A pesticide found at very high levels in Hawaii’s milk supplies in the 1980s has been linked to a higher risk of developing Parkinson's disease, a study concludes.
A team of researchers focused on an environmental scandal in Hawaii to study the association between the pesticide and Parkinson’s: In 1982, tests showed Hawaii milk supplies had abnormally high levels of heptachlor epoxide, an organochlorine pesticide commonly used on pineapples.
Milk was pulled from store shelves and from schools, and residents scrambled to find limited supplies of safe milk. Officials later determined that the pesticide made its way into the milk supply when cows were fed a gruel made in part by pineapple debris.
Reporting in the online journal Neurology, a team of scientists led by Robert Abbott, of the Shiga University of Medical, wanted to see what the effects of heptachlor were on regular milk drinkers.
They studied the brains of men who were middle-aged around the time of the heptachlor crisis, and narrowed their research to focus on men who reported drinking more than two glasses of milk a day.
For the study, they used the brains of Japanese-American men, with an average age of 54, who participated in the Honolulu-Asia Aging Study for more than 30 years until death.
The brains of men who reported being regular milk drinkers showed the thinnest nerve networks in areas known to be affected by Parkinson’s, which suggests those areas were compromised.
Meanwhile, residues of heptachlor epoxide were found in 90 percent of men who drank the most milk, compared to 63 percent of those who didn’t drink milk.
Abbott and his team didn’t have samples of milk the men drink, so they can’t be absolutely sure that the contaminated milk was the source of the pesticides found in the men’s brains.
“We don’t have all the data yet, but we are close to find the smoking gun here,” he told TIME magazine. “It’s not complete but it’s very suspicious.”
Heptachlor is no longer used as an insecticide in the United States.
Exposure to large concentrations of heptachlor can cause liver and kidney damage, along with other problems.
Dairy cattle had been fed the tops of pineapples, known as green chop, for years before officials found highe concentrations of heptachlor in milk -- at the time, health officials said heptachlor in milk was three to six times acceptable levels.
The crisis in Hawaii led to a backlash against local dairies, which had previously supplied all of Hawaii's milk. Residents switched to powdered and evaporated milk; Safeway was the first to import processed milk into the marketplace in 1984, according to the state Department of Agriculture.
The study’s authors say their findings shouldn’t deter people from drinking milk. But, they say, the report can be added to growing body of work that shows lifestyle contributes to Parkinson’s risk.
The study was published online Thursday by Neurology, the journal of the American Academy of Neurology.