By: Agata Blaszczak Boxe
Published: 12/11/2015 10:03 AM EST on LiveScience
A pesticide that was present in milk in the early 1980s may be linked to signs of Parkinson’s disease that are showing up in people today, according to a new study.
The researchers looked at Japanese-American men in Hawaii, where the pesticide was frequently used, and found that those who drank more than two cups of milk daily at the start of the study had 40 percent fewer brain cells in an area of the brain called the substantia nigra 30 years later, on average, compared with similar men who drank less than two cups of milk per day.
The loss of brain cells in this area of the brain may be an early sign of Parkinson’s disease, and can start decades before any visible symptoms of the disease occur, the researchers said. The study included men whose average age was 54 at the start of the study.
The link between the higher consumption of milk and the loss of cells in this brain area was not found among the men in the study who had ever smoked cigarettes, the researchers noted. Previous research has shown that people who smoke cigarettes may have a lower risk of developing Parkinson’s disease, the researchers said. [10 Things You Didn’t Know About the Brain]
The researchers also found that residues of the pesticide, called heptachlor epoxide, were present in the brains of 90 percent of the men who drank the most milk, compared with 63 percent of those who did not drink any milk.
High levels of the pesticide were found in the milk supply in the early 1980s in Hawaii, where the chemical was used for insect control in the pineapple industry. The commercial sale of the pesticide in agriculture was banned in the United States by 1988, according to the U.S. Environmental Protection Agency. However, a related compound can still be used today for controlling fire ants in electrical grid machinery, according to the Agency for Toxic Substances & Disease Registry.