3-Isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, oligomers reaction product with 3-(cyclohexylamino)propane-1-sulfonic acid and N,N-dimethylcyclohexanamine

Endpoint summary

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:

February/March 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 423 (Acute Oral toxicity - Acute Toxic Class Method)

Version / remarks:

(2001)

GLP compliance:

yes (incl. QA statement)

Test type:

acute toxic class method

Limit test:

yes

Specific details on test material used for the study:

- Stability under test conditions: The stability of the substance in the formulation was analytically verified for at least 48 hours.
- The substance in the test item is dissolved in approx. 30 % solvent. Test concentrations in the acute oral toxicity study were adjusted to the substance content (approx. 70 %).

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Strain: RCCHan:WIST
- Source: Harlan GmbH, 5960 AD Horst, Netherlands
- Age at study initiation: approximately 8-12 weeks
- Weight at study initiation: 168-192 g
- Fasting period before study: Food was withheld from the animals for approximately 16-24 h before administration of the test item, and they were fed again approximately 2-4 h after administration.
- Housing: The animals were group caged conventionally in polycarbonate cages on low dust wood granulate bedding.
- Diet and water: ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 2
- Humidity (%): 55 +/- 5
- Air changes (per hr): approx. 10
- Photoperiod (hrs dark / hrs light): 12 / 12

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

VEHICLE: The test substance was formulated in corn oil with the aid of 10 % acetone (dried with molecular sieve).

Administration volume: 10 mL/kg bw

Doses:

2000 mg/kg bw (the test item content was considered)

No. of animals per sex per dose:

6 (3 animals per step)

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Clinical signs and mortality rates were determined several times on the day of administration and subsequently at least once daily. The weight gain was checked weekly until the end of the study.
- Necropsy of survivors performed: yes

Statistics:

The LD50 value was estimated according to OECD TG 423 (2001).

Sex:

female

Dose descriptor:

LD50 cut-off

Effect level:

5 000 mg/kg bw

Based on:

act. ingr.

Remarks on result:

other: cut-off level according to OECD TG 423, Annex 2d

Mortality:

There were no deaths.

Clinical signs:

No clinical signs were observed.

Body weight:

There were no toxicologically significant effects on body weight or body weight gain.

Gross pathology:

The necropsies performed at the end of the study revealed no particular findings.

Executive summary:

An acute oral toxicity study according to OECD TG 423 (Acute Toxic Class Method) was conducted on 6 female rats (3 per step), receiving each a single dose of 2000 mg/kg of the substance formulated in corn oil (the content of the substance in the test item, which is approx. 70 % in approx. 30 % solvent, was considered). No mortalities, no clinical signs, no effects on body weight gain and no gross pathological findings were observed. Therefore, according to the flow chart of the OECD TG 423, Annex 2d, the LD50 cut off for the substance is 5000 mg/kg bw, and the discriminating dose is 2000 mg/kg.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating dose

Value:

2 000 mg/kg bw

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:

January/February 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Version / remarks:

(2009)

GLP compliance:

yes (incl. QA statement)

Test type:

traditional method

Limit test:

yes

Specific details on test material used for the study:

- Stability under test conditions: Analytical investigations verified the stability of the substance in the vehicle used.
- The test substance is a solution in approx. 30 % ethyl acetate. For the generation of a test atmosphere further ethyl acetate was used to decrease viscosity. Since the active ingredient of the test item itself is a solid, the gravimetric concentrations measured during the study reflect the active ingredient of the test item.

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Strain: Hsd Cpb:WU (SPF)
- Source: Harlan-Nederland, AD Horst, Netherlands
- Age at study initiation: approximately 2 months
- Weight at study initiation: At the study start the variation of individual weights did not exceed ± 10 per cent of the mean for each sex
- Housing: singly in conventional Makrolon® Type IIIH cages with gnawing sticks. The legal requirements for housing experimental animals (Directive 2010/63/EU) are followed.
- Diet and water: ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3°C
- Humidity (%): 40 - 60 %
- Air changes (per hr): approximately 10
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

other: ethyl acetate

Mass median aerodynamic diameter (MMAD):

1.61 µm

Geometric standard deviation (GSD):

2.22

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Mode of exposure: Animals were exposed to the aerosolized test substance in restrainers made of Plexiglas. Restrainers were chosen that accommodated the animals' size. The type of exposure principle is comparable with a directed-flow exposure design (Moss and Asgharian, Respiratory Drug Delivery IV, 1994, 197).
- Exposure apparatus: The chambers used are commercially available (TSE, Bad Homburg, Germany) and the performance as well as their validation has been published (Pauluhn, Journal of Applied Toxicology 14, 55-62, 1994, and Pauluhn & Thiel, Journal of Applied Toxicology 27, 160-167, 2007). Each inhalation chamber segment was suitable to accommodate 20 rats at the perimeter location. The ratio between supply and exhaust air was selected so that 85-90 % of the supplied air was extracted via the exhaust air location and, if applicable, via sampling ports. The slight positive balance between the air volume supplied and extracted ensured that no passive influx of air into the exposure chamber occurred.
- Source and rate of air: Conditioned (dry, oil free) compressed air, 15 L/min
- Method of conditioning air: Compressed air was supplied by Boge compressors and was conditioned (freed from water, dust and oil) automatically by a BEKO RA 55 compressed air dryer.
- System of generating particulates/aerosols: Atmosphere for inhalation exposure was generated under dynamic conditions using a digitally controlled Harvard PHD 2000 infusion pump and a modified Schlick nozzle (Schlick GmbH, Coburg, Germany). All liquid containing parts of the nozzle were maintained at the required temperatures (selected during the pre-test phase) using a water jacket connected to a digitally controlled thermostat. Temperature of nozzle was adjusted at 5°C to maintain temporally stable conditions (evaporation of solvent in the nozzle).
- Optimization of respirability: In order to increase the efficiency of the generation of respirable particles and prevent larger particles from entering the chamber a pre-separator (baffle) system was used (Tillery, Environmental Health Perspectives, 16, 25-40, 1976).
- Inhalation chamber equilibrium concentration: The test atmosphere generation conditions provide an adequate number of air exchanges per hour (15 L/min x 60 min/(3.8 L) > 200, continuous generation of test atmosphere). Under such test conditions chamber equilibrium is attained in less than one minute of exposure. At each exposure port a minimal air flow rate of 0.75 L/min was provided. The test atmosphere can by no means be diluted by bias-air-flows.
- Method of particle size determination: The particle-size distribution was analyzed using a BERNER critical orifice cascade impactor.
- Treatment of exhaust air: The exhaust air was purified via filter systems.
- Temperature, humidity: Temperature and humidity measurements were performed by the computerized Data Acquisition and Control System using HC-S3 sensors (Rotronic Messgeräte GmbH, Ettlingen, Germany). The position of the probe was at the exposure location of rats.

TEST ATMOSPHERE
- The integrity end stability of the aerosol generation and exposure system was measured by using a RAS-2 real-time aerosol photometer (MIE, Bedford, Massachusetts, USA).
- Brief description of analytical method used: The test-substance concentration was determined by gravimetric analysis (filter: glass-fiber filter, Sartorius, Gottingen, Germany; digital balance, post-sampling drying period of 30 min at 70°C). This method was used to define the actual concentration.
- Determination of volatile components: The relative proportion of constituents prone to evaporate is determined as follows: aliquots of the test item were added onto glass fiber filters and the filters were allowed to dry under specified conditions (at 70°C drying temperature) over a time period of maximal 3 hours. During this time course that time of drying was defined at which stable conditions are attained. The factor (f) to multiply filter analyses to calculate the actual concentration of the test item including the solvent is determined (factor 1.23).
- Samples taken from breathing zone: yes
- Particle size distribution: The particle size distribution was analysed using a BERNER critical orifice cascade impactor. Aerosol mass < 3 µm: 78.6 % at 3498 mg/m³ (gravimetrical conc.).
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): The respirability of the aerosol was adequate and in compliance with test guidelines, i.e. the average mass median aerodynamic diameter (MMAD) was 1.61 µm at at 3498 mg/m³ (gravimetrical conc.); GSD was 2.22.

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Concentrations:

Target concentration: 5000 mg/m³
The maximum technically attainable concentration was:
- for active ingredient (gravimetric determination): 3498 mg/m³
- for actual test item (substance in approx. 30 % solvent, conc. re-calculated): 4303 mg/m³

No. of animals per sex per dose:

3, additionally 5 animals per sex for vehicle control

Control animals:

yes

Remarks:

Vehicle control (ethyl acetate)

Details on study design:

- Duration of observation period following administration: 2 weeks
- Frequency of observations and weighing: Body weights were measured before exposure (day 0), on days 1, 3, 7, and 14. The appearance and behavior of each rat were examined carefully at least two times on the day of exposure and at least once daily thereafter. Weekend assessments were made once a day (morning). Assessments from restraining tubes were made only if unequivocal signs occurred.
- Necropsy of survivors performed: yes
- Other examinations performed: Reflexes were tested, based on recommendations made by Irwin (Psychopharmacologica 13, 1968, 222-257). Rectal temperatures were measured shortly after cessation of exposure (approximately within ½hour after the end of exposure) using a digital thermometer with a rectal probe for rats.

Statistics:

Body weights: Means and single standard deviations of body weights are calculated. Mean body weights are also depicted graphically as a function of time
(see result section). Since in acute studies individual group means may differ prior to commencement of the first exposure, the body weight gain was statistically evaluated for each group. For these evaluations a one-way ANOVA (vide infra) is used.
Particle size analysis: described in detail in report.
Physiological data: Data of rectal temperature measurements are statistically evaluated using the ANOVA procedure (vide infra).
Randomization: A computerized list of random numbers served the purpose to assign animals at random to the treatment groups.
Analysis of variance (ANOVA): This parametric method checks for normal distribution of data by comparing the median and mean. The groups are compared at a confidence level of (1-a) = 95 % (p = 0.05). The test for the between-group homogeneity of the variance employed Box's test if more than 2 study groups were compared with each other. If the above F-test shows that the intra-group variability is greater than the inter-group variability, this is shown in the Appendix as "no statistical difference between the groups". If a difference is found then a pairwise post-hoc comparison is conducted (1- and 2-sided) using the Games and Howell modification of the Tukey-Kramer significance test. This program was originally obtained from BCTIC.

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 3 498 mg/m³ air

Based on:

act. ingr.

Exp. duration:

4 h

Remarks on result:

other: maximal technical attainable concentration

Mortality:

Mortality did not occur up the technical maximal producible concentration (3498 mg/m³ based on active ingredient).

Clinical signs:

other: Animals of the control group revealed slightly bradypnea and slightly irregular breathing on day 0 after the exposure session. For animals exposed to the test substance the following clinical signs were observed (day 0 - day 1): bradypnea, labored breathi

Body weight:

Comparisons between the control and the exposure groups revealed significant decrease in the incremental body weight gain on day 1. There is evidence of recovery during the postexposure period.

Gross pathology:

No macroscopic findings were observed for animals of the control group. For animals exposed to the test substance the following was detected at necropsy: Two male rats showed few red foci in the lungs and one female rat revealed few light colored areas in the lung.

Other findings:

There were no findings during reflex measurements in rats exposed to the test item.
Statistical comparisons between the control and the exposure groups revealed significant changes in body temperature at 3498 mg/m³ (active ingredient of the test item).

Executive summary:

A study on the acute inhalation toxicity of the test item (solution of the substance at approx. 70 % in 30 % ethyl acetate) has been conducted in accordance with OECD TG 403 and also OECD OECD GD 39. In that study a group of rats was nose-only exposed to the liquid aerosol of the test item at the maximal technically attainable concentration of 4303 mg/m³ (test item including ethylacetate), which corresponds to 3498 mg/m³ pure substance (= "active ingredient"). Since the pure substance itself, without ethylacetate, is solid, gravimetric concentrations were used to reflect the toxicological study results. Further ethyl acetate has been used as vehicle to decrease viscosity. Rats of the control group were exposed to the vehicle (ethyl acetate) under otherwise identical circumstances.

The respirability of the aerosol was adequate and in compliance with test guidelines (MMAD 1.61 µm, GSD 2.22). All rats exposed to 3498 mg/m³ active ingredient showed clinical signs (bradypnea, labored breathing, irregular breathing, motility reduced, atony, high-legged gait, piloerection, haircoat ungroomed, nose/muzzle red encrusted, nostrils with red encrustations). Significantly decreased body temperatures and incremental body weight gain were found at 3498 mg/m³ active ingredient. Mortality did not occur up to the technically maximal producible concentration. After the recovery period, red foci were seen in the lungs of two male rats and few light colored areas were found in the lung of a female rat exposed to the test item.

The LC50 (4 h, both sexes) was therefore concluded to be > 3498 mg/m³ active ingredient (maximal technical attainable concentration) of the test substance.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating conc.

Value:

3 498 mg/m³

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Additional information

An acute oral toxicity study according to OECD TG 423 (Acute Toxic Class Method) is available for the substance. This study was conducted on 6 female rats (3 per step), receiving each a single dose of 2000 mg/kg of the substance formulated in corn oil (the content of the substance in the test item which is approx. 70 % in approx. 30 % solvent, was considered).

No mortalities, no clinical signs, no effects on body weight gain and no gross pathological findings were observed. Therefore, according to the flow chart of the OECD TG 423, Annex 2d, the LD50 cut off is 5000 mg/kg bw, and the discriminating dose is 2000 mg/kg.

 

A study on the acute inhalation toxicity of the test item (solution of the substance at approx. 70 % in 30 % ethyl acetate) has been conducted in accordance with OECD TG 403 and also OECD GD 39. In that study a group of rats was nose-only exposed to the liquid aerosol of the test item at the maximal technically attainable concentration of 4303 mg/m³ (test item including ethylacetate), which corresponds to 3498 mg/m³ pure substance (= "active ingredient"). Since the pure substance itself, without ethylacetate, is solid, gravimetric concentrations were used to reflect the toxicological study results. Further ethyl acetate has been used as vehicle to decrease viscosity. Rats of the control group were exposed to the vehicle (ethyl acetate) under otherwise identical circumstances.

The respirability of the aerosol was adequate and in compliance with test guidelines (MMAD 1.61 µm, GSD 2.22). All rats exposed to 3498 mg/m³ active ingredient showed clinical signs (bradypnea, laboured breathing, irregular breathing, motility reduced, atony, high-legged gait, piloerection, haircoat ungroomed, nose/muzzle red encrusted, nostrils with red encrustations). Significantly decreased body temperatures and incremental body weight gain were found at 3498 mg/m³ active ingredient. Mortality did not occur up to the technically maximal producible concentration. After the recovery period, red foci were seen in the lungs of two male rats and few light coloured areas were found in the lung of a female rat exposed to the test item.

The LC50 (4 h, both sexes) was therefore concluded to be > 3498 mg/m³ active ingredient (maximal technical attainable concentration) of the test substance.

 

No acute dermal toxicity study is available for the substance. However, an assessment of acute dermal toxicity is possible based on the weight of evidences.

The substance has a molecular weight of 222 g/mol (related to the idealised structure of the UVCB), which is not contradictive for systemic availability after dermal exposure. Due to the reactive isocyanate groups the substance is unstable towards nucleophiles, e. g. water or alcohols. The salt character of the idealised substance indicates a certain water solubility, which is not confirmed by experimental data (exp. water solubility < 0.0031 g/L). Thus, if any, dermal absorption is assumed to be low.

Experimental evidence reveals the substance as practically non-toxic after acute oral exposure (LD50 > 2000 mg/kg). In the respective study no mortalities, clinical signs or findings at gross necropsy were observed. No specific toxicity or signs indicating systemic toxicity are revealed from the acute inhalation toxicity study. Also the data for skin sensitisation (LLNA) give no indication for systemic availability, since no skin sensitisation potential was found. Additionally, in vitro data does not lead to the conclusion of a skin irritant effect which then might have an impairment to the protective function of the epidermidis.

Taken together, systemic availability after dermal exposure is not expected to be higher than after oral exposure. With that conclusion, the oral LD50 > 2000 mg/kg and no overt signs of toxicity after oral exposure, it is not expected that an acute dermal toxicity study would reveal adverse systemic effects and thus a positive hazard conclusion. Local effects, on the other hand, were already assessed by the respective skin irritation/corrosion studies.

This assessment of acute dermal toxicity is in line with the recent amendment to REACH Annex VIII (8.5.3) (Reg. (EU) 2016/863) that considers toxicity testing by the dermal route as not needed if a substance does not meet the criteria for classification as acute toxic by the oral route, and with further publications.[1][2]

[1] Moore, Regulatory Toxicology and Pharmacology, 2013, 66, 30-37

[2] Creton, St. et al, Critical reviews in Toxicology, 2010, Vol. 40 No.1, pages 50-83

Justification for classification or non-classification

According to Regulation (EC) No 1272/2008, Annex I, no classification is warranted for acute oral and dermal toxicity.

With the expectation that systemic availability after dermal exposure will not be higher than after oral exposure and the low acute oral toxicity it can be concluded, that no adverse effects after acute dermal exposure.

 

According to Regulation (EC) No 1272/2008, Annex I, no classification is warranted for acute inhalation toxicity.

The LC50 in the acute inhalation toxicity study (4 h, rats) was > 3498 mg/m³. This was the maximum technically achievable concentration of the substance ("active ingredient"), tested as solution in ethyl acetate. No mortality occurred at 3498 mg/m³; only unspecific effects on the respiratory tract and the general condition were observed. Moreover, due to the lack of any apparent test article specific toxicity higher concentrations were considered to be scientifically not justified.