Death in the Air

How much does air pollution affect human health? A new study, published in Nature today, calculates exactly how many people worldwide died of pollution-related causes in 2010: 3.3 million.

The scientific team, led by Jos Lelieveld of the Max Planck Institute, combined data from an atmospheric chemistry circulation model with global air quality changes and population data. Their study also considered country-level health statistics to get the full picture of the cause of these deaths and the seven sources of air pollution that wreak havoc.

The team looked at ozone and particulate matter with diameters 2.5 micrometers or smaller. They discovered that emissions from residential and commercial heating and cooking cause the most deaths—nearly one-third—and primarily affect people in China and India. (This doesn’t even include the indoor air pollution deaths from this source—which reach an additional 3.5 million deaths per year.)

The third leading cause is agriculture. The authors note some uncertainty on this point: particulate emissions of ammonia from fertilizer use and domesticated animals can be less toxic than other particulate sources. Fossil fuel power plants are fourth on the list, affecting those of us here in the U.S., as well as people in Russia, Korea, Turkey, and the Middle East. Industrial manufacturing—production of materials such as iron, steel, chemicals, paper, food, and fuel—comes next.

Emissions from traffic cause one-fifth of the air pollution deaths in the U.S., Germany, and the United Kingdom, but only account for 5% of deaths in other locations.

Last is biomass burning (think of deforestation), and a related paper in Nature Geoscience finds that, at least in Brazil, this number is falling thanks to a reduction in deforestation. The Nature study notes that this number could be higher in African nations due to a lack of health records from certain regions.

These uncertainties highlight the need for more attention to air pollution from agricultural sources, biomass burning, and residential energy use.

The health effects that cause death in these cases include chronic obstructive pulmonary disease, acute respiratory illness, cerebrovascular disease, heart disease, and lung cancer.

The researchers predict that premature mortality from outdoor air pollution could double by 2050—thanks to population growth (especially in urban areas) and increased pollution—reaching 6.6 million deaths per year. But if we are able to reduce air pollution in the coming years, we could decrease this number.