Registration Dossier

Diss Factsheets

Toxicological information

Acute Toxicity: inhalation

Currently viewing:

Administrative data

Endpoint:
acute toxicity: inhalation
Type of information:
migrated information: read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Fully reported guideline study to GLP.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2008
Report date:
2008

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:
acute toxic class method

Test material

Constituent 1
Reference substance name:
9016-87-9
EC Number:
618-498-9
Cas Number:
9016-87-9
IUPAC Name:
9016-87-9
Details on test material:
Test substance: DESMODUR 44 V 20 L
Chemical name: Polymeric Diphenylmethane-4,4'-diisocyanate (MDI-polymer)
Manufacturer: Bayer Material Science, Leverkusen, Germany
Purity: 35.1 % monomeric 4,4'-MDI
62.8 % higher oligomers of MDI
2.2% by-products
Batch no.: P4DB000489 (Tox Id: 10064~)
CAS#: 009016-87-9 (high purity monomeric 4,4'-MDI)
Stability: Stability certified for the duration of study.
Storage conditions: refrigerator (W 4 OC) 1 darkness; room temperature during the course of study.
Handling: Complete exclusion of airlhumidity (head space of containers with MDI purged with nitrogen)
Appearance: Brownish, viscous liquid

Test animals

Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals or test system and environmental conditions:
Healthy young adult SPF bred Wistar rats, strain Hsd Cpb:WU (SPF), from the experimental animal breeder Harlan-Winkelmann GmbH, Borchen (Germany), were used. Animals of this strain have been used at Bayer HealthCare AG in toxicological studies for years. Historical data on their physiology, diseases and spontaneous alterations are available. The state of health of the strain is randomly checked regularly at the instance of the Laboratory Animal Services, Bayer HealthCare AG, for the most important specific infectious pathogens.

Acclimatization: The animals were acclimatized to the animal room conditions for at least 5 days before use. During this period, rats were also acclimatized to the restraining tubes.

Age and weight: At the study start the variation of individual weights did not exceed ± 10 per cent of the mean for each sex (see Appendix). Animals of the weight class used are approximately 2 months old and hence fulfill the criterion for young adults (see Appendix).

Animal housing: During the acclimatization and study periods the animals were housed singly in conventional Makrolon® Type IllH cages (based on A. Spiegel and R. Gönnert, Zschr. Versuchstierkunde, 1, 38 (1961) and G. Meister, Zschr. Versuchstierkunde, 7, 144-1 53 (1 965)). Cages were changed twice a week while unconsumed feed and water bottles were changed once per week. The legal requirements for housing experimental animals (Directive 861609 EEC) were followed.

Bedding: Bedding consisted of low-dust wood granulate from Lignocel BK 8-15
(Rettenmaier).

Animal rooms: All animals were housed in a single room. The animal room environment was as follows:

Room temperature: 22 ± 2°C
Relative humidity: 40 – 80%
Dark/light cycle: 12h/12h; artificial light from 6.00 am to 6.00pm Central European Time
Light intensity: Approximately 14 watt/m2 floor area
Ventilation: Approximately 10 air changes per hour


Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
nose only
Vehicle:
other: unchanged (no vehicle)
Details on inhalation exposure:
Aerosol generation: Atmospheres of the test substance were generated under
dynamic conditions using a digitally controlled Havard PHD 2000 pump and a binary nozzle. For nebulization, conditioned (dry, oil free) compressed air (15 L/min, supply rate: see Table 1 in the Result section, dispersion pressure approximately 600 kPa) was used.

B
Analytical verification of test atmosphere concentrations:
yes
Duration of exposure:
4 h
Concentrations:
250, 300, 400, 440, 500, 550 mg/m3
No. of animals per sex per dose:
5
Control animals:
yes
Details on study design:
Body weights were measured before exposure, on days 1, 3 and 7, and weekly thereafter. Individual weights are also recorded at death, if applicable. The period of observation was for 2 weeks.

Clinical Signs
The appearance and behaviour of each rat were examined carefully several 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 (e.g. spasms, abnormal movements, and severe respiratory signs). Following exposure, observations are made and recorded systematically; individual records are maintained for each animal. Cage-side observations included, but were not limited to, changes in the skin and fur, eyes, mucus membranes, respiratory, circulatory, autonomic and central nervous system, and somatomotor activity and behaviour pattern. Particular attention was directed to observation of tremors, convulsions, alivation, diarrhoea, lethargy, somnolence and prostration. The time of death is recorded as precisely as possible, if applicable. Since these signs can only be assessed adequately from freely moving animals, no specific assessment was performed during exposure while animals were restrained.

Rectal Temperatures
The rectal temperatures were measured shortly after cessation of exposure
(approximately within %hour after the end of exposure) using a digital thermometer with a rectal probe for rats.

Necropsv
All surviving rats were sacrificed at the end of the observation period using sodium pentobarbital (Narcoreno) (approximately 300 mg/kg body weights, intraperitoneal injection). All rats, irrespective of the day of death, were given a gross-pathological examination. Consideration was given to performing a gross necropsy on animals as indicated by the nature of toxic effects, with particular reference to changes related to the respiratory tract. All gross pathological changes were recorded and evaluated.
Statistics:
Calculation of the LC50 is performed by computer according to the method of Rosiello et al. (1977) as modified by Pauluhn (1983). This method is based on the maximum likelihood method of 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 X2-homogeneity test is not performed. In this case the interpolated concentration at 50% lethality is designated the approximate LC50. Additionally, the moving average interpolation according to Schaper et al. (1994) is used for calculation, if applicable.

Results and discussion

Effect levels
Sex:
male/female
Dose descriptor:
LC50
Effect level:
310 mg/m³ air
95% CL:
266 - 361
Exp. duration:
4 h
Mortality:
mortality occurred at 237.3 mg/m3 in a concentration-dependent manner. Details of the method used to calculate the LCs0 are provided in the Appendix. The particle size distribution was not essentially different between groups.

LC50= 3 1 0.24 mg/m3
Confidence interval (95%)= 266.43 - 361.25 mg/m3
Slope= 2.76
LCol= 133.68 mg/m3

Clinical signs:
other: All exposed groups showed clinical signs not seen in controls (details below)
Body weight:
Comparisons between the control and the exposure groups revealed a consistent, concentration-dependent decrease in body weights.
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 were essentially indistinguishable amongst exposure and control groups.

Animals succumbing during the observation period: Nose: white foamy discharge; yellowish and viscous mucous; pleural cavity with yellowish
clear fluid; lung: less collapsed, dark-red, and marbled; trachea with white foamy content; liver, kidneys and spleen with discolorations.
Discolouration of organs post mortem is not a direct compound related effect.
Other findings:
Reflex measurements
A battery of reflex measurements was made on the first post-exposure day. In comparison to the rats of the control group, rats of all exposure groups exhibited concentrations-dependent changes in reflexes

Rectal temperature
Results of the evaluation of the rectal temperature reveal significant changes in body temperature in all exposure groups compared to the controls

Any other information on results incl. tables

Generation and Characterization of Atmosphere

Technical information concerning generation of test atmospheres is provided in

Table 1.

Table I :      Generation and characterization of chamber atmosphere                                (aerosolization of the liquid test article) - Mean values

Group

1

2

3

4

5

6

7

Target Conc. (mg/m3)

0

(air)

250

300

400

440

500

550

Nominal Conc. (mg/m3)

0

369.4

397.2

411.1

494.4

516.7

561.1

Gravimetric Conc. (mg/m3)

-

237.3

299.3

391.7

435

488.8

540

Recovery (%)

Temperature (mean, °C)

-

23.2

64

23.3

75

23.5

95

22.8

88

23.2

95

22.9

96

23.3

Rel. Humidity (mean, %)

10

6

6

8

6

9

6

MMAD (µm)

-

1.55

1.74

1.81

1.76

1.77

1.79

GSD

-

1.70

1.63

1.62

1.62

1.66

1.61

Aerosol Mass 3 µm (5)

-

89.3

86.8

85.4

86.9

85.1

86.1

Mass recovered (mg/m3)

-

230.3

292.2

397.4

440.4

486.9

543.1

MMAD = Mass Median Aerodynamic Diameter, GSD = Geometric Standard Deviation; -- = not applicable.

Signs and Observations

The intensity and time-dependence of the observed signs are presented in the Appendix as incidence tables. A qualitative description, only for the signs of importance for the toxicological evaluation, is given below.

Group 1: All rats tolerated the exposure without specific signs.

Group 2/males: Bradypnea, labored breathing patterns, irregular breathing patterns, piloerection, hair-coat ungroomed, flaccidity, motility reduced, high-legged gait, nasal discharge (serous), nose red encrustations, stridor, nostrils: red encrustations, periorbicular encrustations, lacrimation.

Group 3/males: Bradypnea, labored breathing patterns, piloerection, hair-coat

ungroomed, flaccidity, motility reduced, high-legged gait, nose red encrustations,

stridor, nostrils: red encrustations, periorbicular encrustations, cyanosis, emaciation.

Group 4/males: Bradypnea, labored breathing patterns, irregular breathing patterns, piloerection, hair-coat ungroomed, tremor, flaccidity, motility reduced, high-legged gait, nasal discharge (serous), nose red encrustations, stridor, nostrils: red encrustations, cyanosis.

Group 5/males: Bradypnea, labored breathing patterns, irregular breathing patterns, piloerection, tremor, flaccidity, motility reduced, nasal discharge (serous), nose red encrustations, muzzle red encrustations, nostrils: red encrustations, cyanosis:

Group 6/males: Bradypnea, labored breathing patterns, irregular breathing patterns, breathing sounds, piloerection, hair-coat ungroomed, tremor, flaccidity, motility reduced, high-legged gait, nose red encrustations, stridor, nostrils: red encrustations, periorbicular encrustations, cyanosis.

Group 7/males: Bradypnea, labored breathing patterns, irregular breathing patterns, piloerection, tremor, flaccidity, motility reduced, nose red encrustations.

Group 2/females: Bradypnea, labored breathing patterns, irregular breathing

patterns, piloerection, hair-coat ungroomed, flaccidity, motility reduced, high-legged gait, nose reddened, nasal discharge (serous), nose red encrustations, muzzle red encrustations, stridor, nostrils: red encrustations, emaciation.

Group 3/females: Bradypnea, labored breathing patterns, irregular breathing

patterns, breathing sounds, piloerection, hair-coat ungroorned, flaccidity, motility

reduced, high-legged gait, nasal discharge (serous), nose red encrustations, muzzle red encrustations, stridor, nostrils: red encrustations, periorbicular encrustations, cyanosis, emaciation.

Group 4/females: Bradypnea, labored breathing patterns, irregular breathing

patterns, piloerection, hair-coat ungroorned, tremor, flaccidity, motility reduced, highlegged gait, nasal discharge (serous), nose red encrustations, stridor, nostrils: red encrustations, cyanosis.


Group 5/females: Bradypnea, labored breathing patterns, irregular breathing

patterns, dyspnea, breathing sounds, piloerection, hair-coat ungroomed, tremor,

flaccidity, motility reduced, high-legged gait, nasal discharge (serous), nose red

encrustations, stridor, nostrils: red encrustations, periorbicular encrustations,

cyanosis.

Group 6/lfemales: Bradypnea, labored breathing patterns, irregular breathing

patterns, piloerection, hair-coat ungroorned, tremor, flaccidity, motility reduced, highlegged gait, nasal discharge (serous), nose red encrustations, stridor, nostrils: red encrustations, cyanosis.

Group 7/females: Bradypnea, labored breathing patterns, piloerection, tremor,

flaccidity, motility reduced, nose red encrustations.

Toxicological Results

The results obtained during and after exposures of rats for 4 h to this test substance are summarized in Table 2.

Table 2:      Summary of acute inhalation toxicity - 4 hour exposure to the   aerosol of the liquid test article

N

Group

/sex

Target

Concentration

(mg/m3)

Toxicological

Result

Onset and

Duration of

Signs

Onset of

Mortality

Rectal

Temperature

(°C)

1/m

0

0/0/5

-

-

37.7

2/m

250

2/5/5

0d – 7d

0d, 1d

29.5**

3/m

300

4/5/5

0d – 12d

0d, 1d

28.9**

4/m

400

4/5/5

0d – 7d

1d

29.6**

5/m

440

5/5/5

0d

0d, 1d

29.2**

6/m

500

4/5/5

0d – 7d

0d, 1d

28.5**

7/m

550

5/5/5

0d

1d

28.6**

1/f

0

0/0/5

-

-

38.0

2/f

250

0/5/5

0d – 8d

-

29.9*

3/f

300

1/5/5

0d – 8d

1d

29.8**

4/f

400

4/5/5

0d – 5d

1d

29.3**

5/f

440

3/5/5

0d – 8d

1d, 5d

28.9**

6/f

500

4/5/5

0d – 7d

1d

28.4**

7/f

550

5/5/5

0d

0d, 1d

28.0**

N = group assignment, m = males, f = females, * = p 0.05, ** = p 0.01

Values given in the 'Toxicological results' column are:

            1st = number of dead animals.

            2nd = number of animals with signs after cessation of exposure.

            3rd = number of animals exposed.

Applicant's summary and conclusion