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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

Half-life in water: 100h (at 20°C)
Half-life in sediment: 79 days (at 12°C)

Key value for chemical safety assessment

Half-life in freshwater:
100 h
at the temperature of:
20 °C
Half-life in freshwater sediment:
79 d
at the temperature of:
12 °C

Additional information

A die-away study in river water was carried out with radio labelled HHCB (Schaefer, 2005). The test was carried out at a concentration of 5 µg/l in a sample of river water with activated sludge added at a level of 10 mg AS/l. This test revealed that in the degradation process HHCB is transformed to more polar metabolites. The primary biodegradation on day 28 was circa 60%. According to the kinetic analysis the overall half-life of the parent is 100 hours.

The fate of 14C-HHCB in sediment was studied in microcosms according to protocols described in documents from the U.S. Food and Drug Administration of 1987 (Envirogen, 1998). Samples were taken from the sediment of the Delaware River in central New Jersey. 14C-Radiolabeled HHCB in sediment was almost completely degraded after one year and significant amounts of polar metabolites were found. Only 4 % of the initial HHCB concentration remained in the river sediment. Estimated rate constants and half-lives were 0.0088 d-1 and 79 days for river sediment.

For the environmental risk assessment, conservative biodegradation rate constants (expressed as half-life times) of 60 days in surface water (20 °C) and 150 days in the sediment compartment (12 °C) are used in accordance with the RAR for HHCB.