At least 30.7% of deaths in India can be attributed to air pollution from fossil fuels--that means about 2.5 million people die every year after breathing toxic air. Scientists from Harvard University, University College London and other institutions published a new study on Tuesday, which indicates that deaths from air pollution could be nearly double that of previous estimates.
The study, published in the journal Environmental Research on 9 February, says that more than 8 million people died in 2018 from air pollution from burning fossil fuels like coal, diesel and petrol. It finds that air pollution resulting from fossil fuel use is responsible for 1 in 5 deaths worldwide.
This is an increase over previous estimates. The most recent Global Burden of Disease study from 2015, the largest and most comprehensive study on the causes of global mortality, put the number of global deaths from all outdoor airborne particulate matter — including dust and smoke from wildfires and agricultural burning — at 4.2 million.
In this new study, the researchers found the highest rates of deaths from fossil fuels in China and India. In China, premature mortality due to fossil fuel burning and the resultant toxic air stands at 3.91 million. In India, the number of deaths is 2.46 million a year.
A breakdown of state-wise data from India shows that Uttar Pradesh (471,546 deaths) and Bihar (288,821 deaths) were the most severely affected in terms of excess deaths resulting from fossil fuel pollution among those aged 14 years and above.
"An increase in the concentration of non-fossil-fuel PM2.5 would decrease our estimate of the number of premature deaths due to fossil fuel PM2.5 in India and China," the report observes. In other words, a switch to cleaner and renewable fuels would help reduce the number of premature deaths due to burning of coal, petroleum and other fossil fuels.
Until recently, it was difficult to estimate how much fine particulate matter pollution is caused by directly by fossil fuel use, and by extension, deaths specifically from fossil fuel pollution. Previous research used satellite and surface observations to estimate the average global annual concentrations of airborne particulate matter, or PM 2.5. These can’t differentiate between particles from fossil fuel emissions and those from dust, wildfire smoke or other sources. Advances in research and modelling now allow scientists to pinpoint the contribution of fossil fuel burning.
“With satellite data, you’re seeing only pieces of the puzzle,” Loretta J. Mickley, senior research fellow in Chemistry-Climate Interactions at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and co-author of the study says. “It is challenging for satellites to distinguish between types of particles, and there can be gaps in the data.”
To overcome this, the Harvard researchers turned to GEOS-Chem, a three-dimensional model of atmospheric chemistry. Previous studies have used GEOS-Chem to model the health impacts of particulate matter, and its results have been validated against surface, aircraft, and space-based observations around the world.
To model PM 2.5 generated by fossil fuel combustion, the researchers used estimates of emissions from multiple sectors, including power, industries, shipping, aircraft and ground transportation. The scientists used pollution data from 2012 in the GEOS-Chem model to arrive at the final estimate of 8.7 million deaths in 2018. According to the paper, all simulations were set up to replicate 2012 pollution conditions
But why use data from 2012? Global meteorological conditions can affect estimates of air pollution - in particular the El Niño weather pattern, which can worsen or improve air pollution. The study uses air pollution data from 2012 since El Niño was in a neutral phase, meaning it did not affect air pollution levels, at the time. If it had used data from another year, the estimates of air pollution mortality might have been higher or lower because of El Niño.