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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

ErL50 (72h) = 24 mg/L for Scenedesmus subspicatus (OECD 201), read across
NOEL (72h) = 10 mg/L for Scenedesmus subspicatus (OECD 201), read across

Key value for chemical safety assessment

EC50 for freshwater algae:
24 mg/L
EC10 or NOEC for freshwater algae:
10 mg/L

Additional information

Since no data on the toxicity of Zinc O,O,O',O'-tetrabutyl bis(phosphorodithioate) on aquatic algae are available, an analogy approach using the structurally similar substance Phosphorodithioic acid, mixed O,O-bis(1,3- dimethylbutyl and iso-Pr) esters, zinc salts (CAS 84605-29-8) has been applied. Further justification is given within the endpoint summary 6.1 and within the analogue justification section 13.

For the analogue substance one study is available, conducted according to OECD 201 with the green algae Scenedesmus subspicatus as test organism (Vryenhoef, 2005). Following a preliminary range finding test, the algae were exposed to Water Accommodated Fractions (WAF) of test material over a range of nominal loading rates of 10, 20, 40, 80, and 160 mg/L (nominal) for 72 hours under constant shaking. After 72 hours exposure 50 % growth inhibition was observed at a concentration of 24 mg/L (loading rate). The No Observed Effect Loading rate was 10 mg/L.