The research team found that people living in areas with higher levels of manganese pollution had a 78 percent greater risk of Parkinson's disease than those living in areas free of such pollution.
High levels of copper in the environment increased the risk of Parkinson's disease by 11 percent.
"We're following up with individual patients, examining exposure histories, disease progression and responses to treatments, and if those studies confirm this correlation, we may need to reevaluate the limits we place on environmental discharges of these pollutants," said lead author Allison Wright Willis, MD, assistant professor of neurology at the Washington University School of Medicine.
The comparison, published in "American Journal of Epidemiology," was conducted using Medicare data and industrial discharge reports to the U.S. Environmental Protection Agency.
"Every year since 1988, any factory or other industry that releases more than a predefined amount of any of 650 chemicals into the environment has to report those discharges to the EPA," Dr. Willis says. "We used that data to construct a comparison of areas with high levels of manganese, copper and lead pollution versus areas where there were few or no releases of those elements."
Train rolls past U. S. Steel Corporation’s East Chicago steel plant. (Photo by Mark LLanuza)
Many different industries produced the pollutant emissions in the geographic areas studied.
"There's no one group to blame," says Dr. Willis. "Manganese, copper and lead emissions were reported by industries ranging from food, tobacco and beverages to wood products, furniture, apparel and stone work. Others included producers of electrical and computer equipment, metalworking and chemical facilities and metal mining."
The researchers were surprised when they looked at the socioeconomic status of areas with higher pollutant levels. Instead of being uniformly poor and economically depressed, many are middle-class and upper-income areas.
"These pollutants are everywhere, and I think that strongly emphasizes the need to look into their effects in greater detail," Willis says.
In the United States, at least 500,000 people are believed to suffer from Parkinson's disease, and about 50,000 new cases are reported annually, according to the National Institutes of Health.
Parkinson's Disease is a neurological illness named after Dr. James Parkinson, a London physician who was the first to describe it in 1817.
The gradual loss of cells in a small part of the brain creates a deficiency of the brain signaling chemical dopamine, producing symptoms that may include shaking of hands, slowing down of movement, stiffness, and loss of balance. Other symptoms may include loss of facial expression, reduction in speech volume and clarity, difficulty swallowing, dry skin, constipation, urinary difficulties, and depression.
Because Parkinson's disease is a progressive disorder, these symptoms worsen with time.
Parkinson disease associated with farming and exposure to agricultural chemicals has been reported in numerous studies; but little is known about Parkinson disease risk factors for those living in urban areas.
In their research, Willis and her colleagues focused only on urban areas to avoid pesticides, another group of compounds whose presence in the environment is believed to increase the risk of Parkinson's disease.
Willis and her colleagues then used Medicare data to identify 35,000 Parkinson's patients who were living in the area in which they were diagnosed eight years or more before diagnosis.
When adjusted for age, race, sex, there were 274 new cases of Parkinson's disease per 100,000 people in areas with little or no reported manganese, copper or lead pollution.
In areas with high manganese pollution, that number rose to 489.4, and in areas with high copper levels, it increased to 304.2.
Manganese is a trace element and eating a small amount from food or water is needed to stay healthy. Exposure to excess levels of manganese may occur from breathing air, particularly where manganese is used in manufacturing, and from drinking water and eating food. At high levels, it can cause damage to the brain, according to the federal Agency for Toxic Substances.
Certain occupations like welding or working in a factory where steel is made may increase the chances of being exposed to high levels of manganese, the agency says.
Areas with high lead emissions were not associated with a significant increase in Parkinson's disease. Several earlier studies have associated lead exposure with Parkinson's risk, Willis says, including research that has found increased lead levels in the bones of Parkinson's patients.
Willis speculates that other sources of lead exposure besides industrial emissions - water contamination, for example, or contaminated paint - may have a stronger influence on Parkinson's disease risk.
This study received funding from the National Institute for Environmental Health Sciences, the National Institute of Neurological Disorders and Stroke, the National Institutes of Health, the St. Louis chapter of the American Parkinson Disease Association, the American Parkinson Disease Association, Walter and Connie Donius, and the Robert Renschen Fund.
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