4-methylpentan-2-one

Toxicity to microorganisms

Key value for chemical safety assessment

EC50 for microorganisms:

275 mg/L

Additional information

MIBK being readily biodegradable, it is considered that the substance is not toxic to bacteria. Nevertheless, several bibliographic references confirm this point. Different bacteria strains were tested for different period of time by Bringmann at the end of the 70's and early 80's. The most sensitive species is Pseudomona putida for which an EC50 -16h of 275 mg/L has been measured.

Growth inhibition was measured as relative turbidity at the end of the study (16 h). 

This demonstrates the low toxicity of MIBK. The toxicity to microorganisms data for MIBK could also be partially read across from MIBC. Metabolic data demonstrate that methyl i-butyl carbinol is rapidly and extensively converted to the methyl i-butyl ketone via oxidation of the alcohol functional group by alcohol dehydrogenase in the liver. Methyl i-butyl ketone is subjected to further oxidative metabolism (hydroxylation) by the hepatic microsomal mixed function oxidase system to produce 4-hydroxymethyl-4-methyl-2-pentanone (i.e., diacetone alcohol), which is the major metabolite formed from both methyl i-butyl carbinol and methyl i-butyl ketone exposures. Thus, methyl i-butyl ketone may be used as an appropriate surrogate for methyl i-butyl carbinol and vice versa considering that the alcohol is rapidly metabolized to the ketone and that exposure to either substance ultimately results in the rapid formation of diacetone alcohol. One study was performed to assess the toxicity of MIBC to microorganisms (i.e.: activated sludge of a predominantly domestic sewage). The study was conducted according to OECD Guideline 209 with no exceptions. The 3-hour EC50 for MIBC was reported to be greater than 100 mg/L.