m-tolylidene diisocyanate

Endpoint summary

Description of key information

Acute toxicity: oral
In an NTP study similar to OECD Guideline 401 with rats and mice (NTP, 1986), an LD50 > 2000 mg/kg bw was determined.

Acute toxicity: dermal

In a dermal acute toxicity study according to OECD Guideline 402 in rabbits (Wazeter, 1964), an LD50 > 2000 mg/kg was determined.

Acute toxicity: inhalation
In an inhalation study according to OECD Guideline 403 in rats (Doe/Horspool, 1980), an LC50 = 0.48 mg/L was determined.

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:

data not available

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

no

Remarks:

/ TDI isomer ratio is specified but the purity is not stated.

GLP compliance:

no

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Frederick Cancer Research Center (Frederick MD)
- Age at study initiation: ~10 weeks
- Weight at study initiation: ♀: 144 - 163 g ; ♂: 222 - 272 g
- Housing: two or three per cage
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: ~6 weeks

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

VEHICLE
- Concentration in vehicle: 500 mg/mL
- Preparation: within 2 h of dosing

Doses:

2150, 3160, 4640, 6810, 10000, 14700 mg/kg bw

No. of animals per sex per dose:

5

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations (1) and weighing (2):
(1) Observations for mortality: every 30 minutes for the first 8 hours, then daily for the rest of the study.
(2) Weighing: on test day 1 (prior to administration) and on day 14.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs.

Statistics:

no statistical analysis was used

Key result

Sex:

male

Dose descriptor:

LD50

Effect level:

5 110 mg/kg bw

Based on:

test mat.

Key result

Sex:

female

Dose descriptor:

LD50

Effect level:

4 130 mg/kg bw

Based on:

test mat.

Mortality:

Yes. Mortality increased proportionally to the dose of substance administered. For more details see table 1 in the text field "remarks on results including tables and figures".

Clinical signs:

other: At 10000 or 14700 mg/kg death was preceded by laboured breathing, inactivity and diarrhea.

Gross pathology:

No macroscopic findings were reported.

Other findings:

White crystals in stomach and dark red lungs were found at necropsy. The findings were regarded as dose related.

Table 1: Number of animals dead and time range within which mortality occured

Dose (mg/kg bw)	Mortality (# dead/total)			Time range of deaths (days)
	Male	Female	Combined
2150	2/5	0/5	2/10	(5-9)
3160	3/5	2/5	5/10	(1-14)
4640	2/5	2/5	4/10	(2-10)
6810	2/5	5/5	7/10	(2-5)
10000	5/5	4/5	9/10	(1-3)
14700	5/5	5/5	10/10	(1-2)

Interpretation of results:

GHS criteria not met

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating dose

Value:

2 000 mg/kg bw

Quality of whole database:

Klimisch code 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:

1977-06-16 to 1977-07-30

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

yes

Remarks:

The duration of exposure was 1 h instead of at least 4 h. 4 animals per sex instead of 5. The humidity was low (4 %) instead of 30 - 70 %.

GLP compliance:

no

Test type:

standard acute method

Limit test:

no

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: ABH2146

OTHER SPECIFICS:
- Isomers composition: 79.6 % (2,4 isomer)

Species:

rat

Strain:

other: Alderly Park

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: 6 - 10 weeks
- Weight at study initiation: 150 - 300 g
- Fasting period before study: none
- Housing: 4 rats/cage
- Diet : ad libitum except during the exposure, Oakes Powder 'O' diet
- Water : ad libitum, except during the exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: heated tube
- Exposure chamber volume: a 17 L glass dessicator was used as an exposure chamber (there were no divisions in order to minimise deposition).
- Method of conditioning air: The TDI was dispended into a syringe atomizer by a palmer slow injection apparatus (CF palmer limited). The entrained vapour passed through a heated glass tube (about 120 °C), mixed with diluting air and led into the animal exposure chamber. All air was dried to less than 4 % relative humidity.
- Temperature, humidity, pressure in air chamber: no data, 4 %, no data

TEST ATMOSPHERE
- Brief description of analytical method used: The test atmosphere is drawn throught a glass sintered bubbler containing absolute alcohol. The Isocyanate (Urethane derivative) is subsequently analysed by Liquid Chromatography.
- Samples taken from breathing zone: yes

Analytical verification of test atmosphere concentrations:

yes

Remarks:

A sample of air from the breathing zone of the rats was drawn through two sintered glass absorbers containing 10 mL of absolute alcohol at a rate of 1.25 L/min for 5 min mid-way through each exposure. The trapped isocyanates were then analysed by HPLC.

Duration of exposure:

1 h

Concentrations:

0, 17.4, 25.16, 43.2, 83.9, and 267.1 ppm (0.13, 0.18, 0.31, 0.61, and 1.93 mg/L)

No. of animals per sex per dose:

4

Control animals:

yes

Details on study design:

- Duration of observation period following administration: at least 14 days
- Frequency of observations and weighing: The behaviour of the animals was recorded throughout the exposure. Then, examination and weighing during the following fourteen days were performed at approximately 2 days intervals.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight, lung weight

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

66 ppm

Based on:

test mat.

95% CL:

> 31 - < 141

Exp. duration:

1 h

Remarks on result:

other: (LC50 = 0.48 mg/L) There was no significant difference between the LC50 of male and female rats.

Mortality:

Yes, 11/18 deaths occurred on day 1 or 2. For more details see table 1 in field "Remarks on results including tables and figures".

Clinical signs:

other: At 17.4 ppm: after exposure, all animals were subdued and wheezing. Animals were hunched and blue. 2 females lost weight over 10 days. 1 female died on day 15 and 1 was sacrificed in extremis. At 25.16 ppm: after exposure, all animals were wheezing

Body weight:

All of the animals exposed which survived the first 36 hours after exposure lost weight during the first 4 days of the observation period. Some continued to lose weight and either died or were sacrificed.

Gross pathology:

See remarks.

Other findings:

- Potential target organs: lung
- Organ weights: The lung weights were increased indicating oedema.
- Other observations: Necropsy findings:
(1) At 17.4 ppm, 1 female died on day 15 had dark patches on all lobes of lungs; the animal sacrificed on day 15 had pale inflated lungs with red 2 lobes of right lung; lung weight was high.
(2) At 25.16 ppm: 1 female dying on day 2 had multiple dark red foci on all lung lobes, 2 dark red lobes; others sacrificed at end of study had red foci on lungs and consolidated lobes; 3 males had pale inflated lungs; lung weights were increased.
(3) At 43.2 ppm: animals dying had inflated lungs with dark patches full of fluid; at necropsy, lung weights increased and all lungs were pale, inflated with 2 animals showing dark patches.
(4) At 83.9 ppm: animals dying on study had red foci in lungs and animals surviving had inflated and pale lungs except for red areas of consolidation, lung weights were increased.
(5) At 267.1 ppm: animals dying on day 1 had fluid in lung and thorax, animals dying after day 1 had inflated, red lungs; single survivor had pale enlarged lungs with red spots on all lobes, enlarged adrenals and gray kidneys.

Table 1: Concentrations, time of death and mortality per animals treated

Conc. (ppm)	Isomer ratio 2,4:2,6	Mortality (# dead/total)			Time range of deaths (days)
		Male	Female	Combined
17.4	3.13:1	0/4	1/4	1/8	day 15
25.16	2.53:1	1/4	3/4	4/8	(2-19)
43.2	4.1:1	2/4	1/4	3/8	(2-11)
83.9	3.13:1	1/4	2/4	3/8	(2-4)
267.1	2.27:1	4/4	3/4	7/8	(1-2)
controls	-	0/4	0/4	0/8	-

Interpretation of results:

Category 2 based on GHS criteria

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LC50

Value:

0.48 µg/m³ air

Quality of whole database:

Klimisch code 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

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Deviations:

yes

Remarks:

Two rabbits/sex instead of 5 were tested per group. The skin of half the rabbits in each group was abraded by producing shallow incisions with a scalpel blade.TDI isomer ratio and purity not specified.

GLP compliance:

no

Test type:

standard acute method

Limit test:

no

Species:

rabbit

Strain:

not specified

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 2215 - 3180 g
- Housing: individually in metal cages
- Diet: ad libitum
- Water: ad libitum

Type of coverage:

semiocclusive

Vehicle:

unchanged (no vehicle)

Details on dermal exposure:

TEST SITE
- Area of exposure: ~ 3 inches²
- Type of wrap if used: non-occlusive dressing

REMOVAL OF TEST SUBSTANCE
- Washing: yes
- Time after start of exposure: 24 h

TEST MATERIAL
- Amounts applied: doses of 2500 - 9400 mg/kg

OTHER
TDI applied undiluted to intact or abraded skin of 2 male and 2 female rabbits at doses of 2500 - 9400 mg/kg. The dorsal skin of each rabbit was prepared for treatment by close clipping of the hair with an electric clipper. In addition, the skin of half the rabbits in each group was abraded by producing shallow incisions with a scalpel blade over an area approximately three inches square. The compound was applied to each individual animals in the liquid form as received and administered on a volume basis. The animals were observed daily for a total of 14 days for pharmacotoxic signs and dermal irritation. Body weights were obtained for each animal and a complete necropsy was performed on each animal at termination.

Duration of exposure:

24 h

Doses:

2500, 3900, 6000, and 9400 mg/kg bw

No. of animals per sex per dose:

Four groups of 4 rabbits (2/sex) were used.

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations (1) and weighing (2):
(1) Observations occured daily
(2) weighing occured at the beginning and at the end of the study.
- Necropsy of survivors performed: yes
- Other examinations performed: Signs of dermal irritation

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 9 400 mg/kg bw

Based on:

test mat.

Mortality:

No mortality was observed.

Clinical signs:

other: All animals appeared essentially normal throughout the 14-day observation period.

Gross pathology:

All animals at all dosage levels were considered essentially normal at necropsy examination. No potential target organs were observed. No apparent difference between the sexes was observed.

Other findings:

- Other observations: Dermal irritation was seen at each of the four dosage levels. Peak irritation occurred between the 5th and 10th day after application. During this time, erythema, edema, atonia, and coriaceousness were observed in most cases to a moderate-to-marked degree. From the 8th to the 14th day, moderate-to-marked desquamation and fissuring were observed. This condition subsided by the termination of the study.

Interpretation of results:

GHS criteria not met

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating dose

Value:

2 000 mg/kg bw

Quality of whole database:

Klimisch code 2

Additional information

Acute toxicity: oral

Several tests assessing the oral toxicity of TDI in rats or mice of both sexes are available. A limit test performed by the Ministry of Health of Japan (2001) showed in rats an LD₅₀ value of > 2000 mg/kg bw for both sexes. An NTP study with rats and mice showed also LD₅₀ values > 2000 mg/kg bw (Rat: LD_50male= 5110 mg/kg bw; LD_50female= 4130 mg/kg bw/ Mice: LD_50male = 4130 mg/kg bw; LD_50female= 5620 mg/kg bw). At necropsy, white crystalline material was found in the stomach and dark red lungs were observed. In Wazeter F.X. (1964), the acute oral LD_50male value was determined to be 5840 mg/kg bw. White granular particles were also found in the stomach, and hypoactivity and reduced pain response were observed. Overall, tests assessing the acute oral toxicity of TDI provide consistent evidence of low toxicity after an oral administration.

Acute toxicity: dermal

One study is available for this endpoint. TDI (unspecified isomers) was dermally administered to rabbits. No mortality occured and animals appeared normal throughout the 14-day observation period but skin irritation was noted at all dose levels (2500 to 9400 mg/kg b.w.), at a moderate-to-marked degree. This result shows that TDI is not acutely toxic via the dermal route. The LD50 was > 9400 mg/kg b.w. in rabbits (Wazeter et al., 1964).

Acute toxicity: inhalation

Two reliable studies for the assessment of the inhalation toxicity of TDI are available. Doe and Horspool (1980) determined the 1-hour LC50 in rats at 66 ppm (0.47 mg/L). All animals were exposed whole-body. Animals dying on study or sacrificed at the end of exposure revealed some hemorrhages or edema of the lungs. As part of a micronucleus study, a 6-hour inhalation exposure with a four-day observation period was performed using mice (Mackay, 1992). Exposures were whole body to 80:20 TDI. The LC50 was 14 ppm (0.1 mg/L) for females and 19 ppm (0.14 mg/L) for males. Overall, these results show that TDI is very toxic by inhalation for males. Overall, these results show that TDI is very toxic by inhalation.

  

Justification for classification or non-classification

The available experimental test data are reliable and suitable for classification purposes under Regulation (EC) No 1272/2008.

Discriminating doses for acute oral (> 2000 mg/kg bw) and acute dermal (> 2000 mg/kg bw) toxicity were determined. As a result the substance is not considered to be classified for acute oral or dermal toxicity under Regulation (EC) No 1272/2008, as amended for the tenth time in Regulation (EU) No 2017/776.

TDI has a harmonized classification for acute inhalative toxicity, Category 2 (H330) under Regulation (EC) No 1272/2008. However, the 1-hour LC50 of 0.48 mg/L determined in the key study for this endpoint (Doe and Horspool, 1980) warrants a more severe classification into Category 1 (H330), which is hence adopted as self-classification.