5-amino-o-cresol

Long-term toxicity to aquatic invertebrates

Description of key information

The test item 5-amino-O-cresol was tested on the reproduction of Daphnia magna. No statistically significant effects on adult survival or adult growth were observed and the NOEC for survival and growth was 0.78 mg/L, which is the highest tested concentration.  Adverse effects were observed on the juvenile production and a NOEC reproduction of 0.24 mg/L and a LOEC of 0.78 mg/L was obtained. Given the general decline in measured concentrations during daphnia exposure to the test item, the results are expressed on time-weighted mean measured concentrations.        

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.24 mg/L

Additional information

A 21-day Daphnia magna reproduction study was conducted to determine the effects of exposure to the test substance on Daphnia magna reproduction. The study was conducted in accordance with the OECD Chemicals Testing Guideline No.211 and following the GLP

The definitive test was conducted at the nominal concentrations of 0.010, 0.032, 0.10, 0.32 and 1.0 mg/L. A control group was also included. The test was conducted using a semi-static design with daily renewal of the test media.

Ten replicate test vessels were prepared for the control and each test concentration. A single juvenile Daphnia magna (<24 hours old) was added to each test vessel. On renewal occasions, parental animals were transferred into freshly prepared test media. Any juveniles remaining in old test media were counted and the number of juveniles produced per parental animal on any day during the 21-day study duration was recorded. At the end of the test, carapace lengths of all surviving parental Daphnia magna were measured.

Chemical analysis of the freshly prepared media showed measured concentrations to range from 45% to 117% of nominal. Most results were outside the 80% to 120% of nominal value. This was considered to be due to the unstable nature of the test substance. Analysis of the old media showed measured concentrations to range from 31% to 85% of nominal. Given the general decline in measured concentration over each 24-hour renewal period, it was considered justifiable to base the results on time-weighted mean measured test concentrations. These were calculated to be 0.0065, 0.021, 0.071, 0.24 and 0.78 mg/L.

No statistically significant effects on adult survival or adult growth (based on final length) were observed between the test concentrations and the control. The NOEC and LOEC values for adult survival and growth were therefore considered to be 0.78 and >0.78 mg/L, respectively.

Statistically significant differences were observed, compared to the control, for reproduction. The NOEC and LOEC values for reproduction were therefore considered to be 0.24 and 0.78 mg/L, respectively. The 21-Day EC50 value for reproduction was estimated to be 0.52 mg/L.

The validity criteria were satisfied, and therefore the results of the reproduction test are considered to be valid.