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Toxicological information

Carcinogenicity

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Description of key information

Key value for chemical safety assessment

Carcinogenicity: via oral route

Endpoint conclusion
Endpoint conclusion:
no study available

Carcinogenicity: via inhalation route

Link to relevant study records
Reference
Endpoint:
carcinogenicity: inhalation
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
1983 - 1985
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP guideline study According to ECHA Practical Guide 6 the maximum score for read across is rel. 2
Justification for type of information:
ANALOGUE APPROACH JUSTIFICATION
See document attached to this endpoint study record
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)
Version / remarks:
(1981)
Qualifier:
according to
Guideline:
EPA OTS 798.3320 (Combined Chronic Toxicity / Carcinogenicity)
GLP compliance:
yes
Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories (Kingston, New York)
- Age at study initiation: approx. 7 weeks
- Mean weight at study initiation: males: 161-176 g; females: 121-124 g
- Housing: individual
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: at least 8 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20.5-23.3
- Humidity (%): 35-55
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12 / 12
Route of administration:
inhalation: vapour
Type of inhalation exposure (if applicable):
whole body
Vehicle:
air
Details on exposure:
ANIMAL EXPOSURE CHAMBER:
The chambers used in this study were Hazelton-2000s. These chambers were constructed of stainless steel with clear plastic windows. Each chamber had an approximate volume of two cubic meters. The chambers were equipped with stainless steel, wire mesh cages for individual housing of animals. The cage-racks were fitted with removable feed troughs and an automatie watering system. The air supplied to the chambers passed through an activated-charcoal trap and a HEPA filter before it was conditioned.
CHAMBER AIRFLOW:
Chamber airflow was measured using a calibrated orifice plate and an electro-mechanical transducer. The airflow through each chamber was monitored continuously and recorded at 5-6 minute intervals by a MACSYM 2 (Analog Devices Inc., MA) computer system. The airflow set-point for each chamber was 700 Lpm. Thus, the air turnover rate was set at approximately 21 chamber volumes per hour.
TREATMENT OF CHAMBER EXHAUST:
The air exhausted from each exposure chamber was filtered through an activated-charcoal trap and a HEPA filter before it was vented outside
the building.
CHAMBER TEMPERATURE / RELATIVE HUMIDITY / STATIC PRESSURE:
The thermocouples and the relative humidity sensors (Model SSP128B) were manufactured by HoneyweIl (Minneapolis. Minnesota). Static pressure was measured using Magnahelic gauges. The desired ranges for chamber temperature and relative humidity were 20 to 24°C and 40 to 60 %. respectively. The static pressure set-point was -0.5 inch of water relative to atmospheric pressure. The temperature and relative humidity data were recorded at 5-6 minute intervals by the MACSYM 2 computer system. Static pressure was manually recorded.
GENERATION OF HDI ATMOSPHERE:
HDI vapor was generated by passing filtered, dry air through liquid HDI in a glass bubbler. During vapor generation the bubbler containing HDI was immersed in a constant temperature water bath (Thermomix 1441E, Braun-Melsungen). The water bath temperature and the airflow through the bubbIer were monitored and recorded at hourly intervals during the six-hour exposures.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Samples from the chambers were collected near the animal's breathing zone at a rate of 1 Lpm using two midget impingers connected in series. An acetonitrile solution (10 mL) of N-4-nitrobenzyl-N-n-propylamine (nitro reagent) in the impingers was used to trap and derivatize the HDI to an UV-absorbing compound. All midget impinger samples were analyzed by high performance liquid chromatography.
Duration of treatment / exposure:
2 years
Frequency of treatment:
6 hours/day, 5 days/week
Post exposure period:
no
Remarks:
Doses / Concentrations: 0, 0.035, 0.175, and 1.23 mg/m³ (0, 0.005, 0.025, 0.175 ppm)
Basis: target conc.
Remarks:
Doses / Concentrations: 0, 0.035, 0.175, and 1.15 mg/m³ (0, 0.005, 0.025, 0.164 ppm)
Basis: analytical conc.
No. of animals per sex per dose:
60 (for main study) and 10 (animals of satellite groups for sacrifice after one year)
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: A 90-day inhalation toxicity study (Shiotsuka, 1988) was conducted in Fischer 344 rats using analytical concentrations of 0.01, 0.04 and 0.14 ppm of HDI. There were no compound-related changes in body weight in this subchronic study. Compound-related clinical signs of toxicity were limited to ocular irritation and it was observed at all three HDI exposure levels. Somatic lesions (determined by microscopic examination of tissues) of the anterior nasal cavity were observed at all three concentrations. Based on this information the three concentrations selected for the chronic study were 0.005, 0.025 and 0.125 ppm. The highest concentration of 0.125 ppm was increased to 0.175 ppm on study-day 127 and maintained at that level until termination of the study. This change was instituted because overt signs of toxicity were not observed with 0.125 ppm. Since the rats were predominantly exposed to 0.175 ppm, the high concentration group's target concentration will be referred to as being 0.175 ppm.

EXPERIMENTAL DESIGN:
The exposure was conducted under dynamic conditions, the air control animals were sham-exposed (conditioned room air) under comparable conditions.
Observations and examinations performed and frequency:
CLINICAL OBSERVATIONS:
All animals in the study were observed for clinical signs of toxicity and mortality twice on exposure days (prior to the onset of exposure and at approximately one hour post-exposure) and once daily on weekends and holidays.

BODY WEIGHTS:
All rats were weighed weekly for the first 13 weeks of the study. They were then weighed on weeks 15, 17, 19, 21, 23, 27, 31, 34, 35, 39, 43, 51, 55, 59, 63, 67, 71, 75 and 83. Weekly weighings were resumed for weeks 86 through 105.

FOOD AND WATER CONSUMPTION: No data

OPHTHALMOLOGY:
A pre-exposure ophthalmic examination was condueted on ten rats/sex/exposure level. Prior to scheduled sacrifice, the eyes were examined for all survivors in the satellite groups and the main study groups. The indirect method which utilized a condensing lens between the rat's eyes and the ophthalmoscope was used. The examination was performed in a semi-darkened room. The eyes of each rat were checked for a pupillary reflex using the light reflected from the viewing mirror of the ophthalmoscope. The conjunctiva, cornea, and iris of both eyes were also examined using the ophthalmoscope. Two or three drops of a mydriatic were applied to each eye to dilate the pupil. After pupillary dilatation, the lenses, vitreous humors, retinae and optic discs of each rat were examined with the ophthalmoscope.

CLINICAL PATHOLOGY:
At 3-, 6-, 12- and 18-month intervals and prior to sacrifice, hematology, clinical biochemistry, and urinalysis parameters were evaluated on generally 20 rats/sex/level from the main study groups. The same rats were used throughout the study for all determinations to the extent possible. The rats in the bleeding group that died or were sacrificed during the study were replaced so that generally 20 rats/sex/level were available. In addition, blood smears were prepared from rats sacrificed at termination.

Hematology determinations included: erythrocyte morphology, hematocrit, hemoglobin, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, mean corpuscular volume, platelet count, reticulocyte count, total erythrocyte count, total and differential leukocyte count.

Clinical biochemistry determinations included: albumin, calcium, chloride, creatine phosphokinase, creatinine, gamma glutamyl-transpeptidase, globulin, glucose, phosphorus, potassium, serum alkaline phosphatase, serum lactic dehydrogenase, serum alanine aminotransferase, serum aspartate aminotransferase, sodium, total cholesterol, total protein, total bilirubin, urea nitrogen.

Urinalysis determinations included: bilirubin, glucose, ketones, microscopic sediment exam., occult blood, pH, protein, specific gravity, urobilinogen.

NEUROBEHAVIOURAL EXAMINATION: No
Sacrifice and pathology:
ANIMAL SACRIFICE:
Rats in the main study groups were selected for sacrifice based on a randomized listing (SAS software [1]) of animals by test group and sex. All animals sacrificed in extremis or at study termination were killed by carbon dioxide asphyxiation.

GROSS PATHOLOGY:
All study animals were necropsied following death. The necropsy consisted of a systematic gross examination of each animal's general physical condition, body orifices and cavities, and external and internal tissues (40+ organs/tissues). All necropsy findings were recorded manually and were entered into a computer database. The tissues were fixed in 10 percent buffered formalin. The lungs were removed in toto, weighed and perfused intratracheally with 10 percent buffered formalin. The heads were removed and the nasal and paranasal passages were flushed with 10 percent buffered formalin.

ORGAN WEIGHTS AND TERMINAL BODY WEIGHTS:
At necropsy, terminal body weights and organ weights were recorded for the following tissues: liver, lungs, kidneys, adrenals, heart, spleen, gonads, and brain. In addition, relative organ weights (organ weight: body weight ratio x 100) were calculated. Only data from animals sacrificed after one year and after two years of exposure were evaluated.

HISTOPATHOLOGY:
Tissues collected at necropsy were processed routinely and stained with hematoxylin and eosin and were examined by a veterinary pathologist. Recuts and special stains were requested as deemed necessary, and microscopic observations were entered into a computerized database for summation and report generation. Emphasis was placed on the standardization of trimming procedures of the nasal cavity in this inhalation study. Following removal of the mandible, tongue and associated structures, coronal nasal sections were made from the following areas:
Level I : Vestibule (anterior incisor)
Level II : Posterior to incisor teeth
Level III : Prepapilla (midpoint between incisors and incisive papilla)
Level IV : Incisive papilla
Level V : First palatal ridge
Level VI : Second palatal ridge
Level VII : First molar teeth (second molar teeth in satellite animals)
Morphometric determination of nasal mucosal thickness (measured by an ocular micrometer) was performed on the first 30 rats/sex/exposure level at the first and second nasal cavity examination levels. In level I the mid-septal mucosa thickness was measured unilaterally at the greatest width of epithelium. In level II there were single measurements taken of dorsal turbinate epithelium, ventral turbinate epithelium, lateral wall epithelium and septal epithelium at the point of maximum epithelial width. Lesions in sections from the first and second palatal ridges were coded as First Palatal Ridge and those in the section from the first or second molar teeth were coded as First Molar.
Statistics:
Statistical analysis of continuous data was first evaluated by Analysis of Variance (ANOVA) test, followed by Duncan's Multiple Range Test for between-group comparisons. Frequency data were visually examined for trends that could indicate a compound-related effect. When such trends were apparent, the data was further evaluated using a Chi-Square procedure, followed by pairwise comparison with the control group using one-tailed Fischer's Exact Test on data showing significant differences by the Chi-Square analysis. A p-value less than or equal to 0.05 was considered statistically significant. Any reference to significance in the text of this report presumes statistical significance. References to biologie or toxicologic significance are explicitly identified as such.
Details on results:
HISTOPATHOLOGY: NEOPLASTIC:
Mononuclear cell leukemia commonly seen in aged Fischer 344 rats was frequently seen and was coded in the computer under "multiple organs" as weIl as with individual organs with parenchymal infiltrate. There was an elevated (non-statistical) incidence in 0.175 ppm males and 0.025 ppm females. The incidence of mononuclear cell leukemia in this study is compatible with that from the National Toxicology Program (NTP, 1989) [males: 33 ± 14 %; females: 19 ± 6 % ]. Extent of dissemination (mean number of organs affected) of the mononuclear cell leukemia within an animal was not greater in exposed rats in this study.
There was a trend toward an increase (non-statistical) in thyroid c-cell tumors in males (6-6-5-12) and females (1-2-3-6) exposed to 0.175 ppm of HDI. The frequency of occurrence was within that of historical controls at Mobay or the National Toxicology Program database [NTP, 1983], was not associated with increased c-cell hyperplasia and was interpreted to be of no biological significance.
Common neoplasms of aging Fischer 344 rats such as hepatocellular adenoma or carcinoma, alveolar bronchiolar adenoma or carcinoma, adrenal pheochromocytoma, uterine endometrial stromal polyps, testicular interstitial cell tumor, pituitary tumors, or mammary gland tumors of varied morphologic types were not increased with exposure to HDI.
Although the number of animals with tumors in exposed groups was not increased in this study, the numbers of animals with multiple tumors as weIl as the total tumors found were increased in some groups as compared with controls. Note, this trend toward an increased incidence was also seen in males with both benign and malignant tumors and males with at least one malignant tumor. These increased tumor indices are interpreted to be associated with a trend toward increased (non-statistical) incidence of mononuclear cell leukemia because the computer program counts each metastatic site as a discrete tumor.
In summary, no compound-related oncogenicity was observed in male and female rats up to and including 0.175 ppm HDI (analytical conc.: 0.164 ppm HDI). A Maximum Tolerated Dose (MTD) was established at the highest concentration tested.
Dose descriptor:
NOAEL
Effect level:
1.15 other: mg/m³ (eq. to 0.164 ppm)
Sex:
male/female
Basis for effect level:
other: No indications of an increased tumour incidence up to the highest dose tested (1.15 mg/m³). The criteria for a maximum tolerable concentration were fulfilled at this dose level.
Remarks on result:
other: Effect type: carcinogenicity (migrated information)
Dose descriptor:
NOAEL
Effect level:
0.035 other: mg/m³ (eq. to 0.005 ppm)
Sex:
male/female
Remarks on result:
other: Effect type: toxicity (migrated information)
Conclusions:
non carcinogenic
Executive summary:

In a combined chronic toxicity and oncogenicity study in rats according to OECD TG 453 the substance revealed no carcinogenic potential after a 2-year inhalation exposure with vapour at concentrations up to and including 1.15 mg/m³ (eq. to 0.164 ppm). A Maximum Tolerated Dose (MTD) was established at the highest concentration tested.

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

Carcinogenicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Based on a read across to 1,6 -diisocyanatohexane (HDI, CAS 822 -06 -0) no carcinogenic potential is concluded from a combined chronic toxicity and oncogenicity rat study according to OECD TG 453 with 2-year inhalation exposure to the vapour (whole body) at concentrations of 0.005, 0.025, 0.164 ppm (0.035, 0.175, 1.15 mg/m³). A Maximum Tolerated Dose (MTD) was established at the highest concentration tested.

Justification for classification or non-classification

According to Regulation (EC) No 1272/2008, Annex I, no classification is warranted for carcinogenicity.