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Industrial solvent linked to increased risk of Parkinson's disease

February 7, 2010 |  4:13 pm

Exposure to the industrial solvent trichloroethylene increases a person's risk of developing Parkinson's disease nearly sixfold, California researchers said Sunday. Animal studies had suggested a potential problem with the solvent, but the new study by Dr. Samuel Goldman of the Parkinson's Institute in Sunnyvale is the first to quantify the risk.

Parkinson's disease, caused by the death of cells in the brain that secrete the neurotransmitter dopamine, is characterized by severe tremors, rigidity in the limbs and other symptoms. It strikes an estimated 100,000 Americans each year and is ultimately fatal. Genetics play a role in susceptibility to Parkinson's, but it has also been linked to head trauma, pesticides and illicit drugs.

Trichloroethylene, or TCE, is a solvent that was once widely used in dry cleaning and to clean grease off metal parts, and it was once used as an anesthetic, especially during childbirth. But concerns about its toxicity led to it being mostly abandoned and replaced by other anesthetics and solvents. There have been at least three reports of clusters of Parkinson's among workers exposed to TCE. Animal experiments following those reports showed that the chemical kills dopamine-producing cells in substantia nigra, the part of the brain affected in Parkinson's disease. It also impairs mitochondria -- the power sources of brain and other cells -- in the same locations that are affected by the illicit chemical MTPT, which is known to cause Parkinson's. "There's a lot of circumstantial evidence to show that it is relevant," Goldman said in an interview.

Goldman and his colleagues identified 99 sets of twins from the World War II Veteran Twins Cohort in which one twin had Parkinson's and the other didn't. They collected job histories for each subject and then had them analyzed blindly by an industrial hygienist and a preventive medicine specialist to assess exposure to occupational chemicals.

Goldman and his team found that exposure to the chemicals xylene, toluene and n-hexane was not associated with an increased risk of Parkinson's. Those exposed to TCE, however, were 5.5 times as likely to develop the disease as those who were not exposed. Those exposed to either TCE or tetrachloroethylene, known as PERC, had eight times the risk. Those exposed to carbon tetrachloride had 2.8 times the risk, and those exposed to PERC had nine times the risk; in both cases, however, the results fell short of statistical significance.

"Part of the problem is that the usage of the substances overlaps quite a bit," he said. Nonetheless, the "very high odds ratio" for TCE "is impressive, and certainly mandates that large population-based studies follow this up." Goldman will report his findings at a Toronto meeting of the American Academy of Neurology in April.

Those who were exposed to TCE had job histories primarily as dry cleaners, machinists, mechanics or electricians. Because the exposure estimates were not precise, Goldman said, the study needs to be replicated. To begin with, the team is looking at larger databases, and they will most likely try to find cohorts of people with high exposure to the chemicals to see how many have Parkinson's. "I think people will really move on this as quickly as possible now," he concluded.

-- Thomas H. Maugh II

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Comments (6)

This is a great article filled with specifics that can be acted upon. I had a grandfather who had Parkinson,s on my mother's side. He died from it back in 92, I watched him waste away from the disease, but little was known about it and little could be done. I have been concerned about it every since because, it can be inherited. So far he is the only one known to have it. This article has given me more insight than I have ever had about the disease. I will be watching closely for more information and further studies. Thank you so much!

My husband worked in a dry cleaning plant around all those solvents for 32 years. At one point in time, there were questions as to whether those solvents could have attributed to issues he was having at the time. Now , years later, he has been diagnosed with Lewy Body Dementia with parkinson symptoms. Now you have made me think of what other possibilities could have led to his illness. Thank you for the article.

Great. I used to swim in the stuff. Believe it or not thirty years ago they were calling it a "safety solvent" probably because it didn't rot your brain out like methyl ethyl ketone.

Thanks for this informative page.

Would be grateful to know, - can extreme mental stress and psychological trauma lead to perkinsons disease of any kind?

My father owned a drycleaning establishment for over 50 years. when he passed away from Pancreatic Cancer, I swore that there was a correlation between the Cancer & the exposure toPerc. -Of course the doctors discounted that! My mom suffers from Dementia w/ Lewy Bodies & Parkinson symptoms.
She would help out at the store on MANY occassions. In the early years, there was extremely poor ventilation and "Cold/Transfer" systems were used. This is a method where by the "wet" clothes were taken from the Cleaning Machine & hand transferred to the Dryer. I worked in that envirnoment for quite a number of years myself and am extremely concerned about what the future holds for me. If there are any studies that are to be done, I can be reached at: stimman@aol.com

I was diagnosed with PD 3 years ago. 40+ years ago I was in the US Army and worked as a Nuc Weapons Technician. We used TCE on a daily basis as part of our jobs. We worked mainly in unventilated bunkers and bays. I have a service connected disability claim pending with the VA. The VA is denying any responsibility for my PD claiming they can't find anything in my medical records were I complained about the fumes of the chemicals I was exposed to during my time on active duty. Fourty years ago I was 19 years old. Its true I didn't complain when told to wash atom bomb parts or my hands and arms with TCE. I didn't know, and no one told me it was going to cripple me up 40 years later. The VA is also ignoring studies like this as insufficient to establish a link between PD an TCE. I guess their philosopy is if they close their eyes and pretend like it doesn't exist, maybe it won't.



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