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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

According to the REACH regulation ANNEX IX column 2, studies on the biodegradation in water and sediment need not be conducted if the test item is readily biodegradable.

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Additional information

According to the REACH regulation ANNEX IX column 2, studies on the biodegradation in water and sediment need not be conducted if the test item is readily biodegradable.

However, data are available for the fate of alcohol ethoxysulfates and are presented below.

In a test conducted to OECD 314 C the alcohol ethoxysulfate C14E3S was incubated in anaerobic digester sludge. 91% of the radiolabelled test substance was mineralized after 21 hours. Alkylethoxylate C14EO3 occurred together with the disappearance of the parent compound. Therefore it is proposed that the initial step in anaerobic degradation is sulfatase mediated hydrolysis of the sulfate group. The half-life for primary degradation was determined as 2.6 hours (Federle & Nuck, 1994, P&G). This result was supported by a similar test with alcohol ethoxysulfate C14E3S according to OECD 314 C. After 14 days 88% of the applied radioactivity was recovered in evolving gases. The half-life was determined to be 0.67 d (Federle & Nuck, 1994, P&G).

In two die-away studies according to OECD guideline 314 A and 314 B (Federle & Itrich, 1998, P&G) alcohol ethoxysulfates were removed from the exposure matrix to an extent of 95.2% and 88.4% after 24 hours (mineralization and incorporation into solids). The degradation rates determined for mineralization were 0.033 min-1 and 0.003 min-1, respectively. 98.8% of the test substance was removed from raw sewage after 24 hours. 65.7% were converted to a metabolite and 33.1% were incorporated into solids.

Marks (1994, P&G) investigated the degradation of alcohol ethoxysulfates according to OECD 314 B. In activated sludge treating predominately domestic sewage under aerobic conditions radiolabeled C14E3S was mineralized to 88.3% after 28 days of exposure. Therefore, the rate constant for biodegradation in activated sludge was 1.75 d-1.

In surface water (89% river water, 10% sewage treatment plant effluent and 1% activated sludge) 39.7% of alcohol ethoxysulfates were mineralized after 48 hours. 60.3% were non extractable residues (Federle & Itrich, 1996, P&G). Degradation rates could be calculated as 0.97 h-1 for primary degradation, 0.061 h-1 for ultimate biodegradation and 0.028 h-1 for mineralization.

In another simulation test in surface water according to OECD guideline 314 D 87.5% of theoretical radiolabeled 14CO2 were observed after 28 days of exposure. The degradation rate constant derived for biodegradation of C14E3S was 0.38 d-1 (Marks, 1994, P&G).

Taking into account all available results obtained from the different simulation tests conducted according to OECD guideline 314 it was demonstrated, that alcohol ethoxysulfates are not persistent in water and are ultimately removed under aerobic and anaerobic conditions.