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EC number: 215-089-3
CAS number: 1300-71-6
existing Ames data in the form of a GLP conducted study on mixed
xylenols is available. Under this study, mixed xylenols were tested up
to 5 mg/plate (maximum recommended dose) and returned a negative result
in the absence and presence of metabolic activation (S9). Supporting
studies on mixed cresols and also on the individual cresol isomers all
confirm in the absence and presence of S9 that these test materials do
not increase background gene mutation rates above that of the solvent
control. Based on stuctural similiarites it is reasonable to assume that
ethylphenols would return the same result.
gene mutation (in vitro)
conducted gene mutation study on CHL V79 cells targeting the hprt locus
returned negative results in the absence and presence of S9 mix, when
tested up to cytotoxic concentrations in two independent experiments. In
the second experiment a non-dose related increase in mean mutant
frequency was observed, however these increases were accompanied by
cytotoxicity and were non-reproducible when compared to the first
studies targeting thetklocus have been performed on all three
cresol isomers and have returned negative results. It is important to
note however that no cytotoxicity data were discussed / presented or
evidence of precipitate; therefore the limiting factor for the maximum
dose level tested was not justified. However, based on structrual
similarities with xylenols, cresols along with ethylphenols would be
expected to return results comparable to the GLP study performed.
chromosome aberration (in vitro)
mammalian CHO chromosomal aberration studies condcted on mixed xylenols
and mixed phenols confirmed increases in chromosomal aberrations in both
the absence and presence of S9. In both cases acceptable levels of
toxicity were obtained. Similar results were also obtained with with m,o
and p cresols, however or note not concurrent measure of cytotoxicity
was performed (only conducted in a range-finder experiment). However,
based on structrual similarities with xylenols and ethylphenols, cresols
would be expected to return results which were comparable when
accompanied by concurrent cytotoxicity measures.
vivo bone marrow micronucleus
bone marrow micronucleus study on 3,5 xylenol conducted confirmed no
evidence of micronuclei induction in the bone marrow polychromatic
erthyrocytes of mice when tested up to a dose of 1500 mg/kg (maximum
tolerated dose - MTD). Despite deaths occuring (1 male and 1 female at
the 48 hr sample point), as there were no gender differences, it is
deemed acceptable to combine the data (resulting in sufficient numbers
of animals/group), thereby confirming both an acceptable assay and a
negative result. Further support to justifiy a read-across approach
comes from additional mouse bone marrow micronucleus studies on the 2,4
and 2,6 xylenol isomers which also returned negative results when tested
up to an MTD.
in vivo data providing additional support comes from 2 dominant
lethal studies (o and p-cresol) and a mouse bone marrow chromosome
aberration study (m-cresol). In the case of the chromosome aberration
study, whilst it is pointed out the no bone marrow toxicity was observed
at the maximum dose tested (as evidence by no decrease in mitotic
index), this clinical signs of toxicity reported would be considered
evident of an MTD being achieved.
for the registration of above 1000 tons/annum the minimum requirements
for the genetic toxicology endpoint are bacterial gene mutation assay,
in vitro mammalian gene mutation and chromsome aberration assays and in
vivo assay. The available data, irrespective of the endpoint examined,
test material used or assay used all return comparable results, which
strongly suggestive that these test materials are indistinguishable, and
where data is absent from a particular chemical there is strong evidence
that read across approach can be taken.
positive results were obtained in the in vitro mammalian chromosome
assay, the negative in vivo data confirms that in the in vitro
result is not realised, imply thus that the in vitro positive result was
not biologically relevant (possible resulting from a cell culture /
in vitro artefact). The overall conclusion from these data confirm
under the requirements of this registration the genetic endpoint has
been adequately addressed and these chemicals are devoid of genetic
potential under the testing protocol used.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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