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Hazard for aquatic organisms

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Conclusion on classification

Two studies are available on 4-acetoxystyrene: an acute daphnia study in accordance with OECD 202 and an algae study in accordance with OECD 201. These tests yielded the following results:

- daphnia 48h EC50 = 1.66 mg/L (nominal concentration)

- algae 72h EC50 (growth rate) = 2.45 mg/L (measured, geometric mean)

- algae EC10 = 0.715 mg/L (measured, geometric mean)

Based on the criteria described in CLP section 4.1.2, classification for acute aquatic hazard is not required as the available EC50 values are > 1 mg/L.

With regard to long-term aquatic hazard, the classification needs to be determined in two ways, and the most stringent outcome to be retained:

i) based on the available chronic data for algae. As the EC10 is in the range of 0.1 - 1 mg/L, and taking into account that the substance is readily biodegradable, classification as Chronic Cat. 3 is warranted.

ii) based on the available acute data. The EC50 values are in the range of 1-10 mg/L. However, taking into account that the substance is readily biodegradable and has a log Kow < 4, classification for long-term aquatic hazard is not warranted.

Adopting the most stringent classification determined by methods i) and ii), it can be concluded that 4-acetoxystyrene is to be classified as Chronic Cat. 3.