It May Not Smell Great, but Dust From Dairy Farms Could Have Health Benefits

Being exposed to bacteria from farms can reduce rates of asthma and allergies—but the long-term reality of working on a farm is far more complex.

(Photo: Nick Moir/Getty Images)

Sep 8, 2015· 2 MIN READ
Tove Danovich is a journalist based in Portland, Oregon.

Just smell that fresh dairy air. It’s a mixture of all the things that make a farm smell like a farm—throw in a little cow dander, the smell of fresh-cut grass and sun, and don’t forget the bacteria. While those more discernible scents are what tell you you're in farm country, it turns out the microbes that linger in the air may be worth more attention: They might have beneficial effects on the respiratory system.

A recent study published in Science found that dust from dairy farms may be good for growing lungs. Mice exposed to farm dust over a long period of time had no respiratory reactions to house dust mites, a common allergen in humans. In human studies, a much lower percentage of adults who grew up on farms have respiratory problems than does the general population.

As Bart Lambrecht, one of the study’s authors and a professor of pulmonary medicine at Ghent University, told The Guardian, “At this point, we have revealed an actual link between farm dust and protection against asthma and allergies.” The findings support the popular “hygiene hypothesis,” which conjectures that early exposure to bacteria and allergens may help build immune systems in such a way as to prevent allergies and illnesses later in life. Rolling around in the dirt may not seem all that hygienic in the moment, but in the long term, it’s much better for you than a constant stream of germ-killing hand sanitizers.

While farm dust may have beneficial effects on its own, before people rush off to cure their kid’s asthma by sending him to work in the fields, it’s important to note that agricultural work commonly comes with negative health effects. While a mom-and-pop dairy farm might be the setting for an idyllic pastoral childhood, that’s not what most farms look like today. Manure lagoons that are a common fixture at concentrated animal feeding operations release ammonia, hydrogen sulfide, and methane into the air. A report from the Centers for Disease Control and Prevention noted, “Occupational asthma, acute and chronic bronchitis, and organic dust toxic syndrome can be as high as 30% in factory farm workers.” A recent study was able to detect antibiotic-resistant bacteria in the air downwind from cattle facilities.

While the association with early-life exposure to such an environment and reduced allergies is “pretty strong,” as Jane A. Hoppin, an environmental epidemiologist with the National Institute of Environmental Health Sciences, said in an email, the overall health effects of agricultural work is a complicated area. “Farmers as adults have comparable rates of asthma to non-farmers,” she noted, but the asthma is of a “non-allergic” variety, caused by factors other than documented allergens. Furthermore, chemical exposure may modify any protection that early bacterial exposure has created. Pesticides in particular are “more likely to be associated with allergic asthma,” Hoppin said.

Higher rates of mortality among farmworkers are thanks, in part, to “tuberculosis, cirrhosis of the liver and malignant neoplasms (stomach, biliary passage, liver and gallbladder, and uterine cervix),” Don Villarejo, founder and director emeritus of the California Institute for Rural Studies, wrote in a white paper on health issues among hired farmworkers. Even nonfatal health effects are higher among field workers than among other agricultural employees. “Hired farm workers accounted for 71 percent of acute pesticide poisonings, processing and plant workers for 12 percent, farmers for 3 percent, and other miscellaneous agricultural workers for 19 percent,” Villarejo wrote. Unsurprisingly, farmers themselves often steer clear of potential exposure to pesticides and other chemicals.

Country air may be good for the lungs, but it’s only one aspect of modern agriculture, which puts more than just farm dust into the environment. The allergy-minimizing dust may be more useful off the farm than on it, as there are only so many dairy farms and only so many people living nearby. The study’s authors told The Guardian that they plan to analyze the dust further to find out what the active substance is. The hope is that the active component can be used to develop a vaccine for asthma and a therapy—if not an outright cure—for allergies.