Health and Environment
Particularly large exposures, primarily via inhalation, may occur when workers clean metal parts in a vapor degreaser.
TCE is reported by the EPA to be the most prevalent solvent contaminating groundwater at superfund sites in the United States. The general public may be exposed to TCE by drinking, breathing or bathing in contaminated water. The third National Health and Nutrition Examination Survey suggested that approximately 10% of the population had detectable levels of TCE in their blood.
Human Health Effects
Acute (short-term) exposure to TCE vapors can cause central nervous system (CNS) effects (e.g., light-headedness, drowsiness, headache and giddiness) and may lead to unconsciousness or be fatal. At very high exposure levels, TCE can sensitize the heart to the effects of adrenaline and similar agents, which may lead to sudden cardiac arrest. In addition, TCE may irritate the respiratory tract at high vapor concentrations, and may be lethal at concentrations exceeding 1000 ppm.
Repeated or prolonged contact with the chemical in liquid or mist form can cause irritation of the skin and eyes. Direct exposure to liquid TCE defats the skin, causing redness, blistering and scaling.
Frequent, prolonged exposures to organic solvents in general can have long-lasting and possibly permanent effects on the nervous system. Chronic exposure to TCE in excess of recommended occupational limits has been associated with damage to the liver and kidneys, although this is less well documented in humans than in animals
People who drink water containing TCE over many years could experience liver problems and may have an increased risk of developing liver cancer. TCE also has genotoxic and immunotoxic potential, and some studies indicate that it may be a teratogen.
Several agencies have investigated TCE’s association with cancer. The US National Toxicology Program classifies TCE as “reasonably anticipated to be human carcinogen”. The International Agency for Research on Cancer (IARC) lists TCE as Group 2A, probable human carcinogen.
Evidence from animal and epidemiologic studies suggests that several reproductive and developmental toxicity end points may be associated with TCE exposure, including infertility in males and females, impaired fetal growth, and cardiac teratogenesis. The US Agency for Toxic Substance and Disease Registry Public Health Statement for TCE, however, does not conclude that there is a direct relationship between exposure to TCE and an increased risk of reproductive effects.
TCE most often enters the environment via fugitive emissions from metal degreasing industries and by spills or accidental releases to air, soil and water. Because of its high vapor pressure and low rate of adsorption in soil TCE evaporates fairly rapidly when released to soil. However, where it persists it can percolate rapidly through sandy soil thereby reaching groundwater.
Chemical and biological degradation of TCE in water are expected to be very slow. TCE is not expected to accumulate in aquatic organisms or to adsorb onto sediment; however it is toxic to aquatic organisms.
When released to the atmosphere, TCE remains in the vapor phase. Once in the air about half of the TCE will break down within a week. When TCE is broken down in the air, phosgene, a significant lung irritant, can be formed. In the body, TCE may break down into dichloroacetic acid, trichloroacetic acid, chloral hydrate, and 2-chloroacetaldehyde. These byproducts have been shown to be toxic to animals and may be toxic to humans.
Endnotes: U.S Department of Health and Human Services, Household Products Database. Chemical Information, Trichloroethylene, 2008, and Third National Health and Nutrition Examination Survey (NHANES III, 1988-1994): Multiply Imputed Data Set, 2001; National Toxicology Program, 11th Report on Carcinogens: Trichloroethylene; ATSDR, Public Health Statement for Trichloroethylene; Toxicology Data Network Hazardous Substances Data Bank, Trichloroethylene; ATSDR, Medical Management Guidelines for Trichloroethylene; California Department of Health Services Hazard Evaluation System and Information Service, Fact Sheet: Trichloroethylene; US EPA, Ground Water & Drinking Water Consumer Factsheet on: Trichloroethylene; National Academy Press, Assessing the Human Health Risks of Trichloroethylene: Key Scientific Issues, 2006; US EPA Technology Transfer Network Air Toxics Website. Trichloroethylene; Toxics Use Reduction Institute, Policy Analysis, Higher Hazard Substance Designation Recommendation: Trichloroethylene; Ichihara, et al. Neurological Disorders in Three Workers Exposed to 1-Bromopropane, 2002.