1,3-bis(isocyanatomethyl)benzene

Endpoint summary

Description of key information

In an OECD 422 study, rats were exposed orally (gavage) to XDI up to 200 mg/kg bw/day for approx 42 days. In a sub-chronic (90-d) inhalation toxicity study in rats according to OECD413 with the read across substance NBDI, rats were exposed up to 2.03 mg/m3.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: oral

Remarks:

combined repeated dose and reproduction / developmental screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

June 25 - November 19, 2008

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

other: Crl:CD (SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Hino Breeding Center, Charles River Laboratories Japan, Inc.
- Age at study initiation: 10 weeks
- Weight at study initiation: males 355-394 g and females 240-285 g, females satellite groups 247-279 g
- Fasting period before study: not indicated
- Housing: During acclimatization animals were housed individually in stainless stgeel suspended ages. Animals were paired in males' cages. Dams were housed individually in plastic cages floored with an autoclaved substate of wood chips on Day 18 of pregnancy and thereafter. The dams were housed individually in stainless steel suspended cages on Day 4 of lactation and thereafter.
- Diet: ad libitum to feeders of solid diet (CRF-1, Oriental Yeast Co., Ltd.)
- Water: ad libitum tap water
- Acclimation period: 14 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21.9-24.3
- Humidity (%): 44-63
- Air changes (per hr): 12
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
The required amount of the test substance was measured out and dissolved in corn oil to a concentration of 40 mg/ml. Dosing preparations containing the test substance at concentrations of 10 and 2.5 mg/ml were prepared by serial dilution of the dosing preparation at 40 mg/ml with corn oil. Preparations were used within 4 hours and 54 minutes of preparation. Dosing volumes 5 ml/kg/day on the most recent body weight.

VEHICLE
- Justification for use and choice of vehicle (if other than water): corn oil
- Concentration in vehicle: same dosing volume.
- Lot/batch no.: V8F7016

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Concentrations of the substance in dosing preparations which were used for both sexes in the test groups on the first day of dosing and for the males in the test groups on the last dosing day were measured by gas chromatography. Concentrations were between 92.9 and 95.1% of target concentration. All results of the examination of specificity, linearity, precision, and intr-assay precision, which were obtained from the present study were within the acceptable criteria. The standard solution was confirmed to be stable in an autosampler for 24 hours. See report study no. 093527, validation of an analytical method for determination of m-xylylene diisocyanate concentration in dosing preparations, June 11, 2008.

Duration of treatment / exposure:

Males treated for 14 days before mating and thereafter 28 days, total of 42 days. Half of the males per group were given a 14-day recovery period.
Females treated for 14 days before mating, during the mating period (max 4 days), and during pregnancy up to Day 6 of lactaction, a total of 44 - 48 days. Females of satellite groups, treated for 42 days, were given a 14-day recovery period.

Frequency of treatment:

daily

Dose / conc.:

12.5 mg/kg bw/day (actual dose received)

Dose / conc.:

50 mg/kg bw/day (actual dose received)

Dose / conc.:

200 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

12 males including 6 with a recovery period.
12 females
6 females in satellite group with recovery period.

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Dose levels based on a preliminary study in which death was noted at 500 mg/kg/day and higher. The dosing length in the present study was to be more than 3 times longer than in the preliminary study, the high dose was selected to be 200 mg/kg/day, at which toxicity was expected to occur and lower dose levels were calculated using a common ration of 4.
- Rationale for animal assignment (if not random): Random sampling method so that the mean body weight and variance were as equal as possible among the groups.
- Post-exposure recovery period in satellite groups: 14 days.

Positive control:

not applicable

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS:
- Time schedule: Animals were observed for mortality and clinical signs twice a day, once before and once after administration, once a day during the recovery period and once on the day of necropsy.

BODY WEIGHT: Yes
- Time schedule for examinations: twice a week and on the day of necropsy, with females during pregnancy on Days 0, 7, 14 and 21 and on Days 0, 4 and 6 of lactation.

FOOD CONSUMPTION AND COMPOUND INTAKE:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
Time schedule: approx twice a week

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations: approx twice a week

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: After last dosing day and after temination of recovery period.
- Anaesthetic used for blood collection: Yes, by ip injection of sodium pentobarbital
- Parameters examined: according to OECD 422 (1996)

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: see haematology
- Parameters examined: according to OECD 422 (1996)

URINALYSIS: Yes
- Time schedule for collection of urine: Fresh urine and 24-hour urine was collected. For males on day 37 of administration and day 9 of recovery, for females on day 5 of lactation and day 9 of recovery.

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: All animals were observed for FOB before start of administration and once a week during administration.
- Dose groups that were examined: all dose groups
- Battery of functions tested: FOB consisted of observations on: posture, palpebral closure, biting behavior and convulsions; ease of removal from cage, ease of handling, muscle tone, fur conditions, lacrimation, salivation, and respiration. In the open field, frequency of rearing and frequency of grooming for 2 minutes, gait, palpebral closure, consciousness, behavioral abnormalities, and righting reflex.
Sensory reactivity and grip strength in males before necropsy, in 6 females/group on Day 3 of lactation. Spontaneous Motor Activity in males on day 40 of administration and females on day 4 of lactation.

OTHER:
Estrous cycles: Females were observed once a day from the first dosing day to the day before confirmation of copulation.
Mating: After 14 days of treatment, males and females were paired continuously for a maximum period of 14 days until copulation was confirmed.
Nursing conditions: Dams were observed for nursing conditions once a day from days 0 to 4 of lactation.

Pups - F1:
At delivery dams were examined for the number of pups born, their sexes, number of stillbirths, live pups born, and external abnormalities.
Pups were observed for clinical signs and mortality once a day.
Pups were weighed on Day 0 and Day 4 of lactation.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
Organ weights in males: brain, pituitary, salivary glands, thyroids, thymus, heart, liver, spleen, kidneys, adrenals, testes and epididymides.
Females: number of corpora lutea and number of implantation sites were counted. After necropsy organ weights: same as males + ovaries and uterus.
HISTOPATHOLOGY: Yes
Organs and tissues from males and females of the high dose and control group were examined. When abnormalities were found, e.g. stomach, lower doses were also examined. Organs and tissues examined: heart, lungs, trachea, liver, pancreas, salivary glands, esophagus, stomach, duodenum, jejunum, ileum, cecum, colon, rectum, thymus, spleen, lymph nodes, kidneys, urinary bladder, testes, epididymides, seminal vesicles, prostate, pituitary, adrenals, thyroids, parathyroid glands, brain, spinal cord, sciatic nerves, eyeballs, Harderian glands, bone marrow and bones, testes, ovaries, uterus, vagina, and mammary glands.

Statistics:

Data were tested by Bartlett's test for homogeneity of variance, when variances were homogeneous, Dunnett's test was performed to compare the control group with each of the groups treated with substance. When variance was heterogeneous, Steel's test was performed.
FOB and reproduction/developmental parameters data were tested by Steel's test. Copulation index, fertility index and gestation index were tested by Fisher's exact test.
Effects in stomach: Steel's test was performed. When significant differences were seen, dose-responsiveness was tested by Cochran-Armitage exact test.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Salivation was noted in 200 and 50 mg/kg bw/day group animals after administration. This was considered to be due to the irritancy of the substance and since no further neurological effects were found, not regarded as a systemic effect. During recovery no clinical signs in females and only one male with soiled perineal area was noted.

Mortality:

no mortality observed

Description (incidence):

No dead or moribund males/females were noted in any group.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weight was significantly lower in the males at 200 mg/kg bw/day throughout the administration period and in the females at the same dose level on Day 15 of administration, throughout pregnancy, and on Days 0 and 6 of lactation. Body weight was also lower in the males at 50 mg/kg bw/day on Days 29 and 36 of administration. However, these findings at 50 mg/kg bw/day are not considered attributable to the test substance, since (1) the differences from the control group were small, (2) these findings were transient changes, and (3) food consumption was not adversely affected by the test substance at this dose level. During the recovery period, body weight stayed lower in both sexes at 200 mg/kg bw/day but tended to revert to the normal body weight.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

In the measurement of food consumption, lower food consumption was noted in the males at 200 mg/kg bw/day at the beginning of the administration period, but no changes attributable to the test substance were noted in the females at this dose level. During the recovery period, food consumption was higher in the males at 200 mg/kg bw/day, but this finding is considered to be a recoverable change which occurred after termination of the administration period.

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

effects observed, treatment-related

Description (incidence and severity):

In the measurement of water consumption, higher water consumption was noted in the males at 200 mg/kg bw/day at the end of the administration period, in the females at this dose level before the start of mating, and in the females at 200 and 50 mg/kg bw/day during the lactation period. However, these findings were not regarded as having been caused by the toxicity of the test substance, since all of them were transient changes. During the recovery period, water consumption was higher in the males at 200 mg/kg bw/day, but no changes attributable to the test substance were noted in the females at this dose level.

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Description (incidence and severity):

No changes attributable to test substance were noted in either sex on termination of the administration period or recovery period.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

No changes attributable to test substance were noted in either sex on termination of the administration period or recovery period.

Urinalysis findings:

no effects observed

Description (incidence and severity):

No changes attributable to test substance were noted in either sex on termination of the administration period or recovery period.

Behaviour (functional findings):

effects observed, treatment-related

Description (incidence and severity):

In the measurement of spontaneous motor activity in the females at 200 mg/kg bw/day, the ambulatory count and vertical count were lower 70 minutes after administration, and a lower total vertical count and a tendency for total ambulatory count to be lower were noted on termination of the administration period. In the males, no changes attributable to the test substance were noted in the spontaneous motor activity. Regarding FOB, sensory reactivity, and grip strength, no changes attributable to the test substance were noted in either sex at any dose level.

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

In the organ weight measurement on termination of the administration period, a higher relative spleen weight and a tendency for the absolute spleen weight to be higher were noted in the males at 200 mg/kg bw/day, and higher absolute and relative spleen weights were noted in the females at this dose level. On termination of the recovery period, no changes attributable to the test substance were noted in either sex at any dose level. However, the histopathological examinations on termination of the administration period (see below) shows that there were no changes attributable to the test substance in the spleen in either sex, and hematological examinations shows that the parameters related to the organ weight changes were not affected by the test substance. Therefore, the findings in the spleen weights at 200 mg/kg bw/day in the present study are considered to be minor changes.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Test substance-like residuals were noted in the stomach of animals of both sexes at 200 mg/kg bw/ day.

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

In the histopathological examinations, the following findings were noted in the males:
slight or mild hyperplasia of squamous epithelium in the forestomach in all 6 males at 200 mg/kg bw/day and in 1 male at 50 mg/kg bw/day, slight or mild hyperkeratosis in the forestomach in all 6 males at 200 mg/kg bw/day, slight inflammatory cell infiltration in the forestomach in 1 male at 200 mg/kg bw/day, and cystic changes in the epithelial layer of the forestomach in 1 male at 200 mg/kg bw/day. In the females at 200 mg/kg bw/day, the following findings were noted: slight hyperplasia of squamous epithelium in the forestomach in 3 females, slight inflammatory cell infiltration in the forestomach in 1 female, and cystic changes in the epithelial layer of the forestomach in 1 female. From these findings in the stomach, it can be said that the above-mentioned higher water consumption in both sexes at 200 mg/kg bw/day was a change to alleviate the irritancy of m-xylylene diisocyanate given to the stomach; the higher water consumption noted in the present study is not judged to be a toxicological change. Since no histopathological changes in the stomach were noted in either sex on termination of the recovery period, higher water consumption occurring during administration will revert to normal water consumption after the discontinuation of administration.

Histopathological findings: neoplastic:

not examined

Other effects:

no effects observed

Description (incidence and severity):

In the examinations for reproductive/developmental toxicity in parent animals, no changes attributable to the test substance were noted in the number of estrous cases during the administration period (for 14 days) before the start of mating, copulation index, number of conceiving days, number of pregnant females, fertility index, length of gestation, gestation index, number of corpora lutea, number of implantation sites, implantation index, delivery conditions, or nursing conditions.
In the pups (F1), no changes attributable to the test substance were noted in the number of pups born, number of stillbirths, number of live pups born on Day 0 of lactation, delivery index, birth index, live birth index, sex ratio, number of live pups on Day 4 of lactation, viability index on Day 4 of lactation, clinical signs, body weight on Day 0 or 4 of lactation, appearance, or necropsy findings.

Dose descriptor:

NOAEL

Remarks:

systemic

Effect level:

50 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Significantly decreased bodyweight in males and pregnant females.

Dose descriptor:

NOAEL

Remarks:

local

Effect level:

12.5 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: Histopathological changes in forestomach and salivation

Critical effects observed:

not specified

Conclusions:

The NOAEL for local effects is 12.5 mg/kg bw/d based on histopathological effects in the forestomach. The NOAEL for systemic effects is 50 mg/kg bw/d based on decreased body weight and salivation.

Executive summary:

Rats were administered 0, 12.5, 50 or 200 mg/kg bw/d of test substance in a study performed according to OECD 422 (1996). Rats were dosed from 14 days before mating during mating and afterwards (total 42 days) for males and during mating period, pregnancy and up to lactation day 6 for females. No mortality occurred. Salivation was noted at 50 and 200 mg/kg bw/d in both sexes. Body weight was decreased in both sexes at 200 mg/kg bw/d. For food and water consumption only transient effects were noted which may be due to irritation of the stomach. No test substance-related effect was seen on haematological, clinical chemistry and urinalysis parameters or at gross pathology. Histopathology revealed an increased incidence of hyperplasia of squamous epithelium and hyperkeratosis in the forestomach in both sexes at 200 mg/kg bw/d. Inflammatory cell infiltration in the forestomach and mild cystic changes in the epithelial cell layer of the forestomach were noted in one male and one female at 200 mg/kg bw/d.

The NOAEL for local effects is 12.5 mg/kg bw/d based on histopathological effects in the forestomach. The NOAEL for systemic effects is 50 mg/kg bw/d based on decreased body weight and salivation.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

50 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

The study has Klimisch score 1

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Hypothesis for the analogue approach: The source chemical is also a diisocyanate. The molecular structure of the substance and of the source chemical both contain two isocyanate groups and no other functional group(s). The hypothesis is based on the fact that the presence of two of these functional groups in the molecular structure of a chemical, without the presence of another functional group, mainly determines its properties relevant for hazard assessment. In Section 13 of the IUCLID dossier, a report is attached in which the analogue approach is reported according to ECHA Guidance for the implementation of REACH, Guidance on information requirements and chemical safety assessment, Chapter R.6 (reporting format for the analogue approach).

Reason / purpose for cross-reference:

read-across source

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

The highest dose group (2.03 ug/L) showed signs of irritation (some rubbing noses with paws and sneezing) starting from day 5 throughout the study. This dose group also showed to be less responsive to outside stimuli starting from day 22 throughout the study.

Mortality:

no mortality observed

Description (incidence):

There were no unscheduled deaths.

Body weight and weight changes:

no effects observed

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:

no effects observed

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

For a small number of parameters the differences between control and the highest dose group attained a degree of statistical signifance:
HCt: 4.4%; RBC: 3.7% and MCHC: 2.4% (all 3 parameters in males only)
For the parameter LUC, the differences between control and dose groups 0.12 and 2.03 ug/L attained a degree of statistical signifance in the males:
0.12 ug/L: 47%; 0.55 ug/L: 13.9%; 2.03 ug/L: 36%
As the differences were not dose-related and inconsistent between the sexes, they are not considered as toxicological relevant.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Statistically significant observations:
-In males at the highest dose group, the parameter Ca Total was 3% decreased compared to the control
-In females at the highest dose group, the parameter Phos was 21.8% decreased compared to the control
As the differences were small, not dose-related and inconsistent between the sexes, they are not considered as toxicological relevant.

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

No effects were seen in females at 0.12 and 0.55 ug/L and in males at 0.12 ug/L.
Erosion (2/10)/hyperplasia (10/10) with (3/10) or without (7/10) inflammation (rhinitis) were detected in the transitional epithelium of male rats from the 2.03 ug/L dose group. Hyperplasia of the transitional epithelium was seen at a low incidence in male rats from the 0.55 ug/L dose group (2/10).
Hyperplasia was detected in the respiratory epithelium of rats, of both sexes, from the 2.03 ug/L dose group (males: 7/10; females: 2/10), but only in male rats from the 0.55 ug/L dose group (2/10).

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

local effects

Histopathological findings: neoplastic:

not examined

Key result

Dose descriptor:

NOAEC

Remarks:

systemic effects

Effect level:

>= 2.03 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse effects up to and including highest dose tested

Key result

Dose descriptor:

NOAEC

Remarks:

local effects

Effect level:

0.12 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: Hyperplasia with or without inflammation (rhinitis) in the transitional epithelium and hyperplasia in the respiratory epithelium at 0.55 ug/L and above

Dose descriptor:

NOAEC

Remarks:

local effects

Effect level:

0.55 mg/m³ air (analytical)

Based on:

test mat.

Sex:

female

Basis for effect level:

histopathology: non-neoplastic

Key result

Critical effects observed:

no

Evaluation:

-No systemic effects observed of toxicological relevance

-Local effects observed starting from 0.55 ug/L in males:

Erosion/hyperplasia with or without inflammation (rhinitis) were detected in the transitional epithelium of rats from the 2.03 ug/L dosage group. Hyperplasia of the transitional epithelium was seen at a low incidence in male rats from the 0.55 ug/L dosage groups. Hyperplasia was detected in the respiratory epithelium of rats, of both sexes, from the 2.03 ug/L dosage groups, but only in male rats from the 0.55 ug/L dosage group.

Conclusions:

In a sub-chronic (90-d) inhalation toxicity study with NBDI in rats a NOAEC (local effects) of 0.12 mg/m3 was established based on hyperplasia with or without inflammation (rhinitis) in the transitional epithelium in males at 0.55 mg/m3. In the same study, a NOAEC (systemic effects) of ≥2.03 mg/m3 (highest dose tested) was established. This result is read across to XDI.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

2.03 mg/m³

Study duration:

subchronic

Species:

rat

Quality of whole database:

The study has Klimisch score 2, because it is a read across study

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Hypothesis for the analogue approach: The source chemical is also a diisocyanate. The molecular structure of the substance and of the source chemical both contain two isocyanate groups and no other functional group(s). The hypothesis is based on the fact that the presence of two of these functional groups in the molecular structure of a chemical, without the presence of another functional group, mainly determines its properties relevant for hazard assessment. In Section 13 of the IUCLID dossier, a report is attached in which the analogue approach is reported according to ECHA Guidance for the implementation of REACH, Guidance on information requirements and chemical safety assessment, Chapter R.6 (reporting format for the analogue approach).

Reason / purpose for cross-reference:

read-across source

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

The highest dose group (2.03 ug/L) showed signs of irritation (some rubbing noses with paws and sneezing) starting from day 5 throughout the study. This dose group also showed to be less responsive to outside stimuli starting from day 22 throughout the study.

Mortality:

no mortality observed

Description (incidence):

There were no unscheduled deaths.

Body weight and weight changes:

no effects observed

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:

no effects observed

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

For a small number of parameters the differences between control and the highest dose group attained a degree of statistical signifance:
HCt: 4.4%; RBC: 3.7% and MCHC: 2.4% (all 3 parameters in males only)
For the parameter LUC, the differences between control and dose groups 0.12 and 2.03 ug/L attained a degree of statistical signifance in the males:
0.12 ug/L: 47%; 0.55 ug/L: 13.9%; 2.03 ug/L: 36%
As the differences were not dose-related and inconsistent between the sexes, they are not considered as toxicological relevant.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Statistically significant observations:
-In males at the highest dose group, the parameter Ca Total was 3% decreased compared to the control
-In females at the highest dose group, the parameter Phos was 21.8% decreased compared to the control
As the differences were small, not dose-related and inconsistent between the sexes, they are not considered as toxicological relevant.

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

No effects were seen in females at 0.12 and 0.55 ug/L and in males at 0.12 ug/L.
Erosion (2/10)/hyperplasia (10/10) with (3/10) or without (7/10) inflammation (rhinitis) were detected in the transitional epithelium of male rats from the 2.03 ug/L dose group. Hyperplasia of the transitional epithelium was seen at a low incidence in male rats from the 0.55 ug/L dose group (2/10).
Hyperplasia was detected in the respiratory epithelium of rats, of both sexes, from the 2.03 ug/L dose group (males: 7/10; females: 2/10), but only in male rats from the 0.55 ug/L dose group (2/10).

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

local effects

Histopathological findings: neoplastic:

not examined

Key result

Dose descriptor:

NOAEC

Remarks:

systemic effects

Effect level:

>= 2.03 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse effects up to and including highest dose tested

Key result

Dose descriptor:

NOAEC

Remarks:

local effects

Effect level:

0.12 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: Hyperplasia with or without inflammation (rhinitis) in the transitional epithelium and hyperplasia in the respiratory epithelium at 0.55 ug/L and above

Dose descriptor:

NOAEC

Remarks:

local effects

Effect level:

0.55 mg/m³ air (analytical)

Based on:

test mat.

Sex:

female

Basis for effect level:

histopathology: non-neoplastic

Key result

Critical effects observed:

no

Evaluation:

-No systemic effects observed of toxicological relevance

-Local effects observed starting from 0.55 ug/L in males:

Erosion/hyperplasia with or without inflammation (rhinitis) were detected in the transitional epithelium of rats from the 2.03 ug/L dosage group. Hyperplasia of the transitional epithelium was seen at a low incidence in male rats from the 0.55 ug/L dosage groups. Hyperplasia was detected in the respiratory epithelium of rats, of both sexes, from the 2.03 ug/L dosage groups, but only in male rats from the 0.55 ug/L dosage group.

Conclusions:

In a sub-chronic (90-d) inhalation toxicity study with NBDI in rats a NOAEC (local effects) of 0.12 mg/m3 was established based on hyperplasia with or without inflammation (rhinitis) in the transitional epithelium in males at 0.55 mg/m3. In the same study, a NOAEC (systemic effects) of ≥2.03 mg/m3 (highest dose tested) was established. This result is read across to XDI.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

0.12 mg/m³

Study duration:

subchronic

Species:

rat

Quality of whole database:

The study has Klimisch score 2, because it is a read across study

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Rats were administered orally 0, 12.5, 50 or 200 mg/kg bw/d of test substance in a study performed according to OECD 422 (1996). Dose levels were set based on a 14 -day preliminary study with pronounced toxicity at 250 -1000 mg/kg bw/d. Rats were dosed from 14 days before mating during mating and afterwards (total 42 days) for males and during mating period, pregnancy and up to lactation day 6 for females. No mortality occurred. Salivation was noted at 50 and 200 mg/kg bw/d in both sexes. Body weight was decreased in both sexes at 200 mg/kg bw/d. For food and water consumption only transient effects were noted which may be due to irritation of the stomach. No test substance-related effect was seen on haematological, clinical chemistry and urinalysis parameters or at gross pathology. Histopathology revealed an increased incidence of hyperplasia of squamous epithelium and hyperkeratosis in the forestomach in both sexes at 200 mg/kg bw/d  and in one male at 50 mg/kg bw/d. Inflammatory cell infiltration in the forestomach and mild cystic changes in the epithelial cell layer of the forestomach were noted in one male and one female at 200 mg/kg bw/d.

The NOAEL for local effects is 12.5 mg/kg bw/d based on histopathological effects in the forestomach. The NOAEL for systemic effects is 50 mg/kg bw/d based on decreased body weight and salivation.

Rats were exposed whole body via inhalation to 0, 0.12, 0.55 and 2.03 mg/m3 vapour of the substance NBDI (Reaction mass of 2,5-bis(isocyanatomethyl)-bicyclo[2.2.1]heptane and 2,6-bis(isocyanatomethyl)-bicyclo[2.2.1]heptane) in a study performed according to OECD 413. Dose levels were set based on the acute inhalation study and rats were exposed for 6h/d, 5d/w, 13 consecutive weeks. No systemic effects were observed up to the highest dose tested. The following histopathological (local) effects were seen: Erosion/hyperplasia with or without inflammation (rhinitis) were detected in the transitional epithelium of male rats from the 2.03 mg/m3 dose group. Hyperplasia of the transitional epithelium was seen at a low incidence in male rats from the 0.55 mg/m3 dose group. Hyperplasia was detected in the respiratory epithelium of rats, of both sexes, from the 2.03 mg/m3 dose group, but only in male rats from the 0.55 mg/m3 dose group. The NOAEC for systemic effects is >=2.03 mg/m3, while the NOAEC for local effects is determined to be 0.12 mg/m3.

Hypothesis for the analogue approach: The source chemical is also a diisocyanate. The molecular structure of the substance and of the source chemical both contain two isocyanate groups and no other functional group(s). The hypothesis is based on the fact that the presence of two of these functional groups in the molecular structure of a chemical, without the presence of another functional group, mainly determines its properties relevant for hazard assessment. In Chapter 13 of the IUCLID dossier, a report is attached in which the analogue approach is reported according to ECHA Guidance for the implementation of REACH, Guidance on information requirements and chemical safety assessment, Chapter R.6 (reporting format for the analogue approach).

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Only one study available

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
Only one study available

Justification for selection of repeated dose toxicity inhalation - local effects endpoint:
Only one study available

Justification for classification or non-classification

Based on the available oral study, XDI does not have to be classified according to the CLP Regulation (EC) No. 1272/2008 for repeated dose toxicity. However, based on the available inhalation study with the read across substance NBDI, the substance XDI needs to be classified according to CLP Regulation (EC) No. 1272/2008 for repeated dose toxicity via inhalation. The effects were observed at a low concentration (0.55 mg/m3) which is a factor 100 lower compared to single toxicity, and therefore the effect should be considered to be a repeated dose effect distinct from the acute toxicity (ECHA Guidance on the Application of the CLP Criteria, version 28/08/2009, page 376 -377), and thus the substance should be classified with:

STOT RE Category 1: Causes damage to organs (respiratory tract), through prolonged or repeated exposure (inhalation), in accordance with the CLP Regulation