Registration Dossier
Registration Dossier
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EC number: 200-861-4 | CAS number: 75-33-2
Toxicity to aquatic algae and cyanobacteria
Administrative data
Link to relevant study record(s)
Description of key information
The results obtained with isopropylmercaptan indicate that this substance is harmful to algae.
Key value for chemical safety assessment
- EC50 for freshwater algae:
- 21.9 mg/L
- EC10 or NOEC for freshwater algae:
- 1.2 mg/L
Additional information
Kley (2011) is a GLP-compliant, 72h, static and freshwater study following OECD guideline 201 using closed vessel design. Validity criteria were fulfilled but the concentration was not maintained during the test period. At the start of the test 38 % of the nominal test concentrations were found (mean value of test media of nominal 3.2 to 100 mg test item/L). After 72 hours test duration, the measurement of the test samples failed, therefore, all reported results refer to nominal and initial mean concentrations. The high loss of test item is most likely explained with adsorption effects and the high volatility of the test item. Presumably, the test item was lost during the sampling procedure, since the recoveries of the freshly prepared test media samples is already reduced.
Based on the definitive test results, it can be concluded that propane-2 -thiol is harmful to algae.
Based on nominal test concentrations the 72h ErC50 value was calculated to be 54.1 mg test item/L. Based on the initial mean measured concentrations of the test item the 72h ErC50 was calculated to be 21.9 mg/L.The72h NOEC was determined to be 3.2 and 1.2 mg test item/L based on nominal test and initial measured concentrations, respectively.
A study has been performed with an analogue substance: 2 -methylpropane-2 -thiol. Thiebaud (1999) is a GLP compliant proprietary study, which follows the OECD guideline 201. Concentrations were not maintained within 80% of the initial concentrations so a geometric mean was used as according to OECD 201, calculated from the initial and final concentrations. This study is considered reliable and suitable for use as a key study for this endpoint. The growth rate EC50 of 2-methylpropane-2-thiol was 24 mg/l and the NOEC was 6.41 mg/l.
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