IRIS

Benzo[a]pyrene (BaP)

CASRN 50-32-8 | DTXSID2020139

Toxicological Review (PDF) (234 pp, 4.67 M)
IRIS Executive Summary (PDF) (9 pp, 671 K)
Supplemental Information on the IRIS Toxicological Review of Benzo[a]pyrene

Key IRIS
Values
Organ/System
Specific Values
Chemical
Documents
Other EPA
Information

Noncancer Assessment

Reference Dose for Oral Exposure (RfD) (PDF) (9 pp, 671 K) Last Updated: 01/19/2017

System	RfD (mg/kg-day)	Basis	PoD	Composite UF	Confidence
Developmental	3 x 10^-4	Neurobehavioral changes	BMDL_1SD (HED): 9.2 x 10^-2 mg/kg-day	300	Medium

Reference Concentration for Inhalation Exposure (RfC) (PDF) (9 pp, 671 K) Last Updated: 01/19/2017

System	RfC (mg/m³)	Basis	PoD	Composite UF	Confidence
Developmental	2 x 10^-6	Decreased embryo/fetal survival	LOAEL : 4.6 x 10^-3 mg/m³	3000	Low/Medium

Cancer Assessment

Weight of Evidence for Cancer (PDF) (9 pp, 671 K) Last Updated: 01/19/2017

WOE Characterization	Framework for WOE Characterization
Carcinogenic to humans	Guidelines for Carcinogen Risk Assessment (U.S. EPA, 2005)

Basis:

Under EPA’s Guidelines for Carcinogen Risk Assessment (U.S. EPA, 2005), benzo[a]pyrene is “carcinogenic to humans” based on strong and consistent evidence in animals and humans.
This may be a synopsis of the full weight-of-evidence narrative.

Quantitative Estimate of Carcinogenic Risk from Oral Exposure (PDF) (9 pp, 671 K)

Oral Slope Factor: 1 per mg/kg-day
Extrapolation Method: Time-to-tumor dose-response model with linear extrapolation from the POD (BMDL₁₀(HED)) associated with 10% extra cancer risk.
Tumor site(s): Gastrointestinal
Tumor type(s): forestomach, esophagus, tongue, and larynx tumors (Kroese et al. 2001; Beland and Culp, 1998)
Note: ADAF -- EPA has concluded that benzo[a]pyrene is carcinogenic by a mutagenic mode of action. Application of age-dependent adjustment factors (ADAFs) to the oral slope factor is recommended in combination with appropriate exposure data when assessing risk associated with early-life exposure.

Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure (PDF) (9 pp, 671 K)

Inhalation Unit Risk: 6 x 10^-4 per µg/m³
Extrapolation Method: Time-to-tumor dose-response model with linear extrapolation from the POD ((BMCL₁₀(HED)) associated with 10% extra cancer risk.
Tumor site(s): Gastrointestinal, Respiratory
Tumor type(s): Squamous cell neoplasia in the larynx, pharynx, trachea, nasal cavity, esophagus, and forestomach. (Thyssen et al., 1981)
Note: ADAF -- EPA has concluded that benzo[a]pyrene is carcinogenic by a mutagenic mode of action. Application of age-dependent adjustment factors (ADAFs) to the inhalation unit risk is recommended in combination with appropriate exposure data when assessing risk associated with early-life exposure.

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.

Organ/System-Specific RfDs

System	RfD (mg/m³)	Basis	POD	UF	Confidence
Developmental	3 x 10^-4	Neurobehavioral changes	BMDL_1SD (HED): 9.2 x 10^-2 mg/kg-day	300	Medium
Reproductive	4 x 10^-4	Decreased ovarian follicles and ovary weight	BMDL_1SD (HED): 3.7 x 10^-1 mg/kg-day	1000	Medium
Immune	2 x 10^-3	Decreased thymus weight and serum IgM	BMDL_1SD (HED): 1.9 mg/kg-day	1000	Low

Organ/System-Specific RfCs

System	RfC (mg/m³)	Basis	POD	UF	Confidence
Developmental	2 x 10^-6	Decreased embryo/fetal survival	LOAEL : 4.6 x 10^-3 mg/m³	3000	Low/Medium
Reproductive	3 x 10^-6	Reduced ovulation rate and ovary weight	LOAEL : 9.1 x 10^-3 mg/m³	3000	Low/Medium