Americans in about three dozen counties are being exposed to dangerous air pollution that puts them at a heightened risk of cardiovascular disease.
A research team from the University of Michigan constructed a map of the more than 15,000 cattle and hog feeding operations in the US and found a quarter are located in just 30 US counties out of more than 3,000.
Based on the analysis, the factory farms occupy an area of about 500,000 football fields, with cattle operations representing almost 80 percent of that total. For comparison, there are about 16,000 high school football fields in the country.
Researchers found that these factory farms are putting millions of Americans at risk of heart disease, the leading cause of death in the US, and respiratory issues by pumping out high amounts of pollutants called PM2.5.
PM2.5 levels in the air near the animal feeding operations, or AFOs (large-scale facilities where animals are confined for concentrated feeding), were higher than in similar counties without such operations.
PM2.5 levels were 28 percent higher than average in tracts of land with cattle operations and 11 percent higher in areas with hog farms.
Both short-term and long-term exposure to PM2.5 has been found to trigger heart attacks, stroke, and other cardiovascular events.
Some states with the highest density of factory farms (more than 300 per county) include Idaho, California, Utah, Nebraska, Kansas, Oklahoma, Texas, New Mexico and Arizona.
Cardiovascular diseases, including heart disease and stroke, claim more lives than all forms of cancer and accidental deaths combined
In the study, the researchers focused on PM2.5 levels.
PM2.5 denotes particulate matter that is 2.5 micrometers or less. They are about one millionth of an inch, meaning these particles are easily inhaled by anyone exposed to them.
The pollution is linked to a number of heart, lung and airway health effects.
‘It lingers in the air and can get really deep into your lungs and create scar tissue. It’s nasty stuff. There are really no safe levels of it,’ said Benjamin Goldstein, a senior author of the new study.
The researchers note that the American Medical Association has estimated that for every 10 micrograms per cubic meter (10μg/m3) increase in PM2.5, there is a corresponding four percent increase in overall mortality, with a six percent increase in cardiopulmonary mortality and an eight percent increase in lung cancer mortality.
These health impacts have been observed at communities up to 11 miles from AFOs.
In the study, an analysis revealed that tracts of land with cattle AFOs exhibit an average PM2.5 concentration of 7.7μg/m3.
This is 1.7μg/m3 higher than identical tracts without these facilities.
Similarly, the areas with hog farms show an average PM2.5 concentration of 9.2μg/m3, which is 0.9μg/m3 higher than spots without such facilities.
The researchers found cattle farms are primarily concentrated in select counties within California, Wisconsin, Nebraska, Idaho, Iowa, and Texas, while hog farms are mostly clustered in Iowa, North Carolina, Minnesota, Oklahoma, and Missouri
The researchers said of these findings: ‘These confirm that AFOs are associated with elevated local PM2.5 levels. Given the absence of a safe PM2.5 exposure limits, even slight increases in particulate pollution from AFOs pose health risks to nearby populations.’
AFOs release a variety of air pollutants including ammonia, hydrogen sulfide, methane, particulate matter (PM), and volatile organic compounds (VOCs).
The researchers said: ‘Because of high stocking densities at AFOs, vegetation is scarce, and animal hooves often kick up dust.
‘The sheer number of animals also produce immense volumes of manure and urine.
‘These activities generate airborne particulate matter, both directly as dust and indirectly through precursors volatilized at manure lagoons.’
The researchers found cattle farms are primarily concentrated in select counties within California, Wisconsin, Nebraska, Idaho, Iowa, and Texas, while hog farms are mostly clustered in Iowa, North Carolina, Minnesota, Oklahoma, and Missouri.
Several of these states have the highest rates of heart disease mortality in the US.
Cardiovascular diseases, including heart disease and stroke, claim more lives than all forms of cancer and accidental deaths combined, according to the American Heart Association.
It has been the leading cause of death in the US since 1950. In 2023, it was responsible for about one in three deaths, killing 919,000 people.
According to 2022 CDC data, the latest statewide available, Oklahoma had the highest heart disease mortality at 257 deaths per 100,000 people.
And the leading cause of death in all the other states, aside from Minnesota, is heart disease.
Previous studies have found that people who live within a few miles of an animal feeding operation are more likely to die from a cardiovascular problem than people who do not live near an animal facility.
The pollutants have also been found to increase the risk of contracting respiratory illnesses like asthma and bronchitis.
The researchers said they were concerned to find that communities near AFOs are ‘often lower income, less educated, and composed of higher proportions of racial minorities compared to more distant neighborhoods’.
AFOs release a variety of air pollutants including ammonia, hydrogen sulfide, methane, particulate matter (PM), and volatile organic compounds (VOCs)
Specifically, these communities were more likely to have lower levels of health insurance coverage
‘One of the things that this study reveals is that we could focus on a limited number of counties to really address health impacts in these communities,’ said Joshua Newell, a senior author of the report published in Communications Earth & Environment.
He added that creating the map is important for policymakers, governments, and community groups to ‘develop very targeted policies or measures’ moving forward.
Although entities like the EPA and the Department of Agriculture do collect some data on AFOs, there’s variability and inconsistency in how that data is reported across the country.
As a result, the existent body of data was messy and limited in its scope and accuracy, lead author Sanaz Chamanara said.
For example, she combined government data to start with an original list of more than 10,000 AFO locations.
But as Chamanara started verifying those locations with satellite imagery, she found thousands of sites without active AFOs.
‘I can’t remember the exact numbers, but, at the end, the data contained just about 5,000 locations,’ Chamanara said, a number that was far too low to be accurate. ‘I saw that and said, “This doesn’t make sense.” And that’s when I started developing the whole data set.’
A community science project called Counterglow provided information on where to start looking for the missing AFOs, but Chamanara still had to comb through satellite imagery of every continental US county to locate the operations.
Because nationwide data is available on air quality and the socioeconomic makeup of communities, the team could use its new data and systematically examine correlations with the presence of AFOs on an ‘unprecedented scale’.
Researchers have examined such connections before, but previous studies were constrained to much smaller, local extents.
The researchers used census data to analyze the sociodemographic makeup of the communities near feeding operations.
‘The meat you eat comes from somewhere. It takes up a lot of space and produces a lot of pollution,’ Goldstein said. ‘And somebody else and place has to bear that pollution.’
