In the News
August 27, 2024
As many as 33,000 people across 10 cities die each year from breathing air marked safe by accepted standards in India1. Researchers attribute these fatalities — 7.2% of all deaths annually — to inhaling particulate matter (PM 2.5) at levels far exceeding WHO 24-hour exposure guidelines.
The United Nations agency deems PM 2.5 above 5 microgram per cubic metre as excessive, while Indian air quality standards permit annual average concentrations up to 40 µg per m3.
The highest number of deaths from short-term exposure to pollution were in Delhi and Mumbai. Even cities with moderate to good air quality, such as Chennai, Bengaluru, Hyderabad and Pune, had casualties.
The study authors have called for a revision of India’s current definition of good air quality. “Current standards were set in 2009 before a wealth of evidence was published. Most of the cities we studied would conform to them,” says co-author, Bhargav Krishna at the independent research organisation Sustainable Futures Collaborative.
Because a significant amount of the mortality risk is concentrated at low to moderate levels of exposure, we need to tighten our standards for better public health, says Krishna.
The study looked at PM 2.5 data and daily mortality count across these cities from 2008 to 2019. The researchers employed a hybrid machine learning-based exposure model to predict PM 2.5.
The authors suggest recalibrating the Graded Response Action Plan (GRAP) for Delhi and adjoining regions, an emergency response which kicks in only with severe air quality. It is critical to drive year-round action because even low to moderate air quality — where GRAP does not usually apply — can be harmful, they said.
Each 10 micrograms per cubic metre increase in short-term PM2.5 increased daily deaths by 1.42%. This nearly doubled to 3.57% when the researchers parsed the impact of local sources, especially combustion sources such as vehicles and diesel generators.
Local air pollution especially from dispersed sources such as transport, waste burning, diesel generator sets or other kinds of combustion have a role in these short-term exposure-linked mortalities, says Krishna, emphasising a change in metrics to focus on local combustion sources.
This would mean prioritising mitigation of these sources. Current policies focus on construction dust and road dust, but these sources require attention, he added.
According to data from the Air Quality Life Index 2021, average life expectancy in India go up five years if levels of toxic particles were brought down to meet WHO specifications.
However, this may be ambitious, says Tanushree Ganguly, Director of the Air Quality Life Index at the Energy Policy Institute of the University of Chicago in Delhi. “It can only happen if we periodically review standards and weigh emerging evidence on the impacts of air pollution on health,” she says.