Scientists believe a ubiquitous environmental contaminant used in household products such as carpet cleaners, shoe polishes, and carpet cleaners might be responsible for the development of neurodegenerative movement disorders such as Parkinson’s disease (PD). Parkinson’s disease is already one of the fastest-growing neurological disorders globally, with developing nations reporting an increase of over 30% in the last ten years. The number expects to double again in the next 25 years. Currently, most cases of Parkinson’s disease are diagnosed as idiopathic (no known cause), and population aging is the main reason case numbers are rising, but some leading neurologists have proposed that exposure to a widely used organic solvent known as Trichloroethylene (TCE) may be one contributing factor.
What is TCE (Trichloroethylene) used for?
Trichloroethylene is a halogenated hydrocarbon (halocarbons). These hydrocarbon compounds have at least one hydrogen atom replaced by a halogen atom, such as chlorine, fluorine, or bromine. Emil Fischer first synthesized TCE in 1864, and over the last 100 years, the chemical has had much industrial usage. Due to its age and widespread use, tce chemistry is one of the most severe environmental contaminants. TCE is classified as carcinogenic to humans, with the strongest evidence for kidney cancer and more limited evidence for non-Hodgkin lymphoma and liver cancer, while links with other cancers, such as pancreas cancer and prostate cancer, have not been established. TCE is also shown to damage fetal cardiac development and cause neurotoxicity.[1] Trichloroethylene exposure has been linked in epidemiological studies to a higher risk of Parkinson’s disease, and possible links with other common neurodegenerative disorders are being studied, with limited evidence for ALS, the most common form of MND, and no established link with Alzheimer’s disease.
However, there is still some variance across multiple epidemiological studies assessing TCE-related exposure and risk for developing PD. Also, there is still a degree of uncertainty about how Trichloroethylene causes toxicity to neurons, prevent neurogenesis and damage the dopaminergic system.[2]
The most apparent evidence for the risk of Trichloroethylene to humans has been derived from industrial workers exposed to the chemicals in a workplace setting. An earlier report in the Annals of Neurology found that Trichloroethylene is “a risk factor for Parkinsonism.” A 2012 study of twins in the same journal later found that occupational or hobby exposure to TCE was associated with about a sixfold higher risk of Parkinson’s disease, although the study was small and the estimate is imprecise.
These studies suggest that widely used environmental contaminants may increase the risk of developing Parkinson’s or other neurodegenerative disorders and could pose a considerable risk to public health. An advisory board to the US Department of Labor has also issued a recommendation for workers’ compensation claims, stating that: “The Board recommends exposures to carbon disulfide (CS2) and trichloroethylene (TCE) be presumed to cause, contribute, or aggravate Parkinsonism.”
Does Trichloroethylene cause cancer?
Trichloroethylene is classified as carcinogenic to humans, with the strongest evidence for kidney cancer (renal cell carcinoma) and more limited evidence for non-Hodgkin lymphoma and liver cancer, while links with other cancers, such as lung cancer, have not been established. Exposure has also been linked to non-cancer effects, including autoimmune diseases, fetal heart defects and mitochondrial damage in nerve cells. A possible link with Parkinson’s disease can be easy to overlook because exposure to TCE may happen decades before symptoms appear. High short-term exposure can cause immediate effects such as dizziness, headache and confusion, while many people may unknowingly live or work in contaminated areas for much of their adult lives before any Parkinson’s symptoms develop.
Patients living in sites already known to be contaminated with hazardous materials such as TCE are especially at high risk of exposure. Some countries such as Canada already heavily regulate TCE, and the chemical is also banned in the EU without special permits. It is estimated that over 1 Billion pounds of toxic chemicals are still used annually around the world. In 2018, more than 120 Million pounds of TCE were released into the environment, mainly from industrial sites, which contaminate soil, water, and air. It is estimated that trichloroethylene products can be found in over 25% of groundwater in developed nations, with that number possibly doubling for developing nations.
In the United States, EPA regulations considered a maximum concentration of five parts per billion to be “safe” for TCE in drinking water. In severe contamination cases, such as the contaminated water supply at the Camp Lejeune military base in the United States, residents and workers were exposed to levels far above accepted safety standards, and exposure during pregnancy has been studied for links to birth defects and infant deaths. Researchers do not believe that low concentrations of TCE in drinking water are enough to cause Parkinson’s or severe illness. Still, studies have found an association between drinking private well water and a higher risk of Parkinson’s disease, and pesticides such as the herbicide paraquat, a weedkiller still used in some countries, have also been linked to Parkinson’s risk.[3]
How can we prevent exposure to Trichloroethylene?
A straightforward way to avoid exposure is using activated carbon filtration water devices which can help significantly reduce TCE chemicals in drinking water. If your water comes from a private well near a known contaminated site, have it tested, and if TCE is found, a whole-house treatment system can reduce exposure from showering and bathing as well as drinking. Vapors that rise from contaminated soil or groundwater into buildings need separate measures, such as a sub-slab ventilation system, which local environmental agencies can advise on. Policymakers and doctors around the world are asking for more effective government involvement in testing, proactive monitoring, and remediation of TCE-contaminated sites. Raising awareness of Trichloroethylene will also help many people avoid potentially fatal practices. Failure to address this issue will continue to make matters worse and negatively affect millions of people’s health.
Published Clinical Citations
[1] ^De Miranda BR , Greenamyre JT . Trichloroethylene, a ubiquitous environmental contaminant in the risk for Parkinson’s disease. Environ Sci Process Impacts. 2020 Mar 1;22(3):543-554. doi: 10.1039/c9em00578a. Epub 2020 Jan 30. PMID: 31996877; PMCID: PMC7941732.https://pubmed.ncbi.nlm.nih.gov/31996877/
[2] ^ Liu, M., Shin, E. J., Dang, D. K., Jin, C. H., Lee, P. H., Jeong, J. H., Park, S. J., Kim, Y. S., Xing, B., Xin, T., Bing, G., & Kim, H. C. (2018). Trichloroethylene and Parkinson’s Disease: Risk Assessment. Molecular neurobiology, 55(7), 6201–6214. https://doi.org/10.1007/s12035-017-0830-x
[3] ^ Singthong S, Pakkong P, Choosang K, Wongsanit S. Occupational health risks among trichloroethylene-exposed workers in a clock manufacturing factory. Glob J Health Sci. 2014 Aug 22;7(1):161-72. doi: 10.5539/gjhs.v7n1p161. PMID: 25560356; PMCID: PMC4796495 https://pubmed.ncbi.nlm.nih.gov/25560356/.
