Registration Dossier

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Administrative data

Description of key information

2,2,4(or2,4,4)-trimethylhexane-1,6 -diisocyanate is of low oral and dermal acute toxicity in rats,

whereas the acute inhalation toxicity data indicate that exposure to respirable aerosols of 2,2,4(or2,4,4)-trimethylhexane-1,6 -diisocyanate confined predominantly to the respiratory tract.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records
Reference
Endpoint:
acute toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1977
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study with acceptable restrictions: LD50 slightly outside range of doses
Principles of method if other than guideline:
based on FDA (1959)
GLP compliance:
no
Test type:
standard acute method
Limit test:
no
Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ORGANISMS: 
- Strain: SPF Wistar
- Source: Winkelmann, Paderborn (Germany)
- Weight at study initiation: 150-200 g
- Controls: no
Environmental conditions: - Feed: complete feed for rats (Ssniff/Intermast)
- Water: tap water ad libitum
- Room temperature: 22°C
- Humidity: 45 - 55 %
Route of administration:
oral: gavage
Vehicle:
other: no vehicle
Details on oral exposure:
ADMINISTRATION: 
- Doses: 5.0; 6.3; 7.9; 10.0 ml/kg bw
- Doses per time period: single dose (gavage)
Doses:
5050; 6363; 7979; 10100 mg/kg bw
No. of animals per sex per dose:
10
Control animals:
no
Details on study design:
EXAMINATIONS:
- Post dose observation period: 14 days
- Body weights: days 0 and 14 (only surviving animals)
- Clinical signs: 20 minutes, 1, 3, 24 hours, 7 and 14 days after dosing
- Mortality: 20 minutes, 1, 3, 24 hours, thereafter daily
- Necropsy: all animals (macroscopic)
Statistics:
Litchfield and Wilcoxon (1949), J. Pharmacol. Exp. Ther. 96, 99
Sex:
male/female
Dose descriptor:
LD50
Effect level:
4 800 mg/kg bw
Mortality:
- Number of deaths at each dose:   
5050 mg/kg bw: 3 males, 3 females died on day 2   
6363 mg/kg bw: 5 males, 4 females died on days 1 (1), 2 (6), 3 (2)   
7979 mg/kg bw: 5 males, 5 females died on days 1 (5), 2 (4), 3 (1)
10100 mg/kg bw: all animals died within 24 hours except 1 male on day 2   
LD50 = 4800 (4030-5710) mg/kg bw
Clinical signs:
CLINICAL SIGNS: Beginning about 20 minutes after treatment and lasting  for approximately 24 hours: Reduced activity, asynchronism, anomalous  
positions, diarrhea, cyanosis, reduced body temperature, piloerection.
Body weight:
Body weight development of of surviving animals was normal:  
 2 males 187.5 g (day 0), 245 g (day 14)  
 3 females 163 g (day 0), 183 g (day 14)
Gross pathology:
NECROPSY FINDINGS: Post mortem sections showed redness of  gastrointestinal mucosa which were severe in animals that died during the  study and slight in surviving animals. 
Other findings:
no other findings

no further information


Conclusions:
In a determination of the acute oral toxicity on male and female rats it was found that the LD50 of the test item 2,2,4(2,4,4)-trimethylhexamethylene-
diisocyanate) is 4800 mg/kg of body weight. Under the conditions of this study the acute toxicity of 2,2,4(2,4,4)-trimethylhexamethylenediisocyanate afer oral application in rats is very low.
Executive summary:

In a determination of the acute oral toxicity on male and female rats it was found that the LD50 of the test item 2,2,4(2,4,4)-trimethylhexamethylenediisocyanate is 4800 mg/kg of body weight. The treated animals showed signs of toxicity beginning about 20 minutes after treatment and lasting  for approximately 24 hours: Reduced activity, asynchronism, anomalous positions, diarrhea, cyanosis, reduced body temperature, piloerection during the 14 day observation period. There was no influence on the increase in body weight. Post mortem sections showed redness of  gastrointestinal mucos a which were severe  in animals that died during the study and slight in surviving animals.  Under the conditions of this study the acute toxicity of 2,2,4(2,4,4)-trimethylhexamethylenediisocyanate after oral application in rats is very low.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
LD50
Value:
4 800 mg/kg bw
Quality of whole database:
Study is comparable to guideline study , supporting studies are well documented and meet generally accepted scientific principles, Klimisch Score 2

Acute toxicity: via inhalation route

Link to relevant study records
Reference
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
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
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
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
Preliminary study:
not applicable
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
no further remarks
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

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LC50
Value:
50 mg/m³
Quality of whole database:
Guideline study with acceptable restrictions: no air control animals; exposure concentrations spaced suboptimal, Klimisch Score 2

Acute toxicity: via dermal route

Link to relevant study records
Reference
Endpoint:
acute toxicity: dermal
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1985-02-04 to 1985-02-08
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 402 (Acute Dermal Toxicity)
Version / remarks:
(1981)
Deviations:
no
GLP compliance:
no
Test type:
standard acute method
Limit test:
no
Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ORGANISMS: 
- Strain: Bor: WISW (SPF TNO)
- Source: F. Winkelmann, Borchen (Germany)
- Weight at study initiation: males mean 259 g, females mean 199 g
- Controls: no
Housing conditions:
- Room temperature 20°C (+/- 1°C)
- Humidity: 60% (+/- 5%)
- Light: 12h per day
- Air exchange: 15-fold per hour
- Access to water: ad libitum
- Diet: R10 diet for rats (Ssniff, Soest)
Type of coverage:
occlusive
Vehicle:
other: no vehicle
Details on dermal exposure:
ADMINISTRATION: 
- Area covered: dorsal skin (shaved 24 hours in advance)
- Occlusion: mull patch, elastic dressing (for 24 hours)
- Removal of test substance: after patch removal, washing with warm water  and swabbing with cellulose

Duration of exposure:
24 h, removal of test substance: after patch removal, washing with warm water  and swabbing with cellulose
Doses:
7000 mg/kg bw
No. of animals per sex per dose:
5
Control animals:
not required
Details on study design:
EXAMINATIONS: 
- Post dose observation period: 14 days
- Body weights: before, and 1, 7, 14 days post dosing
- Clinical signs and mortality: within 6 hours after dosing, thereafter  daily
- Necropsy: all animals (macroscopic), no further details
Statistics:
not required
Sex:
male/female
Dose descriptor:
LD50
Effect level:
> 7 000 mg/kg bw
Mortality:
MORTALITY: No deaths occurred
Clinical signs:
CLINICAL SIGNS: Immediately after treatment, animals showed intense  defense reactions and vocalization, piloerection, agitation, and took a  
stretched (caused by patch), mostly abdominal position. After 24 hours  (patch removal), the skin of the application area showed slight erythema  and severe edema. After 2 days, it showed a brown discoloration and  slight induration. Piloerection was still present, and hypothermia and  slowed down motions were observed in one animal. Except for the local  effects, the animals were free from symptoms after four days. By the end  of the study, the application area showed incrustation and scar  formation. 
Body weight:
Body weight development was transiently inhibited.
Gross pathology:
NECROPSY FINDINGS: Hyperemia in the mucosa of stomach and small  intestine, in peritoneum and diaphragm; mottling on livers and kidneys;  fusion of abdominal organs.
Other findings:
no other findings

no further results

Conclusions:
In a determination of the acute dermal toxicity on male and female rats it was found that the LD50 of the test item 2,2,4(2,4,4)-trimethylhexa-
methylenediisocyanate is greater than 7000 mg/kg of body weight.
Executive summary:

A test performed according to OECD TG 402 with male and female rats (Hüls AG, 1985) demonstrated the low acute dermal toxicity of 2,2,4(2,4,4)-trimethylhexamethylenediisocyanate. No animal (= 0/10) died after 24 hours occlusive application of 7000 mg/kg.   Immediately after treatment, animals showed intense  defense reactions and vocalization,  piloerection, agitation, and took a  stretched (caused by patch), mostly abdominal position. After 24 hours (patch removal),  the skin of the application area  showed slight erythema  and severe edema. After 2 days,  it showed a brown discoloration and  slight induration. Piloerection  was still present, and hypothermia and  slowed down motions were observed in one animal. Except for the local  effects, the animals were free from symptoms after four days. By the end  of the study,  the application area showed incrustation and scar  formation. 

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LD50
Value:
7 000 mg/kg bw
Quality of whole database:
Guideline study, Klimisch score 1

Additional information

2,2,4(or 2,4,4)-trimethylhexane-1,6 -diisocyanate is of low oral and dermal acute toxicity in rats with an oral LD50 of 4800 mg/kg bw and a dermal LD50>7000 mg/kg bw.Toxic symptoms after oral administration included reduced activity, asynchronism, anomalous positions, diarrhea, cyanosis, reduced body temperature, piloerection during the 14 day observation period. There was no influence on the increase in body weight. Post mortem sections showed redness of  gastrointestinal mucosa which were severe  in animals that died during the study and slight in surviving animals.

After dermal administration the skin of the application area  showed slight erythema  and severe edema after 24 hours (patch removal). After 2 days,  it showed a brown discoloration and  slight induration. Piloerection  was still present, and hypothermia and  slowed down motions were observed in one animal. Except for the local  effects, the animals were free from symptoms after four days. By the end  of the study, the application area showed incrustation and scar  formation. 

Assessment of the acute inhalation toxicity data indicates that exposure to respirable aerosols of 2,2,4(or2,4,4)-Trimethylhexane-1,6 -diisocyanate confined predominantly to the respiratory tract. 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.


Justification for selection of acute toxicity – oral endpoint
key study

Justification for selection of acute toxicity – inhalation endpoint
key study

Justification for selection of acute toxicity – dermal endpoint
key study

Justification for classification or non-classification

According to the criteria of EC Directive 67/548/EEC and EC Regulation 1272/2008 and subsequent regulations on classification, labelling and packaging of substances and mixtures and based on the results of the studies for 2,2,4(or 2,4,4)-trimethylhexane-1,6

-diisocyanate is classified for acute inhalation toxicity as category 1, H330