A mixture of: α-3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionyl-ω-hydroxypoly(oxyethylene); α-3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionyl-ω-3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionyloxypoly(oxyethylene)

Biodegradation in water and sediment: simulation tests

Description of key information

The primary degradation from water and sediment goes rapidly.

Additional information

According to regulation (EC) No 1907/2006, Annex XI, paragraph 1.5., substances whose physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity may be considered as a group, or "category" of substances. Environmental effects or environmental fate may be predicted from data for reference substance(s) within the group by interpolation to other substances in the group (read-across approach). The substance consists of two main components, a diester (35.4 % ) and a monoester (51.0 %). Both of these components are uvcb substances with varying side and middle chain lengths, respectively.

An analogous substance (EC No. 407-000-3) is available with close structural similarities to the monoester component. Its physico-chemical properties, the toxicological and ecotoxicological profile as well as the environmental fate are comparable to the monoester of EC No. 400-830-7. Therefore, read-across to EC No. 407-000-3 is scientifically justified for physico-chemical, the toxicological and ecotoxicological profile as well as environmental fate.

 

In a study on EC 407-000-3 following OECD guideline 308 the degradation in water/sediment systems was investigated under aerobic and anaerobic conditions (Ciba 851895 and 851896).

Under aerobic conditions the substance migrated rapidly from the water phase into the sediment, with a half-life of about a day. In the sediment a mean half-life of about 8 days was calculated. Several degradation products were determined. The main degradation product resulted from ester hydrolysis of the substance to 3-[3-tert-butyl-5-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] propionic acid. This metabolite degraded with a half-life of about 40 to 64 days. The mineralization of the substance was low (approx. 1 %) and organic volatile compounds were not formed. A part of the test item got stably bound to the immobile organic matter of the sediment.

In conclusion, in aerobic aquatic systems, the test substance (EC 407-000-3) is initially transformed to the hydrolysis product 3-[3-tert-butyl-5-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] propionic acid followed by degradation to numerous minor fractions and incorporation of residues into the organic matter of the sediment. The mineralization was insignificantly low.

 

Under anaerobe conditions similar results occur. The parent compound disappeared rapidly from the aquatic systems (half-life of 20.4 days) to form 3-[3-tert-butyl-5-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] propionic acid and bound residues. As under aerobic conditions the mineralization of the metabolite was insignificantly low. The results of this study indicate that the test substance (EC 407-000-3) rapidly disappears from aquatic systems to from 3-[3-tert-butyl-5-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] propionic acid and low amounts of bound residues.

 

In conclusion, under aerobic conditions the test substance (EC 407-000-3; which is structurally highly similar to the monoester of EC 400-830-7) degrades to 3-[3-tert-butyl-5-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] propionic acid followed by degradation to numerous minor fractions and incorporation of residues into the organic matter of the sediment. The DT50 values for 3-[3-tert-butyl-5-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] propionic acid are 40 to 64 days. Under anaerobic conditions EC 407-000-3 rapidly disappears from aquatic systems to form 3-[3-tert-butyl-5-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] propionic acid and bound residues. The mineralization was insignificantly low.