In Tulare County, California, the air is among the worst in the United States when it comes to pollutants like fine particulate matter (PM2.5). As a report from Friends of the Earth about dairy factory farms in Tulare states, “Community members struggle to access clean water and are suffocated by dismal air quality.” And the research is very clear: PM2.5 levels are associated with higher rates of cardiovascular disease and lung cancer.
Air pollution, in general, is one of the biggest killers worldwide.
And as it happens, no county in California has more animal factories than Tulare, where hundreds of facilities confine thousands of animals apiece. In fact, more than 70 million animals are farmed in California. Over 50 million of them are chickens raised for meat.
The combination of a lot of confined animals and high rates of air pollution is not unique to Tulare County; it describes a number of counties in California, the country’s largest dairy state. The scale of the industry in this region is difficult to overstate. California is home to over 1.7 million dairy cows, the vast majority concentrated in an agricultural corridor that runs through Fresno, Tulare, Kings, Merced, Stanislaus, and Kern counties. The presence of the dairy industry in the region has been heavily implicated in the contamination of available drinking water, among other harms.
Then, when you consider beef operations and chicken facilities, the density of animals in a relatively small geographic area is among the highest anywhere in the country.
Concentrated animal feeding operations (CAFOs) in general are one of the largest sources of pollution in American agriculture. They emit ammonia, hydrogen sulfide, and volatile organic compounds which react in the atmosphere to form particulate matter and ozone. A 2025 University of Michigan study published in Communications Earth & Environment found that PM2.5 levels are 28 percent higher in US census tracts with cattle operations than in tracts without them.
To understand what this looks like in California specifically, we used the Stanford Industrial Animal Agriculture Dashboard, a tool that maps CAFOs across the state alongside related data on particulate matter pollution, nitrate concentrations, and other metrics. We looked at California’s top ten counties across three measures: particulate matter, ozone, and asthma rates. We found that eight of California’s ten most polluted counties by PM2.5 have a lot of factory farms. The top four are all Central Valley agricultural counties that together host over 600 farms, the vast majority of which would be considered “factory farms” on any sensible definition. And the same pattern holds for ozone and asthma. Nine of California’s ten most ozone-burdened counties have factory farms, as do nine of the ten with the highest asthma rates.
These results aren’t surprising. Factory farms have numerous external harms that are pushed onto the general public like air pollution, water pollution, carbon emissions, increasing antibiotic resistance, and more. At the same time, they receive sizable public subsidies that support and maintain some of their worst practices. Reducing pollution in places like Kings County means contending with the industry that, in large part, produces it. Until that changes, denizens of Kings and Tulare counties will keep paying for cheap, factory-farmed milk with their lungs.