The unrelenting rise in vehicular and industrial emissions has turned India's bustling urban centers like Delhi and Bengaluru into veritable hotbeds of air pollution with daily mortality rates soaring-on average 7.2%-due to PM2.5 levels exceeding WHO-recommended safe thresholds.
This lethal phenomenon underscores the urgent need for robust environmental policies and collective action to mitigate the profound impact of air pollution on public health, as highlighted in a first multi-city study to examine the association between short-term exposures to air pollution and daily mortality in India. The study is published in The Lancet Planetary Health journal on Thursday.
Particulate matter (PM) consists of a mixture of solids and liquid droplets and can either be emitted directly or form when pollutants from various sources react in the atmosphere. PMs less than 10 micrometers in diameter pose the greatest problems, because they can get deep into the lungs, and some may even get into the bloodstream.
Researchers of the study "the first multi-city, time series analysis of short-term exposure to PM2.5 and daily mortality in India," said that daily exposure to PM2.5 pollution in Indian cities is linked with a higher risk of death, and locally created pollution could be possibly causing these deaths.
The international team included researchers from Varanasi's Banaras Hindu University (BHU) and the Centre for Chronic Disease Control, New Delhi.
They found that an increase of 10 micrograms per cubic metre in the average of fine particulate matter (PM2.5) pollution measured over two days (short-term exposure) was related to 1.4 per cent higher daily mortality.
The death risk was found to be doubled (2.7 per cent) per a 10 microgram per cubic metre increase, when the researchers restricted their analysis to observations below Indian standards of air quality, less stringent than WHO guidelines for safe exposure, which prescribe 15 micrograms per cubic metre of PM2.5 over a 24-hour period, said the study.
Indian air quality standards prescribe 60 micrograms per cubic metre of PM2.5 over a 24-hour period. City-wise, the authors found a 0.31 per cent rise in daily mortality per a 10 micrograms per cubic metre increase in PM2.5 in Delhi, while in Bengaluru, the rise was 3.06 per cent.
The links between daily exposure to PM2.5 pollution and locally created pollutants were found to be stronger in models which the researchers used to explore cause-and-effect relationships.
Therefore, it was possible that the locally generated pollutants were causing these excess deaths, the authors said. "The causal effects were especially strong in cities with lower concentrations of air pollution, such as (Bengaluru), Chennai, and Shimla," the authors wrote.