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Zebra fish were exposed to nominal chloroprene concentrations of 0 (control), 6.25, 12.5, 25, 50 and 100 mg/L for 96 hours under semi-static conditions according to EU Method C.1 Acute toxicity to fish (2008). A complete set of analysis of new and 24 hour aged media was performed for the nominal 100 mg/L treatment. Geometric mean values were calculated for each 24 hour exposure period. The highest geometric mean value, 5.25 mg/L, was obtained during the final 24 hour exposure period. No mortality was observed in any of the test concentrations, therefore, the 96 hr LC50 was observed to >5.25 mg/L. No sub-lethal effects were observed on any of the treated fish, therefore the no-observed effect concentration (NOEC) was observed to be 5.25 mg/L (Caspars, 2010).

Daphnia magna were exposed to nominal chloroprene concentrations of 0 (control), 6.25, 12.5, 25, 50 and 100 mg/L for 48 hours under static conditions according to EU Method C.2 Acute toxicity for Daphnia (2008).  Geometric mean measured concentrations were 2.51, 5.42, 11.17, 21.68 and 45.17 mg/L in the nominal 6.25, 12.5, 25, 50 and 100 mg/L treatments. Based on mean measured concentrations the 24 hour EC50value was calculated to be 15.32 mg/L and the 48 hour EC50value was 11.17 mg/L. The no-observed effect concentration (NOEC) was observed to be 5.42 mg/L (Caspars, 2010).

The alga Scenedesmus subspicatus were exposed to nominal chloroprene concentrations of 0 (control), 3.2, 10, 32, 100 and 320 mg/L for 72 hours according to EU Method C.3 Freshwater Alga and Cyanobacteria, Growth Inhibition test (2009).  Geometric mean measured concentrations were 0.53, 0.1.37, 3.50, 11.19 and 39.00 mg/L in the nominal 3.2, 10, 32, 100 and 320 mg/L treatments. Based on mean measured concentrations the 72 hour ErC50value was calculated to be 20.4 mg/L (with 95% confidence intervals of 17.9 – 23.3 mg/L), the corresponding no-observed effect concentration (NOEC) was 1.37 mg/L. The 72 hour EyC50value was calculated to be 8.3 mg/L (with 95% confidence intervals of 6.3 – 10.0 mg/L), the corresponding NOEC was 0.94 mg/L. 

Young female Daphnia were exposed to the test item added to water at a range of concentrations (1.0, 3.2, 10.0, 31.6, 100.0 mg/L) for a period of 21 days (OECD 202). Defined concentrations of the test item led to a certain percentage reduction of the parthenogenetic reproduction rate at the end if the 21 day study period. The living offspring was counted daily along with the renewal of the test medium. The following reproduction rates were obtained at the end of the 21 day exposure period of the Daphnia reproduction test: R 21 (control) 100%; R 21 (1.0 mg/L) 74.1%; R 21 (3.2 mg/L) 97.5%; R 21 (10.0 mg/L) 87.2%; R 21 (31.6 mg/L) 67.0% and R 21 (100 mg/L) 54.7%. The no-observed effect concentration based on reproduction was <1. 0 mg/L. A SIDS Initial Assessment Report for 8th SIAM reviewed this report and concluded that "based on the concentration-response relationship and considering the biological variability, the NOEC for reproduction rate is 3.2 mg/L" (Shi, 2009).

Based on the data summarised above the lowest acute toxicity endpoint use for use in determining the freshwater aquatic PNEC is the fish acute 96 h LC50 value of >5.25 mg/L. Given that there is some debate over the NOEC from the Daphnia reproduction study, and that the lowest acute toxicity endpoint has been obtained from an acute toxicity study with fish it is considered appropriate to use the value of 5.25 mg/L together with an assessment factor of 1000 to derive the PNEC. The freshwater aquatic PNEC is therefore 0.00525 mg/L.

The marine aquatic PNEC is calculated using the 96 h fish LC50 value of >5.25 mg/L and applying an assessment factor of 10000, therefore the PNEC is 0.000525 mg/L.

The intermittent release water PNEC is calculated using the 96 h fish LC50 value of >5.25 mg/L and applying an assessment factor of 100, therefore the PNEC is 0.0525 mg/L.