The increasing reliance on fossil fuels globally has severely affected human health|Photo: Healthline

Exposure to PM2.5 generated by fossil-fuel alone costs India 2.46 million lives: Harvard study

One in five deaths around the world in 2018 was attributable to exposure to toxic air from burning fossil fuels, the study finds 

More than 8 million people are killed in 2018 because of air pollution caused by the burning of fossil fuels alone which is equivalent to one in five deaths worldwide, a new study estimates. The study is important because while the Global Burden of Disease (GBD) – the largest and most comprehensive study on the causes of global mortality – focuses on the health impacts of total PM2.5, this study focuses only on the health impacts of fossil-fuel derived PM2.5. 

The study titled ‘Global Mortality from Outdoor Fine Particle Pollution Generated by Fossil Fuel Combustion: Results from GEOS-Chem’ was conducted by Harvard University in collaboration with the University of Birmingham, the University of Leicester and University College London.

China has the greatest premature mortality

According to the study, China reported the greatest number of premature deaths (3.91 million) in 2012. This was the year in which fossil fuel emissions peaked in China and was followed by a dramatic reduction in fossil fuel emissions because of strict mitigation measures. 

The study noted that mitigation measures led to 30%-50% decline in annual mean PM2.5 across China from 2013-18. If the decline is taken into consideration, the number of premature mortality deaths in China decreased from 3.91 million to 2.36 million, bringing the global rate down from 10.2 million to 8.7 million per year. 

The India story

In India, the study found 2.46 million premature deaths in 2012 – the second highest after China – attributable to long-term exposure to PM2.5 generated by fossil-fuel alone. 

It also pointed out that although India has imposed control on pollution sources since 2012, there is no evidence of air quality improvements in heavily populated cities like Delhi.

While Uttar Pradesh reported the maximum number of premature deaths (0.47 million) in 2012, followed by Bihar, West Bengal, Maharashtra and Madhya Pradesh, Sikkim reported the least (359). 

Continent wise, in 2012, Asia reported the greatest number of premature deaths (7.91 million) followed by Europe, Africa, South America and North America, the study found.

Why was data from 2012 used? 

The study points out that globally, exposure to PM2.5 from fossil fuel emissions accounted for 21.5% (10.2 million) of total deaths in 2012. The study used air pollution data from that year because El Niño was in a neutral phase at that time. 

El Niño- an abnormal weather pattern caused by the warming of the Pacific Ocean near the equator, off the coast of South America, affects air pollution levels, which would have affected the data required for the study. Therefore, using a neutral El Niño year allowed researchers to increase the readability of the air pollution data. 

Impact on children

The study also estimated mortality because of lower respiratory infections (LRI) such as pneumonia and bronchitis amongst children under the age of five in America and Europe where the level of annual PM2.5 concentration is below 25 μg/m3

North and Central America had an estimated 876 excess deaths due to LRI followed by South America (747) and Europe (605), the study found.

Excess death is the difference between the observed number of deaths in specific time periods and expected number of deaths in the same time periods.

The developing fetus and children younger than five years of age are more biologically and neurologically susceptible to adverse effects of air pollutants from fossil combustion than adults. According to WHO estimates, in 2012, 0.16 million global deaths among children under the age of five were attributable to ambient air pollution.

Is GBD underestimating deaths?

According to the recent GBD study, the total number of global deaths from all outdoor airborne particulate matter stands at 4.2 million, whereas in this study, the number of deaths due to fossil fuels alone stands at 8.7 million. This difference is attributable to different approaches taken by the two studies.

While GBD relies on satellite and surface observations to estimate the average global annual concentrations of airborne PM2.5, the current study used GEOS-Chem.

What is from GEOS-Chem?

GEOS-Chem, a chemical transport model, is used by the researchers to quantify the global mortality attributable to PM2.5 air pollution from fossil fuel combustion. It is a global 3-D model of atmospheric chemistry driven by meteorological input from the Goddard Earth Observing System (GEOS) of NASA. It is applied by researchers around the world to a wide range of atmospheric composition problems. 

“With satellite data, you’re seeing only pieces of the puzzle,” says 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. “It is challenging for satellites to distinguish between types of particles, and there can be gaps in the data.” 

The way forward

The increasing reliance on fossil fuels globally has severely affected human health. The study proves that the fossil fuel component of PM2.5 contributes to a large global mortality burden. 

It suggested that the health impacts of a category of PM2.5 can be more readily controlled than other sources and precursors of PM2.5 such as dust or wildfire smoke. The study concluded that the findings should encourage policymakers and stakeholders to further invest in clean sources of energy.

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