For decades scientists have known airborne particles are a danger to public health, but there have been few epidemiological studies to quantify the effects of very high levels of exposure like in India and China.
For this study, researchers intentionally chose to use data from 2012, when the El Nino weather pattern was in a “neutral” phase, and did not affect air pollution levels at the time. If data from another year was used, they said, the estimates of mortality might have been higher or lower.
But the researchers updated the China data for 2018, because of the large cut in fossil fuel pollution in that country after 2012.
Ben Ewald, an epidemiologist at the University of Newcastle and member of Doctors for the Environment Australia, said health damage from fossil fuel use was substantial, local and immediate.
“The climate-related harms to health are also substantial, but they are global and delayed,” Dr Ewald said.
“These are powerful reasons not only to phase out fossil fuels, but to ensure best-practice pollution controls are fitted to power plants and vehicles that have to continue operating during the transition years.”
The study greatly increases the estimate of numbers killed by air pollution. In comparison, the most recent Global Burden of Disease study, the most comprehensive study on the causes of global mortality, put the total number of deaths for airborne pollution – including from dust, smoke and agricultural burns – at 4.2 million a year.
This is because previous research used satellite and surface observations to estimate the annual concentrations of airborne particulates (PM2.5s), but satellite observations can’t distinguish between particles from fossil fuels and those from other sources.
So researchers used new spatial modelling to divide the globe into a 3D grid, containing “boxes” as small as 50 kilometres by 60 kilometres, and worked out the pollution levels in each “box” individually.
Co-author Joel Schwartz, an environmental epidemiologist at the Harvard Chan School of Public Health, said the dangers of fossil fuel combustion was often discussed in the context of climate change and the immediate health impact of pollutants was overlooked.
“Our study adds to the mounting evidence that air pollution from ongoing dependence on fossil fuels is detrimental to global health,” Professor Schwartz said.
Miki Perkins is a senior journalist and Environment Reporter at The Age.