A recently published paper in the journal Nature Communications, by an interdisciplinary group of researchers from across the globe has comprehensively examined the sources and health effects of air pollution — not just on a global scale, but also individually for more than 200 countries and sub-national regions.
The study claims that globally, 1.05 million deaths were avoidable in 2017 by eliminating fossil-fuel combustion, with coal contributing to over half. Other dominant global sources included residential (0.74 million deaths; 19.2% of PM2.5 burden), industrial (0.45 million deaths; 11.7% PM2.5 burden), and energy (0.39 million deaths; 10.2% of PM2.5 burden) sectors. With 58% of total global ambient PM2.5 mortality burden, China and India together accounted for the largest numbers of attributable deaths.
Dr Michael Brauer, lead researcher on the study and professor at University of British Columbia’s School of Population and Public Health said, “We’ve known for a while that air pollution is a big contributor to deaths. This study provides both a global perspective of the relative importance of different sources and a starting point for the many countries of the world who have yet to address air pollution as a health concern.”
As per the study, in 2017, the global PM2.5 average concentration was 41.7 μg/m3, with 91% of the world’s population experiencing annual average concentrations higher than the World Health Organization (WHO) annual average guideline of 10 μg/m3. It further adds that more than 65% of the sub-national regions evaluated experienced higher PM2.5 concentrations than their national averages. In some extreme cases in regions around Kanpur and Singrauli, the annual average PM2.5 concentrations exceeded 150 μg/m3, almost four times the safety limit prescribed by the Central Pollution Control Board and 15 times higher than the WHO guideline.
For the top 9 countries that had the highest numbers of attributable deaths, coal was the largest contributing fuel in China, accounting for 22.7% or 315,000 deaths. Oil & natural gas was the largest fuel contributor in Egypt, Russia, and the United States accounting for up to 27% or between 9000 and 13,000 deaths in each country, and solid biofuel combustion was the largest contributing fuel source in India, Indonesia, Bangladesh, Pakistan and Nigeria accounting for up to 36% or 250,000 deaths. Among key polluting sources in India, the residential sector made up 25.7%, source contribution, industry 14.8%, energy 12.5%, agriculture 9.4%, waste 4.2% and other combustion 3.1%.
The study also establishes that sources vary at the sub-national scale, highlighting the importance of developing regional air quality mitigation strategies. For example, while residential emissions are the largest source of average PM2.5 exposure and attributable mortality in China and India, areas surrounding Beijing and Singrauli (Madhya Pradesh, India) have relatively larger contributions from the energy and industry sectors. As the largest number of PM2.5 attributable deaths occurred in China and India, complete elimination of coal and oil & natural gas combustion in these two countries could reduce the global PM2.5 disease burden by nearly 20%. Previous research has shown that emissions from coal combustion have decreased by up to 60% between 2013 and 2017 in China, while these same emission sources in India have increased by up to 7% between 2015 and 2017.
Dr Erin McDuffie, the first author of the study and a visiting research associate at Washington University in St. Louis, explained that countries with the largest number of air pollution-related deaths typically had larger contributions from human-derived sources, “How many deaths are attributable to exposure to air pollution from specific sources? The comparisons in this study are important when it comes to considering mitigation. Ultimately, it will be important to consider sources at the sub-national scale when developing mitigation strategies for reducing air pollution.”
Long-term exposure to air pollution in the form of fine particulate matter contributes to an average of 4 million deaths per year worldwide, including deaths from heart disease, lung cancer, chronic lung disease, strokes, respiratory infections, and Type 2 diabetes. The large dataset in this study is the first to estimate global contributions from more than 20 individual pollution sources—from sectors such as agriculture, transportation, energy generation, waste, and residential energy use. It is also the first to study the global impacts of specific fuels like solid biomass, coal, oil and natural gas.
Dr. Seema Javed is an Environmentalist, Independent Journalist & Strategic Communicator for Climate Change