Trichloroethylene (TCE) is a manufactured chemical widely used in industrial processes. This colorless liquid has been used for its effective solvent properties. However, its widespread application has led to significant environmental and health concerns. This article discusses TCE’s characteristics, uses, health and environmental impacts, and management strategies.
Understanding Trichloroethylene
TCE is an organic compound classified as a chlorinated hydrocarbon, meaning its molecular structure includes chlorine atoms. It is a clear, colorless liquid at room temperature with a distinctive sweet, chloroform-like odor. It readily evaporates into the air and is considered non-flammable.
TCE is denser than water and only sparingly soluble in it, which influences its environmental behavior. These characteristics make TCE useful for certain applications but also contribute to its persistence and movement in the environment.
Where TCE is Found
Historically, TCE’s primary application was as a solvent for degreasing metal parts in industries like aerospace, automotive, and household appliance production. It was valued for its efficiency in cleaning oils and greases. TCE also served as a solvent in the dry-cleaning industry, removing stains from fabrics.
Beyond these uses, TCE has been an ingredient in many commercial and consumer products, including adhesives, paint removers, spot removers, carpet-cleaning fluids, and typewriter correction fluid. Its presence in the environment today is largely due to past industrial discharges, improper disposal, and leaking storage tanks and pipelines.
Impacts on Health and Environment
Exposure to TCE can occur through inhalation of its vapors, ingestion of contaminated water or food, and skin contact. Workers in industries using TCE and individuals near contaminated sites face exposure risks. TCE can evaporate from contaminated soil and groundwater, leading to vapor intrusion into indoor air, even in residential buildings.
The health effects from TCE exposure vary by amount, duration, and route. Short-term inhalation of high levels can affect the central nervous system, causing headaches, dizziness, drowsiness, and impaired coordination. Severe acute exposures can lead to unconsciousness or death.
Long-term or repeated exposure to TCE is associated with serious health issues, including liver and kidney damage. The U.S. Environmental Protection Agency (EPA) classifies TCE as “carcinogenic to humans by all routes of exposure,” with strong evidence linking it to kidney cancer. Associations with liver cancer and non-Hodgkin lymphoma are also suggested. Pregnant women are vulnerable, as TCE exposure has been linked to developmental effects in offspring, including heart defects.
Environmentally, TCE is a concern due to its persistence and mobility. When released, it leaches through soil into groundwater, degrading slowly, especially under oxygen-free conditions. Being denser than water, TCE can sink through aquifers, forming dense non-aqueous phase liquid (DNAPL) pools challenging to locate and remove. This results in long-lasting contamination plumes that spread and affect drinking water sources.
Managing TCE Exposure and Contamination
Regulatory bodies, like the U.S. Environmental Protection Agency (EPA), establish standards and regulations to address TCE contamination and limit exposure. The EPA has characterized TCE as an unreasonable risk to human health. Recently, the EPA issued a final rule banning the manufacture, processing, and distribution of TCE for most uses, with some industrial uses phased out over longer timeframes.
For contaminated sites, various remediation techniques reduce or remove TCE. “Pump and treat” systems extract contaminated groundwater, treat it above ground using methods like air stripping or activated carbon filtration, and then re-inject or discharge the treated water. Other in-situ (in-place) methods treat contamination directly in the ground.
Soil vapor extraction (SVE) removes volatile contaminants like TCE from soil by applying a vacuum to extract soil gas. Bioremediation uses microorganisms to break down TCE into less harmful substances. In-situ chemical oxidation (ISCO) involves injecting chemical oxidants into the ground to chemically transform TCE. These efforts mitigate TCE risks and restore affected environments.