New research from the Harvard T.H. Chan School of Public Health explains that fossil fuel pollution could be responsible for 1 in 5 adult deaths worldwide.

Discussions around the use of fossil fuels today mostly revolve around their environmental impact, as well they should. But the life around us isn’t the only one that has to bear the costs of our reliance on such substances — their use, a new paper reports, has a human cost as well.

According to the authors, pollution generated by the burning of fossil fuels was responsible for around 8 million premature deaths in 2018, roughly 20% of all adult deaths worldwide in that year. The most heavily polluted areas saw the lion’s share of these deaths.

Burn hard die young

Half of those premature deaths were recorded in China and India, with Bangladesh, Indonesia, Japan, and the United States making up the rest. The deadly effects of fossil fuel pollution come down to the tiny particles (PM, particulate matter) generated by the burning of oil, gas, and especially coal. In around six Asian nations, such pollution accounts for over one-quarter of all mortality, the team adds.

However, that also means that lowering our use of fossil fuels, or at least finding ways to keep air quality in check, can prevent all those excess deaths.

All in all, air pollution is responsible for reducing the average lifespan by 4.1 years in China, 3.9 years in India, 3.8 years in Pakistan, and around 8 months on average in Europe. This goes to show how hard air pollution impacts Asia compared to both more developed and less developed areas. The figures reported in this paper are almost double those of previous estimates.

Previous estimates of deaths related to fossil fuel pollution were based on satellite data and surface-level observations to determine concentrations of PM2.5, the most deadly kind of particulate matter. These estimates, most recently provided by World Health Organization through the Global Burden of Disease, puts this number at around 7 million, with around 4 million of those being caused by outdoor pollution.

One limitation of these previous studies, however, is that they cannot determine the origin of the particles in question — these could come from burning fossil fuel as well as dust or wildfires. To get a better idea of their origin (and thus, how much of the problem is caused by fossil fuels) the team used GEOS-Chem, a 3-D atmospheric chemistry model, to look at the Earth’s surface in 50-by-60-kilometer (30-by-36-mile) blocks.

“Rather than rely on averages spread across large regions, we wanted to map where the pollution is and where people live,” said lead author Karn Vohra, a graduate student at the University of Birmingham.

Next, they fed in data regarding carbon emissions from several key fields, as well as NASA simulations of air circulation. After they calculated PM2.5 levels for each block, they used a novel risk assessment model to estimate how much damage these would cause public health, leading to the reported figures. Among the most common effects of air pollution, the team lists coronary heart disease and stroke (around half), followed by lung diseases and non-communicable conditions such as diabetes and high blood pressure for most of the rest.

The paper is awaiting publication in the journal Environmental Letters and is currently available on Harvard’s page.