Trichloroethylene

Reference Dose for Oral Exposure (RfD) (PDF) (63 pp, 520 K) Last Updated: 09/28/2011

Note: The RfD was derived as a midpoint among three similar candidate RfDs—0.00048 mg/kg-day for decreased thymus weight in mice (Keil et al., 2009), 0.00037 mg/kg-day for developmental immunotoxicity (decreased PFC and increased delayed-type hypersensitivity) in mice (Peden-Adams et al., 2006), and 0.00051 mg/kg-day for fetal heart malformations in rats (Johnson et al., 2003). See Section I.A.1 of the IRIS Summary for Trichloroethylene for more information.

Reference Concentration for Inhalation Exposure (RfC) (PDF) (63 pp, 520 K) Last Updated: 09/28/2011

Note: The RfC was derived as the midpoint of two similar candidate RfCs—0.0019 mg/m³ for decreased thymus weight in mice (Keil et al., 2009) and 0.0021 mg/m³ for fetal heart malformations in rats (Johnson et al., 2003). See Section I.B.1 of the IRIS Summary for Trichloroethylene for more information.

Weight of Evidence for Cancer (PDF) (63 pp, 520 K) Last Updated: 09/28/2011

• Under the Guidelines for Carcinogen Risk Assessment (U.S. EPA, 2005), TCE is characterized as "carcinogenic to humans" by all routes of exposure.
• This may be a synopsis of the full weight-of-evidence narrative.

Quantitative Estimate of Carcinogenic Risk from Oral Exposure (PDF) (63 pp, 520 K)

Inhalation Unit Risk: 4.8 x 10^-6 per µg/m³
Extrapolation Method: Low-dose linear extrapolation from the point of departure (LEC01) with a factor of 4 applied to include non-Hodgkin's lymphoma (NHL) and liver cancer risks, combined risk, includes application of age-dependent adjustment factors (ADAFs).
Tumor site(s): Hematologic, Hepatic, Urinary
Tumor type(s): Renal cell carcinoma, non-Hodgkin's lymphoma, and liver tumors (Charbotel et al. 2006; EPA, 2011; Raaschou-Nielsen et al., 2003)
Note: EPA has concluded that trichloroethylene is carcinogenic by a mutagenic mode of action. Thus, based on the EPA cancer guidelines (2005), the inhalation unit risk (IUR) addressing lifetime exposure includes application of ADAFs. The IUR is recommended for lifetime exposures. EPA has also provided an adult-based cancer unit risk of 4.1 x 10^-6 per µg/m³. This adult-based cancer unit risk can be used instead of the IUR when assessing cancer risk associated with exposure scenarios that don’t include early life (< 16 years of age) or when other calculations by the user are necessary (e.g., when applying ADAFs to age-specific exposure estimates).