PM2.5 From Fossil Fuels Killing Way More People Than Previously Thought

New research from Harvard University, University of Birmingham, the University of Leicester, and University College London has concluded that 18% of global deaths in 2018, more than 8.7 million people, can be attributed directly to particulate matter smaller than 2.5 micrometers (PM2.5) emitted when burning fossil fuels.

PM2.5 has not been on the radar until recently and is still not well-known or tightly regulated; it was lost in the haze of cigarette smoke, industrial emissions, and car exhaust. As much of the smoke cleared, PM2.5 stood out; we previously quoted research that blamed it for 4.2 million deaths per year, "usually manifested by respiratory or cardiac symptoms, as well as chronically, potentially affecting every organ in the body." It's not known if there is any safe level.

The new research, to be published in Environmental Research, more than doubles the number of deaths, and separates out those due to PM.25 from forest fires and dust, and those due directly to the burning of fossil fuels. This was new; according to the Harvard press release, previous research relied on satellites and couldn't distinguish the source or type of PM2.5. The new research used GEOS-Chem, a high-resolution 3D model that let them divide the planet up into a grid of 50km by 60km boxes. Karn Vohra, the study's first author says “Rather than rely on averages spread across large regions, we wanted to map where the pollution is and where people live, so we could know more exactly what people are breathing.” From the Harvard release:

"To model PM2.5 generated by fossil fuel combustion, the researchers plugged into GEOS-Chem estimates of emissions from multiple sectors, including power, industry, ships, aircraft and ground transportation and simulated detailed oxidant-aerosol chemistry driven by meteorology from the NASA Global Modeling and Assimilation Office. The researchers used emission and meteorology data primarily from 2012 because it was a year not influenced by El Niño, which can worsen or ameliorate air pollution, depending on the region. The researchers updated the data to reflect the significant change in fossil fuel emissions from China, which fell by about half between 2012 and 2018."

It used to be that when we talked about pollution from fossil fuels, we were talking about smog; then in the last few decades, as cars got catalytic converters and power plants got scrubbers, the discussion turned to CO2 emissions and climate change. But Joel Schwartz of the Harvard TH Chan School of Public Health, a co-author of the report, reminds us that pollution is still a problem:

“Often, when we discuss the dangers of fossil fuel combustion, it’s in the context of CO2 and climate change and overlook the potential health impact of the pollutants co-emitted with greenhouse gases. We hope that by quantifying the health consequences of fossil fuel combustion, we can send a clear message to policymakers and stakeholders of the benefits of a transition to alternative energy sources.”

The study specifically separated PM2.5 emissions from fossil fuels from other sources, most notably dust and biogenic sources like forest fires that add up to a substantial portion. However, the doubling of the estimate of deaths from particulate pollution makes it clear that we have to clean up all sources of PM2.5. This means, regretfully, giving up wood fires, electrifying everything, getting rid of gas stoves, dealing with traffic abrasion by regulating the weight of cars, and providing better ventilation and air filtration indoors. Every new study just piles on more evidence about how bad PM2.5 pollution really is. But burning fossil fuels – for power, heating, cooking, or transportation – is still the worst source; as the study co-author Eloise Marais notes:

“Our study adds to the mounting evidence that air pollution from ongoing dependence on fossil fuels is detrimental to global health. We can’t in good conscience continue to rely on fossil fuels, when we know that there are such severe effects on health and viable, cleaner alternatives.”