Results from a recent study examining what’s in organic versus conventional milk show that the majority of samples of conventional, non-organic milk tested positive for certain low, chronic levels of pesticides, illegal antibiotics and growth hormones. The organic samples tested at either much lower or non-existent rates in comparison. “To our knowledge, the present study is the first study to compare levels of pesticide in the U.S. milk supply by production method (conventional vs. organic),” the researchers noted. “It is also the first in a decade to measure antibiotic and hormone levels and compare them by milk production type.” However, an expert reviewing the study at USA TODAY’s request expressed caution at overinterpreting the results. The study, conducted by Emory University in Atlanta was funded by Washington, D.C.-based nonprofit research organization The Organic Center and looked at a total of 69 samples of conventional and organic milks pulled from retail stores around the U.S., which were then shipped overnight to Georgia to be analyzed. The results have been published online June 26 by peer-reviewed journal Public Health Nutrition.
Pesticide residues were found in up to 60% of conventional samples and none of the organic samples. Those included atrazine (26%), chlorpyrifos (59%), cypermethrin(49%), diazinon (60%), and permethrin (46%). “To what impact these chemicals that we’re seeing in the supply are having, we don’t know,” said Jean Welsh, a nutritional epidemiologist who proposed the Emory study, noting that, “this study wasn’t designed to look at that.” Jessica Shade, director of science programs for The Organic Center said, “This study finds that the presence of antibiotics and pesticides in conventional milk is much more prevalent and pervasive than previously thought.” The Organic Center operates with oversight from the Organic Trade Association, an organization focused on promoting the organic business community. OTA members include a range of businesses from small organic farmers and mom-and-pop operations to brands like Pure Organics, Moodbeli and Horizon Organic and retailers such as Whole Foods. The presence of these antibiotics in conventional milk, however, isn’t necessarily a sign of illegal antibiotic use. They’re illegal only for use in cows producing milk, meaning calves can be administered doses of sulfonamide drugs to treat bacterial diseases, as long as they’re under 20 months old, says Jamie Jonker, a vice president for the National Milk Producers Federation. Any positive test results for sulfonamides could be the result of leftover antibiotics from that time or intentional misuse, Jonker said.
When it comes to the question of hormones in milk, cow-derived hormones were found in both conventional and organic samples. The difference was in how much. The study said the dramatic difference suggests “the use of synthetic growth hormones,” but Welsh said that there currently isn’t a research method to differentiate which hormones are naturally or synthetically produced. Synthetically produced bGH has not been shown to have adverse health effects on either humans or cows, according to a 2014 study published in the Journal of Animal Science by Cornell University’s Dale Bauman and the University of Arizona’s Robert Collier. Cows supplemented with bGH have been shown to produce nutrients and milk more efficiently. One pesticide on the list, chlorpyrifos, has recently been in California’s crosshairs, with plans to ban it announced in May. It’s used on row crops such as corn, soybeans, fruit and nut trees, Brussels sprouts, cranberries, broccoli, and cauliflower, as well as on non-agricultural spaces such as golf courses, according to the Environmental Protection Agency. Again, the use of hormones and pesticides is off limits for organic farmers. That said, some banned legacy pesticides were found in nearly all samples of both organic and conventional milk, the study showed, as they remain “persistent, at very low background levels in the environment.” Levels in the conventional milk again surpassed what was found in the organic samples. “Traces of these legacy pesticides persistently show up in any test for residues, so we were not surprised that they were detectable in both organic and conventional milk,” Shade said.