A U.S. study linked Parkinson's disease to the industrial solvent trichloroethylene (TCE).

Researchers, led by Dr. Samuel Goldman and Dr. Caroline Tanner of The Parkinson's Institute in Sunnyvale, Calif., interviewed 99 pairs of twins. In each pair, one twin had Parkinson's disease and the other did not.

The study, published Monday, found that individuals regularly exposed to TCE, a common agent in dry-cleaning solutions, adhesives, paints and carpet cleaners, had six times the risk of developing Parkinson's disease.

Although the US Food and Drug Administration banned the use of TCE as a general anesthetic, skin disinfectant, and coffee decaffeinating agent in 1977, it is still widely used as a degreasing agent.

The study was the first to report a "significant association" between the solvent and Parkinson's disease.

As a result of the investigation, the researchers also judged that exposure to the solvents perchloroethylene and carbon tetrachloride "tended towards significant risk of developing the disease."

"Our study confirms that common environmental contaminants may increase the risk of developing PD [Parkinson's disease], which has considerable public-health implications," Goldman said. "Our findings, as well as prior case reports, suggest a lag time of up to 40 years between TCE exposure and onset of PD, providing a critical window of opportunity to potentially slow the disease process before clinical symptoms appear."

The National Institute of Neurological Disorders and Stroke (NINDS) estimates that as many as 500,000 Americans have Parkinson's disease, while over 50,000 new cases are diagnosed annually in the US. The disease causes limb tremors, slowed movement, muscle stiffness and speech impairment.

The study was published in the Annals of Neurology journal.