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CASRN: 74839

Update: August 1993

Current Massachusetts Regulatory Limit
ORSGL = 0.01 mg/L. 

Federal Regulatory Limit
The U.S. EPA has not published an MCL for bromomethane 

Basis for Criteria
The ORSGL is based on the RfD presented below and assumes that a 70 kg adult ingests 2 L/day of drinking water. A relative source contribution factor of 20% is incorporated into the final value (U.S. EPA, 1991).

RfD: 1.4 x 10-3 mg/kg/day

UF: 1000 (10 = intraspecies; 10 = interspecies; 10 = subchronic to chronic)
MF: 1 Confidence in RfD: Medium

Critical Effects
The RfD is based on results from a subchronic gavage study in rats (Danse et al 1984). Groups of 10 male and 10 female Wistar rats were treated by gavage 5 days/week for 13 weeks to doses of 0, 0.4, 2, 10 or 50 mg/kg/day. Severe hyperplasia of the stratified squamous epithelium of the forestomach was reported. A NOAEL of 2.0 mg/kg/day was identified from this study and used to develop the RfD. The NOAEL was adjusted to 1.4 mg/kg/day by extrapolating to a 7-day/week exposure from a 5-day per week exposure (i.e., by multiplying the dose by 5/7). 

Cancer Assessment D
Bromomethane has been identified in U.S. EPA's Group D based on inadequate human evidence of carcinogenicity. 


Analytical Information
: 0.5 ug/L 

Analytical Methods
U.S. EPA 502.1, 502.2, 502.3, GC
U.S. EPA 524.1, 524.2, GC/MS

PQLs and analytical methods may have been updated since this guidance value was last revised. Updated analytical methods for drinking water and their associated PQLs may be found at

Other Regulatory Data
Any Health Advisories, Reference Doses (RfDs), cancer assessments or Cancer Potency Factors (CPFs) referenced in this document pertain to the derivation of the current guidance value. Updated information may be obtained from the following sources:

Health Advisories - The U.S. EPA provides guidance for shorter-term exposures for chemicals based on their non-cancer effects. Current health advisories may be more current than those used to derive MCLs and may be found at

RfDs, cancer assessments and CPFs - For specific information pertaining to derivation of drinking water criteria, consult the Federal Register notice that announces the availability of the most current guidance for that chemical. In addition, information on other current RfDs and CPFs as well as cancer assessments for specific chemicals may be found in the U.S. EPA Integrated Risk Information System (IRIS) at Please note that the information in IRIS may differ from that used in the derivation process as published in the Federal Register notice.

Danse, L.H., F.L. Von Vehran and C.A. Van der Heijden. 1984. Methylbromide carcinogenic effects in the rat forestomach. Toxicol. Appl. Pharmacol. 72:262-271.

U.S. EPA (U.S. Environmental Protection Agency). April 10, 1991. Integrated Risk Information System (IRIS). Washington, D.C.