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Administrative data

Description of key information

1) Non-GLP, 13 weeks, Fischer 344 rats, oral gavage, NOEAL males 30 mg/kg bw, females 60 mg/kg bw, questionable reliability
2) Non-GLP, 13 weeks, B6C3F1 mice, oral gavage, NOEAL males 240 mg/kg bw, females 60 mg/kg bw, questionable reliability
3) Non-GLP, 28 days, Spraque-Dawley rats, oral gavage, LOAEL 30 mg/kg kw, questionable reliability
4) carcinogenicity study, Sprague-Dawley rats, inhalation, whole- body, NOAEC 0.15 ppm
5) carcinogenicity study, CD1 mice, inhalation, whole-body, NOAEC 0.15 ppm
6) review on diisocyanates, OEL 0.005 ppm
7) carcinogen profile -Carex Canada, OEL 0.005 ppm for sensitisation and for short term exposure 0.02 ppm.
8) TRGS - MAK 0.005 ppm for Isocyanates

9) Inhalation, pMDI, 2 year, NOEAC 0.2 mg/m³ air, LOEAC 1 mg/ m³, Reutzel et al., 1994

10) Inhalation, MDI, 2 years, NOAEC0.23 mg/m³, Hoymann, 1995

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records
Reference
Endpoint:
sub-chronic toxicity: oral
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
weight of evidence
Justification for type of information:
Please refer to Read-across statement in section 13
Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
1 of 10 males died in the 60 mg/kg bw group. 2 males died in the 120 mg/kg bw group. 1 of 10 males died in the 240 mg/kg bw group. 1 of 10 males (60 and 120 mg/kg bw) and 3 males (240 mg/kg bw) showed respiratory noises.
Mortality:
mortality observed, treatment-related
Description (incidence):
1 of 10 males died in the 60 mg/kg bw group. 2 males died in the 120 mg/kg bw group. 1 of 10 males died in the 240 mg/kg bw group. 1 of 10 males (60 and 120 mg/kg bw) and 3 males (240 mg/kg bw) showed respiratory noises.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
A slight decrease in body weights of all groups of males was evident (down to 89.7 % of the controls in the 240 mg/kg bw dose group).
Food consumption and compound intake (if feeding study):
no effects observed
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:
not specified
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Mukoid bronchopneumonia was evident in 1 of 10 males (60 mg/kg bw), 3 of 10 males and 1 of 10 females (120 mg/kg bw) and in 8 of 10 males and 2 of 10 females (240 mg/kg bw).
Histopathological findings: neoplastic:
no effects observed
Details on results:
no further details available
Dose descriptor:
NOAEL
Effect level:
30 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male
Basis for effect level:
other: not specified
Dose descriptor:
NOAEL
Effect level:
60 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
female
Basis for effect level:
other: not specified
Critical effects observed:
not specified

Table 1: Clinical signs and mortality

Dose (mg/kg bw)  

60

120

240

Mortality

(intercurrent deaths)

1/10 males

2/10 males

1/10 females

Respiratory noises

1/10 males

1/10 males

3/10 males

Table 2: Body weight

Dose (mg/kg bw)

Body weight (percent controls at week 12

Males

Females

60

97.7

100

120

90.7

96.4

240

89.7

94.8

Table 3: Histopathology

Dose (mg/kg bw)  

60

120

240

Mucoid bronchopneumonia

(accumulation of mucoid material in the bronchioles)

- mild to moderate

- moderate to severe

- less severe

1/10 males

3/10 males

1/10 females

8/10 males

2/10 females

Conclusions:
The study is considered to be not reliable (reliability Klimisch 3). However, the validity criteria of the test system were fulfilled. The test material did induce slight signs of toxicity (depression in body weight gain, mucoid bronchopneumonia, mortality). The test material was considered to be toxic via the oral exposure route under the conditions of the test, which is based on the NOEAL values derived from this study (NOAEL: 30 mg/kg bw (male rats) and 60 mg/kg bw (females).
Executive summary:

The study was conducted to provide information on the possible health hazards likely to arise from repeated treatment with the test article m-tolylidene diisocyanate (Gordon, 1978). The test material was administered once daily via oral gavage, 5 days a week, for 13 weeks. The test material was solved in corn oil and administered to six groups, each of ten male and ten female Fischer344 rats, at dietary concentrations of 15, 30, 60, 120 and 240 mg/kg/day. A further group of ten males and ten females was exposed to vehicle only to serve as a control. Clinical signs and bodyweight development were monitored during the study. All animals were subjected to gross necropsy examination and a comprehensive histopathological evaluation of organs and tissues was performed.

There were mortalities and clinically observable signs of toxicity in the test animals the study period. Of the Males treated with 60 mg/kg bw 1 animal died. Additionally 2 males died in the 120 mg/kg bw group and 1 died in the 240 mg/kg bw group. One intercurrent death was noted in females treated at 240 mg/kg bw, which was judged to be related to treatment. 1 of 10 males (60 and 120 mg/kg bw) and 3 males (240 mg/kg bw) showed respiratory noises. A slight decrease in body weights of males treated with 60 mg/kg bw and above was evident (down to 89.7 % of the controls in the 240 mg/kg bw dose group) and in females treated with 120 mg/kg bw and above . Toxicological significant effects (respiratory noises) noted were detected in male animals treated with 60, 120 and 240 mg/kg bw. Histopathological findings were detected in males treated at 60 mg/kg bw and above and in females treated at 120 mg/kg bw and above a dose-related appearance of accumulated mucoid material in the pulmonary bronchioles. Thus, in this rat subchronic repeat dose toxicity study, the No-Observable-Adverse-Effect Level (NOAEL) of the test article m-tolylidene diisocyanate for males is 30 mg/kg/day and for females 60 mg/kg/day.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
30 mg/kg bw/day
Study duration:
subchronic
Species:
rat

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Referenceopen allclose all

Endpoint:
chronic toxicity: inhalation
Remarks:
Carcinogenicity study
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
weight of evidence
Justification for type of information:
Please refer to Read-across statement in section 13
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:
not specified
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.
Dose descriptor:
NOAEC
Effect level:
0.15 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: not specified
Critical effects observed:
not specified

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. The results of the study did not reveal a substantial carcinogenic potential of TDI, when administered via inhalation to rats.
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:
chronic toxicity: inhalation
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
weight of evidence
Justification for type of information:
Please refer to Read-across statement in section 13
Mass median aerodynamic diameter (MMAD):
>= <=
Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
no effects observed
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
not specified
Description (incidence and severity):
see Hoymann et al
Urinalysis findings:
not specified
Description (incidence and severity):
see Hoymann et al
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
effects observed, treatment-related
Details on results:
The major pulmonary effects in the two studies were characterized by hyperplasia, interstitial fibrosis and a low incidence of bronchiolo-alveolar adenoma, the latter occurring in the high exposure groups of both studies (i.e. total inhalation exposures of 17728 and 17575 mg MDI.h/m³). Both studies also reported the presence of particle-laden macrophages predominantly in the alveoli close to the alveolar ducts which in some cases, particularly in high dose groups, were associated with areas of fibrosis.
Dose descriptor:
LOAEC
Effect level:
0.23 mg/m³ air
Based on:
test mat.
Sex:
female
Basis for effect level:
other: not specified
Critical effects observed:
not specified
Conclusions:
The study reported the presence of particle-laden macrophages predominantly in the alveoli close to the alveolar ducts which in some cases, particularly in high dose groups, were associated with areas of fibrosis. It was also suggested (Feron et al., 2001) that the mild histopathological changes seen in the low exposure animals (0.23 mg MDI/m³) in the study reported by Hoymann et al. (1995), would not have occurred if the exposure had been for 6 hours/day. An exposure of 0.2 mg MDI/m³ over a 6 hour period was judged to be the NOAEL.
Executive summary:

In a long-term inhalation study over a maximum of 24 months including satellite groups with 3, 12, and 20-month exposure, the chronic toxicity and carcinogenicity of monomeric methylene diphenyl diisocyanate (MDI) were investigated. Female Wistar rats were exposed in 6 m³ inhalation chambers for 18 hours/day, 5 days/week to 0.23, 0.70 and 2.05 mg/m³ MDI in aerosol form, a control group was kept in clean air. Essentially, a dose-dependent impairment of the lung function in the sense of an obstructive-restrictive malfunction with diffusion disorder, increased lung weights, an inflammatory reaction with increased appearance of lymphocytes (but not of granulocytes) in the lung in the high dose group as a sign of specific stimulation of the immune system by MDI, an intermediately retarded lung clearance in the high dose group as well as dose-dependent interstitial and peribronchiolar fibrosis, alveolar bronchiolisations and a proliferation of the alveolar epithelium, which was classified as preneoplastic, as well as a bronchiolo-alveolar adenoma were ascertained. The LOAEC for the female rat was 0.23 mg/m3 after long-term inhalation of 4,4'-MDI aerosols.

Remark: In a chronic rat study with polymeric MDI the NOAEC was 0.2 mg/m³ after aerosol exposure over 2 years (6 hours/day, 5 days/week) (Reuzel et al. (1994), Fund. Appl. Toxicol. 22: 195-210). A comparison of the both chronic rat studies with 4,4'-MDI and polymeric MDI has shown very good consistency across the studies with respect to gradation of inhaled dose and the observed histopathological changes. In this review it turned out that a daily 18 hr-exposure of 0.23 mg/m³ 4,4'-MDI corresponds approximately to a daily 6 hr-exposure of 1 mg/m³ polymeric MDI (Feron et al. (2001), Arch. Toxicol. 75: 159-175).

Endpoint:
repeated dose toxicity: inhalation, other
Remarks:
This publication is a review on diisocyanates in general and the risk emerging from them.
Type of information:
other: This publication is a review on diisocyanates in general and the risk emerging from them.
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: well documented publication, which meets basic scientific principles
Qualifier:
no guideline followed
Principles of method if other than guideline:
Review on diisocyanates in general and the risk emerging of them.
GLP compliance:
not specified
Species:
other: not applicable
Strain:
other: not applicable
Details on test animals and environmental conditions:
not applicable
Route of administration:
inhalation
Type of inhalation exposure:
whole body
Vehicle:
air
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
For the determination of DI different methods are available. In general the limit of quantification is in the range of 1 µg/m³. Considering air analyses in non-trade indoors, sensitive analytical methods have been developed. According to Schmidtke and Seifert (1990), 1-(2-methoxyphenyl)-piperazine is used for the formation of derivates of isocyanites. The derivates are determined by high-pressure liquid chromatography (HPLC) using diode array detector DAD or electrochemical detector (limit of detection = 3 ng/m³) for detection.
Additionally TDI can be determined by gas chromatography (GC) after derivatisation to 2,2,2-trifluorethylamine.
Dose descriptor:
other: maximal workplace concentration
Effect level:
0.005 ppm
Based on:
other: Classification according to MAK and BAT-Value-List, DFG 1999
Sex:
not specified
Basis for effect level:
other: not specified
Critical effects observed:
not specified

According to the derivation of a basic scheme for the creation of benchmarks for the indoor air, the RWII value provides the concentration of a substance, for which when reached or exceeded, immediate action is needed, while at a concentration equal to the RW-I value even for lifetime exposure no health concerns are expected. Due to the specific material properties and their application procedures, it is not advisory for the following reasons to derive such guidelines for DI: The large-scale application of solvent-based DI coatings occur at short notice under adverse conditions, concentrations of DI-monomers or prepolymers, which may result in particularly sensitive individuals to health problems. The monitoring of such short-term exposure is not possible in practice, however, since the concentration rapidly drops in the air after the end of the application. Therefore, the determination of a short-term guideline value II is not advisory. There is no evidence for a continuous emission of monomeric or polymeric DI after completion of the curing process.

The private use of DI-containing compounds in the living area during processing lead to exposures that correspond to those of an industrial workplace. The non-professional user is probably unaware that he should be following the recommendations. Moreover, he is most likely not aware that poor working conditions could lead to a health burden. To avoid such conditions the recommendations for the non-professional use of DI-containing products should be considered.

Table 1: Identification and physical-chemical data of diisocyanates (DI)
Name (according to EU-GefVO and TRGS 900) Diphenyl-methan-4,4'-diisocyanate Hexamethylen-1,6-diisocyanate Isophoron-diisocyanate1) Naphthylen-cyanattoluole 2.4- Diiso- 1.5- diisocyanate 2,6- Diiso-cyanattoluole
Abbreviation MDI HDI IPDI NDI 2,4-TDI 2,6-TDI
CAS-number 101-68 -8 822-06-0 4098-71-9 3173-72-6 584-84-9 91-08-7
EINECS-number 202-966-0 212-485-8 223-861-6 221-641-4 209-544-5 202-039-0
Molecular formula C15H10N2O2 C8H12N2O2 C12H18N2O2 C12H6N2O2 C9H6N2O2 C9H6N2O2
Structural formula see Appendix 1a see Appendix 1b see Appendix 1c see Appendix 1d see Appendix 1e see Appendix 1f
Phys.-chem. data
Molecular Weight 250,3 168,2 222,3 210,2 174,2 174,2
Melting point °C* 39,5 -67 <-70 127 21,8 8,5**
Boiling point* 194°C at 1013hPa 187°C at 133 hPa 216°C at 133 hPa 244°C at 133 hPa 247°C at 1013 hPa 121°C at 13,3hPa
Density at 20°C* 1,324 1,047 1,061 1,45 1,217 1,22
Vapour pressure at 20°C <0,001 hPa** 0,007 hPa** 10-4hPa* 0,004 hPa** 0,013hPa** 0,02 hPa**
Rel. vapour density (Luft=1)** 8,6 5,8 7,7 7,3 6,02 6,02
Conversion: 1 mg/m3=...ppm 0,1 0,14 0,11 0,11 0,14 0,14
Conversion: 1 ppm =...mg/m3 10,4 7 9,2 8,7 7,2 7,2
* Data according to Ullmanns Enzyklopädie der technischen Chemie (1977)
** Data according to Belgische Gefahrstoffdatenbank BIG
1)3-Isocyanatmethyl-3,5,5-trimethylcyclo-hexylisocyanate

Table 2: Established labelling und regulations for diisocyanate identification and physical-chemical data of diisocyanates (DI)
Name Diphenyl-methan-4,4'-diisocyanate Hexamethylen-1,6-diisocyanate Isophoron- diisocyanate1) Naphthylen-cyanattoluole 2.4- Diiso- 1.5- diisocyanate 2,6- Diiso-cyanattoluole
Abbreviation MDI HDI IPDI NDI 2,4-TDI 2,6-TDI
Labelling Xn T T,N Xn T+ T
according to EU-GefVO (1999) R 20-36/37/ R 23-36/37/ R 23-36/37/38-42/ R 20-36/37/ R 26-36/37/ R 26-36/37/
38-42/43 38-42/43 43-51/53 38-42-52/53 38-40-42/43-52/53 38-40-42/43-52/53
S(2) 23-36/37-45 S(1/2) 26-28-38-45 S(1/2) 26-28-38-45-61 S(2) 26-28-38-45-61 S(1/2) 23-36/37-45-61 S(1/2) 23-36/
37-45-61
TRGS 900 (ppb) 5 5 10 10 10 10
MAK*-value (ppb) 5 5 10 10 - -
Classification* of cancerogenicity (PMDI**)  Category 3 Category 3 Category 3
Sensitisation* Sah Sah Sah Sa Sa Sa
*List of MAK- und BAT-values, DFG 1999
Sah = Hazard of sensitisation for respiratory tract and skin ; Hazard of sensitisation during inhalation
**Classification applies for polymeric MDI (PDMDI) as inhalative dusts as well.
Conclusions:
Diisocyanates are highly hazardous chemicals, which may cause skin irritation, skin sensitisation, respiratory sensitisation and in addition at higher exposure values also acute toxic sings. Therefore an occupational exposure limit of 0.005 ppm has been set.
Executive summary:

The publication of Wolf and Stirn (2000) deals with diisocyanates in general and gives information about the health hazard arising after exposure. Diisocyanates (DI) are reactive compounds. In the presence of an alcohol or a phenol they form polyurethanes, i.e.highly resistant polymers. DI are constituents of high quality paints and varnishes, adhesives and coating agents or of foams used in building and construction. Exposure to DI is irritative for the respiratory tract and the eyes and worsens lung function. A single exposure to high DI concentration or chronic exposure to lower concentrations above the maximum workplace concentration (MAK-value) are capable of causing “isocyanate asthma”, the symptoms of which are closely similar to allergic asthma bronchiale and chronic obstructive bronchitis. Low molecular weight polymers of DI (prepolymers) that have been in use for a long time to replace DI in commercial products can also cause symptoms of asthma.

Moreover the occupational exposure limits are given (0.005 ppm). Indoor use of DI-containing varnishes and paints on large areas may result in an exposure near the MAK-values. Subsequently, the DI-concentration rapidly decreases. There is no evidence that DI are continuously emitted after termination of the polymerisation process. Therefore, an assessment of a short term-exposure limit for indoor use is not reasonable. It is recommended that DI containing products in buildings be applied by professionals. Safety measures that should be taken are effective air circulation, avoidance of skin contact, attention to polymerisation time and prevention of dust when coats of freshly dried paint are ground.

Endpoint:
chronic toxicity: inhalation
Remarks:
other: carcinogenicity study
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
weight of evidence
Justification for type of information:
Please refer to Read-across statement in section 13
Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
Most parameters did not indicate any treatment-related changes. There was a statistically increased mortality in the low- and high-dose females (total 77 percentage deaths were 78% / 70% / 70 % males and 60% / 77% / 74% females (control, low / high dose)
Mortality:
mortality observed, treatment-related
Description (incidence):
Most parameters did not indicate any treatment-related changes. There was a statistically increased mortality in the low- and high-dose females (total 77 percentage deaths were 78% / 70% / 70 % males and 60% / 77% / 74% females (control, low / high dose)
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Mice at the 0.15 ppm level gained less weight. There was also statistically significant reduced weight gain in the 0.15 ppm group which was considered to be exposure-related.
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:
not specified
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):
Major pathological changes occurred in the nasal cavity of both exposure groups. There was a dose-related higher incidence & severity of chronic or necrotic rhinitis: epithelial atrophy, mucous/squamous metaplasia, inflammation, focal destructive rhinitis
Histopathological findings: non-neoplastic:
no effects observed
Description (incidence and severity):
The non-neoplastic lesions of all other tissues correspond to a normal pattern of age-related pathology in this strain of mouse.
Histopathological findings: neoplastic:
no effects observed
Description (incidence and severity):
No treatment-related oncogenic response can be deduced from the incidence and malignancy of the tumours found.
Details on results:
CLINICAL SIGNS AND MORTALITY
Most parameters did not indicate any treatment-related changes in the groups exposed up to and including 0.15 ppm TDI. There was, however, a statistically increased mortality in the low- and high-dose females (total 77 percentage deaths were 78% in controls, 70% low-dose, 70% high-dose males, and 60% in controls, 77% low-dose, 74% high-dose females). The differences were not strictly dose-related and the higher incidence of death rate in the 0.15 ppm group is related to a number of deaths within a 3 week period during the 10th month of the study. Rhinitis in this group was considered to be associated with exposure and was predominantly seen in the animals dying during the study.

BODY WEIGHT AND WEIGHT GAIN
There was also statistically significant reduced weight gain in the 0.15 ppm group which was considered to be exposure-related.

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
Major pathological changes occurred in the nasal cavity of both exposure groups. There was a dose-related higher incidence and severity of either chronic or necrotic rhinitis (epithelial atrophy, mucous and squamous metaplasia, inflammation, focal destructive rhinitis with debris). The highest grade of chronic or necrotic rhinitis was associated with morbidity and mortality in a proportion of mice. Lesions of variable incidence and severity were also seen in the lower respiratory tract (interstitial pneumonitis, catarrhal bronchitis) and in the eyes (keratitis) of some mice, with a higher incidence in the 0.15 ppm group.

HISTOPATHOLOGY: NON-NEOPLASTIC
The non-neoplastic lesions of all other tissues correspond to a normal pattern of age-related pathology in this strain of mouse.

HISTOPATHOLOGY: NEOPLASTIC
No treatment-related oncogenic response can be deduced from the incidence and malignancy of the tumours found.
Dose descriptor:
NOAEC
Effect level:
0.05 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: not specified
Critical effects observed:
not specified

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.

DISCUSSION

Long-term inhalation exposure to TDI vapour resulted in distinct effects in mice. Chronic and necrotic rhinitis, bronchitis and higher mortality (females only) were the predominant effects in the mice. 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. 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 mice exposed for four weeks to TDI at exposure concentrations up to and including 0.15 ppm. The levels of exposure seem to be critical for a proportion of mice. 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 MICE
Synopsis of tumour incidence (malignant tumours in brackets).
  Atmospheric concentrations of TDI (ppm)
  0 0.05 0.15
Sex
Number of animals examined 90 90 90 90 90 89
Ovaries  
granulosa theca cell tumour 0 1 0 1 0 1
tubular adenoma 0 2 0 2 0 0
papillary adenoma 0 1 0 1 0 0
unclassified tumour 0 1 0 0 0 0
Pituitary  
adenoma/microadenoma 0 3 0 0 0 1
Skin  
squamous carcinoma 0 0 ( 1) 0 0 0
fibrosarcoma ( 2) 0 0 0 0 0
Spleen  
haemangioma 1 0 0 1 0 0
haemangiosarcoma 0 ( 1) 0 ( 2) ( 1) (1)
Stomach  
cystadenoma 0 1 1 1 0 0
Subcutaneous tissue  
haemangiosarcoma 0 ( 1) ( 1) 0 0 (1)
Testes  
Leydig cell tumour 1 0 0 0 0 0
Thyroids  
follicular adenoma 1 1 0 0 0 0
follicular carcinoma 0 0 0 ( 1) 0 0
Tongue  
basal cell carcinoma 0 0 0 ( 1) 0 0
squamous papilloma 0 0 1 0 0 0
Uterus  
stromal sarcoma 0 ( 5) 0 ( 3) 0 (2)
stromal polyp 0 9 0 4 0 1
carcinoma 0 ( 1) 0 0 0 0
Miscellaneous  
carcinoma 0 0 0 ( 1) 0 0
sarcoma 0 0 0 ( 1) 0 0
Adrenals  
phaeochromocytoma 0 2 0 0 0 0
Connective tissue  
histiocytic sarcoma 0 0 0 0 ( 1) 0
Kidneys  
tubular carcinoma 0 0 ( 1) 0 ( 1) 0
papillary adenoma 0 0 1 0 0 0
Liver  
adenoma 17 5 14 0 8 1
multicentric/multiple adenoma 4 0 4 0 1 0
carcinoma (23) 0 (19) ( 1) (12) 0
multiple carcinoma ( 1) 0 ( 1) 0 0 0
haemangioma 2 0 0 1 0 0
haemangiosarcoma 0 ( 1) 0 0 0 0
histiocytic sarcoma 0 0 0 0 0 (1)
Lungs  
adenoma/microadenoma 17 22 22 18 16 9
multiple adenoma 0 1 9 2 6 2
carcinoma ( 6) ( 4) ( 4) ( 2) ( 4) 0
Lymph nodes - mesenteric  
haemangioma 0 0 0 0 1 0
Haemopoietic/lymphoreticular system  
leucosis ( 6) ( 1) ( 1) ( 3) 0 0
lymphoma ( 2) (14) (12) (13) ( 5) (6)
Mammary tissue  
mammary carcinoma 0 ( 2) 0 ( 3) 0 0
Nasal turbinates  
papilloma 0 0 0 1 0 0

TABLE II
TDI: LONG-TERM INHALATION STUDY IN MICE
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 90 90 90 90 90 89
Tumour bearers 64 65 43 56 50 22
Animals with malignant tumours 26 21 14 17 19 8
Animals with benign tumours 25 26 20 26 23 12
Animals with both malignant and benign tumours 13 18 9 13 8 2

TABLE III
MICRONUCLEUS TEST ON RATS AND MICE 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
Mice 0.5 ± .2 0.6 ± .2 0.4 ± .2 0.5 ± .2 0.4± .l 0.6 ± .3
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. The results of the study did not reveal a substantial carcinogenic potential of TDI, when administered via inhalation to mice.
Executive summary:

The carcinogenicity of the test material was investigated in mice by Loeser et al (1983). The test was conducted similar to OECD TG451. Groups of male and female mice (30 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. At termination of the study (at week 104) most parameters did not indicate any treatment-related changes. There was a statistically increased mortality in the low- and high-dose females (total 77 percentage deaths were 78% / 70% / 70 % males and 60% / 77% / 74% females (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.

Endpoint:
repeated dose toxicity: inhalation, other
Remarks:
carcinogen profile
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
weight of evidence
Justification for type of information:
Please refer to Read-across statement in section 13
Dose descriptor:
other: OEL (ACGIH 2008 TLV)
Effect level:
0.005 ppm
Based on:
test mat.
Sex:
not specified
Basis for effect level:
other: based on sensitization potential
Dose descriptor:
other: OEL (Canada Labour Code)
Effect level:
0.005 ppm
Based on:
test mat.
Sex:
not specified
Basis for effect level:
other: based on sensitization potential
Critical effects observed:
not specified
Regulations and Guidelines
Occupational Exposure Limits (OEL)
CANADIAN JURISDICTIONS OEL (ppm)
Canada Labour Code 0.005 [sen]
0.02 [stel]
NIC: 0.001 [sk, sen]
0.003 [stel]
BC 0.005 [sk, sen]
0.01 [c]
AB 0.005
0.002 [c]
SK 0.005 [sen]
0.02 [stel]
MB, NL, PE, NS 0.005 [sen]
0.02 [stel]
NIC: 0.001 [sk, sen]
0.003 [stel]
ON 0.005
0.02 [c]
QC 0.005 [sen, EM]
0.02 [stel]
NB 0.005
0.02 [stel]
NT, NU and YT* 0.02 [c]
OTHER JURISDICTIONS OEL(ppm)
ACGIH 2008 TLV 0.005 [sen]
0.02 [stel]
NIC: 0.001 [sk, sen]
0.003 [stel]
SCOEL None listed
Sweden LLV 0.002 [M, sen]
0.005 [c]
German MAK Not enough data
*Yukon's Occupational Health Regulation is scheduled for review in 2011-2012. The Yukon Workers' Compensation Health & Safety Board reports that current ACGIH standards are enforced in the meantime.
ppm = parts per million
sen = potential for sensitization
stel = short term exposure limit (15 min. maximum)
NIC = Notice of intended change (refers to newly proposed regulations)
sk = easily absorbed through the skin
c = ceiling (not to be exceeded at any time)
M = Medical surveillance required
EM = exposure must be reduced to the minimum

Occupational Exposures

Inhalation and dermal contact are the most common routes of occupational exposure.

Exposure can occur during all phases of TDI’s manufacture and use.

The main occupations with the potential for exposure to TDI include adhesive lacquer, rubber, wire coating, and diisocyanate resin workers; insulators, organic chemical synthesizers, paint and urethane foam sprayers, polyurethane makers, ship builders, and textile processors.

Workers who spray foam insulation, which usually takes place in confined spaces, have the highest exposure.

otential for exposure exists from processes involving heating (welding, soldering, or hot-wire cutting) polyurethane products.

Many provinces collect samples of workplace exposures as part of their regulatory practices.

Environmental Exposures

The most common route of environmental exposure is inhalation; dermal exposure via some consumer products is also possible.

In Canada, most industrial releases of TDI are into the air. Long range atmospheric transport is unlikely due to the short half-life of TDI in the environment (~2 days).

Most Canadian releases of TDI to the environment occur in Ontario.

Potential sources of TDI exposure to the general Canadian population include.

  • industrial releases during urethane foam manufacture and processing. (The estimated annual average concentration of TDI in Canada in close proximity to a foam manufacturing facility is 1.06μg/m³.)
  • industrial releases from the manufacture, use ,or disposal of other TDI-based products;
  • from the use of consumer products such as polyurethane foams, varnishes, adhesives, and sealants.
Conclusions:
This publication deals with the hazardous potential of toluene diisocyanates. The toxicity of TDI has been recognized for many years. Exposure to high levels of TDI causes severe irritation of the skin, eyes, and nose, as well as nervous system effects. It is a potent skin and respiratory sensitizer and a well-known cause of occupational asthma. TDI can also cause hypersensitivity pneumonitis and chronic bronchitis. CAREX Canada ranks toluene diisocyanates as Group A (immediate high priority) for occupational settings and as Group B (possible high priority) for environmental settings. Prioritization was based on the carcinogenicity and other toxic properties of the substance, the prevalence of exposure in Canada, and the feasibility of assessing exposure. An OEL of 0.005 ppm for sensitization and an OEL of 0.02 ppm for short term exposure are given.
Executive summary:

This publicly available document deals with the hazardous characteristics of toluene disiocyanates (Carex Canada, 1999). Toluene diisocyanates (TDI) are colourless to pale yellow liquids, solids, or crystals with a distinctive pungent odour. Toluene diisocyanates are highly reactive compounds widely used in the manufacturing of polyurethane foams and coatings. TDI is typically available as a mixture of 80% 2,4-TDI isomer and 20% 2,6-TDI isomer, or sometimes as a 65-35% mix. IARC classifies toluene diisocyanates as Group 2B (possibly carcinogenic to humans), based on sufficient evidence in animals. Ingestion exposure causes liver and blood-related cancers in rats, and tumours of the liver, pancreas, and mammary glands in mice.

The few available studies in occupationally-exposed people have not found a strong association or a consistent pattern.

The NTP’s 11th Report on Carcinogens classifies toluene diisocyanates as “reasonably anticipated to be a human carcinogen,” based on

evidence in experimental animals. The toxicity of TDI has been recognized for many years. Exposure to high levels of TDI causes severe irritation of the skin, eyes, and nose, as well as nervous system effects. It is a potent skin and respiratory sensitizer and a well-known cause of occupational asthma. TDI can also cause hypersensitivity pneumonitis and chronic bronchitis.

CAREX Canada ranks toluene diisocyanates as Group A (immediate high priority) for occupational settings and as Group B (possible high priority) for environmental settings and an OEL of 0.005 ppm for sensitization and an OEL of 0.02 ppm for short term exposure are given.

Endpoint:
repeated dose toxicity: inhalation, other
Remarks:
This publication describes the hazard assessment and the safety precautions of workplaces, where isocyanates are present.
Type of information:
other: This publication describes the hazard assessment and the safety precautions of workplaces, where isocyanates are present.
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: well documented hazard assessment and safety precautions of isocyanates
Qualifier:
no guideline followed
Principles of method if other than guideline:
This TRGS describes the hazard assessment and safety precautions of workplaces, where isocyanates are present. Besides, a method of determination and exposure assessment is given. This method may used during operations including isocyanates. Generally this means operations such as formulation, manufacturing and application of polyurethanes (PU, PUR).
Furthermore an assessment of possible hazards is described regarding the whole exposure to isocyanates.
GLP compliance:
not specified
Species:
other: not applicable
Strain:
other: not applicable
Details on test animals and environmental conditions:
No details given
Route of administration:
inhalation
Analytical verification of doses or concentrations:
not specified
Details on analytical verification of doses or concentrations:
Different analytical procedures for the determination of isocyanates are reported.
(1) Sampling using derivatisation
During sampling isocyanates are derivated with a secondary amine which includes chromophores. Using high-pressure liquid chromatography (HPLC) the isocyanates are determined. Different compounds can be used for derivatisation.
(2) Total Aerosol Mass Method (TAMM)
The TAMM describes a method to determine polymere isocyanates during applications such as spray painting. It is based on the measurement of dust and can only be used if the determined dust concentration do not exceed the limit of quantification for the used method of dust sampling.
(3) Total-NCO (TRIG)
In order to determine the total NCO-content, different chromatograms of standards and samples are considered. By comparison of derivated materials with known concentrations of NCO to the ones of the air samples, the quantification of polymer isocyanates as Total-NCO can be accomplished.
(4) Direct measurement
Paper tape monitors react with NCO-moieties to a coloured compound which can be determined photometrically. Thus the concentration can be identified.
Ion mobilisation spectrometers (IMS) detect isocyanates by an ionisation. Afterwards the charged ions pass an electrical field and can be determined by their characteristic time of flight.
Dose descriptor:
other: OEL (Arbeitsplatzgrenzwerte)
Effect level:
0.005 ppm
Based on:
test mat.
Sex:
not specified
Basis for effect level:
other: This value is valid for 2,4-TDI
Dose descriptor:
other: OEL (Arbeitsplatzgrenzwerte)
Effect level:
0.005 ppm
Based on:
test mat.
Sex:
not specified
Basis for effect level:
other: This value is valid for 2,6-TDI
Critical effects observed:
not specified

Isocyanates have acute as well as chronic effects mainly to the respiratory system. Cough, dyspnoea, coryza and conjunctivitis are described as acute effects which can appear delayed and lethal (pulmonary oedema). Obstructive respiratory diseases and particular immune responses (production of antibodies) can cause isocyanate asthma and less frequently allergic contact dermatitis.

According to determined test results such effects predominately occur on a regular basis of exposure which exceeds the maximum workplace concentration. In addition particular circumstances such as accidents or lack of personal protective equipment, which lead to high exposures to lung and skin, can cause such effects as well. This is given by inappropriate use of adhesives, foams and coatings.

However, diseases were reported although an exposure could not be detected technically. Besides effects in sensitized humans can occur in spite of a concentration below the maximum workplace concentration. Some isocyanates are suspected to cause carcinogenic and mutagenic effects. Data of classification and labelling are shown in the following table.

Classification, labelling and maximum workplace concentrations of several isocyanates
References:
Classification: Regulation (EG) Nr. 1272/2008 of the European Parliament and the European Council (2008-12-16) of classification, labelling and packaging of substances and mixtures, annex VI, table 3.2 (http://eur-lex.europa.eu/JOHtml.do?uri=OJ:L:2008:353:SOM:DE:HTML)
Maximum workplace concentrations: TRGS 900, Issue: January 2006; recent amendment: GMBl N 12-14 p. 254 (27.3.2009)
Identity (EG-number; CAS-number) Classification Maximum workplace concentrations
mg/m3 ml/rr)3 (ppm) peak limit remarks
Aromatic Diisocyanates
Diphenylmethan-4,4'-diisocyanate (4,4'-MDI) 202-966-0 101-68-8 Carc. Cat. 3; R40* Xn; R20-R48/20 Xi; R36/37/38 R42/43 0,05   1;=2=(i) 11, 12, Sa
Diphenylmethan-2,4'-diisocyanate (2,4'-MDI) 227-534-9 5873-54-1 Carc. Cat. 3; R40* Xn; R20-R48/20 Xi; R36/37/38 R42/43 0,05   1;=2=(i) 11, 12, Sa
Diphenylmethan-2,2'-diisocyanate (2,2'-MDI) 219-799-4 2536-05-2 Carc. Cat. 3; R40* Xn; R20-R48/20 Xi; R36/37/38 R42/43 0,05   1;=2=(i) 11, 12, Sa
Diphenylmethan-diisocyanate, mixture of isomers (MDI) 247-714-0 26447-40-5 Carc. Cat. 3; R40* Xn; R20-R48/20 Xi; R36/37/38 R42/43       11,12, Sa (It must apply the MAKs of the isomers)
Diphenylmethan-diisocyanate, isomers and homologues (p-MDI (or MDI) 9016-87-9 notice classification of manufacturer (respirable fraction: Carc. Cat 3*)       It must apply the MAKs of the isomers (4,4'-MDI, 2,4'-MDI, 2,2'-MDI); considering the homologues the EBW (manufacturer instruction) should be used
Naphthylen-1,5-diisocyanate (NDI) 221-641-4 3173-72-6 Xn; R20 Xi; R36/37/38 R42 R52-53 0,05   1;=2=(i) AGS, 11, 12, Sa
2,4-Diisocyanattoluole (2,4-TDI) 209-544-5 584-84-9 Carc. Cat. 3; R40 T+; R26 Xi; R36/37/38 R42/43 R52-53 0,035 0,005 1;=4=(l) AGS, 12, Sa
2,6-Diisocyanattoluole (2,6-TDI) 202-039-0 91-08-7 Carc. Cat. 3; R40 T+; R26 Xi; R36/37/38 R42/43 R52-53 0,035 0,005 1;=4=(i) AGS, 12, Sa
m-Diisocyanattoluole (1,3-) (2,4-/2,6-TDI) (m-TDI) 247-722-4 26471-62-5 Carc. Cat. 3; R40 T+; R26 Xi; R36/37/38 R42/43 R52-53       To classify the mixture of isomers (2,4-/2,6-TDI) , the MAKs of the isomers (2,4-TDI and 2,6-TDI) are considered.
Aliphatic Diisocyanates
Hexamethylen-1,6-diisocyanate (HDI) 212-485-8 822-06-0 T; R23 Xi; R36/37/38 R42/43 0,035 0,005 1;=2=(i) DFG, 12, Sa
2,2,4-Trimethylhexa-methylen-1,6-diisocyanate T; R23 Xi; R36/37/38       consider manufacturer instruction
241-001-8 (TMDI) 16938-22-0 R42        
2,4,4-Trimethylhexa-methylen-1,6-diisocyanate 239-714-4 (TMDI) 15646-96-5 T; R23 Xi; R36/37/38 R42       consider manufacturer instruction
1,3-Tetramethylxylylen-diisocyanate (m-TMXDI) 220-474-4 2778-42-9  consider manufacturer instruction       consider manufacturer instruction
1,4-Tetramethylxylylen-diisocyanate (p-TMXDI) 220-473-9 2778-41-8  consider manufacturer instruction       consider manufacturer instruction
Cycloaliphatic Diisocyanates
3-Isocyanatmethyl-3,5,5- trimethylcyclohexyl- isocyanate (Isophorondiisocyanate) (IPDI) 223-861-6 4098-71-9 T; R23 Xi; R36/37/38 R42/43 N; R51-53 0,046 0,005 1;=2=(i) DFG, 12, Sa
Dicyclohexylmethan-4,4'-diisocyanate (H12MDI) 225-863-2 (PICM) 5124-30-1 T; R23 Xi; R36/37/38 R42/43 0,054     (TRGS 900) NL, H, 29, 36
2,5-(und 2,6-)Bis(isocya natomethyl)-bicyclo[2.2.1] heptaen (Norbornandiisocyanate) (NBDI) 411-280-2 T+; R26 Xn; R22 C; R34 R42/43 R52-53 0,045 0,005   AGS
Monoisocyanates
Methylisocyanate (MIC) 210-866-3 624-83-9 F+; R12 Repr. Cat. 3; R63 T+; R26 T; R24/25 R42/43 Xi; R37/38-41 0,024 0,01   DFG, H, 12
Phenylisocyanate (PhI) 203-137-6 103-71-9  consider manufacturer instruction 0,05 0,01   AGS, 12, Sa
4-Toluensulfonylisocyanate 223-810-8 4083-64-1 R14 Xi; R36/37/38 R42       consider manufacturer instruction

Remarks TRGS 900:

11 (29): Sum of vapour und aerosols.

12 (36): Generally the maximum workplace concentration applies to momomers.

For evaluation of oligomers or polymers see TRGS 430 „Isocyanate“.

H: (resorption through skin),

Sa: sensitisation of respiratory system

* Classification according to first Amendment of Regulation (EG) Nr. 1272/2008 (in preparation)

Conclusions:
Isocyanates have acute as well as chronic effects mainly to the respiratory system. Cough, dyspnoea, coryza and conjunctivitis are described as acute effects which can appear delayed and lethal (pulmonary oedema). Obstructive respiratory diseases and particular immune responses (production of antibodies) can cause isocyanate asthma and less frequently allergic contact dermatitis. According to determined test results such effects predominately occur on a regular basis of exposure which exceeds the maximum workplace concentration of 0.005 ppm.
Executive summary:

This TRGS describes the hazard assessment and safety precautions of workplaces, where isocyanates are present (TRGS, 2009). Besides, a method of determination and exposure assessment is given. This method may used during operations including isocyanates. Generally this means operations such as formulation and application of polyurethanes (PU, PUR). Furthermore an assessment of possible hazards is described regarding the whole exposure to isocyanates. Isocyanates have acute as well as chronic effects mainly to the respiratory system. Cough, dyspnoea, coryza and conjunctivitis are described as acute effects which can appear delayed and lethal (pulmonary oedema). Obstructive respiratory diseases and particular immune responses (production of antibodies) can cause isocyanate asthma and less frequently allergic contact dermatitis.

According to determined test results such effects predominately occur on a regular basis of exposure which exceeds the maximum workplace concentration of 0.005 ppm. In addition particular circumstances such as accidents or lack of personal protective equipment, which lead to high exposures to lung and skin, can cause such effects as well. This is given by inappropriate use of adhesives, foams and coatings.

However, diseases were reported although an exposure could not be detected technically. Besides effects in sensitized humans can occur in spite of a concentration below the maximum workplace concentration.

Isocyanates enter the human body through the skin but predominantly via the respiratory tract. For this reason, both exposure routes are considered regarding operating conditions of machinery and equipment. This includes starting, testing, cleaning and maintenance.

Endpoint:
chronic toxicity: inhalation
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
weight of evidence
Justification for type of information:
Please refer to Read-across statement in section 13
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
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:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
Immunological findings:
not specified
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Neuropathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
effects observed, treatment-related
Dose descriptor:
NOAEC
Effect level:
0.2 mg/m³ air (nominal)
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Dose descriptor:
NOAEC
Effect level:
0.19 mg/m³ air (analytical)
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Dose descriptor:
LOAEC
Effect level:
1 mg/m³ air (nominal)
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Dose descriptor:
LOAEC
Effect level:
0.98 mg/m³ air (analytical)
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Critical effects observed:
not specified

Mortality incidences in males were comparable in all groups. Female rats showed negatively concentration-related mortality incidences. The number of animals with palpable masses did not differ between test and control animals. No treatment-related differences in body weights were observed between control and test groups.

Hematological examination of rats at day 357-358 revealed no exposure-related differences between the groups. Biochemical examination performed on days 360, 366 and/or 367 was essentially negative. No alterations were observed from parameters measured in urine of rats exposed to polymeric MDI aerosol for 360 days.

Lung weights were statistically significantly increased in both males and females exposed to 6.0 mg/m³ for 12 or 24 months as summarized in the following table 1:

Table 1: Mean absolute lung weights and lung-to-body weight ratios in rats exposed by inhalation to polymeric MDI aerosol for 1 year (satellite groups) or for up to 2 years (main groups)

Polymeric MDI (mg/m3)

Satellite groups(a)

Main groups(b)

Absolute (g)

Relative (g/kg)

Absolute (g)

Relative (g/kg)

Males

0

0.2

1.0

6.0

2.30 ± 0.15

2.32 ± 0.09

2.44 ± 0.10

2.60 ± 0.06

4.29 ± 0.16

4.48 ± 0.22

4.48 ± 0.16

5.06 ± 0.08**

2.90 ± 0.06

2.88 ± 0.10

2.88 ± 0.08

3.28 ± 0.07**

5.04 ± 0.14

5.00 ± 0.15

5.19 ± 0.24

5.80 ± 0.16**

Females

0

0.2

1.0

6.0

1.67 ± 0.07

1.66 ± 0.05

1.69 ± 0.06

1.93 ± 0.09*

5.66 ± 0.29

5.63 ± 0.15

5.61 ± 0.21

6.51 ± 0.22*

2.10 ± 0.06

2.09 ± 0.04

2.06 ± 0.04

2.41 ± 0.05**

6.14 ± 0.28

5.87 ± 0.09

5.68 ± 0.11

6.68 ± 0.17

(a) Number of lungs weighed/sex/group was 10
(b) Number of lungs weighed/sex/group varied from 35 to 50

* p<0.05; ** p<0.01

No treatment-related gross changes were found in animals exposed for 12 months. Gross examination of animals exposed for 24 months revealed increased incidence of lungs with spotted surface and/or discoloured appearance in male rats exposed to 6.0 mg/m3.

Histopathology (main groups exposed over 2 years):

Nose: increased incidence of rats with a higher degree of basal cell hyperplasia frequently accompanied by hyperplasia of Bowman's glands in the olfactory epithelium in the nose at levels of 1.0 and 6.0 mg/m³. At 6.0 mg/m³ basal cell hyperplasia occurred in 32/60 males and 49/60 females against 14/60 and 4/60 for the corresponding controls.

Lungs: incidences of non-neoplastic findings and tumors are summarized in the following table 2:

Table 2: Number of rats with non-neoplastic findings and tumors in lungs after 2-year exposure to polymeric MDI (main groups)

 Polymeric MDI (mg/m3)    0  0.2  1.0  6.0

Animal number

M 60   60 60 60  

60  60 60  60

Surviving animals

M 38 38 42 36
F 41 42 48 50

- Macrophages with yellow pigment

M 0 3 21** 60**
F 0 1 23** 59** 

- Localized fibrosis

M 1 0 9* 44**
0 0 4 48**

- Alveolar duct epithelialization 

M 1 0 8* 54**
F 0 0 8* 57*

- Localized alveolar bronchiolization

1 12** 
  F 14** 

- Mineralized deposits in the bronchial and alveolar region 

0 1 13** 
  24** 

- Pneumonitis 

13 13   17 28 
  F 3

- Adenoma 

0 6* 
 

- Adenocarcinoma 

  F

0

0

* p<0.05; ** p<0.01

Mediastinal lymph nodes: increased incidence of rats with an accumulation of macrophages with yellow pigment at levels of 1.0 and 6.0 mg/m³. At 6.0 mg/m³ this finding occurred in 50/60 males and 43/60 females against 0/60 for the corresponding controls.

Other organs: the incidence and distribution of other tumour types was not affected by treatment.

Histopathology (satellite groups exposed over 1 year):

Rats killed after 1 year of exposure had treatment-related histopathological changes in the nasal cavity, lungs, and mediastinal lymph nodes starting at 1.0 mg/m³, but to a lower degree of severity compared to animals exposed over 2 years. There was no microscopic evidence of lung tumors or any other tumors following exposure to polymeric MDI for 1 year.

Conclusions:
It was concluded that in the present study, the "no-observed-adverse-effect level" of polymeric MDI was 0.2 mg/m³, and that chronic exposure to polymeric MDI at a level of 6.0 mg/m³ was related to the occurrence of pulmonary tumors. It was also concluded that exposure to polymeric MDI at concentrations not leading to recurrent lung tissue damage will not produce pulmonary tumors.
Executive summary:

In a combined chronic toxicity and carcinogenicity study rats were exposed for 6 hours/day, 5 days/week for 1 (satellite groups) or 2 years (main groups) to polymeric MDI aerosol concentrations of 0, 0.2, 1.0 or 6.0 mg/m3.

There was no adverse effect on general health, survival, body weight, or hematological or clinical chemistry parameters. Lung weights were increased in both males and females exposed to 6.0mg polymeric MDI/ m³ for 12 or 24 months. Gross examination at autopsy of males exposed to 6.0mg polymeric MDI/ m³ for 12 or 24 months revealed an increased incidence of spotted and discolored lungs

Histopathology of the organs/tissues investigated showed that exposure to 6.0 mg/m³ over 2 years was related to the occurence of pulmonary tumors in males (6 adenomas and 1 adenocarcinoma) and females (2 adenomas). No lung tumors were found in the lower concentration groups and in the control group. The incidence and distribution of other types of tumors were not influenced by polymeric MDI.

In this 2-year rat study the NOAEC was 0.2 mg/m³ for the repeated dose toxicity of polymeric MDI. The LOAEC was set on 1.0 mg/m³.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEC
0.058 mg/m³
Study duration:
chronic
Species:
rat

Additional information

Repeated dose toxicity oral:

Gordon, 1978 – rats

A study was conducted in Fischer 344 rats to provide information on the possible health hazards likely to arise from repeated treatment with the test article toluene diisocyanate (Gordon, 1978). The test material was administered once daily via oral gavage, 5 days a week, for 13 weeks. The test material was solved in corn oil and administered to six groups, each of ten male and ten female Fischer 344 rats, at dietary concentrations of 15, 30, 60, 120 and 240 mg/kg/day. A further group of ten males and ten females was exposed to vehicle only to serve as a control. Clinical signs and bodyweight development were monitored during the study. All animals were subjected to gross necropsy examination and a comprehensive histopathological evaluation of organs and tissues was performed. However, the study is problematic, as the stability of the test item under the acidic conditions in the stomach is not likely to be guaranteed. Therefore the results were considered to be not reliable (Klimisch 3).

There were mortalities and clinically observable signs of toxicity in the test animals during the study period. Of the males treated with 60 mg/kg bw 1 animal died. Additionally 2 males died in the 120 mg/kg bw group and 1 died in the 240 mg/kg bw group. One intercurrent death was noted in females treated at 240 mg/kg bw, which was judged to be related to treatment. 1 of 10 males (60 and 120 mg/kg bw) and 3 males (240 mg/kg bw) showed respiratory noises. A slight decrease in body weights of males treated with 60 mg/kg bw and above was evident (down to 89.7 % of the controls in the 240 mg/kg bw dose group) and in females treated with 120 mg/kg bw and above . Toxicological significant effects (respiratory noises) noted were detected in male animals treated with 60, 120 and 240 mg/kg bw. Histopathological findings were detected in males treated at 60 mg/kg bw and above and in females treated at 120 mg/kg bw and above a dose-related appearance of accumulated mucoid material in the pulmonary bronchioles. Thus, in this rat subchronic repeated dose toxicity study, the No-Observable-Adverse-Effect Level (NOAEL) of the test article toluene diisocyanate for males is 30 mg/kg/day and for females 60 mg/kg/day. The NOAEL of 30 mg/kg bw was used for preliminary derivation of DNELs, but in the following DNELs were derived based on the available OELs for TDI.

Gordon, 1978 - mice

The study was conducted in B6C3F1 mice to provide information on the possible health hazards likely to arise from repeated treatment with the test article toluene diisocyanate (Gordon, 1978). The test material was administered once daily via oral gavage, 5 days a week, for 13 weeks. The test material was solved in corn oil and administered to six groups, each of ten male and ten female B6C3F1 mice, at dietary concentrations of 15, 30, 60, 120 and 240 mg/kg/day. A further group of ten males and ten females was exposed to vehicle only to serve as a control. Clinical signs, bodyweight development and food consumption were monitored during the study. All animals were subjected to gross necropsy examination and a comprehensive histopathological evaluation of organs and tissues was performed. However, the study is problematic, as the stability of the test item under the acidic conditions in the stomach is not likely to be guaranteed. Therefore the results were considered to bei not reliable (Klimisch 3). No effects on clinical signs, food consumption, body weights, necropsy or tissue histopathology were noted. There were mortalities but no clinically observable signs of toxicity in the test animals during the study period. Of the females treated with 240 mg/kg bw 2 animals died, which were judged as intercurrent. Additionally 1 female died in the 120 mg/kg bw group. Thus, in this mice subchronic repeat dose toxicity study, the No-Observable-Adverse-Effect Level (NOAEL) of the test article toluene diisocyanate for males is 240 mg/kg/day and for females 60 mg/kg/day.

Ministry of Health Labour & Welfare - rats

The Ministry of Health Labour & Welfare performed a study to provide information on the possible health hazards likely to arise from repeated treatment with the test article toluene disocyanate (Ministry of Health Labour & Welfare, Japan, 2001). The test material was administered by gavage to four groups, each of five male and five female Sprague-Dawley Crl:CD(SD) strain rats, for twenty-eight consecutive days, at nominal dose levels of 30, 100 and 300 mg/kg/day. A control group of five males and five females was dosed with vehicle alone (Corn oil). Clinical signs and bodyweight development were monitored during the study.Blood and urinalysis were evaluated. All animals were subjected to a gross necropsy examination and histopathological evaluation of organs and tissues was performed. However, the study is problematic, as the stability of the test item under the acidic conditions in the stomach is not likely to be guaranteed. Therefore the results were considered to be not reliable (Klimisch 3). Oral administration of the test material to rats did not result in mortalities. Clinical signs (salivation) during the administration period were noted in both sexes at 100 and 300 mg/kg bw. Reduced body weight development was noted in males at 100 and 300 mg/kg bw. However, recovery was seen during the recovery period. Repeated oral dosing of rats with toluene diisocyanate over 28 days led to histopathological changes in lungs (males at >=100 mg/kg; females at >= 30 mg/kg), trachea (both sexes at >= 30 mg/kg), stomach (both sexes at 300 mg/kg), liver (both sexes at 300 mg/kg) and spleen (both sexes at 300 mg/kg). After a 14 -day recovery period all changes in lungs, trachea, stomach, small intestine and liver were considered to be reversible. The NOEL for the oral subacute rat study was considered to be less than 30 mg/kg/day for males and females. The LOAEL is 30 mg/kg/day based on histopathological changes in lungs (females only) and trachea (both sexes).

Repeated dose toxicity inhalation

Loeser, 1983 - rats

The carcinogenicity of toluene-diisocyanate (TDI) 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 (correspomds to 0.05 (correspomds to 0.58 mg/m³ for TRIDI)and 0.15 ppm (corresponds to 1.75 mg/m³ for TRIDI) 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 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.

Loeser, 1983 – mice

The carcinogenicity of the toluene-diisocyanate was investigated in mice by Loeser et al (1983). The test was conducted similar to OECD TG451. Groups of male and female mice (30 animals per sex 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. At termination of the study (at week 104) most parameters did not indicate any treatment-related changes. There was a statistically increased mortality in the low- and high-dose females (total 77 percentage deaths were 78% / 70% / 70 % males and 60% / 77% / 74% females (control / low / high dose). Distinct effects occured 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.

Wolf and Stirn, 2000

The publication of Wolff and Stirn (2000) deals with diisocyanates in general and gives information about the health hazard arising after exposure. Diisocyanates (DI) are reactive compounds. In the presence of an alcohol or a phenol they form polyurethanes, i.e.highly resistant polymers. DI are constituents of high quality paints and varnishes, adhesives and coating agents or of foams used in building and construction. Exposure to DI is irritative for the respiratory tract and the eyes and worsens lung function. A single exposure to high DI concentration or chronic exposure to lower concentrations above the maximum workplace concentration (MAK-value) are capable of causing “isocyanate asthma”, the symptoms of which are closely similar to allergic asthma bronchiale and chronic obstructive bronchitis. Low molecular weight polymers of DI (prepolymers) that have been in use for a long time to replace DI in commercial products can also cause symptoms of asthma. Moreover the occupational exposure limits are given (0.005 ppm). Indoor use of DI-containing varnishes and paints on large areas may result in an exposure near the MAK-values. Subsequently, the DI-concentration rapidly decreases. There is no evidence that DI are continuously emitted after termination of the polymerisation process. Therefore, an assessment of a short-term exposure limit for indoor use is not reasonable. It is recommended that DI containing products in buildings be applied by professionals. Safety measures that should be taken are effective air circulation, avoidance of skin contact, attention to polymerisation time and prevention of dust when coats of freshly dried paint are ground.

CAREX Canada, 1999

The publicly available document of CAREX Canada deals with the hazardous characteristics of toluene diisocyanates (Carex Canada, 1999). Toluene diisocyanates (TDI) are colourless to pale yellow liquids, solids, or crystals with a distinctive pungent odour. Toluene diisocyanates are highly reactive compounds widely used in the manufacturing of polyurethane foams and coatings. TDI is typically available as a mixture of 80% 2,4-TDI isomer and 20% 2,6-TDI isomer, or sometimes as a 65-35% mix. IARC classifies toluene diisocyanates as Group 2B (possibly carcinogenic to humans), based on sufficient evidence in animals. Ingestion exposure causes liver and blood-related cancers in rats, and tumours of the liver, pancreas, and mammary glands in mice. The few available studies in occupationally-exposed people have not found a strong association or a consistent pattern. CAREX Canada ranks toluene diisocyanates as Group A (immediate high priority) for occupational settings and as Group B (possible high priority) for environmental settings and an OEL of 0.005 ppm for sensibilisation and an OEL of 0.02 ppm for short-term exposure are given.

The NTP’s 11th Report on Carcinogens classifies toluene diisocyanates as “reasonably anticipated to be a human carcinogen,” based on evidence in experimental animals. The toxicity of TDI has been recognized for many years. Exposure to high levels of TDI causes severe irritation of the skin, eyes, and nose, as well as nervous system effects. It is a potent skin and respiratory sensitizer and a well-known cause of occupational asthma. TDI can also cause hypersensitivity pneumonitis and chronic bronchitis.

BAuA, 2009 - TRGS

The TRGS describes the hazard assessment and safety precautions of workplaces, where isocyanates are present (BAuA, 2009). Besides, a method of determination and exposure assessment is given. This method may used during operations including isocyanates. Generally this means operations such as manufacture, formulation and application of polyurethanes (PU, PUR). Furthermore an assessment of possible hazards is described regarding the whole exposure to isocyanates. Isocyanates have acute as well as chronic effects mainly to the respiratory system. Cough, dyspnoea, coryza and conjunctivitis are described as acute effects which can appear delayed and lethal (pulmonary oedema). Obstructive respiratory diseases and particular immune responses (production of antibodies) can cause isocyanate asthma and less frequently allergic contact dermatitis.

According to determined test results such effects predominately occur on a regular basis of exposure which exceeds the maximum workplace concentration of 0.005 ppm. In addition particular circumstances such as accidents or lack of personal protective equipment, which lead to high exposures to lung and skin, can cause such effects as well. This is given by inappropriate use of adhesives, foams and coatings.

However, diseases were reported although an exposure could not be detected technically. Besides, effects in sensitized humans can occur in spite of a concentration below the maximum workplace concentration.

Isocyanates enter the human body through the skin but predominantly via the respiratory tract. For this reason, both exposure routes are considered regarding operating conditions of machinery and equipment. This includes starting, testing, cleaning and maintenance.

Conclusion

Considering oral exposure, the rat subchronic repeated dose toxicity study by Gordon (1978) set the No-Observable-Adverse-Effect Level (NOAEL) of the test article toluene diisocyanate to 30 mg/kg/day. As the results revealted the respiratory system to be the primary target of these chemicals. However inhalation is the most relevant route of exposure for humans. Thus studies on inhalation exposure are considered in detail.

The chronic inhalation study in rats (Loeser et al., 1983) was taken as key study for the chemical safety assessment. Although the exposure levels used by Loeser et al. may not have been optimal doses to detect all systemic effects (Screening Assessment for TDIs, 2008; NTP, 1986), they are the lowest doses tested which are known for the read-across substance toluene diisocyanate. The dose level of 0.15 ppm (1.75 mg/m³ for TRIDI) can be considered as a NOAEL since no treatment related effects were observed in any of the treated animals at this dose level. This NOAEL can serve as the starting point for DNEL derivation and should cover the risk of carcinogenicity arising after oral route of exposure, as well as the risk for respiratory hypersensitivity.

Additionally there are other sources for toxicity and safety exposure levels as described below.

The publication of Wolff and Stirn (2000) describes an occupational exposure limit (OEL) of 0.005 ppm for diisocyanates (DIs). An assessment of a short-term exposure limit for indoor use of diisocyanates is regarded as not reasonable.

CAREX Canada (1999) gives an OEL of 0.005 ppm for sensibilisation and an OEL of 0.02 ppm for short-term exposure regarding toluene diisocyanates (TDIs). Furthermore TDIs are categorised as Group A (immediate high priority) for occupational settings and as Group B (possible high priority) for environmental settings.

According to the TRGS isocyanates have acute as well as chronic effects mainly to the respiratory system. Such effects predominately occur on a regular basis of exposure which exceeds the maximum workplace concentration of 0.005 ppm.

Hoymann, 1995

In a long-term inhalation study over a maximum of 24 months including satellite groups with 3, 12, and 20-month exposure, the chronic toxicity and carcinogenicity of monomeric methylene diphenyl diisocyanate (MDI) were investigated. Female Wistar rats were exposed in 6 m³ inhalation chambers for 18 hours/day, 5 days/week to 0.23, 0.70 and 2.05 mg/m³ MDI in aerosol form, a control group was kept in clean air. Essentially, a dose-dependent impairment of the lung function in the sense of an obstructive-restrictive malfunction with diffusion disorder, increased lung weights, an inflammatory reaction with increased appearance of lymphocytes (but not of granulocytes) in the lung in the high dose group as a sign of specific stimulation of the immune system by MDI, an intermediately retarded lung clearance in the high dose group as well as dose-dependent interstitial and peribronchiolar fibrosis, alveolar bronchiolisations and a proliferation of the alveolar epithelium, which was classified as preneoplastic, as well as a bronchiolo-alveolar adenoma were ascertained. The LOAEC for the female rat was 0.23 mg/m³ after long-term inhalation of 4,4'-MDI aerosols.

Remark: In a chronic rat study with polymeric MDI the NOAEC was 0.2 mg/m³ after aerosol exposure over 2 years (6 hours/day, 5 days/week) (Reuzel et al. (1994), Fund. Appl. Toxicol. 22: 195-210). A comparison of the both chronic rat studies with 4,4'-MDI and polymeric MDI has shown very good consistency across the studies with respect to gradation of inhaled dose and the observed histopathological changes. In this review it turned out that a daily 18 hr-exposure of 0.23 mg/m³ 4,4'-MDI corresponds approximately to a daily 6 hr-exposure of 1 mg/m³ polymeric MDI (Feron et al. (2001), Arch. Toxicol. 75: 159-175).

Reutzel et al, 1994

In a combined chronic toxicity and carcinogenicity study rats were exposed for 6 hours/day, 5 days/week for 1 (satellite groups) or 2 years (main groups) to polymeric MDI aerosol concentrations of 0, 0.2, 1.0 or 6.0 mg/m3.

There was no adverse effect on general health, survival, body weight, or hematological or clinical chemistry parameters. Lung weights were increased in both males and females exposed to 6.0mg polymeric MDI/ m³ for 12 or 24 months. Gross examination at autopsy of males exposed to 6.0mg polymeric MDI/ m³for 12 or 24 months revealed an increased incidence of spotted and discolored lungs

Histopathology of the organs/tissues investigated showed that exposure to 6.0 mg/m³ over 2 years was related to the occurence of pulmonary tumors in males (6 adenomas and 1 adenocarcinoma) and females (2 adenomas). No lung tumors were found in the lower concentration groups and in the control group. The incidence and distribution of other types of tumors were not influenced by polymeric MDI.

In this 2-year rat study the NOAEC was 0.2 mg/m³ for the repeated dose toxicity of polymeric MDI. The LOAEC was set on 1.0 mg/m³.

 


Justification for classification or non-classification

According to the Regulation (EC) No 1272/2008 the test material does not meet the criteria for classification and will not require labelling.


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