Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

According to the two valid studies performed on trimellitic anhydride (TMA), analogue of the registered substance trimellitic anhydride mono-chloride (TMAC), following OECD guidelines 301 B and 301 C, the registered substance is readily biodegradable.

Additional information

One of the three available studies was performed on the registered substance trimellitic anhydride mono-chloride (TMAC, target substance), while the two others were performed on its analogue trimellitic anhydride (TMA, source substance).

The first disregarded study (Environmental Biological Life Science Research Center, 1996) was performed on the registered substance trimellitic anhydride mono-chloride (target substance), according to a test similar to MITI test. As one of the validity criteria was not fulfilled as the difference between extremes degradation values of replicates at the end of the test were more than 20%, the study is considered as not reliable and was disregarded.

Trimellitic anhydride (source substance) was tested for ready biodegradability by two respirometric methods where the degradation "pass" level that conventionally represents complete mineralisation is 60%.

In the first biodegradation study (Lebertz, 1991) trimellitic anhydride was tested for ready biodegradability according to the 1984 OECD 301B (Sturm Test) procedure, at concentrations of approximately 10 and 20 mg/L. 98.7% and 77.4% degradation occurred within 28 days at concentrations of 10 and 20 mg trimellitic anhydride/L respectively and the 60% pass level was exceeded within 7 days. Recovery of CO2 provides a direct and unambiguous indication of the mineralisation of the test substance.

In the second biodegradation study (CITI, 1988) of reliability 2, 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 trimellitic anhydride 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. The pass-level of 70% was exceeded.

These results show that trimellitic anhydride (rapidly hydrolysed into trimellitic acid under test conditions) is readily biodegradable.

Both studies demonstrate that trimellitic anhydride (TMA) is readily biodegradable and this result signifies that trimellitic anhydride 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.

Due to close strutural similarity between the source and target substances, these results indicate that the registered substance (TMAC, target substance) is expected to be readily biodegradable.