key: cord-0887179-c74anzbk
authors: Das, Darpan; Ramachandran, Gurumurthy
title: Risk Analysis of Different Transport Vehicles in India During COVID-19 Pandemic
date: 2021-05-11
journal: Environ Res
DOI: 10.1016/j.envres.2021.111268
sha: 513e173272fc6dce422c23e97d45847687ff54ca
doc_id: 887179
cord_uid: c74anzbk

Due to the airborne nature of viral particles, adequate ventilation has been identified as one suitable mitigation strategy for reducing their transmission. While ‘dilution of air by opening the window’ has been prescribed by national and international health agencies, unintended detrimental consequences might result in many developing countries with high ambient air pollution. In the present study, PM(2.5) exposure concentration and probability of mortality due to PM(2.5) in different scenarios were assessed. A COVID airborne infection risk estimator was used to estimate the probability of infection by aerosol transmission in various commuter micro-environments: (a) air conditioned (AC) taxi (b) non-AC taxi (c) bus and (d) autorickshaw. The following were the estimated exposure concentrations in the four types of vehicles during pre-lockdown, during lockdown, and lost-lockdown: AC taxi cars (17.16 μg/m(3), 4.52 μg/m(3), and 25.09 μg/m(3)); non-AC taxis: (28.74 μg/m(3), 7.56 μg/m(3), 42.01 μg/m(3)); buses (21.79 μg/m(3), 5.73 μg/m(3), 31.86 μg/m(3)) autorickshaws (51.30 μg/m(3), 3.50 μg/m(3), 75 μg/m(3)). Post-lockdown, the probability of mortality due to PM(2.5) was highest for autorickshaws (5.67 x 10(-3)), followed by non-AC taxis (2.07 x 10(-3)), buses (1.39 x 10(-3)), and AC taxis (1.02 x 10(-3)). This order of risk is inverted for the probability of infection by SARS-COV-2, with the highest for AC taxis (6.10 x 10(-2)), followed by non-AC taxis (1.71 x 10(-2)), buses (1.42 x 10(-2)), and the lowest risk in autorickshaws (1.99 x 10(-4)). The findings of the present study suggest that vehicles with higher ventilation or air changes per hour (ACH) should be preferred over other modes of transport during COVID-19 pandemic.

ventilation or air changes per hour (ACH) should be preferred over other modes of transport during COVID-19 pandemic.

The World Health Organization (WHO) has declared the COVID-19 pandemic to be an airborne infectious disease (1) . The general consensus is that there are two main modes of transmission of the virus: (a) via larger respiratory droplets (>5 µm) that remain in the air for only a short time and travel short horizontal distances, generally a few meters, before settling out by gravity and (b) via small (<5 µm) aerosolized droplets that remain in the air for many hours or days and travel longer distances (2) . While exposure to droplets can be mitigated by face masks and social distancing, exposures to smaller airborne particle need to be managed using engineering controls such as adequate ventilation. Several studies indicate that inadequate ventilation is an important mechanism for the spread of COVID virus (2) (3) (4) (5) . Ventilation as a strategy to dilute the air concentration of airborne contaminants (including virus containing particles) by exchanging air in the room with air from outside is widely accepted including for transport vehicles (URL 01).

The USEPA and Centers for Disease Control (CDC) recommendations include "Improve the ventilation in the vehicle if possible (for example, open the windows or set the air ventilation/air conditioning on non-recirculation mode" and "Ask the driver to improve the ventilation in the vehicle ) (URL 02, URL 03).

However, in many developing countries, diluting the indoor with ambient air increases risks to health from exposure to air pollution. PM 2.5 (particulate matter less than 2.5 m in aerodynamic diameter) concentrations in India are an order of magnitude higher than cities in USA (6) .

Approximately 58% of districts in India recorded ambient particulate matter PM 2.5 (particulates with aerodynamic diameter ≤ 2.5 m) pollution above the National Ambient Air Quality Standard (NAAQS) and 99% of the districts were above the WHO guidelines in 2015 (7).

Estimates of the burden in India show that 627,000 premature deaths and nearly 17.8 million Disability Adjusted Life Years (DALYs) to be attributable to ambient air pollution (8) .

Autorickshaws and buses are other commonly used means of public transport in most of the cities in India (9), along with personal cars and shared cars/ taxis (10) . Exposure to traffic-related PM during short-term commutes has demonstrable health effects (11) , and there is evidence that the in-cabin air can be polluted by the outdoor ambient air in India (URL 04). Piscitelli et al., (12) in their study in Italy, estimated the health care cost due to road freight traffic related air pollution to be up to 1.2 billion EUR per year. A recent study shows that irrespective of the city and car model used, a windows-open setting showed the highest exposure, followed by fan-on and recirculation , and also that particulate matter (PM) was higher for shared cars compared to personal cars (13, 14) . While many cities in the developing countries like Delhi (15, 16) suffer from poor air quality with PM 2.5 concentrations above WHO guidelines, ambient air pollution has been shown to decrease globally during the pandemic (17) . As lockdowns are removed in many parts of the word, PM 2.5 concentrations are expected to soon reach pre-lockdown levels. There is a considerable percentage of passengers in India who use autorickshaws and motorcycles who will be exposed to the ambient PM 2.5 concentrations. High PM 2.5 exposure in auto-rickshaws have been described in several studies (18) (19) (20) .

With the ongoing pandemic and guidelines suggested by the regulatory bodies to open window during travel, population living in low/ income countries are exposed to the ambient PM 2.5 concentration. In the present study, short-term health risks (due to virus infection) and long-term or chronic risks (due to particulate matter) were assessed for several commute microenvironments. Short term or acute health risk refers to health outcomes resulting from exposures J o u r n a l P r e -p r o o f within a short period. Long term health risks are attributable to chronic exposure (PM 2.5 ) over a long time period that result in adverse health outcomes. The risk tradeoffs in different scenarios of pre-lockdown, lockdown and post-lockdown were assessed to estimate the risk associated with different mode of transportation. The probability of infection is assumed to be related to the number of quanta (airborne virus)

inhaled. The average concentration of quanta in a compartment (C avg in q/m 3 ) can be estimated as:

where E is the quanta emission rate (q/hour), L is the sum of removal rates by all mechanisms (hour -1 ), e.g., gravitational settling, and removal by ventilation and filtration systems, D is the duration of the ride, and V is the volume of the vehicle interior.

The probability of infection (P i ) is modeled as:

J o u r n a l P r e -p r o o f

where n is the number of inhaled quanta. The assumptions given as input to the model are shown

in Table 1 , with many of the values relating to virus properties obtained from Miller et al. (24) .

The dimensions of a typical Indian AC-taxi and non AC-taxi were taken from Adak et al., (25) ; J o u r n a l P r e -p r o o f boosting SARS-COV2 inter-personal transmission (32, 33) . The present study assesses the longterm health effects of the particulate matter. However, apart from particulate matter, traffic related pollutants include carbon monoxide, volatile organic compounds, nitrogen dioxide and poly-aromatic hydrocarbons (34) . There is limited epidemiological evidence regarding the synergistic effects of traffic related pollutants (35) . It is very likely that traffic related pollutants will increase the absolute risk values due to their synergistic effects but the risks will still be an order of magnitude lower than the short-term effects of the SARS-CoV-2 virus. Thus, synergisms between the components of the air pollution mixture, although not included in the present study, will not qualitatively alter the findings of the study.

There are two key mitigation strategies for countering virus-laden aerosols in transit vehicles: we J o u r n a l P r e -p r o o f

The findings of the present study indicate that the risk ranking of commute micro-environments is altered in different stages of the lockdown (Figure 3 ). The risk calculations clearly indicate that while the AC-taxi option is most preferable during normal periods to mitigate air pollution (in middle-and low-income countries with poor air quality), this may not be a viable option 

It is Time to Address Airborne Transmission of COVID-19

COVID-19 Outbreak Associated with Air Conditioning in Restaurant

Viable SARS-CoV-2 in the air of a hospital room with COVID-19 patients

Evidence for probable aerosol transmission of SARS-CoV-2 in a poorly ventilated restaurant

Makeshift hospitals for COVID-19 patients: where health-care workers and patients need sufficient ventilation for more protection

Evaluation of emissions and air quality in megacities

The Contribution of Household Fuels to Ambient Air Pollution in India: A Comparison of Recent Estimates. Collab Clean Air Policy Centre

Addressing the burden of disease attributable to air pollution in India: The need to integrate across household and ambient air pollution exposures

Urban real-world driving traffic emissions during interruption and congestion

How Urban India Moves

A review of commuter exposure to ultrafine particles and its health effects

Air pollution and estimated health costs related to road transportations of goods in Italy: A first healthcare burden assessment

In-car particulate matter exposure across ten global cities

Exposure to in-vehicle respirable particulate matter in passenger vehicles under different ventilation conditions and seasons

Effect of lockdown amid COVID-19 pandemic on air quality of the megacity Delhi

Impact of lockdown measures during COVID-19 on air quality-A case study of India

COVID-19 lockdowns cause global air pollution declines with implications for public health risk

exposure in highly polluted cities: A case study from

Concentrations of fine, ultrafine, and black carbon particles in auto-rickshaws

Exposure to traffic-related particulate matter and deposition dose to auto rickshaw driver in Dhanbad

Estimating the National Public Health Burden Associated with Exposure to Ambient PM 2.5 and Ozone

Extended follow-up and spatial analysis of the American Cancer Society study linking particulate air pollution and mortality

Analysis of various transport modes to evaluate personal exposure to PM 2 . 5 pollution in Delhi

Transmission of SARS-CoV-2 by inhalation of respiratory aerosol in the Skagit Valley Chorale superspreading event

Development of emission factors for motorcycles and shared auto-rickshaws using real-world driving cycle for a typical Indian city

The influence of school bus ventilation scenarios over incabin PM number concentration and air exchange rates

Usage pattern development for three-wheel auto rickshaw taxis in India. VPPC 2007 -Proc

Field study of air change and flow rate in six automobiles

Air change rates of motor vehicles and in-vehicle pollutant concentrations from secondhand smoke

The dramatic impact of coronavirus outbreak on air quality: Has it saved as much as it has killed so far?

Exposure to air pollution and COVID-19 mortality in the United States: A nationwide cross-sectional study

SARS-Cov-2RNA found on particulate matter of Bergamo in Northern Italy: First evidence

Potential role of particulate matter in the spreading of COVID-19 in Northern Italy: First observational study based on initial epidemic diffusion

A review of traffic-related air pollution exposure assessment studies in the developing world

Is there evidence for synergy among Air pollutants in causing health effects? Environ Health Perspect

Effect of cabin ventilation rate on ultrafine particle exposure inside automobiles

Invehicle particle air pollution and its mitigation

The role of air conditioning in the diffusion of Sars-CoV-2 in indoor environments: A first computational fluid dynamic model, based on investigations performed at the Vatican State Children's hospital

The authors declare no conflict of interest

No financial assistance was received in support of the study.

None