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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Algal growth inhibition: ErC50= 65.3 mg/L; EyC50 = 61.4 mg/L; NOEC = 25 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:
65.3 mg/L
EC10 or NOEC for freshwater algae:
25 mg/L

Additional information

Algal growth inhibition to the unicellular freshwater green algaPseudokirchneriella subcapitatahas been investigated according to OECD/EU test methods. THPA was found to inhibit the growth after 72 hours exposure, EC50 values for inhibition of specific growth rate (ErC50) and yield (EyC50) being 65.3 mg/L and 61.4 mg/L, respectively. The potential for recovery from the observed effects was established.


In accordance with ECHA guidance oninformation requirements and chemical safety assessment, Chapter R.7b: Endpoint specific guidance, theErC50 endpoint is used in DNEL derivation. This is because use of values based on biomass cannot be applied to an analysis of results from a system in exponential growth without logarithmic transformation.