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Two screening tests of the "ready" biodegradability of trimellitic anhydride (TMA) are available.

In the first (Lebertz, 1991a) TMA was tested for ready biodegradability according to the 1984 OECD 301B (Sturm Test) procedure, at concentrations of approximately 10 and 20 mg/L. The measured CO2 yield from TMA exceeded 60% of theoretical at both concentrations and the 60% threshold was crossed within the "10-day window", i.e. within 10 days of CO2 production reaching 10% of theoretical.

In the second (CITI, 1988), TMA (100 mg/L) was tested for biodegradability by the Chemicals Inspection and Testing Institute of Japan to fulfil the requirements of the Japanese Chemical Substances Control Law. A composite inoculum (applied at 30 mg suspended solids/L) originating from ten specified locations around Japan, not deliberately adapted to the test substance, fed with peptone and glucose prior to use and renewed at regular intervals (see OECD Guideline 301C 1984 and 1992 for details) was employed as standard practice at CITI for these investigations. An automated respirometer was used to make continuous measurements of biochemical oxygen demand (BOD) and recorded BOD was compared to the theoretical oxygen demand (ThOD) calculated assuming the complete mineralisation of TMA to its terminal oxidation products. This comparison provides a measure of ultimate biodegradation. Measured BOD expressed as %ThOD reached 96% within 28 days in this study. Confirmatory indications are provided by total organic carbon (TOC) analyses - this non-specific technique showed 99% loss of the test substance (ultimate degradation) and are consistent with the figure of 96% for ultimate biodegradation based on BOD measurement.

Both studies demonstrate that TMA is readily biodegradable and this result signifies that TMA will degrade rapidly and completely, without the formation of stable metabolites, under aerobic conditions in a variety environmental compartments (aquatic and terrestrial) and that extensive biodegradation may be anticipated in aerobic biological wastewater treatment processes. This (in addition to exposure considerations) obviates the need for studies of the degradation of TMA in water/sediment systems or in soil.

The screening test inherent to the biodegradability of trimellitic acid (TMLA) was calculated using the software BIOWIN v4.10.

The results indicate that the above substance is expected to be readily biodegradable.

Therefore both trimellitic anhydride and acid are not persistent (not P).