Concerned about the gallons of pollution you’ll be swallowing this pollution season? Multiple estimates in the past suggested that the severe air pollution over the Indo-Gangetic Plains (IGP), including the Delhi-NCR, causes millions of premature deaths every year. This led many families to relocate to less-polluted regions while the remaining residents spent winter days under the constant anxiety of how their life might be cut short due to the choking, toxic air.
Now, a new study says we might not have to be as paranoid as we are about the death risks associated with air pollution in India!
Deadly, tiny particles of horror
India is notorious for being one of the worst pollution hotspots in the world. The winter inversion and the geography of the IGP trap most pollution particles near the surface. Add to that post-monsoon stubble burning, industrial and vehicular emissions, thermal power plants, and festival emissions, and it seems like a no-brainer that respiratory diseases are one of the leading causes of death in the country.
The ball is driven right out of the park when we compare PM2.5 levels — tiny particles of less than 2.5 micrometres — that form a significant component of the harmful stuff in the air. Many reports have shown that almost everyone in the country breathes exorbitant amounts of the matter than is considered safe by multiple health organisations, including the World Health Organisation (WHO). Estimates from studies in reputed journals like The Lancet also attributed up to 23.5 lakh premature deaths per year to air pollution.
But here’s the catch — most research linking PM2.5 levels to mortality risk due to respiratory and cardiovascular diseases are derived from models, not practical, real-life data. Furthermore, these models are based on high-income countries that are vastly different from ours in terms of disease patterns.
“Most existing studies on air quality and health are done in high-income countries, where PM2.5 exposures are far lower, and disease patterns are substantially different than in low and middle-income countries such as India,” explains co-author George D’Souza, dean of St. John’s Medical College in Bengaluru, India. “That needs to change.”
Million Death Study shows unusual results
When scientists processed input from the Million Death Study — one of the world’s most extensive studies of premature mortality using real-world historical data — they found that we might have been jumping to alarming conclusions a little too soon.
After analysing over 2 lakh deaths aged 15-69, they found no direct correlation between excess risk between PM2.5 concentrations and respiratory or heart disease (excluding stroke). These results were similar over different age groups, as well as areas that might have high usage of solid household fuel (which is a significant contributor to PM2.5).
The study calculated relative risks (RRs) by linking satellite-based estimated PM2.5 exposure over specific time periods to deaths 3 to 5 years later in over 7,400 small villages or urban blocks covering a total population of 6.8 million. Based on the results, the authors of the study recommend suitable caution in estimating deaths from PM2.5 exposure and even more caution in extrapolating model-based associations of risk derived mostly from high-income countries to India.
Health risks remain high
However, there was a 9% increase in stroke deaths for every ten micrograms increase in PM2.5 exposure in a cubic metre space. So, this doesn’t put us in the clear to start burning woodstoves indoors, especially since we’ve recently found traces of soot in developing foetus brains and lungs.
While this might help many of us breathe a little easier (literally, if Diwali goes well this year), there are still many reasons we cannot ignore the tragic pollution levels in India, especially in the metro and northern cities.
“PM2.5 may not be the big killer in India as has been touted, but action to reduce PM2.5 exposure is still necessary,” says Jha, a physician at St. Michael’s Hospital. “Air pollution worsens child lung health and lowers the quality of life, and that is sufficient justification to act.”
The results of this research were published in Environmental Health Perspectives last month and can be accessed here.
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