2-Propenoic acid, butyl ester, reaction products with butadiene, sulfur and tri-Ph phosphite

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Remarks:

combined repeated dose and reproduction / developmental screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Between 02 June 2009 and 27 November 2009.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study; well documented study report

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2009

Report date:

2010

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Date of inspection 19/08/2008. Date of signature 04/03/2009.

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-Propenoic acid, butyl ester, reaction products with butadiene, sulfur and tri-Ph phosphite

EC Number:

300-339-7

EC Name:

2-Propenoic acid, butyl ester, reaction products with butadiene, sulfur and tri-Ph phosphite

Cas Number:

93925-37-2

Molecular formula:

C18H15O3P.C7H12O2.C4H6.S as an example

IUPAC Name:

2-Propenoic acid, butyl ester, reaction products with butadiene, sulfur and tri-Ph phosphite

Details on test material:

- Physical state: pale amber coloured liquid
- Analytical purity: 100%
- Storage condition of test material: room temperature in the dark

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Wistar Han™:HsdRccHan™:WIST strain rats from Harlan UK, Ltd, Oxon, UK
- Age at study initiation: Approximately 12 weeks old
- Weight at study initiation: the males weighed 301 to 352 g; the females weighed 184 to 219 g
- Fasting period before study: Not applicable
- Housing: Initially, all animals were housed in groups of five in solid floor polypropylene cages withstainless steel mesh lids and softwood flake bedding (Harlan UK Ltd). During the mating phase, animals were transferred to polypropylene grid floor cages suspended over trayslined with absorbent paper on a one male: one female basis within each dose group. Following evidence of successful mating, the males were returned to their original cages. Mated females were housed individually during gestation and lactation, in solid floor polypropylene cages with stainless steel mesh lids and softwood flakes.
- Diet: The animals were allowed free access to food. A pelleted diet (Rodent 2018CTeklad Global Certified Diet Harlan UK Ltd, Oxon, UK) was used throughout the study period. The diet was considered not to contain any contaminant at a level that mighthave affected the purpose or integrity of the study.
- Water: The animals were allowed free access to water. Mains drinking water was supplied from polycarbonate bottles attached to the cage. The drinking water was considered not to contain any contaminant at a level that might have affected the purpose or integrity of the study.
- Acclimation period: 12 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 ± 2
- Humidity (%): 55 ± 15%
- Air changes (per hr): At least fifteen air changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours continuous light and 12 hours darkness

IN-LIFE DATES: between 28 July 2009 (first day of treatment) and 16 September 2009 (final necropsy).

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: Arachis oil BP

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
For the purpose of the study, the test material was prepared at the appropriate concentrations as a solution in Arachis oil BP. The stability and homogeneity of the test material formulations were determined by Harlan Laboratories Ltd. Results show the formulations to be stable for at least 21 days. Formulations were therefore prepared fortnightly and stored at approximately 4ºC in the dark.
Samples were taken of each test material formulation and were analyzed for concentration of test material at Harlan Laboratories Ltd. The results indicate that the prepared formulations were within ± 8% of the nominal concentration.
DIET PREPARATION
- Rate of preparation of diet (frequency): Not applicable
- Mixing appropriate amounts with (Type of food): Not applicable
- Storage temperature of food: Not applicable

VEHICLE: Arachis oil BP
- Justification for use and choice of vehicle (if other than water): Test material was poorly water soluble, so Arachis oil BP was used as vehicle to prepare test material solution.
- Concentration in vehicle: 12.5, 87.5, 250 mg/ml
- Amount of vehicle (if gavage): 4 ml/kg
- Lot/batch no. (if required): No data available.
- Purity: No data available.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The concentration, homogeneity and stability of test material in the test material formulations was determined by high performance liquid chromatography (HPLC) using an external standard technique.

Homogeneity Determinations
- The test material formulations were mixed thoroughly and samples were taken from the top, middle and bottom of the container, shaking between sampling. Sampling for homogeneity determinations was performed in triplicate.

Stability Determinations
- The test formulation were sampled and analyzed initially and then after storage at approximately 4 oC in the dark for 21 days.

Verification of Test Material Formulation Concentrations
- The test material formulations were sampled and analyzed within 2 days of preparation.

Method Validation
- The analytical method has been satisfactorily validated in terms of linearity, specificity and accuracy for the purposes of the study.

Duration of treatment / exposure:

The test material was administered to four groups each of ten male and ten female rats, for up to fifty-four consecutive days

Frequency of treatment:

Daily

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
50 mg/kg/day
Basis:
actual ingested

Doses / concentrations 2

Remarks:

Doses / Concentrations:
350 mg/kg/day
Basis:
actual ingested

Doses / concentrations 3

Remarks:

Doses / Concentrations:
1000 mg/kg/day
Basis:
actual ingested

No. of animals per sex per dose:

10 animals per sex per dose (including control).

Control animals:

yes, concurrent vehicle

Details on study design:

Chronological Sequence of Study
Dose Groups 1 to 4
i) Groups of ten male and ten female animals were treated daily at the appropriate dose level throughout the study (except for females during parturition where applicable). The first day of dosing was designated as Day 1 of the study.
ii) Prior to the start of treatment and once weekly thereafter, all animals were observed for signs of functional/behavioural toxicity.
iii) One day prior to pairing (Day 14), blood samples were taken from five males and five females, randomly selected from each dose group and analysed for
haematological and blood chemical assessment.
iv) On Day 15, animals were paired on a 1 male: 1 female basis within each dose
group for a maximum of fourteen days.
v) Following evidence of mating (designated as Day 0 post coitum) the males were returned to their original cages and females were transferred to individual cages.
vi) On completion of mating (during Week 6), five selected males per dose group
were evaluated for functional/sensory responses to various stimuli.
vii) Pregnant females were allowed to give birth and maintain their offspring until Day 5 post partum. Evaluation of each litter size, litter weight, mean offspring weight by sex, clinical observations and landmark developmental signs were also performed during this period.
viii) At Day 4 post partum, five selected females per dose group were evaluated for functional/sensory responses to various stimuli.
ix) Additional blood samples were taken from five males from each dose group for haematological and blood chemical assessments on Day 42. Following completion of the female gestation and lactation phases, the male dose groups were killed and examined macroscopically.
x) Additional blood samples were taken from five randomly selected females from each dose group at termination for haematological and blood chemical assessment on Day 4 post partum. At Day 5 post partum, surviving females and offspring were killed and examined macroscopically.

- Dose selection rationale: The dose levels were chosen based on the results of a preliminary range-finder performed as part of the study.

- Rationale for animal assignment (if not random): The animals were randomly allocated to treatment groups using a stratified bodyweight randomisation procedure and the group mean bodyweights were then determined to ensure similarity between the treatment groups. The cage distribution within the holding rack was also randomised. The animals were uniquely identified within the study by an ear punching system routinely used in these laboratories..

- Rationale for selecting satellite groups: Not applicable

- Post-exposure recovery period in satellite groups: Not applicable
- Section schedule rationale (if not random): Not applicable

Positive control:

Not applicable

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Immediately before dosing, up to thirty minutes after dosing, and one and five hours afterdosing, during the working week. Animals were observed immediately before dosing, soon after dosing, and one hour after dosing at weekends and public holidays (except forfemales during parturition where applicable).

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Immediately before dosing, up to thirty minutes after dosing, and one and five hours afterdosing, during the working week. Animals were observed immediately before dosing,soon after dosing, and one hour after dosing at weekends and public holidays (except forfemales during parturition where applicable).

BODY WEIGHT: Yes
- Time schedule for examinations: Individual bodyweights were recorded on Day 1 (prior to dosing) and then weekly for males until termination and weekly for females until mating was evident. Bodyweights were then recorded for females on Days 0, 7, 14 and 20 post coitum, and on Days 1 and 4 post partum.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes.
During the maturation period, weekly food consumption was recorded for each cage of adults. This was continued for males after the mating phase. For females showing evidence of mating, food consumption was recorded for the periods covering Days 0-7, 7-14 and 14-20. For females with live litters, food consumption was recorded on Days 1 and 4 post partum.

- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Group mean weekly food consumptions
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No data

FOOD EFFICIENCY: Yes.
- Food efficiency (the ratio of bodyweight change/dietary intake) was calculated retrospectively for males throughout the study period and for females during maturation and the first two weeks of gestation. Due to offspring growth and milk production, food efficiency could not be accurately calculated during the final week of gestation and during lactation.
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No data


WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes.
- Time schedule for examinations: Water intake was observed daily by visual inspection of water bottles for any overt changes.

OPHTHALMOSCOPIC EXAMINATION: No
- Time schedule for examinations: Not applicable
- Dose groups that were examined: Not applicable

HAEMATOLOGY: Yes.
- Time schedule for collection of blood: Haematological and blood chemical investigations were performed on five males and five females selected from each non-recovery test and control group on Day 14 (day prior to pairing) and prior to termination (Day 42 for males and Day 4 post partum for females).
- Anaesthetic used for blood collection: No data
- Animals fasted: No
- How many animals: five males and five females selected from each test and control group
- Parameters were examined:
Haemoglobin (Hb)
Erythrocyte count (RBC)
Haematocrit (Hct)
Erythrocyte indices
- mean corpuscular haemoglobin (MCH)
- mean corpuscular volume (MCV)
- mean corpuscular haemoglobin concentration (MCHC)
Total leucocyte count (WBC)
Differential leucocyte count - neutrophils (Neut)
- lymphocytes (Lymph)
- monocytes (Mono)
- eosinophils (Eos)
- basophils (Bas)
Platelet count (PLT)
Prothrombin time (CT) was assessed by ‘Innovin’ and Activated partial thromboplastin
time (APTT) was assessed by ‘Actin FS’ using samples collected into sodium citrate solution (0.11 mol/l).

CLINICAL CHEMISTRY: Yes.
- Time schedule for collection of blood: Haematological and blood chemical investigations were performed on five males and five females selected from each non-recovery test and control group on Day 14 (day prior to pairing) and on Day 42. In addition haematological and blood chemical investigations were performed on all recovery group animals after the fourteen day treatment free period at termination (Day 56). Blood samples were obtained from the lateral tail vein at Day 14 and by cardiac puncture at termination.
- Animals fasted: No
- How many animals: five males and five females selected from each non-recovery test and control group
- Parameters were examined:
Urea
Calcium (Ca++)
Glucose
Inorganic phosphorus (P)
Total protein (Tot. Prot.)
Aspartate aminotransferase (ASAT)
Albumin
Alanine aminotransferase (ALAT)
Albumin/Globulin (A/G) ratio (by calculation)
Alkaline phosphate (AP)
Sodium (Na+)
Creatinine (Creat)
Potassium (K+)
Total cholesterol (Chol)
Chloride (Cl¯)
Total bilirubin (Bili)

URINALYSIS: not examined.
- Time schedule for collection of urine: No data
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- Parameters were examined: No data

NEUROBEHAVIOURAL EXAMINATION: Yes.
- Time schedule for examinations:
(Behavioural assessment) Prior to the start of treatment and at weekly intervals thereafter
(Functional Performance Tests) Prior to termination
(Sensory Reactivity) Prior to termination

- Dose groups that were examined:
(Behavioural assessment) All animals
(Functional Performance Tests) Five selected males and females per dose level
(Sensory Reactivity) Five selected males and females per dose level- Parameters examined.
(Behavioural assessment) Detailed individual clinical observations were performed for each animal using a purpose-built arena.

- The following parameters were observed:
Gait
Hyper/Hypothermia
Tremors
Skin colour
Twitches
Respiration
Convulsions
Palpebral closure
Bizarre/Abnormal/Stereotypic behaviour
Urination
Salivation
Defecation
Pilo-erection
Transfer arousal
Exophthalmia
Tail elevation
Lachrymatation

(Functional Performance Tests)
- Motor Activity. Purpose-built 44 infra-red beam automated activity monitors were usedto assess motor activity. Animals were randomly allocated to the activity monitors. Thetests were performed at approximately the same time each day, under similar laboratoryconditions. The evaluation period was thirty minutes for each animal. The time in seconds each animal was active and mobile was recorded for the overall thirty minute periodand also during the final 20% of the period (considered to be the asymptotic period).
- Forelimb/Hindlimb Grip Strength. An automated meter was used. Each animal was allowed to grip the proximal metal bar of the meter with its forepaws. The animal was pulled by the base of the tail until its grip was broken. The animal was drawn along thetrough of the meter by the tail until its hind paws gripped the distal metal bar. The animalwas pulled by the base of the tail until its grip was broken. A record of the force requiredto break the grip for each animal was made. Three consecutive trials were performed foreach animal.
- (Sensory Reactivity) Animals were assessed for sensory reactivity to auditory, visual and proprioceptive stimuli. The following parameters were observed:
Grasp response,
Touch escape,
Vocalisation,
Pupil reflex,
Toe pinch,
Startle reflex,
Tail pinch,
Blink reflex
Finger approach

Sacrifice and pathology:

Sacrifice and pathology
Adult males were killed by intravenous overdose of a suitable barbiturate agent followed by exsanguination on Day 43. Adult females were killed by intravenous overdose of a suitable barbiturate agent followed by exsanguination on Day 5 post partum. Surviving offspring were terminated via intracardiac overdose of sodium pentobarbitone. Any females which failed to achieve pregnancy or produce a litter were killed on or after Day 26 post coitum.
For all females, the uterus was examined for signs of implantation and the number of uterine implantations in each horn was recorded. This procedure was enhanced; as necessary, by staining the uteri with a 0.5% ammonium polysulphide solution.
All adult animals and offspring, including those dying during the study, were subjected to
a full external and internal examination, and any macroscopic abnormalities were recorded.

GROSS PATHOLOGY: Yes.
The following organs, removed from animals that were killed at the end of the study, were dissected free from fat and weighed before fixation:
Adrenals Ovaries Brain Spleen Epididymides Testes Heart Thymus Kidneys Thyroid
Liver

HISTOPATHOLOGY: Yes.
Samples of the following tissues were removed from all animals and preserved in buffered 10% formalin except where stated:
Adrenals
Aorta (thoracic)
Bone & bone marrow (femur including stifle joint)
Bone & bone marrow (sternum)
Brain (including cerebrum, cerebellum and pons)
Caecum
Coagulation gland
Colon
Duodenum
Epididymides
Eyes
Gross lesions
Heart
Ileum (including peyer’s patches)
Jejunum
Kidneys
Liver
Lungs (with bronchi) #
Lymph nodes (cervical and mesenteric)
Mammary gland
Muscle (skeletal)
Ovaries
Pancreas
Pituitary
Prostate
Oesophagus
Rectum
Salivary glands (submaxillary)
Sciatic nerve
Seminal vesicles
Skin (hind limb)
Spinal cord (cervical, mid-thoracic and lumbar)
Spleen
Stomach
Thyroid/parathyroid
Trachea
Testes
Thymus
Urinary bladder
Uterus/Cervix
Vagina

Other examinations:

None.

Statistics:

For males and females during the pre-mating phase, quantitative data were analysed by the Provantis™ Tables and Statistics Module. For each variable, the most suitable transformation of the data was found, the use of possible covariates checked and the homogeneity of means assessed using ANOVA and ANCOVA and Barletts’s test. The transformed data were analysed to find the lowest treatment level that showed a significant effect, using the Williams Test for parametric data or the Shirley Test for non-parametric data. If no dose response was found, but the data showed nonhomogeneity of means, the data were analysed by a stepwise Dunnett (parametric) or Steel (non parametric) test to determine significant differences from the control group. Finally, if required, pair-wise tests were performed using the Student t-test (parametric) or the Mann-Whitney U test (non-parametric).
Data for females during gestation and lactation, and offspring data were assessed for dose response relationships by linear regression analysis, followed by one way ANOVA incorporating Levene’s test for homogeneity of variance. Where variances were shown to be homogenous, pairwise comparisons were conducted using Dunnett’s test. Where Levene’s test showed unequal variances the data were analysed using non-parametric methods: Kruskal-Wallis ANOVA and Mann-Whitney ‘U’ test.
Non-parametric methods were used to analyse implantation loss, offspring sex ratio and landmark developmental markers.
Histopathology data were analysed (excluding any decedents, nonmated females and females not producing a pregnancy/litter) using the following methods to determine significant differences between control and treatment groups for the individual sexes:
1. Chi-squared analysis for differences in the incidence of lesions occurring with an overall frequency ≥ 1.
2. Kruskal-Wallis one-way non-parametric analysis of variance for the comparison of severity grades for the more frequently observed graded conditions.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

no effects observed

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

see "Details on results"

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

see "Details on results"

Histopathological findings: neoplastic:

no effects observed

Details on results:

Mortality.
One male treated with 350 mg/kg/day was found dead on Day 35. One female
from this treatment group was also terminated early due to an unscheduled mating on Day 18.
There were no further unscheduled deaths during the study.

Clinical Signs.
No clinical signs of toxicity were detected.

Bodyweights.
No adverse effects on bodyweight development were detected.

Food Consumption and Food Efficiency.
No adverse effects on food consumption or food efficiency were detected.

Water Consumptions. No significant intergroup differences were detected.
No intergroup differences were detected.

Ophthalmoscopic Examination
Not examined.

Haematology.
No toxicologically significant effects were detected in the haematological parameters measured.

Blood Chemistry.
No toxicologically significant effects were detected in the blood chemical parameters measured.

Urinalysis.
Not examined.

Behavioural Assessment.
There were no treatment-related changes in the behavioural parameters measured.

Functional Performance Tests.
There were no treatment-related changes in functional performance.

Sensory Reactivity Assessments.
There were no treatment-related changes in sensory reactivity.

Necropsy.
The male treated with 350 mg/kg/day that was found dead on Day 35 had reddened lungs and fluid in the thoracic cavity.

Organ Weights.
No toxicologically significant effects were detected in the organ weights measured.

Histopathology - non-neoplastic.
The following treatment-related effects were detected:
LIVER: Centrilobular hepatocyte enlargement was seen in relation to treatment for males only treated with 1000 mg/kg/day.
Hepatocyte enlargement is commonly observed in the rodent liver following the administration of xenobiotics and, in the absence of associated inflammatory or degenerative changes, is generally considered to be adaptive in nature.
KIDNEY: A higher incidence of globular accumulations of eosinophilic material was observed in the tubular epithelium of males treated with 1000 or 350 mg/kg/day. A slightly higher incidence of the condition was also seen for males treated with 50 mg/kg/day compared with the control group, but this condition is seen occasionally as a spontaneous change and an effect of treatment at the low dose was not convincing. This finding is consistent with the presence of hydrocarbon nephropathy, which results from the excessive accumulation of α2-microglobulin in renal proximal tubular epithelial cells. α2-Microglobulin is found only in the proximal tubular epithelium of adult male rats.


HISTOPATHOLOGY: NEOPLASTIC (if applicable) Not applicable.
HISTORICAL CONTROL DATA (if applicable) Not applicable.
OTHER FINDINGS

Effect levels

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The oral administration of test material to rats by gavage, at dose levels of 1000, 350 and 50 mg/kg/day, resulted in treatment-related effects at 1000 and 350 mg/kg/day. These effects were considered not to represent an adverse effect of treatment, hence the NOAEL for systemic toxicity was considered to be 1000 mg/kg/day.

Executive summary:

Introduction.The study was designed to investigate the systemic toxicity and potential adverse effects of the test material on reproduction (including offspring development) and complies with the recommendations of the OECD Guidelines for Testing of Chemicals No. 422 “Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test” .

 

Methods.The test material was administered by gavage to three groups each of ten male and ten female Wistar Han™:HsdRccHan™:WIST strain rats, for up to fifty-four consecutive days (including a two week maturation phase, pairing, gestation and early lactation for females), at dose levels of 50, 350 and 1000 mg/kg/day. A control group of ten males and ten females was dosed with vehicle alone (Arachis oil BP).

Clinical signs, behavioural assessments, bodyweight development, food and water consumption were monitored during the study. Haematology and blood chemistry were evaluated prior to mating and at termination on five selected males and females from each dose group.

Pairing of animals within each dose group was undertaken on a one male: one female basis within each treatment group on Day 15 of the study, with females subsequently being allowed to litter and rear their offspring to Day 5 of lactation.

During the lactation phase, daily clinical observations were performed on all surviving offspring, together with litter size and offspring weights and assessment of surface righting reflex.

Extensive functional observations were performed on five selected males from each dose group after the completion of the mating phase, and for five selected parental females from each dose group on Day 4post partum.

Males were terminated on Day 43, followed by the termination of all surviving females and offspring on Day 5post partum. All animals were subjected to a gross necropsy examination and histopathological evaluation of selected tissues was performed.

Results.

Mortality.One male treated with 350 mg/kg/day was found dead on Day 35. One female from this treatment group was also terminated early due to an unscheduled mating on Day 18.

There were no further unscheduled deaths during the study.

Clinical Observations.No clinical signs of toxicity were detected.

Behavioural Assessment.There were no treatment-related changes in the behavioural parameters measured.

Functional Performance Tests.There were no treatment-related changes in functional performance.

Sensory Reactivity Assessments.There were no treatment-related changes in sensory reactivity.

Bodyweight.No adverse effects on bodyweight development were detected.

Food Consumption.No adverse effects on food consumption or food efficiency were detected.

Water Consumption.No intergroup differences were detected.

Haematology.No toxicologically significant effects were detected in the haematological parameters measured.

Blood Chemistry.No toxicologically significant effects were detected in the blood

chemical parameters measured.

Organ Weights.No toxicologically significant effects were detected in the organ weights measured.

Necropsy.The male treated with 350 mg/kg/day that was found dead on Day 35 had reddened lungs and fluid in the thoracic cavity.

Histopathology.The following treatment-related effects were detected:

LIVER: Centrilobular hepatocyte enlargement was seen in relation to treatment for males only treated with 1000 mg/kg/day.

Hepatocyte enlargement is commonly observed in the rodent liver following the administration of xenobiotics and, in the absence of associated inflammatory or degenerative changes, is generally considered to be adaptive in nature.

KIDNEY: A higher incidence of globular accumulations of eosinophilic material was observed in the tubular epithelium of males treated with 1000 or 350 mg/kg/day. A slightly higher incidence of the condition was also seen for males treated with

50 mg/kg/day compared with the control group, but this condition is seen occasionally as a spontaneous change and an effect of treatment at the low dose was not convincing.

This finding is consistent with the presence of hydrocarbon nephropathy, which results from the excessive accumulation ofα2-microglobulin in renal proximal tubular epithelial cells.α2-Microglobulin is found only in the proximal tubular epithelium of adult male rats.

Conclusion.The oral administration of test material to rats by gavage, at dose levels of 1000, 350 and 50 mg/kg/day, resulted in treatment-related effects at 1000 and 350 mg/kg/day. These effects were considered not to represent an adverse effect of treatment, hence the 'No Observed Adverse Effect Level' (NOAEL) for systemic toxicity was considered to be 1000 mg/kg/day.