Parkinson's Disease Linked to Cleaning Chemical Exposure
Two common cleaning chemicals have been linked to development of Parkinson’s disease, according to a study published in the Annals of Neurology. Researchers discovered up to a nearly tenfold increased risk of Parkinson’s associated with exposure to trichloroethylene (TCE) and/or perchloroethylene (PERC).
Cleaning solutions may have toxic effects
The chemical solvent TCE is a nonflammable, colorless liquid that is mainly used to remove grease from metal parts, although it also can be found in paint removers, adhesives, and spot removers. Even though TCE does not occur naturally in the environment, it can be found in underground and surface water sources related to the manufacture, use, and disposal of the chemical.
Perchloroethylene also is a nonflammable, colorless liquid, and its primary use is dry cleaning fabrics and degreasing metals. PERC can also be found in aerosol products, printing inks, adhesives, sealants, paint removers, automotive cleaners, polishes, and lubricants.
The new research involved 99 sets of twins (half were identical, half fraternal), in which one of the pair had developed Parkinson’s, a neurodegenerative disease characterized by tremor, stiffness, impaired balance, and slowed movement. Twin studies are effective in testing for environmental influences, and in the case of Parkinson’s disease, fewer than 10% of cases are caused by a single gene mutation, which suggests environmental influences are a contributing factor.
Under direction of Samuel M. Goldman, MD, MPH, and Caroline Tanner, MD, PhD, at the Parkinson’s Institute in Sunnyvale, California, a research team evaluated the twins’ work and hobby activities over their lifetimes, with special emphasis on situations in which they may have been exposed to chemicals previously linked to Parkinson’s disease. The chemicals included TCE, PERC, carbon tetrachloride, n-hexane, xylene, and toluene.
Other risk factors for the disease were also considered, including smoking and head injuries. The evaluators looked only at the data for each twin and did not know which individuals had Parkinson’s disease.
Goldman reported that “Parkinson’s was sixfold more common in twins exposed to TCE, and ninefold more common in twins exposed to TCE or PERC.” Among twins exposed to PERC alone, there was a trend toward a tenfold increase in Parkinson’s disease.
The authors pointed out that there is “a lag time of up to 40 years between TCE exposure and onset of Parkinson’s,” which limits the types of studies investigators can perform in hopes of securing accurate data. They also noted that carbon tetrachloride “tended towards significant risk of developing the disease.”
This study was limited in that the evaluators looked only at the twins’ occupational exposure to the chemicals, yet both TCE and PERC are found outside industrial settings. TCE, for example, is the most often reported organic contaminant in groundwater, while PERC is the main chemical you can find on clothes you have dry cleaned.
TCE can remain in ground water for many years, and it has been identified in more than half of the 1,430 National Priorities List sites named by the Environmental Protection Agency. Drinking or breathing high levels of TCE may damage the liver, lungs, and nervous system, as well as cause abnormal heartbeat, coma, and even death.
The health impact of PERC is similar to that of TCE. PERC has also been listed as “reasonably anticipated to be a human carcinogen” in the Twelfth Report on Carcinogens published by the National Toxicology Program, because long-term exposure can cause leukemia and cancer of the skin, lungs, bladder, colon, urogenital tract, and larynx.
Tanner remarked that while the link between exposure to the cleaning chemicals and Parkinson’s disease appears strong in their study, future work with larger populations is necessary. “It will be important to replicate these results in additional populations with well-characterized exposure histories,” she noted.
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