Trichloroethylene, a ubiquitous environmental contaminant in the risk for Parkinson's disease

Abstract

Organic solvents are common chemicals used in industry throughout the world, however, there is evidence for adverse health effects from exposure to these compounds. Trichloroethylene (TCE) is a halogenated solvent that has been used as a degreasing agent since the early 20^th century. Due to its widespread use, TCE remains one of the most significant environmental contaminants in the US, and extensive research suggests TCE is a causative factor in a number of diseases, including cancer, fetal cardiac development, and neurotoxicity. TCE has also been implicated as a possible risk factor in the development of the most common neurodegenerative movement disorder, Parkinson's disease (PD). However, there is variable concordance across multiple occupational epidemiological studies assessing TCE (or solvent) exposure and risk for PD. In addition, there remains a degree of uncertainty about how TCE elicits toxicity to the dopaminergic system. To this end, we review the specific neurotoxic mechanisms of TCE in the context of selective vulnerability of dopaminergic neurons. In addition, we consider the complexity of combined risk factors that ultimately contribute to neurodegeneration and discuss the limitations of single-factor exposure assessments.

Fig. 1

Environmental sources of trichloroethylene (TCE). TCE is predominantly released into the environment via air emissions from industrial sites (1), however, TCE waste may also contaminate groundwater and soil. TCE travels through groundwater or sewer systems in non-aqueous plumes, therefore individuals who live or work near areas of high TCE contamination may be exposed through drinking water (2), or vapor intrusion (3). Figures were created with Biorender.com.