Air pollution from fossil fuel use is killing 5 million people worldwide every year, a death toll much higher than previously estimated, according to the largest study of its kind. The stark figures, published on the eve of the Cop28 climate summit in Dubai, will increase pressure on world leaders to take action. Among the decisions they must make at the UN conference will be whether to agree, for the first time, to gradually “phase out” fossil fuels. Research has shown that switching from fossil fuels to clean, renewable energy sources would save many lives from air pollution and help combat global heating. However, until now, mortality estimates have varied widely. A new modelling study suggests air pollution, from the use of fossil fuels in industry, power generation, and transportation, accounts for 5.1 million avoidable deaths a year globally. These findings were published in The BMJ. The contribution of fossil fuels equates to 61% of a total estimated 8.3 million deaths worldwide due to outdoor air pollution from all sources in 2019. The new estimates of fossil fuel-related deaths are larger than most previously reported values, suggesting that phasing out fossil fuels might have a greater impact on attributable mortality than previously thought. “Our results suggest that a global phase-out of fossil fuels will have large health benefits, much larger than indicated by most previous studies,” the global team of researchers wrote in the BMJ. “These data support increasing the share of clean, renewable energy, advocated by the UN through the sustainable development goals for 2030 and the ambition of climate neutrality for 2050.” Ambient air pollution is the leading environmental health risk factor for illness and death, but few global studies have attributed deaths to specific air pollution sources and their results widely differ. To address this, an international team of researchers from the UK, US, Germany, Spain and Cyprus, used a new model to estimate deaths due to air pollution related to fossil fuels, and to assess potential health benefits from policies that replace fossil fuels with clean, renewable energy sources. They assessed excess deaths using data from the Global Burden of Disease 2019 study, as well as Nasa satellite-based fine particulate matter and population data, and atmospheric chemistry, aerosol, and relative risk modelling for 2019. The results show that in 2019, 8.3 million deaths worldwide were attributable to fine particles (PM2.5) and ozone (O 3 ) in ambient air, of which 61% (5.1 million) were linked to fossil fuels. “Major reductions in air pollution emissions, notably through a phase-out of fossil fuels, could have large, positive health outcomes. Results show that the mortality burden attributable to air pollution from fossil fuel use is higher than most previous estimates,” the researchers wrote. They said one reason for their model producing larger estimates than most previous studies was its being based solely on studies of outdoor air pollution. Uncertainty remained but given the Paris climate agreement’s goal of climate neutrality by 2050, “the replacement of fossil fuels by clean, renewable energy sources would have tremendous public health and climate co-benefits”.