Bromoform Quickview (CASRN 75-25-2)

Status of Data for Bromoform

File First On-Line: 09/30/1987; Last Significant Revision: 12/01/1993

Category (section)	Status	Last Revised
Oral RfD Assessment	On-line	03/01/1991
Inhalation RfC Assessment	Message	12/01/1993
Carcinogenicity Assessment	On-line	01/01/1991

Synonyms

75-25-2 Bromoform Methane, tribromo-

Methenyl tribromide Tribromomethane

Chronic Health Hazard Assessments for Noncarcinogenic Effects

Reference Dose for Chronic Oral Exposure (RfD)

Critical Effect	Point of Departure*	UF	MF	RfD
Hepatic lesions	NOEL : 17.9 mg/kg-day	1000	1	2 x10-2 mg/kg-day

* The Point of Departure listed serves as a basis from which the Oral RfD was derived. See Discussion of Conversion Factors and Assumptions for more details.

• Principal and Supporting Studies (Oral RfD)
  • Rat, subchronic oral gavage bioassay, NTP, 1989
• Confidence in the Oral RfD
  • Study -- Medium
  • Database -- Medium
  • RfD -- Medium

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Reference Concentration for Chronic Inhalation Exposure (RfC)

Information reviewed but value not estimated. See IRIS Summary.

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Carcinogenicity Assessment for Lifetime Exposure

• Weight-of-Evidence Characterization
  • B2 (Probable human carcinogen - based on sufficient evidence of carcinogenicity in animals)
• Weight-of-Evidence Narrative:
  • Based on inadequate human data and sufficient evidence of carcinogenicity in animals, namely an increased incidence of tumors after oral administration of bromoform in rats and intraperitoneal administration in mice. Bromoform is genotoxic in several assay systems. Also, bromoform is structurally related to other trihalomethanes (e.g., chloroform, bromodichloromethane, dibromochloromethane) which have been verified as either probable or possible carcinogens.
  • This may be a synopsis of the full weight-of-evidence narrative. See IRIS Summary.

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Quantitative Estimate of Carcinogenic Risk from Oral Exposure

Oral Slope Factor(s)	Extrapolation Method
7.9 x10-3 per mg/kg-day	Linearized multistage procedure, extra risk

Drinking Water Unit Risks
2.3x10-7 per ug/L

Risk Level	Concentration
E-4 (1 in 10,000)	4x102 ug/L
E-5 (1 in 100,000)	4x101 ug/L
E-6 (1 in 1,000,000)	4 ug/L

• Dose-Response Data (Carcinogenicity, Oral Exposure)
  • Tumor Type: Neoplastic lesions in the large intestine
  • Test Species: F344/N rat, female
  • Route: Oral, Gavage in corn oil
  • Reference: NTP, 1988

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Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure

Inhalation Unit Risk(s)	Extrapolation Method
1.1 x10-6 per ug/m3	Linearized multistage procedure, extra risk

Inhalation Concentrations at Specified Risk Levels

Risk Level	Concentration
E-4 (1 in 10,000)	9x101 ug/m3
E-5 (1 in 100,000)	9 ug/m3
E-6 (1 in 1,000,000)	9x10-1 ug/m3

• Dose-Response Data (Carcinogenicity, Inhalation Exposure)
  • Tumor Type: Neoplastic lesions in the large intestine
  • Test Species: F344/N rat, female
  • Route: Oral, Gavage in corn oil
  • Reference: NTP, 1988