Air pollution remains a major cause of death in the United States, one usually associated with tailpipe exhaust and factory and power plant smokestacks. Now new research shows that 16,000 U.S. deaths are the result of air polluted by growing and raising food—and 80 percent of those result from producing animal products like meat, dairy, and eggs.
Additional deaths are attributable to products we don’t eat, including ethanol, leather, or wool. That brings the total number of deaths from agricultural air pollution to 17,900 a year.
“We spend a lot of time thinking about how the food we consume impacts our health, but the food we eat impacts other people’s as well,” says Nina Domingo, lead author of a new study, published May 10 in the Proceedings of the National Academy of Sciences, that analyzes which food products contribute most to lethal air quality.
The environmental impact of certain foods—such as their carbon footprint and land or water use—has been researched for more than a decade. But the new study is the first to identify which individual foods and diets have the biggest effect on the air pollution that causes asthma, heart attacks, and strokes.
“The long-term effects of climate change are daunting and quite frightening, but this is killing people now, too,” says Jason Hill, a University of Minnesota biosystems engineer and senior author. “These are emissions that happen every year, that affect people, that lead to a poor quality of life.”
Industry groups criticized the study. The National Cattlemen’s Beef Association, an industry trade group that reviewed the findings, dismissed the study as “based on faulty assumptions and riddled with data gaps.” The association characterized the study as a “misleading” contributor to “a false narrative around animal agriculture.” The American Farm Bureau Federation made similar claims saying it stretched “the definition of cause and effect.”
“All the models have been extensively peer-reviewed and have been widely used by our group and by many others,” says Hill.
Finding the deadliest food
To determine the health impact of animal-related products, the study’s authors looked at what it takes to produce them—such as fertilizing crops, tilling land, burning diesel engine tractors, and managing the waste produced by livestock.
“So much of our agriculture is driven by animal agriculture. Not just the animals themselves, but what goes into feeding them,” Hill says.
Growing corn for food, fuel, and livestock feed, for instance, corresponds to 3,700 deaths every year as a result of toxic air. When the study’s authors calculated the air quality-related deaths caused by producing livestock and the crops they require, they found that beef alone corresponded with 4,000 air pollution-related deaths every year. When pork and dairy production were added to the calculation, such production contributed to 9,100 deaths annually.
In contrast, vegetables, the category encompassing the corn that humans eat, contributes to 100 deaths, they found.
The negative impact of air quality due to corn grown to feed people is “so small as to almost be imperceptible there. Almost none of the corn we grow is sweet corn. It’s far less than one percent,” says Hill.
“We try really hard not to come into a study with preconceived notions,” says Domingo, who specializes in biosystems engineering at the University of Minnesota. “But it’s striking to see how they’re concentrated in a few food groups.”
Should we all go vegan?
The study also outlines a number of remedies that could be undertaken by farmers and consumers to reduce air pollution from agriculture. Better management of waste from livestock and more efficient application of fertilizer are among the recommendations. If all the recommended changes were applied to farms, the scientists estimate that 7,900 lives could be saved every year.
Individuals can affect change, as well. If consumers adopted a national dietary shift it would have a big impact on air quality, the scientists say. If the U.S. changed dietary preferences from red meat to poultry, for instance, they estimated 6,300 deaths could be prevented. By going vegetarian, vegan, or flexitarian—eating meat sparingly—consumers could prevent anywhere from 10,700 deaths to 13,100 deaths as a result of air pollution, they estimate.
“One of the great pieces of advice I got early on in my career is when you point out a problem, also point out a solution. It’s one thing if we point out that 18,000 people die from [toxic air] every year, but how do you solve that problem?” says Hill.
Tracking deadly particles
The study was launched to learn about what foods and diets are contributing to reduced air quality. Researchers used data from the Environmental Protection Agency’s National Emissions Inventory, which tracks air pollution in the U.S.
“It’s an extremely detailed inventory of all emission sources that contribute to air pollution, in particular PM 2.5, [which] has the largest impact of air pollutants,” says Hall.
Their models were based on research estimating 100,000 people die from air pollution in the U.S. every year, though that number can range from anywhere from 60,000 to 200,000.
The paper models the effect of PM 2.5, a type of pollution called fine particulate matter. Such microscopic particles, which measure 2.5 microns in diameter, are more than 100 times thinner than a human hair. These particulates are formed by hundreds of different sources, including wildfires, car exhaust, and factory emissions. They are small enough to lodge their way into the lungs and can cause respiratory and heart problems.
In agriculture, PM 2.5 can come directly from dust, tilling the land, or exhaust from diesel combustion engines used by tractors. It is also created from pollutants like the ammonia—found in fertilizer, manure, and animal waste lagoons—undergoing chemical changes in the atmosphere that turn the gaseous pollutant into particulates.
The scientists used data to run three complex models looking at how PM 2.5 emissions move through the atmosphere and how many people might breathe it in. Using U.S. census data, researchers were able to estimate how many people would be made sick over time.
“If you were to expose a population to a certain amount of a toxin, you would expect a certain number to die from that toxin,” says Hill.
The Cattlemen’s Association challenged the modeling methods and EPA data. Ethan Lane, the group’s vice president for government affairs, said in a statement that the research “attempts to cultivate a misleading narrative that ammonia emissions from farms are responsible for thousands of deaths. No such federal methodologies for agriculture exist, which casts serious doubt on the accuracy of these conclusions.”
The American Farm Bureau, in a statement, suggested the scientists made “giant leaps to stretch the definition of cause and effect. Let’s not forget that U.S. farmers and ranchers are responsible for 330 million American lives, providing the food that sustains all of us, in addition to addressing food insecurity around the world.”
How does bad air affect the body?
When PM 2.5 is inhaled, it irritates the respiratory system and prompts the body’s immune system to attack the pollutant. The body produces a protein called a cytokine “that sends out a message that we have a problem here, and we need to initiate an inflammatory response,” says Jack Harkema, a toxicologist at Michigan State University who was not involved with the paper.
When air pollution is inhaled regularly over time, the sustained immune response damages other parts of the body beyond the respiratory system.
“We know what the direct effect is of [PM 2.5] on the lung. That can cause diseases and chronic inflammation like asthma, but the cardiovascular part of this is a little bit different,” says Harkema.
“We think the cytokines are transported into the heart and other areas, and they can generate an inflammatory response there,” he says. PM 2.5 is known to predispose people to heart attacks by disrupting the nervous system and making a person more likely to develop a blood clot.
Harkema, who served on the EPA’s Clean Air Science Advisory Committee during the Obama administration, says he hopes this new research dispels a widely held belief that air pollution is primarily a problem of population density.
“A lot of people think of particulate matter air pollution as associated with urban areas. And there hasn’t been a lot of this in rural areas,” he says. “This brings it to the forefront.”