The USDA recently announced that dust blown from dairy farms is not likely to be hazardous to surrounding communities; however, the USDA cited a 2-year-old study that omitted data from December through March – months when potentially harmful endotoxins in dairy dust are highest, according to a previous study by the same scientists.
The USDA's Agricultural Research Service issued a news release on Dec. 12 titled “Dust from Dairies Not Likely to Pose Hazard to Nearby Communities” that stated “potentially problematic particles are not found at high levels far beyond the barnyard.” The story was widely reported in agricultural publications.
The “problematic particles” in dust are known as bioaerosols and consist of endotoxins, bacteria and fungi. They can cause both short-term and long-term health problems such as pneumonia symptoms, asthma symptoms, organic dust toxicity syndrome, and farmer’s lung. Farmer's lung is so much more prevalent in winter than any other time of year that some medical doctors define it as a disease of farmers who handle contaminated hay during the winter months.
The USDA cited data from a study of bioaerosols in fall, spring and summer that originally was published online in the Journal of Animal Science in May 2011. That study measured both total endotoxin concentrations in air and “inhalable” concentrations – particulate matter small enough to be “particularly hazardous when deposited anywhere in the respiratory tract because it can cause respiratory disease, discomfort, and increased mortality.”
During fall, spring and summer, the study found an average of 56 inhalable endotoxin units (EUs) and 68 total EUs per cubic meter of air 655 feet downwind (a length of more than two football fields) of a 10,000-cow open-freestall dairy in southern Idaho. The scientists who conducted the study are R. S. Dungan, A. B. Leytem and D. L. Bjorneberg, all with the USDA's Agricultural Research Service.
In an earlier 12-month study published online in Aerobiologia in December 2009, the same scientists took measurements 655 feet downwind of a 10,000-cow open lot dairy farm, also in southern Idaho. The total endotoxin concentrations from December through March ranged from 21 to 261 EUs per cubic meter of air, with an average of 107 EUs. The range for other months was lower, and the average for the entire year was 72 EUs.
“It is well established that airborne endotoxin concentrations as low as 50 EU m-3 can cause acute respiratory effects. In this study, total airborne endotoxin concentrations often exceeded this value at the upwind and downwind sites throughout the year,” the scientists concluded in the 12-month study.
The United States does not yet regulate how much endotoxin an agricultural worker can inhale under workplace safety rules, although other countries have considered maximum exposure limits starting as low as 50 EU's per cubic meter of air.
Farm workers and neighboring property owners alike have become concerned about possible health effects of bioaerosols due to the increasing industrialization of dairies. “High stocking densities at animal feedlots have drastically changed modern agricultural practices,” the scientists noted in the 2009 study, and said the trend is happening not just in Idaho but in other states and countries. Suburban development has also encroached on farming regions.
The number of dairies has declined from about 650,000 in 1970 to fewer than 100,000 today, per USDA statistics, while the average herd size has increased fivefold. All 50 states produce milk, but in 2011 the top 10 were California, Wisconsin, Idaho, New York, Pennsylvania, Texas, Minnesota, Michigan, New Mexico and Washington.
The studies said wind was a factor in blowing endotoxins farther away from farms. Maps of potential wind farms show that many of the same states with enough sustained winds for wind power are located in the Midwest and West Coast where lots of dairy operations are located.
“In the western United States, dairy cows are kept in large outdoor pens or in a combination of exercise pens and barns at open-freestall facilities. Either way, people can sometimes smell dairies before they can see them, so they assume there’s a problem,” Dungan stated in an article in the November/December 2013 issue of Agricultural Research magazine.
Although Dungan gave the results from the studies a positive spin, saying “people who live near these facilities can hopefully breathe a sigh of relief about potential bioaerosol exposures,” he and his fellow researchers were more cautious in the conclusion of the study published in the Journal of Animal Science. “Because only two dairies have been investigated by our group to date, it should be cautioned that the observed spatial trends and bioaerosol concentrations may not be representative of the whole dairy industry,” they wrote.
It is possible that as more studies reveal data about endotoxin levels and potential health hazards, new laws will soon establish maximum exposure limits to endotoxins in agricultural dust, or regulate how close farms can be to neighboring residential communities, or specify criteria for dairy facilities and methods of lot management to reduce dairy dust. Regulations protecting agricultural workers may also increase, since bioaerosol concentrations are much higher on the farms than downwind.
As dairy farms become more industrialized, it is clear that the concern over bioaerosols in dairy dust cannot be swept under a rug.
Dayna J. Sondervan is an attorney based in Atlanta, Georgia and can be reached at dayna.sondervan@gmail.com. As an attorney since 1994 and a former Vice President & General Counsel of a company, she has experience in a wide range of legal issues that confront businesses. She also has served on a Georgia Senate Lien Law Study Committee helping to draft new lien legislation, and she has been admitted to practice before the Supreme Court of the United States. Ms. Sondervan’s articles are for general information only and subject to editing, and readers should consult an attorney for legal advice about current laws and options that apply to their situation.