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Environmental fate & pathways

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Additional information

A. BIODEGRADATION IN WATER - STATIC TESTS


1. OECD 301 Type Screening tests

Results from CO2evolution tests (OECD 301B) show that HYEQS is readily and ultimately biodegradable.

2. OECD 314A 14C-HYEQS Biodegradation test in Sewage Influent

The test was carried out at 3 different concentrations (50, 100, 250 µg/L). After 10d 64% of HYEQS was mineralized, 22% of radioactivity was associated with solids and 14% of HYEQS was still in the influent (mean of the three test concentrations). The kinetic for primary and ultimate degradation was calculated. The half-life for primary degradation was ca. 0.6d and for ultimate degradation ca. 2d.

3. OECD 314B 3H- and 14C-HYEQS Activated sludge Die Away Test

The test was run at a concentration of 1000 µg/L. Removal mechanism for both labelled substances were similar. Overall mass balance was 99.9% for 14C-HYEQS and 108% for 3H-HYEQS. Half-life of primary degradation was ca. 0.5h.The Half-life for mineralization of 14C HYEQS was ca. 41h and for 3H-HYEQS ca. 0.8h.The latter value is a more accurate (less conservative) rate of ultimate biodegradation. Only very polar metabolites remained at the end of the study.

4.OECD 314D 14C-HYEQS River Die Away Test

The test system consisted of: 89% river water, 10% sewage effluent, and 1% combined activated sludge liquor. Biodegradation was determined by Liquid Scintillation Counting of 14C-HYEQS over a 21 day test duration. HYEQS degraded rapidly with a half-life of 0.61 days for loss of parent. No parent compound remained by day 5.The half-life of mineralization was 7.7 days(CO2 evolved), and by day 21 80% of the test substance had evolved as CO2. After 21 days, 0% remained as parent, 11.6% was present as metabolites, 8.4% was present in the solids, and 80% was evolved CO2.
5. Biodegradation of HYEQS in Sediment
HYEQS Biodegradation in sediment was not tested. But a Half-life of HYEQS for soil (median of 3 soil half-lives) of 6.2d was derived from an OECD 307 Aerobic Soil transformation study (see IUCLID Section 5.2.3). Based on EChA REACH Guidance R.16 Environmental Exposure Assessment, Section R.16.4.4.5 (May 2008) the HYEQS Soil half-life of 6.2d may also be applied for aerobic sediment if no other data are available.

B. BIODEGRADATION IN SEWAGE TREATMENT PLANT – DYNAMIC TEST

OECD 303A HYEQS Simulation Test Activated Sludge Unit -Aerobic Sewage Treatment
HYEQS was continuously dosed into the activated sludge unit resulting in an influent concentration of 200 µg/L (137 µg/L C12 isomer, 50 µg/L C14 isomer). Influent and effluent concentration of HYEQS were measured daily using LC MS MS (LOQ C12 organic medium = 0.96 µg/L, C14 0.35 µg/L). Already one day after the start of the test the elimination of HYEQS was > 99.95% for C12 and 99.89% for C14. After 2d biodegradation of HYEQS was >99%. The biodegradation rate during the plateau phase was >99.9%.

C. BIODEGRADATION IN SOIL


OECD 307 14C-HYEQS Aerobic Transformation in Soil
The degradation rate of 14C-HYEQS in three aerobic soils was investigated during 62 days. 14C-HYEQS was applied at a rate of 0.45 mg a.i./kg soil dw. using sewage sludge as carrier. The application rate was determined from an exposure modelling using realistic use rates. Soil sampling was done after 2, 4, 8, 15, 28 and 62 days. Further sampling up to 120 days was not necessary due to rapid biodegradation. Significant amounts of radioactive carbon dioxide and bound residues were formed. The total mean recoveries of radioactivity were in the range of 91.2 to 94.9% for the three soils. From the measurements the following DT50 were calculated:

DT50 soil 1
 6.2 d (median of all 3 soils),
DT50 soil 2
 6.0 d,
DT50 soil 3 13.6 d.