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Ecotoxicological information

Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the substance is found to be readily biodegradable and the applied test concentrations are in the range of concentrations that can be expected in the influent of a sewage treatment plant
Justification for type of information:
JUSTIFICATION FOR DATA WAIVING
According to column 2 of REACH Annex VIII, the study does not need to be conducted on microorganisms because the substance is found to be readily biodegradable and the applied test concentrations (2 mg/L) are in the range of concentrations that can be expected in the influent of a sewage treatment plant ( 1.60E-19< PEC stp< 2.66E-02 mg/L).
Reason / purpose:
data waiving: supporting information

Description of key information

Weight of evidence: One valid ready biodegradability study on l-limonene and one valid activated sludge respiration test on dipentene multi-constituents (48.4% dl-limonene) were available to assess the toxicity of l-limonene to microorganisms. The most sensitive value, a NOEC of 2 mg/L derived from the ready biodegradability test, was considered as the reliable value for risk assessment purposes.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
2 mg/L

Additional information

According to column 2 of REACH Annex VIII, the study does not need to be conducted on microorganisms because the substance is found to be readily biodegradable and the applied test concentration (2 mg/L) was higher that can be expected in the influent of a sewage treatment plant ( 1.60E-19< PEC stp< 2.66E-02 mg/L).

According to ECHA, Chapter R.7b, Endpoint specific guidance (2008), the information content of a ready biodegradability test can be used to derive a NOEC. In the case of l-limonene, the close bottle test using unadapted domestic sludge (5989-54-8, Biodegradation in water: screening tests, van Ginkel, 2010, RS, K) according to OECD 310 (2006) and ISO 10707 (1994) fulfills the following requested conditions: the compound is found to be readily biodegradable and the test substance concentration (2 mg/L) was not above the solubility limit of l-limonene (12.3 mg/L). A toxicity control that shows good degradation of the positive control substance (sodium acetate) in the presence of the test substance haven't been included in this test because it was believe that possible toxicity of l-limonene to microorganisms degrading acetate was not relevant. However inhibition of the endogenous respiration of the inoculum by the test substance was not detected and therefore, no inhibition of the biodegradation due to the "high" initial concentration of the test substance is expected. This hypothesis is reinforced by the result of a 3 hours acute toxicity study performed in accordance with the OECD guideline 209, on unadapted domesticactivated sludge exposed to Dipentene multi-constituent (dl-limonene purity was 48,4%) at nominal concentrations of 0 (control), 8.45, 16.9, 33.8, 67.6, 135.2, 270.4, 540.8 mg/L under static conditions.

The EC50 and EC10values for the respiration rate inhibition were 209 and 18 mg test item/L, respectively and the test concluded that the test item was not harmful to activated sludge. In conclusion a NOEC of 2 mg/L corresponding to a good degradated tested concentration can be derived from the ready biodegradability test for risk assessment purposes.