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Environmental fate & pathways

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The atmospheric oxidation half-life of terephthalic acid was estimated using the AOPWIN v1.91QSAR model available from the US EPA. The estimated atmospheric oxidation DT50 of terephthalic acid ranged from 8.65 days (default settings) to 12.97 days, estimated by applying the recommended northern hemisphere settings that are considered relevant in a European context.

Since terephthalic acid is readily biodegradable, a study of the hydrolysis behaviour of TPA is not required and has not been performed. Nevertheless, some insight is provided indirectly by a study of the toxicity of TPA to unicellular aquatic algae (Government of Japan, Ministry of the Environment 2003d). Terephthalic acid, dosed to aqueous algal growth test medium at a measured initial concentration of 19.0 mg/L, remained intact over the course of 72-h incubation at pH 7.8 +/- 0.3 and 22.3 +/- 0.1 degrees C. These data (DT50 > 3 days) provide evidence that TPA is not prone to rapid hydrolysis in the aquatic environment.

Similarly, no studies have been performed to investigate the phototransformation of terephthalic acid in water, however the results of the same algal study, in which TPA remained stable following continuous bright illumination for 72 hours, suggests that terephthalic is not prone to rapid photodegradation.

In summary terephthalic acid is generally resistant to physico-chemical degradation processes under the range of conditions likely to be encountered in the aquatc and terrestrial environment. Other data (see Point 5.2.1) show that terephthalic acid is readily biodegradable, with >60% mineralisation (oxidation to CO2) occuring within 5 days. Biodegradation may therefore be considered a more significant dissipation mechanism than physico-chemical processes tor TPA in the environment.