Benzo[a]pyrene (BaP) CASRN 50-32-8 | IRIS

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

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 (Combined route)	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: 2 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, includes application of age-dependent adjustment factors (ADAFs).
Tumor site(s): Gastrointestinal
Tumor type(s): forestomach, esophagus, tongue, and larynx tumors (Kroese et al. 2001; Beland and Culp, 1998)
Note: EPA has concluded that benzo[a]pyrene is carcinogenic by a mutagenic mode of action. Thus, based on the EPA cancer guidelines (2005), the oral slope factor (OSF) addressing lifetime exposure includes application of ADAFs. The OSF is recommended for lifetime exposures. EPA has also provided an adult-based cancer slope factor of 1 per mg/kg-day. This adult-based cancer slope factor can be used instead of the OSF when assessing cancer risk associated with exposure scenarios that don’t include early life (< 16 years of age) or when other calculations by the user are necessary (e.g., when applying ADAFs to age-specific exposure estimates).

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

Inhalation Unit Risk: 1 x 10^-3 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, includes application of age-dependent adjustment factors (ADAFs).
Tumor site(s): Respiratory, Gastrointestinal
Tumor type(s): Squamous cell neoplasia in the larynx, pharynx, trachea, nasal cavity, esophagus, and forestomach. (Thyssen et al., 1981)
Note: EPA has concluded that benzo[a]pyrene is carcinogenic by a mutagenic mode of action. Thus, based on the EPA cancer guidelines (2005), the inhalation unit risk (IUR) addressing lifetime exposure includes application of ADAFs. The IUR is recommended for lifetime exposures. EPA has also provided an adult-based cancer unit risk of 6 x 10^-4 per µg/m³. This adult-based cancer unit risk can be used instead of the IUR when assessing cancer risk associated with exposure scenarios that don’t include early life (< 16 years of age) or when other calculations by the user are necessary (e.g., when applying ADAFs to age-specific exposure estimates).

Organ/System-Specific RfDs

System	RfD (mg/kg-day)	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	Notes
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

Jan 2017: IRIS Toxicological Review of Benzo[A]Pyrene (Final Report) (Report)

Sep 2016: IRIS Toxicological Review of Benzo[a]pyrene (Interagency Science Discussion Draft) (Report)

Sep 2014: IRIS Toxicological Review of Benzo[a]pyrene (External Review Draft) (Report)

Aug 2013: IRIS Toxicological Review of Benzo[a]pyrene (Public Comment Draft) (Report)

Jun 2011: IRIS Toxicological Review of Benzo[a]pyrene (Interagency Science Consultation Draft) (Report)

Sep 1984: Health Effects Assessment for Benzo[a]pyrene (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.

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