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Environmental fate & pathways

Hydrolysis

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Description of key information

According to REACH Regulation 1907/2006, Annex VIII Column 2, hydrolysis studies are not necessary for substances that are readily biodegradable.  Since trimellitic anhydride has been shown to be readily biodegradable (Point 5.2.1), a study of its hydrolysis under a range of pH conditions is not required.  

Key value for chemical safety assessment

Half-life for hydrolysis:
0.1 h
at the temperature of:
40 °C

Additional information

Since trimellitic anhydride has been shown to be readily biodegradable (Point 5.2.1), a study of its hydrolysis under a range of pH conditions is not strictly necessary.

However, a study of the hydrolysis of the closely related substance, trimellitic anhydride acid chloride, has been performed in the context of the requirements for substances that may come into contact with food via packaging material. This study examined the behaviour of trimellitic anhydride acid chloride in unbuffered distilled water as a simple food simulant. Trimellitic anhydride acid chloride was found to hydrolyse completely at 40 °C in less than ½ hour to trimellitic acid and hydrogen chloride gas. Hydrolysis of the monomer was virtually instantaneous. Based on its close structural similarity, rapid hydrolysis is anticipated for trimellitic anhydride, which is also expected to undergo almost instantaneous conversion to trimellitic acid on contact with aqueous matrices in the environment and in vivo in exposed humans and other organisms.

This behaviour defines trimellitic acid (and its salts) rather than the anhydride as the entity relevant to exposure in the environment and also justifies the consideration of toxicology data provided by studies in which animals or test systems were administered trimellitic acid (bypassing the in vivo hydrolysis step) rather than the parent trimellitic anhydride polyester monomer.