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Repeated dose toxicity: oral

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short-term repeated dose toxicity: oral
combined repeated dose and reproduction / developmental screening
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
weight of evidence
Justification for type of information:
No data are available for the target substance. 90-day repeated dose oral toxicity studies are available for individual (o-, m- and p-) cresol isomers and all report NOAEL and LOAEL values of 50 and 150 mg/kg bw/d, respectively. Critical findings in the study with o-cresol included central nervous system depression and reductions in body weight and body weight gain. Critical findings in the study with m-cresol included reductions in body weight and body weight gain. Critical findings in the study with p-cresol include increased mortality, clinical signs (including lethargy, excessive salivation, tremor, occasional convulsions and coma), hepatotoxicity and nephrotoxicity. The data therefore demonstrate a higher degree of toxicity for p-cresol, which has a metabolic basis (see discussion above). OECD 422 screening studies available for xylenol (mixed isomers) and ethylphenol (mixed isomers) both report NOAEL values of 100 mg/kg bw/d. The xylenol study reports clinical signs (stained fur) and increased relative weights of the kidneys, liver and ovaries at the NOAEL of 245 mg/kg bw/d. The ethylphenol study reports clinical signs (stained fur, salivation) and increased relative weights of the kidneys, liver and ovaries at the NOAEL of 245 mg/kg bw/d. Read-across is therefore proposed to the study with xylenol as the closest structural analogue among the Category members.

Data source

Materials and methods

Test guideline
according to guideline
OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
GLP compliance:
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
Reaction mass of 2,4-xylenol and 2,5-xylenol
EC Number:
Cas Number:
Molecular formula:
Reaction mass of 2,4-xylenol and 2,5-xylenol
Test material form:
solid: bulk

Test animals

other: Crl:CD (SD)IGS BR VAF/Plus

Administration / exposure

Route of administration:
oral: gavage
corn oil
Details on oral exposure:
The test substance was prepared as a solution in the vehicle and administered orally by gavage.
Analytical verification of doses or concentrations:
Details on analytical verification of doses or concentrations:
GC/FID analysis of dosing preparation concentration, stability and homogeneity.
Duration of treatment / exposure:
28 days for males and 54 days for females.
Frequency of treatment:
Daily administration beginning 14 days prior to cohabitation and continuing until the day before sacrifice.
Doses / concentrations
Doses / Concentrations:0, 30, 100 and 245 mg/kg/dayBasis:actual ingested
No. of animals per sex per dose:
10 rats per sex per group
Control animals:
yes, concurrent vehicle


Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes- Time schedule: At least 2/dayDETAILED CLINICAL OBSERVATIONS: Yes- Time schedule: 2/dayBODY WEIGHT: Yes- Time schedule for examinations: WeeklyObservations were performed for viability, clinical signs of toxicity, food consumption, body weight gain, functional observational battery and motor activity, hematology, clinical chemistry, developmental toxicity and reproductive performance, gross and microscopic post-mortem examination.
Sacrifice and pathology:
Body weight, weight gains and reproductive end points analysed by ANOVA and Dunnett's. Reproductive data analysed by Fisher's exact test.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
mortality observed, treatment-related
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
not specified
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
no effects observed
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
Relative weights of kidney, liver and ovaries were increased in the high dose group.

Effect levels

Dose descriptor:
Effect level:
100 mg/kg bw/day (nominal)
Basis for effect level:
other: Due to clinical observations (urine-stained fur, increased kidney, liver and ovarian relative weight).

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

All rats survived the treatment. In males, urine stained fur was observed at the 245 mg/kg/day level. Body weight gain and food consumption were unaffected by treatment. Mating frequency was reduced at the 245 mg/kg/day level. Neurotoxicity was not observed during the study and there were no treatment related effects observed at gross necropsy or histopathologically. Urine staining of the fur was observed in females at the 245 mg/kg/day level. F1 animals showed no treatment related clinical or necropsy signs. Haematology and clinical pathology parameters were unaffected.

Reproductive indices are discussed under section 7.8.1.

Applicant's summary and conclusion

The test substance mixed xylenol isomers was administered to rats by oral gavage at 0, 30, 100 and 245 mg/kg/day. The general toxicological No Observable Adverse Effect Level was shown to be 100 mg/kg/day. The reproductive NOAEL is discussed under section 7.8.1.
Executive summary:

The above results are suitable to be used for read across for Reaction mass of 2,4-xylenol and 2,5-xylenol, due to the category being based on structural similarity and comparable physicochemical properties, leading to similar (eco)toxicological properties.

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