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ETHYLBENZENE
CASRN: 100414

Update: August 1993

Current Massachusetts Regulatory Limit
MMCL = 0.7 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).

Federal Regulatory Limit
The MCL is based on the MCLG of 0.7 mg/L.

Basis for Criteria
 

The MCLG is derived using the RfD presented below and assuming 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.

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

Critical Effects
Liver and kidney toxicity. The RfD is based on the results of a 182 day oral bioassay in which ethylbenzene was given to rats by gavage. There were 10 albino rats/sex/dose at doses of 13.6, 136, 408 or 680 mg/kg/day. A LOAEL of 408 mg/kg/day was associated with histopathological changes in the liver and the kidneys. The reference dose is based on an adjusted NOAEL of 97.1 mg/kg/day identified from a rat subchronic to chronic oral bioassay. (Wolf et al. 1956).

Cancer Assessment: 
Ethylbenzene has been identified in U.S. EPA's Group D, based upon inadequate evidence of carcinogenicity in animals.

Class
VOC

Analytical Information
PQL
: 0.0005 mg/L

Analytical Methods
502.2; GC/PID
503.1; GC/PID-FID in series
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 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. November 13, 1985. Part IV. Environmental Protection Agency. 40 CFR Part 141. National Primary Drinking Water Regulations: Synthetic Organic Chemicals, Inorganic Chemicals and Microorganisms; Proposed Rule. (50 FR 46936).

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).

Wolf, MA., V.K. Rowe, D.D. McCollister, R.C. Hollingsworth and F. Oyer. 1956. Toxicological studies of certain alkylates, benzenes and benzene. Arch. Ind. Health. 14:387-398.