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Acute Toxicity: inhalation

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Administrative data

Endpoint:
acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1987-08-28 to 1987-09-29
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study with acceptable restrictions: no air control animals; exposure concentrations spaced suboptimal

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1988
Report date:
1988

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 403 (Acute Inhalation Toxicity)
Version / remarks:
adopted May 12, 1981
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPP 81-3 (Acute inhalation toxicity)
Version / remarks:
November 1982, revised edition, November 1984
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: U.K. B4 (Inhalation Toxicity of Pesticidal Chemicals), revised edition 1981
Deviations:
no
Principles of method if other than guideline:
other: Sachsse et al. (1973, 1976) and Cannon et al. (1983)
GLP compliance:
yes
Test type:
standard acute method
Limit test:
no

Test material

Constituent 1
Reference substance name:
Reaction mass of 2,2,4-trimethylhexa-1,6-diyl diisocyanate and 2,4,4-trimethylhexa-1,6-diyl diisocyanate
EC Number:
915-277-1
Cas Number:
32052-51-0
Molecular formula:
C11H18N2O2
IUPAC Name:
Reaction mass of 2,2,4-trimethylhexa-1,6-diyl diisocyanate and 2,4,4-trimethylhexa-1,6-diyl diisocyanate
Test material form:
other: liquid
Details on test material:
> 99 %: 2,2,4(or 2,4,4)-Trimethylhexane-1,6-diisocyanate

Test animals

Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ORGANISMS: 
- Strain:  Wistar rat, KFM-Han., outbred, SPF Quality
- Source: KFM Kleintierfarm Madoerin AG (Swiss)
- Weight at study initiation: male: 221.1 - 320.7 g, female: 204.1 - 265.2 g
- Age at start of treatment: 10 weeks males, 13 weeks females
- Acclimation: at least 7 days
- Controls: no
Environmental conditions: - Feed: complete feed for rats (KLIBA rart maintenance diet), ad libitum
- Water: tap water ad libitum
- Room temperature: 22°C +/- 3°C
- Humidity: 40 - 70 %
- Air changes: 10 - 15 per hour
- Dark/light: 12 hours dark period and 12 hours artificial fluorescent light period

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
nose only
Vehicle:
clean air
Details on inhalation exposure:
ADMINISTRATION: 
- Type of exposure: flow-past nose-only inhalation
- Exposure apparatus: Aimals are confined separately in tubes which are positioned radially around the exposure chamber (see illustration below)
- Exposure chamber volume: Internal active volume of the chamber for exposing 40 animals in 1 L
- Method of holding animals in test chamber: Different size MAKROLON animal restraint tubes
- System of generating particulates/aerosols: Hospitak No. 950 nebulizer and  dilution system (clean air), symmetrical top-down flow of aerosol to  
animals'  noses and further
- Method of particle size determination: Using a Mercer 7 stage cascade impactor, sampling air flow rate was 1.0 l/min
- Temperature, humidity, concentration, Particle size distribution and oxygen content in chamber: Determination was performed at the position of
the animals snout in the exposure system

EXAMINATIONS:
- Analysis of test atmosphere: Sampling close to the animals' noses with Gelman A/E 47 mm diameter  glass fiber filters; monitoring of relative 
aerosol concentration using a  RAM-1 light scattering type aerosol monitor.   In addition, collection of test atmosphere in three bottles filled with  
ethyl acetate and cooled with dry ice, subsequent analysis with gas  chromatography
- Particle size (gravimetric): Once during each exposure
- Concentration (gravimetric): At regular intervals during each exposure
- Concentration (analytic): Three times during each exposure
- Oxygen content, humidity, temperature: Once during each exposure
- Air flow rate: Monitored indirectly during the exposure period through the aerosol generation and dilution systems

TEST ATMOSPHERE
- Gravimetric concentrations:  mg/L air: 0.205 (group 1), 0.006 (group 2), 0.044 (group 3), 0.097 (group 4)
- Temperature, humidity, oxygen content: 19.0 - 20.0 °C, 0 - 5 %, 20.9 %
Analytical verification of test atmosphere concentrations:
yes
Remarks:
GC
Duration of exposure:
4 h
Concentrations:
0.008, 0.035, 0.090 and 0.180 mg/L air (analytical)
No. of animals per sex per dose:
5
Control animals:
no
Details on study design:
EXAMINATIONS:
- Post dose observation period (including day of exposure as day 1):    0.180 mg/L: 2 days (all dead)  0.008 mg/L: 16 days   
0.035 mg/L: 26 days   0.090 mg/L: 22 days
- Mortality/viability: At least four times on test day 1 and twice daily  thereafter.
- Body weights: On days 1 (day of exposure), 8, 15 and 22 of test, and also on test day 3 for group 4.
- Symptoms: At least four times on test day 1 and at least daily thereafter.  During exposure only grossly abnormal signs could be noted, due to the   animals being in restraint tubes. General behavior, motor susceptibility,  body position, motility, respiration, skin / fur, eyes, and nose were  
characterized in addition to potential emaciation, poor condition,  salivation, crying, diarrhea and distended abdomen.
- Necropsies of all animals
Statistics:
LoGIT-Model was used to calculate the LC50

Results and discussion

Preliminary study:
not applicable
Effect levels
Sex:
male/female
Dose descriptor:
LC50
Effect level:
0.05 mg/L air
95% CL:
>= 0.042 - <= 0.059
Exp. duration:
4 h
Mortality:
Analytical concentration Death rate
0.008 mg/L air 0 %
0.035 mg/L air 60 % ( 1 male, 5 females)
0.090 mg/L air 40 % (3 males, 1 female)
0.180 mg/L air 100 % ( 5 males, 5 females)
Clinical signs:
other: 0.008 mg/L air (2): Breathing difficulty, piloerection, sedation and nose bleeding were observed after exposure. Animals had recovered on test day 3. 0.035 mg/L air (3): Breathing difficulty, sedation, piloerection and salivation were observed following e
Body weight:
see "Clinical signs" and "Attached background material"
Gross pathology:
No abnormal observations were made in the lowest dose group (0.008 mg/L air). In the other groups, the most frequent abnormality was the
presence of red foci on all lung lobes: 3 males and 5 females at the concentration of 0.035 mg/L air, 3 males and 1 female at the concentration of
0.090 mg/L air and all animals in the 0.180 mg/L air dose group. Two females of the 0.090 mg/L air group had one red lobe which could not be
inflated with formaldehyde.
POTENTIAL TARGET ORGANS: Respiratory tract
Other findings:
no

Any other information on results incl. tables

no further remarks

Applicant's summary and conclusion

Conclusions:
Using the LOGIT-Model, the LC50 of the test item in rats of both sexes, observed over a period of 26 days was estimated to be: 0.050 mg/L AIR , 95 % Confidence limits : 0.042 - 0.059 mg/L air
Executive summary:

The purpose of this 4-hour acute inhalation toxicity study was to assess the toxicological profile of the test item when administered to rats by inhalation and followed over an observation period of 26 days.

Rats of both sexes were exposed to during a 4-hour period to the test item via the inhalation route. The followig concentrations were used:

Group              Concentration (mg/L air)

Analytic              Gravimetric

1                 0.180                    0.205

2                 0.008                    0.006

3                 0.035                    0.044

4                 0.090                    0.097

After 4 -hour inhalation period the following death rate was observed:

Analytical concentration                     Death rate

0.008 mg/L air                                      0 %

0.035 mg/L air                                     60 % ( 1 male, 5 females)

0.090 mg/L air                                     40 % (3 males, 1 female)

0.180 mg/L air                                    100 % ( 5 males, 5 females)

Following symptoms were observed after exposure:

In group 2 (008 mg/L air) animals showed breathing difficulty, piloerection, sedation and nose bleeding. Animals had

recovered on test day 3. In group 3 (0.035 mg/L air) breathing difficulty, sedation, piloerection and salivation were observed following exposure. One male rat died on test day 10. All females died between test day 8 and 13. In the surviving males, breathing difficulty persisted until test day 20 and piloerection until test day 13. Weakness started to appear by the end of the second week of observation. In both sexes, a marked decrease in body weight was observed during the first week of observation. Animals in group 4 (0.090 mg/L air) showed sedation, piloerection, salivation, nose bleeding and marked breathing difficulty after exposure. Three males diedwithin 24 hours following the onset of exposure. In surviving animals breathing difficulty and piloerection persisted until the end of the 22 day's obervation period. In the females, all except one survived until the end of the observation period. All surviving animals lost weight during the two first weeks of observation. In Group 1 (0.180 mg/L air) breathing difficulty, nose bleeding, piloerection and stagger were noted following exposure. All animals died within 24 hours following the onset of exposure.

All animals surviving to the end of the observation period were killed and necrosied. No abnormal observations were made in the lowest dose group (0.008 mg/L air). In the other groups, the most frequent abnormality was the presence of red foci on all lung lobes: 3 males and 5 females at the concentration of 0.035 mg/L air, 3 males and 1 female at the concentration of 0.090 mg/L air and all animals in the 0.180 mg/L air dose group. Two females of the 0.090 mg/L air group had one red lobe which could not be inflated with formaldehyde.

Using the LOGIT-Model, the LC50 of the test item in rats of both sexes, observed over a period of 26 days was estimated to be: 0.050 mg/L AIR , 95 % Confidence limits : 0.042 - 0.059 mg/L air