Pollution from burning coal, oil and gas kills millions each year. The toll is heaviest in China and India

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BURNING FOSSIL fuels does more than pump carbon into the atmosphere. As with all sources of air pollution, it releases a mix of gases and tiny particulate matter. The smallest class of these—known as PM2.5—can settle in people’s lungs and enter the bloodstream, where they can cause or exacerbate illnesses and, sometimes, lead to death.

The death toll is enormous, according to a new paper by researchers at Harvard University in America, and University College London (UCL) and the University of Birmingham in Britain. Their study, published in Environmental Research, estimates that in 2018, 8.7m global deaths were associated with breathing air pollution from fossil fuels, almost one-fifth of all deaths worldwide. That total is far higher than previous estimates. The Global Burden of Disease (GBD), a study by the Institute for Health Metrics and Evaluation (IHME) that tallies the lives lost to hundreds of illnesses and injuries, puts deaths from air pollution at 4.2m in 2015. Moreover, the GBD estimate included all sources of outdoor and indoor pollution—including dust, burning organic matter (such as wildfires and deliberate agricultural fires) and cooking fuels—rather than just fossil fuels.

There are several reasons for the discrepancy. Michael Brauer, who leads the team that assesses environmental risk factors at IHME, points out that the GBD looks specifically at the handful of diseases—including heart disease, heart attack, chronic lung disease, lung cancer, type-2 diabetes and lower respiratory infections—for which it considers there to be a sufficiently strong causal relationship with air pollution. Many other diseases with links to air pollution are not factored into their estimates. (Alzheimer’s disease and dementia, for example, have not yet been included, though they will be in the GBD’s next update.) The paper in Environmental Research, meanwhile, looks at mortality from all possible causes.

The GBD also relies on studies conducted chiefly in North America and Western Europe to establish the relationship between its diseases and air pollution, which are not directly translatable to regions like Africa and Asia, where deaths from other diseases are more common. Eloise Marais, a professor at UCL and one of the authors of the new report, says that its higher estimate was the product, in part, of an updated statistical model that incorporates health studies from Asia, as well as new research into the health impacts of air pollution at both higher and lower concentrations. There are also differences in the methodology used and the GBD’s inclusion of satellite data.

The new research finds that China and India have some of the highest concentrations of PM2.5 in the world, and suffer the highest mortality rates from fossil-fuel air pollution. Indeed, these two countries alone account for some 60% of such deaths worldwide. But there is hope. The paper points out that, between 2012 and 2018, the contribution of fossil-fuel-related pollution to global deaths fell from 21% to 18%. These health gains were almost entirely due to more stringent air-pollution standards in China. The country’s annual average PM2.5 emissions fell by 30-50% in roughly the same period.