Trichloroethylene (TCE) is a chemical that has been a fixture in industrial processes for nearly a century. This substance is recognized as a hazardous compound, and its widespread use and environmental persistence have established it as a significant public health concern. The properties that once made it an industry favorite are the same characteristics that allow it to contaminate water and air over vast areas. Understanding the nature of TCE and its long-term effects is crucial for addressing the risks it poses to communities.
Defining Trichloroethylene
TCE is a colorless, nonflammable liquid classified as a Volatile Organic Compound (VOC). It possesses a distinctive sweet or chloroform-like odor, although it often goes undetected at lower, yet still harmful, concentrations in the air. TCE gained popularity in the early 20th century because it is a highly effective solvent for organic materials.
Historically, its primary function was as a solvent for vapor degreasing of metal parts in industries like automotive and electronics manufacturing. It was also used in consumer products such as adhesives, paint removers, spot cleaners, and as an extraction solvent for fats and oils.
Sources of Exposure
The public’s primary exposure risk today stems from environmental contamination rather than direct industrial use. Industrial spills, improper disposal, and leaking storage tanks have caused widespread pollution of soil and groundwater. Since TCE is denser than water, it sinks through the soil, persisting in underground aquifers and acting as a long-term source of contamination.
A particularly concerning pathway is vapor intrusion, which occurs when TCE in contaminated soil or groundwater volatilizes into a gas. This gaseous form can migrate upwards through the subsurface and enter homes, schools, or offices through cracks in foundations, utility conduits, or sumps. Vapor intrusion results in contaminated indoor air, which is a major source of non-occupational exposure for communities living near industrial sites.
Occupational exposure remains a concern for workers who still use TCE as a solvent or are involved in its manufacturing and processing. These individuals are exposed directly through inhalation of vapors and dermal contact with the liquid. Even with regulations, historical and ongoing environmental releases mean that many people are unknowingly exposed through contaminated drinking water or indoor air.
Health Impacts on the Body
Exposure to TCE, whether acute or chronic, affects multiple organ systems. High, short-term exposure to TCE vapors acts as a central nervous system (CNS) depressant. This may result in symptoms such as headaches, dizziness, sedation, confusion, and lack of coordination.
For chronic, lower-level exposures, the primary concern is the development of cancer and organ toxicity. The International Agency for Research on Cancer (IARC) and the U.S. Environmental Protection Agency (EPA) classify TCE as a known human carcinogen. Epidemiological studies have strongly linked long-term exposure to an increased risk of kidney cancer. There is also evidence associating TCE exposure with liver cancer and non-Hodgkin lymphoma.
Beyond cancer, chronic exposure is associated with damage to the liver and kidneys, as the body attempts to metabolize the chemical. It can also suppress the immune system, increasing the risk of autoimmune diseases. Furthermore, TCE is a developmental toxicant, with exposure during the first eight weeks of pregnancy linked specifically to congenital cardiac defects in the fetus.
Remediation and Regulatory Status
The EPA determined that TCE poses an unreasonable risk to human health and has finalized rules to prohibit or phase out most of its uses under the Toxic Substances Control Act (TSCA). TCE is also a common contaminant at sites listed on the National Priorities List, making it a frequent target for Superfund cleanups.
For environmental remediation, various techniques are employed to address existing contamination. Groundwater cleanup often utilizes “pump-and-treat” systems, which extract contaminated water and then treat it above ground using methods like air stripping or activated carbon filtration. For the issue of vapor intrusion in buildings, a common mitigation strategy involves installing a sub-slab depressurization (SSD) system. This system uses a fan to create a negative pressure beneath the building’s foundation, drawing the TCE vapors from the soil and venting them safely into the outdoor air.