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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The adverse effects 1,3 -dichloro-4 -nitrobenzene towards the growth of aquatic algae are characterized by EC50(48 h) of 5.3 mg/L as well as a NOEC of 2.03 mg/L referring to the reduction of the growth rate (Currenta, 2009). Effective concentrations are based on the geometric mean of measured concentrations.

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Additional information

The study data were analysed on a 48 h basis, because the coefficient of variation between daily sectional growth rates over 72 h exceeded 35 %. As cell numbers increased well above 16-fold over 48 h, and all other validity criteria are met, this is an option explicitly covered by OECD TG 201 (2006) and EU method C.3 (2009).

Furthermore, effects based on the biomass were reported yielding more sensitive results than effects based on the growth rate. But, according to the Guidance Document R.7b (ECHA, 2008) results based on the biomass should not be used for assessment since biomass results depend on the growth rate of the species as well as the test duration and other elements of the test design. Thus, the results based on the biomass are not used for the hazard assessment.