## Kathleen Newhouse, Assessment Manager



# IRIS Draft Toxicological **Review for Benzo[a]pyrene (**  **BaP )** 

**Office of Research and Development** National Center for Environmental Assessment **December 13, 2013 Office of Research and Development** 

National Center for Environmental Assessment 

## General Information Five- ring polycyclic aromatic hydrocarbon • Relatively insoluble in water • Low volatility Ubiquitous in the environment primarily as a result of incomplete combustion emissions • Natural sources include forest fires and volcanoes • Anthropogenic sources include stoves/furnaces burning fossil fuels (especially wood and coal), motor vehicle exhaust, and various industrial combustion processes 

## Exposure Major sources of occupational exposure involve • P roduction of aluminum, coke, graphite, and silicon carbide • Coal tar distillation Major sources of non -occupational exposure • Tobacco products • Diet (e.g. barbequed or charred meats) 1**Office of Research and Development**

National Center for Environmental Assessment 

## Agency Interest in BaP Hazardous substance under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) • Found at 524 hazardous waste sites on the National Priorities List (NPL) Drinking water contaminant under the Safe Drinking Water Act (SDWA) • Maximum Contaminant Level Goal (MCLG) of zero and enforceable Maximum Contaminant Level (MCL) of 0.0002 mg/L have been established Component in a class of chemicals referred to as Polycyclic Organic Matter, defined as a Hazardous Air Pollutant in the 1990 amendments to the Clean Air Act Index chemical for the EPA Relative Potency Factor approach for PAH mixtures
2**Office of Research and Development**

National Center for Environmental Assessment 3**Office of Research and Development**

National Center for Environmental Assessment **3** 

### Literature Search Strategy
•The literature search identified more than 21,000 studies for BaP. • Approximately 700 references we re cited in the August 2013 Toxicological Review

( Public Comment Draft).

4**Office of Research and Development**

National Center for Environmental Assessment 

## Health Hazards Identified in the Public Comment Draft EFFECTS OTHER THAN CANCER • Animal studies indicate that the strongest evidence for potential hazard following BaP exposure is for **dev elopmental**  and **reproductiv e**  **toxicity** and **immunotoxicity** .
• Human studies report ef fects that are generally analogous to the ef fects observed in animal toxicological studies, and provide qualitative, supportive evidence. CANCER • Under EP

A’s Guidelines for Carcinogen Risk Assessment (2005) BaP is **“carcinogenic to humans”** based on strong and consistent evidence in humans and animals, as well as mechanistic data .
• The weight of evidence supports **mutagenicity** as the primary mode of action for BaP- induced carcinogenicity. 5**Office of Research and Development**

National Center for Environmental Assessment 

## Specific Issues Identified in the Public Comment Draft Charge The new d ocument structure • The Preamble • Executive Summary • Literature Search Strategy/Study Selection The synthesis, integration, and weight of the evidence for the identified hazards The development of candidate values and organ/system -specific reference values The development of cancer risk estimates for oral, inhalation, and dermal exposure • Including the method used for interspecies scaling of the dermal slope factor
6**Office of Research and Development**

National Center for Environmental Assessment 

## Innovative Features of the BaP Public Comment Draft

• New d ocument structure, responsive to NRC recommendations
• First IRIS derivation of non -cancer reference values for BaP
• First assessment to calculate multiple organ/system specific reference values (facilitates subsequent risk assessments of multiple chemicals)
• First IRIS inhalation unit risk for BaP ; updated oral slope factor
• Presentation of the first dermal cancer risk estimate for any chemical on IRIS
• First characterization of a chemical as “carcinogenic to humans” based in part on mechanistic data
• First systematic analysis of transcriptomics data in an IRIS assessment 7