Benzene, mono-C10-13-alkyl derivs., distn. residues

Endpoint summary

Description of key information

Two key studies determined the sub-chronic toxicity of HAB to rats. In the first study (Charles River 2007), groups of rats were exposed by oral gavage to concentrations of 0, 250, 500 or 1000 mg/kg/day of test substance. Males were exposed daily for 39 days, and females were exposed daily through lactation day 4. Animals were observed regularly for body weight, mortality, clinical signs, food consumption, and behaviour. At the end of the study, the animals were sacrificed and examined for gross pathology, organ weights, histopathology, clinical chemistry, hematology, and urinalysis parameters. Adverse effects were seen in the thymus at all dose levels, however, these changes are most likely stress related and are considered to be of minimal toxicological significance. Body weight reduction was seen in male rats at the 1000 mg/kg/day dose level. Thus, the LOAEL for male rats was determined to be 1000 mg/kg/day, making the NOAEL 500 mg/kg/day. No adverse effects were seen in female rats, therefore, the NOAEL for female rats is 1000 mg/kg/day.  The following summarizes the details of the results:

Mortality: No treatment-related mortalities were observed. One early sacrifice occurred in one male rat as the result of an injury. No treatment-related clinical signs were observed in the F0 male and female rats and F1 generation rats (main and recovery portions of the study).

Body Weight: Body weight gains of the male rats assigned to the main study were significantly reduced for the entire study (DSs 1 to 39) in the 1000 mg/kg/day dosage group. No reductions in body weight or body weight gain was observed in the male rats assigned to the recovery portion as high as 1000 mg/kg/day. No effects on body weight or body weight gain were observed in the female rats during any stage of the study at doses up to and including 1000 mg/kg/day.

Feed Consumption: No effects were observed on the absolute or relative feed consumption for either sex a high as 1000 mg/kg/day.

Reproduction: No effects were observed on estrous, mating, fertility, natural delivery or litter observations at any dose.

Behavior and Motor Activity: No effects on any of the parameters examined in the FOB, motor activity or urinalysis were observed.

Clinical Chemistry: There were no statistically significant or biologically important differences in the urinalysis, haematology or clinical chemistry parameters.

Organ Weights: No statistically significant differences were observed in organ weights, the ratio (%) of organ weights to terminal body weights, or the ratio (%) of organ weights to brain weights in either sex at any dose.

Microscopic Effects: Treatment-related microscopic changes were observed in the thyroid of male and female rats at all dosage levels and in the thymus of the 1000 mg/kg/day dosage group female rats. No other treatment-related microscopic changes were observed. The changes in the thyroid consisted of hyperplasia and hypertrophy of the follicular epithelial cells. These microscopic changes occurred in a dose-responsive manner. According to various sources, the thyroid of rats is susceptible to environmental variations that are reversible and considered of minimal toxicological significance. Thyroid changes may be a response to stress, and therefore, a combination of dosing and stress may have contributed to the effects seen in this study (e.g., Cotchin and Roe 1967; Haschek and Rousseaux 1991). Microscopically, the thymus was reduced in size due to atrophy of the cortical and medullary lymphoid lobules in the 1000 mg/kg/day dosage group (females only). No atrophy was observed in the males of any dosage group or the females in the 250 and 500 mg/kg/day groups. Thymic atrophy or decreased cellularity is a relatively nonspecific finding in young rats, but is often associated with stress and can occur in young rats with significant decreased weight gain or loss.

In the second key study (Naylor and Ruecker 1988), a 90-day rat oral toxicity test to determine the effects of dietary exposure to the test substance was done. Groups of 20 male and female rats were fed diets containing 0, 1000, 8000, or 20,000 ppm (corresponding to 0, 45, 360 and 900 mg/kg bw/day) of test substance for 90 days. During the exposure period, the animals were observed for mortality, clinical signs, body weight, and food consumption. At 45 days, and at the end of the study at 90 days, blood samples were drawn and analyzed for hematological and clinical chemistry parameters. At the study termination at day 90, the animals were sacrificed and examined for gross pathology and histopathology. There were no treatment related deaths or clinical signs. There was reduced weight gain in middle and high dose females, and high dose males. Middle and high dose females had increased liver weights, and middle and high dose males had increased kidney weights. Based on these effects the LOAEL for both males and females was 8000 ppm. The NOAEL for both males and females was 1000 ppm.  Additional details of the results:

Clinical signs and mortality: There was no mortality, and no treatment related clinical signs observed during the study.

Body weight and weight gain: There was reduced weight gain in middle and high dose females. The body weights of these females were significantly lower by the end of the study. High dose males also had reduced body weight gain.

Food consumption: Females at the middle and high dose levels, and males at the high dose level exhibited decreased food consumption during the first week. The food consumption of these animals improved, but remained low throughout the study.

Ophthalmoscopic examination: No treatment related effects were observed.

Haematology: Mean corpuscular volume was decreased in high and middle dose females at the terminal sampling. Platelet counts were slightly increased in these groups at both samplings. No other treatment related effects were seen. There were no treatment related effects in males.

Clinical chemistry: High dose males and females showed a slight decrease in total protein due to slight decreases in albumin and/or globin at the terminal sampling. Cholesterol was decreased in high dose males at the terminal sampling, and high dose females in the interim sampling. Glucose was slightly decreased in middle and high dose females at both samplings.

Organ weights: Absolute and relative kidney weights were increased in middle and high dose males. Absolute and relative liver weights were increased in middle and high dose females. No other treatment related effects were observed.

Gross pathology: No gross changes attributable to treatment were observed.

Histopathology: Non-neoplastic: No histophathological changes attributable to treatment were observed.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Dec. 19, 1986

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

GLP compliance:

yes (incl. QA statement)

Limit test:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratory, Portage MI
- Age at study initiation: 6 weeks
- Weight at study initiation: Males 157.9-186.1 g, Females 124.8 - 144.5 g
- Housing: individually in stainless steel cages, identified by ear tag
- Diet (e.g. ad libitum): Ralston Purina Certified Rodent Chow #5002, ad libitum
- Water (e.g. ad libitum): ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 70-74 degree F
- Humidity (%): 35-60%
- Photoperiod (hrs dark / hrs light): 12 hrs light/12 hrs dark


IN-LIFE DATES: From: Dec. 19, 1986

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

DIET PREPARATION
- Rate of preparation of diet (frequency): weekly
- Mixing appropriate amounts with (Type of food): Ralston Purina Certified Rodent Chow #5002

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Duplicate samples were taken from the top, middle, and bottom of the mixer. Test substance was extracted with iso-octane, and analyzed by gas chromatography with flame ionization detector. Stability of mixture was tested by analyzing samples from the low and high dose levels at 33 days storage in a closed container, and 7 and 18 days in an open container.

Duration of treatment / exposure:

90 days

Frequency of treatment:

daily

Remarks:

Doses / Concentrations:
1000, 8000, 20,000 ppm
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
970, 8000, 21,000 ppm
Basis:
other: analytical concentration

Remarks:

Doses / Concentrations:
45, 360, 900 mg/kg bw/day
Basis:
nominal in diet

No. of animals per sex per dose:

20 animals per sex per dose

Control animals:

yes, plain diet

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily
- Cage side observations checked: mortality and morbundity


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: once weekly


BODY WEIGHT: Yes
- Time schedule for examinations: weekly


FOOD CONSUMPTION: Yes
- Time schedule for examinations: weekly

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: pretest and prior to sacrifice
- Dose groups that were examined: all groups


HAEMATOLOGY: Yes
- Time schedule for collection of blood: day 45, and termination
- Anaesthetic used for blood collection: Yes
- How many animals: day 45 - 8 per sex per dose, termination - all animals
- Parameters examined: total erythrocyte count, total leucocyte count, platelet count, hematocrit, hemoglobin level, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, reticulocyte count


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: day 45, and termination
- How many animals: day 45 - 8 per sex per dose, termination - all animals
- Parameters examined: albumin, total protein, blood urea nitrogen, total bilirubin, direct bilirubin, glucose, glutamic pyruvic transaminase, alkaline phosphatase, glutamic oxaloacetate transaminase, creatinine, cholesterol, calcium, phosphorus, chloride, sodium, and potassium

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
Adrenals, brain, kidneys, liver, and testes with epididymides were weighed in addition to internal and external examination.

HISTOPATHOLOGY: Yes
Lungs from all animals were examined. The following organs were examined in animals from the control and high dose groups: aorta, adrenals, bone and bone marrow, brain, caecum, colon, duodenum, esophagus, eyes, heart, ileum, jejunum, kidneys, lesions, abnormal masses, liver, lung, lymph node, muscle, ovaries, pancreas, pituitary gland, prostate, rectum, sciatic nerve, seminal vesicles, skin, spinal cord, spleen, stomach, submaxillary salivary gland, testes with epididymides, thymus, thyroid and parathyroid, trachea, uterus, urinary bladder

Statistics:

Dunnett's Multiple Comparison Test: body weights, food consumption, noncategorical clinical pathology data, absolute organ weights
Mann-Whitney Test with Bonferroni Inequality Procedure: organ weight/body weight ratios
Fisher's Exact Test with Bonferroni Inequality Procedure: incidence of microscopic lesions

Other analyses used were Bartlett's Test, Analysis of Variance, and Grubb's Test.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

no effects observed

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY
There was no mortality, and no treatment related clinical signs observed during the study.

BODY WEIGHT AND WEIGHT GAIN
There was reduced weight gain in middle and high dose females. The body weights of these females were significantly lower by the end of the study. High dose males also had reduced body weight gain.

FOOD CONSUMPTION
Females at the middle and high dose levels, and males at the high dose level exhibited decreased food consumption during the first week. The food consumption of these animals improved, but remained low throughout the study.

OPHTHALMOSCOPIC EXAMINATION
No treatment related effects were observed.

HAEMATOLOGY
Mean corpuscular volume was decreased in high and middle dose females at the terminal sampling. Platelet counts were slightly increased in these groups at both samplings. No other treatment related effects were seen. There were no treatment related effects in males.

CLINICAL CHEMISTRY
High dose males and females showed a slight decrease in total protein due to slight decreases in albumin and/or globin at the terminal sampling. Cholesterol was decreased in high dose males at the terminal sampling, and high dose females in the interim sampling. Glucose was slightly decreased in middle and high dose females at both samplings.

ORGAN WEIGHTS
Absolute and relative kidney weights were increased in middle and high dose males. Absolute and relative liver weights were increased in middle and high dose females. No other treatment related effects were observed.

GROSS PATHOLOGY
No gross changes attributable to treatment were observed.

HISTOPATHOLOGY: NON-NEOPLASTIC
No histophathological changes attributable to treatment were observed.

Dose descriptor:

NOAEL

Effect level:

1 000 other: ppm diet

Sex:

male/female

Basis for effect level:

organ weights and organ / body weight ratios

Dose descriptor:

LOAEL

Effect level:

8 000 ppm

Sex:

male/female

Basis for effect level:

organ weights and organ / body weight ratios

Critical effects observed:

not specified

Body Weights

Group (ppm)	Study Mean (g)	% Difference from Control Study Mean	% Difference from Control Final Body Weight	% Gain from Initial
Males
0	401.9			218
1000	396.0	-1.5	-3.6	207
8000	393.4	-2.1	-3.3	208
20,000	374.1	-6.9	-10.4	185
Females
0	220.7			98
1000	217.5	-1.4	-1.8	95
8000	198.8	-9.9	-13.0	73
20,000	193.8	-12.2	-16.2	66

Conclusions:

The 90-day NOAEL for male and female rats was 1000 ppm in the diet. The 90-day LOAEL for male and female rats was 8000 ppm in the diet based on increased kidney weights (males) and increased liver weights (females).

Executive summary:

A 90 -day oral toxicity to determine the effects of dietary exposure to Therminol 55 to rats was done. Groups of 20 male and female rats were fed diets containing 0, 1000, 8000, or 20,000 ppm of test substance for 90 days. During the exposure period, the animals were observed for mortality, clinical signs, body weight, and food consumption. At 45 days, and at the end of the study at 90 days, blood samples were drawn and analyzed for hematological and clinical chemistry parameters. At the study termination at day 90, the animals were sacrificed and examined for gross pathology and histopathology. There were no treatment related deaths or clinical signs. There was reduced weight gain in middle and high dose females, and high dose males. Middle and high dose females had increased liver weights, and middle and high dose males had increased kidney weights. Based on these effects the LOAEL for both males and females was 8000 ppm. The NOAEL for both males and females was 1000 ppm.

Reference 2

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2007

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study.

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes

Species:

rat

Strain:

other: Crl:CD(SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

Housing and Husbandry: F0 generation rats assigned to the main satellite/recovery mated portions of the study were individually housed in stainless steel, wire-bottomed cages, except during the cohabitation and postpartum periods. During cohabitation, each pair of male and female rats was housed in the male rat's cage. Beginning no later than gestation day (DG) 20, F0 generation female rats assigned to natural delivery were individually housed in nesting boxes. The study room was maintained under conditions of positive airflow, temperature and humidity were monitored and maintained. Animals were given standard diet and water ad libitum under a 12 hour light and 12 hour dark photoperiod.

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

Stock Preparation: A blended stock suspension was prepared once at the testing facility and stored at room temperature, protected from light. Suspensions of the blended test substance and/or vehicle for dosage administration were prepared daily and also stored at room temperature, protected from light. Prepared formulations were stirred continuously during dosage administration.

Dosage Selection: Doses were selected on the basis of results from a range-finding study. In that study there were no mortalities at doses as high as 2000 mg/kg/day. Body weight gains of the males only were reduced in the 1000 and 2000 mg/kg/day groups during the first week, and although they subsequently rebounded, the early reductions resulted in overall reduction at the end of the test period. Therefore, doses of 0, 250, 500 and 1000 mg/kg/day were selected for the definitive test.

Duration of treatment / exposure:

at least 39 days (males); through lactation day 4 (females)

Frequency of treatment:

daily

Remarks:

Doses / Concentrations:
0 (corn oil vehicle), 250, 500 and 1000 mg/kg/day
Basis:
other: nominal

Control animals:

yes, concurrent vehicle

Details on study design:

Method Overview: Sixty male and 80 female rats were randomly assigned to four dosage groups, 15 male rates and 20 female rats per dosage group. The test material was administered orally (via gavage) on a daily basis beginning 14 days before a 14 day cohabitation period. Dosage continued through the day prior to sacrifice, after completion of the cohabitation period (minimum of 39 days of administration). In female rats, dosage continued up to and including day 4 of lactation. Male and female rats assigned to the satellite recovery portion of the study were not administered the test substance and/or the vehicle for 14 days prior to sacrifice starting when the first main study female rat assigned to the main study reached day 4 of lactation.

Observations and examinations performed and frequency:

Parameters Evaluated: All of the main and recovery rats were examined for viability, clinical observations, detailed clinical observations (main study rats only), body weight and body weight changes and feed consumption values. Maternal behavior was observed at various times for specific purposes. In addition, each litter was evaluated for viability at least twice daily and clinical observations once daily. Each litter was counted once daily. Pup weights were recorded on lactation days (DL) 1 and 4 for litters of dams assigned to the main study hematology and clinical chemistry portion of the study. Pup body weights were also recorded periodically for various purposes. Urine and blood samples were collected for evaluation periodically and a functional observational battery (FOB) and motor activity assessment was conducted on study day (DS) 40 (male rats) or DL5 (female rats). All surviving main study rats were sacrificed on the day following the last administration of the test substance and/or the vehicle, after a minimum of 39 days of dosage. Satellite/recovery mated female rats were sacrificed on DL18. Satellite/recovery non-mated male and female rats were Sacrificed 4 days after the first main study rat reached DL4.

Sacrifice and pathology:

Necropsy: The following tissues were weighed and/or retained from all rats: liver, kidneys, testes, epididymides, seminal vesicles with coagulation gland and prostate (male only), and ovaries, vagina, a mammary gland and uterus with cervix. The following tissues were retained from the five male and female rats (main study) assigned to hematology, clinical biochemistry and histological evaluations: small and large intestines (Peyer's patches), lungs, trachea, esophagus, mandibular and mesenteric lymph nodes, peripheral nerve (sciatic), stomach, seminal vesicles with coagulating gland, spinal cord, thyroid, urinary bladder, prostate, vagina and a mammary gland, bone marrow and gross lesions. Additionally, the brain, adrenals, spleen, thymus and heart were weighed and retained for possible histological evaluation from the five male and female rats (main study) assigned to hematology, clinical biochemistry and histological evaluations. All gross lesions were examined histologically. Histological examination was performed on all (main study rats assigned to clinical chemistry evaluation only) control and high test substance dose group rats, and on the thymus and thyroids from all in the 250, 500 and 1000 mg/kg/day dosage groups. Pups that died were examined and/or preserved for future analysis. On DL4, pups from litters of dams assigned to the clinical chemistry and hematology portion of the study were sacrificed, as were pups from litters of dams assigned
to the FOB portion of the study on DL5. Necropsies were performed.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

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:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Details on results:

Mortality: No treatment-related mortalities were observed. One early sacrifice occurred in one male rat as the result of an injury. No treatment-related clinical signs were observed in the F0 male and female rats and F1 generation rats (main and recovery portions of the study).

Body Weight: Body weight gains of the male rats assigned to the main study were significantly reduced for the entire study (DSs 1 to 39) in the 1000 mg/kg/day dosage group. No reductions in body weight or body weight gain was observed in the male rats assigned to the recovery portion as high as 1000 mg/kg/day. No effects on body weight or body weight gain were observed in the female rats during any stage of the study at doses up to and including 1000 mg/kg/day. Summary data for the male rats is shown in the table below; full data are in the study report.

Feed Consumption: No effects were observed on the absolute or relative feed consumption for either sex a high as 1000 mg/kg/day.

Reproduction: No effects were observed on estrous, mating, fertility, natural delivery or litter observations at any dose.

Behavior and Motor Activity: No effects on any of the parameters examined in the FOB, motor activity or urinalysis were observed.

Clinical Chemistry: There were no statistically significant or biologically important differences in the urinalysis, hematology or clinical chemistry parameters.

Organ Weights: No statistically significant differences were observed in organ weights, the ratio (%) of organ weights to terminal body weights, or the ratio (%) of organ weights to brain weights in either sex at any dose.

Microscopic Effects: Treatment-related microscopic changes were observed in the thyroid of male and female rats at all dosage levels and in the thymus of the 1000 mg/kg/day dosage group female rats. No other treatment-related microscopic changes were observed. The changes in the thyroid consisted of hyperplasia and hypertrophy of the follicular epithelial cells. These microscopic changes occurred in a dose-responsive manner. According to various sources, the thyroid of rats is susceptible to environmental variations that are reversible and considered of minimal toxicological significance. Thyroid changes may be a response to stress, and therefore, a combination of dosing and stress may have contributed to the effects seen in this study (e.g., Cotchin and Roe 1967; Haschek and Rousseaux 1991). Microscopically, the thymus was reduced in size due to atrophy of the cortical and medullary lymphoid lobules in the 1000 mg/kg/day dosage group (females only). No atrophy was observed in the males of any dosage group or the females in the 250 and 500 mg/kg/day groups. Thymic atrophy or decreased cellularity is a relatively nonspecific finding in young rats, but is often associated with stress and can occur in young rats with significant decreased weight gain or loss. Total incidence of thymus and thyroid observations are shown below.

Dose descriptor:

NOAEL

Effect level:

500 mg/kg bw/day (nominal)

Sex:

male

Basis for effect level:

body weight and weight gain

Dose descriptor:

LOAEL

Effect level:

1 000 mg/kg bw/day (nominal)

Sex:

male

Basis for effect level:

body weight and weight gain

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (nominal)

Sex:

female

Basis for effect level:

other:

Remarks on result:

not determinable due to absence of adverse toxic effects

Critical effects observed:

not specified

Dose Group	I	II	III	IV	I	II	III	IV
Sex	Males				Females
No. Animals	5	5	5	5	5	4	5	5
Thymus
No. Examined	5	5	5	5	5	3	5	5
No. Normal	5	5	5	5	5	3	5	0
- atrophy, focal [total]	[0]	[0]	[0]	[0]	[0]	[0]	[0]	[5]
- minimal	0	0	0	0	0	0	0	2
- mild	0	0	0	0	0	0	0	3
Thyroid
No. Examined	5	5	5	5	4	4	5	5
No. Normal	5	4	2	1	3	2		1
- cyst(s), ultimobrancial	0	0	0	0	1	0	0	1
- hypertrophy/hyperplasia, follicular [total]
- epithelium	[0]	[1]	[3]	[4]	[0]	[2]	[3]	[4]
- minimal	0	0	0	1	0	2	2	2
- mild	0	1	2	1	0	0	1	2
- moderate	0	0	1	2	0	0	0	0

Dosage Group	I	II	III	IV
Dosage (mg/kg/d)	0	250	500	1000
Body Weight (g)
- Day 1	345.9 ± 8.6	346.4 ± 8.9	346.9 ± 8.4	345.6 ± 6.5
- Day 39	525.6 ± 45.0	489.0 ± 37.9	501.5 ± 31.7	478.8 ± 20.6

Conclusions:

Based on the body weight reductions in male rats, the NOAEL was considered to be 500 mg/kg/day in male rats and 1000 mg/kg/day in female rats. The overall NOAEL is 500 mg/kg-bw/day.

Executive summary:

This study determined the sub-chronic toxicity of the test substance to rats. Groups of rats were exposed by oral gavage to concentrations of 0, 250, 500 or 1000 mg/kg/day of test substance. Males were exposed daily for 39 days, and females were exposed daily through lactation day 4. Animals were observed regularly for body weight, mortality, clinical signs, food consumption, and behaviour. At the end of the study, the animals were sacrificed and examined for gross pathology, organ weights, histopathology, clinical chemistry, hematology, and urinalysis parameters. Adverse effects were seen in the thymus at all dose levels, however, these changes are most likely stress related and are considered to be of minimal toxicological significance. Body weight reduction was seen in male rats at the 1000 mg/kg/day dose level. The LOAEL for male rats is 1000 mg/kg/day, and the NOAEL is 500 mg/kg/day. No adverse effects were seen in female rats. The NOAEL for female rats is 1000 mg/kg/day.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

45 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

Key study is a repeat dose toxicity study, reliable without restriction.

Additional information

The effects of repeated dose oral exposures to HAB was examined and represented by the above two key studies. Results demonstrate NOAELs of 500 mg/kg bw/d (male) and 1000 mg/kg bw/d (female) for one study and NOAELs of 1000 ppm (45 mg/kg bw/d, male and female) for the other. HAB is not considered significantly toxic even after repeated oral exposures.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Key GLP guideline study reports experimental data., conservative value relied upon.

Justification for classification or non-classification

Based on two reliable GLP Key studies, HAB is not considered significantly toxic even after repeated oral exposures.