In a small study of milk collected from stores across the United States, researchers from Emory University found traces of current-use pesticides and antibiotics in conventionally produced milk but not in milk produced using organic methods, and that growth hormone levels were higher in the conventional vs. organic milk samples. While most samples were within FDA and EPA limits considered safe for these substances, several samples of conventionally produced milk exceeded FDA limits for a few of the antibiotics tested.

The results were recently published in Public Health Nutrition.

“Milk is a valuable source of important nutrients that are often underconsumed by U.S. children and adults,” says lead author Jean Welsh, PhD, MPH, associate professor of Pediatrics at Emory University School of Medicine.  Therefore, it’s important that consumers are able to drink milk, as advised in dietary guidelines, without concern.

“While more research is needed to understand the health impact, if any, of exposure to the antibiotics, pesticides and growth hormones used by some milk producers, our results suggest that consuming organically produced milk, when possible, will help to minimize any possible impact,” says Welsh.

Dana Boyd Barr, PhD, professor of environmental health at Rollins School of Public Health, is senior author of the paper. Barr is director of a laboratory that studies human exposure to a wide range of chemicals, and has been studying chemical exposure for more than two decades.

“Sufficient exposure to pesticides may lower birth weight, contribute to delayed motor and neurological development, and increase cancer risk,” the authors say. 

They also note the long-time hypothesis that levels of antibiotics in dairy and meat products could lead to antibiotic resistance and hypersensitivity.,

Researchers collected samples from a total of 69 half-gallon milk cartons, 34 organic and 35 conventionally-produced. They tested multiple brands of milk collected from all across the U.S. The majority of samples were of milk with 2% milkfat, the type most commonly consumed by US children.

“To our knowledge, this is the first study in several years to compare levels of pesticides, antibiotics, and growth hormones in milk according to production method (conventional vs organic),” the authors say.

Emory co-authors include: Hayley Braun (pediatrics), Nicole Brown (pharmacology), Caroline Um (epidemiology); Karen Ehret (environmental health), and Janet Figueroa (pediatrics).