Air Pollution Deaths Haunt Even 'Clean' Cities Like Shimla, Says Lancet

There has been an increase in air pollution-related deaths in Indian cities that are deemed cleaner in terms of air quality against highly polluted mega cities like Delhi, according to a new study published in The Lancet Planetary Health journal.

In a stark revelation highlighting the deadly consequences of air pollution, the study, conducted across 10 major Indian cities, has underscored the severe health risks associated with even moderate levels of air pollution. Spanning from 2008 to 2019, it sheds light on how seemingly 'good' air quality can still be lethal, affecting millions.

“The significant effects we are observing even below the Indian air quality limits are alarming, suggesting that perhaps we have set our standards higher than they should be," said Bhargav Krishna, fellow at the Sustainable Futures Collaborative and the study’s lead author.

The study examined daily mortality rates alongside PM2.5 exposure levels in cities including Delhi, Mumbai, Chennai, and Kolkata. PM2.5 refers to fine particulate matter, less than 2.5 micrometers in diameter, which can penetrate deep into the lungs and enter the bloodstream, causing serious health complications. The study found that an exposure of just 48 hours to high levels of the particles could decrease life expectancy at a collective level.

Despite periodic improvements in air quality measures, the study found that air pollution levels often surpassed both Indian and World Health Organization guidelines, contributing to a staggering annual death toll of approximately 33,627 across the 10 cities. Delhi, notorious for its air pollution spikes, registered the highest attributable deaths due to PM2.5 exposure, reflecting 11,964 fatalities annually.

"Our findings debunk the notion that cities with 'acceptable' air quality are safe. Even when air quality is within permissible limits by local standards, the health impact remains profound," said Dr. Anjali Sharma, lead researcher of the study.

The study employed rigorous analytical methods, including quasi-Poisson generalised additive models and instrumental variable analysis to discern the impact of locally generated pollutants. This approach revealed a 1.42% increase in daily mortality per 10 μg/m3 increase in PM2.5, affirming a direct correlation between air pollution levels and death rates.

"We observed a supralinear relationship, where lower levels of exposure to PM2.5 posed higher relative risks of mortality. This indicates that there is no safe threshold for air pollution exposure, even at concentrations below current guidelines," Sharma said.

The research also highlighted significant heterogeneity in mortality risks across different cities, suggesting varying susceptibilities and pollutant profiles unique to each urban area. For instance, while Shimla and Bangalore exhibited relatively lower pollution levels, they showed sharper mortality increases per unit of PM2.5, compared to more polluted cities like Delhi and Kolkata.

"The data unequivocally calls for stricter air quality regulations and aggressive enforcement mechanisms," said Rajesh Kumar, a public health policy analyst. "It is imperative to prioritise public health over economic interests to mitigate this silent health crisis."