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Environmental fate & pathways

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The threshold that triggers the need to investigate a potential bioconcentration/bioaccumulation tendency experimentally is a log10 Kow value greater than or equal to 3.0.

The log Kow of trimellitic anhydride (TMA), determined experimentally according to the OECD 117 (HPLC method) is 0.06.

The log Kow of trimellitic acid (TMLA), determined experimentally according to OECD 107 (Shake Flask method) is 0.54.

The US EPA's KOWWIN model predicts a log Kow of 1.95 for TMA and a log Kow of 0.95 for its hydrolysis product TMLA.

Considering all the charge-state forms of trimellitic acid dissolved in water and in octanol, a LogD (distribution coefficient) was estimated taking account for the pH dependence of the substance in aqueous solution.

For the environmental and PBT assessments, trimellitic acid was therefore considered more significant, with logD= -4.83.

TMLA is not expected to remain stable in the form of the free acid under environmental conditions. Aquatic ecotoxicology studies have been conducted with TMA after converting it to the sodium salt(s) of TMLA .This is considered representative of the likely behaviour of TMA (TMLA) in the environment.

The log Kow of ionised forms of TMLA relevant to considerations of environmental exposure will be lower still. All these log10 Kow values lie below the trigger of 3.0 and both TMA and TMLA are therefore expected not to exhibit significant bioconcentration or bioaccumulation tendencies.

It may be concluded that both trimellitic anhydride and acid are not bioaccumulative (not B).