Mumbai: Long-term exposure to air pollution may have significantly increased the spread and severity of Covid-19 in districts such as Mumbai, according to a nationwide study that found higher levels of PM2. 5 and nitrogen dioxide (NO2) were consistently associated with higher infection and death rates.
Published in the peer-reviewed journal Applied Spatial Analysis and Policy, researchers from the International Institute for Population Sciences (IIPS), Deonar, analysed data from 640 districts across India between April 2020 and Nov 2022. Globally, Covid-19 infected about 770 million people and claimed nearly 70 lakh lives, while India reported around 4.5 crore confirmed cases and over 5.3 lakh deaths till Dec 2024.
The IIPS team gathered district-level Covid-19 data, along with long-term measures of air pollution, temperature, rainfall and vegetation while accounting for demographic, socioeconomic and health factors. Districts with the highest Covid-19 case burden were concentrated in Maharashtra, Kerala, Karnataka and Andhra Pradesh, said lead author Dr Suryakant Yadav.
Districts adjoining major cities such as Delhi, Kolkata, Chennai, Bengaluru and Ahmedabad also recorded moderate to high numbers of Covid-19 cases and deaths. “In contrast, districts in Bihar, Uttar Pradesh, Madhya Pradesh and Rajasthan reported relatively fewer infections and deaths,” said the study. Maharashtra’s districts, along with those in Delhi, Punjab and Haryana, were among the worst affected in terms of Covid-19 mortality.
Dr Yadav said the study fills an important gap in Indian research. “While similar studies examining the link between PM2. 5 and Covid incidence and severity have been conducted in other countries, this is the first such study from India,” he said. His team triangulated satellite-derived pollution data with district-wise Covid-19 infections and deaths to conclude that “while air pollutants worsened the risk of Covid, greenery reduced the risk”.
Referring to Mumbai, he said, “”Mumbai witnessed one of the highest incidence rates in the country. It has lower green cover than many other places and higher PM2. 5 and nitrogen oxide concentrations. This affected mortality in Mumbai.”
It’s well-known that long-term exposure to air pollution could impair lung function, increase inflammation and make people more vulnerable to severe respiratory infections. Green spaces, meanwhile, can improve air quality, reduce urban heat and promote better overall health, potentially lowering the risk of severe disease.
The findings are particularly relevant for Mumbai and other industrialised districts of Maharashtra, which were among the country’s worst-hit regions during successive Covid-19 waves. Researchers found that districts with higher PM2. 5 and NO2 levels generally experienced worse Covid-19 outcomes, while districts with greater vegetation cover had lower case fatality rates. Environmental greenness, measured using the normalised difference vegetation index (NDVI), appeared to offer a protective effect against Covid-19 deaths, said the study’s data.
The study found that the relationship between environmental factors and Covid-19 was not uniform across India, with the impact of pollution and greenness varying considerably between districts. The authors emphasised that the study establishes associations rather than causation, as individual factors such as vaccination, healthcare access, testing rates and personal behaviour could not be accounted for. However, they said the findings underscore the importance of cleaner air and greater urban green cover in strengthening preparedness for future respiratory pandemics.
