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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The toxicity to aquatic algae was assessed in a test with Pseudokirchnerella subcapitata (reported as Selenastrum capricornutum) according to OECD 201 (2010):
ErC50 (72h) = 100.4 mg/L, EyC50 (72h) = 23.86 mg/L
NOErC = 6.0 mg/L, NOEyC = 6.0 mg/L
LOErC = 9.7 mg/L, LOEyC = 9.7 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:
100.4 mg/L
EC10 or NOEC for freshwater algae:
6 mg/L

Additional information

The acute toxicity to aquatic algae and cyanobacteria of tributyl citrate was tested according to OECD guideline 201 and EU Method C.3 in a static dose-response Algal Growth Inhibition Test with the freshwater green algae Pseudokirchneriella subcapitata (formerly known as Selenastrum capricornutum) as test organism (2010). The study was conducted under certificated GLP compliance. The concentrations that have been tested were 4.3, 9.4, 21, 45 and 100 mg test item/L (mean measured) and a control (test water without addition of the test item). For the determination of the test concentrations a range-finding test was performed. However, concentrations above the limit concentration (nominal 100 mg test item/L or limit of solubility) described by the OECD 201 Guideline for Testing of Chemicals, Section 2 from March 2006 were not tested. The study encompassed 6 treatment groups (5 dose rates of the test item, control) with three replicates per test concentration and six replicates for the control. At test start 50 mL of the test concentrations were inoculated with 5000 algal cells per mL test medium. These cells were taken from an exponentially growing pre-culture, which was set up 4 days prior to the test start under the same conditions as in the test. Based on the calculated cell densities, the 72-hour ErC50 and the 72-hour EyC50, the corresponding EC10 values and where possible their 95 %-confidence limits were calculated by Probit analysis. All other calculations were carried out using a statistical software programme. Analysis of the yield and growth rate of the algal population within 72 h exposure period gave the following results:

The 72-hour ErC50 value was calculated to be 100.4 mg test item/L and the 72-hour EyC50 was calculated to be 23.86 mg test item/L. The 72-hour NOErC was determined to be 6.0 and the associated 72-hour LOErC is 9.7 mg test item/L. The 72-hour NOEyC was determined to be 6.0 and the associated 72-hour LOEyC is 9.7 mg test item/L.