There are more than 15,000 cattle and hog feeding operations in the United States. These operations rear 70% of the country's cattle and 98% of its hogs.
Now, for the first time in the nation's history, we know with certainty where most of them are, thanks to research from the University of Michigan.
The research team found that a quarter of the nation's hog and cattle feeding operations are found in just 30 counties out of more than 3,000 in the United States. Going a step further, the team also found that an air pollutant linked to heart and respiratory issues near these animal feeding operations, or AFOs, was higher than in similar counties without feeding operations.
The team also found that there was a higher likelihood of finding vulnerable and marginalized communities near AFOs. Specifically, these communities were more likely to have lower levels of health insurance coverage and education. They were also more likely to have higher percentages of Latino residents.
"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.
"If you're a policymaker, or a government, or a community group or association concerned with these issues, this allows you to develop very targeted policies or measures," said Newell, a professor at the U-M School for Environment and Sustainability, or SEAS. "That's one of the reasons why mapping this out spatially is so important."
'This doesn't make sense'
The term AFO refers to a specific type of operation where animals are kept and fed for more than 45 days in a year, said lead author Sanaz Chamanara . Animal manure is also kept on site, which plays a significant role in air quality. Aside from its smell, it also contributes to dust and particulate matter that pollute the air.
Although entities like the U.S. Environmental Protection Agency 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, 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 valuable information on where to start looking for the missing AFOs, but Chamanara still had to comb through satellite imagery of every continental U.S. county to locate the operations. This painstaking process was a key element of her doctoral work for SEAS and this new study. But Chamanara is most excited about the future work it will enable.
"The first objective of this project was to develop this dataset to make sure other researchers have access to it," said Chamanara, who now works for Microsoft. "It can be helpful for public health officials and environmental justice researchers."
In addition to identifying locations, Chamanara also mapped the extent of each hog and cattle feeding operation. Based on that analysis, the nation's AFOs occupy an area of about 500,000 football fields, with cattle operations representing almost 80% of that total. For comparison, there are about 16,000 high school football fields in the country, according to the National Football Foundation.
The team's data set can be found online as supplemental information to their study.
"We live in one of the most data-rich countries in the world, yet until Sanaz Chamanara did this work, we didn't have a comprehensive dataset of these massive facilities," said Dimitris Gounaridis , an assistant research scientist with SEAS and a co-author of the paper.
"And we're not claiming this includes every AFO in the U.S., but it's a large enough sample to draw conclusions with confidence."
'It's nasty stuff'
Because nationwide data is available on air quality and the socioeconomic makeup of communities, the U-M 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.
In the U-M study, the team examined air pollution known as PM2.5 as a case study. PM2.5 denotes particulate matter that's 2.5 micrometers or less. That's about a 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 , an assistant professor at SEAS and a senior author of the new study.
The team found that the levels of PM2.5 were, on average, 28% higher near cattle feeding operations and 11% higher near hog operations compared with similar counties without AFOs.
The researchers used census data to analyze the sociodemographic makeup of the communities near feeding operations. While the team's work doesn't answer the question of whether an AFO is built in a certain community or whether a certain community settles around an AFO, that doesn't dilute the study's take-home message.
"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."
