Air pollution is killing 3.3m people a year worldwide, according to a new study. Surprisingly, farming plays a large role in soot-and-smog deaths in industrial nations.
Scientists in Germany, Cyprus, Saudi Arabia, and Harvard University calculated the most detailed estimates yet of the toll of air pollution, and what caused it. The study projects that if trends don’t change, the yearly death total will have doubled to 6.6m a year by 2050.
The study, published in the journal Nature, showed that three quarters of the deaths are from strokes and heart attacks, said lead author Jos Lelieveld at the Max Planck Institute for Chemistry in Germany.
The findings are similar to other, less detailed pollution death estimates, outside experts said. “About 6% of all global deaths each year occur prematurely, due to exposure to ambient air pollution. This number is higher than most experts would have expected, say, 10 years ago,” said Jason West, a University of North Carolina environmental sciences professor who wasn’t part of the study, but who praised it.
Air pollution kills more than HIV and malaria combined. China has the most air pollution fatalities, with 1.4m, followed by India, with 645,000, and Pakistan, with 110,000. The United States, with 54,905 deaths in 2010, ranks seventh. What is unusual is that the study says agriculture caused 16,221 of those deaths, second only to 16,929 deaths blamed on power plants.
In the US northeast, all of Europe, Russia, Japan, and South Korea, agriculture is the leading cause of soot-and-smog deaths. Worldwide, agriculture is the second-biggest cause, with 664,100 deaths, behind 1m deaths from in-home heating and cooking done with wood, and other biofuels, in the developing world.
The problem with farms is ammonia from fertiliser and animal waste. That ammonia combines with sulphates from coal-fired power plants, and with nitrates from car exhaust, to form the soot particles that are the big air pollution killers, he said.
In London, for example, the pollution from traffic takes time to be converted into soot, and then it is mixed with ammonia and transported downwind to the next city, he said.
“We were very surprised, but, in the end, it makes sense,” Lelieveld said.
He said the scientists had assumed that traffic and power plants would be the biggest cause of deadly soot and smog.
Agricultural emissions are becoming increasingly important, but are not regulated, said Allen Robinson, an engineering professor at Carnegie Mellon University, who was not part of the study, but who praised it.
Ammonia air pollution from farms can be reduced “at relatively low costs,” Robinson said. “Maybe this will help bring more attention to the issue.”
In the central United States, the main cause of soot-and-smog premature deaths is power plants; in much of the West, it’s traffic emissions.
Jason West, and other outside scientists, did dispute the study’s projections that deaths would double by 2050. That is based on no change in air pollution. West and others said it’s likely that some places, such as China, will dramatically cut their air pollution by 2050.
And Lelieveld said that if the world reduces a different air pollutant — carbon dioxide, the main gas causing global warming — soot-and-smog levels will be reduced as well, in a “win-win situation in both directions”.
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