium. Adsorption Ratio (Kd) -- The amount of a chemical adsorbed by a sediment or soil (i.e., the solid phase) divided by the amount of chemical in the solution phase, which is in equilibrium with the solid phase, at a fixed solid/solution ratio. It is generally expressed in micrograms of chemical sorbed per gram of soil or sediment. Bioconcentration Factor (BCF) -- The quotient of the concentration of a chemical in aquatic organisms at a specific time or during a discrete time period of exposure divided by the concentration in the surrounding water at the same time or during the same period. Cancer Effect Level (CEL) -- The lowest dose of chemical in a study, or group of studies, that produces significant increases in the incidence of cancer (or tumors) between the exposed population and its appropriate control. Carcinogen -- A chemical capable of inducing cancer. Ceiling Value -- A concentration of a substance that should not be exceeded, even instantaneously. Chronic Exposure -- Exposure to a chemical for 365 days or more, as specified in the Toxicological Profiles. Developmental Toxicity -- The occurrence of adverse effects on the developing organism that may result from exposure to a chemical prior to conception (either parent), during prenatal development, or postnatally to the time of sexual maturation. Adverse developmental effects may be detected at any point in the life span of the organism. Embryotoxicity and Fetotoxicity -- Any toxic effect on the conceptus as a result of prenatal exposure to a chemical; the distinguishing feature between the two terms is the stage of development during which the insult occurred. The terms, as used here, include malformations and variations, altered growth, and in utero death. EPA Health Advisory -- An estimate of acceptable drinking water levels for a chemical substance based on health effects information. A health advisory is not a legally enforceable federal standard, but serves as technical guidance to assist federal, state, and local officials. 102 9. GLOSSARY Immediately Dangerous to Life or Health (IDLH) -- The maximum environmental concentration of a contaminant from which one could escape within 30 min without any escape-impairing symptoms or irreversible health effects. Intermediate Exposure -- Exposure to a chemical for a duration of 15-364 days as specified in the Toxicological Profiles. Immunologic Toxicity -- The occurrence of adverse effects on the immune system that may result from exposure to environmental agents such as chemicals. In Vitro -- Isolated from the living organism and artificially maintained, as in a test tube. In Vivo -- Occurring within the living organism. Lethal Concentration ,, (LC,,) -- The lowest concentration of a chemical in air which has been reported to have caused death in humans or animals. Lethal Concentration gg (LCsy) -- A calculated concentration of a chemical in air to which exposure for a specific length of time is expected to cause death in 50% of a defined experimental animal population. Lethal Dose, o, (LD, ) -- The lowest dose of a chemical introduced by a route other than inhalation that is expected to have caused death in humans or animals. Lethal Dose 5, (LDgy) -- The dose of a chemical which has been calculated to cause death in 50% of a defined experimental animal population. Lethal Time gy, (LTgy) -- A calculated period of time within which a specific concentration of a chemical is expected to cause death in 50% of a defined experimental animal population. Lowest-Observed-Adverse-Effect Level (LOAEL) -- The lowest dose of chemical in a study, or group of studies, that produces statistically or biologically significant increases in frequency or severity of adverse effects between the exposed population and its appropriate control. Malformations -- Permanent structural changes that may adversely affect survival, development, or function. Minimal Risk Level -- An estimate of daily human exposure to a chemical that is likely to be without an appreciable risk of deleterious effects (noncancerous) over a specified duration of exposure. 103 9. GLOSSARY Mutagen -- A substance that causes mutations. A mutation is a change in the genetic material in a body cell. Mutations can lead to birth defects, miscarriages, or cancer. Neurotoxicity -- The occurrence of adverse effects on the nervous system following exposure to chemical. No-Observed-Adverse-Effect Level (NOAEL) -- The dose of chemical at which there were no statistically or biologically significant increases in frequency or severity of adverse effects seen between the exposed population and its appropriate control. Effects may be produced at this dose, but they are not considered to be adverse. Octanol-Water Partition Coefficient (K_) -- The equilibrium ratio of the concentrations of a chemical in n-octanol and water, in dilute solution. Permissible Exposure Limit (PEL) -- An allowable exposure level in workplace air averaged over an 8-hour shift. qq* -- The upper-bound estimate of the low-dose slope of the dose-response curve as determined by the multistage procedure. The q;* can be used to calculate an estimate of carcinogenic potency, the incremental excess cancer risk per unit of exposure (usually pg/L for water, mg/kg/day for food, and pg/m> for air). Reference Dose (RfD) -- An estimate (with uncertainty spanning perhaps an order of magnitude) of the daily exposure of the human population to a potential hazard that is likely to be without risk of deleterious effects during a lifetime. The RfD is operationally derived from the NOAEL (from animal and human studies) by a consistent application of uncertainty factors that reflect various types of data used to estimate RfDs and an additional modifying factor, which is based on a professional judgment of the entire database on the chemical. The RfDs are not applicable to nonthreshold effects such as cancer. Reportable Quantity (RQ) -- The quantity of a hazardous substance that is considered reportable under CERCLA. Reportable quantities are (1) 1 1b or greater or (2) for selected substances, an amount established by regulation either under CERCLA or under Sect. 311 of the Clean Water Act. Quantities are measured over a 24-hour period. Reproductive Toxicity -- The occurrence of adverse effects on the reproductive system that may result from exposure to a chemical. The toxicity may be directed to the reproductive organs and/or the related endocrine system. The manifestation of such toxicity may be noted as alterations in sexual behavior, fertility, pregnancy outcomes, or modifications in other functions that are dependent on the integrity of this system. 104 9. GLOSSARY Short-Term Exposure Limit (STEL) -- The maximum concentration to which workers can be exposed for up to 15 min continually. No more than four excursions are allowed per day, and there must be at least 60 min between exposure periods. The daily TLV-TWA may not be exceeded. Target Organ Toxicity -- This term covers a broad range of adverse effects on target organs or physiological systems (e.g., renal, cardiovascular) extending from those arising through a single limited exposure to those assumed over a lifetime of exposure to a chemical. Teratogen -- A chemical that causes structural defects that affect the development of an organism. Threshold Limit Value (TLV) -- A concentration of a substance to which most workers can be exposed without adverse effect. The TLV may be expressed as a TWA, as a STEL, or as a CL. Time-Weighted Average (TWA) -- An allowable exposure concentration averaged over a normal 8-hour workday or 40-hour workweek. Toxic Dose (TDgq) -- A calculated dose of a chemical, introduced by a route other than inhalation, which is expected to cause a specific toxic effect in 50% of a defined experimental animal population. Uncertainty Factor (UF) -- A factor used in operationally deriving the RfD from experimental data. UFs are intended to account for (1) the variation in sensitivity among the members of the human population, (2) the uncertainty in extrapolating animal data to the case of human, (3) the uncertainty in extrapolating from data obtained in a study that is of less than lifetime exposure, and (4) the uncertainty in using LOAEL data rather than NOAEL data. Usually each of these factors is set equal to 10. APPENDIX A USER'S GUIDE Chapter 1 Public Health Statement This chapter of the profile is a health effects summary written in nontechnical language. Its intended audience is the general public especially people living in the vicinity of a hazardous waste site or substance release. If the Public Health Statement were removed from the rest of the document, it would still communicate to the lay public essential information about the substance. The major headings in the Public Health Statement are useful to find specific topics of concern. The topics are written in a question and answer format. The answer to each question includes a sentence that will direct the reader to chapters in the profile that will provide more information on the given topic. Chapter 2 Tables and Figures for Levels of Significant Exposure (LSE) Tables (2-1, 2-2, and 2-3) and figures (2-1 and 2-2) are used to summarize health effects by duration of exposure and endpoint and to illustrate graphically levels of exposure associated with those effects. All entries in these tables and figures represent studies that provide reliable, quantitative estimates of No-Observed-Adverse-Effect Levels (NOAELs), Lowest-Observed- Adverse-Effect Levels (LOAELs) for Less Serious and Serious health effects, or Cancer Effect Levels (CELs). In addition, these tables and figures illustrate differences in response by species, Minimal Risk Levels (MRLs) to humans for noncancer end points, and EPA's estimated range associated with an upper-bound individual lifetime cancer risk of 1 in 10,000 to 1 in 10,000,000. The LSE tables and figures can be used for a quick review of the health effects and to locate data for a specific exposure scenario. The LSE tables and figures should always be used in conjunction with the text. The legends presented below demonstrate the application of these tables and figures. A representative example of LSE Table 2-1 and Figure 2-1 are shown. The numbers in the left column of the legends correspond to the numbers in the example table and figure. LEGEND See LSE Table 2-1 (1). Route of Exposure One of the first considerations when reviewing the toxicity of a substance using these tables and figures should be the relevant and appropriate route of exposure. When sufficient data exist, (2). (3). (4). (5). (6). (7). (8). 9). A-2 APPENDIX A three LSE tables and two LSE figures are presented in the document. The three LSE tables present data on the three principal routes of exposure, i.e., inhalation, oral, and dermal (LSE Table 2-1, 2-2, and 2-3, respectively). LSE figures are limited to the inhalation (LSE Figure 2-1) and oral (LSE Figure 2-2) routes. Exposure Duration Three exposure periods: acute (14 days or less); intermediate (15 to 364 days); and chronic (365 days or more) are presented within each route of exposure. In this example, an inhalation study of intermediate duration exposure is reported. Health Effect The major categories of health effects included in LSE tables and figures are death, systemic, immunological, neurological, developmental, reproductive, and cancer. NOAELs and LOAELs can be reported in the tables and figures for all effects but cancer. Systemic effects are further defined in the "System" column of the LSE table. Key to Figure Each key number in the LSE table links study information to one or more data points using the same key number in the corresponding LSE figure. In this example, the study represented by key number 18 has been used to define a NOAEL and a Less Serious LOAEL (also see the two "18r" data points in Figure 2-1). Species The test species, whether animal or human, are identified in this column. Exposure Frequency/Duration The duration of the study and the weekly and daily exposure regimen are provided in this column. This permits comparison of NOAELs and LOAELs from different studies. In this case (key number 18), rats were exposed to [substance x] via inhalation for 13 weeks, 5 days per week, for 6 hours per day. System This column further defines the systemic effects. These systems include: respiratory, cardiovascular, gastrointestinal, hematological, musculoskeletal, hepatic, renal, and dermal/ocular. "Other" refers to any systemic effect (e.g., a decrease in body weight) not covered in these systems. In the example of key number 18, one systemic effect (respiratory) was investigated in this study. NOAEL A No-Observed-Adverse-Effect Level (NOAEL) is the highest exposure level at which no harmful effects were seen in the organ system studied. Key number 18 reports a NOAEL of 3 ppm for the respiratory system which was used to derive an intermediate exposure, inhalation MRL of 0.005 ppm (see footnote "c"). LOAEL A Lowest-Observed-Adverse-Effect Level (LOAEL) is the lowest exposure level used in the study that caused a harmful health effect. LOAELs have been classified into "Less Serious" and "Serious" effects. These distinctions help readers identify the levels of exposure at which adverse health effects first appear and the gradation of effects with increasing dose. A brief description of the specific end point used to A-3 APPENDIX A quantify the adverse effect accompanies the LOAEL. The "Less Serious" respiratory effect reported in key number 18 (hyperplasia) occurred at a LOAEL of 10 ppm. (10). Reference The complete reference citation is given in Chapter 8 of the profile. (11). CEL A Cancer Effect Level (CEL) is the lowest exposure level associated with the onset of carcinogenesis in experimental or epidemiological studies. CELs are always considered serious effects. The LSE tables and figures do not contain NOAELs for cancer, but the text may report doses vhich did not cause a measurable increase in cancer. (12). Footnotes Explanations of abbreviations or reference notes for data in the LSE tables are found in the footnotes. Footnote "c" indicates the NOAEL of 3 ppm in key number 18 was used to derive an MRL of 0.005 ppm. LEGEND See LSE Figure 2-1 LSE figures graphically illustrate the data presented in the corresponding LSE tables. Figures help the reader quickly compare health effects according to exposure levels for particular exposure duration. (13). Exposure Duration The same exposure periods appear as in the LSE table. In this example, health effects observed within the intermediate and chronic exposure periods are illustrated. (14). Health Effect These are the categories of health effects for which reliable quantitative data exist. The same health effects appear in the LSE table. (15). Levels of Exposure Exposure levels for each health effect in the LSE tables are graphically displayed in the LSE figures. Exposure levels are reported on the log scale "y" axis. Inhalation exposure is reported in mg/m® or ppm and oral exposure is reported in mg/kg/day. (16). NOAEL In this example, 18r NOAEL is the critical end point for which an intermediate inhalation exposure MRL is based. As you can see from the LSE figure key, the open-circle symbol indicates a NOAEL for the test species (rat). The key number 18 corresponds to the entry in the LSE table. The dashed descending arrow indicates the extrapolation from the exposure level of 3 ppm (see entry 18 in the Table) to the MRL of 0.005 ppm (see footnote "b" in the LSE table). (17). CEL Key number 38r is one of three studies for which Cancer Effect Levels (CELs) were derived. The diamond symbol refers to a CEL for the test species (rat). The number 38 corresponds to the entry in the LSE table. (18). (19). A-4 APPENDIX A Estimated Upper-Bound Human Cancer Risk Levels This is the range associated with the upper-bound for lifetime cancer risk of 1 in 10,000 tol in 10,000,000. These risk levels are derived from EPA's Human Health Assessment Group's upper-bound estimates of the slope of the cancer dose response curve at low dose levels (a). Key to LSE Figure The Key explains the abbreviations and symbols used in the figure. . —> TABLE 2-1. Levels of Significant Exposure to [Chemical x] - Inhalation LOAEL (effect) Exposure Key to frequency/ NOAEL Less serious Serious figure? Species duration System (ppm) (ppm) (ppm) Reference [2}— 1nteRMEDIATE EXPOSURE [5] 7 & [¢}— 18 Rat 13 wk Resp 3p 10 (hyperplasia) Nitschke et al. 5d/wk 1981 6hr/d CHRONIC EXPOSURE > Cancer ac) rd ] 2 38 Rat 18 mo 20 (CEL, multiple Wong et al. 1982 © > 5d/wk organ / gans) > 7hr/d 39 Rat 89-104 wk 10 (CEL, lung tumors, NTP 1982 5d/wk nasal tumors) 6hr/d 40 Mouse 79-103 wk 10 (CEL, lung tumors, NTP 1982 5d/wk hemangiosarcomas) 6hr/d 2 The number corresponds to entries in Figure 2-1. [12] ° CEL = cancer effect level; d = day(s); hr = hour(s); LOAEL observed-adverse-effect level; Resp = respiratory; wk = = lowest-obs week(s) Used to derive an intermediate inhalation Minimal Risk Level (MRL) of 5 x 1073 ppm and divided by an uncertainty factor of 100 (10 for extrapolation from animal to h ved-adverse-effect level; mo = ; dose adjusted for intermittent exposure umans, 10 for human variability). month(s); NOAEL = no- [33] _—— + INTERMEDIATE [4] -- JB) (15-384 Days) Systomis so SS CHRONIC (365 Days) ons 18 104 Estimaied Upper - —4H4) 10S Bound Human Cancer Risk 106- 10-7 1000 § 10 f@e @n Buse Qi (Ghee Gen O> an ° Ome Bre Bre Bree Boe wo "ow Or @=0n Ow Ow Om Ow O% On ej —————+ Qw Om 1 , ' ' 01 ' ' ' 001 § ’ ' ooot | < Key t Ra © 10AEL tr seins oftecs jardmals) * 00001 | LI B 1 0AEL tor loss sorts ofiock (ardmaks) 4 Mnimad rioh loved tur » Rata NOAEL jerdmate) § oe ether han concer P0000: § Outneapy @ Cet Concw EReciLovel Sor & Mordey he number nes to seach paint Cor espands ie entries in Table 2 1 FIGURE 2-1. "Doses 1s0resart he wes! Gose lasied por shudy hal reduced & Aemedgenic reapense and @o net ingly The saibterce of a fuesheld le Pe cance end pent Levels of Bignificant Exposure to [Chemical X]-Inhalation V XIAN3ddV 9-V A-7 APPENDIX A Chapter 2 (Section 2.4) Relevance to Public Health The Relevance to Public Health section provides a health effects summary based on evaluations of existing toxicological, epidemiological, and toxicokinetic information. This summary is designed to present interpretive, weight-of-evidence discussions for human health end points by addressing the following questions. 1. What effects are known to occur in humans? 2. What effects observed in animals are likely to be of concern to humans? 3. What exposure conditions are likely to be of concern to humans, especially around hazardous waste sites? The section discusses health effects by end point. Human data are presented first, then animal data. Both are organized by route of exposure (inhalation, oral, and dermal) and by duration (acute, intermediate, and chronic). In vitro data and data from parenteral routes (intramuscular, intravenous, suuc.iLaneous, etc.) are also considered in this section. If data are located in the scientific literature, a table of genotoxicity information is included. The carcinogenic potential of the profiled substance is qualitatively evaluated, when appropriate, using existing toxicokinetic, genotoxic, and carcinogenic data. ATSDR does not currently assess cancer potency or perform cancer risk assessments. MRLs for noncancer end points if derived, and the end points from which they were derived are indicated and discussed in the appropriate section(s). Limitations to existing scientific literature that prevent a satisfactory evaluation of the relevance to public health are identified in the Identification of Data Needs section. Interpretation of Minimal Risk Levels Where sufficient toxicologic information was available, MRLs were derived. MRLs are specific for route (inhalation or oral) and duration (acute, intermediate, or chronic) of exposure. Ideally, MRLs can be derived from all six exposure scenarios (e.g., Inhalation - acute, -intermediate, -chronic; Oral - acute, - intermediate, - chronic). These MRLs are not meant to support regulatory action, but to aquaint health professionals with exposure levels at which adverse health effects are not expected to occur in humans. They should help physicians and public health officials determine the safety of a community living near a substance emission, given the concentration of a contaminant in air or the estimated daily dose received via food or water. MRLs are based largely on toxicological studies in animals and on reports of human occupational exposure. A-8 APPENDIX A MRL users should be familiar with the toxicological information on which the number is based. Section 2.4, "Relevance to Public Health," contains basic information known about the substance. Other sections such as 2.6, "Interactions with Other Chemicals" and 2.7, "Populations that are Unusually Susceptible" provide important supplemental information. MRL users should also understand the MRL derivation methodology. MRLs are derived using a modified version of the risk assessment methodology used by the Environmental Protection Agency (EPA) (Barnes and Dourson, 1988; EPA 1989a) to derive reference doses (RfDs) for lifetime exposure. To derive an MRL, ATSDR generally selects the end point which, in its best judgement, represents the most sensitive human health effect for a given exposure route and duration. ATSDR cannot make this judgement or derive an MRL unless information (quantitative or qualitative) is available for all potential effects (e.g., systemic, neurological, and developmental). In order to compare NOAELs and LOAELs for specific end points, all inhalation exposure levels are adjusted for 24hr exposures and all intermittent exposures for inhalation and oral routes of intermediate and chronic duration are adjusted for continous exposure (i.e., 7 days/week). If the information and reliable quantitative data on the chosen end point are available, ATSDR derives an MRL using the most sensitive species (when information from multiple species is available) with the highest NOAEL that does not exceed any adverse effect levels. The NOAEL is the most suitable end point for deriving an MRL. When a NOAEL is not available, a Less Serious LOAEL can be used to derive an MRL, and an uncertainty factor (UF) of 10 is employed. MRLs are not derived from Serious LOAELs. Additional uncertainty factors of 10 each are used for human variability to protect sensitive subpopulations (people who are most susceptible to the health effects caused by the substance) and for interspecies variability (extrapolation from animals to humans). In deriving an MRL, these individual uncertainty factors are multiplied together. The product is then divided into the adjusted inhalation concentration or oral dosage selected from the study. Uncertainty factors used in developing a substance-specific MRL are provided in the footnotes of the LSE Tables. ACGIH ADME ATSDR BCF BSC CDC CEL CERCLA CFR CLP cm CNS DHEW DHHS DOL ECG EEG EPA EKG FAO FEMA FIFRA fpm ft FR GC HPLC hr IDLH IARC ILO in Kd kg Koc Kow B-1 APPENDIX B ACRONYMS, ABBREVIATIONS, AND SYMBOLS American Conference of Governmental Industrial Hygienists Absorption, Distribution, Metabolism, and Excretion Agency for Toxic Substances and Disease Registry bioconcentration factor Board of Scientific Counselors Centers for Disease Control Cancer Effect Level Comprehensive Environmental Response, Compensation, and Liability Act Code of Federal Regulations Contract Laboratory Program centimeter central nervous system Department of Health, Education, and Welfare Department of Health and Human Services Department of Labor electrocardiogram electroencephalogram Environmental Protection Agency see ECG Food and Agricultural Organization of the United Nations Federal Emergency Management Agency Federal Insecticide, Fungicide, and Rodenticide Act first generation feet per minute foot Federal Register gram gas chromatography high performance liquid chromatography hour Immediately Dangerous to Life and Health International Agency for Research on Cancer International Labor Organization inch adsorption ratio kilogram octanol-soil partition coefficient octanol-water partition coefficient liter liquid chromatography lethal concentration low lethal concentration 50 percent kill lethal dose low lethal dose 50 percent kill lowest-observed-adverse-effect level Levels of Significant Exposure meter mg min mL mm mmo 1 mppcf MRL MS NIEHS NIOSH NIOSHTIC nm ng NHANES nmol NOAEL NOES NOHS NPL NRC NTIS NTP OSHA PEL Pg pmol PHS PMR ppb ppm ppt REL RED RTECS sec SCE SIC SMR STEL STORET TLV TSCA TRI TWA u.s. UF WHO Iv Vv B-2 APPENDIX B milligram minute milliliter millimeters millimole millions of particles per cubic foot Minimal Risk Level mass spectroscopy National Institute of Environmental Health Sciences National Institute for Occupational Safety and Health NIOSH's Computerized Information Retrieval System nanometer nanogram National Health and Nutrition Examination Survey nanomole no-observed-adverse-effect level National Occupational Exposure Survey National Occupational Hazard Survey National Priorities List National Research Council National Technical Information Service National Toxicology Program Occupational Safety and Health Administration permissible exposure limit picogram picomole Public Health Service proportional mortality ratio parts per billion parts per million parts per trillion recommended exposure limit Reference Dose Registry of Toxic Effects of Chemical Substances second sister chromatid exchange Standard Industrial Classification standard mortality ratio short-term exposure limit STORAGE and RETRIEVAL threshold limit value Toxic Substances Control Act Toxic Release Inventory time-weighted average United States uncertainty factor World Health Organization greater than greater than or equal to B-3 APPENDIX B equal to less than less than or equal to percent alpha beta delta gamma micron microgram