Registration Dossier

Administrative data

Description of key information

4,4'-Methylenedicyclohexanamine (PACM) has been studied in a 28-day oral repeat dose toxicity study in rats. A structural analogue of PACM, 2,2’-dimethyl-4,4'-methylenedicyclohexanamine (DM-PACM), has been studied in a 90-day oral as well as inhalation repeated dose study in rats. Results of the subchronic studies with DM-PACM allow calculation of NOAELs for subchronic exposure.

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:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
GLP guideline study (OECD 408) of a structural analogue. PACM and DM-PACM are considered read-across analogues based on structural similarity and similar physico-chemical and toxicological properties. The common structural features of the two substances are: a common functional primary amine group; the amines are bound to a cyclic aliphatic organic substituent; there are no elements other than carbon, hydrogen and nitrogen; identical structures except for a methyl group on each cyclohexane, ortho to the amine on DM-PACM similar molecular weights, both under 500 daltons, qualifiying as “low molecular weight” compounds. For a detailed read across justification see also attached background material.
Qualifier:
according to
Guideline:
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity in Rodents)
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Dr. Karl Thomae GmbH, Biberach, Germany
- Age at study initiation: 42 days
- Weight at study initiation: males: 178 (168 - 193) g; females: 147 ( 139 - 157) g
- Housing: single
- Diet: Kliba-Labordiaet Ratte/Maus/Hamster Haltung GLP 343 Mehl, ad libitum
- Water: ad libitum
- Acclimation period: 8 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24 °C
- Humidity (%): 30-70 %
- Photoperiod (hrs dark / hrs light): 12/12
Route of administration:
oral: gavage
Vehicle:
other: 0.5 % CMC (carboxymethyl cellulose)
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
gas chromatography
Duration of treatment / exposure:
3 month
Frequency of treatment:
each working day (5 days/week)
Remarks:
Doses / Concentrations:
2.5, 12, 60 mg/kg bw/day
Basis:
actual ingested
No. of animals per sex per dose:
test group: 30;
control group: 10
Control animals:
yes
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: weekly

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: before and after the application period
- Dose groups that were examined: control and high dose

HAEMATOLOGY: Yes
- Time schedule for collection of blood: day 29 and 85
- Anaesthetic used for blood collection: No data
- Animals fasted: yes, overnight
- How many animals: all
- Parameters examined: Erythrocyte count, hemoglobin, hematocrit, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), thrombocyte count.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: day 29 and 85
- Animals fasted: Yes
- How many animals: all
- Parameters examined: aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, gamma-glutamyltranspeptidase, sodium, potassium, chloride, inorganic phosphorus, calcium, bilirubin total, creatinine, glucose, urea, total protein, albumin, cholesterol, triglycerides.

URINALYSIS: Yes
- Time schedule for collection of urine: day 23 and 79
- Metabolism cages used for collection of urine: Yes
- Animals fasted: No data
- Parameters examined: Nitrite, pH-Value, hemoglobin, protein, glucose, ketone bodies, bilirubin, urobilinogen, sediment, volume.

NEUROBEHAVIOURAL EXAMINATION: No data

OTHER:
blood was sampled from all surviving animals of both sexes for immunological determinations after about 8 and 13 test weeks.
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
Details on results:
CLINICAL SIGNS AND MORTALITY
60 mg/kg bw : On day 71 one male was sacrificed moribund. Deteriorated general state of health with differently discolored regions of various localizations in the animals of both sexes was observed.

BODY WEIGHT AND WEIGHT GAIN
60 mg/kg bw: Significantly retarded body weight gain in both sexes.
12 mg/kg bw: Significantly retarded body weight gain in the female animals, which was present in the males only as a trend.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
60 mg/kg bw: Reduced feed consumption in the males and females.
12 mg/kg bw: Slight reduction of the feed consumption in the females.

OPHTHALMOSCOPIC EXAMINATION
No abnormalities

HAEMATOLOGY
60 mg/kg bw: Increase of the lymphocyte values with changed nuclear structure in both sexes. Increase of the monocyte and neutrophilic polymorphonuclear granulocytes in the females. Decrease of the mean cell volume, mean hemoglobulin content of the individual erythrocyte, of the chloride and creatinine values in both sexes. Decrease of the total protein, albumin, globulins and triglyceride levels in the males. Increased inorganic phosphate in the females.

CLINICAL CHEMISTRY
60 mg/kg bw: Increase of the alanine aminotransferase, aspartate aminotransferase, leukocyte and lymphocyte values in both sexes.
12 mg/kg bw: Increase of the aspartate aminotransferase values in the males.

URINALYSIS
60 mg/kg bw: Increase of the erythrocyte and leukocyte values, of renal and round-cell epithelias, bacterias and roundcell epithelias without nucleus in the urine of both sexes.
12 mg/kg bw: Increase of bacterias and round-cell epithelias without nucleus in the urine of both sexes. Increase of erythrocytes in the urine of the males and single renal and round-cell epithelias in both sexes

ORGAN WEIGHTS
60 mg/kg bw: Increase of the absolute liver weights in the females. Increase of the relative liver weights in the males and females. Increase of the relative kidney weights of the males and females. Increase of the absolute adrenal weights of the males and females. Increase of the relative adrenal weights of the males and females.
12 mg/kg bw: Increase of the relative liver weights in the males. Increase of the absolute kidney weights in the males. Increase of the relative kidney weights in the males and females.

HISTOPATHOLOGY: NON-NEOPLASTIC
60 mg/kg bw: Histopathology revealed microvacuolar degeneration of the liver of most animals. The lesion was qualitatively more distinct in the female than in the male animals. Vacuolar tubulopathy was seen in the kidneys of all animals that were sacrificed at the end of the study. Vacuolar myocardial degeneration was observed in the heart of all male and female animals. The adrenal glands of all male and female animals showed the picture of a progressive transformation.
12 mg/kg bw: Histopathology revealed vacuolar tubulopathy in the kidneys of some male and female animals. The heart of most animals was found to show vacuolar myocardial degeneration

OTHER: The immunological examinations elicited no adverse effects on the humoral parameters examined.
Dose descriptor:
NOAEL
Effect level:
2.5 mg/kg bw/day (actual dose received)
Sex:
male/female
Basis for effect level:
other: see 'Remark'
Critical effects observed:
not specified

In conclusion, the 3-month administration of Laromin C 260 to male and female rats at a dose of 60 mg/kg b.w. each working day by gavage led to clear toxic findings, such as reduced feed consumption, retarded body weight gain, impaired general state of health, changes of the hematologic (white and red blood counts), enzymatic, clinicochemical and urinanalytical parameters as well as hepato and nephrotoxic, myocardially toxic and adrenotoxic (progressive transformation) effects.

12 mg/kg b.w. led in the female animals to a reduced feed consumption, in the animals of both sexes to a retarded body weight gain, and to an increase of the aspartate aminotransferase values in the male animals. Urinalysis detected in both sexes an increased number of bacterias, of round-cell epithelias with and without nucleus, and of renal epithelias and in the male animals an increase of erythrocytes. The pathological examinations exhibited hepato and nephrotoxic and myocardially toxic findings.

  

2.5 mg/kg b.w. caused no differences when compared with the control.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEL
2.5 mg/kg bw/day
Study duration:
subchronic
Species:
rat
Quality of whole database:
adequate

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records
Reference
Endpoint:
sub-chronic toxicity: inhalation
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
GLP guideline study of a structural analogue. PACM and DM-PACM are considered read-across analogues based on common functional groups, common precursors/break-down products, and similar physico-chemical and toxicological properties. The common structural features of the two substances are: a primary amine group, bound to a cyclic aliphatic organic substituent; a bis-cyclic structure. There are no elements other than carbon, hydrogen and nitrogen. They are identical structures except for a methyl group on each cyclohexane, ortho to the amine on DM-PACM.
Qualifier:
according to
Guideline:
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Wistar
Sex:
male/female
Route of administration:
inhalation
Type of inhalation exposure:
nose/head only
Vehicle:
other: fresh air
Remarks on MMAD:
MMAD / GSD: The mass median aerodynamic diameter (MMAD) was 3.5, 1.5, and 2.8 µm, respectively.
Details on inhalation exposure:
Groups of 10 male and 10 female Wistar rats (age 9 weeks, mean body weights 247g and 171 g for male and female animals) were exposed by inhalation to a liquid aerosol of the test substance at concentrations of 2, 12, and 48 µg/l. A control group (10 males, 10 females) was exposed to fresh air.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Analysis confirmed the nominal concentrations. mean values +/- standard deviation were 2.1 +/- 0.58 µg/l, 12.4 +/- 2.63 µg/l, and 48.2 +/-10.48 µg/l.
Duration of treatment / exposure:
3 months
Frequency of treatment:
6 hours each working day (5 d/w)
Remarks:
Doses / Concentrations:
2.1 mg/m3
Basis:
analytical conc.
Remarks:
Doses / Concentrations:
12.4 mg/m3
Basis:
analytical conc.
Remarks:
Doses / Concentrations:
48.2 mg/m3
Basis:
analytical conc.
No. of animals per sex per dose:
10
Control animals:
yes
Details on study design:
Post-exposure period: none
Observations and examinations performed and frequency:
Ophthalmologic examinations were carried out at the beginning and at the end of the study. The state of health was checked before, during and after exposure. Clinicochemical and hematological examinations were carried out. All animals were necropsied and assessed by gross pathology, extensive histopathological examinations were done including examination of the testes, ovaries and uterus.
Other examinations:
The body weight was determined once a week. Feed and water consumption was not measured.
Statistics:
no data
Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
One female at 2 µg/l and one male at 12 µg/l died intercurrently after 37 and 48 exposures, respectively. Deaths were judged to be of spontaneous nature.
Mortality:
mortality observed, treatment-related
Description (incidence):
One female at 2 µg/l and one male at 12 µg/l died intercurrently after 37 and 48 exposures, respectively. Deaths were judged to be of spontaneous nature.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Compared to control animals statistically reduced mean body weight gain (p<0.01) and reduced body weight from day 50 onwards (p<0.01) was seen in high dose male rats. Body weight was reduced by approx 14% compared to controls on day 85. In high dose fe
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:
no effects observed
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
Significant (p<0.05) reductions in hemoglobin, hemoglobin per erythrocyte, and in mean corpuscular hemoglobin concentration (MCHC) were noted in the male high dose rats only. Polychromatosis was noted. Clotting test: statistically significant clotting t
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
Animals at 2µg/l: no substance-related changes noted in either test group. Animals at 12 µg/l: statistically significant, but marginal increase of alkaline phosphatase (5.658 µkat/l vs. 4.949 µkat/l in controls) and GPT (glutamate pyruvate transaminas
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
Relative organ weight of liver, lung, and kidney was significantly increased in high dose male and female animals on the 1% or 5% level of significance. Relative weight of adrenals (p<0.05) and testes (p<0.01), and absolute lung weight (1.41g vs. 1.18g
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
No effects in low and medium dose animal groups. Effects in high dose animals included: Local irritative effects on the skin and slight hyperkeratosis in 7/10 male rats. Minimal to slight vacuolization of the craniodorsal olfactory epithelium in both ma
Details on results:
Toxicity was observed in the high dose group (local irritative effects, decreased body weight gain, increased relative weights of liver, lung and kidney without pathology. In high dose males only, there was increased relative weights of adrenals and testes, without pathology or histopathology. Selected liver enzymes were increased in serum, and red blood cells were increased with decreased hemoglobin but increased hemosiderin deposits in the spleen. The only effect noticed in the mid-dose group was a single clinical chemistry parameter whose value was statistically significantly different from control values, but in the absence of liver histopathology and evidence of toxicity in other enzyme levels, this was considered not biologically significant.
Dose descriptor:
NOAEC
Effect level:
12.2 other: mg/m3
Based on:
test mat.
Sex:
male/female
Basis for effect level:
clinical signs
mortality
food consumption and compound intake
organ weights and organ / body weight ratios
gross pathology
Critical effects observed:
not specified
The read-across to PACM is adequate for designation of a NOAEL for risk assessment for chronic exposure, and adequate for classification and labeling
    
    
    
    
    

PACM and DM-PACM are considered read-across analogues based on structural similarity and similar physico-chemical and toxicological properties. The common structural features of the two substances are: a common functional primary amine group; the amines are bound to a cyclic aliphatic organic substituent; there are no elements other than carbon, hydrogen and nitrogen; identical structures except for a methyl group on each cyclohexane, ortho to the amine on DM-PACM similar molecular weights, both under 500 daltons, qualifiying as “low molecular weight” compounds

PACM and DM-PACM are considered read-across analogues based on structural similarity and similar physico-chemical and toxicological properties. The common structural features of the two substances are: a common functional primary amine group; the amines are bound to a cyclic aliphatic organic substituent; there are no elements other than carbon, hydrogen and nitrogen; identical structures except for a methyl group on each cyclohexane, ortho to the amine on DM-PACM similar molecular weights, both under 500 daltons, qualifiying as “low molecular weight” compounds

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

RS-Freetext:
Overall assessment:
No treatment-related effect was noted in animal groups at 2 and 12 µg/l apart from the increased GPT level in mid dose male rats.

Although clear effects on body weight gain were noted in the high dose groups target organ toxicity was mild and restricted to red blood cells, including the spleen (extramedulary haematopoesis) indicative of a mild anemic effect.
There were increases in clinical chemical parameters (GPT and GOT) as well as in the relative liver weight; however, no histopathological correlate was found in this study.
A substance-related effect on kidneys (slight tubular nephrosis with increased kidney weights) was of borderline significance. Other organ weight changes were seen (increased relative weights of testes and adrenals), but were considered to be secondary toxic effects due to severe impairment of the body weight.
According to the authors, under the conditions of this study, the NOAEC was 2 µg/l (0.002 mg/l), based on slightly increased GPT level (1.043 µkat/l vs. 0.845 µkat/l in controls) observed in mid dose males representing a borderline toxicity.

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

Conclusions:
4,4'-Methylenebis(2-methyl-cyclohexanamine) an analogue of PACM, was tested in a 90-day inhalation toxicity study in male and female Wistar rats at concentrations of 2, 12 and 48 mg/m3 for 6 hours daily, 5 days per week. Clear toxicity was noted in animals exposed to 48 mg/m3. Local effects included degeneration of the olfactory epithelium. In the high dose group, hepatotoxicity, adverse effects on red blood cells, hemoglobin, and spleen were noted as was a reduced body weight gain. Male animals were more susceptible than females. The NOAEC was 12 mg/m3 (0.012 mg/l) in this study, based on clear toxicity observed in high dose male rats.
Selected data can be ”read-across” to 4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue, 2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on common functional groups, common precursors/break-down products, and similar physico-chemical and toxicological properties. The read-across is adequate for designation of a NOAEC for risk assessment for chronic exposure, and adequate for classification and labeling
Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEC
12 mg/m³
Study duration:
subchronic
Species:
rat
Quality of whole database:
adequate

Repeated dose toxicity: inhalation - local effects

Link to relevant study records
Reference
Endpoint:
sub-chronic toxicity: inhalation
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
GLP guideline study of a structural analogue. PACM and DM-PACM are considered read-across analogues based on common functional groups, common precursors/break-down products, and similar physico-chemical and toxicological properties. The common structural features of the two substances are: a primary amine group, bound to a cyclic aliphatic organic substituent; a bis-cyclic structure. There are no elements other than carbon, hydrogen and nitrogen. They are identical structures except for a methyl group on each cyclohexane, ortho to the amine on DM-PACM.
Qualifier:
according to
Guideline:
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Wistar
Sex:
male/female
Route of administration:
inhalation
Type of inhalation exposure:
nose/head only
Vehicle:
other: fresh air
Remarks on MMAD:
MMAD / GSD: The mass median aerodynamic diameter (MMAD) was 3.5, 1.5, and 2.8 µm, respectively.
Details on inhalation exposure:
Groups of 10 male and 10 female Wistar rats (age 9 weeks, mean body weights 247g and 171 g for male and female animals) were exposed by inhalation to a liquid aerosol of the test substance at concentrations of 2, 12, and 48 µg/l. A control group (10 males, 10 females) was exposed to fresh air.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Analysis confirmed the nominal concentrations. mean values +/- standard deviation were 2.1 +/- 0.58 µg/l, 12.4 +/- 2.63 µg/l, and 48.2 +/-10.48 µg/l.
Duration of treatment / exposure:
3 months
Frequency of treatment:
6 hours each working day (5 d/w)
Remarks:
Doses / Concentrations:
2.1 mg/m3
Basis:
analytical conc.
Remarks:
Doses / Concentrations:
12.4 mg/m3
Basis:
analytical conc.
Remarks:
Doses / Concentrations:
48.2 mg/m3
Basis:
analytical conc.
No. of animals per sex per dose:
10
Control animals:
yes
Details on study design:
Post-exposure period: none
Observations and examinations performed and frequency:
Ophthalmologic examinations were carried out at the beginning and at the end of the study. The state of health was checked before, during and after exposure. Clinicochemical and hematological examinations were carried out. All animals were necropsied and assessed by gross pathology, extensive histopathological examinations were done including examination of the testes, ovaries and uterus.
Other examinations:
The body weight was determined once a week. Feed and water consumption was not measured.
Statistics:
no data
Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
One female at 2 µg/l and one male at 12 µg/l died intercurrently after 37 and 48 exposures, respectively. Deaths were judged to be of spontaneous nature.
Mortality:
mortality observed, treatment-related
Description (incidence):
One female at 2 µg/l and one male at 12 µg/l died intercurrently after 37 and 48 exposures, respectively. Deaths were judged to be of spontaneous nature.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Compared to control animals statistically reduced mean body weight gain (p<0.01) and reduced body weight from day 50 onwards (p<0.01) was seen in high dose male rats. Body weight was reduced by approx 14% compared to controls on day 85. In high dose fe
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:
no effects observed
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
Significant (p<0.05) reductions in hemoglobin, hemoglobin per erythrocyte, and in mean corpuscular hemoglobin concentration (MCHC) were noted in the male high dose rats only. Polychromatosis was noted. Clotting test: statistically significant clotting t
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
Animals at 2µg/l: no substance-related changes noted in either test group. Animals at 12 µg/l: statistically significant, but marginal increase of alkaline phosphatase (5.658 µkat/l vs. 4.949 µkat/l in controls) and GPT (glutamate pyruvate transaminas
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
Relative organ weight of liver, lung, and kidney was significantly increased in high dose male and female animals on the 1% or 5% level of significance. Relative weight of adrenals (p<0.05) and testes (p<0.01), and absolute lung weight (1.41g vs. 1.18g
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
No effects in low and medium dose animal groups. Effects in high dose animals included: Local irritative effects on the skin and slight hyperkeratosis in 7/10 male rats. Minimal to slight vacuolization of the craniodorsal olfactory epithelium in both ma
Details on results:
Toxicity was observed in the high dose group (local irritative effects, decreased body weight gain, increased relative weights of liver, lung and kidney without pathology. In high dose males only, there was increased relative weights of adrenals and testes, without pathology or histopathology. Selected liver enzymes were increased in serum, and red blood cells were increased with decreased hemoglobin but increased hemosiderin deposits in the spleen. The only effect noticed in the mid-dose group was a single clinical chemistry parameter whose value was statistically significantly different from control values, but in the absence of liver histopathology and evidence of toxicity in other enzyme levels, this was considered not biologically significant.
Dose descriptor:
NOAEC
Effect level:
12.2 other: mg/m3
Based on:
test mat.
Sex:
male/female
Basis for effect level:
clinical signs
mortality
food consumption and compound intake
organ weights and organ / body weight ratios
gross pathology
Critical effects observed:
not specified
The read-across to PACM is adequate for designation of a NOAEL for risk assessment for chronic exposure, and adequate for classification and labeling
    
    
    
    
    

PACM and DM-PACM are considered read-across analogues based on structural similarity and similar physico-chemical and toxicological properties. The common structural features of the two substances are: a common functional primary amine group; the amines are bound to a cyclic aliphatic organic substituent; there are no elements other than carbon, hydrogen and nitrogen; identical structures except for a methyl group on each cyclohexane, ortho to the amine on DM-PACM similar molecular weights, both under 500 daltons, qualifiying as “low molecular weight” compounds

PACM and DM-PACM are considered read-across analogues based on structural similarity and similar physico-chemical and toxicological properties. The common structural features of the two substances are: a common functional primary amine group; the amines are bound to a cyclic aliphatic organic substituent; there are no elements other than carbon, hydrogen and nitrogen; identical structures except for a methyl group on each cyclohexane, ortho to the amine on DM-PACM similar molecular weights, both under 500 daltons, qualifiying as “low molecular weight” compounds

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

RS-Freetext:
Overall assessment:
No treatment-related effect was noted in animal groups at 2 and 12 µg/l apart from the increased GPT level in mid dose male rats.

Although clear effects on body weight gain were noted in the high dose groups target organ toxicity was mild and restricted to red blood cells, including the spleen (extramedulary haematopoesis) indicative of a mild anemic effect.
There were increases in clinical chemical parameters (GPT and GOT) as well as in the relative liver weight; however, no histopathological correlate was found in this study.
A substance-related effect on kidneys (slight tubular nephrosis with increased kidney weights) was of borderline significance. Other organ weight changes were seen (increased relative weights of testes and adrenals), but were considered to be secondary toxic effects due to severe impairment of the body weight.
According to the authors, under the conditions of this study, the NOAEC was 2 µg/l (0.002 mg/l), based on slightly increased GPT level (1.043 µkat/l vs. 0.845 µkat/l in controls) observed in mid dose males representing a borderline toxicity.

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

Selected data can be ”read-across” to4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue,2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on structural similarity and similar physico-chemical and toxicological properties.  Both substances are part of a larger OECD chemical category of twelve members, the Primary Amine Category.  Specifically, the concept of read-across between the two cyclohexamines was promoted in the recent OECD SIAR, which identified DM-PACM as “the surrogate for cyclohexylamine, 4,4’-methylenebis- (1761-71-3)” for repeated dose toxicity and reproductive toxicity endpoints. Concerning physico-chemical properties, values from both chemicals are comparable. The freezing and boiling points, vapour pressure and Henry’s Law Constants are slightly higher for DM-PACM than for PACM, which is characteristic of increasing molecular weight. Both display low water solubility and the partitioning between n-octanol and water are comparable.  Environmental fate parameters are comparable. Both are hydrolytically stable and neither are biodegradable. However, they are not bioaccumulative and their acute toxicity levels to aquatic organisms are low. In mammalian toxicity tests, they display similar behaviours, including skin and eye corrosion and weak activity in dermal sensitisation assays. DM-PACM may be slightly more toxic than PACM; hence, reading across from DM-PACM should not underestimate the toxicity of PACM.

Conclusions:
4,4'-Methylenebis(2-methyl-cyclohexanamine) an analogue of PACM, was tested in a 90-day inhalation toxicity study in male and female Wistar rats at concentrations of 2, 12 and 48 mg/m3 for 6 hours daily, 5 days per week. Clear toxicity was noted in animals exposed to 48 mg/m3. Local effects included degeneration of the olfactory epithelium. In the high dose group, hepatotoxicity, adverse effects on red blood cells, hemoglobin, and spleen were noted as was a reduced body weight gain. Male animals were more susceptible than females. The NOAEC was 12 mg/m3 (0.012 mg/l) in this study, based on clear toxicity observed in high dose male rats.
Selected data can be ”read-across” to 4,4'-methylenebis(cyclohexanamine) (PACM, target chemical) from its analogue, 2,2'-dimethyl-4,4'-methylenebis(cyclohexylamine) (dimethyl or DM-PACM, source chemical), based on common functional groups, common precursors/break-down products, and similar physico-chemical and toxicological properties. The read-across is adequate for designation of a NOAEC for risk assessment for chronic exposure, and adequate for classification and labeling
Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEC
12 mg/m³
Study duration:
subchronic
Species:
rat
Quality of whole database:
adequate

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

oral

Currently, there is one oral subacute reprotoxicity screening study (OECD 422) with 4,4'-methylenedicyclohexanamine (PACM) available:

Four groups of ten male and ten female Wistar Han rats were exposed by oral gavage to the test substance dosed in propylene glycol at 0, 15, 50 and 100 mg/kg bw/day (deGraff-Heezen, 2010). Due to toxicity observed in females in the main study at 150 mg/kg including clinical signs (hunched posture, rales and piloerection) and marked body weight loss, the dose level was lowered to 100 mg/kg bw on Day 12 of treatment, and the pre-mating period was consequently extended to 3 weeks instead of 2 to allow for partial recovery before mating. Males were exposed for 36 days, i.e. 3 weeks prior to mating, during mating, and up to termination. High dose animals were exposed for 11 days to 150 mg/kg and 25 days (males) or 37-41 days (females) to 100 mg/kg. Females were exposed for 48-52 days, i.e. during 3 weeks prior to mating, during mating, during post-coitum, and during at least 4 days of lactation. The following parameters were evaluated: mortality / viability, clinical signs, functional observations, body weights, food consumption, reproduction/developmental parameters, observations pups, clinical pathology, macroscopy, organ weights, and histopathology. Chemical analyses of formulations were conducted once during the study to assess accuracy, homogeneity and stability. There were treatment-related and toxicologically relevant effects at 50 and 100 mg/kg bw. At the high dose, two females were euthanized in extremis. Clinical signs including hunched posture, yellow feces, piloerection, lean appearance, ptosis, lethargy, chromodacryorrhoea, and rales. Body weights, body weight gains and food consumption were reduced. Clinical biochemistry parameters were affected including increased aspartate aminotransferase (ASAT) and reduced creatinine levels (both sexes). Treatment related microscopic findings of various organs at 100 mg/kg bw were noted, including: the stomach (vaculolation of the stomach musculature; both sexes), liver (centrilobular vacuolation; both sexes), brain (vacuolation of the choroid plexus; both sexes), skeletal muscle (vacuolar myofiber degeneration and myofiber degeneration; both sexes), and the eyes (vacuolation of the cuboidal epithelium of the iris; both sexes). At 50 mg/kg bw exposure, slight reductions in body weights and food consumption were noted on a few occasions, but at the degree observed were not considered to be biologically significant. Microscopic findings were noted for various organs, including the stomach (vaculolation of the stomach musculature; both sexes), liver (centrilobular vacuolation; both sexes), skeletal muscle (vacuolar myofiber degeneration and myofiber degeneration; both sexes), and the eyes (vacuolation of the cuboidal epithelium of the iris; both sexes). No toxicologically relevant changes were seen at 15 mg/kg bw. Treatment with the test substance by oral gavage in male and female Wistar Han rats at dose levels of 15, 50 and 100 mg/kg body weight/day revealed parental toxicity at 50 mg/kg bw characterized by microscopic findings in various organs and at 100 mg/kg body weight/day characterized by changes in body weights, food consumption, clinical biochemistry parameters, organ to body weight ratio changes and histopathological findings in various organs. Based on these results, the systemic NOAEL was 15 mg/kg bw/day.

 

PACM and DM-PACM (CAS 6864 -37 -5) are structurally very similar low molecular weight cyclic diamines, which differ only in the additional methyl groups in the ortho positions of the cyclohexane rings. They are low volatile (vapour pressure < 0.1 hPa) organic compounds with similar specific gravity (PACM: 210.36 g/mol and DM-PACM: 238.42 g/mol) and log Pow values between 2.03 for PACM and 2.30 for DM-PACM. Moreover, the comparison of the available toxicity data for both compounds indicates a similar toxicological profile: the substances are showing moderate acute toxicity by the oral route (i.e. oral LD50values for DM-PACM in the range of 320-460 mg/kg bw and 380 mg/kg bw for PACM), and they are corrosive to skin and eyes. These amino-mediated corrosive properties of PACM as well as DM-PACM may be at least in part responsible for the acute toxic effects of both compounds. The additional methyl groups of DM-PACM apparently do not affect the anticipated toxicity. Furthermore,the major routes of metabolism of PACM and DM-PACM include oxidation, conjugation, and other enzyme-catalyzed reactions. This results in detoxification and excretion via urine or faeces.

There is a modern subchronic toxicitity study (OECD 408) for DM-PACM available, which can be used as source chemical for a read across approach. Rats were administered the test substance by gavage at dose levels of 2.5, 12, and 60 mg/kg bw. The animals were dosed for a time span of three months. Liver, white and red blood cells, kidneys, adrenal glands and heart were the target organs for toxic effect showing also histopathological alterations: histopathology revealed microvacuolar degeneration of the liver of most animals. The lesion was qualitatively more distinct in the female than in the male animals. Vacuolar tubulopathy was seen in the kidneys of all animals that were sacrificed at the end of the study. Vacuolar myocardial degeneration was observed in the heart of all male and female animals. The adrenal glands of all male and female animals showed the picture of a progressive transformation. At the high dose level (60 mg/kg bw) body weight development and food consumption were clearly impaired and the general state of health was poor. While the toxic effects at the mid dose of 12 mg/kg bw were generally less pronounced, histopathological examinations revealed vacuolar tubulopathy in the kidneys of some male and female animals, and the heart of most animals was found to show vacuolar myocardial degeneration. The NOAEL was achieved at 2.5 mg/kg bw.

By comparison, the results of the study with DM-PACM and the results of the OECD 422 with PACM both revealed distinctive and comparable toxic effects with the liver, kidney, and muscle tissues as main target organs. Additionally, the NOAELs determined are entirely in the same range: NOAELDM-PACM = 2.5 mg/kg bw and NOAELPACM = 5 mg/kg bw (by applying a 28-days to 90-days exposure duration extrapolation factor of three).

 

As supporting information, PACM was also investigated in several studies in Japan as the possible cause of scleroderma-like symptoms found in workers in an epoxy glue polymerization factory (Yamakage, 1980). Adverse effects after oral administration to rats included decreased weight gain and liver and kidney weight changes with a NOAEL of 37.5 mg/kg bw. Using light and electron microscopy, the researchers found muscular degeneration/regeneration and formation of lamellar inclusion bodies in muscles and the choroid plexus of the brain. Later studies suggest that these effects may be due to the presence or formation of other compounds used in the epoxy hardening process, such as isocyanates or generalized solvents. In the 28-day oral toxicity guideline study with PACM, similar findings were seen in liver, skeletal muscle, choroid plexus of the brain and cuboid epithelium of the eye. This was specifically described as vacuolar degeneration at doses of 100 mg/kg bw, with a NOAEL of 15 mg/kg bw.

 

 

inhalation

Currently, there is no inhalation study with PACM available. Nevertheless, a subchronic study via the inhalative route (OECD 413) was carried out with DM-PACM and can be used for cross reading in analogous way to the oral route of exposure.

Rats were exposed to aerosol concentrations of 0, 2, 12 and 48 mg DM-PACM/m³ for 3 months (6 hours/day and 5 days/week) (BASF AG, 1992). No mortalities occurred. In the high exposure group local irritative effects, typical for alkaline compounds such as amines were observed for the skin (slight hyperkeratosis in 7/10 animals) and upper airways (nasal mucosa, slight vacuolization of olfactory epithelium in 2/10 high dose males, and in 1/10 high dose females). A clear and statistically significant depression of body weight development was noted in animals of both sexes. Compared to control animals terminal body weight was significantly reduced by 14 % in males (p < 0.01) and 8 % in females (p < 0.05). Systemic toxicity was mild. Relative organ weight of liver, lung, and kidney was significantly increased in high dose male and female animals on the 1 % or 5 % level of significance. Relative weight of adrenals (p < 0.05) and testes (p < 0.01) and absolute lung weight (1.41 g vs. 1.18 g in controls, p < 0.05) were significantly increased only in high dose male rats. The relative organ weight changes were largely influenced by reduced body weights and were judged to be of minor relevance. Pathological correlates were not found for any of these organs, and histological alterations in the testes were not seen.

The liver was also a target organ in high dose male rats, but not in high dose females, as substantiated by significant increases of serum transaminases GOT and GPT (glutamate oxalo-acetate transaminase and glutamate pyruvate transaminase, both on the p < 0.01 level). Activity of GPT in serum was 1.081μkat/l in high dose male rats compared to 0.845μkat in control animals. However, no histopathological correlate was seen. Red blood cells were affected in high dose male rats as substantiated by significant reductions (p < 0.05) of hemoglobin, hemoglobin per erythrocyte, mean corpuscular hemoglobin concentration, and polychromatosis. In spleen hemosiderin was noted in all high dose animals and extramedulary haematopoesis (9/10 high dose females) was indicative of a mild anemic effect. A test substance related effect on kidneys was of borderline significance (slight tubular nephrosis in 6/10 high dose males vs. 1/10 male controls; in females 7/10 mid dose and 9/10 high dose rats vs. 7/10 control animals) with increased relative kidney weights (p < 0.01) and increased urea concentration in females (p < 0.01; unchanged in males). In the mid dose animals only a marginal yet significant increase of GPT and alkaline phosphatase levels (both at p < 0.05) in the male rats were seen. Alkaline phosphatase (AP) was not significantly increased in animals at the higher dose level. Therefore no dose-relation was given for AP, and this finding was not regarded as a treatment-related effect. The increase of GPT in mid dose males was marginal (1.043μkat/l vs. 0.845μkat/l in controls). GOT (glutamateoxaloacetate transaminase) was not affected in this animal group. No substance-related effect was noted in the low dose groups.

The marginal increase in GPT level at 12 mg/m3was not considered toxicologically relevant in the absence of an increase in GOT levels and any other effects in the liver. Therefore, the NOAEC was set at 12 mg/m3.

 

 

conclusion

The results of the sub-chronic studies with DM-PACM and the results of the sub-acute study with PACM revealed distinctive and comparable toxic effects on the liver, kidney, and muscle tissues as main target organs. Additionally, the NOAELs determined are entirely in the same range: NOAELDM-PACM = 2.5 mg/kg bw and NOAELPACM = 5 mg/kg bw (by applying a 28-days to 90-days exposure duration extrapolation factor of three).Based on Annex I of Regulation (EC) No.1272/2008 PACM has to be classified with Specific Target Organ Toxicity Repeated Exposure (STOT RE) category 2 (LOAELPACM = ca. 17 mg/kg bw, if extrapolated from sub-acute (LOAEL = 50 mg/kg bw) to sub-chronic exposure). Since the DNELs for PACM are derived from the NOAEL/NOAEC of the sub-chronic repeated dose oral as well as inhalation toxicity studies of DM-PACM(NOAEL (oral) = 2.5 mg/kg bw,NOAEC (inhal.) = 12 mg/m3  3.5 mg/kg bw), this will result in a most conservative risk assessment.


Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Subchronic oral toxicity study in the rat, according to OECD Guideline 408 and GLP

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
Subchronic inhalation toxicity study in the rat, according to OECD Guideline 413 and GLP

Justification for selection of repeated dose toxicity inhalation - local effects endpoint:
Subchronic inhalation toxicity study in the rat, according to OECD Guideline 413 and GLP

Repeated dose toxicity: via oral route - systemic effects (target organ) digestive: liver; other: skeletal muscle

Repeated dose toxicity: inhalation - systemic effects (target organ) digestive: liver

Justification for classification or non-classification

Based on the available data, 4,4'-Methylenedicyclohexanamine is subject to C&L according to Regulation 1272/2008/EC and Directive 67/548/EEC.

 

Directive 67/548/EEC: R48/22 “Danger of serious damage to health by prolonged exposure

Regulation 1272/2008/EC: STOT RE cat. 2, H331 “May cause damage to organs through prolonged or repeated exposure