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CASRN: 78933

Update: May 2004

Current Massachusetts Regulatory Limit
ORSGL = 4.0 mg/L

Federal Regulatory Limit
The U.S. EPA has not published an MCL for methyl ethyl ketone.

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

RfD: 6 x 10-1 mg/kg/day (U.S. EPA, 2003)
UF: 1000 (10 = interspecies; 10 = intraspecies; 10 = database deficiency) MF: 1

Critical Effects
There is limited toxicological data available for methyl ethyl ketone (also known as 2-butanone), although there is sufficient data for its metabolic precursor, 2-butanol. The available pharmacokinetic and toxicological data support the use of 2-butanol as a surrogate for methyl ethyl ketone. Thus, the identification of the critical effect for methyl ethyl ketone is based on toxicological data for 2-butanol. The RfD is based on a multigenerational developmental and reproductive toxicity study in which rats were administered 2-butanol in drinking water. The results of the Cox et al. (1975) study demonstrate that the administration of 2-butanol in drinking water to rats at a concentration of 3% produced maternal toxicity accompanied by developmental effects, but did not affect reproductive performance (with the possible exception of effects on male rat copulatory success) (U.S. EPA, 2003). The critical effect was a decreased pup body weight. A NOAEL of 594 mg/kg/day was identified from this study. The lower 95% confidence limit on the effective dose associated with a 5% decrease in first generation pup (F1) body weight on postnatal day 21 (LED05), a value of 639 mg/L was selected as the point of departure for the RfD (Cox, 1975).

Cancer Assessment: 

Data are inadequate for assessment of human carcinogenic potential.

Methyl ethyl ketone has yielded little or no evidence of mutagenicity. Structure Activity Relationship (SAR) analysis suggests that MEK is unlikely to be carcinogenic based on the absence of any structural characteristics indicative of carcinogenicity (U.S. EPA, 2003).


Analytical Information
: 10 ug/L 

Analytical Methods

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 US EPA Drinking Water Analytical Methods .

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 US EPA Current Drinking Water Health Advisories .

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.

Cox, G.E., Bailey, DE and Morgareidge, K.. 1975. Toxicity studies in rats with 2-butanol including growth, reproduction and teratologic observation. Food and Drug Research Lab, Inc. Waverly, N.Y. Report No. 91MR1R1673.

U.S. EPA (U.S. Environmental Protection Agency). September 26, 2003. Integrated Risk Information System (IRIS). Washington, D.C