A new study, published in the journal Neurology , says that pesticides found in milk in the 1980s could be linked with Parkinson’s disease. The study followed nearly 500 Japanese-American men for over 30 years from the Honolulu-Asia Aging Study. Researchers assessed brain cell loss in a particular area of the brain—the Substantia nigra—which is an indicator of Parkinson’s disease. In addition, they looked at residuals of heptachlor epoxies, a pesticide abundant in the milk supply in the early 1980s, in the brains of 116 study participants. This pesticide was originally used to kill insects affecting the pineapple industry and eventually spread to cow feed and thus cow’s milk.
Since smoking has been linked with a decreased risk for Parkinson’s disease, the study also took smoking status into account. Nonsmokers who had over two cups of milk daily had 40% fewer brain cells in the Substantia nigra region compared to men drinking less than two cups of milk a day. For smokers, milk intake was not tied with decreased brain cells.
High levels of heptachlor epoxide residuals were found in 90% of men who drank the most milk, and in only 63% of those who reported drinking no milk. However, the researchers can’t determine if the milk that participants drank had high levels (or any at all) of the pesticide in question, heptachlor epoxide. This study can only show a possible association between the milk drank in the ’80s and risk of Parkinson’s disease. In fact, “there are several possible explanations for the association, including chance,” said Honglei Chen, MD, PhD, with the National Institute of Environmental Health Sciences and a member of the American Academy of Neurology (not associated with this study), in a corresponding editorial, reports Science Daily.
The US banned the use of the pesticide heptachlor epoxide in 1988 after noting heptachlor’s dangerous effects—meaning, this study doesn’t mean a whole lot for milk consumers today, though it is a reminder to consider environmental toxins and their role in disease.