IRIS Toxicological Review of Benzo[a]pyrene (Interagency Science Discussion Draft)

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In January 2017, EPA finalized the IRIS assessment of Benzo[a]pyrene. The Toxicological Review was reviewed internally by EPA and by other federal agencies and White House Offices before public release. Consistent with the May 2009 IRIS assessment development process, all written comments on IRIS assessments submitted by other federal agencies and White House Offices are made publicly available. Accordingly, interagency comments and the interagency science discussion materials provided to other agencies, including interagency review drafts of the IRIS Toxicological Review of Benzo[a]pyrene are posted on this site.

Benzo[a]pyrene is a five-ring polycyclic aromatic hydrocarbon (PAH). Benzo[a]pyrene (along with other PAHs) is released into the atmosphere as a component of smoke from forest fires, industrial processes, vehicle exhaust, cigarettes, and through the burning of fuel (such as wood, coal, and petroleum products). Oral exposure to benzo[a]pyrene can occur by eating certain food products, such as charred meats, where benzo[a]pyrene is formed during the cooking process, or by eating foods grown in areas contaminated with benzo[a]pyrene (from the air and soil). Dermal exposure may occur from contact with soils or materials that contain soot, tar, or crude petroleum products or by using certain pharmaceutical products containing coal tars, such as those used to treat the skin conditions, eczema and psoriasis. The magnitude of human exposure to benzo[a]pyrene and other PAHs depends on factors such as lifestyle (e.g., diet, tobacco smoking), occupation, and living conditions (e.g., urban versus rural setting, domestic heating, and cooking methods).

Animal studies demonstrate that exposure to benzo[a]pyrene is associated with developmental (including developmental neurotoxicity), reproductive, and immunological effects. In addition, epidemiology studies involving exposure to PAH mixtures have reported associations between internal biomarkers of exposure to benzo[a]pyrene (benzo[a]pyrene diol epoxide-DNA adducts) and adverse birth outcomes (including reduced birth weight, postnatal body weight, and head circumference), neurobehavioral effects, and decreased fertility.

Studies in multiple animal species demonstrate that benzo[a]pyrene is carcinogenic at multiple tumor sites (alimentary tract, liver, kidney, respiratory tract, pharynx, and skin) by all routes of exposure. In addition, there is strong evidence of carcinogenicity in occupations involving exposure to PAH mixtures containing benzo[a]pyrene, such as aluminum production, chimney sweeping, coal gasification, coal-tar distillation, coke production, iron and steel founding, and paving and roofing with coal tar pitch. An increasing number of occupational studies demonstrate a positive exposure-response relationship with cumulative benzo[a]pyrene exposure and lung cancer.


EPA is undertaking an update of the Integrated Risk Information System (IRIS) health assessment for benzo[a]pyrene (BaP). The outcome of this project is an updated Toxicological Review and IRIS Summary for BaP that will be entered into the IRIS database.


The benzo[a]pyrene assessment has been loaded into the IRIS website and database.


U.S. EPA. IRIS Toxicological Review of Benzo[a]pyrene (Interagency Science Discussion Draft). U.S. Environmental Protection Agency, Washington, DC, EPA/635/R-16/331, 2016.


Date Description
01-Jun 2011EPA initiated the interagency science consultation on the draft Toxicological Review of Benzo[a]pyrene.
02-Jun 2012A revised interagency science consultation draft Toxicological Review of Benzo[a]pyrene was provided for further review by other federal agencies and the Executive Office of the President.
03-Aug 2013EPA released a public comment draft for review and comments. EPA also released the interagency science consultation documents, comments from reviewers, and EPA's response to major comments. [Federal Register Notice: Aug 21, 2013]
06-Dec 2013EPA held a public meeting to engage stakeholders in early discussions on the draft IRIS assessment and draft charge.
09-Sep 2014EPA transmitted the external peer review draft benzo[a]pyrene assessment, including responses to major public comments, and the draft charge to the peer reviewers to the SAB. This draft and related materials were also posted on the IRIS website.
10-Apr 2016EPA's SAB released a final report of their review of the draft IRIS assessment (see downloads). [SAB's Benzo[a]pyrene Review Page]
11-Nov 2016EPA submitted a revised draft for final Agency Review and Interagency Science Discussion.
12-Jan 2017EPA posted the final Toxicological Review of Benzo[a]pyrene to the IRIS database.

This download(s) is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not been formally disseminated by EPA. It does not represent and should not be construed to represent any Agency determination or policy.