Nearly 3,000 deaths in Chennai per year due to short-term air pollution exposure, finds study

CHENNAI: A new study published in the Lancet Planetary Health journal has found that air pollution has caused around 2,900 deaths annually in Chennai between 2008 and 2019, despite the city's levels being lesser than the country's current standards.

Around 4.9 per cent of all deaths reported in Chennai during that period were attributed to short-term PM2.5 (Particulate Matter) exposure, which is higher than the World Health Organization (WHO) given guideline value of 15 micrograms per cubic meter.

Each 10 micrograms per cubic meter increase in short-term PM2.5 exposure was associated with a 0.97 per cent increase in daily deaths.

The study was conducted in 10 Indian cities --- Chennai, Hyderabad, Bengaluru, Delhi, Mumbai, Shimla, Kolkata, Varanasi, Ahmedabad, and Pune.

A significant number of deaths were observed even in cities which are not considered to have high air pollution levels, such as Mumbai, Bengaluru, Kolkata, and Chennai.

The researchers said that 7.2 per cent of all deaths (approximately 33,000 each year) reported from across the 10 cities during the study period could be linked to short-term PM2.5 exposure higher than the WHO's guideline value of 15 microgram per cubic meter. Each 10 micrograms per cubic meter increase in short-term PM2.5 exposure was associated with a 1.42 per cent increase in daily deaths.

This estimate nearly doubled to 3.57 per cent when the team used a causal modelling approach that isolates the impact of local sources of air pollution.

Air pollution policy currently focuses on 'non-attainment cities' which fail to meet the current Indian standards. But since the standards are 4 times above the current WHO guideline value of 15 micrograms per cubic meter, people in many more regions beyond these 10 cities are also vulnerable, the study reminded.

Reccommending to expand remedial action beyond the current 'non-attainment cities', the team asked to improve focus on action throughout the year and not just during seasonal extremes.

A large proportion of mortality risk is concentrated at low to moderate PM2.5 levels with risk tapering off at higher levels, it observed.

The study also suggested developing policy instruments to better address dispersed local sources of air pollution.

Meanwhile, Dr Bhargav Krishna, Fellow at the Sustainable Futures Collaborative and a lead author on the study said, "The significant effects observed below the current Indian standards have implications for what we consider acceptable air quality, and emphasise the need for stringent year-round action across the whole country".

Among the 10 cities surveyed during 2008-2019, Delhi has the highest mortality due to short-term PM2.5 exposure with 11.5 per cent of all deaths, which is around 12,000 deaths every year. Meanwhile, Varanasi reported 10.2 per cent deaths due to PM2.5 exposure.