This notice is brought to you by the OEHHA.



The California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA) intends to list the chemical methyl isobutyl ketone (MIBK) as known to the State to cause reproductive toxicity (developmental endpoint) under the Safe Drinking Water and Toxic Enforcement Act of 19861.  This action is being proposed under the authoritative bodies listing mechanism2.


Methyl isobutyl ketone meets the criteria for listing as known to the State to cause reproductive toxicity under Proposition 65, based on findings of the U.S. EPA (U.S. EPA, 2003a; U.S. EPA, 2003b).


In 2003, U.S. EPA updated its online Integrated Risk Information System (IRIS) entry for methyl isobutyl ketone (U.S. EPA, 2003a).  The inhalation reference concentration (RfC) was based on developmental toxicity manifested as reduced fetal body weight, skeletal variations, and increased fetal death in mice, and skeletal variations in rats.  This meets the criterion in Section 25306(d)(1) that the chemical “has otherwise been identified as causing …reproductive toxicity by the authoritative body in a document that indicates that such identification is a final action”.


OEHHA is requesting comments as to whether methyl isobutyl ketone meets the criteria set forth in the Proposition 65 regulations for authoritative bodies listings.  In order to be considered, OEHHA must receive comments by 5:00 p.m. on MONDAY October 7, 2013.



For more information and the full notice please refer to the OEHHA link above.


Please contact Nexreg with any questions regarding Prop 65.