Phenol, 4-nonyl-, branched

Endpoint summary

Additional information

Three negative Ames tests are available. None was repeated, as required by OECD guidelines in case of a negative result. However, the three studies taken together are considered sufficient to address in vitro gene mutation in bacteria.

One negative Chromosome Aberration assay was reported by Tayama (2008), together with two additional indicator studies for mutagenicity. A COMET assay generated positive results (weak but statistically significant increase in chromosome breakage at 0.125 and 0.15 mM NP). There is currently no (OECD) guideline for COMET assays and the documentation is insufficient (Klimisch 3). The method was ‘mostly in accordance with the protocol for the COMET assay kit’. A significant decrease in viable cells at 0.15 mM NP was recorded; however this cytotoxic effect is not relevant for the mutagenicity endpoint. A positive result was also reported for a Sister Chromatide Exchange (SCE) assay; SCE may be an indicator for repaired DNA damage. The CA test carried out by Tayama is considered a reliable study indicating the absence of cytogenicity in mammalian cells in vitro. Both additional indicator tests reported in the same publication gave positive results. However, in each case there are concerns regarding the reliability of the test method and/or the relevance of the result. The Chromosome Aberration test is considered sufficient to address this endpoint, and over-rules the results of both other indicator studies. This is in accordance with the endpoint specific guidance R.7a (ECHA).

IBR Forschungs GmbH (1990, Sponsor: Huels AG) reported a negative in vitro mammalian cell gene mutation test according OECD 476. 

 

Three in vivo micronucleus studies are available. Huels (1999) was conducted according to OECD guideline 474. Fife NMRI mice/sex received a single intraperitoneal dose of 50, 150 or 300 mg/kg bw. The highest dose level was chosen as the maximum tolerated dose, based on the results of a preliminary study. Toxicity was elicited at 150 and 300 mg/kg, seen as clinical signs (sedation, squatting posture, abnormal gait and piloerection). There was no consistent effect on the PCE/NCE ratio. No increases in the frequency of micronucleated PCEs were seen. Thus, the test is considered to be negative. Although the PCE/NCE ratio was not affected, the fact that the study was conducted at the maximum tolerated dose and using the intraperitoneal route of administration, it can be presumed that exposure of the one marrow was maximised. Accordingly, a high level of confidence can be given to this negative result. In contrast, an earlier micronucleus test (Huels, 1988, limit test) was conducted using the oral route of administration. No increases in the frequency of micronuclei were observed within 72 h. The test was considered to be negative. However, the PCE/NCE ratio was not affected by nonylphenol, which raises concerns about adequacy of exposure of the bone marrow to the test substance. Toxicokinetic data suggests that the bioavailability of Nonylphenol after oral exposure is restricted due to an extensive first pass effect. Thus, the oral route is considered not appropriate for the assessment of Nonylphenol by means of in vivo micronucleus studies.

In a recent publication by Dobrzynska (2008) the induction of micronuclei in somatic cells of mice exposed to x-rays or nonylphenol and to a combination of both agents was assessed. The author concluded an increase in chromosome aberration in mice caused by i.p. administration of 4-Nonylphenol at doses of 25 and 50 mg/kg bw/day for 8 weeks (5 d/w). After translating the Polish study and checking raw data provided by the author, this conclusion could not be affirmed. The description of the methods is poor (e.g. number of animals not indicated) and the results are not significant. In peripheral blood (reticulocytes) no significant difference to control group in the 25 mg/kg/d group and no significant difference in the 50 mg/kg/d group expect in week 1+3+4 (from 8) was observed. No significant difference to control group were observed in reticulocytes at the terminal assessment of bone marrow. If only polychromatic erythrocytes were considered, a significant difference to control group was evident. According OECD 474 this is the more relevant parameter compared to reticulocytes. However, dependency on dosage could not be established (50 mg/kg < 25 mg/kg). The result of this publication does not challenge the negative results reported in both Huels studies (1999/1988).

 

In summary, results derived from this test battery are sufficient to cover the data requirement for in vitro and in vivo mutagenicity under REACH. Nonylphenol is considered not mutagenic.

Short description of key information:

- Three negative Ames tests (Huels, 1987 [CAS 26543-97-5]; Shimuzu, 1985 [CAS 104-40-5]; Huels, 1984 [substance identified as “Nonylphenol”]).

- One negative Chromosome Aberration assay (Tayama, 2008 [4-Nonylphenol = CAS 84852-15-3 or CAS 104-40-5]). In addition a positive COMET assay and a positive Sister Chromatide Exchange (SCE) assay were reported in the same study.

- One negative in vitro mammalian cell gene mutation test (IBR Forschungs GmbH, 1990 (Sponsor: Huels) [substance identified as “Nonylphenol”]).

- Three in vivo micronucleus tests are available. Two gave negative results (Huels, 1999 [CAS 25154-52-3] and Huels, 1988 [substance identified as “Nonylphenol”]), one was ambiguous (Dobrzynska, 2008 [CAS 104-40-5]).

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Results derived from this test battery are sufficient to cover the data requirement for in vitro and in vivo mutagenicity under REACH. Nonylphenol is considered not mutagenic.