(E)-3-methyl-4-(2,6,6-trimethylcyclohex-2-en-1-yl)but-3-en-2-one

Endpoint summary

Description of key information

Repeated dose toxicity, oral (Analogy CAS 127-51-5; OECD 408):
- NOAEL male = 30 mg/kg bw/day, NOAEL female = 500 mg/kg bw/day
- NOEL male = 5 mg/kg bw/day, NOEL female = 30 mg/kg bw/day
- LOAEL male/female = 500 mg/kg bw/day

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:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

A detailed read-across justification in-line with the ECHA RAAF guidelines is provided as an attached document.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Key result

Dose descriptor:

LOAEL

Effect level:

500 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

Dose descriptor:

NOAEL

Effect level:

500 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

female

Basis for effect level:

other: highest dose tested, some effects observed that were considered adaptative in nature and non-adverse.

Dose descriptor:

NOAEL

Effect level:

30 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

histopathology: neoplastic

Remarks on result:

other: effects at 30 mg/kg bw/day in males concluded to be a well documented change that is peculiar to the male rat in response to treatment with some hydrocarbons. As such, only the effects observed at 500 mg/kg bw/day were taken into account by the authors.

Critical effects observed:

not specified

Conclusions:

There are two valid studies on the source substance alpha-isomethyl ionone, but only one (Dunster, 2006) allowed for the derivation of LOAELs and NOAELs.
Based on this data and the possible read-across from alpha-isomethyl ionone to methyl ionone, it was decided to adopt the LOAEL of 500 mg/kg bw/day for both sexes, the NOAEL for female rats of 500 mg/kg bw/day and 30 mg/kg bw/day for males.

A detailed read-across justification in-line with the ECHA RAAF guidelines is provided as an attached document.

Reference 2

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

other: Sprague-Dawley Crl:CD(SD)IGS BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: 6 - 8 w
- Weight at study initiation: male: 131 - 172 g; female: 122 - 155 g
- Housing: in groups of three or four by sex in polypropylene grid-floor cages suspended over trays lined with absorbent paper
- Diet (e.g. ad libitum): free access, pelleted diet (Rodent 5LF2 (Certified) Diet)
- Water (e.g. ad libitum): free access, drinking water was supplied from polycarbonate bottles attached to the cage
- Acclimation period: 6 d


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 +/- 2
- Humidity (%): 55 +/- 15
- Air changes (per hr): > 15x
- Photoperiod (hrs dark / hrs light): 12 / 12

Route of administration:

oral: gavage

Vehicle:

corn oil

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

90 days

Frequency of treatment:

daily

Dose / conc.:

5 mg/kg bw/day (actual dose received)

Dose / conc.:

30 mg/kg bw/day (actual dose received)

Dose / conc.:

500 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes

DETAILED CLINICAL OBSERVATIONS: Yes

BODY WEIGHT: Yes

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes

OPHTHALMOSCOPIC EXAMINATION: Yes
- Dose groups that were examined: control and high dose (500 mg/kg bw) group

HAEMATOLOGY: Yes
- Time schedule for collection of blood: end of study

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: end of study

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations:prior to start of study, then weekly
- Battery of functions tested: sensory activity during week 12

OTHER:
- All animals were examined for overt signs of toxicity, ill-health or behavioural changes immediately before dosing and one and five hours after dosing during the working week.
- Animals were observed immedately before dosing and one hour after dosing at weekends. Prior to the start of treatment and at weekly intervals thereafter, all animals were observed for signs of functional/behavioural toxicity.
-Functional performance tests were also performed on all animals during week 12, together with an assessment of sensory reactivity to different stimuli.
- Clinical signs, functional observations, bodyweight development and food and water consumption were monitored during the study.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes, of selected tissues

Statistics:

Statistical analyses were performed.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Description (incidence and severity):

No adverse effect on bodyweight development was detected.

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

no effects observed

Ophthalmological findings:

no effects observed

Description (incidence and severity):

No treatment related changes

Behaviour (functional findings):

not examined

Description (incidence and severity):

No toxicologically significant effects in organ weights were detected

Gross pathological findings:

no effects observed

Neuropathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Key result

Dose descriptor:

LOAEL

Effect level:

500 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

Dose descriptor:

NOAEL

Effect level:

500 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

female

Basis for effect level:

other: highest dose tested, some effects observed that were considered adaptative in nature and non-adverse.

Dose descriptor:

NOAEL

Effect level:

30 mg/kg bw/day (nominal)

Based on:

other: effects at 30 mg/kg bw/day in males concluded to be a well documented change that is peculiar to the male rat in response to treatment with some hydrocarbons.

Sex:

male

Basis for effect level:

histopathology: non-neoplastic

Remarks on result:

other: effects at 30 mg/kg bw/day in males concluded to be a well documented change that is peculiar to the male rat in response to treatment with some hydrocarbons. As such, only the effects observed at 500 mg/kg bw/day were taken into account by the authors.

Critical effects observed:

not specified

The oral administration of the test material to rats for a period of ninety consecutive days at dose levels of 5, 30 and 500 mg/kg/day resulted in treatment related effects in males at 500 and 30 mg/kg/day and in females at 500 mg/kg/day. The No Observed Effect Level (NOEL) was considered to be 30 mg/kg/day for females and 5 mg/kg/day for males.

5 mg/kg	no effects, reported No Effect Concentration
	- There were no deaths. - No clinically observable signs of toxicity were detected in test or control animals throughout the study period. - There were no treatment-related changes in the behavioural parameters measured. - There were no treatment-related changes in the functional performance parameters measured. - There were no treatment-related changes in sensory reactivity. - No adverse effect on bodyweight development was detected. - No adverse effect on dietary intake or food efficiency was detected. No intergroup differences in water consumption were detected. - No treatment-related ocular effects were observed. - No treatment-related haematology changes were detected. - No treatment-related blood chemistry effects were detected. - No toxicologically significant effects in organ weights were detected. - At necropsy, no macroscopic abnormalities were detected. The no observed effect concentration of the test material in corn oil for males was 5 mg/kg/day.
30 mg/kg	no observed adverse effect level, no effects, reported No Effect Concentration
	- There were no deaths. - No clinically observable signs of toxicity were detected in test or control animals throughout the study period. - There were no treatment-related changes in the behavioural parameters measured. - There were no treatment-related changes in the functional performance parameters measured. - There were no treatment-related changes in sensory reactivity. - No adverse effect on bodyweight development was detected. - No adverse effect on dietary intake or food efficiency was detected. - No intergroup differences in water consumption were detected. - No treatment-related ocular effects were observed. - No treatment-related haematology changes were detected. - No treatment-related blood chemistry effects were detected. - No toxicologically significant effects in organ weights were detected. - At necropsy, no macroscopic abnormalities were detected. The following treatment-related changes were detected: - A greater incidence of higher severity grades of globular accumulations of eosinophilic material were observed in the tubular epithelium of 5/10 (minimal effects) and 4/10 (slight effects) males treated at this dose level (p0.05). Authors stated that this finding is consistent with the presence of hydrocarbon nephropathy, which results from the excessive accumulation of alpha-2-microglobulin in renal proximal tubular epithelial cells. Alpha-2-microglobulin is found only in the proximal tubular epithelium of adult male rats. - One male rat treated at this dose level exhibited associated higher grades of tubular basophilia. The no observed effect concentration of the test material in corn oil for females was 30 mg/kg/day. Authors stated that the kidney changes identified histopathologically were consistent with well documented changes that are peculiar to the male rat in response to treatment with some hydrocarbons. This effect may not be indicative of a hazard to human health and for the purposes of hazard evaluation the no observed adverse effect level for males should be regarded as 30 mg/kg/day.
500 mg/kg	bone marrow effects, liver
	- There were no deaths. - No clinically observable signs of toxicity were detected in test or control animals throughout the study period. - There were no treatment-related changes in the behavioural parameters measured. - There were no treatment-related changes in the functional performance parameters measured. - There were no treatment-related changes in sensory reactivity. - No adverse effect on bodyweight development was detected. - No adverse effect on dietary intake or food efficiency was detected. - No intergroup differences in water consumption were detected. No treatment-related ocular effects were observed. - No treatment-related haematology changes were detected. - No treatment-related blood chemistry effects were detected. - No toxicologically significant effects in organ weights were detected. - At necropsy, no macroscopic abnormalities were detected. The following treatment-related changes were detected: - Hepatocyte enlargement, centrilobular or generalised, was observed in relation to treatment for 4/10 (minimal effects) males and 9/10 (minimal effects) females treated at this dose level (p0.05 for males; p0.001 for females). Authors stated that hepatocyte enlargement is commonly observed in the rodent liver following the administration of xenobiotics and in the absence of associated degenerative changes may be interpreted as adaptive in nature. - A greater incidence of higher severity grades of globular accumulations of eosinophilic material were observed in the tubular epithelium of 3/10 (minimal effects), 5/10 (slight effects) and 1/10 (moderate effects) males treated at this dose level (p0.01). Authors stated that this finding is consistent with the presence of hydrocarbon nephropathy, which results from the excessive accumulation of alpha-2-microglobulin in renal proximal tubular epithelial cells. Alpha-2-microglobulin is found only in the proximal tubular epithelium of adult male rats. - Two male rats treated at this dose level exhibited associated higher grades of tubular basophilia. - In the thyroid, a higher incidence of follicular cell hypertrophy was seen in relation to treatment for 7/10 (minimal effects) males at this dose level (p0.01). - A higher incidence of lower grades of severity of adipose infiltration of the bone marrow, indicative of marrow hyperplasia, was observed in relation to treatment for 7/10 (minimal effects) and 3/10 (slight) males treated at this dose level (p0.01).

Conclusions:

In this oral subchronic study in rats performed with the test item alpha-methylionone at doses 5, 30 and 500 mg/kg bw/day, the NOAELoral was found to be 30mg/kg bw/d for males and 500mg/kg bw/day for females.

Executive summary:

A study was conducted to investigate the systemic toxicity of the test material. The test material was administered by gavage to three groups, each of ten male and ten female Sprague-Dawley Crl:CD(SD)IGS BR strain rats for 90 consecutive days. A control group of ten males and ten females was dosed with the vehicle alone (corn oil). The animals were acclimatised for 6 days. At the start of treatement the males weighed 131 to 172 grams and the females weighed 122 to 155 grams. The animals were approximately 6-8 weeks old. Animals were housed in groups of three or four by sex in polypropylene grid-floor cages suspended over trays lined with absorbent paper. The animals were allowed free access to food and water. A pelleted diet (Rodent 5LF2 (Certified) Diet) was used. Mains drinking water was supplied from polycarbonate bottles attached to the cage. The animals were housed in a single air-conditioned room with an air exchange rate of at least 15 air changes per hour and the low intensity lighting was controlled to give twelve hours continuous light and twelve hours darkness. The temperature and relative humidity were set to achieve target values of 21 +/- 2 C and 55 +/- 15%, respectively. Dose levels were 5, 30 and 500 mg/kg/day at a volume of 4 ml/kg. All animals were examined for overt signs of toxicity, ill-health or behavioural changes immediately before dosing and one and five hours after dosing during the working week. Animals were observed immedately before dosing and one hour after dosing at weekends. Prior to the start of treatment and at weekly intervals thereafter, all animals were observed for signs of functional/behavioural toxicity. Functional performance tests were also performed on all animals during Week 12, together with an assessment of sensory reactivity to different stimuli. Clinical signs, functional observations, bodyweight development and food and water consumption were monitored during the study. Haematology and blood chemistry were evaluated for all animals at the end of the study. Ophthalmosscopic examination was also performed on control and high dose animals (500 mg/kg). All animals were subjected to gross necropsy examination and histopathological evaluation of selected tissues was performed Statistical analyses were performed.

There were no unscheduled death and no clinical sings of toxicity observed. No adverse effects on bodyweight, dietary intake or food efficiency and treatment-related haematology changes were detected. A statistically significant increase in liver and kidney weights both absolute and relative was observed in animals treated with 500 mg/kg/day and a significant increase in plasma creatinine, total protein and cholesterol were also observed in high-dose animals. Histopathology revealed an enlargement of hepatocytes in the liver (generally regarded as adaptive in nature) of animals treated with 500 mg/kg/day. Males treated with 500 mg/kg/day also showed a significant increase in spleen weight and in plasma albumin. No abnormalities were observed at necropsy. A greater incidence of globular accumulations of eosinophilic material in the kidney’s tubular epithelium was noted in males treated with 30 and 500 mg/kg/day and a higher incidence of follicular cell hypertrophy in thyroid and adipose infiltration of the bone marrow (indicative of morrow hyperplasia) in males treated with 500 mg/kg/day. The NOEL was considered to be 30 mg/kg/day for females and 5 mg/kg/day for males. Because the kidney changes noted in male rats were consistent with well documented changes that are peculiar to the male rat in response to treatment with some hydrocarbons, the NOAEL for males may be considered to be 30 mg/kg/day.

Reference 3

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

limited documentation and dose levels choice was not according to guideline.

Qualifier:

equivalent or similar to guideline

Guideline:

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

GLP compliance:

not specified

Limit test:

no

Specific details on test material used for the study:

Obtained from one or more known primary producers of each substance in the USA and of typical commercial grade.

Species:

rat

Strain:

other: FDRL rats

Sex:

male/female

Details on test animals or test system and environmental conditions:

The groups consisted of 15 male and 15 female rats of the FDRL strain, housed individually in wiremesh cages and fed their respective diets (Purina Laboratory Chow) and fresh ater ad libitum.

Route of administration:

oral: feed

Details on route of administration:

Test substance diluted in cotton seed oil in a concentration sufficient to provide the predetermined dosage in 2% of the diet.

Vehicle:

cotton seed oil

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

90 days

Frequency of treatment:

Daily

Dose / conc.:

3.66 mg/kg bw/day (nominal)

Remarks:

Dose selected so as to be at least 100 times the maximum estimated human dietary level.

Dose / conc.:

3.55 mg/kg bw/day (actual dose received)

Remarks:

in males

Dose / conc.:

4.1 mg/kg bw/day (actual dose received)

Remarks:

in females

No. of animals per sex per dose:

15 rats per sex per dose

Control animals:

yes, concurrent no treatment

Details on study design:

A 90 day study with 15 FDRL rats (per sex per dose), weighing 82.1 +/- 2.3 grams for males and 77.1 +/- 2.3 grams for females were used. There was one control group for every 3 test groups. Each test substance was diluted in cotton-seed oil in a concentration sufficient to provide the predetermined dosage in 2% of the diet. Dosages were administered on a uniform body weight basis by biweekly adjustments of the concentration of the test material in the cotton-seed oil. Observations included body weight and food consumption. In addition, haematological and blood chemical determinations were made on 8 rats of each sex at a 6 week period and in all rats at 12 weeks. The tests were terminated at 90 days. All animals were sacrificed and a gross necropsy was carried out. At necropsy, liver and kidney weights were recorded and the following organs from half the animals in each group were taken for histological examination: liver, kidneys, stomach, small andlarge intestines, spleen, pancrease, heart, lungs, bone marrow, muscle, brain, spin cord, bladder, adrenals, thyroid, pituitary, gonads, salivary glands, and lymph nodes.

Observations and examinations performed and frequency:

Observations included the usual observations (ie body weight and food consumption). In addition, haematological and blood chemical determinations were made on 8 rats of each sex at a 6 week period and in all rats at 12 weeks.

Sacrifice and pathology:

The tests were terminated at 90 days. All animals were sacrificed and a gross necropsy was carried out. At necropsy, liver and kidney weights were recorded and the following organs from half the animals in each group were taken for histological examination: liver, kidneys, stomach, small andlarge intestines, spleen, pancrease, heart, lungs, bone marrow, muscle, brain, spin cord, bladder, adrenals, thyroid, pituitary, gonads, salivary glands, and lymph nodes.

Statistics:

Performed but not specified.

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 specified

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

In males: slightly reduced haemoglobin level, but the haematocrit adn erythrocyte counts were within control ranges.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

In males: mean blood urea nitrogen level (8.9 mg/100ml) somewhat below that of the composite controls. However, in that particular series, the male control rats showed a mean blood urea nitrogen at 12 weeks of 9.2 mg/100ml; the value at 6 weeks was 10.8 mg/100ml for the test item group compared with 9.9 mg/100ml for the controls.

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Immunological findings:

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Neuropathological findings:

not specified

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Other effects:

no effects observed

Key result

Dose descriptor:

NOAEL

Effect level:

>= 3.55 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: highest dose tested with no adverse effects observed

Key result

Dose descriptor:

NOAEL

Effect level:

>= 4.1 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

female

Basis for effect level:

other: highest dose tested with no adverse effects observed

Critical effects observed:

no

Conclusions:

In this oral subchronic study in rats performed with the test item alpha-methylionone at 3.66 mg/kg bw/day (actually found 3.55 mg/kg bw/d for males and 4.10 mg/kg bw/d for females), the NOAELoral was found to be ≥ 3.55 mg/kg bw/d for males and ≥ 4.10 mg/kg bw/d for females.

Executive summary:

In the second supporting study (Oser, 1965), another 90 day study used 15 FDRL rats (per sex per dose), weighing 82.1 +/- 2.3 grams for males and 77.1 +/- 2.3 grams for females. There was one control group for every 3 test groups, as several test substances were examined in this campaign. Each test substance was diluted in cotton-seed oil in a concentration sufficient to provide the predetermined dosage in 2% of the diet. Dosages were administered on a uniform body weight basis by biweekly adjustments of the concentration of the test material in the cotton-seed oil. Observations included body weight and food consumption. In addition, haematological and blood chemical determinations were made on 8 rats of each sex at a 6 week period and in all rats at 12 weeks. The tests were terminated at 90 days. All animals were sacrificed and a gross necropsy was carried out. At necropsy, liver and kidney weights were recorded and the following organs from half the animals in each group were taken for histological examination: liver, kidneys, stomach, small and large intestines, spleen, pancreas, heart, lungs, bone marrow, muscle, brain, spin cord, bladder, adrenals, thyroid, pituitary, gonads, salivary glands, and lymph nodes. Haemoglobin and blood urea nitrogen were slightly decreased in the males, but those findings were within control ranges or only slightly out of range, and were not considered adverse.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

30 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

Data are derived from the structural methyl ionone analog alpha-iso-methylionone, for more information please refer to the read-across justification.

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: inhalation

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Reason / purpose for cross-reference:

data waiving: supporting information

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: dermal

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

a short-term toxicity study does not need to be conducted because a reliable sub-chronic (90 days) or chronic toxicity study is available, conducted with an appropriate species, dosage, solvent and route of administration

Reason / purpose for cross-reference:

data waiving: supporting information

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: dermal

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

a short-term toxicity study does not need to be conducted because a reliable sub-chronic (90 days) or chronic toxicity study is available, conducted with an appropriate species, dosage, solvent and route of administration

Reason / purpose for cross-reference:

data waiving: supporting information

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

In order to assess the endpoint of repeated dose toxicity, data from the four principal components α-iso-methylionone, methyl-α-ionone, methyl-β-ionone, and isomethyl-β-ionone of methyl ionone were used as well as data from related ionones. For more information, please refer to the attached read-across justification.

Oral

Due to the lack of sufficient data regarding oral repeated dose toxicity, data for the analogue substance alpha-iso-methylionone (CAS No.127-51-5) were taken into account. For this substance two 90-day oral subchronic studies under GLP were performed according to OECD Guideline 408 (Dunster, 2006 and Politano 2012). Ten male and ten female Sprague-Dawley rats (Crl:CD(SD)IGS BR) were daily administered by gavage with 5, 30, 500 mg/kg bw/d at a volume of 4 ml/kg bw in olive oil. While no toxic effects were noted at 5 mg/kg bw/d, a greater incidence of higher severity grades of globular accumulations of eosinophilic material were observed in the tubular epithelium of nine out of ten males at 30 mg/kg bw/day. Administration of 500 mg/kg bw/d led to centrilobular or generalised hepatocyte enlargement in four out of ten males and nine out of ten females. Also, greater incidences of higher severity grades of globular accumulations of eosinophilic material were observed in the tubular epithelium in nine out of ten males. Two male rats treated at this dose level exhibited associated higher grades of tubular basophilia, whereas a higher incidence of follicular cell hypertrophy in the thyroid was seen in relation to treatment for seven out of ten males. In addition, a higher incidence of lower grades of severity of adipose infiltration of the bone marrow, indicative of marrow hyperplasia, was observed in relation to treatment for all males treated at this dose level.

The authors stated that the kidney changes identified histopathologically were consistent with well documented changes that are peculiar to the male rat in response to treatment with some hydrocarbons. This effect may not be indicative of a hazard to human health and for the purposes of hazard evaluation the no observed adverse effect level for males should be regarded as 30 mg/kg/day. Besides this, hepatocyte enlargement is commonly observed in the rodent liver following the administration of xenobiotics and in the absence of associated degenerative changes may be interpreted as adaptive in nature. Therefore, the no effect level (NOEL) was estimated as 5 and 30 mg/kg bw/d for males and females, respectively. NOAELs were observed to be 30 mg/kg bw/d for males and females. Due to the structural similarities, the same result could also be expected for methylionone.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
OECD guideline study according to GLP, detailed report published.

Justification for classification or non-classification

The present data on repeated dose toxicity do not fulfill the criteria laid down in 67/548/EEC and 1272/2008/EEC, and therefore, a non-classification is warranted.