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Administrative data

Description of key information

Subacute, subchronic and chronic toxicity of 2,5-Di-t-pentylhydroquinone was tested in three studies with rats, during 28, 90 and 500 days, respectively, and in chickens during 8 and 20 weeks.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records
Reference
Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
02 October 2012 - 08 February 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP study, conducted to current guidelines for the purposes of REACH registration.
Qualifier:
according to guideline
Guideline:
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)
Deviations:
yes
Remarks:
See "principles of method if other than guideline"
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.3100 (90-Day Oral Toxicity in Rodents)
Deviations:
yes
Remarks:
See "principles of method if other than guideline"
Qualifier:
according to guideline
Guideline:
other: Japanese Chemical Substances Control Law 1973, Notification of Mar. 31 2012 by MHLW (0331 No.7), METI (No. 5) and MOE (No. 110331009)
Deviations:
yes
Remarks:
See "principles of method if other than guideline"
Qualifier:
according to guideline
Guideline:
other: Council regulation (EC) No 440/2008 Part B: Methods for the Determination of Toxicity and other Health Effects; B.26: “Sub-chronic Oral Toxicity Test: Repeated dose 90-day toxicity study in rodents".
Deviations:
yes
Remarks:
See "principles of method if other than guideline"
Principles of method if other than guideline:
A few organs were not available for histopathology. Missing tissues are listed in raw data and pathology report.
Evaluation: Sufficient data was available for adequate histopathological evaluation.
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
other: Crl:WI(Han)
Details on species / strain selection:
Rationale: Recognized by international guidelines as the recommended test system (e.g. EPA, FDA, OECD and EC).
Sex:
male/female
Details on test animals or test system and environmental conditions:
Test system: Rat: Crl:WI(Han) (outbred, SPF-Quality).
Source: Charles River Deutschland, Sulzfeld, Germany.
Total number of animals: 40 males and 40 females (females were nulliparous and non-pregnant).
Age at start of treatment: Approximately 6 weeks.
Identification: Earmark and tattoo.
Randomization: By computer-generated random algorithm according to body weight, with all animals within ± 20% of the sex mean.
Acclimatization period: At least 5 days before the start of treatment under laboratory conditions.
Health inspection: Upon receipt of the animals.
Room number: A0.05 (A0.23 for motor activity measurements).
Conditions: Environmental controls for the animal room were set to maintain 18 to 24°C, a relative humidity of 40 to 70%, approximately 15 room air changes/hour, and a 12-hour light/12-hour dark cycle. Any variations to these conditions were maintained in the raw data and had no effect on the outcome of the study.
Accommodation: Group housing of 5 animals per sex in Macrolon cages (MIV type, height 18 cm) with sterilized sawdust as bedding material (Litalabo, S.P.P.S., Argenteuil, France) and paper as cage-enrichment (Enviro-dri, Wm. Lilico & Son (Wonham Mill Ltd), Surrey, United Kingdom). During locomotor activity monitoring, animals were housed individually in a Hi-temp polycarbonate cage (Ancare corp., USA; dimensions: 48.3 x 26.7 x 20.3 cm) without cage-enrichment or bedding material.
Diet: Free access to pelleted rodent diet (SM R/M-Z from SSNIFF® Spezialdiäten GmbH, Soest, Germany). During motor activity measurements, animals had no access to food.
Water: Free access to tap water except during motor activity measurements.
Diet, water, bedding and cage enrichment evaluation for contaminants and/or nutrients was performed according to facility standard procedures. There were no findings that could interfere with the study.
Route of administration:
oral: gavage
Vehicle:
propylene glycol
Details on oral exposure:
Vehicle: Propylene glycol, specific gravity 1.036.
Rationale for vehicle: Based on trial formulations performed at WIL Research Europe and on information from the sponsor.
Method of formulation: Formulations (w/w) were prepared daily within 6 hours prior to dosing, and were homogenized to a visually acceptable level. Adjustment was made for specific gravity of the vehicle. No correction was made for the purity/composition of the test substance.
Storage conditions: At ambient temperature.
Method: Oral gavage, using a plastic feeding tube. Formulations were placed on a magnetic stirrer during dosing.
Dose volume: 5 mL/kg body weight.
Frequency: Once daily, 7 days per week, approximately the same time each day with a maximum of 6 hours difference between the earliest and latest dose.
Duration of treatment: 90-91 days. Animals were dosed up to the day prior to necropsy.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Analyses were conducted on three occasions during the treatment phase, according to a validated method (project 494311). Samples of formulations were analyzed for homogeneity (highest and lowest concentration) and accuracy of preparation (all concentrations, in weeks 1, 6 and 13). Stability in vehicle over 6 hours and over 8 days at room temperature under normal laboratory light conditions was also determined (highest and lowest concentration, in week 1).
The accuracy of preparation was considered acceptable if the mean measured concentrations were or 85-115% of the target concentration . Homogeneity was demonstrated if the coefficient of variation was ≤ 10%. Formulations were considered stable if the relative difference before and after storage was maximally 10%.
Duration of treatment / exposure:
90
Frequency of treatment:
Frequency: Once daily, 7 days per week, approximately the same time each day with a maximum of 6 hours difference between the earliest and latest dose.
Remarks:
Doses / Concentrations:
15 mg/kg/day
Basis:
actual ingested
Remarks:
Doses / Concentrations:
50 mg/kg/day
Basis:
actual ingested
Remarks:
Doses / Concentrations:
150 mg/kg/day
Basis:
actual ingested
No. of animals per sex per dose:
10 male, 10 female.
Control animals:
yes, concurrent vehicle
Details on study design:
Dose levels were based on results of a 14-day oral range finding study with Lowinox® AH25 by daily gavage in the rat (project 501334). A summary of the results is included in the study report.
Randomization: By computer-generated random algorithm according to body weight, with all animals within ± 20% of the sex mean.
Positive control:
No
Observations and examinations performed and frequency:
Mortality / Viability: At least twice daily.

Clinical signs:
At least once daily from start of treatment onwards, detailed clinical observations were made in all animals. These observations were conducted after dosing at no specific time point, but with a similar time period after dosing for the respective animals. Once prior to start of treatment and at weekly intervals, this was also performed outside the home cage in a standard arena. The time of onset, grade and duration of any observed signs were recorded. Signs were graded for severity and the maximum grade was predefined at 3 or 4. Grades were coded as slight (grade 1), moderate (grade 2), severe (grade 3) and very severe (grade 4). For certain signs, only its presence (grade 1) or absence (grade 0) was scored. In the data tables, the scored grades are reported, as well as the percentage of animals affected in summary tables.

Functional Observations:
During week 12 of treatment, the following tests were performed on all animals, after dosing at no specific time point but within a similar time period after dosing for the respective animals (abbreviations mentioned in the respective tables indicated between brackets):
a) hearing ability (HEARING), pupillary reflex (PUPIL L/R), static righting reflex (STATIC R) and grip strength (GRIP) (Score 0 = normal/present, score 1 = abnormal/absent).
b) locomotor activity (recording period: 1-hour under normal laboratory light conditions, using a computerized monitoring system, Kinder Scientific LLC, Poway, USA). Total movements and ambulations were reported. Ambulations represent movements characterized by a relocation of the entire body position like walking, whereas total movements represent all movements made by the animals, including ambulations but also smaller or more fine movements like grooming, weaving or movements of the head.

Body weights: Weekly.

Food consumption: Weekly.

Water consumption: Subjective appraisal was maintained during the study, but no quantitative investigation introduced as no effect was suspected.

Ophthalmoscopic Examination (direct):
Following instillation of tropicamide solution (5 mg/mL, THEA Pharma, Wetteren, Belgium) both eyes were examined by means of an ophthalmoscope (Heine Beta 200):
at pretest : All animals
at week 13 : Groups 1 and 4

Since no treatment-related ophthalmologic findings were noted in week 13, the eyes of the rats of Groups 2 and 3 were not examined.
Sacrifice and pathology:
Clinical laboratory investigations
Blood samples were collected under anaesthesia using isoflurane (Abbott B.V., Hoofddorp, The Netherlands) between 7.00 and 10.30 a.m. on the day of necropsy. Animals were deprived of food overnight (for a maximum of 24 hours1), but water was available.

Blood samples were drawn from the retro-orbital sinus and collected into tubes (Greiner Bio-One GmbH, Kremsmünster, Austria) prepared with EDTA for haematological parameters (0.5 mL), with citrate for clotting tests (0.45 mL) and Li-heparin treated tubes for clinical biochemistry parameters (0.5 mL). An additional blood sample (0.25 mL) was collected into untreated tubes for determination of bile acids. The following parameters were determined:

Parameter
Haematology
White blood cells; Differential leucocyte count; neutrophils, lymphocytes, monocytes, eosinophils, basophils; Red blood cells; Reticulocytes; Red blood cell distribution width; Haemoglobin; Haematocrit; Mean corpuscular volume; Mean corpuscular haemoglobin; Mean corpuscular haemoglobin concentration; Platelets; Clotting Potential; Prothrombin time; Activated Partial thromboplastin time

Clinical Biochemistry
Alanine aminotransferase; Aspartate aminotransferase; Alkaline phosphatase; Total Protein; Albumin; Total Bilirubin; Urea; Creatinine; Glucose; Cholesterol; Sodium; Potassium; Chloride; Calcium; Inorganic Phosphate; Bile acids

Pathology
Necropsy
Animals surviving to the end of the observation period were deeply anaesthetized using isoflurane (Abbott B.V., Hoofddorp, The Netherlands) and subsequently exsanguinated and subjected to a full post mortem examination. Animals were deprived of food overnight (with a maximum of 24 hours 1) prior to scheduled necropsy. All animals assigned to the study were necropsied and descriptions of all macroscopic abnormalities recorded. Samples of the following tissues and organs were collected from all animals at necropsy and fixed in 10% buffered formalin (neutral phosphate buffered 4% formaldehyde solution, Klinipath, Duiven, The Netherlands):

Identification marks: not processed
Adrenal glands; Aorta; Brain [cerebellum, mid-brain, cortex]; Caecum; Cervix; (Clitoral gland); Colon; Duodenum; Epididymides; Eyes with optic nerve [if detectable]; Harderian gland; Female mammary gland area; (Femur including joint); Heart; Ileum; Jejunum; Kidneys; Larynx; (Lacrimal gland, exorbital); Liver; Lung, infused with formalin; Lymph nodes - mandibular, mesenteric; (Nasopharynx); Oesophagus; Ovaries; Pancreas; Peyer's patches [jejunum, ileum] if detectable; Pituitary gland; (Preputial gland); Prostate gland; Rectum; Salivary glands - mandibular, sublingual; Sciatic nerve; Seminal vesicles; (Skeletal muscle); Skin; Spinal cord -cervical, midthoracic, lumbar; Spleen; Sternum with bone marrow; Stomach; Testes; Thymus; Thyroid including parathyroid [if detectable]; (Tongue); Trachea; Urinary bladder; Uterus; Vagina; All gross lesions
Tissues/organs mentioned in parentheses were not examined by the pathologist, since no signs of toxicity were noted at macroscopic examination.

Organ weights
The following organ weights and terminal body weight were recorded from the animals on the scheduled day of necropsy:
Adrenal glands; Brain; Epididymides; Heart; Kidneys; Liver;' Ovaries; Spleen; Testes; Thymus; Uterus (including cervix); Prostate; Seminal vesicles including coagulating glands; Thyroid including parathyroid

Histotechnology
All organ and tissue samples, as defined under Histopathology (following), were processed, embedded in paraffin wax (Klinipath, Duiven, The Netherlands), cut at a thickness of 2-4 micrometers and stained with haematoxylin and eosin (Klinipath, Duiven, The Netherlands).

Histopathology
The following slides were examined by a pathologist:
- all tissues collected at the scheduled sacrifice from all Main group 1 and 4 animals,
- thyroid, stomach and adrenal glands (both sexes), kidneys (females) and mesenteric lymph node (males) of groups 2 and 3, based on (possible) treatment-related microscopic changes in these organs in group 4.
- all gross lesions.

All abnormalities were described and included in the report. An attempt was made to correlate gross observations with microscopic findings.
Histopathology was subjected to a peer review.
Statistics:
The following statistical methods were used to analyze the data:
1) If the variables could be assumed to follow a normal distribution, the Dunnett-test (Ref. 1; many-to-one t-test) based on a pooled variance estimate was applied for the comparison of the treated groups and the control groups for each sex.
2) The Steel-test (Ref. 2; many-to-one rank test) was applied if the data could not be assumed to follow a normal distribution.
3) The Fisher Exact-test (Ref. 3) was applied to frequency data.
4) The Kruskal-Wallis nonparametric ANOVA test (Ref. 4) was applied to motor activity data to determine intergroup differences.

All tests were two-sided and in all cases p < 0.05 was accepted as the lowest level of significance. Group means were calculated for continuous data and medians were calculated for discrete data (scores) in the summary tables. Test statistics were calculated on the basis of exact values for means and pooled variances. Individual values, means and standard deviations may have been rounded off before printing. Therefore, two groups may display the same printed means for a given parameter, yet display different test statistics values.
Clinical signs:
effects observed, non-treatment-related
Description (incidence and severity):
No toxicologically relevant clinical signs were noted during the observation period.
Salivation seen after dosing among all animals at 15, 50 and 150 mg/kg was considered to be a physiological response rather than a sign of systemic toxicity considering the nature and minor severity of the effect and its time of occurrence (i.e. after dosing). This sign may be related to irritancy/taste of the test substance.
Incidental findings that were noted included piloerection (one female at 150 mg/kg), gasping, scabs, rales, alopecia, exophthalmos of the right eye, watery discharge from the eye and chromodacryorrhoea. These findings occurred within the range of background findings to be expected for rats of this age and strain which are housed and treated under the conditions in this study. At the incidence observed, these were considered signs of no toxicological significance.
Mortality:
no mortality observed
Description (incidence):
No mortality occurred during the study period.
Body weight and weight changes:
effects observed, non-treatment-related
Description (incidence and severity):
No toxicologically significant changes in body weights and body weight gain were noted.
Body weights of females at 150 mg/kg were higher than control levels throughout most of the treatment period, achieving a level of statistical significance on several occasions. Since this change was slight in nature, it was considered not to be toxicologically relevant.
Food consumption and compound intake (if feeding study):
not examined
Description (incidence and severity):
No toxicologically significant changes in food consumption before or after correction for body weight were noted.
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
effects observed, non-treatment-related
Description (incidence and severity):
No toxicologically significant ophthalmology findings were noted.
Incidental ophthalmology findings at pretest and in week 13 consisted of focal corneal oedema or opacity, a haemorrhage from the anterior chamber or hyaloid vessel and/or persistent pupillary membrane.
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
The following statistically significant changes in haematology parameters distinguished treated animals from control animals:
− Higher platelet counts in males at 150 mg/kg,
− Higher white blood cell counts (WBC) in females at 150 mg/kg,
− Lower red blood cell counts in females at 50 and 150 mg/kg,
− Higher reticulocyte counts in females at 150 mg/kg,
− Lower haemoglobin level in females at 50 and 150 mg/kg,
− Lower haematocrit level in females at 150 mg/kg.
Means of the above haematological changes remained within the range considered normal for rats of this age and strain.
The statistically significant lower prothrombin time (PT) in males at 50 mg/kg and females at 150 mg/kg occurred in the absence of a dose-related trend and/or remained within the range considered normal for rats of this age and strain. An opposite and more pronounced effect would be expected in case of target organ toxicity. These changes were therefore considered to be of no toxicological significance.
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
The following (statistically significant) changes in clinical biochemistry parameters distinguished treated animals from control animals:
− Higher alanine aminotransferase activity in males and females at 150 mg/kg (in males, this was due to one higher value (no. 32)),
− Higher aspartate aminotransferase activity in females at 150 mg/kg (one male (no. 32) also showed a high value),
− Higher albumin level in males at 15, 50 and 150 mg/kg, and in females at 50 and 150 mg/kg (no clear dose-related trend),
− Higher total bilirubin level in males at 150 mg/kg,
− Higher creatinine level in males at 150 mg/kg,
− Lower glucose level in males at 15, 50 and 150 mg/kg (no clear dose-related trend),
− Higher cholesterol level in males and females at 150 mg/kg,
− Lower bile acid level in males at 150 mg/kg,
− Higher sodium level in males at 15, 50 and 150 mg/kg (no clear dose-related trend),
− Higher potassium level in females at 150 mg/kg,
− Higher chloride level in males at 15, 50 and 150 mg/kg (no clear dose-related trend).
The statistically significant higher calcium level in males, and the higher sodium and chloride and lower inorganic phosphate level in females (all at 50 mg/kg) occurred in the absence of a dose-related trend and remained within the range considered normal for rats of this age and strain. No toxicological significance was therefore ascribed to these changes.
Urinalysis findings:
no effects observed
Behaviour (functional findings):
effects observed, non-treatment-related
Description (incidence and severity):
No toxicologically significant effects on hearing ability, pupillary reflex, static righting reflex and grip strength were observed.
One male at 50 mg/kg showed a pupil size that remained small. Given the incidental nature of this finding and absence of a dose-related incidence, this was considered to be of no toxicological relevance.
Motor activity was similar between treated and control groups. All groups showed a similar motor activity habituation profile with high activity in the first interval that decreased over the duration of the test period.
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
The following changes in absolute organ weights and relative organ weights (organ to body weight ratio) were considered to be related to treatment:
− Higher liver and liver to body weight ratio in females at 50 and 150 mg/kg,
− Higher thyroid and thyroid to body weight ratio in females at 50 and 150 mg/kg,
− Higher ovary weight and ovary to body weight ratio at 150 mg/kg.
Any other statistically significant changes in organ weights and organ to bodyweight ratios were considered to be of no toxicological relevance, as no histopathological correlates were found, terminal body weights were considered to be slightly low and/or means occurred in the absence of a dose related trend. These changes consisted of lower thymus, adrenal and prostate weight in males at 150 mg/kg, higher liver to body weight ratio in males at 15, 50 and 150 mg/kg, higher thyroid to body weight ratio in males at 15 mg/kg, higher testes to body weight ratio in males at 50 mg/kg, and higher heart weight in females at 150 mg/kg.
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
The following macroscopic findings were considered to be related to treatment:
− Pale discolouration of the adrenal glands in 1/10 females at 50 mg/kg and in 4/10 females at 150 mg/kg.
− Dark red/red brown discolouration of the liver in 5/10 females at 150 mg/kg.
The incidence of other macroscopic findings among control and treated animals was within the background range of findings that are encountered among rats of this age and strain, and did not show a dose-related incidence trend. These necropsy findings were therefore considered to be of no toxicological relevance.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
There were treatment-related microscopic findings present in males and/or females:
− Increased incidence and/or severity of follicular cell hypertrophy of the thyroid gland in males at 15, 50 and 150 mg/kg, and in females at 50 and 150 mg/kg (up to slight degrees; the incidence and severity of this finding is within the normal background levels which can be found in control rats).
− Increased incidence and severity of hyper- and dyskeratosis of the limiting ridge of the stomach in males at 150 mg/kg and females at 15, 50 and 150 mg/kg (up to moderate degrees).
− Hyaline droplets in the kidneys of 1/10 females (1 minimal) at 50 mg/kg and in 5/10 females (3 minimal, 2 slight) at 150 mg/kg.
All other microscopic findings were within the range of background pathology encountered in Wistar rats of this age and strain and occurred at similar incidences and severity in both control and treated rats.
Histopathological findings: neoplastic:
not examined
Other effects:
not specified
Key result
Dose descriptor:
NOAEL
Effect level:
150 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: see 'Remark'
Key result
Critical effects observed:
not specified

Analysis of dose preparations:

The purpose of the study was to determine the accuracy of preparation, homogeneity and stability of the test substance in formulations.

 

Accuracy of preparation:

The concentrations analysed in the formulations of Group 2, Group 3 and Group 4 were in agreement with target concentrations (i.e. mean accuracies between 85% and 115%).

No test substance was detected in the Group 1 formulations.

 

Homogeneity:

The formulations of Group 2 and Group 4 were homogeneous (i.e. coefficient of variation ≤ 10%).

 

Stability:

Formulations at the entire range were stable when stored at room temperature under normal laboratory light conditions for at least 6 hours, but not when stored at room temperature under normal laboratory light conditions for at least 8 days.

Conclusions:
From the results presented in this report a No Observed Adverse Effect Level (NOAEL) for Lowinox® AH25 of 150 mg/kg was established. No classification or labelling is applicable.
Executive summary:

Wistar rats were treated with Lowinox® AH25 for 13 weeks by daily oral gavage at dose levels of 15, 50 and 150 mg/kg.

 

Treatment at dose levels up to 150 mg/kg was well tolerated by the animals. No toxicologically significant changes were noted in any of the parameters investigated in this study during the in-life phase of the study (i.e. clinical appearance, functional observations, ophthalmoscopy, body weight, food consumption).

 

The changes in haematological and clinical biochemistry parameters were generally slight in nature, remained essentially within the range considered normal for rats of this age and strain, and had no apparent treatment-related morphological correlates. There were no indications that the changes in red blood cell parameters represented an adverse effect on red blood cell turn over.

 

No histopathological correlate was found for the pale discolouration of the adrenal glands in 1/10 females at 50 mg/kg and in 4/10 females at 150 mg/kg, for the dark red/red brown discolouration of the liver in 5/10 females at 150 mg/kg and for the higher ovary weight and ovary to body weight ratio at 150 mg/kg.

 

Liver to body weight ratio of females at 50 and 150 mg/kg was increased with approximately 11 and 24% compared to control levels. Since there were no supportive histopathological lesions and no toxicologically relevant clinical biochemistry changes occurred, these higher liver weights were considered to be non-adverse in nature.

 

The incidence and severity of follicular cell hypertrophy of the thyroid gland in males at 15, 50 and 150 mg/kg, and in females at 50 and 150 mg/kg (up to slight degrees) is within the normal background levels which can be found in control rats. This finding coincided with higher thyroid and thyroid to body weight ratio in females at 50 and 150 mg/kg, but not in males. The increased incidence and severity of hyper- and dyskeratosis of the limiting ridge of the stomach in males at 150 mg/kg and females at 15, 50 and 150 mg/kg (up to moderate degrees) was confined to the limiting ridge only. Body weight and food intake development showed no treatment-related changes suggesting that stomach function was affected. The hyaline droplets in the kidneys in one female at 50 mg/kg and 5/10 females at 150 mg/kg (up to slight degree) occurred without concurrent morphological lesions in the kidneys or changes in blood parameters suggestive of an adverse effect on renal function. These histopathological findings were therefore considered not to be adverse in nature.

 

None of the above findings were considered to be detrimental to organ system function or vitality of the animals, and were therefore considered not adverse in nature.

 

From the results presented in this report a No Observed Adverse Effect Level (NOAEL) for Lowinox® AH25 of 150 mg/kg was established. No classification or labelling is applicable.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
150 mg/kg bw/day
Study duration:
subchronic
Species:
rat
Quality of whole database:
GLP study conducted in accordance with current OECD Guidance therefore categorised as Klimisch 1.

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

In the 90 day repeated dose oral toxicity study in rats, a No Observed Adverse Effect Level (NOAEL) for Lowinox® AH25 of 150 mg/kg was established (the highest dose tested). In the 28 day study, male and female rats were treated with 0, 100, 1000, 3000, and 5000 ppm 2,5-Di-t-pentylhydroquinone. 2,5-Di-t-pentylhydroquinone decreased kidney weights in the females treated with 1000 ppm and higher. Although at 1000 ppm effect was only 9%, no histopathology is performed and thus the effect is considered adverse with no further information available. Other signs of toxicity were reported in females and males treated with 3000 and 5000 ppm. A NOAEL of 2,5 -Di-t-pentylhydroquinone in this study was estimated 100 ppm (9.4 mg/kg bw/day) for females and 1000 ppm for males. In two other supportive publications (in rats and chickens), no NOAEL could be established.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:

90 day study in rats conducted in accordance with GLP and current guidelines.

Justification for classification or non-classification

Based on the above mentioned results, the substance does not need to be classified according to the Dangerous Substance Directive 67/548/EC and CLP Regulation(EC) 1272/2008.

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