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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

There are no reliable experimental data on bioaccumulation for p-cresol available. Therefore, data of the isomer m-cresol and o-cresol are taken into account to describe the potential for bioaccumulation of p-cresol based on a read-across approach. The lowest value of 10.7 is used for assessment. 

Key value for chemical safety assessment

BCF (aquatic species):
10.7 dimensionless

Additional information

There are no reliable experimental data on bioaccumulation for p-cresol available. Therefore, data of the isomer m-cresol and o-cresol are taken into account to describe the potential for bioaccumulation of p-cresol. Because of the similar log Kow values 1.95 for o-cresol, 1.96 m-cresol- and 1.94 for p-cresol, a similar accumulation behaviour is expected. As the experimentally determined BCF for o-cresol and m-cresol indicates a low bioaccumulation potential, the potential for bioaccumulation of p-cresol is also considered to be low.

Justification for the read-across approach:

Data from substances who’s physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity may be used in a read-across approach in order to avoid unnecessary animal testing. It can be stated that the 3 cresols act as a prime example of substances that are suitable for read-across. 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.

The bioconcentration factor (BCF) in fish (Leuciscus idus melanotus) was determined with 14C-labelled m-cresol. The fish were exposed to a 0.05 mg/l solution of the tests compound. After the test period of 3 days radioactivity was measured in water medium and fish. A BCF value of 20 was obtained.

In a flow-through test according to OECD guideline 305 E for o-cresol a BCF of 10.7 in zebrafish (Brachydanio rerio) were obtained and hence o-cresol is not bioaccumulative.