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CHLOROBENZENE
CASRN: 108907

Update: August 1993

Current Massachusetts Regulatory Limit
MMCL = 0.1 mg/L. ORS has adopted the MCL published by the U.S. EPA as part of the Phase II rule (56 FR 3526; 1/30/91); (56 FR 30266; 7/1/91). 

Federal Regulatory Limit
The final MCL is based on the MCLG of 0.1 mg/L (56 FR 3526; 1/30/91); (56 FR 30266; 7/1/91). 

Basis for Criteria
The MCLG is based on hepatic toxicity reported in dog studies and was derived assuming a 70 kg adult ingests 2 L/day water. The MCLG assumes a relative source contribution factor of 20%.

RfD: 2 x 10-2 mg/kg/day
UF: 1000 (10 = interspecies; 10 = intraspecies; 10 = subchronic to chronic)
MF: 1

Critical Effects
Histopathological liver changes. The RfD is based on a NOAEL (adjusted) of 19 mg/kg/d identified in a 13 week dog study where the animals were given a capsule containing chlorobenzene. (Knapp et al., 1971; Monsanto, 1967). 

Cancer Assessment D
Chlorobenzene is currently classified as a group D, not classifiable as to human carcinogenicity (Fed. Reg., 1989). 

Class
VOC (chlorinated aromatic)

Analytical Information

Analytical Methods
524.2

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 http://www.epa.gov/safewater/methods/methods.html

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 http://www.epa.gov/waterscience/drinking/standards/dwstandards.pdf

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 http://www.epa.gov/iris/. Please note that the information in IRIS may differ from that used in the derivation process as published in the Federal Register notice.

References
Federal Register. May 22, 1989. Part II. Environmental Protection Agency. 40 CFR Parts 141, 142, and 143. National Primary and Secondary Drinking Water Regulations; Proposed Rule. (54 FR 22062).

Federal Register. January 30, 1991. Part II. Environmental Protection Agency. 40 CFR Parts 141, 142, and 143. National Primary Drinking Water Regulations; Final Rule. (56 FR 3526).

Federal Register. July 1, 1991. Environmental Protection Agency. 40 CFR Parts 141, 142, and 143. National Primary Drinking Water Regulations; Monitoring for Volatile Organic Chemicals; MCLGs and MCLs for Aldicarb, Aldicarb Sulfoxide, Aldicarb Sulfone, Pentachlorophenol, and Barium; Final Rule. (56 FR 30266).

Knapp, W.K., W.M. Busey, and W. Kundzins. 1971. Subacute oral toxicity of monochlorobenzene in dogs and rats. Tox. Appl. Pharmacol. 19:393 (abstract).

Monsanto Chemical Company. 1967. 13 week oral administration -- dogs. Monochlorobenzene. Final Report. Prepared by Hazelton Lab. Proj. No. 249-105.