Polychlorinated Biphenyls (PCBs) CASRN 1336-36-3 | IRIS

IRIS

Polychlorinated Biphenyls (PCBs)

CASRN 1336-36-3 | DTXSID5024267

IRIS Summary (PDF) (22 pp, 150 K)
Status: Polychlorinated Biphenyls (PCBs) is in step 1 at this time; see Quick Check.

Noncancer Assessment

Reference Dose for Oral Exposure (RfD) (PDF) (22 pp, 150 K) Last Updated: 06/01/1994
Information reviewed but value not estimated.

Note: See the assessments under Related Links for information on the effects of oral exposure to specific PCB mixtures, including RfDs for Aroclor 1016 and Aroclor 1254.

Reference Concentration for Inhalation Exposure (RfC) (PDF) (22 pp, 150 K)
Not assessed under the IRIS Program.

Cancer Assessment

Weight of Evidence for Cancer (PDF) (22 pp, 150 K) Last Updated: 10/01/1996

WOE Characterization	Framework for WOE Characterization
B2 (Probable human carcinogen - based on sufficient evidence of carcinogenicity in animals)	Guidelines for Carcinogen Risk Assessment (U.S. EPA, 1986)

Basis:

A 1996 study found liver tumors in female rats exposed to Aroclors 1260, 1254, 1242, and 1016, and in male rats exposed to 1260. These mixtures contain overlapping groups of congeners that, together, span the range of congeners most often found in environmental mixtures. Earlier studies found high, statistically significant incidences of liver tumors in rats ingesting Aroclor 1260 or Clophen A 60 (Kimbrough et al., 1975 Norback and Weltman, 1985 Schaeffer et al., 1984). Mechanistic studies are beginning to identify several congeners that have dioxin-like activity and may promote tumors by different modes of action. PCBs are absorbed through ingestion, inhalation, and dermal exposure, after which they are transported similarly through the circulation. This provides a reasonable basis for expecting similar internal effects from different routes of environmental exposure. Information on relative absorption rates suggests that differences in toxicity across exposure routes are small. The human studies are being updated currently available evidence is inadequate, but suggestive.
This may be a synopsis of the full weight-of-evidence narrative.

Quantitative Estimate of Carcinogenic Risk from Oral Exposure (PDF) (22 pp, 150 K)

Oral Slope Factor: 2 per mg/kg-day (high risk and persistence, upper bound)
Extrapolation Method: Linear extrapolation below LED10s
Tumor site(s): Hepatic
Tumor type(s): Liver hepatocellular adenomas, carcinomas, cholangiomas, or cholangiocarcinomas (Brunner et al., 1996 Norback and Weltman, 1985)
Note: Cancer potency of PCB mixtures is determined by a tiered approach that depends on exposure matrix and route, type of congener present, and lifestage. See IRIS Summary for specific factors used to select appropriate slope factor. High risk and persistence: 2 per mg/kg-day; Low risk and persistence: 0.4 per mg/kg-day; Lowest risk and persistence: 0.07 per mg/kg-day.

Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure (PDF) (22 pp, 150 K)

Inhalation Unit Risk: 1 x 10^-4 per µg/m³ (Applies to inhalation of evaporated congeners)
Extrapolation Method: Linear extrapolation below LED10; route-to-route extrapolation from the oral slope factor
Tumor site(s): Hepatic
Tumor type(s): Liver hepatocellular adenomas, carcinomas, cholangiomas, or cholangiocarcinomas (Brunner et al., 1996; Norback and Weltman, 1985)
Note: For inhalation of an aerosol or dust contaminated with PCBs, see the IRIS Summary for information on the appropriate inhalation unit risk.

Program Outlook Details

Public Assessment Materials	Date
Problem Formulation Materials/IRIS Assessment Plan	Apr-2015
Preliminary Assessment Materials/Systematic Review Protocol	Dec-2019
Public Comment	TBD
External Peer Review	TBD
Post Final Assessment	TBD

Note: Any future dates displayed in the table above should be considered estimates and are subject to change. Once the external peer review is complete, estimated dates for release of the final assessment will be published. For the latest information on the status of this assessment, please refer to the IRIS Program Outlook. To access assessment documents, meeting materials or other supporting documents related to this assessment, visit the Chemical Documents tab. For more information about the development process, visit the IRIS Process page.

Mar 2023: A Systematic Evidence Map of Noncancer Health Endpoints and Exposures to Polychlorinated Biphenyl (PCB) Mixtures (Report)

Mar 2022: Mixtures Modeling Methods: Applications for Assessing Polychlorinated Biphenyls (PCBS) (Webinar) (Other)

Dec 2019: Systematic Review Protocol for the Polychlorinated Biphenyls (PCBs) Noncancer IRIS Assessment (Preliminary Assessment Materials) (Report)

Mar 2015: IRIS Toxicological Review of Polychlorinated Biphenyls (PCBs) (Scoping and Problem Formulation Materials) (Report)

Sep 1996: PCBs: Cancer Dose-Response Assessment and Application to Environmental Mixtures (1996) (Report)

Sep 1984: Health Effects Assessment for Polychlorinated Biphenyls (PCBs) (Report)

Additional EPA toxicity information may be available by visiting the following sites:

Human Health Benchmarks for Pesticides (HHBP). This database provides human health benchmarks for pesticides that may be present in drinking water.
Office of Pesticide Programs Pesticide Chemical Search. This database provides links to health effects information and registration status for pesticides.
Chemistry Dashboard. This database provides information on chemical structures, experimental and predicted physicochemical, and toxicity data.

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more.

US EPA

IRIS