4-hydroxy-4-methylpentan-2-one

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1980

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1980

Report date:

1980

Reference 2

Reference Type:

study report

Title:

Unnamed

Year:

1979

Report date:

1979

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 412 (Subacute Inhalation Toxicity: 28-Day Study)

Deviations:

no

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

4-hydroxy-4-methylpentan-2-one

EC Number:

204-626-7

EC Name:

4-hydroxy-4-methylpentan-2-one

Cas Number:

123-42-2

Molecular formula:

C6H12O2

IUPAC Name:

4-hydroxy-4-methylpentan-2-one

Details on test material:

- Supplier: Shell Nederland Chemie
- Name of test material (as cited in study report): Diacetone alchol
- Physical state: liquid
- Analytical purity: 99.44%

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Shell Toxicology Laboratory (Tunstall)
- Age at study initiation: 10 to 13 weeks
- Weight at study initiation: 413 to 415 g (male) and 245 to 246 g (female)
- Housing: hanging aluminum cages with stainless steel bases
- Diet: Lad 1 (Spillers Spratts Ltd.), ad libitum
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 to 25
- Humidity (%): 31 to 57
- Photoperiod (hrs dark / hrs light):12/12

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

clean air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: aluminum chamber with a volume of 1 m3
- Source and rate of air: laboratory air and 1.8 and 1.9 m3/min
- System of generating particulates/aerosols: by completely evaporating the solvent into the streams of ventilating air entering the chambers using micrometering pumps and vaporisers
- Temperature, humidity, pressure in air chamber: between 19 and 25 °C, humidity and pressure not reported
- Air flow rate: 0.40 to 0.55 meters cubed/min
- Treatment of exhaust air: exhaust ducts from each chamber entered a common exhaust duct through which the air was drawn by a fan situated on the roof of the laboratory.

TEST ATMOSPHERE
- Brief description of analytical method used: hydrocarbon analysers fitted with flame-ionisation detectors

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

hydrocarbon analysers fitted with flame-ionisation detectors.

Duration of treatment / exposure:

6 weeks

Frequency of treatment:

6 hours/day, 5 days/week

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
50, 225 and 1000 ppm
Basis:
nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
233, 1041 and 4685 mg/m3
Basis:
analytical conc.

No. of animals per sex per dose:

12 animals/sex/dose

Control animals:

yes, sham-exposed

Details on study design:

- Dose selection rationale: no data
- Rationale for animal assignment (if not random): no data

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS:Yes
-Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: at the end of the experiment

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
- Time schedule for examinations: weekly

FOOD EFFICIENCY:
- 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

WATER CONSUMPTION: Yes

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at the end of the experiment
- Anaesthetic used for blood collection: No data
- Animals fasted: No data

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the end of the experiment
- Animals fasted: No data

URINALYSIS: Yes
- Time schedule for collection of urine: overnight following the last exposure
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes

ORGAN WEIGHT: Yes
After post-mortem examinations the following organe were weighed:
Brain Liver
Heart Spleen
Kidneys Testes

HISTOPATHOLOGY: Yes
Tissues taken for histological examination were: *
Mammary gland (posterior site with skin)
Mesenteric lymph node
Pancreas
Stomach
Intestine at 5 levels
Caecum*
Spleen
Liver (middle, left and trianguler lobes)
Adrenals
Kidneys
Ovaries or testes
Uterus or prostate
Seminal vesicles*
Urinary bladder
Thyroid with oesophagus and trachea
Trachea (mid course and bifurcation)
Heart
Lungs
Nasal cavity
Thymus
Eye and lacrimal glands
Salivary gland (submaxillary)
Brain
Spinal cord (thoracic)*
Pituitary
Tongue*
Sciatic nerves*
Muscle (femoral)*
Knee joint and femur*
Plus any other macroscopic lesions in any tissues

The samples marked * were held in 4% neutral formalin and only processed for histological examination if indicated by clinical or other pathological findings.

Statistics:

Body and organ weights were analysed by covariance analysis using initial body weight as the covariate. Reported means were adjusted for initial body weight if a significant covariance relationship existed: where no significant covariance relationship was found, unadjusted means were reported.Organ weights were further examined by covariance analysis using the terminal body weight as the covariate. The organ weight means are reported as adjusted for terminal body weight if a significant covariance relationship existed. Although not a true covariance analysis (because the terminal body weights are dependent upon treatment), the analysis does provide an aid to the interpretation of organ weights when there are differences in terminal body weights. The analysis attempts to predict what the organ weights would have been, had all the animals had the same terminal body weight. Clinical chemical and haemlatological parameters were examined using analysis of variance. The analysis allowed for the fact that animals were multi-housed.Differences in response can be affected by cage environment as well as by treatment (this is indicated by 'C' - inflated standard deviation due to significant cage effect), but this effect is minimal in a study of this duration. The significance of any difference between treated and control group means was tested using the Williams t –test (1971, 1972). However, if a monotonic dose response could not be assumed Dunnett's test (1964) was used.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

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):

no effects observed

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

effects observed, treatment-related

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY: No clinical signs of toxicity were noted during the first four weeks of exposure, but over the next two weeks slight lethargy was noted in several of the animals exposed to the high and medium concentrations when they were examined 30 minutes after cessation of exposure. These signs persisted for a few hours but all the rats were fully recovered before the next day's exposure.

BODY WEIGHT AND WEIGHT GAIN: The body weights of females exposed to the high concentration to be significantly lower (-5%) than controls at week 6. No significant differences were noted in any other group.

FOOD CONSUMPTION: The results show no significant differences in the female food intakes but a significant reduction from control in the males exposed to the high concentration (-14%) after 2 weeks, but not at subsequent weeks.

HAEMATOLOGY: The results of the haematological analysis of the blood taken from each rat 18 hours after the last exposure to DAA show no significant differences in the males. Haemoglobin was significantly higher (+6%) than control at the high concentration exposure level in females.
Differential leucocytes count of blood taken 18 hours after the last exposure to the high concentration did not show any significant differences from control.

CLINICAL CHEMISTRY: In females only one significant difference was seen, LDH being significantly higher (+48%) than control at the high concentration. In males plasma protein was increased (+3%) at the high concentration, plasma chloride was reduced (-1%) at the medium and high concentration, and plasma sodium was reduced (-0.7%) at the low, medium and high concentrations.

URINALYSIS: The results show blood to be present in the urines of two rats but this could be attributed to slight damage to the claws from the mesh floor of the urine collector. Glucose was also present in the urine of many of the rats , but since the urine was collected overnight between exposures and the animals had to be fed during the collection period, the presence of glucose is not unexpected. What was unexpected was the very low incidence of rats with glycosuria at the high dose compared with controls and low dose rats .

ORGAN WEIGHTS: The organ weights of the rats showed male liver weights to be significantly higher than control at the medium (+13%) and high (+23%) concentrations, and male kidney weights to be significantly higher ( +17%) than control at the high concentration. When adjustment was made for terminal body weight, not only was there a significant increase in the males in these variates but the females also were significantly higher than controls .

HISTOPATHOLOGY: With the exception of one animal, the kidneys of all males exposed to the high concentration showed eosinophilic hyaline droplets in the proximal tubular cells. They were not easily identified without the use of the X100 objective. The cells containing the droplets were of limited distribution, being mainly close to the surface around the superficial glomeruli. These eosinophilic hyaline droplets were not seen in the females exposed to the high concentration or in the males and females exposed to the medium and low concentrations. In other organs, abnormalities included alveolar wall thickening and minor inflammatory infiltrates in the lungs, and similar infiltrates in the nasal cavities and trachea. Inflammatory changes in the lacrimal and salivary glands were found in a minority of animals. None of these changes appeared to be compound related.

Effect levels

1

Key result

Dose descriptor:

NOAEC

Remarks:

systemic toxicity

Effect level:

4 685 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: increased kidney and liver weights in males and eosinophilic hyaline droplets in the proximal tubular cells in males

2

Key result

Dose descriptor:

NOEC

Remarks:

systemic toxicity

Effect level:

1 041 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no effect

3

Key result

Dose descriptor:

NOAEC

Remarks:

local irritation of the respiratory tract

Effect level:

>= 4 685 mg/m³ air (analytical)

Sex:

male/female

Basis for effect level:

other: no effect

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Executive summary:

A 6-week whole body inhalation study was conducted with 4-hydroxy-4-methylpentan-2-one in Wistar rats. Animals were exposed to analytical concentrations of 0, 233, 1041 and 4685 mg/m³of 4-hydroxy-4-methylpentan-2-one for 6 hours per day for 5 days per week for 6 weeks (Butterworth et al., 1980). This non-GLP study was equivalent to OECD Test Guideline 412. There were no clinical signs of toxicity in the first four weeks of exposure; however, slight lethargy was noted for a few hours in 233 and 4685 mg/m³4-hydroxy-4-methylpentan-2-one-exposed animals over the following 2 weeks. The body weights of females exposed to 4685 mg/m³were significantly lower (-5%) than controls at week 6. After 2 weeks, food consumption was significantly decreased in males compared to controls; however, this was not noted in subsequent weeks. Haemoglobin was significantly increased (+6%) in females exposed to 4685 mg/m³4-hydroxy-4-methylpentan-2-one compared to controls. Lactate dehydrogenase (LDH) was significantly higher (+48%) in females exposed to 4685 mg/m³4-hydroxy-4-methylpentan-2-one compared to controls. In males, plasma protein was increased (+3%) at the 4685 mg/m³concentration and plasma sodium was reduced (-0.7%) at all concentrations. Liver and kidney weights were increased in males (compared to controls) exposed to 1041 (liver+13%) and 4685 mg/m³(liver+23%) and 4685 mg/m³(kidney +17%) 4-hydroxy-4-methylpentan-2-one, respectively. Histologically, the abnormal presence of eosinophilic hyaline droplets in the proximal tubules of males exposed to the high concentration was noted. There was no suggestion of cellular damage and the response may have been due to cellular accumulation of the chemical or a metabolite. A review of the study data suggests that a NOAEC of 4685 mg/m³and a NOEC of 1041 mg/m³can be considered for repeated-dose inhalational toxicity, based on liver weight changes not associated with histological alterations and probably secondary to a metabolic over load and based on the male rat-specific eosinophilic hyaline droplets in the proximal tubular cells as hyaline droplet formation in male rats is not considered to be relevant to human health for the purposes of risk assessment (U. S. EPA, 1991). No irritation of the respiratory tract was observed up to the highest concentration tested.