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Solvent Exposures and Parkinson’s Disease Risk in Twins

Samuel M Goldman, Patricia J Quinlan, G Webster Ross, Connie Marras, Cheryl Meng, Grace S Bhudhikanok, Kathleen Comyns, Monica Korell, Anabel R Chade, Meike Kasten, Benjamin Priestley, Kelvin L Chou, Hubert H Fernandez, Franca Cambi, J William Langston and Caroline M Tanner.

Annals of Neurology; Published Online: November 14, 2011 (DOI:10.1002/ana.XXX).

Sponsors: This research was supported by NINDS Grants RO1-NS40467 and U10-NS31321, the Michael J. Fox Foundation, Parkinson’s Unity Walk, The Valley Foundation, and James and Sharron Clark.

What we found

  • Risk of Parkinson's disease was increased 6-fold in people who worked with the solvent TCE (trichloroethylene) and 10-fold in those who worked with PERC (perchloroethylene; tetrachloroethylene)
  • Exposure preceded Parkinson's disease onset by 30-40 years

How was the study done

  • We studied 99 pairs of twins in which 1 twin had Parkinson's disease and the other twin didn’t
  • We asked them detailed questions about their jobs and hobbies, focusing on job tasks and materials
  • Experts estimated lifelong exposure to 6 common solvents
  • Exposures were compared in the twins with and without Parkinson's disease

Why this matters

  • All of us are exposed to TCE and PERC in the environment
  • In industry, TCE is used to remove grease from metals and other materials
  • PERC is the leading solvent used in dry-cleaning, and is also used as a degreaser and spot remover
  • People who don’t “work” with TCE have been exposed through its use in dozens of common household products such as spot removers, glues, carpet cleaners and paints.
  • Both TCE and PERC persist in the environment. TCE is the most common organic contaminant in groundwater.
  • Millions of pounds of both solvents are released into the environment each year

Next steps

  • Like all epidemiology studies, our results need to be replicated before we can be certain that TCE and PERC cause Parkinson's disease
  • In our study, exposure preceded Parkinson's disease onset by several decades, suggesting that if we understand the toxic mechanism we can potentially intervene to prevent Parkinson's disease
  • Additional studies in the laboratory could help to explain the toxic effects of TCE and PERC on the brain, hopefully leading to preventive therapies

Additional Information

  • There have been a few “case reports” of Parkinson's disease occurring in people who worked with TCE, but this is the first analytic epidemiology study to link TCE or PERC exposure with Parkinson's disease
    • Ref: Gash et al, Ann Neurol 2008;63:184–192
  • Animal studies also support a biological link between TCE and Parkinson's disease
    • Ref: Liu et al, J Neurochem 2010; 112:773–783

For the article abstract, please click here.

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