A new study suggests that emissions from cars or power plants are not the biggest sources of air pollution. Rather, emissions from farming outweigh these major factors.

Previous studies have found that crop production in farms contributes to the annual carbon dioxide increase in the atmosphere, which is a marker of global warming.

Now, researchers from Columbia University discovered that fumes — from fertilizers and animal waste that are rich in nitrogen — combine with combustion emissions to create solid particles.

The fine particulate matter then becomes a major source of disease and death on Earth, including respiratory problems and heart disease, the study said.

How Farming Negatively Affects The Atmosphere

Manure and fertilizers release ammonia (NH3) into the air, which is swept downwind of farms.

When that happens, ammonia mingles with pollutants such as nitrogen oxide and sulfate, which are produced by factories and vehicles.

After a series of chemical reactions, ammonia molecules and the molecules of pollutants combine to generate gag-inducing particles that are less than 2.5 microns in diameter. These particles earned the name PM 2.5.

PM 2.5 is dangerous. Past studies have estimated the particulate is responsible for at least 3.3 million premature deaths every year.

In 2015, a study found that PM 2.5 can aggravate rheumatoid arthritis. And just recently, the World Health Organization (WHO) revealed that PM 2.5 and other particles create unsafe air for city dwellers.

Regional studies in the United States have revealed that agricultural pollution is a prime source of fine-particulate triggers, but the new study, which looks at broader range, confirms that more than 50 percent of the aerosols in the U.S. come from farming.

There Is Good News

Atmospheric scientist Susanne Bauer, the study's lead author, said the findings do not suggest that using fertilizers is bad.

"There are many places, including Africa, that need more of it," said Bauer.

What's more, the fact that emission from farming combines with other pollutants to produce aerosol is good news.

Most studies say that cleaner and more renewable sources of energy, stricter regulations and vehicles with higher mileage could cut down industrial emission by 2100. If that happens, agricultural emission will be starved of the ingredients it needs to produce aerosols, Bauer said.

The details of the study are published in the journal Geophysical Research Letters.

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