Registration Dossier
Registration Dossier
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EC number: 204-506-4 | CAS number: 121-91-5
Toxicity to microorganisms
Administrative data
Link to relevant study record(s)
Description of key information
The effect of isophthalic acid (IPA) on the respiration of activated sludge was investigated according to OECD 209 in a reliable (Klimisch 1) study performed to GLP (Lebertz, 1991). IPA was applied without pre-treatment at nominal concentrations of 500, 1000, 2000 and 4000 mg/L, which all exceeded the water-solubility limit of the test substance. The 3-h EC50 based on respiration inhibition was 617.1 mg IPA/L.
Key value for chemical safety assessment
- EC50 for microorganisms:
- 617.1 mg/L
- EC10 or NOEC for microorganisms:
- 158.3 mg/L
Additional information
The 3 -h EC50 of isophthalic acid, based on inhibition of respiration of activated sludge, was 617.1 mg/L. Inhibition, relative to the untreated control, was observed at concentrations >/= 500 mg/L and the EC5 was 158.3 mg/L. All the concentrations applied exceeded the water-solubility of the test substance. No pH measurements were reported; consequently it is uncertain whether a lowering of pH may have caused or contributed to the observed effect.
Nevertheless, it may be concluded that isophthalic acid presents low toxicity to aquatic microorganisms and to biological waste water treatment processes.
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