Dichloromethane

Reference Dose for Oral Exposure (RfD) (PDF) (44 pp, 337 K) Last Updated: 11/18/2011

Reference Concentration for Inhalation Exposure (RfC) (PDF) (44 pp, 337 K) Last Updated: 11/18/2011

Weight of Evidence for Cancer (PDF) (44 pp, 337 K) Last Updated: 11/18/2011

• Following U.S. EPA (2005) Guidelines for Carcinogen Risk Assessment, dichloromethane is "likely to be carcinogenic in humans," based predominantly on evidence of carcinogenicity at two sites in 2-year bioassays in male and female B6C3F1 mice (liver and lung tumors) with inhalation exposure (NTP, 1986) and at one site in male B6C3F1 mice (liver tumors) with drinking water exposure (Serota et al., 1986b; Hazleton Laboratories, 1983).
• This may be a synopsis of the full weight-of-evidence narrative.

Quantitative Estimate of Carcinogenic Risk from Oral Exposure (PDF) (44 pp, 337 K)

Inhalation Unit Risk: 1.7 x 10^-8 per µg/m³
Extrapolation Method: Multistage model with linear extrapolation from the point of departure (BMDL₁₀), includes application of age-dependent adjustment factors (ADAFs).
Tumor site(s): Hepatic, Respiratory
Tumor type(s): Hepatocellular carcinomas or adenomas, bronchoalveolar carcinomas or adenomas (Mennear et al., 1988; NTP, 1986)
Note: EPA has concluded that dichloromethane 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 1 x 10^-8 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).