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Toxicological information

Repeated dose toxicity: inhalation

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Administrative data

Endpoint:
sub-chronic toxicity: inhalation
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
14 weeks in 2005
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Recent study conducted by NTP similarly to OECD guideline 413 with deviations: food consumption, hematology, ophthalmological examination, some organ weights were not recorded.
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
other: data available on NTP website
Title:
Unnamed
Year:
2006

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
Deviations:
yes
Remarks:
food consumption, hematology, ophthalmological examination, some organ weights were not recorded
Principles of method if other than guideline:
Not applicable
GLP compliance:
not specified
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Purity ≥ 97%

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
After a 10- to 14-day quarantine period, animals are assigned at random to treatment groups.

Administration / exposure

Route of administration:
inhalation
Type of inhalation exposure:
not specified
Vehicle:
not specified
Remarks on MMAD:
MMAD / GSD: no data
Details on inhalation exposure:
No data
Analytical verification of doses or concentrations:
not specified
Details on analytical verification of doses or concentrations:
No data
Duration of treatment / exposure:
14 weeks; 6 hours per day
Frequency of treatment:
five times per week, weekdays only
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
25 ppm
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
50 ppm
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
100 ppm
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
200 ppm
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
400 ppm
Basis:
nominal conc.
No. of animals per sex per dose:
10
Control animals:
yes
Details on study design:
No
Positive control:
No

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes for moribundity and death
- Time schedule: twice daily, at least 6 hours apart (before 10:00 AM and after 2:00 PM)

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: on Day 1 of the test, after 7 days and at weekly intervals thereafter

FOOD CONSUMPTION: No

FOOD EFFICIENCY: No

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: No

CLINICAL CHEMISTRY: Yes

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
Other examinations:
no data
Statistics:
Kaplan-Meier used for probability of survival. Statistical analyses used for possible dose-related effect on survival was Cox (Cox D.R. (1972) Regression models and life tables. J.R. Stat. Soc. B34: 187-220.) for testing two groups for equality; and Tarone’s (Tarone R.E. (1975) Tests for trend in life table analysis. Biometrika 62; 679-682) life table test for a dose-related trend.

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 examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
not specified
Details on results:
MORTALITY
In the high dose group (400 ppm), 6 females were found dead before the end of the study (4 on Day 36, 1 on Day 50 and 1 on Day 91). All other animals survived until terminal sacrifice.

CLINICAL EXAMINATION
Three females of the high dose group (which survived until terminal sacrifice) displayed mild tremors.

BODY WEIGHT AND WEIGHT GAIN
Males: during the first week of treatment, the body weight gain was slightly lower in all treated groups when compared to the control group. The overall bodyweight gain was significantly lower in the high dose group (197 g vs 224 g in the control group).
Females: during the first week of treatment, the body weight gain was lower in the high dose group only when compared to the treated group. Thereafter the mean bodyweight gain of females in the high dose group was variable but overall approximately half this of the control group. All surviving females at 400 ppm lost weight between week 12 and week 14.

CLINICAL CHEMISTRY
Males showed statistically significant reductions in sorbitol dehydrogenase activity at 400 ppm, alanine aminotransferase activity at levels ≥50 ppm, and alkaline phosphatase activity at levels ≥100 ppm. Females showed statistically significant reductions in alanine aminotransferase activity at levels ≥200 ppm, and alkaline phosphatase activity at the 400 ppm. There were significant decreases at lower levels of exposure for females but these changes were not dose-dependent. None of these changes in enzyme activity were related to organ weight changes or evidence of histopathology.

ORGAN WEIGHTS
Absolute and relative liver weights were statistically increased in males at 200 ppm and greater and relative and absolute kidney weights were increased in males at 100 ppm and greater. In females, relative and absolute liver weights were increased at levels of ≥50 ppm, but there were no increases in either hepatic enzymes or any evidence of histopathological changes at any of these dose levels.
Females showed statistically significant decreases in absolute and relative thymus weights and increased relative lung weight at the 400 ppm level.

HISTOPATHOLOGY: NON-NEOPLASTIC
Examination of the male kidneys at all dose levels revealed lesions including granular casts and hyaline droplets indicative of α2u-globulin nephropathy.
In females there was no evidence of histopathology in any organ at any dose level. Specifically, there was no evidence of histopathological changes to the clitoris, ovaries, uterus, epididymis, preputial gland, seminal vesicles, and testes for any of the control or test groups of animals.

Effect levels

open allclose all
Dose descriptor:
LOAEL
Effect level:
25 ppm
Based on:
test mat.
Sex:
male
Basis for effect level:
other: Nephropathy which is relevant only in male rats. Lower body weight gain in the high dose group. In humans, this LOAEL will not be relevant.
Dose descriptor:
NOAEL
Effect level:
200 ppm
Based on:
test mat.
Sex:
female
Basis for effect level:
other: Based on mortality and lower body weight gain in the high dose group.

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

Table 1 - Mean body weight gain (g) in males

Dose Group Wk 1-2 Wk 1-14
Vehicle Control 55.6 224
25 ppm 45.7 212
50 ppm 49.2 221
100 ppm 36.6 207
200 ppm 46.0 216
400 ppm 33.2 197

Table 2 - Mean body weight gain (g) in females

Dose Group Wk 1-2 Wk 1-14
Vehicle Control 26.4 99
25 ppm 25.1 101
50 ppm 27.5 109
100 ppm 19.0 99
200 ppm 22.7 105
400 ppm 16.2 57

Applicant's summary and conclusion

Conclusions:
The LOAEL in male rats is the lowest dose level tested, but it is not relevant to humans as it is based on renal effects linked to alpha2µ-globulin accumulation. When considering effects other than those on kidneys in males, a lower body weight gain was observed at 400 ppm when compared to controls.
A NOAEL could be defined in female rats at 200 ppm on the basis of mortality and a lower body weight gain at the next dose level when compared to controls.
The overall NOAEL relevant for humans is 200 ppm, equivalent to ca. 170 mg/kg bw/day.
Executive summary:

In a 90-day inhalation study conducted by NTP similarly to OECD guideline 413, groups of 10 animals per dose and per sex were administered for 6 hours per day, 5 weekdays per week at 0, 25, 50, 100, 200 and 400 ppm for a total of 14 weeks. The animals were observed twice per day and weighed once per week. A complete histopathologic evaluation including treatment-related gross lesions was performed on all animals, including early death animals. Treatment-related lesions (target organs) were identified and these organs and gross lesions were examined to a no-effect level.

Apart from lesions including granular casts and hyaline droplets indicative of alpha2µ-globulin nephropathy observed in all treated group males, a lower body weight gain than in controls was observed in the high dose group in both sexes. In addition, 6 females died and 3 females displayed mild tremors in the high dose group too.

The LOAEL in male rats is the lowest dose level tested, but it is not relevant to humans as it is based on renal effects linked to alpha2µ-globulin accumulation. When considering effects other than those on kidneys in males, a lower body weight gain was observed at 400 ppm when compared to controls. A NOAEL could be defined in female rats at 200 ppm on the basis of mortality and a lower body weight gain at the next dose level when compared to controls. The overall NOAEL relevant for humans is 200 ppm.