Ammonia from farm animal waste and fertilizers plays a surprising role in producing health-harming air pollution
In the United States alone, air pollution kills about 115,000 people a year — more than three times the number of deaths caused by motor vehicles. Worldwide, some 7 million people died in 2012 alone from exposure to air pollution, according to the World Health Organization. The U.S. and other developed nations have taken major steps in recent decades to decrease pollution emissions from smokestacks and tailpipes. Yet a surprising source of harmful air pollution particles — emissions of ammonia from livestock manure and synthetic fertilizer application — continues to grow in parts of the U.S., Asia and Europe.
“When people think about air quality, they think about factories and power plants and transportation. But agriculture is a substantial contributor to reduced air quality, too,” says Jason Hill, associate professor of bioproducts and biosystems engineering at the University of Minnesota. Potential solutions — say Hill and other experts — will hinge on the efforts of industry, society and government regulators.
The Science on Agricultural Ammonia Emissions
Small air pollution particles can infiltrate deep into the lungs and even enter the bloodstream. In very old people and people with underlying illnesses such as asthma and heart disease, they can make heart and breathing problems worse and may even result in death.
These tiny specks of particulate matter — about 1/30th the width of a human hair — are called PM2.5 and have many sources. Power plants, factories and cars can pump such particles — and the precursors to these particles — into the air. So, too, can natural events, such as forest fires. Sometimes PM2.5 forms when gaseous chemicals react in the atmosphere. Ammonia, a nitrogen-based compound, is one of those chemicals.
In the past 70 years, global emissions of ammonia have more than doubled from 23 to 60 teragrams per year. (One teragram is 1 billion kilograms or 2.2 billion pounds.) Researchers say the increase is due in large part to an increase in ammonia emissions from agriculture. Our ability to grow crops depends on nitrogen, which is a critical plant nutrient. But in overabundance, nitrogen can spell trouble. Nitrogen in animal waste and in excess fertilizer can turn into gaseous ammonia. In fact, in the U.S. and Canada, agriculture accounts for more than three-fourths of all ammonia emissions.