p-cresol

Long-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

fish early-life stage toxicity

Type of information:

experimental study planned

Justification for type of information:

Cresols are isomers and, thus ideally fulfill the recommended criteria of structural similarity. In its chemical structure, a cresol molecule has a methyl group substituted onto the benzene ring of a phenol molecule, by different arrangement of the -CH3 groups are three structural isomers possible. (ortho-cresol, meta-cresol and para-cresol). Of particular importance to environmental effects are the values for partition coefficient (log Kow), vapour pressure, water solubility and dissociation constant. The values of the isomers are very close together, resulting in the same environmental fate and behaviour. Further, with regard to the bioderadation behavior, all 3 cresols are readily biodegradable. Concerning aquatic toxicity of the cresols on aquatic species, a large number of experimental results from tests with fish, invertebrates and algae are available, indicating a similar toxicity of all isomers, with p-cresol being slightly more toxic in acute tests: Based on the similarities in the results mentioned above the read-across approach is therefore scientifically justified.

TESTING PROPOSAL ON VERTEBRATE ANIMALS FOR p-CRESOL

NON-CONFIDENTIAL NAME OF SUBSTANCE:
- Name of the substance on which testing is proposed to be carried out: p-Cresol [EC: 203-398-6; CAS: 106-44-5]
- Name of the substance for which the testing proposal will be used [if different from tested substance]: the substance itself.

CONSIDERATIONS THAT THE GENERAL ADAPTATION POSSIBILITIES OF ANNEX XI OF THE REACH REGULATION ARE NOT ADEQUATE TO GENERATE THE NECESSARY INFORMATION:
- Available GLP studies: There are no GLP-compliant chronic fish studies available on the substance.
- Available non-GLP studies: Acute toxicity studies are available for daphnids, fish and algae. In addition, a daphnia reproduction study is available. A chronic fish study by Barron and Adelmann (1984) reports NOEC values, however after thorough investigation, reported values are insufficiently documented for evaluation and must be classified as Klimisch 4. Additionally, Falk-Petersen et al. (1985) report a study performed on gadus morrhua (Atlantic Cod). This study does not satisfy the requirements according to OECD Guidance and cannot be used to fulfill the information requirements for REACH.
- Historical human data: Not relevant for this endpoint.
- (Q)SAR: There are no QSAR models available for this higher tier ecotoxicological endpoint that are sufficiently validated and acceptable (according to OECD Q/SAR validation criteria).
- In vitro methods: The registrant is not aware of any validated alternative tests that use in vitro methodologies that could be used to meet the standard requirement of the REACH regulation for long-term toxicity towards fish.
- Weight of evidence: No data are available for use in a weight of evidence approach.
- Grouping and read-across: Grouping and read-across approaches have been evaluated and are not considered feasible in this case. p-Cresol is considered to be the most toxic regioisomer of cresols towards the aquatic environment with a 96h-LC50 = 4.4 mg/L (Salmo trutta) determined in an acute fish toxicity study, compared to 96h-LC50 = 6.2 mg/L (Salmo trutta) for o-cresol and 96h-LC50 = 7.6 mg/L (Salvelinus fontinalis) for m-cresol , respectively. This is continued within the acute toxicity studies on invertebrates, where the 48h-EC50 value for p-cresol is 7.7 mg/L (Daphnia magna), while it is 9.6 mg/L (Daphnia pulex) for o-cresol. For m-cresol a 24h-EC50 of 99.5 mg/L could be determined on Daphnia pulicaria. Hence, testing of p-cresol is considered as the worst-case approach regarding long-term aquatic toxicity testing towards fish.
- Substance-tailored exposure driven testing [if applicable] : Not applicable
- Approaches in addition to above [if applicable] : Not applicable
- Other reasons [if applicable] : Not applicable

Overall, the registrant has carefully considered all general adaptation procedures as listed in Annex XI of the Reach regulation, however the registrant has come to the conclusion that the lack of available data through studies and the level of extensiveness of the study proposed herein, the conduction of an OECD TG 210: Fish Early Life Stage (FELS) toxicity test is considered the best course of action in order to elucidate the long-term toxicity towards fish of p-cresol This study can be further used in read-across approaches for the other regioisomers, o- and m- cresol, as it will cover the worst-case approach. The data generated within this study may be used to cover data gaps of o- and m-cresol through a read-across approach.
CONSIDERATIONS THAT THE SPECIFIC ADAPTATION POSSIBILITIES OF ANNEXES VI TO X (AND COLUMN 2 THEREOF) OF THE REACH REGULATION ARE NOT ADEQUATE TO GENERATE THE NECESSARY INFORMATION:
According to REACH Annex IX, 9.1.6. ‘Long-term toxicity testing on fish, (unless already provided as part of Annex VIII requirements)’ is a standard information requirement and cannot be generated otherwise. The Fish Early Life Stage (FELS) toxicity test (OECD TG 210) is regarded as the most suitable test guideline for addressing the information requirements.

Furthermore, section 9.1, column 2 states:
'Long-term toxicity testing shall be proposed by the registrant if the chemical safety assessment according to Annex I indicates the need to investigate further the effects on aquatic organisms. The choice of the appropriate test(s) depends on the results of the chemical safety assessment.'

The widespread dispersive uses of the registered substance leads to release to the aquatic environment. There is a need for further information on the long-term effects of the registered substance on aquatic organisms. Since long-term data are available for daphnia and algae, data for fish are required as the third pelagic level.

FURTHER INFORMATION ON TESTING PROPOSAL IN ADDITION TO INFORMATION PROVIDED IN THE MATERIALS AND METHODS SECTION:

- Details on study design / methodology proposed [if relevant]: - An OECD 210 Guideline study has been proposed to assess the long-term toxicity towards fish. The substance shall be applied via the freshwater medium.

Qualifier:

according to guideline

Guideline:

OECD Guideline 210 (Fish, Early-Life Stage Toxicity Test)

Water media type:

freshwater

Description of key information

The chronic toxicity of p-cresol to fish was tested with Pimephales promelas in an Early-Life Stage Toxicity Test equivalent to OECD Guideline 210. The 32d NOEC is 1.35 mg/L.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

NOEC

Effect concentration:

1.35 mg/L

Additional information

Concerning long-term toxicity to fish there is one reliable study available. The toxicity test was performed with a method equivalent to OECD TG 210. A 32d-NOEC of 1.35 mg/l was obtained in this test with pimephales promelas.