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CASRN: 50328

Update: August 1993

Current Massachusetts Regulatory Limit
MMCL = 0.0002 mg/L. ORS has adopted the MCL published by the U.S. EPA as part of the Phase V rule (57 FR 31776: 7-17-92). 

Federal Regulatory Limit
The MCL for benzo(a)pyrene is based on its detection limit of 0.0002 mg/L. The MCLG is zero. 

Basis for Criteria
The MCLG is zero based on its classification as a B2 carcinogen. The MCL is set at the PQL of 0.0002 mg/L.

Critical Effects
Acute exposure to benzo[a]pyrene for relatively short periods of time at levels above the MCL may cause red blood cell damage, leading to anemia and a suppressed immune system. Upon longer-term exposure to levels above the MCL, benzo[a]pyrene may cause developmental and reproductive effects and cancer. 

Cancer Assessment
Forestomach tumors, squamous cell papillomas and carcinomas were produced in CFW mice exposed to benzo[a]pyrene in the diet.

Benzo[a]pyrene has been classified as a B2 (probable) human carcinogen via the older U.S. EPA cancer classification system. Under U.S. EPA's Proposed Guidelines for Carcinogen Risk Assessment (U.S. EPA, 1999), this classification would correspond to the descriptor "likely to be carcinogenic to humans".

U.S. EPA developed an oral cancer slope factor for benzo[a]pyrene of
5.76 (mg/kg/day)-1.

Polycyclic aromatic hydrocarbon (PAH)

Analytical Information
: The PQL used as the basis for the MCL is 0.0002 mg/L.

Analytical Methods
U.S. EPA Methods 525.1; 550; 550.1

PQLs and analytical methods may have been updated since this guidance value was last revised. Updated analytical methods for drinking water and their associated PQLs may be found at

Other Regulatory Data
Any Health Advisories, Reference Doses (RfDs), cancer assessments or Cancer Potency Factors (CPFs) referenced in this document pertain to the derivation of the current guidance value. Updated information may be obtained from the following sources:

Health Advisories - The U.S. EPA provides guidance for shorter-term exposures for chemicals based on their non-cancer effects. Current health advisories may be more current than those used to derive MCLs and may be found at

RfDs, cancer assessments and CPFs - For specific information pertaining to derivation of drinking water criteria, consult the Federal Register notice that announces the availability of the most current guidance for that chemical. In addition, information on other current RfDs and CPFs as well as cancer assessments for specific chemicals may be found in the U.S. EPA Integrated Risk Information System (IRIS) at Please note that the information in IRIS may differ from that used in the derivation process as published in the Federal Register notice.

Federal Register. July 17, 1992. Part III. Environmental Protection Agency. 40 CFR Parts 141 and 142. National Primary Drinking Water Regulations; Synthetic Organic Chemicals and Inorganic Chemicals; Final Rule. (57 FR 31776).

U.S. EPA. (Last updated 4/27/04). Consumer Factsheet on: Benzo[a]pyrene. Office of Groundwater and Drinking Water.

U.S. EPA. (Last updated 11/26/02). Technical Factsheet on: Benzo[a]pyrene. Office of Groundwater and Drinking Water.

U.S. EPA. (Last updated 11/18/04). Benzo[a]pyrene, (CASRN: 50-32-8). Integrated Risk Information System (IRIS). U.S. Environmental Protection Agency. Washington, D.C.

U.S. EPA (U.S. Environmental Protection Agency). July 1999. Guidelines for Carcinogen Risk Assessment. Review Draft. NCEA-F-0644. Risk Assessment Forum.