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Toxicity to microorganisms

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Description of key information

The influence of InCl3 on the respiration rate of activated sludge was investigated after a contact time of 3 hours. Five concentrations were tested: 46,100,220,460 and 1000 mg/L. The pH was adjusted to 7.2. No statistically significant inbition of the respiration rate was recorded at and below 1000 mg InCl3/L. This is equivalent to 516 mg In/L. The study met the acceptability criteria prescribed by the protocol and was considered valid.

Key value for chemical safety assessment

EC50 for microorganisms:
516 mg/L
EC10 or NOEC for microorganisms:
516 mg/L

Additional information

There were two test results available. In a first test, the respiration slugde study was carried out without pH adjustement. This resulted in a NOEC of 460 mg InCl3/L and an EC50 of 680 mg InCl3/L. The pH in the controls and substance series, before addition of sludge was 7.3 at 10 mg/L and decreased to 2.9 at 1000 mg/L. After 3 hours exposure period the pH in the Indium trichloride series was 7.8 at 10 mg/L and decreased to 3.4-3.7 at 1000 mg/L.

In a second test, the pH was adjusted to 7.2. This resulted in a NOEC of 1000 mg/L and an EC50 of >1000 mg InCl3/L. As pH was very low in the pH non adjustement treatment, the results of the pH adjusted treatments were taken to set the PNEC for STP. The NOEC was 1000 mg InCl3/L or 516 mg In/L.