Factory farms don’t just stink — they make it harder to breathe, too 

New research out this week underscores what many environmental justice advocates in the U.S. have long known: Animal feeding operations — another term for factory farming — pollute the air, and these environmental impacts are disproportionately felt by nearby communities, who are often people of color.

The report, published Tuesday and led by researchers at the University of California, Santa Barbara and the University of Michigan, maps cattle and hog farms across the United States at the county level — and finds that these animal feeding operations tend to be sited in communities with higher percentages of Latino residents and uninsured residents. Fine particulate matter — or PM2.5 — levels in census tracts with cattle operations are 28 percent higher than similar census tracts without, according to the report. In census tracts with hog farms, PM2.5 levels were found to be 11 percent higher than those without. 

In their report, the authors caution that the air pollution burden in these areas could lead to more emergency room visits and hospitalizations — which itself poses significant financial problems for residents lacking adequate health insurance coverage. Environmental experts say that lack of governmental oversight into industrial animal agriculture, combined with rising temperatures caused by climate change, put these vulnerable communities at risk of various health problems.

It’s the study authors’ hope that their data could aid campaigns to better regulate cattle and hog production and lessen their environmental impact, especially at the local level. The study found that roughly a quarter of animal feeding operations, or AFOs, are located in just 30 counties across the U.S. 

“That’s a huge spatial concentration,” said Joshua Newell, a professor of environment and sustainability at the University of Michigan and one of the study’s authors. Knowing where cattle and hog operations are clustered “allows us to really, if we’re concerned about AFOs, develop targeted policies” aimed at the county level, said Newell.

The environmental impacts of livestock production have been well-documented. Not only does raising cattle, for example, require a lot of water, but the animal waste produced by farmed animals can also contaminate nearby waterways. Air pollution on AFOs stems from livestock kicking up dust, as well as how manure is stored; in the case of cattle and hogs, it’s open-air lagoons.  

While research has clearly illuminated the connection between animal agriculture and environmental degradation, the federal government has done little to regulate this part of the U.S. food system. Just this week, the Environmental Protection Agency ruled that animal farms do not have to disclose toxic air emissions. 

Still, researchers interested in studying the public health impacts of AFOs — also sometimes called concentrated animal feeding operations, or CAFOs — face hurdles: To start, nationwide data on these facilities is scarce. As part of their research, the study authors pulled state and regional data on AFOs from the EPA. But they found that these sources were incomplete and often outdated, said Newell. 

In order to fill in these gaps, the researchers used EPA data as well as two other existing datasets on animal agriculture. Stitching together the three datasets, they identified AFOs and removed duplicates, and then verified their results with high-resolution satellite imagery from Google Earth. Then, using U.S. Department of Agriculture reports on cattle and hog production, they also zoomed in on other meat-producing regions and added in AFOs that were left out of the initial three datasets. 

With that map in hand, the team compared the dispersal of AFOs across the country to nationwide PM2.5 levels. They also attempted to capture the makeup of communities nearby, looking at the percentage of Latino residents, uninsured residents, and residents without a high school diploma. 

The resulting map is a telling, if incomplete, picture of how the heavily industrialized food system in the U.S. impacts vulnerable communities. The new data has limitations: For example, the team did not include poultry farms in their research. They also did not look into the relationship between AFOs and Latinos — such as whether these residents choose to live close to these facilities in order  to pursue jobs in animal agriculture, or whether these communities were already in place when industry moved in. Newell said he hopes their work will be a jumping off point for additional research that benefits this crucial environmental justice question.

A truly comprehensive, nationwide look at where meat producers operate in the U.S. is hard to come by, said Valerie Baron, a national policy director and senior attorney at the National Resource Defense Council. That’s partly because of “a systemic effort by the industry to escape transparency and liability,” she continued.

“These facilities emit massive amounts of really, really noxious stuff,” said Baron. Air pollution on AFOs stems from the way manure is stored; on cattle and hog operations, which produce tremendous amounts of manure, the animal waste is kept in large anaerobic lagoons. These can be as large as football fields, says Baron, and emit ammonia and hydrogen sulfide as the manure decomposes. These compounds in and of themselves are dangerous — exposure to hydrogen sulfide can be fatal and even small amounts of the gas can lead to myriad health problems — but they can also mix together in the air and form PM2.5.  

Academic and crowd-sourced efforts to document the animal agriculture industry’s impact on both the environment and the people who work at or live next door to such facilities are useful in building public awareness of the harms of meat production. “It is incredibly important that the public have access to basic information about dangerous facilities, including industrial animal agriculture,” said Baron. But it doesn’t automatically translate into action. Data is “cold comfort to someone whose child has asthma or someone who’s struggling to breathe living next door to one.”

For Rania Masri, the co-director of the North Carolina Environmental Justice Network, the University of Michigan study felt like something her team could use as part of their advocacy campaigns. But she wasn’t surprised by the findings, particularly with the prevalence of hog farms in North Carolina. While national data on AFOs may be hard to come by, research on the impact of hog farming on Black and brown residents in North Carolina is widely available; its roots go back to slavery.

“I would argue, in North Carolina and across the country, we have enough research. We really do,” said Masri. “We have enough research to prove that this is systemic. This is by design. This is targeted in Black and brown communities.”

Of the 10 counties with the highest number of hog farms, four — including the two top — are in North Carolina. “That is quite significant,” said Masri. She sees this as an opportunity for environmental justice advocates to push for specific, county-level solutions that can address community members’ needs. 

Baron worries that, as global temperatures rise, the communities already dealing with poor air quality will be hit hard by extreme heat. In a state like California with a lot of animal agriculture, PM2.5 can be a precursor to smog. “The impact of climate change in areas where water is more scarce, plus extreme heat, really put extra stress on the air quality in that area,” said Baron. Workers in these industries may have a harder time dealing with respiratory problems caused by air pollution if they’re also dealing with a heat wave, for example. “I’m very concerned about the impact that increased heat will have,” she added.

Newell says that even before this report came out, community organizations and Indigenous groups he was in touch with were eager to see their data. Making it open-source and public was always part of the goal of this research. Whether or not it helps change the power dynamic in the animal agriculture industry is another question. “I think that is powerful, you know,” said Masri. But in North Carolina, “we do have a Republican-majority general assembly. And the agricultural industry has bipartisan clout.”

This story was originally published by Grist with the headline Factory farms don’t just stink — they make it harder to breathe, too  on Aug 15, 2025.