α,α-dimethylbenzyl hydroperoxide

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1979

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

10 rats were exposed to 4 concentrations of the test substance 5d/wk, over a period of 90 d.

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

α,α-dimethylbenzyl hydroperoxide

EC Number:

201-254-7

EC Name:

α,α-dimethylbenzyl hydroperoxide

Cas Number:

80-15-9

Molecular formula:

C9H12O2

IUPAC Name:

1-methyl-1-phenylethyl hydroperoxide

Details on test material:

- Analytical purity: Lot OC-03-04-7-M15B and OC-03-04-7-Mi5C: 80.20%; Lot OC-06-09-7-MI05: 82.50%

Test animals

Species:

rat

Strain:

other: CDF (Fischer 344 derived)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Wilmington, MA
- Weight at study initiation: males:245-308 g; females: 140-160 g
- Diet (e.g. ad libitum): Purina rat chow ad libitum
- Water (e.g. ad libitum): ad libitum


ENVIRONMENTAL CONDITIONS
- Temperature (°C):
- Humidity (%):
- Air changes (per hr):
- Photoperiod (hrs dark / hrs light):

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: glass and stainless steel in construction, rectangular in cross section, 160 l in volume with regular pyramid top and bottom
- System of generating particulates/aerosols: the cumene hydroperoxide atmosphere was generated by aerosoling the test material with a modified DeVelbies nebulizer; the concentrated aerosol was deluted to the desired concentration with the chamber air at the inlet to the exposure chamber
- Temperature, humidity, pressure in air chamber: the chambers were operated under dynamic air flow conditions (40-50 l/min) with temperature and humidity control
- Method of particle size determination: the median particle diameter and geometric standard deviation were calculated using computer program RCUM. CLIST (Computations Laboratory, Dow Chemical Company)

TEST ATMOSPHERE
- Brief description of analytical method used: the chamber atmosphere was sampled by drawing known volumes of air (10 or 20l) through glass inpingers containing 50 ml n-octanol; cumene hydroperoxide in the n-octanol was assayed colorimetrically by the ferrous thiocynate method for organic peroxide

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Cumene hydroperoxide was assayed colorimetrically in n-propanol containing air samples

Duration of treatment / exposure:

6 hours/day

Frequency of treatment:

5 days/week, for approximately 3 months (males: 60 exposures in 88 days, females: 61 exposures in 89 days); 1 mg/ cubic m group was started with a delay of 15 days resulting in 50 exposure days

Doses / concentrations

Remarks:

Doses / Concentrations:
1, 6, 31, 124 mg/cubic m aerosol
Basis:

No. of animals per sex per dose:

10

Control animals:

yes, concurrent no treatment

Details on study design:

Exposure of 124 mg/cubic m was terminatet after 5 days due to toxicity and all surviving rats of this group were killed and examined on the 12th day of the study.

Positive control:

no data

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes, daily

DETAILED CLINICAL OBSERVATIONS: Yes, daily

BODY WEIGHT: Yes
- Time schedule for examinations: twice per week for the first 2 weeks and once per week thereafter

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No data

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 data

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at or near termination of the study
- How many animals: all animals exposed to 1, 6, 31 mg/square m and controls
- Parameters: red, white and differential blood cell counts, hemoglobin, concentration and packed cell volume

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at or near termination of study
- How many animals: all animals exposed to 1, 6, 31 mg/square m and controls
- Parameters: blood urea nitrogen, serum glutamic pyruvic transaminase, serum alkaline phosphatase

URINALYSIS: Yes
- Time schedule for collection of urine: at or near termination of study
- Metabolism cages used for collection of urine: No data
- Parameters: pH, specific gravity, sugar, protein, ketones, bilirubin, occult blood, urobilinogen

NEUROBEHAVIOURAL EXAMINATION: No data

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table 1)
HISTOPATHOLOGY: Yes (see table 2)

Other examinations:

Frozen sections of adrenal glands and liver were stained with Oil Red G (from 3 males and 3 females from control group and from groups 31 and 124 mg/cubic m) in order to determine lipid content

Statistics:

Hematology, clinical chemistry, urine specific gravity, organ weight and body weight data were evaluated using an analysis of variance and Dunnett's test; the level of significance was for all cases p<0.05

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):

not specified

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

not specified

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
124 mg/cubic m: males and females had difficulty breathing (gasping for air) after the first two days of exposure; subsequent daily exposure through 5 days resulted in progressive deterioration of health indicated by irritation to skin and mucous membranes (gangrene of extremities, exudate around eyes and nose) and breathing difficulties; 6/10 males and 3/10 females died within the first 12 days of the study
1, 6, 31 mg/cubic m: no clinical signs of irritation or toxicity
Mortality see Table 3

BODY WEIGHT AND WEIGHT GAIN
124 mg/square m: significant decrease in body weight
1, 6, 31 mg/square m: no statistically significant effects


HAEMATOLOGY
124 mg/square m: generalized decrease in PCV, RBC count, hemoglobin (it is difficult to assess whether this was a significant treatment related effect, because no control rats were killed simultaneously on day 12th of the study); the WBC count was also decreased (considered highly significant in comparison with historical controls) and coincided with the severe debilated state of surviving rats on day 12 of the study
1, 6, 31 mg/square m: no statistically significant effects


CLINICAL CHEMISTRY
1, 6, 31 mg/square m: no toxicologically significant effects



URINALYSIS
1, 6, 31 mg/square m: no treatment related effects


ORGAN WEIGHTS
1, 6, 31 mg/square m: no treatment related effects

GROSS PATHOLOGY
124 mg/square m: urine and fecal staining in the perineal region; debris around the eyes, external nares or extremities; porphyrin pigment around the nose, eyes, or both; cyanotic or hyperemic appearance of the extremities; dry gangrene of the feet, limbs, or tail; depletion of adipose tissue; variations in color (usually darker, hyperemic or congested) of several internal organs such as liver, kidney, lungs and nasal mucosa; decreased contents in the gastrointestinal tract; edema, ulcerations or erosions of the stomach; thymic athrophy; corneal cloudiness of the eyes
1, 6, 31 mg/cubic m: no treatment related effects


HISTOPATHOLOGY: NON-NEOPLASTIC
124 mg/cubic m: upper respiratory tract changes, including inflammation, erosions or ulcerations of the trachea and nasal turbinates, focal epithelial hyperplasia of tracheal mucosa and squamous metaplasia of the mucosa of the nasal turbinates (males); an apparent decrease in the amount ot secretory material in the pancreatic acini (more prominent in males than in females); changes in nonglandular stomach, including submucosal edema, hyperkeratosis, acanthosis, inflammation, erosions and ulcerations (prominent in males, but not in females); hyperkeratosis of the esophageal mucosa in 2/10 males; depletion of cortical and/or paracortical lymphocytes in the mesenteric lymph nodes; depletion of the germinal centers in the spleen; thymic athrophy with or without necrotic debris and hemorrhage; extremities with necrosis, inflammation, ulcerations, fibrin thrombi in blood vessels, and edema (more common in females than in males); eyes with increased corneal vascularization, corneal ulceration and erosions, and corneal inflammation (more common in males than in females)
1, 6, 31 mg/cubic m: no treatment related effects


OTHER FINDINGS
124 mg/cubic m: decreased lipid content in livers
31 mg/cubic m: no effect on lipid content in livers

Effect levels

Dose descriptor:

NOAEC

Effect level:

31 mg/m³ air

Sex:

male/female

Basis for effect level:

other: absence of recognized treatment related effects on hematology, urinalysis, clinical chemistry, body weights, organ weights and pathology in rats exposed to 1, 6, or 31 mg/cubic m cumene hydroperoxide

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Table 3: Mortality

Exposure group (mg/cubic m)	No. alive at start of the study                     m f	No. dying or killed moribund                    m f	No. terminated after 12 days m                 f	No. presented alive or killed at the end of the study m           f
0	10           10	0              0	0                   0	10              10
1^*	10            10	0               0	0                  0	10               10
6	10             10	0                0	0                  0	10               10
31	10             10	0                0	0                  0	10               10
124**	10             10	6                3	4                  7	0                  0

*: The 1 mg/cubic m exposure group was started 15 days later than the other groups and, therefore, received 10 fewer exposures than the 6, 31 mg/cubic m and control rats

**: The 124 mg/cubic m exposure group received 5 consecutive daily exposures and because of the high toxicity it was terminated on day 12^th of the study

Applicant's summary and conclusion

Conclusions:

The highest no adverse effect concentration in this study was judged to be 31 mg/cubic m which is equivalent to 5 ppm vapor exposure.

Executive summary:

Male and female rats were exposed daily (6 h/day, 5 days/week) to 1, 6, 31 and 124 mg/cubic m cumene hydroperoxide delivered as aerosol over a period of 3 months. Inhalation of 124 mg/cubic m cumene hydroperoxide for 5 consecutive days resulted in decresed body weight and death of 6/10 males and 3/10 females, therefore exposure of this group was terminated after 5 day and all surviving rats were killed on day 12 of the study. Pathologic alterations in rats that died as well as those that survived at 124 mg/cubic m exposure level appeared to be the result of tissue irritation at the site of contact and included ulceration and inflammation of the cornea and eyes, nasal turbinates and lining of the stomach. Primary toxicologic effects following inhalation of124 mg/cubic m cumene hydroperoxide were consistent with those caused by a primary tissue irritant, other changes were judged by the authors as secondary effects and as caused by stress. These included thymic atrophy, depletion of lymphoid tissue in the germinal centers of some lymph nodes and the spleen, decreased lipid content of the liver and decreased circulating white blood cells. The exposure of 1, 6 or 31 mg/cubic m cumene hydroperoxide induced no substance related statistically significant effects on hematology, urinalysis, clinical chemistry, body weights, organ weights and pathology.