Conclusions from the TSCA Trichloroethylene Assessment
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Each year, the United States uses 225 million pounds of TCE, a volatile organic compound (VOC) and human carcinogen. TCE is used widely, primarily in industrial and commercial processes as a solvent, degreaser, and fixative. EPA’s Office of Pollution Prevention and Toxics (EPA/OPPT) focused the TCE assessment on characterizing human-health risks from inhalation and exposures to the chemical in scenarios “that were expected to make frequent use of TCE in high concentrations and/or pose high potential for human exposure.”
While the EPA/OPPT recognizes that TCE can be absorbed through the skin, in light of the physical-chemical properties of TCE and the scenarios assessed, the EPA/OPPT chose inhalation as the main exposure pathway for the risk assessment. As a result, according to the EPA, the “assessment may underestimate total exposures resulting from the uses of TCE…” The assessment also does not include environmental impacts.
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Ultimately, the EPA/OPPT assessment covered acute and chronic risks for thousands of workers in two types of businesses: 30,000 workers at small degreasing facilities using TCE as a degreaser and 300,000 workers at dry-cleaning facilities that use TCE as a solvent degreaser or spotting agent. Workers were assumed to be both male and female (including pregnant women) and age 16 years or older. Risks were also assessed for “occupational bystanders,” such as workers in the vicinity of TCE operations but not actually performing the operations. The EPA/OPPT also included acute risks associated with consumer exposures in residential settings with risk estimates focused on pregnant women and their developing fetuses.
Since TCE was already known to be a human carcinogen, the results of the assessment reveal more about risk related to the level of exposure in degreasing and dry-cleaning operations. These include:
- There are cancer risk concerns for users and bystanders occupationally exposed to TCE when using TCE‐containing degreasers and spot cleaners in small commercial shops and dry-cleaning facilities, respectively.
- Many of the commercial vapor degreasing and spot cleaning exposure scenarios exceed the excess lifetime cancer risk probabilities of 1 chance in 10,000, 100,000, or 1 million (i.e., target cancer risks of 10‐4, 10‐5, and 10‐6, respectively) of an individual developing cancer.
- Comparing the occupational exposures in degreasing vs. dry-cleaning operations, degreasing operations show the greatest cancer risk.
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The assessment also revealed acute noncancer risks, including:
- Developmental effects (i.e., cardiac defects) for most occupational and residential exposure scenarios (i.e., margins of exposure (MOE) were below the benchmark MOE of 10).
- Comparing the occupational exposures in degreasing vs. dry-cleaning operations, degreasing operations show the greatest acute noncancer risk.
In addition, chronic noncancer risks were found to be:
- Chronic noncancer risks for human health effects in both occupational scenarios (i.e., MOE below the MOE benchmark of 10), with an overall higher chronic risk for the degreaser exposure scenarios, including developmental effects (i.e., fetal cardiac defects), kidney effects, and immunotoxicity. In general, concern is irrespective of the type of exposure (typical vs. worst case) and the availability of room ventilation.
- Reproductive effects and neurotoxicity for degreaser worker exposure scenarios and most of the degreaser bystander exposure scenarios. However, the risks concerns for these effects are reported for fewer spot cleaning worker/bystander scenarios and are generally attributed to exposure conditions without room ventilation.
- Liver effects, although these are less prominent than those reported for other health effects and are found only in the degreaser worker/bystander exposure worst case scenarios and the spot cleaning worker/bystander worst case scenarios with no LEV.
Based on these findings the EPA recommends taking precautions to reduce TCE exposures, such as using the product outside or in an extremely well-ventilated area, and wearing protective equipment. Additional work is ongoing to define alternative chemicals and processes to replace TCE and reduce associated risks and subsequent health impacts using voluntary and regulatory actions.