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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

Description of key information

Key value for chemical safety assessment

Additional information

There are no measured data for toxicity of TOPP to microorganisms. However, it is not considered necessary to derive a PNEC or conduct risk characterisation for TOPP in biological WWTP (waste water treatment plant) for the following reasons:

-  TOPP (and the majority of its constituents) are naturally-occurring and well tolerated by environmental organisms

- TOPP has been reliably demonstrated to be readily biodegradable by activated sludge cultures

- Gscheidmeier and Fleig (1996) reported that below the solubility limits of its constituents, TOPP does not present a hazard to biological wastewater treatment plants     

           

It is therefore very unlikely that TOPP would cause inhibitory effects on microorganisms present in WWTP.

This conclusion is supported by available data that was reported for hydrocarbons, terpene processing by products (CAS 68956-56-9) on the ECHA disseminated dossier page. Hydrocarbons, terpene processing by products (CAS 68956-56-9) has a reported Activated Sludge Respiration Inhibition (ASRI) 3 hour EC50 values of 365 mg/l and 579 mg/l. These values are for two different batches of the substance.

Also, the toxicity of terpineol to microorganisms was obtained as part of a toxicity control in an OECD 310 test guideline. The activated sludge which was obtained from a wastewater treatment plant treating predominantly domestic wastewater, was exposed to about 64.8 mg/l sodium acetate (positive control) with and without addition of 25.7 mg/l test substance (terpineol). Oxygen depletion in both solutions was measured and compared. There was no inhibition of the degradation of sodium acetate by the addition of the test substance. In addition, terpineol was considered to be non-toxic to micro-organisms as inhibition of the endogenous respiration of the inoculum was not detected during the test. Their NOEC value for microorganism toxicity is 25.7 mg/l.

These data, along with the observation that there was no inhibition to microorganisms in ready biodegradation tests for the whole substance and a number of TOPP constituents, support the expectation that microorganisms in the environment would be adapted to degrading these substances.