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Repeated dose toxicity: inhalation

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Administrative data

sub-chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
according to guideline
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
GLP compliance:
Limit test:

Test material

Constituent 1
Reference substance name:
Methacrylic acid
EC Number:
EC Name:
Methacrylic acid
Cas Number:
methacrylic acid
Details on test material:
Test substance No.: 06/0581-2
Batch-Identification: 011835eda0
Purity: 99.8 area-%
Homogeneity: Homogeneous
Storage stability: Expiry day: 13 Apr 2008Date of production: 12 Apr 2007
Physical state/Appearance:Liquid / colorless, clear
Storage conditions: Room temperature, no direct sunlight, under light exclusion,
protect against heat, storage between 18-25°C, under atmospheric oxygen

Test animals

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.

Administration / exposure

Route of administration:
Type of inhalation exposure:
whole body
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:
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
Doses / concentrations
Doses / Concentrations: 0, 70 mg/m³ (20 ppm), 141 mg/m³ (40 ppm), 352 mg/m³ (100 ppm ), 1232 mg/m³ (350 ppm )
No. of animals per sex per 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.
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

Results and discussion

Results of examinations

Clinical signs:
no effects observed
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

Effect levels

open allclose all
Key result
Dose descriptor:
Effect level:
ca. 100 ppm
Basis for effect level:
other: = 352 mg/m³ for local effects and effects to body weight
Key result
Dose descriptor:
Effect level:
ca. 350 ppm
Basis for effect level:
other: = 1232 mg/m³ for systemic effects in target organs other than body weight effects due to reduced food consumption
Key result
Dose descriptor:
Effect level:
ca. 350 ppm
Basis for effect level:
other: = 1232 mg/m³ air; reduced food consumption and body weight gain
Key result
Dose descriptor:
Effect level:
ca. 350 ppm
Basis for effect level:
other: = 1232 mg/m³ for local effects (goblet cell hypertrophy/hyperplasia) in the respiratory epithelium in 2/10 females

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

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 according to 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 study condition, the no-observed adverse effect level (NOAEL) in this study was 100 ppm (352 mg/m³) for the male and female rats (Ma-Hock, 2008).

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