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Environmental fate & pathways

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Dechlorane Plus was investigated for biodegradation in two non-standard tests. In a first study by Boudreau et al. (1973) the disappearance of the substance was measured analytically (GC-EC) over a 21d-period with a domestic activated sludge (non-adapted) being present. Initial nominal test substance concentrations of ca. 0.01 mg/l, ca. 1 mg/l, ca. 10 mg/l and ca. 100 mg/l (active ingredient) were used (stock solution prepared in acetone and precipitation was observed, resulting in measured concentrations of 0.008 mg/l, 0.46 mg/l, 8.0 mg/l and 82 mg/l). Water samples were obtained on days 0, 7, 14 and 21. Concentrations did not decrease over the exposure time, and thus no biodegradation was observed in the study. No positive controls and no negative controls were included in the study.

In a second experiment by Chou et al. (1979) radiolabelled Dechlorane Plus was investigated for biodegradation. The radiolabelled test item was incubated with sewage treatment plant sludge under aerobic or anaerobic conditions for 2 or 6 weeks at two nominal concentrations of 218 and 872 ng/ml. Parallel cultures, autoclaved to kill the sludge bacteria, served as negative controls. The water samples were extracted, and the radioactivity was determined by liquid scintillation. Degradation was determined as loss of radioactivity. No loss of radioactivity was seen after 2 weeks of incubation at aerobic and anaerobic conditions. After 6 weeks of incubation, the recovery of radioactivity at aerobic conditions was 42.9% at the low concentration and 0.16% at the high concentration when compared to 92.1% in the sterile negative control at the high concentration. After 6 weeks of incubation at anaerobic conditions, the recovery of radioactivity was 87.5% at the low concentration and 84.1% at the high concentration, when compared to 88.4% in the sterile negative control at the high concentration. Volatilisation of the test substance causing reduction of radiolabelled material is unlikely, given the physic-chemical properties of the substance (melting point >300 °C and vapour pressure considered negligible), but adsorption to sludge or bacteria cannot be excluded. Also the position of radiolabelling in the molecule is not described. Thus, the findings have to be seen with caution and cannot be considered as proof for biodegradation. Hence, the substance is considered non-biodegradable.

Studies on biodegradation in water and/or soil are not available.