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Environmental fate & pathways

Hydrolysis

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Description of key information

In accordance with REACH Annex XI, there is sufficient weight of evidence from several independent sources of information leading to the conclusion that hydrolysis is not an important abiotic degradation pathway for 4-nonylphenol. Therefore, hydrolysis testing for 4-nonylphenol is not scientifically necessary.

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Additional information

As stated in the ECHA Guidance Document R.7B, p. 233, hydrolysis is not an important fate process for petroleum substances since hydrocarbons do not undergo reaction with water. 4-nonylphenol is also a substance among the hydrocarbons consisting of an alkylchain with nine C atoms attached to a phenolring. This means that also for 4-nonylphenol, branched, it can be assumed that hydrolysis is not a dominant route of abiotic degradation.

This assumption is in accordance with Melcer et al., 2007 (p. 11). This study did not expect hydrolysis to be important for alkylphenols because of their chemical structures and the lack of functional groups susceptible to hydrolytic attack.

This assumption is also supported by the EU Risk Assessment Report 2002 (p.54) which states that hydrolysis is a negligible removal processes for nonylphenol in the aquatic environment. This assumption is based upon the stability of nonylphenol during storage and several biodegradation studies reviewed by the UK rapporteur on behalf of the European Union where no degradation was observed in the control experiments. The authors of these studies concluded that abiotic degradation was likely to be negligible (Corti et al., 1995; Trocmé et al., 1988; both cited in the EU Risk Assessment Report 2002).

According to Corti et al., 1995, who observed biodegradation of 4-(1-nonyl)phenol by cultures of a Candida maltosa strain isolated from aerobic sludge samples, no significant abiotic degradation was observed in uninoculated sterile controls. Trocmé et al., 1988, were able to demonstrate that 4-nonylphenol is degraded microbiologically after induction of the microorganisms in an incubation experiment with a reconstituted soil system (compost + sandstone). 4-nonylphenol was more persistent under semi-sterile conditions, with 100 % residual 4-nonylphenol after 15 days, than in the non-sterilized treatment, where only 51 % of the initial concentration was present after 15 days. Trocmé showed that the disappearance of 4-nonylphenol was limited to biodegradation and residue binding.