Solvent May Boost Parkinson’s Risk | November 21, 2011 Issue - Vol. 89 Issue 47 | Chemical & Engineering News
Volume 89 Issue 47 | p. 8 | News of The Week
Issue Date: November 21, 2011 | Web Date: November 22, 2011

Solvent May Boost Parkinson’s Risk

Epidemiology: Study strengthens link between trichloroethylene exposure and movement disorder
Department: Science & Technology
News Channels: Environmental SCENE
Keywords: Parkinson’s disease, trichloroethylene, dopamine
Liver enzymes catalyze reaction of trichloroethylene (TCE) with tryptamine to form the neurotoxin TaClo.
A reaction scheme showing Trichloroethylene reacting with tryptamine in the presence of a P450 enzyme to for TaClo
Liver enzymes catalyze reaction of trichloroethylene (TCE) with tryptamine to form the neurotoxin TaClo.

A study of Parkinson’s disease in twins shows that long-term occupational exposure to the solvent trichloroethylene (TCE) is associated with a risk of developing the movement disorder that is six times that for unexposed people(Ann. Neurol., DOI: 10.1002/ana.22629).

The investigation, led by Samuel M. Goldman and Caroline M. Tanner at the Parkinson’s Institute, in Sunnyvale, Calif., is the first to nail down in an entire population a long-suspected link between TCE and Parkinson’s disease.

Until now, associations between solvent exposure and Parkinson’s disease had been largely anecdotal. The work “takes an important step” by clearly implicating TCE, says Michael A. Schwarzschild, a neurologist at Harvard Medical School and MassGeneral Institute for Neurodegenerative Disease.

“If these findings could be confirmed in the general population, the public health implications will be considerable,” agrees Honglei Chen, an epidemiologist at the National Institute of Environmental Health Sciences.

The work also bolsters the case for the so-called TaClo hypothesis, which posits that reaction of the amino-acid derivative tryptamine with TCE creates 1-trichloromethyl-1,2,3,4-tetrahydro-β-carboline (TaClo), a neurotoxin that destroys dopamine-producing cells. TaClo structurally resembles other molecules known to induce Parkinson’s symptoms in people and in animal models.

Goldman and Tanner’s team examined the occupations, hobbies, and environments of 99 pairs of twins, in which one twin had Parkinson’s and the other did not. The researchers estimated the twins’ long-term occupational exposure to six organic solvents, including TCE and perchloroethylene (PERC).

The study design allowed the researchers not only to account for genetic factors, but also to reduce other confounding factors, such as household environment, demographics, and education.

Exposure to n-hexane, toluene, and xylene did not appear to increase the risk of developing Parkinson’s, but exposure to TCE multiplied the risk six times. PERC and CCl4 were also associated with increased risk, although it was not statistically significant.

TCE is now ubiquitous in the environment, especially in groundwater. It was recently classified as a human carcinogen by EPA (C&EN, Oct. 3, page 26).

Goldman and Tanner’s group are hoping to expand their studies to larger populations and to be able to quantify exposure doses, Goldman says.

Chemical & Engineering News
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kay bander (November 21, 2011 8:36 PM)
what are the most likely household source culprits in addition to groundwater?
steven wood (February 7, 2012 2:49 PM)
can exposure to trike, have any link atall towards diabetes,seeing that it is linked to auto-immune problems. i was exposed to the vapours of trike for about 5 years whilst degreasing metal objects for painting i became diabetic about 14 years after leaving the the time whilst cleaning out the degreasing tank it not only made you feel high it made your teeth feel strange.any comments appreciated.

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