Methyl Ethyl Ketone and Methyl Isobutyl Ketone Not Carcinogenic The April 22, 1993, issue of Environmental Health Perspectives contained a commentary by Legator and Strawn entitled "Public Health Policies Regarding Hazardous Waste Sites and Cigarette Smoking: An Argument by Analogy." Although the article does not include any discussion of either methyl ethyl ketone (MEK) or methyl isobutyl ketone (MIBK), it does list them in Table 3 as substances that cause cancer in animals and/or humans." Because MEK and MIBK are both widely used industrial chemicals, they have been studied extensively for possible human health or environmental effects. The Ketones Panel of the Chemical Manufacturers Association has sponsored a number of the studies and surveyed all the pertinent literature on these two compounds. The panel is not aware of any evidence suggesting that either MIBK or MEK causes cancer in humans or animals. Indeed, neither MEK nor MIBK is known or reasonably expected to cause any type of chronic health effect in humans. MEK has been shown to be inactive in a wide variety of in vitro and in vivo genetic toxicity assays and was not neurotoxic in five recent studies. Although MEK has not been tested specifically for carcinogenicity, the data on its structure and metabolism, the results of numerous subchronic studies, and the absence of genotoxicity indicate that MEK is highly unlikely to pose a cancer risk. With respect to MIBK, inhalation studies conducted with rats, mice, dogs, and monkeys all indicate a very low order of subchronic toxicity. The results from a number of different mutagenicity screening assays show that MIBK exhibits very little, if any, mutagenic activity. Existing studies also demonstrate that MIBK is not teratogenic and exhibits low reproductive toxicity. As with MEK, MIBK has not been tested specifically for carcinogenicity because data on its structure and metabolism, subchronic health effects, and genotoxicity indicate that it is highly unlikely to pose a cancer risk. If you are aware of any evidence that either MEK or MIBK is carcinogenic, please notify the panel. If not, we request that you publish a correction in order to set the record straight. Inaccurate and misleading information, even from a single publication, can have a significant impact. We therefore ask that you take the steps necessary to correct the false impression that has been created by your April 22, 1993, publication. If you have any questions or wish to provide information on either of these these compounds, please contact Barbara Francis, manager of the Ketones Panel, at (202) 887-1314.