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No acute toxic effects on micro-organisms, aquatic invertebrates, and fish were observed in the guideline studies.

Algae showed effects below 50% at 0.80 mg/L (de Groot 2004b) in the range of the environmental solubility of DCDPS, i.e. 0.86 mg/L (Boelhouwers 2004). By correction of possible hormesis effects using extrapolation with appropriate curve fitting software no 50% adverse effects are reached until the level of water solubility. DCDPS is thus regarded as not acute toxic to the aquatic life.

Chronic exposure of algae and daphnids showed effects. The lowest observed effect concentration LOEC is reported to be 0.48 mg/L in algae (NOEC 0.28 mg/L de Groot 2004b). This indicates that algae represent the most sensitive trophic level. The chronic LOEC for daphnids is reported to be 0.55 mg/L (NOEC 0.32 mg/L, de Groot 2004a). However no LOEC for fish was determined it is assumed that they represent the fewest sensitive organism group. This is based on the observation that they did not exhibit acute toxicity at extensively high exposure far above the water solubility level of DCDPS.

The fish were exposed for 35 days in the course of a bioaccumulation study (NITE 2002). The DCDPS-level in this study, 0.05 mg/L, was below a toxic concentration. Analogue to the OECD threshold approach (for acute fish toxicity testing) this observation is regarded as a limit study. Thus the NOEC for assessment is assigned to this concentration.