Trichloroethylene (TCE) is a common industrial solvent mostly used for metal degreasing. Due to its wide use in industries, there have been several incidences of waste TCE leaking into aquifers and contaminating groundwaters.
Due to their similar industrial uses, areas contaminated with mainly TCE may also be contaminated with tetrachloroethylene in smaller amounts.
The first known report of TCE in groundwater was given in 1949 by two English public chemists who described two separate instances of well contamination by industrial releases of TCE. [1]
Exposure to TCE occurs mainly through contaminated drinking water. With a specific gravity greater than 1 (denser than water), trichloroethylene can be present as a dense non-aqueous phase liquid (DNAPL) if sufficient quantities are introduced into the environment. Another significant source of vapor exposure in Superfund sites that has contaminated groundwater, such as at the Twin Cities Army Ammunition Plant, was by showering. TCE readily volatilizes out of hot water and into the air. Long, hot showers would then volatilize more TCE into the air. In a home closed tightly to conserve the cost of heating and cooling, these vapors would then recirculate. Based on available federal and state surveys, between 9% and 34% of the drinking water supply sources tested in the U.S. may have some TCE contamination, though EPA has reported that most water supplies are in compliance with the maximum contaminant level (MCL) of 5 ppb. [2]
In addition, a growing concern in recent years at sites with TCE contamination in soil or groundwater has been vapor intrusion in buildings, which has resulted in indoor air exposures, such is in a recent case in the McCook Field neighborhood of Dayton, Ohio, United States. [3] Trichloroethylene has been detected in 852 Superfund sites across the United States, [4] according to the Agency for Toxic Substances and Disease Registry (ATSDR). Under the Safe Drinking Water Act of 1974, and as amended [5] annual water quality testing is required for all public drinking water distributors. The EPA'S current guidelines for TCE are online. [6]
The EPA's table of "TCE Releases to Ground" is dated 1987 to 1993, thereby omitting one of the largest Superfund cleanup sites in the nation, the North IBW in Scottsdale, Arizona. Earlier, TCE was dumped here, and was subsequently detected in the municipal drinking water wells in 1982, prior to the study period. [7]
Marine Corps Base Camp Lejeune [8] in North Carolina may be the largest TCE contamination site in the United States. Legislation could force the EPA to establish a health advisory and a national public drinking water regulation to limit trichloroethylene. [9]
The 1998 film A Civil Action dramatizes the EPA lawsuit Anne Anderson, et al., v. Cryovac, Inc. concerning trichloroethylene contamination that occurred in Woburn, Massachusetts in the 1970s and 1980s.
Until recent years, the US Agency for Toxic Substances and Disease Registry (ATSDR) contended that trichloroethylene had little-to-no carcinogenic potential, and was probably a co-carcinogen—that is, it acted in concert with other substances to promote the formation of tumors.
In 2023, the United States EPA determined that trichloroethylene presents an unreasonable risk of injury to human health under 52 out of 54 conditions of use, including during manufacturing, processing, mixing, recycling, vapor degreasing, as a lubricant, adhesive, sealant, cleaning product, and spray. It is dangerous from both inhalation and dermal exposure and was most strongly associated with immunosuppressive effects for acute exposure, as well as autoimmune effects for chronic exposures. [33]
As of June 1, 2023, two U.S. states (Minnesota and New York) have acted on the EPA's findings and banned trichloroethylene in all cases but research and development. [34] [35]
In 2001, a draft report of the Environmental Protection Agency (EPA) laid the groundwork for tough new standards to limit public exposure to trichloroethylene. The assessment set off a fight between the EPA and the Department of Defense (DoD), the Department of Energy, and NASA, who appealed directly to the White House. They argued that the EPA had produced junk science, its assumptions were badly flawed, and that evidence exonerating the chemical was ignored.[ citation needed ]
The DoD has about 1,400 military properties nationwide that are contaminated with trichloroethylene. Many of these sites are detailed and updated by www.cpeo.org and include a former ammunition plant in the Twin Cities area. [36] Twenty three sites in the Energy Department's nuclear weapons complex—including Lawrence Livermore National Laboratory in the San Francisco Bay area, and NASA centers, including the Jet Propulsion Laboratory in La Cañada Flintridge are reported to have TCE contamination.
Political appointees in the EPA sided with the Pentagon and agreed to pull back the risk assessment. In 2004, the National Academy of Sciences was given a $680,000 contract to study the matter, releasing its report in the summer of 2006. The report has raised more concerns about the health effects of TCE.
In the European Union, the Scientific Committee on Occupational Exposure Limit Values (SCOEL) recommends an exposure limit for workers exposed to trichloroethylene of 10 ppm (54.7 mg/m3) for 8-hour TWA and of 30 ppm (164.1 mg/m3) for STEL (15 minutes). [37]
Existing EU legislation aimed at protection of workers against risks to their health (including Chemical Agents Directive 98/24/EC [38] and Carcinogens Directive 2004/37/EC [39] ) currently do not impose binding minimum requirements for controlling risks to workers health during the use phase or throughout the life cycle of trichloroethylene. However, in case the ongoing discussions under the Carcinogens Directive will result in setting of a binding Occupational Exposure Limit for trichloroethylene for protection of workers; this conclusion may be revisited.
The Solvents Emissions Directive 1999/13/EC [40] and Industrial Emissions Directive 2010/75/EC [41] impose binding minimum requirements for emissions of trichloroethylene to the environment for certain activities, including surface cleaning. However, the activities with solvent consumption below a specified threshold are not covered by these minimum requirements.
According to European regulation, the use of trichloroethylene is prohibited for individuals at a concentration greater than 0.1%. In industry, trichloroethylene should be substituted before April 21, 2016 (unless an exemption is requested before October 21, 2014) [42] by other products such as tetrachloroethylene (perchloroethylene), methylene chloride (dichloromethane), or other hydrocarbon derivatives (ketones, alcohols, ...).
The use of TCE in the U.S. peaked around 1970, then declined significantly due to regulatory and economic factors. [43] As a result, 1,1,1-trichloroethane (TCA) became a common substitute in metal degreasing and cleaning applications. [43] However, alternatives to chlorinated aliphatic hydrocarbons have since proliferated, as many of these compounds have been phased out across industries due to their health risks and the associated legal liabilities.
The U.S. military has virtually eliminated its use of the chemical, allegedly purchasing only 11 gallons in 2005. [44] : 4 About 100 tons of it was used annually in the U.S. as of 2006. [44] : 5