Food production, primarily the raising of livestock, causes poor air quality that is responsible for  about 16,000 deaths a year in the United States, roughly the same number from other sources of air pollution, including transportation and electricity generation, according to research published Monday.

The study, in the journal Proceedings of the National Academies of Sciences, is the first ever to look at the air quality impacts of specific foods and production systems, and comes as livestock agriculture is increasingly scrutinized for its climate-warming impacts.

“There’s been a lot of focus on the climate change impacts of food production, and water quality, water use, land footprints and biodiversity impacts, but what’s been missing are the air quality impacts,” said Jason Hill, a professor of bioproducts and biosystems engineering at the University of Minnesota, which led the study. “Air quality is the largest environmental contributor to human health damage and agriculture is known to be a contributor to reduced air quality, but there’s been a disconnect until now.”

The team found that of the nearly 16,000 deaths resulting from food production, 80 percent were linked to animal based foods. (Roughly 100,000 people die from air pollution a year, Hill said.)

Many of those deaths were in areas with high concentrations of livestock production and CAFOs—concentrated animal feeding operations—including North Carolina and areas in the Upper Midwestern Corn Belt, especially east of Iowa where wind blows in to large population centers from the state’s hog-producing areas.

Using three different models, researchers looked at 95 agricultural commodities and 67 food products, making up 99 percent of agricultural production in the U.S. They tracked how each of these products increased levels of fine particulate matter, or PM 2.5, in the air. PM 2.5 exposure can lead to heart disease, cancer, stroke and respiratory illnesses.

Per serving, the air-quality impacts of red meat, including pork, was two times that of eggs, three times that of dairy, seven times that of poultry, 10 times that of nuts and seeds and at least 15 times that of other plant-based foods, the study said.

The livestock industry blasted the study Monday, calling it “misleading.” No “federal methodologies for agriculture exist, which casts serious doubt on the accuracy of these conclusions,” said Ethan Lane, vice president of government affairs for the National Cattlemen’s Beef Association, in an email. “Based on the short time we’ve had to review the information, it appears to be based on faulty assumptions and riddled with data gaps.”

Much of the negative air quality impact from agriculture is attributable to ammonia, which mixes with other pollutants to form PM 2.5 but is not considered a “criteria,” or regulated, pollutant.  Nitrogen-based fertilizers and manure are the primary sources of ammonia from agriculture.

The researchers found that plant-based diets could reduce air quality-related deaths by as much as 83 percent. Substituting poultry for red meat could prevent 6,300 annual deaths and 10,700 “could be achieved from more ambitious shifts to vegetarian, vegan or flexitarian diets such as the planetary health diet of the EAT-Lancet Commission,” the study found.

“Producers can produce food in more sustainable ways and consumers can eat foods that are better for air quality,” Hill said. “And interestingly, those things have co-benefits for climate change and for health. It’s another good reason to eat a plant-rich diet.”

Agricultural emissions, in general, are largely unregulated. 

“Current diets and food production practices cause substantial damages to human health via reduced air quality; however, their corresponding emissions sources, particularly ammonia, are lightly regulated compared to other sources of air pollution, such as motor vehicles and electricity production,” the authors concluded. “This is true despite agriculture having comparable health damages to these other sources of pollution.”

The authors of the study found that while dietary changes could have the biggest impact on lowering air quality, changes in agricultural practices, including using less fertilizer and better managing manure, could also have significant impacts. 

The research was conducted by a large team, including engineers, agriculture specialists and air quality experts, many supported by an Environmental Protection Agency grant.  

The authors said that, while the work focused on the United States, their approach could be used globally.

“Globally this is a much larger problem. In India and China,” Hill said. “If you looked more broadly some of these similar trends will apply.”