1,6-hexanediyl bismethacrylate

Endpoint summary

Description of key information

No data are available for 1,6-HDDMA. However, data from the analogous substance 1,4 -BDDMA and metabolites (MAA/MMA and 1,6 -HD) allow the evaluation of repeated dose hazard of 1,6 -HDDMA after oral and inhalative exposure.

Read-across to the metabolites is justified by the fact that carboxylesterases are ubiquitous in the body and half-lifes of the other category substances are only a few minutes (see category document, chapter 5.1). In the body, methyl methacrylate hydrolyses rapidly to methacrylic acid and thus serves as methacrylic acid donor in several test systems investigating systemic effects. For hazard assessment purposes of 1,6 -HDDMA however, a subacute study with the analogous substance 1,4-BDDMA is used as starting point for DNEL calculation.

 

Following data were considered for read across:

Subacute (33-40 day) study; oral (gavage); rat, m/f (OECD guideline 422, GLP): NOAEL = 300 mg/kg bw/d due to liver and stomach findings; read-across from the analogous substance 1,4-BDDMA (RTC 2013)

Subchronic (90 d) study; inhalation vapour, rat, m/f (OECD guideline 413, GLP); NOAEClocal= 100 ppm (352 mg/m3) due to local irritation effects in the respiratory epithelium; NOAECsystemic= 100 ppm (352 mg/m3) due to reduced bw gain; read-across from the metabolite MAA (BASF 2008)

Chronic (2 yrs) study; oral (drinking water), rat, m/f (pre-guideline, pre-GLP): NOAEL ≥ 2000 ppm (=124 mg/kg bw/d in males and 164 mg/kg bw/d in females); read-across from the metabolite donor substance MMA (Borzelleca 1964)

Chronic/ Carcinogenicity (2 yrs) study; inhalation (vapour), rat, m/f (comp. to OECD guideline 453, non-GLP): LOAEClocal= 100 ppm (ca. 416 mg/m3) due to nasal lesions; NOAECsystemic= 400 ppm (ca. 1640 mg/m3) due to reduced bw gain read-across from the metabolite donor substance MMA (Lomax 1997)

Chronic/ Carcinogenicity (2 yrs) study; inhalation (vapour), rat, m/f (NTP protocol, GLP): LOAEClocal= 250 ppm for female rats and 500 ppm for male rats due to nasal lesions; NOAECsystemic≥ 500 ppm for female rats and ≥ 1000 ppm male rats; read-across from the metabolite donor substance MMA (NTP 1986)

Subacute (28 d) study; oral (gavage), rat, m/f (OECD guideline 407, GLP); NOEL = 1000 mg/kgbw/d; read across from the alcohol metabolite 1,6 -HD (OECD 2002)

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study well documented, meets generally accepted scientific principles, acceptable for assessment.

Qualifier:

equivalent or similar to guideline

Guideline:

other: not known

Principles of method if other than guideline:

Chronic, repeated dose study with exposure via drinking water

GLP compliance:

no

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: "young" (unspecified)
The  animals were individually housed and provided food (finely ground Purina Dog Chow Kibbled Meal; questionable information in the publication) ad libitum

Route of administration:

oral: drinking water

Vehicle:

unchanged (no vehicle)

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

polarographic analysis of monomer content

Duration of treatment / exposure:

104 weeks (2 years)

Frequency of treatment:

Daily, ad libitum

Remarks:

Doses / Concentrations:
6, 60 and 2000 ppm at the start of the study; raised after 5 months to 7, 70 and 2000 ppm (limited by palatability)
Basis:

Remarks:

Doses / Concentrations:
ca. 14, 137, 3360 ppm
Basis:
other: for females based on dietary equivalents of fluid consumption

Remarks:

Doses / Concentrations:
ca. 12, 115, 3210 ppm
Basis:
other: for males based on dietary equivalents of fluid consumption

No. of animals per sex per dose:

25

Control animals:

yes, concurrent no treatment

Details on study design:

Twenty-five male and female albino (Wistar) rats were administered 6, 60 or 2000 ppm of methyl methacrylate in the drinking water. The concentrations of the low- and mid-dose groups were increased to 7 and 70 ppm at the beginning of the fifth month of the study.
Prior to the start of the study, it was apparent that methyl methacrylate was volatilizing at the tip of the water bottles. A special design was employed to reduce the volatilization and measurements showed that the methyl methacrylate concentrations remained within 15% of nominal for 72 hours.
The low and medium concentrations in the water were selected with the expectation that the diet equivalents would approximate 10 and 100 ppm. The high concentration was selected following preliminary tests that indicated that this level would significantly depress fluid consumption.

Observations and examinations performed and frequency:

Body weights were measured prior to study initiation, at weeks 1, 3, 6, 13, 26, 52, 78 and 104. Food and water consumption was measured over a three day period at the end of one and four weeks, monthly through month six and during even months thereafter. Hematological measurements, including hematocrit, hemoglobin, total white and differential white cell counts, were obtained from five rats from each sex in each treatment level at three month intervals. Pooled urine samples were collected from five rats per sex from each treatment group every three months to evaluate urinary concentrations of reducing substances and proteins.

Sacrifice and pathology:

Semiquantitative tests for urinary concentrations of reducing substances and protein were performed on urines pooled from 5 rats/sex per group at three month intervals. At two years, survivors were sacrificed and organ to body weight measurements were made for heart, spleen, kidney, liver and testes. Tissues preserved from all animals on study included heart, lung, kidney, liver, urinary bladder, spleen, gastrointeric, skeletal muscle, bone marrow, skin, brain, thyroid, adrenal, pancreas, pituitary and gonad. Histopathology was conducted on all tissues collected except from animals in the low dose group.

Details on results:

Body weight depression observed at 2000 ppm did not persist beyond the first few weeks of the study. Significant depression of fluid consumption was observed at 2000 ppm, although this tended to regress at the end of the study. Individual observations of depressed food consumption tended to parallel periods of depressed growth. These effects were considered as temporary non-adverse effects.
There were significantly increased kidney weight ratios for female rats at 2000 ppm. Since no substance-related effects were reported from histopathologic examinations in the kidneys, this effect is not considered as biologically relevant.

Dose descriptor:

NOAEL

Effect level:

>= 124.1 mg/kg bw/day (actual dose received)

Sex:

male

Basis for effect level:

other: based on fluid consumption and body weight (see attached document)

Dose descriptor:

NOAEL

Effect level:

>= 164 mg/kg bw/day (actual dose received)

Sex:

female

Basis for effect level:

other: based on fluid consumption and body weight (see attached document)

Dose descriptor:

NOAEL

Effect level:

>= 2 000 other: ppm nominal

Sex:

male/female

Basis for effect level:

other: corresponding to ca. 3300 ppm in the diet on the basis of fluid and food consumption observations

Critical effects observed:

not specified

Mortality: A summary of the mortality data for methyl methacrylate is presented below.

Dose group (ppm)            Male           Female
Negative              (0)          12/25           9/25
                           6/7           7/25           7/25
          60/70          10/25           7/25
           2000          12/25          10/25

No statistical differences were noted in the mortality of the animals exposed to methyl methacrylate and those in the control group. A statistically significant decrease in body weight was observed in the first week for the female rats and in weeks one through three in the male rats administered 2000 ppm methyl methacrylate. Water consumption was reduced in the animals from the high-dose group; however, it was reported that this finding tended to regress towards the end of the study. Food consumption was not affected by the administration of methyl methacrylate in the drinking water. 

  

Hematologic values varied within normal ranges in all groups of rats throughout the study, and urine concentrations of protein and reducing substances showed no trends that appeared relatable to treatment.

Organ to body weight ratios obtained at sacrifice of 2-year survivors differed from the controls only in significantly increased kidney ratios in female rats receiving 2000 ppm of methyl methacrylate (controls 0.0082 ± 0.0019; treated 0.0094 ± 0.0011).

Histopathologic findings showed no abnormalities or lesions, in kind or incidence, not explicable on the basis of naturally occurring ones in this strain of rat at this age.

  

Diet equivalents of the test materials were calculated from the fluid and food consumption data.

In these calculations, corrections were not made for evaporation losses of the test materials from the drinking water, the orders of magnitude of which are given under methods described above (maximum 15%). Allowing for such losses, it would appear that the concentrations of test materials in the drinking water were equivalent to approximately 10, 100, and 3000 ppm in the diet.

Conclusions:

No relevant effects were observed up to the highest dose tested (2000 ppm, limited by palatability)

Executive summary:

No relevant effects were observed after exposure of rats in drinking water up to the highest dose tested (2000 ppm, limited by palatability).

Reference 2

Endpoint:

short-term repeated dose toxicity: oral

Remarks:

combined repeated dose and reproduction / developmental screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from 20 April to 25 June 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Italy s.r.l., San Pietro al Natisone (UD), Italy. Animals were bred by Harlan Laboratories Netherland - Kreuzelweg 53, 5961 NM Horst P.O. Box 6174 NL 5960 AD Horst (Netherlands).
- Age at study initiation: 9 to 10 weeks (day of allocation)
- Weight at study initiation: Males 279-280g ; Females 214-216g (day of allocation)
- Housing: 5 sex/cage
- Diet (e.g. ad libitum): ad libitum excepted for clinical pathology
- Water (e.g. ad libitum): ad libitum excepted for clinical pathology
- Acclimation period: circa 3 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22°C +/-2°C
- Humidity (%): 55% +/- 15%
- Air changes (per hr): 15 to 20 air changes per hour
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: from 26 April (day of allocation) to 25 June 2012

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

The test item was administered orally by gavage at a dose volume of 5 mL/kg body weight. Control animals received the vehicle alone at the same dose volume.
The required amount of 1,4-Butanediol dimethacrylate was suspended in the vehicle (corn oil) at the final concentrations of 20, 60 and 200 mg/mL. The formulations were prepared daily and the concentrations were calculated and expressed in terms of test item as supplied.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Prior to commencement of treatment, analysis was performed to confirm that the proposed formulation procedure was acceptable (check of concentration and homogeneity).
The stability was found to be 24 hours at room temperature in the concentration range of 20 to 200 mg/mL.
Samples of the formulations prepared on Weeks 1 and 6 (when all females were present) were also analysed to check the concentration and homogeneity.
The overall results of the analyses were within the limits of acceptance stated in RTC’s SOPs for concentration (90-110%) and homogeneity (CV <10%).
Chemical analysis was carried out by the Analytical Chemistry Department at RTC according to a validated method (RTC Study No. 90770), in the range from 1.0 to 200 mg/mL. The software used for this activity was the Empower® Pro build No. 2154.

Duration of treatment / exposure:

Males
Animals were dosed once a day, 7 days a week, for 2 consecutive weeks prior to pairing and thereafter through the day before necropsy.
Dose volumes were adjusted once per week for each animal according to the last recorded body weight.

Females
Animals were dosed once a day, 7 days a week, for 2 consecutive weeks prior to pairing and thereafter during pairing (up to Day 40 of pairing for female no. 90760079 which did not mate), post coitum (up to Day 26 for non pregnant females) and post partum periods until Day 3 post partum. Dose volumes were adjusted once per week for each animal according to the last recorded body weight.
During the gestation period, dose volumes were calculated according to individual body weight on Days 0, 7, 14 and 20 post coitum and on Day 1 post partum. Thereafter individual dose volumes remained constant.

Frequency of treatment:

Once daily

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

10 male and 10 female rats

Control animals:

yes

Details on study design:

This study design was in agreement with the procedures described in OECD Guideline no. 422 adopted on 22 March 1996 and subsequent revisions.
The test item was administered orally by gavage to parental animals at 5 mL/kg body weight.
The dosages, selected in consultation with the Sponsor, were 100, 300 and 1000 mg/kg/day.
The oral route was selected as it is a possible route of exposure of the test item in man.

Observations and examinations performed and frequency:

Mortality
Throughout the study, all animals were checked early in each working day and again in the afternoon. At weekends and Public Holidays a similar procedure was followed except that the final check was carried out at approximately mid-day.

Clinical signs
All clinical signs were recorded for individual animals.
Once before commencement of treatment and at least once daily during the study, each animal was observed and any clinical signs were recorded.
Observations were performed at the same time interval each day, the interval was selected taking into consideration the presence of post-dose reactions.

Clinical observations (Functional Observation Battery Tests)
Once before commencement of treatment and at least once a week thereafter, each animal was given a detailed clinical examination. Each animal was
removed from the home cage and observed in an open arena. The tests included observation of changes in gait and posture, reactivity to handling, presence of clonic or tonic movements, stereotypies or bizarre behaviour and effects on the autonomic nervous system (e.g. lachrymation, piloerection, pupil size, unusual respiratory pattern).
All observations were recorded for individual animals.

Grip strength and sensory reactivity to stimuli
Once during the study, towards the end of treatment, 5 males and 5 females were randomly selected from each group for evaluation of sensory reactivity to stimuli of different modalities (e.g. auditory, visual and proprioceptive stimuli) and for assessment of grip strength. Measurements were performed using a computer generated random order. For males the tests were performed 4 days before necropsy and for females on Day 3 post partum.

Motor activity assessment (MA)
Once during the study, towards the end of treatment, 5 males and 5 females were randomly selected from each group and the motor activity was measured (for approximately 5 minutes) by an automated activity recording device. For males the tests were performed 4 days before necropsy and for females on Day 3 post partum.

Food consumption
The weight of food consumed by each cage of males and females was recorded weekly during the pre-mating period following allocation. The interval between allocation and treatment initiation was less than a full week. Individual food consumption for the females was measured on Days 7, 14 and 20 post coitum starting from Day 0 post coitum and on Day 4 post partum starting from Day 1 post partum.

Body weight
Males were weighed on the day of allocation to treatment groups, on the day of treatment commencement, weekly thereafter and at termination. Females were weighed on the day of allocation to treatment groups, on the day of treatment commencement, weekly thereafter until pairing and on Days 0, 7, 14 and 20 post coitum. Dams were also weighed on Days 1 and 4 post partum.

Clinical pathology investigations
As a part of the sacrificial procedure, samples of blood were withdrawn under isofluorane anaesthesia from the abdominal vena cava from 5 males and 5 females (all females with viable litters with the exception of one not pregnant female of Group 4) randomly selected from each group, under condition of food deprivation.
The blood samples collected were divided into tubes as follows:
EDTA anticoagulant for haematological investigations
Heparin anticoagulant for biochemical tests
Citrate anticoagulant for coagulation tests

Haematology
Haematocrit
Haemoglobin
Red blood cell count
Reticulocyte count
Mean red blood cell volume
Mean corpuscular haemoglobin
Mean corpuscular haemoglobin concentration
White blood cell count
Differential leucocyte count
- Neutrophils
- Lymphocytes
- Eosinophils
- Basophils
- Monocytes
- Large unstained cells
Platelets
Coagulation tests
Prothrombin time

Clinical chemistry
Alkaline phosphatase
Alanine aminotransferase
Aspartate aminotransferase
Gamma-glutamyltransferase
Urea
Creatinine
Glucose
Triglycerides
Bile acids
Phosphorus
Total bilirubin
Total cholesterol
Total protein
Albumin
Globulin
A/G Ratio
Sodium
Potassium
Calcium
Chloride

Urinalysis (Only males)
At the same time interval as the clinical pathology investigations, individual overnight urine samples were also collected from the same animals under the same conditions. Before starting urine collection, water bottles were removed from each cage and each animal received approximately 10 mL/kg of drinking water by gavage, in order to obtain urine samples suitable for analysis.

Appearance
Volume
Specific gravity
pH
Protein
Glucose
Ketones
Bilirubin
Urobilinogen
Blood

The sediment, obtained from centrifugation at approximately 3000 rpm for 10 minutes, was examined microscopically for:

Epithelial cells
Leucocytes
Erythrocytes
Crystals
Spermatozoa and precursors
Other abnormal components

Sacrifice and pathology:

Parental males:
The males were killed after the mating of all females (after 33 days of treatment).

Parental females:
The females with live pups were killed on Day 4 post partum.
The clinical history of the males and females of the parental generation was studied and a detailed post mortem examination was conducted (including examination of the external surface and orifices).
Changes were noted, the requisite organs weighed and the required tissue samples preserved in fixative and processed for histopathological examination.

Females:
All females were examined also for the following:
a) external and internal abnormalities;
b) number of visible implantation sites (pregnant animals);
c) number of corpora lutea (pregnant animals).
Organ weights

From all animals completing the scheduled test period, the organs were dissected free of fat and weighed.
The ratios of organ weight to body weight were calculated for each animal.

Tissues fixed and preserved

Samples of all the tissues listed in Annex 1 were fixed and preserved in 10% neutral buffered formalin (except testes and epididymides which were fixed in modified Davidson's fluid and preserved in 70% ethyl alcohol).

Histopathological examination

After dehydration and embedding in paraffin wax, sections of the tissues were cut at 5 micrometer thickness and stained with haematoxylin and eosin.
In addition, the testes and epididymides were cut at 2-3 micrometer thickness and stained with Periodic Acid Schiff (PAS). The morphological evaluationof the seminiferous epithelium (staging of spermatogenic cycle) was performed.

In the first instance the examination was restricted as detailed below:

a) Tissues from 5 males and 5 females randomly selected (animals evaluated for clinical pathology) in the control and high dose group.
b) All abnormalities in all groups.
The examination of stomach (both sexes) and liver (only females) was extended to include the remaining 5 males and 5 females (animals not evaluated for clinical pathology) of the control and high dose group.
In addition, the examination of stomach (both sexes) and liver (only females) was extended to animals of the other dose groups since possible treatment-related changes were observed in the high dose group.

Statistics:

Standard deviations were calculated as appropriate. For continuous variables the significance of the differences amongst group means was assessed by Dunnett’s test or a modified t test, depending on the homogeneity of data.
Statistical analysis of histopathological findings was carried out by means of the non-parametric Kolmogorov-Smirnov test (for stomach and liver).
The non-parametric Kruskal-Wallis analysis of variance was used for the other parameters. Intergroup differences between the control and treated groups were assessed by the non-parametric version of the Williams test.
The criterion for statistical significance was p<0.05 or p<0.01.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weight and body weight gain were lower in the high dose group compared to controls throughout the study.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Food consumption was reduced in the high dose group compared to controls.

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

The main relevant change was an increased value of bile acids in treated groups compared to controls with a clear dose-relation in males.

Urinalysis findings:

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Treatment-related findings were limited to the high dosed animals and were seen in the stomach of both sexes and in the liver of the females only.

Histopathological findings: neoplastic:

no effects observed

Details on results:

Mortality and fate of females
No mortality occurred in the study.
A total of 8 females were found not pregnant at necropsy: one each in the control and low dose groups and 6 in the high dose group.
The number of females with live pups on Day 4 post-partum were: 9 in the control group, 9 in the low dose group, 10 in the mid-dose group and 4 in the high dose group.

Clinical signs and neurotoxicity assessment (Functional Observation Battery Tests)
No clinical signs of toxicological significance were reported.

Body weight and body weight gain
Body weight and body weight gain were lower in the high dose group compared to controls throughout the study.

Food consumption
Food consumption was reduced in the high dose group compared to controls.

Motor activity and sensory reaction to stimuli
No relevant differences were noted in all parameters investigated between control and treated groups.

Haematology
No changes of toxicological significance were found.

Clinical chemistry
The main relevant change was an increased value of bile acids in treated groups compared to controls with a clear dose-relation in males.

Urinalysis
No changes were recorded.

Oestrus cycle, reproductive parameters, pairing combination and mating performance
Measurements of oestrus cycle, pre-coital intervals and copulatory index did not show differences between treated and control groups. On the
contrary, fertility index was markedly reduced in the high dose group (40% compared to 90% of the control group).

Implantation, pre-birth loss data and gestation length of females
No significant differences were observed in the number of implantation, corpora lutea, total litter size, pre-implantation loss, pre-birth loss and
gestation length between control and treated groups.

Litter data and sex ratios
Reduced litter and mean pup weights were found in the high dose group compared to controls. The percentage of cumulative pup loss on Day 4 post partum starting from the total litter size at birth, was increased in the high dose group.
No differences were found in sex ratio between the groups.

Clinical signs of pups
Small pups were generally observed in all groups including the control group. Cold to touch and apparently no food intake were the signs noted in pups of the treated groups only.

Necropsy findings in decedent pups and in pups sacrificed on Day 4 post partum
No relevant differences were recorded in decedent pups between the groups.
No abnormalities were observed in pups sacrificed at term.

Terminal body weight and organ weights
Terminal body weight was lower in the high dose group compared to controls and this difference was statistically significant in females.
Statistically significant higher kidneys weight was observed in high dose males and females compared to controls. In addition, thymus weight was significantly decreased in high dose males.

Macroscopic observations
No treatment-related changes were noted at macroscopic examination.

Microscopic observations
Treatment-related findings were limited to the high dosed animals and were seen in the stomach of both sexes and in the liver of the females only.
Stomach (non-glandular): The treatment-related change seen in the high dosed animals (1/10 and 5/10, respectively in males and females), consisted of mild diffused hyperplasia of the squamous epithelium in the non-glandural stomach, which was associated with mild thickening (i.e., hyperkerathosis) of the keratin layer. This change was not associated with any indication of inflammation and/or ulceration
Liver: In 3/10 high dose animals (females), minimal degree of multifocal perilobular hepatocytic vacuolaiton, which is suggested to be consistent with fatty change, was noted. The vacuoles were of mixed type (i.e., micro- and macrovesicular) and no presence of inflammation and/or necrosis was noted.

Key result

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

clinical biochemistry

food consumption and compound intake

organ weights and organ / body weight ratios

Critical effects observed:

no

Conclusions:

On the basis of the results obtained in the study, the NOAEL (No Observed Adverse Effect Level) could be considered 300 mg/kg/day for males and females.

Executive summary:

 In a Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test according to OECD Guideline 422 (22 March 1996) 1,4-Butanediol dimethacrylate was administered to 10 Hsd: Sprague Dawley SD rats/sex/dose orally by gavage at dose levels of 0 (control), 100, 300 and 1000 mg/kg bw/d. The treatment schedule included 2 weeks before pairing, during pairing, post coitum and post partum periods up to day 3 post partum. Animals were administered for approximately 5 and 8 weeks for males and females, respectively.

 

No mortality occurred in the study. A total of 8 females were found not pregnant at necropsy: one each in the control and low dose groups and 6 in the high dose group.
The number of females with live pups on Day 4 post-partum were: 9 in the control group, 9in the low dose group, 10 in the mid-dose group and 4 in the high dose group.
No clinical signs of toxicological significance were reported.

Body weight and body weight gain were lower in the high dose group compared to controls throughout the study.
Food consumption was reduced in the high dose group compared to controls.No relevant differences were noted in all parameters investigated between control and treated groups.
No changes of toxicological significance were found.
The main relevant change was an increased value of bile acids in treated groups compared to controls with a clear dose-relation in males.
No changes were recorded in urinalysis.
Measurements of oestrus cycle, pre-coital intervals and copulatory index did not show differences between treated and control groups. On the contrary, fertility index was marked lyreduced in the high dose group (40% compared to 90% of the control group).
No significant differences were observed in the number of implantation, corpora lutea, total litter size, pre-implantation loss, pre-birth loss and gestation length between control and treated groups.
Reduced litter and mean pup weights were found in the high dose group compared to controls. The percentage of cumulative pup loss on Day 4 post partum starting from the total litter size at birth, was increased in the high dose group.
No differences were found in sex ratio between the groups.
Small pups were generally observed in all groups including the control group. Cold to touch and apparently no food intake were the signs noted in pups of the treated groups only.
No relevant differences were recorded in decedent pups between the groups.
No abnormalities were observed in pups sacrificed at term.
Terminal body weight was lower in the high dose group compared to controls and this difference was statistically significant in females.
Statistically significant higher kidneys weight was observed in high dose males and females compared to controls. In addition, thymus weight was significantly decreased in high dose males.
No treatment-related changes were noted at macroscopic examination.
Treatment-related findings at microscpopic observations were limited to the high dosed animals and were seen in the stomach of both sexes and in the liver of the females only.Stomach (non-glandular)
The treatment-related change seen in the high dosed animals (1/10 and 5/10, respectively in males and females), consisted of mild diffused hyperplasia of the squamous epithelium in thenon-glandural stomach, which was associated with mild thickening (i.e., hyperkerathosis) ofthe keratin layer. This change was not associated with any indication of inflammation and/orulceration.
In 3/10 high dose animals (females), minimal degree of multifocal perilobular hepatocytic vacuolaiton, which is suggested to be consistent with fatty change, was noted. The vacuoles were of mixed type (i.e., micro- and macrovesicular) and no presence of inflammation and/ornecrosis was noted.
Evaluation of the spermatogenic cycle did not show differences between the groups. Regular layering in the germinal epithelium was noted.

 

Conclusions

On the basis of the results obtained in the study, the NOAEL (No Observed Adverse Effect Level) for both general toxicity and reproduction/developmental toxicity could be considered 300 mg/kg/day for males and females.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

300 mg/kg bw/day

Study duration:

subacute

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Method and results sufficiently described, similar to OECD-guideline 453.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

GLP compliance:

no

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc. (Wilmington, USA)
- Housing: group-housed by sex in wire mesh cages (seven per cage)
- Diet (e.g. ad libitum): Purina Laboratory Chow
- Water (e.g. ad libitum): water unspecified
- Acclimation period: 19 d


ENVIRONMENTAL CONDITIONS
not reported

Route of administration:

inhalation

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

1. Original study (Reno FE, 1979):  The test substance was administered in 6000-liter inhalation chambers with pyramidal tops and bottoms, under  dynamic conditions of 1000 liters/minute of airflow. Control animals were exposed to filtered room air in the same manner as the treated animals. 
2. Re-Evaluation of the study (Lomax LG et al., 1997):  Animals were exposed to the test substance vapor in 6000 liter inhalation chambers under dynamic conditions of 1000  liters/minute of air flow. The control animals were exposed to filtered room air in a chamber with similar air-flow characteristics.  

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The concentration of MMA in each chamber was monitored, when possible, at hourly intervals during each 6-hr exposure using an Infrared 6-Station Analyzer (Wilks-Miran, Foxboro, MA, USA).

Duration of treatment / exposure:

2 years (104 weeks)

Frequency of treatment:

6 hr/day, 5 days / week

Remarks:

Doses / Concentrations:
25, 100 and 400 ppm (corresponding to ca. 0.10, 0.41 and 1.64 mg/L, respectively)
Basis:
nominal conc.

Remarks:

Doses / Concentrations:
25.0, 99.8 and 396.1 ppm
Basis:
analytical conc.

No. of animals per sex per dose:

70 males and 70 females were assigned to each of the four exposure groups (including the  control). 

Control animals:

yes, concurrent vehicle

Details on study design:

Post-exposure period: Not applicable

Observations and examinations performed and frequency:

1. Original study (Reno FE, 1979):
-NOTE: This study is also summarized with further evaluation of nasal passage microscopy in Lomax et al. (1997).
Methods: Groups of 70 male and 70 female (total animals = 280 males and 280 females) rats were randomly assigned to either a control or one of three test groups. The animals were group housed (7/cage) and provided food and water ad libitum, except during the exposure period. The animals were exposed to the test substance six hours a day five days per week for a total of 104 - 106 weeks. The test substance was administered in 6000-liter inhalation chambers with pyramidal tops and bottoms, under dynamic conditions of 1000 liters/minute of airflow. Control animals were exposed to filtered room air in the same manner as the treated animals. Concentrations of the test substance in each chamber were measured hourly during each exposure period using an infrared analyzer. Animals were observed daily for mortality and moribundity. Body weights and clinical observations were recorded prior to study initiation, weekly during weeks 1 though 12, biweekly from week 14 through 24, every fourth week from week 28 through 78 and biweekly from week 80 through 104. Ophthalmoscopic exams were performed on all rats prior to treatment using an indirect ophthalmoscope at weeks 13, 52 and 102.
2. Re-Evaluation of the study (Lomax LG et al., 1997): Animals: Three hundred male and 300 female rats were received from Charles River Breeding Laboratories, Inc. (Wilmington, MA, USA). Animals were maintained under quarantine for 19 days, during such time all rats were evaluated for clinical signs of disease and an ophthalmoscopic examination. Following the quarantine period, 70 males and 70 females were assigned to each of the four exposure groups (including the control). The animals were housed by sex in wire mesh cages (seven/cage). Animals were provided feed and water ad libitum, except during the exposure period. Exposure conditions: Animals were exposed to the test substance vapor in 6000 liter inhalation chambers under dynamic conditions of 1000 liters/minute of air flow. The control animals were exposed to filtered room air in a chamber with similar air-flow characteristics. Observations: All animals were observed for mortality and morbidity daily. Individual body weight data were collected at the start of the study, weekly for the first twelve weeks and biweekly to week 24, every fourth week to week 78 and biweekly until study termination (week 104). At such time, a more detailed evaluation of gross toxicity and tissue masses was performed. Ophthalmoscopic evaluations were conducted at weeks 13, 52 and 102.

Sacrifice and pathology:

1. Original study (Reno FE, 1979):
Blood samples were collected from ten males and ten females in each group at weeks 13, 52 and 102 and from ten males and ten females in the control and high-exposure group at weeks 26 and 78 for hematological evaluation via segmental amputation of the tail. The following parameters were examined: hematocrit, hemoglobin, erythrocyte count, erythrocyte morphology, total leukocyte count and differential leukocyte count. In addition, coagulation and prothrombin times were determined from all blood samples taken at 13, 52 and 104 weeks and from the samples collected from the control and high-exposure groups at week 78. Femoral bone samples were collected from all sacrificed animals at weeks 13 and 52 and from 10 animals/sex/group at termination. The number of myeloid and erythroid cells and the myeloid/erythroid ratios were determined. Blood samples were collected for clinical chemistry evaluations from the abdominal aorta of all animals sacrificed at weeks 13 and 51 and from ten males and ten females per group at study termination. The following parameters were evaluated: fasting glucose, blood urea nitrogen, serum glutamic pyruvic transaminase, alkaline phosphatase, total protein, total albumin, albumin/globulin ratio. In addition, total cholesterol and triglycerides were also determined from blood samples taken from all animals sacrificed at week 52 and from ten animals/sex/group at week 104. Twenty-four hour urine samples were collected from 10 animals/sex/group at weeks 13, 52 and 104 by individually housing the rats overnight in stainless steel cages. The following parameters were evaluated: appearance, pH, ketones, total protein, specific gravity, bilirubin, glucose and occult blood. Necropsy: Ten rats/sex/group were sacrificed by exsanguination after 13 and 52 weeks of exposure. Animals found moribund during the course of the study were sacrificed at the time of the observation. The remaining animals were sacrificed after 102-104 weeks of exposure to the test substance. A gross necropsy was performed on all animals that were sacrificed and most of the animals that died during the study. Brain, kidneys, lungs, spleen, thyroids, adrenals and testes/ovaries from each animal were weighed and the organ to body weight ratio was calculated. The following tissues were collected and preserved in formalin or Bouin's solution: brain, pituitary, thoracic spinal chord, esophagus, salivary glands, thyroids, lungs, thymus, heart, spleen, kidneys, adrenals, stomach, duodenum, ileum, jejunum, colon, skin, mesenteric lymph nodes, urinary bladder, ovaries, uterus, mammary gland costochondral junction, liver, sciatic nerve, skeletal muscle, pancreas, nasal turbinates, unusual lesions, eyes and the testes with epididymides. Intraperitoneal body fat was recorded without exception at week 52 and by exception at all subsequent intervals. Histopathology was performed on the brain, spinal cord, pituitary, thyroid, adrenal, heart, lung, spleen, liver kidney, and ovaries/testes from 10/animals/sex in the low- and mid-exposure groups; and the nasal turbinates of all low- and mid-level animals. Also, the adrenals, ovaries/testes, heart (with coronary vessels), kidneys, liver, lungs, nasal turbinates, pituitary and thyroid were evaluated from 10 animals/sex/group from the control and high-exposure groups sacrificed at weeks 13 and 52.

2. Re-Evaluation of the study (Lomax LG et al., 1997):
Blood samples were collected from 10 males and 10 females per dose group at weeks 13, 52 and 104 and 10 males and 10 females in the control and the high-dose group at weeks 26 and 78. The following hematological parameters were evaluated at each sampling interval: hematocrit, hemoglobin, red blood cells counts, erythrocyte counts, total white blood cell counts, erythrocyte morphology and prothrombin time. Bone marrow samples were collected from the femurs of all rats killed at week 13 and 52 and from 10 males and 10 females from each group at study termination. Blood also was obtained from the abdominal aorta of all rats killed at week 13, 52 and study termination. The following clinical chemistry parameters were evaluated: glucose, blood urea nitrogen, serum glutamic-pyruvic transaminase, alkaline phosphatase, total protein, total albumin, total cholesterol (except for week 13) and triglycerides (except for week 13). Twenty-four hour urine samples were collected from 10 animals per sex per group at weeks 13, 52 and 104. The following parameters were evaluated: appearance, pH, specific gravity, glucose, ketones, total protein, bilirubin, and occult blood. Necropsy: Ten rats per sex per group were sacrificed after 13 and 52 weeks of exposure. The remaining animals were sacrificed after 104 - 106 weeks of exposure. Necropsies were performed on all decedents. The brain, kidneys, lungs spleen, adrenal and thyroid glands and the testis or ovaries were weighed and the organ to body weight ratios were calculated. The following tissues were preserved in buffered 10% formalin: brain, pituitary, spinal cord, esophagus, salivary glands, thyroid glands with parathyroid, lungs, mediastinal lymph nodes, thymus, heart, aorta, larynx, spleen, kidneys, adrenals, stomach, duodenum, ileum, jejunum, colon, skin, mesenteric lymph nodes, urinary bladder, uterus, mammary gland, prostate, seminal vesicles, costochondral junction, liver, sciatic nerve, skeletal muscle, pancreas, nasal cavity and gross lesions. The eyes from all rats and the testes with epididymides were preserved in Bouin's fixative. Microscopic evaluations were made using the tissue listed above in the control and the high-dose groups at study termination. The brain, spinal cord, pituitary, thyroid, adrenal, heart, lung, liver, spleen, kidney, and ovaries/testes from 10 animals per sex in the low- and mid-dose groups and the nasal cavities from all animals in the low- and mid-dose groups were evaluated microscopically. Sections from the adrenals, testes or ovaries, heart, kidneys, pituitary, thyroids, liver, nasal cavities and lungs of control and high-dose animals were examined microscopically after the week 13 and 52 interim sacrifices. Following the issuance of the original report, tissue blocks of the nasal cavities from the animals killed at the terminal sacrifice and the control and high-dose group at week 13, were obtained and a composite cross-sectional map of representative nasal cavity lesions with the approximate distribution was prepared for the mid- and high-dose groups.

Statistics:

1. Original study (Reno FE, 1979): Data Analysis: Pairwise comparisons of the mean body weights from weeks 12, 24, 36, 48, 52, 60, 72, 78, 90 and 104 were conducted using the F test for equality of two variances and Student's t-test. Clinical laboratory data (except urinalysis and leukocyte differentials), terminal body weights and absolute and relative organ weights (organ/body weight) of all animals sacrificed at weeks 13, 52 and term were subjected to a preliminary test for equality of variance followed by one-way analysis using Bartlett's test for homogeneity and Snedecor and Cochran, respectively. When statistical significances were observed, an additional set of analyses was conducted using Scheffe's method for judging all contrast in analysis of variance.
2. Re-Evaluation of the study (Lomax LG et al., 1997): Data analysis: Pair-wise comparisons of the mean body weights were performed. Clinical laboratory data, with the exception of urinalysis and leukocyte differentials, terminal body weights and absolute and relative organ weights of all animals killed at weeks 13 and 52 and at study termination were subjected to a preliminary test for the equality of variance. To evaluate tumor incidence, Fisher's one-sided exact test was conducted between the control and high-dose groups. For all analyses, statistical significance was determined by a p value < 0.05.

Dose descriptor:

NOAEC

Remarks:

systemic (gross pathology histopathology, clinical effects)

Effect level:

ca. 1 640 mg/m³ air

Sex:

male/female

Basis for effect level:

other: corresponding to 400 ppm

Dose descriptor:

LOAEC

Remarks:

local effects (Histopathology, olfactory epithelium)

Effect level:

ca. 416 mg/m³ air

Sex:

male/female

Basis for effect level:

other: nasal lesions; corresponding to 100 ppm

Dose descriptor:

NOAEC

Remarks:

local effects (Histopathology, olfactory epithelium)

Effect level:

ca. 104 mg/m³ air

Sex:

male/female

Basis for effect level:

other: corresponding to 25 ppm

Critical effects observed:

not specified

1. Original study (Reno FE, 1979):

-----------------------------------

The mean analytical concentration was evaluated. The overall mean concentrations of MMA vapour were 25.0, 99.8 and 396.1 ppm for the 25, 100 and 400 ppm exposure groups, respectively.

 

Mortality: Mortality rates were relatively low through week 78. High mortality was observed through week 104. The author indicates that the increase in mortality was probably due to aging, not related to test substance exposure. The mortality rates for treated groups were comparable to the control group. A summary of the mortality rates (%) is provided below.

 

 

Dose group (ppm)	Week 0-13	Week 0-52	Week 0-104
MALES
Negative Control (0)	0	0	16
25	0	1.7	20
100	0	1.7	16
400	0	0	20
FEMALES
Negative Control (0)	0	0	24
25	0	3.3	36
100	1.4	3.3	26
400	0	5.0	30

 

Clinical signs

No signs of test substance-related toxicity were observed in any of the treated animals throughout the 104-week exposure period. The most frequent observations included cloudy eye(s) and bloody crust around one or both eyes. The author reported that these findings occurred with approximately the same frequencies in treated and control groups.

Body weight

Male body weights were significantly higher in the mid-level exposure group at week 24, lower weights in the low-level exposure group at week 104, and lower weights of the high-level exposure group at weeks 28 and 78. In the females, the low-level exposure groups showed a significant decrease in body weight at weeks 60, 72 and 78 and an increase at weeks 12 and 24. The females in the mid-level exposure group showed a significant decrease at weeks 52, 60 and 78 and in the high-level exposure group at weeks 28, 36, 52, 60, 72, 78 and 90. The author concluded, the body weight reduction observed in the females exposed to ca. 1.64 mg/L (400 ppm) MMA was test substance-related.

 

Ophthalmoscopy

Ophthalmoscopic observations were noted at weeks 13, 52 and 102. The author reports that no consistent ocular abnormalities were noted at weeks 13 and 52. Ocular findings noted at week 102 included cataracts, pale coloration, corneal cloudiness and red discharge. The cataract findings were considered to be caused by aging.

Haematology/ Clinical chemistry

Evaluation of the haematology and clinical chemistry data did not reveal any remarkable trends. Statistical analyses showed numerous significant differences between the treated and the control groups; however, these differences were considered sporadic and were considered by the author a reflection of sampling and biological variability. A transitory appearance of occult blood was observed in all groups at week 52. All remaining intervals were generally unremarkable.

 

Organ weights

A statistically significant increase in absolute and relative organ weights of the females exposed to ca. 1.64 mg/L (400 ppm) MMA was observed in the lungs, liver, kidneys, and ovaries at week 13. A statistically significant decrease in absolute and relative thyroid and adrenal weights were observed in both males and females in the high-level exposure group at week 52. Absolute thyroid and adrenal weights were significantly higher in the males exposed to ca. 0.41 mg/L (100 ppm), MMA for 52 weeks. Other significant differences were noted at weeks 52 and 104; however, the author concluded that no consistent dose-related pattern was established.

 

Gross pathology

Findings noted in animals that were sacrificed at weeks 13 and 52 were mainly discolorations of the lung and liver. None of the findings were considered treatment-related. Tissue mass findings for animals sacrificed at week 104 were typical for the age and the species of rats. No treatment-related differences with respect to the frequency were observed.

 

Histopathology 

Week 13

No treatment-related histopathological findings were noted in the rats exposed to ca. 1.64 mg/L (400 ppm) MMA for 13 weeks. Findings were consistent among groups and were typical for rats of this age and strain.

Week 52

No treatment-related histopathological findings were noted in the rats exposed to ca. 1.64 mg/L (400 ppm) MMA for 13 weeks. Findings were consistent among groups and were typical for rats of this age and strain.

Week 104

Treatment-related histopathological findings were limited to a very slight increase in the lesions of mild rhinitis observed in the mucosal lining of the nasal turbinates. A summary of the lesions is provided below.

 

Incidence of Lesions in Nasal Mucosa

 

	Males				Females
Group No.*	1	2	3	4	1	2	3	4
No. of Nasal Turbinates Examined	48	49	49	48	44	48	45	46
Serous Exudate	3	11	12	16	15	8	17	23
Purulent Exudate	2	6	4	8	2	9	6	6
Pleocellular Infiltrate	1	4	6	19	3	14	9	11
Distended Submucosal Glands	5	21	21	12	3	14	12	9
Squamous Metaplasia (focal)	2	3	1	5	0	5	1	2
Inflammatory Polyp	0	0	1	2	0	0	0	0

*Groups 1, 2, 3 and 4 were exposed to ca. 0, 0.10, 0.41 and 1.64 mg/L (0, 25, 100 and 400 ppm) MMA, respectively.

 

No clear treatment-related effect could be established. Although lesions of mild rhinitis occurred more often in treated rats than control rats, it could not be determined if the rhinitis was a result of direct chemical insult to the turbinate area or whether the presence of MMA vapors predisposed the rats to an increase in spontaneous disease. [NOTE - Subsequent evaluation of the nasal lesions (Lomax et al., 1997) indicated that there were exposure related nasal lesions at ca. 0.10 and 0.41 mg/L (100 and 400 ppm)]. Neoplasms and spontaneous disease lesions were observed with comparable frequency in control and treated rats. Chronic nephritis was observed in most rats; however, it was more pronounced in males.

 

2. Re-Evaluation of the study (Lomax LG et al. (1997)):

-------------------------------------------------------

 

The mean analytical concentrations of the test substance in the exposure chambers were 25.0, 99.8 and 396.1 ppm less than 10% per dose level.

 

Mortality rates for the treated animals were similar to those of the controls. No signs of treatment-related toxicity were observed. At the 13, 52 and 104-week observation intervals, cloudy eyes and bloody crusts around one or both eyes were noted in all of the treatment groups, as well as the control animals. Body weights for males were lower than the control at various intervals but overall were considered equivalent over the 104-week period. Mean body weights for females were lower than the controls at ca. 1.64 mg/L (400 ppm) after week 52. Haematology, clinical chemistry and urinalyses did not indicate any treatment-related effects in any of the parameters evaluated.

 

Gross necropsy of the rats sacrificed at weeks 13 and 52 did not show any treatment-related effects.

 

The following information was obtained from the reevaluation of the nasal tissues from this study originally conducted by Reno et al.(1979) - see also summary for this study in this Dossier. Microscopic evaluation of the nasal cavity sections obtained from the animals exposed to the test substance for 13 weeks showed degeneration of the neuroepithelial cell lining of the dorsal meatus in conjunction with atrophy of Bowman's glands and focal basal cell hyperplasia. Lesions were identified on the tips of the maxilloturbinates and nasoturbinates and focally along the nasal septum in the more anterior regions of the nose. These lesions were characterized by chronic active inflammation, respiratory epithelial hyperplasia and squamous metaplasia. No microscopic findings were identified in the ocular tissue or the lungs or other tissues. Blocks of the nasal cavities of animals from the 52-week sacrifice were unable to be located and, therefore, were not evaluated. No new findings were identified in the tissues that were available for animals exposed to the test substance for 52 weeks. Spontaneous disease lesions included early respiratory disease in both the control animals and the animals exposed to 400 ppm of the test substance. Also focal areas of pneumonitis were observed in two females in the control group.

Gross necropsy after two years of exposure to the test substance showed no treatment-related effects. The nasal cavity was the target organ for chronic toxicity. Rats exposed to the 100 and 400 ppm dose group had dose-dependent lesions in the anterior portions of the nasal cavity. The olfactory epithelium lining the dorsal meatus in the anterior region of the nasal cavity was affected by exposure to higher concentrations of the test substance. The microscopic changes consisted of degeneration of the olfactory epithelium and underlying Bowman's glands, hyperplasia of basal cells, replacement of olfactory epithelium by ciliated epithelium and inflammation of

the mucosa and/or submucosa. Lesions tended to be bilateral in distribution. The olfactory lesions in rats exposed to 100 ppm were localized in the more posterior (level 3) portion of the dorsal meatus, while those in animals exposed to ca. 1.64 mg/L (400 ppm) were found in levels 2 and 3. Hyperplasia of glands in the lamina propria and/or goblet cells and inflammation of the mucosa/lamina propria were observed in the respiratory epithelium in the high exposure group animals. No effects were seen in nasal epithelium of rats exposed to ca. 0.10 mg/L (25 ppm) MMA. No statistically significant differences were observed in the frequency of tumours between the rats exposed to ca. 1.64 mg/L (400 ppm) of the test substance and that of the controls. In female rats exposed to ca. 1.64 mg/L (400 ppm) of the test substance, a statistically significant decrease in pituitary adenoma/carcinomas and mammary gland fibroadenomas was recorded. In male rats, a decreased incidence of pheochromocytoma was observed.

Reference 2

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

Age when supplied; sex: about 7 weeks, male and female
Supplier: Charles River Laboratories, Research Models and Services, Germany GmbH; Sandhofer Weg 7, 97633 Sulzfeld
During the period when the rats were not exposed they were housed singly in wire cages (type DK III, Becker & Co., Castrop-Rauxel, FRG (floor area about 800 cm²)). Underneath the cages, waste trays were fixed containing bedding material (Type Lignocel FS14 fibres,
dustfree bedding supplied by SSNIFF, Soest, Germany)
The motor activity measurements were conducted in Polycarbonate cages with wire covers from Ehret, Emmendingen, FRG (floor area about 800 cm²) and bedding.
The animals were kept in fully air-conditioned rooms in which a temperature in the range of 20 - 24°C and relative humidity in the range of 30 - 70% were ensured by means of a central air-conditioning system.
A light/dark rhythm of 12 hours was maintained.
The room was completely disinfected using a disinfector ("AUTEX", fully automatic, formalinammonia-based terminal disinfector) before the start of the study. Usually, each week the floor and the walls were cleaned with water containing about 1 % Mikroquat®.
The animals were maintained on milled mouse/rat laboratory diet “GLP”, (Provimi Kliba SA, Kaiseraugst, Basel Switzerland) and tap water ad libitum.

Route of administration:

inhalation

Type of inhalation exposure:

whole body

Vehicle:

air

Details on inhalation exposure:

For each concentration, the test substance was supplied to the two-component atomizer of a thermostated vaporizer at a constant rate by means of the piston metering pump. The vapor was generated by spraying the substance with compressed air into a counter current of conditioned supply air (about 50% ± 20% relative humidity, 22°C ± 2°C). Thereafter it was further mixed with conditioned supply air and passed into the inhalation system.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The concentrations of the inhalation atmospheres in test groups 1 - 4 were analyzed by HPLC.

Duration of treatment / exposure:

90 days

Frequency of treatment:

6 hours/day, 5 days/week

Dose / conc.:

20 ppm

Remarks:

= 70 mg/m3

Dose / conc.:

40 ppm

Remarks:

= 141 mg/m³

Dose / conc.:

100 ppm

Remarks:

= 352 mg/m³

Dose / conc.:

350 ppm

Remarks:

= 1232 mg/m³

No. of animals per sex per dose:

10/sex/dose

Control animals:

yes, sham-exposed

Details on study design:

Ten male and ten female Sprague Dawley rats per test group were whole body exposed to a vapor of the test substance on 6 hours per working day for 90 days (65 exposures). The target concentrations were 20, 40, 100 and 350 ppm (corresponding to 70, 141, 352 and 1232 mg/m3). A concurrent control group was exposed to conditioned air.

Observations and examinations performed and frequency:

The animals were examined for evident signs of toxicity or mortality twice a day (in the morning and in the late afternoon) from Mondays to Fridays and once a day (in the morning) on Saturdays, Sundays and public holidays. The clinical condition of the test animals was recorded once during the preflow period and on post-exposure observation days and at least 3 times (before, during and after exposure) on exposure days.
During exposure only a group wise examination was possible.The body weight of the animals was determined at the start of the preflow, at the start of the exposure period and then, as a rule, once a week as well as one day prior to gross necropsy. As a rule, the animals were weighed at the same time of the day.
Body weight change was calculated as the difference between body weight on the respective exposure day and body weight on the day of the first exposure. Group means were derived from the individual differences.
Food consumption was determined weekly and calculated as mean food consumption in grams per animal and day.Food efficiency (group means) was calculated based upon individual values for body weight and food consumption.
Before the start of the exposure period (day -6) the eyes of all animals, and at the end of the study (day 82) the eyes of the animals of test group 0 (control group) and test group 4 (high concentration) were examined with an ophthalmoscope (HEINE Optotechnik, Herrsching, FRG)) for any changes in the refracting media.
Functional observation battery (FOB) was carried out on the assigned animals once before the exposure period and once against the end of the exposure period.Motor activity was measured on the same day and with the same animals as FOB was performed.

Sacrifice and pathology:

In the morning, blood was taken from the retro-orbital venous plexus from fasted animals. The animals were anaesthetized using isoflurane (Isoba®, Essex GmbH Munich, Germany). The blood sampling procedure and the subsequent analysis of the blood and serum samples were carried out in a randomized sequence. For urinalysis the individual animals were transferred to metabolism cages (withdrawal of food and water) and urine was collected overnight. The urine samples were evaluated in a randomized sequence. At necropsy specimen were sampled from fasted anesthetized male animals in a randomized sequence for sperm analyses.
Hematological parameters were determined in blood with EDTA-K3 as anticoagulant using a particle counter (Advia 120 model; Bayer, Fernwald, Germany): Furthermore differential blood smears were prepared and stained according to Wright without being evaluated.
An automatic analyzer (Hitachi 917; Roche, Mannheim, Germany) was used to examine the clinicochemical parameters.
With the exception of volume, color, turbidity, sediment examination and the specific gravity, all the urine constituents were determined semi-quantitatively using test strips (Combur-9-test M, Roche, Mannheim, Germany) and a reflection photometer (Miditron M; Roche, Mannheim, Germany).
Immediately after necropsy and organ weight determination the right testis and cauda epididymis were taken from all male animals.
Sperm motility examinations were carried out in a randomized sequence. Sperm morphology and sperm head count (cauda epididymis and testis) were evaluated for the control and highest dose group, only.
The animals were killed under Narcoren anesthesia by exsanguination from the abdominal aorta and vena cava. The animals were then be necropsied and subjected to a grosspathological assessment. Animals that died intercurrently or were killed in a moribund state were necropsied and assessed by gross-pathology as quickly as possible.

Statistics:

DUNNETT, C.W. (1955): A multiple comparison procedure for comparing several treatments with a control. JASA, Vol. 50, 1096– 1121
DUNNETT, C.W. (1964). New tables for multiple comparisons with a control. Biometrics, Vol. 20, 482 –491
SIEGEL, S. (1956): Non-parametric statistics for the behavioural sciences. McGraw-Hill New York
Nijenhuis, A.; Wilf, H.S.(1978): Combinatorial Algorithms. AcademicPress New York, 32-33
Hettmansperger, T.P. ( 1984); Statistical Inference based on Ranks. John Wiley & Sons New York, 132-142
International Mathematical and Statistical Libraries, Inc., 2500 Park West Tower One, Houston, Texas 77042-3020, USA, nakl-1 -nakl-3
MILLER, R.G. (1981): Simultaneous Statistical Inference Springer-Verlag New York Inc., 165-167

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Details on results:

Subchronic vapor inhalation of the test substance led to the following treatment-related
adverse effects:
Test group 4 (350 ppm):
􀂾 Decreased body weight of the males (- 6.1% to - 12.8%) from study day 7 onward
􀂾 Decreased body weight change (gain) of the males (- 28.5% to - 64.8%) from study
day 7 onward
􀂾 Decreased food consumption in the male animals on study days 7 (- 13.5%),
14 (- 12.2%), and from study day 28 through to day 84 (from - 9.4% to - 13.7%)
􀂾 Decreased food efficiency in the male animals on study days 7, 28, 49 and 56
􀂾 Decrease of terminal body weights in both sexes
􀂾 Goblet cell hypertrophy/hyperplasia in the respiratory epithelium of the nasal cavity
(level I) of two females
Test group 1 (20 ppm), test group 2 (40 ppm) and test group 3 (100 ppm):
􀂾 No treatment-related findings

Dose descriptor:

NOAEC

Remarks:

systemic effects

Effect level:

100 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

food consumption and compound intake

food efficiency

Remarks on result:

other: = 352 mg/3

Dose descriptor:

NOAEC

Remarks:

local effects

Effect level:

100 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

Remarks on result:

other:

Remarks:

= 352 mg/3

Dose descriptor:

LOAEC

Effect level:

350 ppm

Sex:

male/female

Basis for effect level:

body weight and weight gain

food consumption and compound intake

food efficiency

Remarks on result:

other: = 1232 mg/m3

Dose descriptor:

LOAEC

Remarks:

local effets

Effect level:

350 ppm

Based on:

test mat.

Sex:

female

Basis for effect level:

histopathology: non-neoplastic

Remarks on result:

other: = 1232 mg/m3

Critical effects observed:

not specified

Conclusions:

In a valid guideline study, the the no-observed adverse effect level (NOAEL) is 100 ppm for the male and female rats exposed by whole body inhalation for 90 days.

Executive summary:

In a valid guideline study acc OECD 413 ( Subchronic inhalation toxicity: 90 day exposure of rats) methacrylic acid induced signs of general toxicity as indicated by descreased body weight, body weight gain, food consumption and transiently food efficiency in the high concentration male animals. At a concentration as high as 350 ppm (1232 mg/m³), the local irritating effect was marginal, indicated by the hypertrophy/hyperplasia of the respiratory epithelium in the nasal cavity of two female animals. Substance-related changes of the sexual organs were not noted in any of the exposed animals, nor were there any changes of sperm mobility and sperm head counts. Under the current test conditions, the no-observed adverse effect level (NOAEL) in this study is 100 ppm (352 mg/m³) for the male and female rats.

NOTE: Any of data in this dataset are disseminated by the European Union on a right-to-know basis and this is not a publication in the same sense as a book or an article in a journal. The right of ownership in any part of this information is reserved by the data owner(s). The use of this information for any other, e.g. commercial purpose is strictly reserved to the data owners and those persons or legal entities having paid the respective access fee for the intended purpose.

Reference 3

Endpoint:

chronic toxicity: inhalation

Remarks:

combined repeated dose and carcinogenicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: NTP standard protocol, cancer bioassay with limited dose range

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

air

Remarks on MMAD:

MMAD / GSD: vapour

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

2 years

Frequency of treatment:

6 h / day, 5 d / wk

Remarks:

Doses / Concentrations:
0, 500, 1000 ppm for males
Basis:
other: analytically confirmed nominal concentrations

Remarks:

Doses / Concentrations:
0, 250, 500 ppm for females
Basis:
other: analytically confirmed nominal concentrations

No. of animals per sex per dose:

50

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: random (table)
- Dose selection rationale: Based on the results of several preliminary studies up to 90 d duration

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: 2/d

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: at weighing

BODY WEIGHT: Yes
- Time schedule for examinations: weekly for the first 13 weeks, monthly afterwards

FOOD CONSUMPTION, FOOD EFFICIENCY and WATER CONSUMPTION: no data
HAEMATOLOGY, CLINICAL CHEMISTRY, URINALYSIS, NEUROBEHAVIOURAL EXAMINATION: No data

Sacrifice and pathology:

GROSS PATHOLOGY and HISTOPATHOLOGY: Yes

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

URT

Histopathological findings: neoplastic:

no effects observed

Description (incidence and severity):

no relevant effect in all investigated tissues

Dose descriptor:

LOAEC

Remarks:

for local effects in the URT (no NOAEC identified)

Effect level:

250 ppm

Based on:

test mat.

Sex:

female

Basis for effect level:

other: Histopathology (Irritation)

Dose descriptor:

NOAEC

Remarks:

for systemic effects

Effect level:

500 ppm

Based on:

test mat.

Sex:

female

Basis for effect level:

other: Gross pathology, Histopathology (organ effects)

Dose descriptor:

NOAEC

Effect level:

1 000 ppm

Based on:

test mat.

Sex:

male

Basis for effect level:

other: Gross pathology, Histopathology (organs)

Critical effects observed:

not specified

Mortality: No difference in survival between treated and untreated groups.

Histopathology:

Site / Lesion Males	Control [0 ppm]	Low. Conc. [500 ppm]	High Conc. [1000 ppm]
Nasal Cavity /            Serous inflammation            Suppurative inflammation	0/50 11/50	37/50 21/50	44/50 30/50
Olfactory sensory epithelium /            Degeneration	7/50	39/50	42/50
Lung /            Alveolar macrophages            Focal or multifocal fibrosis	6/49  6/49	20/49  6/49	16/50  5/50
Site / Lesion Females	Control [0 ppm]	Low. Conc. [250 ppm]	High Conc. [500 ppm]
Nasal Cavity /            Serous inflammation            Suppurative inflammation	4/50 7/50	17/50 12/50	32/50 12/50
Olfactory sensory epithelium /            Degeneration	2/50	39/50	44/50
Lung /            Alveolar macrophages            Focal or multifocal fibrosis	9/50 1/50	14/50  2/50	16/50  7/50

 

No histopathological findings other than local findings in the respiratory tract. Systemic histopathological effects, as for example in the brain in females particularly at 2000 ppm and above in the subchronic range finding study (Batelle, 1980), are absent in this 104 week study.

Body weight: Mean body weight gain was reduced in females at 500 ppm resulting in 6 -11% lower body weights after week 73 and in males at 1000 ppm which were 5 -10 % lower than controls after week 81.

There was no treatment-related increase in tumour incidence.

Conclusions:

The primary finding in this study was inflammation of rat nasal cavity as well as olfactory epithelial degeneration at all exposure levels in male and female rats. For local effects the LOAEC was 250 ppm in this study while a NOAEC could not be found. 
In contrast to the 90 d range finding study with histopathological changes in females at exposures of 1000 ppm and above (Battelle, 1980), no other significant histopathological changes were reported in male and female rats after 104-week exposures to MMA vapour in this study. Based on this a NOEC for systemic effects of 500 ppm is derived.

Executive summary:

In this104-week study with groups of 50 animals each, male rats were treated with MMA vapour by whole-body exposure to 500 or 1000 ppm while female rats were exposed to 250 or 500 ppm.

 

The primary finding was inflammation of rat nasal cavity as well as olfactory epithelial degeneration at all exposure levels in male and female rats. For local effects the LOAEC was 250 ppm in this study while a NOAEC could not be found. 

In contrast to the 90 d range finding study with histopathological changes in females at exposures of 1000 ppm and above (Battelle, 1980), no other significant histopathological changes were reported in male and female rats after 104-week exposures to MMA vapour in this study. Based on this a NOEC for systemic effects of 500 ppm is derived.

 

Male and female rat body weights were lower at the 1000 ppm (5-10%) and 500 ppm (6-11%) exposure levels, respectively, presumably due to reduced food consumption due to nasal irritation and damage of olfactory epithelium. While food consumption was not recorded in this study this association is confirmed by two other studies, the developmental toxicity study with MMA with reduced food consumption and reduced body weight gain at concentrations higher than 99 ppm (Solomon, 1993) and a subchronic inhalation study with methacrylic acid where there was also an association of irritative effects in the nose and reduced food consumption and reduced body weight gain (BASF, 2008). Consequently, reduced body weight gain, while clearly treatment-related - is considered to be secondary to the local effects in the nose and not the result of true systemic toxicity.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

416 mg/m³

Study duration:

chronic

Species:

rat

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

No study is available for 1,6-HDDMA. Reliable, relevant and adequate studies are however available on repeated dose toxicity conducted with the structurally closely related analogous 1,4-BDDMA, and the primary metabolites MAA/MMA after oral and inhalative exposure and 1,6 -Hexanediol (1,6 -HD) as follows. Like other investigatedsubstances from this category, 1,6-HDDMA is expected to be rapidly hydrolysed by carboxylesterasesto methacrylic acid (MAA) and the respective alcohol 1,6-HD. The read across is justified in detail in the attached category document.

 

In a Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test according to OECD Guideline 422 (22 March 1996), 1,4-BDDMA was administered to groups of 10 Hsd: Sprague Dawley SD rats/sex/dose orally by gavage at dose levels of 0 (control), 100, 300 and 1000 mg/kg bw/d. The treatment schedule included 2 weeks before pairing, during pairing, post coitum and post partum periods up to day 3 post partum. Animals were administered for approximately 5 and 8 weeks for males and females, respectively.

No mortality occurred in the study. No clinical signs of toxicological significance were reported. Body weight and body weight gain as well as food consumption were lower in the high dose group compared to controls throughout the study.

No relevant differences were noted in motor activity and sensory reaction to stimuli between control and treated groups. Haematology and urin analysis revealed no changes of toxicological significance. The main relevant change in clinical chemistry was an increased value of bile acids in treated groups compared to controls with a clear dose-relation in males.

Measurements of oestrus cycle, pre-coital intervals and copulatory index did not show differences between treated and control groups. No significant differences were observed in the number of implantation, corpora lutea, total litter size, pre-implantation loss, pre-birth loss and gestation length between control and treated groups.

On the contrary, fertility index was markedly reduced in the high dose group (40% compared to 90% of the control group).

Reduced litter and mean pup weights were found in the high dose group compared to controls. The percentage of cumulative pup loss on Day 4 post partum starting from the total litter size at birth, was increased in the high dose group. No differences were found in sex ratio between the groups.

Small pups were generally observed in all groups including the control group. Cold to touch and apparently no food intake were the signs noted in pups of the treated groups only. No relevant differences were recorded in decedent pups between the groups. No abnormalities were observed in pups sacrificed at term.

At necropsy statistically significant higher kidneys weight was observed in high dose males and females compared to controls. In addition, thymus weight was significantly decreased in high dose males. No treatment-related changes were noted at macroscopic examination.

Treatment-related microscopic findings were limited to the high dosed animals and were seen in the stomach of both sexes and in the liver of the females only.

Stomach (non-glandular):

The treatment-related change seen in the high dosed animals (1/10 and 5/10, respectively in males and females), consisted of mild diffused hyperplasia of the squamous epithelium in the non-glandural stomach, which was associated with mild thickening (i.e., hyperkerathosis) of the keratin layer. This change was not associated with any indication of inflammation and/or ulceration

Liver:

In 3/10 high dose animals (females), minimal degree of multifocal perilobular hepatocytic vacuolaiton, which is suggested to be consistent with fatty change, was noted. The vacuoles were of mixed type (i.e., micro- and macrovesicular) and no presence of inflammation and/or necrosis was noted.

 

Slight toxic effects were seen in parental animals as indicated by the reduced body weight, body weight gain and food consumption in the animals receiving 1000 mg/kg bw/d. The reduced mean litter/pup weights in the high dose group may be related to the maternal toxicity.

Concerning the reproductive parameters, the fertility appeared to be treatment-related as indicated by the reduced number of pregnant females in the high dose group respect to the control group.

On the basis of the results obtained in the study, the NOAEL for both, general toxicity and reproduction /developmental toxicity was 300 mg/kg bw/d (males/females).  

The observed effects in the high dose group were only slight indicating only little likelihood that effects of greater severity at the same effect doses or effects at lower doses would occur in studies of longer duration (e.g. 90 day study). In addition, 1,4-BDDMA is considered as the category substance with an alcohol metabolite (1,4-Butanediol) owing a clear toxicological profile (neurobehaviour). Such clear toxicological properties are not known for 1,6-HD as the alcohol metabolite of 1,6-HDDMA.

Thus, when using the study of the analogous substance 1,4-BDDMA and the default ECHA assessment factor = 6 for extrapolation from subacute to chronic exposure, several uncertainties are considered as covered for DNEL derivation of 1,6-HDDMA.

 

MAA (common primary methacrylic metabolite of all category substances)

In an OECD 413, 90-day vapour inhalation study in Sprague Dawley rats, MAA revealed general toxicity at 350 ppm (1253 mg/m3, the highest tested dose) in male animals (BASF, 2008). Local, marginal irritation of the respiratory epithelium in the nasal cavity was observed in two female animals. No changes in sexual organs or sperm mobility and sperm head counts were noted. The NOAEC was 100 ppm (352 mg/m3) for local irritation effects in male and females The NOAEC for systemic effects based upon reduced body weight gain in the presence of reduced feed intake but no other systemic effects was also 100 ppm (352 mg/m3) in male and females.

 

MMA (donor substance for the common primary metabolite MAA)

In an early 2-year chronic drinking water study with 25 male and 25 female rats administered with 6, 60 and 2000 ppm MMA no adverse effect were observed other than elevated kidney weights without corresponding histopathology in female rats at 2000 ppm (Borzelleca et al., 1964). The NOAEC was reported as 2000 ppm (124 and 164 mg/kg bw/d) in male and female rats.

--

EU ESR on MMA (2002) concluded: “The combined chronic toxicity/carcinogenicity study of methyl methacrylate in F344 rats (Rohm and Haas, 1979a; the nasal tissues were reevaluated by Lomax, 1992; Lomax et al., 1997) was assessed for the requirements of the regulation 793/93/EEC as a valid study with restrictions. In comparison to the minimal requirements of a 28-day inhalation study (OECD 412), the list of organs to be weighted did not include the liver and the heart. 70 male and 70 female f 344 rats were exposed to vapor concentrations of 0, 25, 100 or 400 ppm methyl methacrylate for two years. Ten male and ten female rats from all groups were sacrificed after 13 and 52 weeks of exposure and all surviving rats were killed during week 104-106. Histological examination was conducted on more than 35 tissues including 3-4 cross-sections of the nasal cavity. Tissues from the trachea and the pharynx/larynx were not preserved for histopathologic examination. Mortality rates of treatment and control groups did not show significant differences. No compound-induced clinical signs were observed. After week 52, mean body weight of high dose females was generally lower than controls gaining intermittently significance. Reduced growth represented the only adverse effect outside the respiratory 'tract. Evaluation of hematology, clinical chemistry and urinalysis data did not reveal any methyl methacrylate associated effect.

At the end of the study, there were weight changes of some organs in males or females without any consistent relationship to the treatment. Similarly, no treatment-related macroscopic findings were observed in any of the dose groups. No histomorphological lesions other than nasal lesions were attributable to methyl methacrylate exposure of any exposed group. The examination of nasal cavities from male and female rats exposed to 400 ppm for 13 weeks or 52 weeks revealed a degeneration of the neuroepithelial olfactory cells lining the dorsal meatus of the anterior portions of the nasal cavities in conjunction with atrophy of Bowman's glands and focal basal cell hyperplasia. Chronic active inflammation, respiratory epithelial hyperplasia and squamous metaplasia characterized the lesions on the tips of the maxilloturbinate and nasoturbinats and focally along the nasal septum in more anterior regions of the nose. At the final sacrifice, nasal lesions were evident in males and females of the 100 ppm and 400 ppm exposure groups characterised by inflammatory degeneration of nasal epithelium. The primary target tissue was the olfactory epithelium with degeneration and/or atrophy of neurogenic epithelium and submucosal (Bowman's) glands lining the dorsal meatus, hyperplasia of basal cells, replacement of olfactory epithelium with ciliate (respiratory like) epithelium (metaplasia), and inflammation of the mucosa and/or submucosa. The severity of the lesions varied from minimal to slight at 0.4 mg/l (equivalent to 100 ppm) to moderate at 1.7 mg/l (equivalent to 400 ppm). At 0.1 mg/l (equivalent to 25 ppm) no pathological effects on the olfactory epithelium were reported, representing the NOAEC for local effects on the respiratory tract. Slight to moderate changes in respiratory epithelium occurred at 1.7 mg/l (equivalent to 400 ppm) and were characterized as hyperplasia of submucosal glands and/or goblet cells in the anterior regions of the nasal cavity. In the respiratory epithelium, there was inflammation of the mucosa and/or submucosa in males and females exposed to 400 ppm.... The NOAEC for systemic effects was considered to be 100 ppm for female rats and 400 ppm for male rats.

 

The cancer studies of the National Institutes of Health (NTP, 1986) revealed toxicological effects regarding the respiratory tract in male and female rats and mice. Groups of 50 male F344 rats and 50 B6C3Fl mice of each sex were exposed 6 hours per day, 5 days per week to air containing methyl methacrylate at target concentrations of 0, 2.1 or 4.2 mg/l (equivalent to 500 or 1,000 ppm) for 102 weeks. Groups of 50 female rats were exposed at concentrations of 0, 1.0 or 2.1 mg/l (equivalent to 250 or 500 ppm) on the same schedule. Increased incidences of serous and suppurative inflammation of the nasal cavity were observed in male and female rats.

Degeneration of the olfactory sensory epithelium characterized by loss of neuroepithelial cells was also observed in male and female rats. In exposed male and female mice inflammation of the nasal cavity, epithelial hyperplasia in the nasal mucosa and degenerative changes of the olfactory sensory epithelium were reported. In addition methyl methacrylate caused interstitial inflammation of the lung in high dose male mice. The trachea and larynx were also included in the histopathology, but no compound-related effects on these tissues were reported for rats and mice of each dose and sex. A NOAEC could not be established either from rats or mice.” This is true for local effects. For systemic effects, the NOAEC is the highest tested dose, i.e. 1000 ppm for mice and male rats and 500 ppm for female rats.

1,6-HD (specific metabolite of 1,6-HDDMA)

A 28 d gavage study acc. OECD 407 in Wistar rats with 1,6-HD was performed in which animals were tested at doses of 0, 100, 400, 1000 mg 1,6-HD /kg/day. There were no adverse effects observed up to the highest ested dose so that a NOEL of 1000 mg/kg in rat was concluded (OECD 2002)

 

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

The NOAEL for 1,6-HDDMA used for DNEL derivation is 300 mg/kg/bw based on a subacute OECD 422 study with 1,4-BDDMA. For 1,6-HDDMA this is a conservative value for two reasons: First of all, the observed effects in the high dose group were only slight indicating only little likelihood that effects of greater severity at the same effect doses or effects at lower doses would occur in studies of longer duration (e.g. 90 day study). In addition, 1,4-BDDMA is considered as the category substance with an alcohol metabolite (1,4-Butanediol) owing a clear toxicological profile (neurobehaviour). Such clear toxicological properties are not known for 1,6-HD as the alcohol metabolite of 1,6-HDDMA. Any NOAEL derived for 1,6-HDDMA from this study is likely to be conservative.

 

Compliance to REACh requirements

The requirements are covered with subchronic/ chronic studies with the methacrylic metabolite MAA (90 d inhalation rat) and its donor MMA (2 yr oral rat, 2 yr inhalation rat) and the alcohol metabolite 1,6-HD (28 d oral, rat). All mentioned studies are reliable (Reliability 1 or 2) and the read across is done with a high level of confidence (see chapter toxicokinetics and category document, respectively).

Justification for classification or non-classification

No classification for systemic target organ toxicity based on the discussed studies from analogous substances and metabolites.