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Category name:
1,2-butadiene read across

Justifications and discussions

Category definition:
C4 alkene hydrocarbons, read-across framework for 1,2-butadiene
Category description:
1,2-butadiene, 1-butene, 2-butene, 2-methylpropene, 1,3-butadiene
Category rationale:
The analogue approach is being applied to C4 hydrocarbons with one or two alkene (olefin) moieties, i.e. carbon-carbon double bonds. These substances are all gaseous at room temperature and pressure, and the inhalation route is expected to be the predominant, and only significant, route of exposure. The alkene moiety is susceptible to oxidation by cytochrome P450 isozymes (in particular 2A6 and 2E1) resulting in epoxide and diepoxide metabolites that may react with cellular nucleophiles. The epoxides may also be hydrolysed by epoxide hydrolase to diol metabolites, or react with glutathione, catalysed by glutathione-S-transferase. Hydrolysis and conjugation with GSH are considered to be routes of detoxification.