Exposure to pesticides and solvents, including common household brands like Roundup, increases a person’s risk of developing Parkinson’s disease, according to a new analysis of more than 100 studies from around the world in the latest edition of Neurology, the medical journal of the American Academy of Neurology.
In their analysis, the researchers reviewed 104 studies that looked at exposure to weed, fungus, rodent or bug killers, and solvents and the risk of developing Parkinson’s disease. Studies that evaluated the proximity of exposure — such as country living, occupation and well-water drinking — were also included.
The researchers found that exposure to bug or weed killers and solvents increased the risk of developing Parkinson’s disease by 33 to 80 percent. In controlled studies, exposure to the weed killer paraquat or the fungicides maneb and mancozeb was associated with two times the risk of developing the disease.
“I think the study is actually a big advance in our research knowledge of the relation between chemical exposures and the basic neurological injuries,” Dr. Arch Carson, associate professor at the University of Texas School of Public Health in Houston, said. “This report is the first to show that there is a positive relationship between not only insecticides and herbicides but also some other solvent chemicals to which many people are exposed and the development of Parkinson’s syndrome.”
“We didn’t study whether the type of exposure, such as whether the compound was inhaled or absorbed through the skin and the method of application, such as spraying or mixing, affected Parkinson’s risk,” study author Emanuele Cereda said. “However, our study suggests that the risk increases in a dose response manner as the length of exposure to these chemicals increases.”
A household threat
Parkinson’s disease is a neurological disorder that is caused by the loss of dopamine-producing brain cells. Dopamine controls movement and other neurological functions, so the death of the dopamine cells causes people to lose control of their motor functions and leads to shaking, balance issue, stiffness and difficulty walking.
According to the National Parkinson Foundation, about 50,000 to 60,000 new cases are diagnosed each year, and the disease has become the 14th leading cause of death in the U.S.
One of the most popular and widely used weed killers, Roundup, has been found to be connected to numerous health issues, including Parkinson’s, infertility and cancer. A Monsanto product, Roundup is largely used by farmers. The main ingredient in the herbicide, “glyphosate,” is sprayed over millions of acres of crops and has been found in food across America.
Glyphosate use has doubled in recent years, and companies like Monsanto say the chemical has been proven to be safe and more environmentally friendly than other chemicals. The Environmental Protection Agency is currently reviewing the use of glyphosate and should announce by 2015 whether or not the use of the chemical should be limited.
Roundup is also commonly used on residential lawns, gardens and golf courses.
Correlation isn’t the same as causation
Previous research has linked numerous health complications ranging from allergies to lower IQ levels to pesticides and solvents, but as the researchers cautioned even in this study, the evidence remains “limited, or at least inconclusive,” due to a lack of definitive agreement between cohort and case-control studies.
Carson was not involved in this latest research but says the findings are limited since other factors such as family history, smoking, exposure to other chemicals and occupation have been strongly linked to the disease.
“It does not provide us in medical practice any clear pathway for the treatment of Parkinson’s disease, or even its prevention,” he said. “We do know there is a significant relationship between various chemical exposures and the development of Parkinson’s disease, as well as a significant relationship with things like family history, smoking, and occupation … but it’s very difficult to put these things into practice except in terms of preventive health, and reducing or eliminating exposures to such suspect materials over time.
“It’s very difficult to put these (risks) into practice except in terms of preventive health, and reducing or eliminating exposures to such suspect materials over time,” Carson said.