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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

The toxicity controls from the biodegradation studies on the xylene isomers indicate that the substances are not inhibitory to micro-organisms, with a 28 day NOEC of 16 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
16 mg/L

Additional information

Biodegradation tests were carried out on all three xylene isomers following OECD 301F guidelines using a mixed inoculum of non-adapted sludge and soil micro-organisms. In the toxicity control vessels, containing the individual xylene isomers with the reference substance sodium benzoate, none of the xylene isomers exhibited inhibitory effects on the micro-organisms. The 28 day NOEC (nominal concentration) is therefore 16 mg/L for m-xylene and 16.2 mg/L for o-xylene and p-xylene.

The studies by TNO (Oldersma 2004) and Volskay and Grady (1988) both follow OECD 209. TNO (2004) used p-xylene as the test substance, Volskay and Grady (1988) tested both o- and p-xylene. Each of the tests used a single test concentration approximating the limit of solubility of the test substance. The EC50 was not observed in any of the tests. The study by TNO reports a 3 hour NOEC of 157mg/L. Volskay and Grady (1988) report a 30 minute EC50 (respiration inhibition) of >175 mg/L for o-xylene and >198 mg/L for p-xylene and therefore the EC50 are above the limit of solubility.