Chromium(VI) CASRN 18540-29-9 | IRIS

IRIS

Chromium(VI)

CASRN 18540-29-9 | DTXSID7023982

Toxicological Review (PDF) (538 pp, 10.09 M)
IRIS Summary (PDF) (14 pp, 473 K)

Noncancer Assessment

Reference Dose for Oral Exposure (RfD) (PDF) (14 pp, 473 K) Last Updated: 08/01/2024

System	RfD (mg/kg-day)	Basis	PoD	Composite UF	Confidence
Gastrointestinal	9 x 10 ^-4	GI tract effects in mice and rats	HED : 9.11 x 10^-2 mg/kg-day	100	Medium/High

Reference Concentration for Inhalation Exposure (RfC) (PDF) (14 pp, 473 K) Last Updated: 08/01/2024

System	RfC (mg/m³)	Basis	PoD	Composite UF	Confidence
Respiratory	3 x 10 ^-5	Ulcerated nasal septum in humans	LOAEL : 3.4 x 10^-3 mg/m³	100	Medium

Cancer Assessment

Weight of Evidence for Cancer (PDF) (14 pp, 473 K) Last Updated: 08/01/2024

WOE Characterization	Framework for WOE Characterization
Carcinogenic to humans (Inhalation route)	Guidelines for Carcinogen Risk Assessment (U.S. EPA, 2005)
Likely to be carcinogenic to humans (Oral route)	Guidelines for Carcinogen Risk Assessment (U.S. EPA, 2005)

Basis:

Under EPA’s Guidelines for Carcinogen Risk Assessment (U.S. EPA, 2005), Cr(VI) is “likely to be carcinogenic” via oral exposure based on sufficiently supported [laboratory] animal studies relevant to humans. This assessment maintains the previous conclusion (U.S. EPA, 1998) that Cr(VI) is “carcinogenic to humans” via inhalation exposure.
This may be a synopsis of the full weight-of-evidence narrative.

Quantitative Estimate of Carcinogenic Risk from Oral Exposure (PDF) (14 pp, 473 K)

Oral Slope Factor: 0.27 per mg/kg-day
Extrapolation Method: HEDs calculated using BW3/4 scaling
Tumor site(s): Gastrointestinal
Tumor type(s): Squamous cell carcinoma or squamous cell papilloma. (NTP, 2008)
Note: EPA has concluded that Cr(VI) 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 age-dependent adjustment factors (ADAFs). The OSF is recommended for lifetime exposures. An adult-based cancer slope factor of 0.16 per mg/kg-day is also provided. 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) (14 pp, 473 K)

Inhalation Unit Risk: 0.018 per µg/m³
Extrapolation Method: Linear extrapolation from LEC01 derived from Cox proportional hazard model with 5 year lag using lifetable analysis.
Tumor site(s): Respiratory
Tumor type(s): Lung cancer
Note: EPA has concluded that Cr(VI) 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 age-dependent adjustment factors (ADAFs). The IUR is recommended for lifetime exposures. An adult-based cancer inhalation unit risk of 0.011 per µg/m3 is also provided. This adult-based cancer inhalation 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).

Aug 2024: IRIS Toxicological Review of Hexavalent Chromium (Final Report, 2024) (Report)

May 2024: IRIS Toxicological Review of Hexavalent Chromium (Interagency Science Discussion Draft, 2024) (Report)

Oct 2022: IRIS Toxicological Review of Hexavalent Chromium (External Review Draft, 2022) (Report)

Feb 2022: IRIS Toxicological Review of Hexavalent Chromium (Interagency Science Consultation Draft, 2022) (Report)

Mar 2019: Updated Systematic Review Protocol for the Hexavalent Chromium IRIS Assessment (Preliminary Assessment Materials, 2019) (Report)

Sep 2014: IRIS Toxicological Review of Hexavalent Chromium Part 2: Human, Toxicokinetic, and Mechanistic Studies (Preliminary Assessment Materials, 2014) (Report)

Apr 2014: IRIS Toxicological Review of Hexavalent Chromium Part 1: Experimental Animal Studies (Preliminary Assessment Materials, 2014) (Report)

Sep 2013: Hexavalent Chromium Workshops (2013) (Other)

Sep 2010: IRIS Toxicological Review of Hexavalent Chromium (2010 External Review Draft) (Report)

May 2010: IRIS Toxicological Review of Hexavalent Chromium (2010 Interagency Science Consultation Draft) (Report)

Sep 1998: IRIS Toxicological Review of Chromium VI (1998 Final) (Report)

Apr 1990: Noncarcinogenic Effects of Chromium: Update to Health Assessment Document (Report)

Sep 1984: Health Effects Assessment for Hexavalent Chromium (1984 Final) (Report)

Aug 1983: Health Assessment Document for Chromium (1983 Final) (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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