m-TDI oligomers, isocyanurate

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2011

Report date:

2011

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test type:

standard acute method

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

(2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(methyl-m-phenylene) isocyanate

EC Number:

247-840-6

EC Name:

(2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(methyl-m-phenylene) isocyanate

Cas Number:

26603-40-7

Molecular formula:

C27H18N6O6

IUPAC Name:

1,3,5-tris(3-isocyanato-4-methylphenyl)-1,3,5-triazinane-2,4,6-trione

Constituent 2

Reference substance name:

TDI Trimer

IUPAC Name:

TDI Trimer

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan-Nederland, AD Horst, Netherlands
- Strain: HsdCpb:Wu (SPF)
- Age at study initiation: approx. 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
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: at least 5 days

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

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

other: conditioned dry air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Mode of exposure: Animals were exposed to the aerosolized test substance in Plexiglas exposure restrainers applying a directed-flow nose-only exposure principle.
- Aerosol generation: Under dynamic conditions the test substance is atomized into the baffle (pre-separator) of the inhalation chamber. For atomization a binary nozzle and conditioned compressed air (15 L/min) was used. The representative dispersion pressure was approximately 600 kPa (constant liquid feed at 722 µl/min through the nozzle maintained at 10°C to decrease the viscosity and volatility of the test article). Higher temperatures lead to a rapid evaporation of solvent with resultant obliteration of the nozzle. This could be prevented by a lower operating temperature of the nozzle. The neat test article was fed into the nozzle system using a digitally controlled pump (Harvard PHD 2000 infusion pump).
- Inhalation chamber: The aluminium inhalation chamber has the following dimensions: inner diameter = 14 cm, outer diameter = 35 cm (two-chamber system), height = 25 cm (internal volume = about 3.8 L). Details of this modular chamber and its validation have been published previously (Pauluhn, Journal of Applied Toxicology 14: 55-62, 1994).
- Optimization of respirability: In order to increase the efficiency of the generation of fine particles likely to evaporate and to prevent larger particles from entering the chamber a glass-preseparator/ baffle system was used (Tillery et al., 1976).
- Conditioning the compressed air: Compressed air was supplied by Boge compressors and was conditioned (i.e. freed from water, dust, and oil) automatically by a VIA compressed air dryer. Adequate control devices were employed to control supply pressure.
- Inhalation chamber equilibrium concentration: The test atmosphere generation conditions provide an adequate number of air exchanges per hour (> 200 x, continuous generation of test atmosphere). Under such test conditions chamber equilibrium is attained within the first minute of exposure. At each exposure port a minimal air flow rate of 0.75 I/min was provided. The test atmosphere can by no means be diluted by bias-air-flows.
- Exhaust air treatment: The exhaust air was purified via cotton-wool/HEPA filters. These filters were disposed of by Bayer Schering Pharma AG.
- Temperature and humidity measurements: Temperature and humidity measurements are also performed by the computerized Data Acquisition and Control System using HC-S3 sensors (Rotronic, http://www.rotronic-usa.com/prod_oem/hc2%20probes/hc2_main.htm). The position of the probe was at the exposure location of rats. Temperature and humidity data are integrated for 30 seconds and displayed accordingly. The humidity sensors are calibrated using saturated salt solutions according to Greenspan (1977) and Pauluhn (1994) in a two-point calibration at 33% (MgCI2) and at 75% (NaCI) relative humidity. The calibration of the temperature sensors is also checked at two temperatures using reference thermometers.

ANALYSIS OF TEST ATMOSPHERE
- Nominal concentration: The nominal concentration was calculated from the ratio of the total quantity of test item consumed during the exposure period and the total throughput of air through the inhalation chamber. For calculation of the consumed content of neat test article a specific density of 1.01 g x cm-3 was used. The lower analytical concentrations compared with the nominal concentrations are attributed to the efficient removal of larger particles in the baffle/pre-separator system.
- Gravimetric concentration: The test-substance concentration was determined by gravimetric analysis (filter: glass-fiber filter, Sartorius, Göttingen, Germany; digital balance).The mass collected by the filter was converted to the test substance taking into account the concentration of constituents contained in it that are prone to evaporate subsequent to nebulization. The relative proportion of constituents prone to evaporate is determined as follows: aliquots of the test substance 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 will be defined at which stable conditions are attained.
- Samples taken from breathing zone: yes
- Particle size distribution: The particle-size distribution was analyzed using an ANDERSEN cascade impactor and a critical orifice BERNER-type cascade impactor. An adhesive stage coating (silicone spray) was not used to minimize particle bounce. Gravimetric analyses of filters used a digital
balance.
- Respirability: The particle-size distribution achieved was adequate to reach all potential target structures of the respiratory tract.

RESULTS OF PARTICLE-SIZE ANALYSES:
- Particle size distribution: In the 1839 mg/m3 exposure group 66.3 % of particles were < 3 µm.
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): In the 1839 mg/m3 exposure group MMAD was 2.21 µm (GSD: 2.08).

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Concentrations:

target concentration: 5000 mg/m3
gravimetric concentration: 1839 mg/m3

No. of animals per sex per dose:

exposure groups: 3 animals per sex
control groups: 5 animals per sex

Control animals:

yes

Details on study design:

- Duration of observation period following administration: 2 weeks
- Frequency of observations and weighing: clinical signs were examined several times on the day of exposure and at least once daily therafter; body weights were measured before exposure, on days 1, 3 and 7, and weekly thereafter.
- Necropsy of survivors performed: yes
- Other examinations performed: rectaI temperatures were measured shortly after cessation of exposure (approx. within half an hour after the end of exposure); a battery of reflex measurements was made on the first post-exposure day.

Statistics:

-Necropsy flndings: If specific findings occur from the respiratory tract of surviving rats they are evaluated statistically using the pairwise Fisher test after the R x C chi-squared test.
-Body weights: Means and single standard deviations of body weights are calculated. 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.
-Calculation of the LC50: If calculation of a median lethal concentration (LC50) is possible, it is performed by computer (PC) according to the method of AP. Rosiello, I.M. Essigmann, and G.N. Wogan (1977) as modified by Pauluhn (1983). This method is based on the maximurn-likelihood method of C.I. Bliss (1938). If only 2 pairs of values with greater than 0% lethality and less than 100% are available then the first linear approximation is based on these values and a homogeneity test is not performed. In this case the interpolated concentration at 50% lethality is designated at approximate LC50. Additionally, the moving average interpolation according to Schaper et al. (1994) is used for calculation, if applicable.
-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-alpha)= 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 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.

Results and discussion

Effect levels

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 1 839 mg/m³ air

Based on:

test mat.

Exp. duration:

4 h

Remarks on result:

other: NOAEL: < 1839 mg/m3

Mortality:

Mortality did not occur up to the maximum technically attainable concentration.

Clinical signs:

other: Controls: All rats tolerated the exposure without specific signs. Exposure group (males): Bradypnea, labored breathing patterns, motility reduced, limp, piloerection, hair-coat ungroomed, high-legged gait, eyelids closed, nostrils: red encrustations, eyel

Body weight:

Comparisons between the control and the exposure group revealed transient changes in body weights of toxicological significance.

Gross pathology:

A qualitative description, only of findings of toxicological importance and for toxicological evaluation, is given below:

- Animals sacrificed at the end of the observation period: The macroscopic findings of extrapulmonary organs were essentially indistinguishable amongst exposure and control groups. Most of the rats of the exposure groups showed discolorated lungs.

Other findings:

- Rectal temperature:
Statistical comparisons between the control and the exposure group revealed significant changes in body temperature (for details see Table 1 below).

- Reflex measurements:
In comparison to the rats of the control group, two male rats of the exposure group exhibited changes in reflexes.

Any other information on results incl. tables

Table 1: Summary of acute inhalation toxicity (4 hrs, liquid aerosol) of Desmodur RC (25 % in ethyl acetate)

Sex	Gravimetric concentration (mg/m3)	Toxicological results	Onset and duration of signs	Rectal temperature (°C)	Onset and duration of mortality
male	0	0 / 0 / 5	---	38.3	---
	1839	0 / 3 / 3	0d - 5d	31.0 **	---
female	0	0 / 0 / 5	---	38.3	---
	1839	0 / 3 / 3	0d - 4d	31.6 **	---

Toxicological results:

number of dead animals / number of animals with signs after cessation of exposure / number of animals exposed

* = p < 0.05, ** = p < 0.01

Applicant's summary and conclusion

Executive summary:

An acute inhalation study with Desmodur RC (25 % in ethyl acetate) according to OECD TG 403 was conducted on male and female rats, which were nose-only exposed to a liquid aerosol concentration of 1839 mg/m3 (gravimetric concentration). The liquid aerosol was generated so that it was respirable to rats. Mortality did not occur up the maximum technically attainable concentration at 1839 mg/m3. Rats exposed at this concentration displayed the following signs (exposure day up to post-exposure day 5): bradypnea, labored breathing patterns, motility reduced, limp, piloerection, hair-coat ungroomed, high-legged gait, eyelids closed, nostrils: red encrustations, eyelids: red encrustations, cyanosis, decreased body weight, and hypothermia.

The respirability of the aerosol was adequate, i.e. the mass median aerodynamic diameter (MMAD) was 2.2 µm, the geometric standard deviation (GSD) was 2. The verification test without animals clearly demonstrated that the minimization of solvent evaporation at the nozzle (nozzle jacket kept at 10°C) did not prevent crystallization/obstruction to occur. The twofold increase of the liquid flow did not change the exposure concentration to any significant extend. Hence, the exposure concentration examined can truly be judged to be 'the maximum technically attainable concentration'.

In summary, the aerosolized test substance (liquid aerosol of the test article) proved to have essentially no acute inhalation toxicity in rats (LC50: > 1839 mg/m3).