The study of 990 Parkinson’s patients, published in the official journal of the American Academy of Neurology, found that those who had been exposed to hydrocarbon solvents were on average three years younger when they first showed symptoms. The solvents are found in common petroleum-based products such as paints and glues, and the severity of the disease was found to be directly linked to the duration and intensity of exposure to them.

“These findings raise serious questions about specific occupational risk,” said study author, Dr Gianni Pezzoli of the Parkinson Institute in Milan. “This study more than merits further investigation into job-related Parkinson’s risk factors.”

Researchers identified nine occupations which accounted for more than 91% of the hydrocarbon solvent exposure, the most common being in the petroleum, plastic and rubber industries. Other occupations found to have frequent solvent exposure were painters, engine mechanics and lithographers.

Assuming that the research paper proved that hydrocarbons cause Parkinson’s Disease, then one would be able to speculate that the effect on the nervous system, or on cells in general, was caused by metabolising hydrocarbons producing free radicals, Robert G Feldman MD, spokesman for the American Academy of Neurology, and Professor of Neurology, Pharmacology and Environmental Health at Boston University, told edie. These charged ions would produce intracellular damage, decreasing the cell function and eventually killing them.

However, not all people exposed to hydrocarbons develop Parkinson’s disease, points out Feldman. This makes it more likely that the disease is caused by a combination of genetic susceptibility and exposure to various substances, says Feldman. As well as solvents, other possible causes of Parkinson’s which are being investigated include exposure to lead, manganese, iron and pesticides.

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