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Ecotoxicological information

Long-term toxicity to fish

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Description of key information

Several long-term studies with the zebrafish Danio rerio have been performed, using TDCP as as test substance. None of these tests followed a standard guideline that is typically used for the log-term assessment of a chemical for fish. Wang et al (2015), however, conducted a 6 month experiment using freshly fertilized eggs as starting material and exposing these organisms continuously to TDCP for a six month period. This timeframe is longer than typical exposure periods that are provided in standard long term guidance documents. The lifestages that were tested cover the most sensitive phases of development. Finally, the evaluated endpoint “weight” is relevant for environmental assessment purposes.

A 6-month ECx of 4 µg/L was determined for D.rerio, with x situated between 10 and 20%. The ECHA Guidance Document on information requirements and chemical safety assessment (Chapter R.10: Characterisation of dose (concentration)-response for environment) does provide guidance on how to deal with studies that report ECx levels deviating from the classical 10%. More specifically, Table R.10-1 “Overview of toxicity test endpoints and guidance on derivation of L(E)C50 and NOEC values” : LOEC >10 and <20% effect: NOEC can be calculated as LOEC:2.

According to this methodology, a NOEC of 2 µg/L can be estimated for D. rerio (NOEC = LOEC:2 = ECx% : 2 = 4:2 µg/L = 2 µg/L)

All other studies resulted in NOEC-values that ranged from 4 to 300 µg/L; these studies covered shorter exposure periods, and both testing procedures as well as endpoints sometimes significantly deviated from conventional protocols that are typically used when assessing long-term effects to fish. None of the other studies with D.rerio generated a NOEC that was lower than the value derived from Wang et al (2015).

It should also be noted that the value of 2 µg/L is a factor of 500 lower than the NOEC value of 1 mg/L that was determined using a QSAR.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Effect concentration:
2 µg/L

Additional information

No long-term data for marine fish were identified.