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Carcinogenicity

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Description of key information

1. Carcinogenitcity study - Read across from Toluene diisocyanate, Loeser et al. (1983), similar to OECD TG451, rats and mice, inhalation, 0.05 or 0.15 ppm for approximately 2 years (6 h/day, 5 days a week), NOEAC 0.05 ppm for mice and 0.15 ppm for rats
2. Carcinogenitcity study - Read across from Toluene diisocyanate, Gordon et al. (1986), similar to OECD TG451, rats and mice, oral exposure, rats:30 mg/kg (males), 60 mg/kg and 120 mg/kg (females), mice: 60 mg/kg (females), 120 mg/kg, and 240 mg/kg (males) for 105 or 106 weeks (5 days a week), carcinogenicity in rats, carcinogenicity in female mice from 60 mg/kg on, no carcinogenicity in male mice
3. Prediction using Toxtree - structural alerts for genotoxic, but not for non-genotoxic carcinogenicity
4. Toolbox export file (see IUCLID)

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records
Reference
Endpoint:
carcinogenicity: oral
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
December, 1978 - January. 1981
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: well documented peer-reviewed NTP report
Reference:
Composition 0
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 451 (Carcinogenicity Studies)
GLP compliance:
yes
Test material information:
Composition 1
Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS:
- Source: Harlan Industries
- Age at study initiation: 12 weeks
- Weight at study initiation: males ca. 180-200 g, females: ca. 130 - 140 g
- Housing: five per cage in polycarbonate cages covered with nonwoven filter sheets. Racks and filters were changed once every 2 weeks. Cages, bedding, and glass water bottles (equipped with stainless steel sipper tubes) were replaced twice per week
- Diet (e.g. ad libitum): feed was available ad libitum.
- Water (e.g. ad libitum): Tap water (acidified to pH 2.5 for bacterial control) was available ad libitum.
- Acclimation period: 6 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20°- 26°C
- Humidity (%): 20%-78%
- Air changes (per hr): Twelve to 15 changes of room air per hour were provided.
- Photoperiod (hrs dark / hrs light): Fluorescent lighting provided illumination 12 hours per day
Route of administration:
oral: gavage
Vehicle:
corn oil
Remarks:
Dosage analyses of toluene diisocyanate indicated that the chemical had reacted in the corn oil vehicle, resulting in actual gavage concentrations 77% to 90% of theoretical values.
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
Doses were prepared by weighing appropriate amounts of TDI and mixing them with enough corn oil of normal moisture content (0.05%) to give the desired concentrations.
As a part of the initial stability analysis of gavage solutions, Midwest Research Institute determined that TDI reacted very rapidly with water - approximately 20% remained less than 15 minutes after the aqueous solution was prepared (MRI Report, August 7. 1975). Campbell et al., (1975 and 1976) have reported that, upon reaction with water, TDI forms a disubstituted urea, N,N'-bis(3-isocyanato-4-methylphenyl) urea. This material is insoluble in TDI and precipitates, thereby inhibiting further reaction to form polymers. If TDI is warmed to increase the solubility of this disubstituted urea, the relative amount of the polymers can be increased. It was therefore important that TDI be stored in a dry environment.

VEHICLE
- Justification for use and choice of vehicle (if other than water): corn oil, since TDI reacts with water immediately.
- Concentration in vehicle: Toluene diisocyanate was dissolved in corn oil at concentrations of 9. 18, 36, or 72 mg/mL. Storage: 1 week at roomtemperature.
- Purity: with a water content of 0.050 %. The dried corn oil used for the stability study contained approximately 0.0053 % water

Gavage solutions were stored at room temperature outside of a desiccator.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Dosage analyses of toluene diisocyanate indicated that the chemical had reacted in the corn oil vehicle, resulting in actual gavage concentrations 77% to 90% of theoretical values.
Toluene diisocyanate (TDI) was unstable in gavage solutions prepared with corn oil of normal moisture content (0.05%) and with corn oil which had been dried to a water content of 0.0057;. After 7 days storage at room temperature, gavage solutions in normal corn oil at dose levels of 9, 36, and 72 mg/mL showed losses of 80%;. 49%, and 27%;. respectively. Gavage solutions prepared at the 9, 36, and 72 mg/mL dose levels with the dried corn oil showed losses of 52%. 32%;. and 19%; respectively after 7 days at room temperature. An evaluation of stability test results revealed that over 90%; of the TDI loss measured in the gavage solutions prepared with dried corn oil was caused by reaction of TDI with components in the corn oil other than water. The same calculations applied to gavage solutions prepared with normal corn oil showed that 12%-98% of the loss could have been caused by reaction with the available water in the oil (theoretical basis) and the remainder was due to reaction of TDI with components of the corn oil.
Duration of treatment / exposure:
106 weeks
Frequency of treatment:
once daily
Remarks:
Doses / Concentrations:
females: 60 or 120 mg/ kg body weight
Basis:

Remarks:
Doses / Concentrations:
males: 30 or 60 mg/ kg body weight
Basis:

No. of animals per sex per dose:
50
Control animals:
yes, concurrent no treatment
Details on study design:
- Dose selection rationale: animals assigned to groups according to a series of computer-generated random numbers

Additional groups of 50 rats of each sex were started as untreated controls but were subsequently sacrificed at 87 weeks.
Positive control:
no data on positive controls available
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: all animals were observed twice daily for mortality and morbidity

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: clinical signs and the results of palpations were recorded every 4 weeks.

BODY WEIGHT: Yes
- Time schedule for examinations: body weights were recorded once per week for the first 13 weeks and then monthly thereafter. The mean body weight of each group was calculated by dividing the total weight of all animals in the group by the number of surviving animals in the group.

OTHER: the classification of neoplastic nodules was done according to the recommendations of Squire and Levitt (1975) and the National Academy of Sciences (1980). When the pathology examination was completed, the slides, individual animal data records, and summary tables were sent to an independent quality assurance laboratory. Individual animal records and tables were compared for accuracy, slides and tissues were verified, and histotechniques were evaluated. All tumour diagnoses, target tissues, and tissues from a randomly selected 10% of the animals were evaluated by a pathologist. Slides of all target tissues and those about which the original and quality assurance pathologists disagreed were submitted to the Chairperson of the Pathology Working Group (PWG) for evaluation. Representative slides selected by the Chairperson were reviewed blindly by PWG pathologists, who reached a consensus and compared their findings with the original diagnoses. When disagreements occurred, the PWG sent the appropriate slides and their comments to the original pathologist for review. (This procedure has been described by Maronpot and Boorman, 1982.) The final diagnosis represents a consensus of contractor pathologists and the NTP Pathology Working Group.
Sacrifice and pathology:
GROSS PATHOLOGY: Yes, moribund animals and animals that survived to the end of the study were killed with carbon dioxide and necropsied. Examinations for grossly visible lesions were performed on major tissues or organs.
Necropsies were performed on all animals found dead and on those killed at the end of the study, unless precluded in whole or in part by autolysis or cannibalization. Thus, the number of animals from which particular organs or tissues were examined microscopically varies and is not necessarily equal to the number of animals that were placed on study in each group.
HISTOPATHOLOGY: Yes, tissues were preserved in 10% neutral buffered formalin, embedded in paraffin, sectioned, and stained with hematoxylin and eosin. The following were examined microscopically: tissue masses, abnormal lymph nodes, skin, mandibular lymph nodes, mammary gland, salivary gland, thigh muscle, sciatic nerve, bone marrow, costochondral junction (rib), thymus, larynx, trachea, lungs and bronchi, heart, thyroid, parathyroid, oesophagus, stomach, duodenum, jejunum, ileum, colon, mesenteric lymph nodes, liver, gallbladder (mice), pancreas, spleen, kidneys, adrenals, bladder, seminal vesicles/ prostate/ testes or ovaries/uterus, brain, and pituitary.
Other examinations:
no information on other examinations available
Statistics:
Probabilities of survival: estimated by product-limit procedure of Kaplan & Meier (1958). All animals dying of accidents or found to be missing were statistically censored from the survival analysis at the time of death.
Statistical analyses for a possible dose-related effect on survival: method of Cox (1972) for testing two groups for equality & Tarone’s (1975) extensions of Cox’s methods for testing for a dose-related trend. All reported P values for the survival analysis are two-sided.
Incidence of neoplastic or non-neoplastic lesions: given as ratio of the number of animals bearing such lesions at a specific anatomic site to the number of animals in which that site was examined.
Statistical analysis of tumour incidence data: two different methods of adjusting for intercurrent mortality were employed. Each used the classical methods for combining contingency tables developed by Mantel & Haenszel (1959). Tests of significance included pairwise comparisons of high and low dose groups with controls and tests for overall dose-response trends.
1. method: assumption that all tumours of a given type observed in animals dying before the end of the study were“fatal”; i.e., they either directly or indirectly caused the death of the animal. So the proportions of tumour-bearing animals in the dosed and control groups were compared at each point in time at which an animal died with a tumour of interest. These results, were then combined by the Mantel-Haenszel methods to obtain an overall P-value. This method of adjusting for intercurrent mortality is the life table method of Cox (1972) and of Tarone (1975).
2. method: assumption that all tumours of a given type observed in animals dying before the end of the study were “incidental’’. So the proportions of animals found to have tumors in dosed and control groups were compared in each of five time intervals: 0-52 weeks, 53-78 weeks, 79-92 weeks, week 93 to the week before the terminal kill, and the terminal kill period.
Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
Survival (all groups) sig. shorter than in controls. Dose-dependent pattern of cumulative toxicity began at 70 weeks & culminated in excessive mortality, indicating the estimated maximum tolerated dose had been exceeded. No other compound-related signs
Mortality:
mortality observed, treatment-related
Description (incidence):
Survival (all groups) sig. shorter than in controls. Dose-dependent pattern of cumulative toxicity began at 70 weeks & culminated in excessive mortality, indicating the estimated maximum tolerated dose had been exceeded. No other compound-related signs
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Depressions in bw gain relative to controls: greater than 10% in all dosed rat groups. Mean body weights of dosed rats were lower than those for the controls after week 10 in males & week 20 in females. The depressions were dose-related.
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
Subcutaneous tissue fibromas or fibrosarcomas (combined) in male rats, mammary gland fibroadenomas in female rats,pancreatic acinar cell adenomas in male rats occurred with a positive trend.
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Lung sections were examined from rats that died during the first 4 months of the studies. All lungs showed marked congestion and variable amounts of pulmonary oedema. Oedema occurred in the bronchioles and alveoli and in a perivascular location.
Histopathological findings: neoplastic:
effects observed, treatment-related
Description (incidence and severity):
The incidences of female rats with neoplastic nodules in the liver occurred with a positive trend (P<0.05; 3/50,8/50, 8/48), and the incidence in the high dose group was higher (P<0.05) than that in the controls.
Details on results:
CLINICAL SIGNS AND MORTALITY
Survival in all groups of dosed rats in the 2-year studies was shorter (P>0.005)than that of the controls. A dose-dependent pattern of cumulative toxicity began at 70 weeks and culminated in excessive mortality, indicating the estimated maximum tolerated dose had been exceeded for rats, Acute bronchopneumonia occurred at increased incidences in groups of dosed male and female rats (males: control, 2/50; low dose, 6/50; high dose, 14/50; females: 1/50, 10/50, 25 / 49). No other. compound-related clinical signs were observed. See table 5.

In male rats, the survival of animals in the two dosed groups was significantly shorter than that of the controls (P<0.001). In females, the survival in each dosed group was significantly shorter than that in the controls (high dose, P<0.001; low dose, P=0.005), and the survival in the high dose group was significantly shorter than that in the low dose group (P=0.001). One control, six low dose, and three high dose males and one high dose female and five low dose females were accidentally killed and were censored from the statistical analysis of survival. In male rats, 36/50 (72%) of the controls, 14/50 (28%) of the low dose, and 8/50 (16%) of the high dose group lived to the end of the study at 108 weeks. In female rats, 36/50 (72%) of the controls, 19/50 (38%) of the low dose, and 6/50 (12%) of the high dose group lived to the end of the study at IO8 weeks. The survival data included one control male and one high dose female that died during the termination period of the study.

BODY WEIGHT AND WEIGHT GAIN
Depressions in mean body weight gain relative to controls were greater than 10% in all dosed at groups throughout most of the study.
Mean body weights of dosed rats were lower than those for the controls after week IO in males and week 20 in females. The depressions in mean body weight gains were dose related. See table 5.

GROSS PATHOLOGY
Subcutaneous tissue fibromas or fibrosarcomas (combined) in male rats occurred with a positive trend (P<0.01; 3/50, 6/50, 12/50). The incidence in the high dose group was higher than that in the controls (P<0.01). The same tumour comparisons were significant (P<0.001) in female rats by the life table analysis. Mammary gland fibroadenomas in female rats occurred with a positive trend (P<0.001), and the incidences in low and high dose groups were significantly higher than that in controls (P<0.01).
Pancreatic acinar cell adenomas in male rats occurred with a positive trend (p<0.05; 1/47, 3/47, 7/49). The incidence in the high dose group was higher than that in the controls (p<0.05).
The incidences of pancreatic islet cell adenomas in female rats were higher by the incidental tumour test (p<0.01) in low dose (6/49) and high dose (2/47) groups than in controls (0/50). An islet cell carcinoma was also observed in a low dose female rat. The incidences of female rats with neoplastic nodules in the liver occurred with a positive trend (P<0.05; 3/50,8/50, 8/48), and the incidence in the high dose group was higher (p<0.05) than that in the controls.

Fibromas or fibrosarcomas occurred in male rats with a statistically significant positive trend, and the incidence in the high dose males was significantly higher than that in the controls (Table 6).
Fibromas or fibrosarcomas also occurred in female rats with a statistically significant positive trend, and the incidence in the high dose females was higher than that in the controls by life table analysis (Table 6).
Mammary Gland: By life table and incidental tumour test analysis, there were statistically significant increases in the incidence of combined mammary gland tumours in female rats in both low dose and high dose groups (Table 7). Since these mammary gland tumours and subcutaneous tissue tumours were all found in the axillary and inguinal areas, they are regarded as all arising from mammary tissue. The survival-adjusted tumour incidences provide a more meaningful comparison than unadjusted overall tumour rates. For example, the first tumour was seen in an animal dying at week 84, and the proportions of animals surviving at least to week 84 with combined mammary gland tumours were: controls, 17/45 (38%); low dose, 25/36 (69%); and high dose, 2 1 / 28 (75%).
There we no differences in the incidence of mammary gland fibroadenomas in male rats after 30 or 60 mg/ kg TDl treatment compared to controls.
Haematopoietic System: Monocytic leukaemia was observed in male and female rats with a statistically significant decreasing trend (Table 8). and the pairwise comparisons between the control and dosed groups were significant. These decreases were not significant by life table analysis.
Pancreas: Acinar cell adenomas were observed in male rats with a statistically significant trend, and the incidence in the high dose group was significantly higher than that in the controls (Table 9). In high dose female rats one acinar cell adenoma and one acinar cell carcinoma were observed.
The adenomas were sharply demarcated from the surrounding tissue and were characterised by a loss of acinar structure, an increase in the number of basophilic cells, and enlarged and irregular nuclei with increased mitotic activity. (Mitoses often averaged one to three per highpower field.) The lesions were usually small, often less than I to 2 millimeters in diameter. A dose-related increase also was observed in the number of male rats with nodular hyperplasia of the pancreatic acinus (control, 0%; low dose, 4%; high dose, 8%).
Islet cell adenomas occurred in female rats with a statistically significant positive trend (Table 9); the incidences of dosed females with these tumours were significantly higher than those in the controls. An islet cell carcinoma was observed in a low dose female rat. The markedly reduced survival in high dose female rats may have been responsible for the lower incidence of islet cell tumours in this group relative to the low dose group. In male rats, pancreatic islet cell adenoma or carcinoma (combined) showed a positive trend and increased incidence in the high dose group by the life table test (Table 9).
Liver: The incidence of female rats with neoplastic nodules occurred with a statistically significant positive trend; the incidence of high dose females with these' nodules was significantly higher than that of the controls (Table 10).
Brain: Gliomas were found in two high dose male rats and a pinealoma was found in a third high dose male.
Lungs: Acute bronchopneumonia was found in increased incidence in dosed rats (males: control, 2/50, 4%; low dose, 6/50, 12%; high dose, 14/50, 28%; females: control, 1/50, 2%; low dose, 10/50,20%; high dose, 25/49,51%;).

HISTOPATHOLOGY: NON-NEOPLASTIC
Lung sections were examined from 11 male and 10 female rats that died during the first 4 months of the studies. All lungs showed marked congestion and variable amounts of pulmonary oedema. Oedema occurred in the bronchioles and alveoli and in a perivascular location. Slight to moderate amounts of perivascular lymphoplasmacytosis were observed in four rats. Necrotising suppurative pneumonia was detected in two rats, and the lungs of one of these animals contained numerous bacteria. Bacteria were also detected in the lungs of two other rats, and a clump of foreign material (presumably of vegetable origin) was found in the bronchus of another animal. Mucocellular exudate was observed in bronchiolar lumens in a moderate number of rats. The presence of trace to very small quantities of pale yellow, slightly refractile material was detected in terminal portions of the respiratory tree (alveoli and terminal bronchioles) in 13/21 lungs examined. In the bronchioles, the material was associated with a stringy pink substance that was suggestive of fibrin and that appeared as an aggregate of vacuoles and strands. Very pale, refractive material was sometimes observed in the vacuoles. Larger, pale yellow, globular bodies were found in respiratory bronchioles and alveoli. The bodies occasionally appeared “fractured’’ and were sometimes associated with an inflammatory reaction.

HISTOPATHOLOGY: NEOPLASTIC (if applicable)

HISTORICAL CONTROL DATA (if applicable): yes
Relevance of carcinogenic effects / potential:
The carcinogenic effects observed in male and female rats indicate that the test substance had a significant carcinogenic effect after oral gavage. A treatment related increase in tumour incidence as compared to controls was shown. As tumours subcutaneous tissue fibromas or fibrosarcomas (combined) in male rats, mammary gland fibroadenomas in female rats, pancreatic acinar cell adenomas in male rats occurred with a positive trend. However the tumours observed are due to metabolism of toluene diisocyanate to toluene diamine (mainly in the gastrointestinal tract) and that metabolite is known to be a potent carcinogen. Additionally the exposure route is not well chosen, since the inhalation route is most relevant to humans. Therefore the results obtained need to be judged carefully.
Dose descriptor:
other:
Effect level:
>= 60 mg/kg bw/day (nominal)
Based on:
other: mammary gland fibroadenomas
Sex:
female
Remarks on result:
other: Effect type: carcinogenicity (migrated information)
Dose descriptor:
other:
Effect level:
>= 60 mg/kg bw/day (nominal)
Sex:
female
Basis for effect level:
other: The incidences of female rats with neoplastic nodules in the liver occurred with a positive trend (P<0.05; 3/50,8/50, 8/48), and the incidence in the high dose group was higher (P<0.05) than that in the controls.
Remarks on result:
other: Effect type: carcinogenicity (migrated information)
Dose descriptor:
other:
Effect level:
>= 30 mg/kg bw/day (nominal)
Based on:
other: Incidence of subcutaneous tissue fibromas or fibrosarcomas
Sex:
male
Remarks on result:
other: Effect type: carcinogenicity (migrated information)
Dose descriptor:
other:
Effect level:
>= 30 mg/kg bw/day (nominal)
Based on:
other: pancreatic acinar cell adenomas
Sex:
male
Remarks on result:
other: Effect type: carcinogenicity (migrated information)

At week 87 untreated controls were sacrificed and examined. The incidence and type of tumors in individual rats did not appear different from the normal background of tumors in the F344/N rat. Thus these data are not given in this report.

Table 5. Mean body weights and survival or rats in the two-year gavage studies of Toluene diisocyanate
Weeks on Study Vehicle Control Low Dose High Dose
Av.Wt (grams) No. of Survivors Av.Wt. (grams) Wt (percent of veh controls) No. of Survivors Av. Wt. (grams) Wt (percent of veh controls) No. of Survivors
MALE
0 184 50 182 99 50 198 108 50
1 200 50 190 95 50 200 100 50
2 211 50 210 100 50 212 100 50
3 224 50 227 101 50 228 102 49
4 240 50 240 100 50 239 100 48
5 233 50 238 103 48 237 102 48
e 233 50 249 98 48 256 101 47
7 282 50 260 99 47 268 102 47
8 272 50 263 97 45 266 98 45
9 288 50 277 96 44 276 96 44
10 283 50 288 95 43 286 94 43
11 288 50 280 95 41 266 90 42
12 297 50 284 96 41 272 92 40
13 302 50 290 96 41 278 92 40
16 323 50 306 95 41 294 91 39
20 3S3 50 338 96 41 309 88 39
24 357 49 338 95 41 323 90 39
28 371 49 351 95 39 330 89 36
32 384 49 368 95 39 341 89 36
36 396 49 367 93 39 338 85 36
40 402 49 378 94 37 341 85 35
44 411 49 378 92 37 339 82 33
48 418 49 387 93 37 343 82 32
52 418 49 385 92 35 337 81 32
56 426 49 388 91 33 335 79 30
60 421 49 379 90 33 325 77 29
64 429 49 386 90 33 332 77 29
68 425 49 382 90 31 324 76 29
72 427 49 376 88 31 324 76 27
76 430 48 377 88 30 325 76 25
80 425 47 370 87 28 329 77 23
84 424 47 370 87 27 327 77 20
88 410 46 354 86 27 323 79 20
92 408 45 358 88 26 314 77 16
96 412 42 365 89 22 316 77 14
100 ??? 39 358 87 20 309 75 13
104 ??? 36 350 86 18 318 78 10
FEMALE
0 130 50 134 103 50 139 107 50
1 137 50 138 101 50 145 106 50
2 146 50 145 99 50 149 102 50
3 154 50 151 98 50 156 101 50
4 161 50 157 98 50 162 101 50
5 161 50 161 100 48 166 103 50
6 167 50 166 99 47 166 99 50
7 171 50 171 100 46 173 101 50
8 174 50 172 99 44 173 99 49
9 178 50 178 100 43 182 102 47
10 180 50 178 98 42 175 97 47
11 181 50 182 101 42 176 97 47
12 185 50 179 97 41 181 98 47
13 186 50 182 98 41 179 96 47
16 191 50 186 97 41 183 96 47
20 205 50 197 96 41 193 94 45
24 209 50 203 97 41 199 95 44
28 211 50 200 95 39 191 91 43
32 220 50 206 94 39 195 89 43
36 228 50 210 92 39 195 86 43
40 232 50 211 91 39 193 83 43
44 236 50 208 88 39 193 82 43
48 237 50 211 89 39 196 83 41
52 237 50 206 87 39 192 81 40
56 246 50 212 86 39 192 78 40
60 242 50 209 86 39 187 77 40
64 252 50 214 85 39 191 76 40
68 261 49 214 82 38 185 71 39
72 267 49 215 81 36 189 71 37
76 275 48 218 79 36 190 69 35
80 277 47 216 78 36 184 66 30
84 284 45 216 76 35 189 67 28
88 282 45 215 76 34 192 68 26
92 286 44 214 75 30 189 66 23
96 291 41 216 74 30 196 67 20
100 293 41 218 74 26 208 71 15
104 297 38 219 74 23 224 75 10

Table 6.Incidences of rats with subcutaneous tumors
  MALES
Vehicle 30 60
  Control mg/kg mg/kg
Fibroma
Overall Incidence 3/50 (6%) 3/50 (6%) 9/50(18%)
Adjusted Incidence 8.3% 16.5% 56.6%
Terminal Incidence 3/36 (8%) 1/14(7%) 3/8 (38%)
Life Table Test P<0.001 P=0.258 P<0.001
Incidental Tumor Test P=0.002 P=0.415 P=0.004
Fibrosarcoma
Overall Incidence 0/50 (0%) 3/50 (6%) 3/50 (6%)
Adjusted Incidence 0.0% 19.0% 23.1%
Terminal Incidence 0/36 (0%) 2/14(14%) 0/8 (0%)
Life Table Test P=0.003 P=0.020 P=0.008
Incidental Tumor Test P=0.021 P=0.044 P=0.089
Fibroma or Fibrosarcoma
Overall Incidence 3/50 (6%) 6/50(12%) 12/50 (24%)
Adjusted Incidence 8.3% 33.5% 66.6%
Terminal Incidence 3/36 (8%) 3/14(21%) 3/8 (38%)
Life Table Test P<0.001 P=0.016 P<0.001
Incidental Tumor Test P<0.001 P=0.056 P<0.001
  FEMALES
Vehicle 60 120
  Control mg/kg mg/kg
Fibroma
Overall Incidence 0/50 (0%) 1/50 (2%) 3/50 (6%)
Adjusted Incidence 0.0% 5.3% 35.7%
Terminal Incidence 0/36 (0%) 1/19(5%) 1/6(17%)
Life Table Test P<0.001 P=0.373 P=0.001
Incidental Tumor Test P=0.019 P=0.373 P=0.083
Fibroma or Fibrosarcoma
Overall Incidence 2/50 (4%) 1/50 (2%) 5/50(10%)
Adjusted Incidence 5.3% 5.3% 51.8%
Terminal Incidence 1/36(3%) 1/19 (5%) 2/6 (33%)
Life Table Test P<0.001 P=0.715N P<0.00l
Incidental Tumor Test P=0.038 P=0.609N P=0.092

Table 7: Combined incidence of mammary gland tumours and subcutaneous tissue tumours in female rats
  Vehicle 60 120
  Control mg/kg mg/kg
Overall Incidence 17/50 (34%) 25/50 (50%) 21/50 (42%)
Adjusted Incidence 43.1% 88.8% 91.1%
Terminal Incidence 14/36 (39%) 16/19(84%) 4/6 (67%)
Life Table Test P<0.001 P<0.00l P<0.001
Incidental Tumor Test P<0.001 P<0.001 P=0.009

Table 8:.Incidences of monocytic leukemia in rats
  MALES
Vehicle 30 60
  Control mg/kg mg/kg
Overall Incidence 11/50 (22%) 4/50 (8%) 4/50 (8%)
Adjusted Incidence 25.5% 19.0% 19.2%
Terminal Incidence 5/36 (14%) 0/14 (0%) 0/8 (0%)
Life Table Test P=0.559N P=0.423N P=0.574
Incidental Tumor Test P=0.027N P=0.053N P=0.039N
  FEMALES
Vehicle 60 120
  Control mg/kg mg/kg
Overall Incidence 21/50 (42%)(a) 7/50(14%) 4/50 (8%)
Adjusted Incidence 47.4% 26.3% 32.9%
Terminal Incidence 13/36 (36%) 2/19(11%) 1/6(17%)
Life Table Test P=0.168N P=0.120N P=0.392N
Incidental Tumor Test P<0.001N P=0.006N P=0.001N
(a)One lymphoma was observed in this group.

Table 9: Incidences of pancreatic lesions in rats
  MALES
Vehicle 30 60
  Control mg/kg mg/kg
Acinar Cell Nodular Hyperplasia Adenoma      
0, 47 (0%) 2 47 (4%) 4 49 (8%)
Overall Incidence 1/47(2%) 3 47(6%) 7 49 (14%)
Adjusted Incidence 2.9% 18.2% 59.2%
Terminal Incidence 1 35(3%) 2 14(14%) 4 8 (50%)
Life Table Test P<0.001 P=0.075 P<0.001
Incidental Tumor Test P<0.001 P=0.128 P=0.001
  MALES
Vehicle 30 60
  Control mg/kg mg/kg
Islet Cell Adenoma or Carcinoma      
Overall Incidence 1,47 (2%) 0 47 (0%) 4 49 (8%)
Adjusted Incidence 2.9% 0.0% 24.2%
Terminal Incidence 1, 35 (3%) 0 14(0%) 1 8 (13%)
Life Table Test P=0.007 P=0.682N P=0.0I3
Incidental Tumor Test P=0.075 P=0.682N P=0.180
  FEMALES
Vehicle 60 120
  Control mg/kg mg/kg
Islet Cell Adenoma      
Overall Incidence 0/50 (0%) 6/49 (12%)(a) 2/47 (4%)
Adjusted Incidence 0.0% 24.2% 33.3%
Terminal Incidence 0/36 (0%) 3/19(16%) 2/6(33%)
Life Table Test P=0.008 P=0.003 P=0.006
Incidental Tumor Test P=0.054 P=0.010 P=0.006
(a)One islet cell carcinoma was also observed in this group.

Table 10: Incidences of neoplastic nodules of the liver in female rats
  Vehicle 60 120
  Control mg/kg mg/kg
Overall Incidence 3/50 (6%) 8/50(16%) 8/48(17%)
Adjusted Incidence 8.0% 30.6% 60.1%
Terminal Incidence 2/36 (6%) 3/19(16%) 3/6 (50%)
Life Table Test P<0.001 P=0.014 P<0.001
Incidental Tumor Test P=0.035 P=0.068 P=0.022
Conclusions:
The study was performed equivalent of similar to the OECD TG451 with only minor deviations and therefore considered to be of high quality (reliability Klimisch 2). The validity criteria of the test system are still fulfilled. The accuracy of the TDI dose mixtures were uncertain because of reactivity with water and the unknown nature of the decomposition products that resulted from preparation of the TDI-corn oil mixtures. Although not every potential discrepancy identified in the audit was fully resolved it was concluded that the data reported were adequate to support the conclusions presented in this Technical Report. Carcinogenic potential of orally administered TDI was evident in rats and in female mice. The test material was considered to be carcinogenic under the conditions of the test.
Executive summary:

The carcinogenicity of toluene diisocyanate after oral administration to rats was investigated by Gordon et al. (1986). The study was conducted equivalent or similar to the OECD Guideline 451. The duration of the study was approximately 2 years. As doses 30 and 60 mg/kg bw (for male rats) and 60 or 120 mg/kg bw (for female rats) of the test substance were administered via gavage. The test substance was analysed analytically and the results revealed that it reacted quickly with the water content of the solvent corn oil. Therefore the actual gavage concentrations were 77% to 90% of theoretical values.Despite the reduced doses, mean body weight gains of male and female rats were less than those of the controls after week 20. Early deaths occurred in groups of dosed male and female rats, but by week 60 only the high dose male rats were dying as a result of TDI administration.An apparent dose-related pattern of mortality began to emerge at week 70, and persisted until the end of the study. The delayed cumulative toxicity caused by TDI administration indicated that the estimated maximum tolerated doses had been exceeded in rats.Bronchopneumonia was the most prominent non-neoplastic effect seen in these gavage studies. In the present study, the late-appearing pattern of mortality in rats could be a reflection of delayed hypersensitivity, as well as direct respiratory irritation. The incidences of bronchopneumonia were dose related in male and female rats, and this effect may have weakened the animals’ resistance to further chemical challenge. The increased rate of mortality may also be due, in part, to TDI’s inhibition of acetylcholinesterase, which could have compounded the animals’ respiratory difficulty. Despite the reduced survival, there was unequivocal evidence of dose-related increases in tumours in rats and mice in the 2-year studies. About 50% of the tumours detected were observed in animals killed at the end of these studies; the rest were found in animals dying between weeks 77 and 108. Tissues associated with the digestive system were primary sites of tumour induction and included acinar cell adenomas of the pancreas in male rats, and liver tumours in female rats. There were also increased incidences of islet cell adenomas in low dose female rats. Dose-related increases were observed in the number of male rats with nodular hyperplasia of the pancreatic acinus (control, 0%; low dose, 4%; high dose, 8%) and in the incidence of acinar cell adenomas (control, 2%; low dose, 6%; high dose, 14%). The corn oil vehicle used in these gavage studies may have contributed to the incidences of acinar cell tumours in male and female rats. The systemic nature of the carcinogenicity of TDI was demonstrated by the appearance of tumours at multiple sites in male rats (fibromas and fibrosarcomas of the skin), in female rats (mammary gland fibroadenomas, adenomas, papillary adenomas, cystadenomas and subcutaneous fibroadenomas and fibromas). The tumours observed in the liver, pancreas, mammary gland, and subcutaneous tissues of F344/N rats in these studies are the same type as those seen when 2,4-diaminotoluene-a possible hydrolysis product of 2,4-toluene diisocyanate was administered to the same strain(NC1, 1979). Differences in mean body weight gains, hypersensitivity, and the incidences of neoplastic and non-neoplastic lesions in animals in the present studies emphasize differences in the degree to which TDI is toxic in different species and sexes. . Both female rats and female mice received doses of 60 or 120 mg/ kg, and most of the rats died during the study. Male mice received higher doses ( 120 and 240 mg/ kg) than male rats (30 and 60 mg/ kg), yet mortality and decreases in mean body weights were less severe in the former group, and no tumours were detected at statistically significant incidences in male mice.

Under the conditions of these gavage studies, the commercial mixture of 2,4- and 2,6-toluene diisocyanate in corn oil was carcinogenic for F344/ N rats, causing subcutaneous fibromas and fibrosarcomas (combined) in males and females, pancreatic acinar cell adenomas in males, and pancreatic islet cell adenomas, neoplastic nodules of the liver, and mammary gland fibroadenomas in females.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEL
30 mg/kg bw/day
Study duration:
chronic
Species:
rat
Quality of whole database:
No carcinogenicity studies are available for TRIDI. Therefore, a chronic carcinogenicity study in rats conducted with TDI, the nearest analogue, is used for the DNEL derivation and further risk assessment.

Carcinogenicity: via inhalation route

Link to relevant study records
Reference
Endpoint:
carcinogenicity: inhalation
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable well documented publication, which meets basic scientific principles
Reference:
Composition 0
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 451 (Carcinogenicity Studies)
Deviations:
yes
Remarks:
6-9 weeks of age at study initiation, only 21 animals per sex/level, no detailed information on housing, diet and water, only 2 dose levels tested, no detailed information which tissues were examined
Principles of method if other than guideline:
Groups of male and female rats were exposed to 0,05 and 0.15 ppm of toluene-diisocyanate (TDI) by inhalation for 6 h/day, 5 days/week for approx. 2 years. Type and incidence of tumours and the number of tumour-bearing animals were recorded. Additionally clinical signs, mortality, body weight gain, haematology, biochemistry, urinalysis, and cytogenicity were recorded. At termination of the study necropsy and histopathological examination were performed and organ weights recorded.
GLP compliance:
not specified
Test material information:
Composition 1
Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River, UK
- Age at study initiation: 6-9-week-old, randomly allocated to exposure and control groups
Route of administration:
inhalation: vapour
Type of inhalation exposure (if applicable):
whole body
Vehicle:
other: TDI-vapour was generated by the passage of dry nitrogen through liquid TDI maintained at 21 °C, The vapour produced was then diluted with air in all-glass systems to produce the exposure concentrations.
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Stainless steel/glass cubical chambers with pyramidal ceilings of approx. 10 m³ were used.
- System of generating particulates/aerosols: TDI-vapour was generated by the passage of dry nitrogen through liquid TDI maintained at 21 °C, The vapour produced was then diluted with air in all-glass systems to produce the exposure concentrations.
- Temperature, humidity, pressure in air chamber: Temperature and humidity in the chambers were recorded daily.

TEST ATMOSPHERE
- Brief description of analytical method used: exposure levels have been monitored using both the U.E.I. Model 7000 TDI Tape monitor and a colorimetric method.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The exposure levels have been monitored using both the U.E.I. Model 7000 TDI Tape monitor and a colorimetric method, The actual levels were: 0.052 ± 0.007 ppm, 0.146 ± 0.014 ppm.
Duration of treatment / exposure:
108 (females) or 110 weeks (males) = approximately 2 years
Frequency of treatment:
6 h/day, 5 days/week
Post exposure period:
No data on post exposure period available.
Remarks:
Doses / Concentrations:
0 ppm
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
0.05 ppm
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
0.15 ppm
Basis:
nominal conc.
No. of animals per sex per dose:
21 rats per sex per level = in total 126 (including animals for interim kill)
Control animals:
yes, concurrent no treatment
Details on study design:
- Dose selection rationale:
Range-finding study
A range-finding study was carried out at another laboratory, and has been reported [2] prior to starting the lifetime studies. Sprague-Dawley rats (Spartan), Fisher 344 rats (Charles River), CD-I mice (Charles River), and Syrian hamsters (Engle Labs.) in groups of 10 animals of each sex and strain were exposed to TDI-vapour for 6 h/day, 5 days/week for a total of 20-22 exposures at levels of 0 (control), 0.1 or 0.3 ppm. Exposure was conducted under dynamic airflow conditions in chambers with quadrangular, pyramidal ceilings. TDI-vapour was generated by metering a calculated amount of liquid TDI into a heated vaporization flask at 220°C. The actual chamber concentrations of TDI were monitored analytically using a modified colorimetric method based on Marcali [1],
Clinical observations and body weights were recorded; haematological (RBC, haemoglobin, haematocrit, total and differential WBC counts) and biochemical (BUN, SGPT, AP) parameters were measured at the end of the study for animals of each sex, species and strain.

- Rationale for animal assignment (if not random): randomly allocated to exposure and control groups

- Other: An additional 5 rats per sex per level were exposed for 4 weeks to conduct the micronucleus test.
Positive control:
No data on positive controls available.
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Clinical signs were recorded at regular intervals

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: clinical signs and ophthalmoscopic observations were recorded at regular intervals

BODY WEIGHT: Yes
- Time schedule for examinations: body weights were recorded at regular intervals

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: ophthalmoscopic observations were recorded at regular intervals
- Dose groups that were examined: 0 ppm, 0.05 ppm and 0.15 ppm

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Haematological (haemoglobin, RBC, PCV, total and differential, white cell count) were measured after 6, 12, 18 months of exposure and terminally.
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: all animals

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: blood biochemical parameters (urea nitrogen, alkaline phosphatase and alanine-aminotransferase) were measured after 6, 12, 18 months of exposure and terminally.
- Animals fasted: No data
- How many animals: all animals

URINALYSIS: Yes
- Time schedule for collection of urine: measured after 6, 12, 18 months of exposure and terminally
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
Sacrifice and pathology:
GROSS PATHOLOGY: Yes (see table)
HISTOPATHOLOGY: Yes (see table)

GROSS PATHOLOGY: Yes (see table)
HISTOPATHOLOGY: Yes (see table)

Animals found dead, killed in extremis or scheduled for interim or terminal kills were subjected to gross and histopathology. Organ weights were recorded at all scheduled necropsies. The following tissues were examined histologically in both studies: adipose tissue, adrenal glands, aorta, blood film, brain (3 levels), caecum, colon, epididymides, eyes, femur (including bone marrow), gonads, heart, intestine, kidneys, liver, lungs (infused), lymph nodes, mammary gland, nasal turbinate (2 levels; mouse terminated, rat in progress), oesophagus, pancreas, pituitary, prostate, salivary glands, sciatic nerve, seminal vesicles, skeletal muscle (m. quadriceps), spinal cord (high cervical), spleen, stomach, thyroid, trachea, urinary bladder, uterus.
Other examinations:
Micronucleus test in rats
The results of the micronucleus test indicate that there was no dose- or treatment-related percentage increase of micronucleated erythrocytes in rats exposed to TDI at levels up to and including 0.15 ppm for 4 weeks.
Statistics:
No additional information on statistics available.
Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
No exposure-related signs occurred during the study. At termination of the study total percentage deaths were 65% in controls, 67% low dose, 71% high dose males & 68% in controls, 75% low dose, 64% high dose females.
Mortality:
mortality observed, treatment-related
Description (incidence):
No exposure-related signs occurred during the study. At termination of the study total percentage deaths were 65% in controls, 67% low dose, 71% high dose males & 68% in controls, 75% low dose, 64% high dose females.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
in all groups during the main part of the study. Significantly less weight gain in the 0.15 ppm group in both sexes in the first 12 weeks of exposure. Weight increases between weeks 12 and 108 show comparable weight gains for all groups.
Food consumption and compound intake (if feeding study):
not specified
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Description (incidence and severity):
No treatment-related changes in haematological parameters were recorded.
Clinical biochemistry findings:
no effects observed
Description (incidence and severity):
No treatment-related changes in blood biochemical parameters were recorded.
Urinalysis findings:
no effects observed
Description (incidence and severity):
No treatment-related changes in urinary parameters were recorded.
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Description (incidence and severity):
The statistical analysis of the organ weights of the animals from interim and terminal kills did not reveal treatment-related differences.
Gross pathological findings:
no effects observed
Description (incidence and severity):
The examination of the tissues did not reveal any evidence of treatment-related effects. Macroscopically no changes were seen in the upper respiratory tract.
Histopathological findings: non-neoplastic:
no effects observed
Description (incidence and severity):
Microscopic evaluation of the tissues revealed some alterations in all groups which were considered incidental and not treatment-related. It should, however, be noted that histopathology of the nasal turbinates is still in progress.
Histopathological findings: neoplastic:
no effects observed
Description (incidence and severity):
Statistical evaluation demonstrated no treatment-related effect on the incidence of tumours, their multiplicity or malignancy.
Details on results:
CLINICAL SIGNS AND MORTALITY
No exposure-related signs occurred during the study. At termination of the study (at week 110 for males and at week 108 for females) total percentage deaths were 65% in controls, 67% low dose, 71% high dose males and 68% in controls, 75% low dose, 64% high dose females. Statistical analysis indicated that TDI did not significantly affect mortality.

BODY WEIGHT AND WEIGHT GAIN
Body weight gain was similar in all groups during the main part of the study. There was, however, significantly less weight gain in the 0.15 ppm group in both sexes in the first 12 weeks of exposure. The weight increases for the periods between weeks 12 and 108 show comparable weight gains for all groups.

OPHTHALMOSCOPIC EXAMINATION
No effects reported.

HAEMATOLOGY
No treatment-related changes in haematological parameters were recorded.

CLINICAL CHEMISTRY
No treatment-related changes in blood biochemical parameters were recorded.

URINALYSIS
No treatment-related changes in urinary parameters were recorded.

ORGAN WEIGHTS
The statistical analysis of the organ weights of the animals from interim and terminal kills did not reveal treatment-related differences.

GROSS PATHOLOGY
At necropsy the examination of the tissues from control and TDI-exposed animals did not reveal any evidence of treatment-related effects. Macroscopically no changes were seen in the upper respiratory tract.

HISTOPATHOLOGY: NON-NEOPLASTIC
Microscopic evaluation of the tissues revealed some alterations in all groups which were considered incidental and not treatment-related. It should, however, be noted that histopathology of the nasal turbinates is still in progress.

HISTOPATHOLOGY: NEOPLASTIC (if applicable)
Statistical evaluation demonstrated no treatment-related effect on the incidence of tumours, their multiplicity or malignancy.
Relevance of carcinogenic effects / potential:
The results of the study did not reveal a substantial carcinogenic potential of TDI, when administered via inhalation to rats.
Dose descriptor:
NOAEC
Remarks on result:
not determinable
Remarks:
no NOAEC identified

Range-finding study:

Male rats of both the Fisher 344 and Sprague-Dawley strain exposed to 0.1 or 0.3 ppm TDI showed a slight but significant reduction in body weight gain. A greater incidence of sneezing occurred in the Sprague-Dawley males suggesting slight respiratory irritation. No adverse effects were observed in the mouse and hamster study.

Rats did not exhibit changes in the lower respiratory tract (histopathology of upper respiratory tract in progress) nor was there any trend of increased mortality in any group. Rats exposed at 0.15 ppm had significantly less increase in weight, only in the first 12 weeks of the study. No specific target tissue has been identified. The tumour pattern in the rat study was similar in the control and in the treated groups and corresponded to historical data. The study demonstrated no evidence of any neoplastic response. These results are supported by tests on mutagenicity. There was no evidence of a mutagenic response in vivo as demonstrated by the results of a micronucleus test on rats and mice exposed for four weeks to TDI at exposure concentrations up to and including 0.15 ppm. As far as the incomplete rat study can be interpreted, levels which cause no primary irritative effect also do not result in any other effect of toxicological significance. As a result of these studies the current occupational exposure levels are not considered to represent a serious health hazard. The possible sensitization to TDI, however, needs special attention.

TABLE I
TDI: LONG-TERM INHALATION STUDY IN RATS
Synopsis of tumour incidence (malignant tumours in brackets).
  Atmospheric concentrations of TDI (ppm)
  0 0.05 0.15
Sex ¿ ¿ ¿ ¿ ¿ ¿
Number of animals examined 104 104 104 105 104 105
Skin/Adnexa/Glands  
carcinoma (basal/squamous etc.) (5) (3) (3) (2) (6) 0
adenoma 0 0 0 0 3 0
papilloma 9 1 5 3 3 0
Mammary gland  
benign tumour (fibroadenoma etc.) 4 24 4 27 2 22
multiple benign tumours 1 55 0 42 1 52
carcinoma + benign tumour (1) (9) 0 (9) 0 (14)
multiple carcinoma + benign tumour 0 (3) 0 (1) 0 0
mammary tumour (unconf.) 0 1 0 0 0 0
Subcutis/muscle/bone  
fibroma 29 1 22 1 35 4
fibrosarcoma (1) (2) (2) 0 (2) 0
lipoma 10 3 6 0 6 3
osteoma 0 0 0 0 1 0
osteosarcoma (1) 0 (1) 0 (1) (1)
lymphangioma 0 0 0 0 1 0
histiocytoma (1) 0 (4) 0 (1) 0
rhabdomyosarcoma 0 0 (1) 0 0 0
sarcoma (unclass.) 0 0 (1) 0 0 0
Haemopoietic/lymphoreticular  
malignant lymphoma (6) (1) 0 (1) (3) (3)
haemangioma 1 1 1 2 4 0
thymus: thymoma 0 (1) 0 1+ (1) 0 1
squamous carcinoma 0 (1) 0 0 0 0
Uterus  
polyp - 5 - 2 - 3
leiomyoma   0 - 1 - 0
sarcoma - 0 - 0 - (1)
Cervix  
stromal tumour - 2 - 2 - 0
Pancreas  
islet cell adenoma 1 1 2 0 3 2
Liver  
angiosarcoma 0 (3) 0 (1) 0 (3)
carcinoma 0 0 (1) 0 0 (1)
cholangiocarcinoma 0 0 (1) 0 0 0
Jejunum  
sarcoma 0 0 (1) 0 0 0
Stomach  
adenocarcinoma 0 0 0 (1) 0 0
Caecum  
schwannoma 0 0 0 0 1 0
leiomyosarcoma 0 0 0 0 0 (1)
Rectum  
polyp 0 0 0 1 0 0
Lungs  
adenoma 2 3 3 0 1 1
Body cavities, membranes, surfaces etc.  
lipoma 0 1 0 0 0 0
mesothelioma 0 0 (1) 0 1 0
liposarcoma 0 0 0 0 (1) 0
haemangioma 0 0 0 0 1 0
lymphangioma 0 0 1 0 0 0
Adrenals  
phaeochromocytoma 1 0 1 0 1 0
cortical adenoma 2 1 1 0 0 1
cortical carcinoma 0 0 0 0 (1) 0
Pituitary  
adenoma 53 64 32 62 38 67
Thyroid  
c-cell carcinoma 0 0 0 (1) 0 0
c-cell adenoma 11 7 3 1 7 4
follicular adenoma 1 0 0 0 0 1
Parathyroids  
adenoma 0 1 0 0 0 0
Brain  
meningioma 0 0 0 0 2 0
astrocytoma 1 0 1 0 0 0
oligodendroglioma 1 0 0 0 0 0
Kidneys  
carcinoma 0 0 0 0 0 (1)
liposarcoma (1) 0 (1) 0 0 0
mesenchymal tumour 1 0 0 0 0 0
lipomatous tumour 1 0 3 0 0 0
nephroblastoma 0 0 1 0 0 0
Testes  
Leydig cell adenoma 2 - 2 - 1 -
Epididymides  
mesothelioma 0 - 1 - 0 -
Prostate  
adenocarcinoma 0 - 0 - (1) -
Ovaries  
granulosa-theca cell - 2 - 0 - 1
Heart  
angiosarcoma 0 (1) 0 0 0 0
Eyes  
leiomyoma 0 0 0 1 1 1
Miscellanous  
squamous cell carcinoma of unknown origin (1) 0 0 0 0 0
Nasal turbinates No macroscopically diagnosed tissue masses. Histopathology in progress.

TABLE II
TDI: LONG-TERM INHALATION STUDY IN RATS
Summary of total tumour incidence
  Males Females
  0 ppm 0.05 ppm 0.15 ppm 0 ppm 0.05 ppm 0.15 ppm
Total animals 104 104 104 104 105 105
Tumour bearers 86 67 81 105 98 101
Animals with malignant tumours 9 3 10 3 4 5
Animals with benign tumours 69 53 64 84 80 76
Animals with both malignant and benign tumours 8 11 7 18 14 20

TABLE III
MICRONUCLEUS TEST ON RATS EXPOSED TO TDI-VAPOUR FOR 4 WEEKS, PERCENTAGE OF MICRONUCLEATED ERYTHROCYTES, MEANS OF 5 ANIMALS PER SEX PER LEVEL ± STANDARD DEVIATION, 1000 RBC PER ANIMAL EXAMINED
  Atmospheric concentration of TDI (ppm)
  0 0.05 0.15
Sex ¿ ¿ ¿ ¿ ¿ ¿
Rats 0.6 ± .9 0.5 ± .2 0.9 ± .4 0.8 ± .l 0.8 ± .2 0.8 ± .4
Conclusions:
The study is considered to be reliable (reliability Klimisch 2). The validity criteria of the test system were fulfilled. The test material did induce slight signs of toxicity but no increased incidence of tumours. The test material was considered to be not carcinogenic after exposure via the inhalation route under the conditions of the test.
Executive summary:

The carcinogenicity of the test material was investigated in rats by Loeser et al (1983). The test was conducted similar to OECD TG451. Groups of male and female rats (21 animals per sex per group) were exposed to 0,05 and 0.15 ppm of toluene-diisocyanate (TDI) by inhalation for 6 h/day, 5 days/week for approx. 2 years. Type and incidence of tumours and the number of tumour-bearing animals were recorded. Additionally clinical signs, mortality, body weight gain, haematology, biochemistry, urinalysis, and cytogenicity were recorded. At termination of the study necropsy and histopathological examination were performed and organ weights recorded. No exposure-related signs occurred during the study. At termination of the study (at week 110 for males and at week 108 for females) total percentage deaths were 65% in controls, 67% low dose, 71% high dose males and 68% in controls, 75% low dose, 64% high dose females. Male and female rats of the 0.15 ppm group gained less weight during the first 12 weeks of the study. Type and incidence of tumours and the number of tumour-bearing animals did not indicate any carcinogenic effect. Haematology, biochemistry, urinalysis, and cytogenicity did not reveal any untoward effect. Histopathological examination in the rat study has not been completed, but no effect in the respiratory tract or in any other tissue has yet been seen.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEC
1.75 mg/m³
Study duration:
chronic
Species:
rat
Quality of whole database:
No carcinogenicity studies are available for TRIDI. Therefore, a chronic carcinogenicity study in rats conducted with TDI, the nearest analogue, is used for the DNEL derivation and further risk assessment.

Additional information

Carcinogenicity study - Read across from Toluene diisocyanate, (Loeser, 1983)

The carcinogenicity of the toluene diisocyanate was investigated in rats and mice by Loeser et al (1983). The test was conducted similar to OECD TG451. Groups of male and female rats (21 rats per sex per group, 30 mice per group) were exposed to 0.05 and 0.15 ppm of test material by inhalation for 6 h/day, 5 days/week for approx. 2 years. Type and incidence of tumours and the number of tumour-bearing animals were recorded. Additionally clinical signs, mortality, body weight gain, haematology, biochemistry, urinalysis, and cytogenicity were recorded. At termination of the study necropsy and histopathological examination were performed and organ weights recorded.No exposure-related signs occurred during the study. At termination of the study (at week 110 for male rats and at week 108 for female rats) total percentage of deaths among the rats were 65% in controls, 67% low dose, 71% high dose males and 68% in controls, 75% low dose, 64% high dose females. Male and female rats of the 0.15 ppm group gained less weight during the first 12 weeks of the study. Type and incidence of tumours and the number of tumour-bearing rats did not indicate any carcinogenic effect. Haematology, biochemistry, urinalysis, and cytogenicity did not reveal any untoward effect. Histopathological examination in the rat study has not been completed, but no effect in the respiratory tract or in any other tissue has yet been seen.

At termination of the study (at week 104) most parameters did not indicate any treatment-related changes in mice . There was a statistically increased mortality in the low- and high-dose female mice (total 77 percentage deaths were 78% / 70% / 70 % male mice and 60% / 77% / 74% female mice (control / low / high dose). Distinct effects occurred in mice: chronic and necrotic rhinitis, bronchitis and higher mortality (females only). Additionally mice at the 0.15 ppm level gained less weight. No specific target tissue, except the respiratory tract in mice, has been identified. The tumour pattern in the mouse study was similar in the control and in the treated groups and corresponded to historical data. The study demonstrated no evidence of any neoplastic response.

0.15 ppm can be considered as NOAEC for carcinogenicity (corresponds to 1.75 mg/m³ for TRIDI).

Carcinogenitcity study - Read across from Toluene diisocyanate, (Gordon et al. 1986) - rats

The carcinogenicity of toluene diisocyanate after oral administration to rats was investigated by Gordon et al. (1986). The study was conducted equivalent or similar to the OECD Guideline 451. The duration of the study was approximately 2 years. As doses 30 and 60 mg/kg bw (for male rats) and 60 or 120 mg/kg bw (for female rats) of the test substance were administered via gavage. The test substance was analysed analytically and the results revealed that it reacted quickly with the water content of the solvent corn oil. Therefore the actual gavage concentrations were 77% to 90% of theoretical values. Despite the reduced doses, mean body weight gains of male and female rats were less than those of the controls after week 20. Early deaths occurred in groups of dosed male and female rats, but by week 60 only the high dose male rats were dying as a result of TDI administration. An apparent dose-related pattern of mortality began to emerge at week 70, and persisted until the end of the study. The delayed cumulative toxicity caused by TDI administration indicated that the estimated maximum tolerated doses had been exceeded in rats.Bronchopneumonia was the most prominent non-neoplastic effect seen in these gavage studies. In the present study, the late-appearing pattern of mortality in rats could be a reflection of delayed hypersensitivity, as well as direct respiratory irritation. The incidences of bronchopneumonia were dose related in male and female rats, and this effect may have weakened the animals’ resistance to further chemical challenge. The increased rate of mortality may also be due, in part, to TDI’s inhibition of acetylcholinesterase, which could have compounded the animals’ respiratory difficulty. Despite the reduced survival, there was unequivocal evidence of dose-related increases in tumours in rats and mice in the 2-year studies. About 50% of the tumours detected were observed in animals killed at the end of these studies; the rest were found in animals dying between weeks 77 and 108. Tissues associated with the digestive system were primary sites of tumour induction and included acinar cell adenomas of the pancreas in male rats, and liver tumours in female rats. There were also increased incidences of islet cell adenomas in low dose female rats. Dose-related increases were observed in the number of male rats with nodular hyperplasia of the pancreatic acinus (control, 0%; low dose, 4%; high dose, 8%) and in the incidence of acinar cell adenomas (control, 2%; low dose, 6%; high dose, 14%). The corn oil vehicle used in these gavage studies may have contributed to the incidences of acinar cell tumours in male and female rats. The systemic nature of the carcinogenicity of TDI was demonstrated by the appearance of tumours at multiple sites in male rats (fibromas and fibrosarcomas of the skin), in female rats (mammary gland fibroadenomas, adenomas, papillary adenomas, cystadenomas and subcutaneous fibroadenomas and fibromas). The tumours observed in the liver, pancreas, mammary gland, and subcutaneous tissues of F344/N rats in these studies are the same type as those seen when 2,4-diaminotoluene - a possible hydrolysis product of 2,4-toluene diisocyanate was administered to the same strain (NC1, 1979). Differences in mean body weight gains, hypersensitivity, and the incidences of neoplastic and non-neoplastic lesions in animals in the present studies emphasize differences in the degree to which TDI is toxic in different species and sexes. Both female rats and female mice received doses of 60 or 120 mg/ kg, and most of the rats died during the study. Male mice received higher doses (120 and 240 mg/ kg) than male rats (30 and 60 mg/ kg), yet mortality and decreases in mean body weights were less severe in the former group, and no tumours were detected at statistically significant incidences in male mice.

Under the conditions of these gavage studies, the commercial mixture of 2,4- and 2,6-toluene diisocyanate in corn oil was carcinogenic for F344/ N rats, causing subcutaneous fibromas and fibrosarcomas (combined) in males and females, pancreatic acinar cell adenomas in males, and pancreatic islet cell adenomas, neoplastic nodules of the liver, and mammary gland fibroadenomas in females.

Carcinogenitcity study - Read across from Toluene diisocyanate, Gordon et al. (1986) - mice

A study on the carcinogenicity of toluene diisocyanate after oral administration to mice was conducted by Gordon et al. (1986). The study was conducted equivalent or similar to the OECD Guideline 451. The duration of the study was approximately 2 years. As doses 120 and 240 mg/kg bw (for male mice) and 60 or 120 mg/kg bw (for female mice) of the test substance were administered via gavage. The test substance was analysed analytically and the results revealed that it reacted quickly with the water content of the solvent corn oil. Therefore the actual gavage concentrations were 77% to 90% of theoretical values. Despite the reduced doses, mean body weight gains of all male and female mice of the high dose group were less than those of the controls. Mortality in male mice was also dose related and significantly higher than in controls, but it was not as excessive as that in rats.Despite the reduced survival, there was unequivocal evidence of dose-related increases in tumours in rats and mice in the 2-year studies. About 50% of the tumours detected were observed in animals killed at the end of these studies; the rest were found in animals dying between weeks 77 and 108. The systemic nature of the carcinogenicity of TDI was demonstrated by the appearance of tumours at multiple sites in female mice (haemangiomas and haemangiosarcomas).Differences in mean body weight gains, hypersensitivity, and the incidences of neoplastic and non-neoplastic lesions in animals in the present studies emphasize differences in the degree to which TDI is toxic in different species and sexes. Both female rats and female mice received doses of 60 or 120 mg/ kg, and most of the rats died during the study. Male mice received higher doses (120 and 240 mg/ kg) than male rats (30 and 60 mg/ kg), yet mortality and decreases in mean body weights were less severe in the former group, and no tumours were detected at statistically significant incidences in male mice.Female mice showed positive evidence of carcinogenicity associated with TDI administration. The species and sex differences in sensitivity to TDI may be metabolic, but no experimental data are available.

Under the conditions of these gavage studies, commercial grade toluene diisocyanate in corn oil was carcinogenic for female B6C3F1 mice, causing haemangiomas or haemangiosarcomas (combined), as well as hepatocellular adenomas. No carcinogenic effect was revealed in male mice.

Prediction using Toxtree (v.2.1.0)

The carcinogenic toxicity potential of 2,4,6-triisopropyl-m-phenylene diisocyanate was assessed using the Toxtree (version 2.1.0.) modelling tool. Toxtree was developed by IDEA Consult Ltd (Sofia, Bulgaria) and is approved and recommended by the EU Joint Research Center in Ispra (Italy) (LINK:http://ecb.jrc.ec.europa.eu/qsar/qsar-tools/index.php?c=TOXTREE). According to the modelling results of Toxtree, structural alerts were identified for genotoxic, but not for non-genotoxic carcinogenicity of 2,4,6-triisopropyl-m-phenylene diisocyanate. Therefore the substance might bear the potential for carcinogenicity.

Prediction using the QSAR OECD Toolbox (v2.2)

The chemical 2,4,6-triisopropyl-m-phenylene diisocyanate (CAS 2162 -73 -4) was evaluated by the QSAR OECD Toolbox software for its carcinogenic potential. The prediction was based on the measured values of chemicals assigned into the category.

The target chemical was classified as "Diisocyanates" by "US EPA New Chemical Categories". Therefore primarily analogues chemicals were searched by this profiling method. 21 chemicals were assigned into the category. However, 49 analogues were identified into the category when grouping chemicals according to their organic functional groups. It was decided to proceed with prediction based on the category of 49 chemicals because the number of chemicals and the data points available for the carcinogenicity endpoint were higher than those in the first category. Thereafter, the chemicals in the category were scanned for the differences relevant for the investigated endpoint. The 3 chemicals in the category exhibited the same mechanism of binding to DNA and to proteins and possess the same organic functional group (isocyanate). LogKow, water solubility, planarity and molecular weight are parameters which can be important for absorption of substance into the organism, therefore these descriptors were taken to build an applicability domain. Some isocyanates are known to be carcinogenic probably due to isocyanate group which can bind to DNA leading to adducts. Although the target chemical falls out of applicability domain because of logKow, water solubility and planarity isocyanate groups in the structure of analogues is crucial factor for exerting toxic activity by prolonged exposures and therefore considered meaningful to accept the prediction.

TRIDI was predicted positive for carcinogenicity.

Conclusion:

The data of toxicokinetic studies revealed that the carcinogenic potential of toluene diisocyanate depends highly on the exposure route. By oral exposure, TDI undergoes hydrolysis in the stomach to form toluene diamine (TDA). By inhalation exposure, TDI is absorbed in the upper respiratory tract and results in the formation of acid-labile conjugates with little diamine formed. The differential formation of TDA via the two routes of exposure may contribute to the mechanism by which TDI was carcinogenic in mice and rats by oral but not inhalation exposure (Doe and Hoffman 1995; IARC 1999; Collins 2002, cited in Screening Assessment for TDIs , 2008). However, the potential occurrence of neoplasms from inhalation exposure cannot be discounted, as it is uncertain whether maximum tolerable doses were attained in the chronic inhalation studies conducted by Loeser et al. (Screening assessment for TDIs, 2008; NTP, 1986).

Although the inhalation exposure is more likely to occur in humans than oral exposure, the exposure levels used by Loeser et al. may not have been optimal doses to adequately detect a potential carcinogenic response. The test substance is therefore judged based on the results obtained by the study of Gordon et al (1986) and the revealed carcinogenic potential provides the basis for classification.


Justification for selection of carcinogenicity via oral route endpoint:
The evaluation of the National Toxicology Program revealed toluene diisocyanate to be carcinogenic only after oral exposure (due to formation of toluene diamine).

Justification for selection of carcinogenicity via inhalation route endpoint:
The evaluation of Loeser and colleagues revealed toluene diisocyanate not to be carcinogenic after exposure via inhalation.

Carcinogenicity: via oral route (target organ): digestive: liver; digestive: pancreas; glandular: mammary gland; other: skin

Justification for classification or non-classification

Carcinogenicity:

The test material requires classification and labelling for carcinogenicity (Cat. 2) in accordance with European regulation (EC) No. 1272/2008.