N,N''-methylenebis[N'-[3-(hydroxymethyl)-2,5-dioxoimidazolidin-4-yl]urea]

Endpoint summary

Description of key information

Subchronic oral NOEL (rat) 280 mg/kg/day based on read-across, supported by a subchronic oral NOAEL for the registered substance 653-672 mg/kg/day, which was considered insufficient for use in assessment.

Subacute dermal NOAEL (systemic toxicity, rabbit) 200 mg/kg/day.

Subacute LOAEL for localised dermatitis after repeated occlusive application to skin 45 mg/kg/day.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

sub-chronic toxicity: oral

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Read-across from Klimisch 1 study performed on a close structural analogue which is manufactured in the same way (reaction of formaldehyde with a modified urea) and reacts with water in the same way (hydrolysis releasing formaldehyde) as the registered substance

Qualifier:

according to guideline

Guideline:

EPA OPP 82-1 (90-Day Oral Toxicity)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

42 days old at start of treatment: bodyweights males 175-195g, females 145-178g. Individually housed; animal room 19-23C, 30-80% humidity, 12h dark/light cycle. Food and water provided ad lib.

Route of administration:

oral: gavage

Vehicle:

water

Remarks:

(distilled)

Details on oral exposure:

Gavage dosing at 5 ml/kg dose volume.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Stability (up to14 days) and homogeneity of formulated doses was confirmed. Achieved concentrations were confirmed by analysis of samples taken weekly to Week 4, then in Weeks 7, 10 and 13.
Analytical method: after addition of a colour reagent to diluted samples and heating (70C, 1h), absorbance at 492nm was determined.

Duration of treatment / exposure:

91 or 92 days (staggered termination).

Frequency of treatment:

Daily

Remarks:

Doses / Concentrations:
200 mg/kg
Basis:
other: ingested dose (corrected for active ingredient)

Remarks:

Doses / Concentrations:
500 mg/kg
Basis:
other: ingested dose (corrected for active ingredient)

Remarks:

Doses / Concentrations:
1000 mg/kg
Basis:
other: ingested dose (corrected for active ingredient)

No. of animals per sex per dose:

20 males, 20 females

Control animals:

yes, concurrent vehicle

Details on study design:

Samples from 10M, 10F/group taken for haematology, clinical chemistry and urinalysis.

Positive control:

No

Observations and examinations performed and frequency:

Twice daily cageside observations. Detailed weekly observations including bodyweight.
Opthalmoscopy: pretest and at termination.
Blood samples taken at termination, after fasting: full haematology and clinical chemistry.
Urinalysis: at termination.

Sacrifice and pathology:

Macroscopic observations at necropsy.
Organ weights: adrenals, brain, heart, kidneys, liver, lungs, ovaries, pituitary, spleen, testes with epididymides, thyroid/parathyroids, uterus.

Tissues collected: weighed organs plus aorta (thoracic), bone and bone marrow (sternum/femur), oesophagus, eyes with optic nerve, intestine (caecum, colon, ileum, jejunum, rectum), lacrymal gland, lymph nodes, mammary gland, sciatic nerve, pancreas, prostate, salivary glands, seminal vesicles, skeletal muscle, skin spinal cord (cervical, thoracic, lumbar), stomach, thymic region, trachea, urinary bladder, uterus with cervix, gross lesions.

Histopathology: all collected tissues from control and high-dose groups plus decedents. Kidneys, liver, lungs, stomach, adrenals, gross lesions for other test groups.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

2 males died at 1000 mg/kg/day. Excessive salivation seen at 500 and 1000 mg/kg/day.

Mortality:

mortality observed, treatment-related

Description (incidence):

2 males died at 1000 mg/kg/day. Excessive salivation seen at 500 and 1000 mg/kg/day.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

decreased in males dosed at 1000 mg/kg/day.

Food consumption and compound intake (if feeding study):

no effects observed

Ophthalmological findings:

no effects observed

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

Haemoglobin, haematocrit and erythrocyte counts were significantly decreased, leucocyte counts increased at 1000 mg/kg/day (both sexes); erythrocytes were significantly decreased in males at 500 mg/kg/day.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

At 1000 mg/kg/day glucose, total protein, albumin and globulin significantly decreased, albumin/globulin ratio increased. Total protein, globulin and albumin/globulin ration were reduced at 500 mg/kg (and glucose decreased in males).

Urinalysis findings:

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Absolute and relative adrenal weights increased significantly at 1000 and at 500 (males only) mg/kg/day. In females absolute and relative liver weights increased significantly at 1000 and 500 mg/kg/day, pituitary weights decreased at 1000 mg/kg/day.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Stomach lesions (nodules, masses, swelling) seen at 1000 mg/kg/day.

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Necrotising gastritis of forestomach and/or glandular stomach seen at 500 and 1000 mg/kg/day (severe at 1000 mg/kg/day).

Details on results:

Homogeneity and stability of test doses plus achieved concentrations (within 20% of nominal values) were confirmed by analysis.

Dose descriptor:

NOEL

Effect level:

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

Based on:

act. ingr.

Sex:

male/female

Basis for effect level:

other: Based on stomach lesions and associated clinical pathology parameters observed at 500 and 1000 mg/kg/day.

Remarks on result:

other: 1-[1,3-bis(hydroxymethyl)-2,5-dioxoimidazolidin-4-yl]-1,3-bis(hydroxymethyl)urea (CAS# 78491-02-8)

Key result

Dose descriptor:

NOEL

Effect level:

280 mg/kg bw/day (nominal)

Based on:

other: analogue: CAS# 78491-02-8

Sex:

male/female

Basis for effect level:

other: See above

Remarks on result:

other: Comparing the difference in molecular weight between the registered substance and its analogue, a factor of 1.4 should be applied on the NOEL.

Critical effects observed:

yes

Lowest effective dose / conc.:

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

System:

gastrointestinal tract

Organ:

stomach

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

not specified

Conclusions:

Daily oral dosing of rats at 200 mg/kg/day produced no effects considered treatment-related: this is concluded to be the NOEL for the tested analogue. Main target organ was identified as the fore-and glandular stomach. Based on the similarity of chemical structure and properties including hydrolysis to release formaldehyde, it is predicted that the registered substance will show a similar toxicological profile.

Reference 2

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well reported subchronic toxicity study performed in accordance with current practice at the time: limited tissue list examined microscopically.

Qualifier:

no guideline followed

Principles of method if other than guideline:

90-day rat feeding study with haematology, blood chemistry and urinalysis plus limited organ weights at necropsy and micropathology (protocol adapted from a US EPA recommendation).

GLP compliance:

no

Remarks:

Pre-GLP study

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

Weanling rats, housed individually with free accesss to food and water.

Route of administration:

oral: feed

Vehicle:

other: test substance incorporated into diet

Details on oral exposure:

Test substance mixed into Purina Laboratory Chow diet: concentrations adjusted at intervals to take account of increasing rat bodyweights.

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

Continuous, in diet.

Remarks:

Doses / Concentrations:
6, 28, 130, 600 mg/kg/day
Basis:
other: target values for ingested dose of test substance.

Remarks:

Doses / Concentrations:
7, 31, 147, 672 mg/kg/day
Basis:
other: Males: ingested dose of test substance, calculated from bodyweight, food intake and dietary content.

Remarks:

Doses / Concentrations:
7, 30, 140, 653 mg/kg/day
Basis:
other: Females: ingested dose of test substance, calculated from bodyweight, food intake and dietary content.

No. of animals per sex per dose:

7 males, 7 females: blood and urine samples collected in Week 12 from 5 males, 5 females/group. All animals subjected to macroscopic examination at necropsy and micropathology.

Control animals:

yes, plain diet

Details on study design:

Groups of 7M, 7F rats fed test or control diet for 13 weeks.

Observations and examinations performed and frequency:

Animals observed daily, bodyweights and food consumption measured weekly. From 5M, 5F/group blood sampled at study start and in Week 12, urine collected in Week 12.

Sacrifice and pathology:

Animals terminated in Week 13: macroscopic examinations at necropsy included liver, spleen and kidney weights. Stained sections of liver, spleen, kidneys, lungs and bladder examined microscopically.

Other examinations:

Haematology parameters investigated: white blood cells, differential count, haemoglobin, haematocrit.
Blood chemistry parameters investigated: blood urea nitrogen, glucose, cholesterol, serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, lactic dehydrogenase, serum alkaline phosphatase, uric acid, creatinine phosphokinase, creatinine.
Urinary parameters investigated: pH, specific gravity, albumin, glucose, ketones, bile, occult blood.

Statistics:

t-test used to determine significance of an observed bodyweight depression in test groups.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Overall net bodyweight gains reduced in males dosed at nominal 28, 130 and 260 mg/kg/day.

Food efficiency:

no effects observed

Description (incidence and severity):

Possible minor reduction in high-dose males only.

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

Organ weight findings including organ / body weight ratios:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Details on results:

Limited reductions in bodyweight gain in males dosed at (nominal) 28 mg/kg/day or higher was the only observed effect of treatment. The reduction in weight gain compared to controls was <20% in males given the highest test dosage.

Dose descriptor:

NOEL

Effect level:

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

Based on:

test mat.

Remarks:

calculated daily intake over test period

Sex:

female

Basis for effect level:

other: No effects at the highest dose tested.

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Remarks:

calculated daily intake over test period

Sex:

male

Basis for effect level:

body weight and weight gain

Critical effects observed:

not specified

Group description	Nominal intake (mg/kg/day)	Calculated actual intake (mg/kg/day)	Group net bodyweight gain (g)	Food utilisation efficiency (g weight gain/100g food eaten)
Control males	0	0	324	16.9
Test males 1	6	7	303	15.5
Test males 2	28	31	270*	15.5
Test males 3	130	147	278*	15.8
Test males 4	600	672	265*	14.9
Control females	0	0	161	11.2
Test females 1	6	7	159	10.9
Test females 2	28	30	166	11.5
Test females 3	130	140	166	11.1
Test females 4	600	653	151	10.7

* Significantly different from control group (Group 2 p<0.05, Groups 3 and 4 p<0.01)

Conclusions:

Based on the limited magnitude of the observed weight gain reduction in males, the absence of an equivalent and clearly dose-related effect on food utilisation efficiency and the absence of any other indicator of toxicity in test group males, 672 mg/kg/day can be considered a male NOAEL for systemic toxicity in this study (NOEL 6 mg/kg/day). For females, 653 mg/kg/day was a NOEL.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

280 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

The available information is sufficient for determination of an NOAEL value.

Organ:

stomach

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Data waiving:

other justification

Justification for data waiving:

other:

Critical effects observed:

not specified

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Data waiving:

other justification

Justification for data waiving:

other:

Critical effects observed:

not specified

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well reported subacute toxicity study performed in accordance with current practice at the time: limited tissue list examined microscopically.

Qualifier:

no guideline followed

Principles of method if other than guideline:

21-day rabbit dermal toxicity study with haematology and urinalysis plus limited organ weights at necropsy and micropathology (protocol adapted from a US EPA recommendation).

GLP compliance:

no

Remarks:

Pre-GLP study

Limit test:

no

Species:

rabbit

Strain:

other: described as albino rabbits

Sex:

male/female

Details on test animals or test system and environmental conditions:

Initial bodyweights: males 2.19-3.38 kg, females 1.94-3.42 kg.
Individually housed, with free access to food and water.

Type of coverage:

occlusive

Vehicle:

unchanged (no vehicle)

Details on exposure:

Test substance applied to the dorsal skin (at least 10% of body area, initially shaved, then reclipped as necessary) daily for 6h/day, 5 days/week over a 3-week period.

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

3 weeks (5 days/week).

Remarks:

Doses / Concentrations:
20, 45, 90, 200 mg/kg/day.
Basis:
nominal per unit body weight

No. of animals per sex per dose:

5 males, 5 females.

Control animals:

yes, sham-exposed

Details on study design:

In each group, skin at the test site was abraded in 3 females, 2 males (test sites at the remaining 3 males, 2 females were left as intact skin). Local skin reactions were scored as well as systemic toxicity parameters.

Positive control:

Not required.

Observations and examinations performed and frequency:

Bodyweights were recorded and blood plus urine samples collected pretreatment and at study termination.

Sacrifice and pathology:

Examinations at necropsy included measurement of liver, kidney and spleen weights as well as recording of any macroscopic abnormalities.

Other examinations:

Stained sections of lungs, liver, kidneys, spleen, bladder, test site skin and adjacent normal skin plus macroscopic abnormalities were examined microscopically.
Haematology parameters investigated: white blood cells, differential count, haemoglobin, haematocrit.
Urinary parameters investigated: pH, specific gravity, albumin, glucose, ketones, bile, occult blood.

Clinical signs:

no effects observed

Description (incidence and severity):

A single female dosed at 90 mg/kg/day died on Day 18 of the test period. This was not attributed to treatment with the test substance. No adverse reactions to treatment were reported.

Dermal irritation:

effects observed, treatment-related

Description (incidence and severity):

Cses of localised slight to mild acute or chronic dermatitis (sometimes with ulceration or pustule formation) were observed. At intact skin test sites, this was seen in 2 animals at 45 mg/kg/day and 4 at 200 mg/kg/day.

Mortality:

no mortality observed

Description (incidence):

A single female dosed at 90 mg/kg/day died on Day 18 of the test period. This was not attributed to treatment with the test substance. No adverse reactions to treatment were reported.

Body weight and weight changes:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

not examined

Urinalysis findings:

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Description (incidence and severity):

except for test site skin lesions in 3/5 males, 1/5 females treated at 200 mg/kg/day. These were superficial and judged to be reversible (and similar changes were seen in one control animal).

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

cases of local local test site dermatitis at higher dose levels.

Details on results:

Light to mild superficial dermatitis, sometimes with focal ulceration and/or pustules, was seen at intact skin test sites in some animals treated at 200 mg/kg/day, and (by microsopic examination only) in one male treated at 45 mg/kg/day. Similar responses were seen in a few animals treated at abraded skin test sites. Daily skin reaction scores during the treatement period never exceeded 1 for erythema (very slight), and were all 0 for oedema (none seen).

Dose descriptor:

NOAEL

Effect level:

200 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: NOAEL for systemic toxicity: no observed effect on bodyweight, haematology, urine, organ weights or pathology other than skin at test sites.

Dose descriptor:

LOAEL

Effect level:

45 mg/kg bw/day

Based on:

test mat.

Sex:

male

Basis for effect level:

other: Based on local reaction at test sites (for intact skin, seen in 2 animals at this dosage and 3 at 200 mg/kg/day).

Dose descriptor:

LOAEL

Effect level:

200 mg/kg bw/day

Based on:

test mat.

Sex:

female

Basis for effect level:

other: Based on local reaction at test sites (in intact skin, seen only in 1 female treated at this dosage).

Critical effects observed:

not specified

No evidence of systemic toxicity was observed. A high incidence of pulmonary oedema was seen in lung sections from all groups including controls but this was not associated with any other lung abnormalities and was considered unrelated to treatment.

Conclusions:

This study found no evidence of systemic toxicity when rabbits were treated dermally (6h/day under occluded dressing) with the test substance at dosages up to 200 mg/kg/day. Localised skin reactions to treatment were observed.

Executive summary:

Rabbits dosed dermally for 15 days (within a 3 -week period) showed local reactions indicative of a mild inflammatory response. In the absence of clinical chemistry tests and with only limited haematology investigations and micropathology list, the observed absence of systemic toxicity at the maximum tested dosage does not provide definitive evidence of low toxicity.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

200 mg/kg bw/day

Study duration:

subacute

Species:

rabbit

Quality of whole database:

This study is considered reliable (Klimisch 2) and sufficient for determination of a systemic toxicity NOAEL.

Repeated dose toxicity: dermal - local effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well reported subacute toxicity study performed in accordance with current practice at the time: limited tissue list examined microscopically.

Qualifier:

no guideline followed

Principles of method if other than guideline:

21-day rabbit dermal toxicity study with haematology and urinalysis plus limited organ weights at necropsy and micropathology (protocol adapted from a US EPA recommendation).

GLP compliance:

no

Remarks:

Pre-GLP study

Limit test:

no

Species:

rabbit

Strain:

other: described as albino rabbits

Sex:

male/female

Details on test animals or test system and environmental conditions:

Initial bodyweights: males 2.19-3.38 kg, females 1.94-3.42 kg.
Individually housed, with free access to food and water.

Type of coverage:

occlusive

Vehicle:

unchanged (no vehicle)

Details on exposure:

Test substance applied to the dorsal skin (at least 10% of body area, initially shaved, then reclipped as necessary) daily for 6h/day, 5 days/week over a 3-week period.

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

3 weeks (5 days/week).

Remarks:

Doses / Concentrations:
20, 45, 90, 200 mg/kg/day.
Basis:
nominal per unit body weight

No. of animals per sex per dose:

5 males, 5 females.

Control animals:

yes, sham-exposed

Details on study design:

In each group, skin at the test site was abraded in 3 females, 2 males (test sites at the remaining 3 males, 2 females were left as intact skin). Local skin reactions were scored as well as systemic toxicity parameters.

Positive control:

Not required.

Observations and examinations performed and frequency:

Bodyweights were recorded and blood plus urine samples collected pretreatment and at study termination.

Sacrifice and pathology:

Examinations at necropsy included measurement of liver, kidney and spleen weights as well as recording of any macroscopic abnormalities.

Other examinations:

Stained sections of lungs, liver, kidneys, spleen, bladder, test site skin and adjacent normal skin plus macroscopic abnormalities were examined microscopically.
Haematology parameters investigated: white blood cells, differential count, haemoglobin, haematocrit.
Urinary parameters investigated: pH, specific gravity, albumin, glucose, ketones, bile, occult blood.

Clinical signs:

no effects observed

Description (incidence and severity):

A single female dosed at 90 mg/kg/day died on Day 18 of the test period. This was not attributed to treatment with the test substance. No adverse reactions to treatment were reported.

Dermal irritation:

effects observed, treatment-related

Description (incidence and severity):

Cses of localised slight to mild acute or chronic dermatitis (sometimes with ulceration or pustule formation) were observed. At intact skin test sites, this was seen in 2 animals at 45 mg/kg/day and 4 at 200 mg/kg/day.

Mortality:

no mortality observed

Description (incidence):

A single female dosed at 90 mg/kg/day died on Day 18 of the test period. This was not attributed to treatment with the test substance. No adverse reactions to treatment were reported.

Body weight and weight changes:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

not examined

Urinalysis findings:

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Description (incidence and severity):

except for test site skin lesions in 3/5 males, 1/5 females treated at 200 mg/kg/day. These were superficial and judged to be reversible (and similar changes were seen in one control animal).

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

cases of local local test site dermatitis at higher dose levels.

Details on results:

Light to mild superficial dermatitis, sometimes with focal ulceration and/or pustules, was seen at intact skin test sites in some animals treated at 200 mg/kg/day, and (by microsopic examination only) in one male treated at 45 mg/kg/day. Similar responses were seen in a few animals treated at abraded skin test sites. Daily skin reaction scores during the treatement period never exceeded 1 for erythema (very slight), and were all 0 for oedema (none seen).

Dose descriptor:

NOAEL

Effect level:

200 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: NOAEL for systemic toxicity: no observed effect on bodyweight, haematology, urine, organ weights or pathology other than skin at test sites.

Dose descriptor:

LOAEL

Effect level:

45 mg/kg bw/day

Based on:

test mat.

Sex:

male

Basis for effect level:

other: Based on local reaction at test sites (for intact skin, seen in 2 animals at this dosage and 3 at 200 mg/kg/day).

Dose descriptor:

LOAEL

Effect level:

200 mg/kg bw/day

Based on:

test mat.

Sex:

female

Basis for effect level:

other: Based on local reaction at test sites (in intact skin, seen only in 1 female treated at this dosage).

Critical effects observed:

not specified

No evidence of systemic toxicity was observed. A high incidence of pulmonary oedema was seen in lung sections from all groups including controls but this was not associated with any other lung abnormalities and was considered unrelated to treatment.

Conclusions:

This study found no evidence of systemic toxicity when rabbits were treated dermally (6h/day under occluded dressing) with the test substance at dosages up to 200 mg/kg/day. Localised skin reactions to treatment were observed.

Executive summary:

Rabbits dosed dermally for 15 days (within a 3 -week period) showed local reactions indicative of a mild inflammatory response. In the absence of clinical chemistry tests and with only limited haematology investigations and micropathology list, the observed absence of systemic toxicity at the maximum tested dosage does not provide definitive evidence of low toxicity.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LOAEL

45

Study duration:

subacute

Species:

rabbit

Quality of whole database:

This study is considered reliable (Klimisch 2) and sufficient for determination of the NOAEL for local effects at sites of occluded skin application.

Additional information

A subchronic rat feeding study and a subacute rabbit dermal study are available. Due to the low level of systemic toxicity observed in these two studies, no target organs were identified. However it was not clear that the limited histopathology investigations included in the feeding study would have detected changes to the fore- and glandular stomach of the type seen in a subchronic oral study conducted with the close chemical analogue diazolidinyl urea. The similarity of formaldehyde donor activity of the registered substance and diazolidinyl urea indicates a likelihood that the necrotising gastritis seen following oral administration of diazolidinyl urea at 500 and 1000 mg/kg/day would occur as a consequence of subchronic administration of the registered substance. For this reason, the diazolidinyl urea subchronic oral study is selected as the key study for assessment of the registered substance and the NOEL determined in that study is considered applicable.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:

Although a 90-day feeding study found only a limited (<20%) reduction in male bodyweight gain after continuous exposure to the registered substance at 653 mg/kg/day (males) or 672 mg/kg/day (females), it was not clear that the limited histopathology investigations included in this study would have detected changes to the fore- and glandular stomach of the type seen in a subchronic oral study conducted with the close chemical analogue diazolidinyl urea.  The similarity of formaldehyde donor activity of the registered substance and diazolidinyl urea  indicates a likelihood that the necrotising gastritis seen following oral administration of diazolidinyl urea at 500 and 1000 mg/kg/day would occur as a consequence of subchronic administration of the registered substance.  For this reason, the diazolidinyl urea study is selected as the key study for assessment of the registered substance and the NOAEL determined in that study is considered applicable.

Justification for selection of repeated dose toxicity dermal - systemic effects endpoint:

No evidence of systemic toxicity seen in this 21-day dermal (6h/day, 5 days/week occluded application) study, where a maximum test dosage of 200 mg/kg/day was employed.

Justification for selection of repeated dose toxicity dermal - local effects endpoint:

Minor local reaction (cumulative irritation response) seen at intact skin test sites in this study in 2/5 males dosed at 45 mg/kg/day and in 3/5 males, 1/5 female dosed at 200 mg/kg/day.  At 45 mg/kg/day, this local reaction was observed only by microscopic tissue examination.

Justification for classification or non-classification

The concluded NOAEL values and the minimal nature of the localised reaction to repeated, occluded application to rabbit skin demonstrate that no classification in respect of repeated exposure is warranted, under the terms of either the CLP Regulation or the older DSD rules.