Ethyl acrylate

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

20 Dec 1977 - 21 June 1978

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study, conducted in compliance with GLP regulations

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1979

Report date:

1979

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

no

Principles of method if other than guideline:

115 male and 115 female rats per group were exposed to ethyl acrylate vapour (purity > 99.5 %) for 27 months (25, 75 ppm) (corresponding to 0.10, 0.31 mg/L) or 6 months (225 ppm) (corresponding to 0.92 mg/L). The rats exposed to 225 ppm for 6 months were held for 21 additional months post-exposure. All groups of animals were observed on each exposure day for signs of toxicity. Blood was collected for haematology and blood chemistry measurement.
The presented interim report consisted of data from preselected groups of 10 rats/sex/dose sacrificed and subjected to necropsy including gross and histopathological examination after 3 or after 6 months of exposure to 0, 25, 75 or 225 ppm ethyl acrylate vapours. Animal observations, palpable mass examinations, physical examinations, and mean body weight changes also included animals to be sacrificed at later dates.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Ethyl acrylate

EC Number:

205-438-8

EC Name:

Ethyl acrylate

Cas Number:

140-88-5

Molecular formula:

C5H8O2

IUPAC Name:

ethyl acrylate

Details on test material:

- Name of test material (as cited in study report): Ethyl acrylate
- Analytical purity: > 99.5 % (GC)
- Impurities: Ethyl propionate ca. 0.15 %; Inhibitor MEHQ 10-15 ppm
- Lot/batch No.: Lot EJS 11/9/77
- Supplier: Ethyl acrylate was supplied by Rohm and Haas Company as a mixture prepared from commercial material supplied by three sponsoring companies. The mixture was prepared using the following proportions: 60 % Rohm and Haas, 25 % Celanese, and 15 % Union Carbide.

Test animals

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, MA)
- Age at study initiation: 4-6 weeks
- Housing: rats were housed with up to 4 per cage
- Diet: Purina Laboratory Chow, ad libitum
- Water: ad libitum
- Acclimation period: 3 weeks

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Remarks on MMAD:

MMAD / GSD: no data

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE:
Exposure concentrations of ethyl acrylate were generated by pumping liquid ethyl acrylate at calculated rates into glass vaporization flasks heated
to approximately 110°C. Vapors from the flasks were swept into the chamber inlet ducts with compressed air where there was further mixing and dilution with incoming air. Total chamber airflow was maintained at approximately 2500 liters per minute (10 air changes per hour).


CHAMBER DESCRIPTION
- Exposure apparatus: Epoxy-resin coated chambers
- Temperature, humidity in air chamber: 22.2°C and relative humidity approximately 50 %
- Air flow rate: Chambers were operated under dynamic airflow conditions and were maintained at a slight negative pressure relative to air in the surrounding area.


TEST ATMOSPHERE
- Brief description of analytical method used: The concentration of ethyl acrylate within each chamber was determined by interpolation from calibration curves derived from standards (100 liter Saran bags) of known concentration. Standardization was checked each exposure day with at least one standard of known concentration.
- Samples taken from breathing zone: yes. Air samples from each chamber were analyzed approximately 1-2 times per hour by infrared spectroscopy using a Miran I Infrared Analyzer at a wavelength of 8.3 u.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The mean daily time-weighted average (TWA) analytical concentration was within ±2 % of the intended target concentration for each exposure group .

Duration of treatment / exposure:

3 or 6 months

Frequency of treatment:

6 hours/day; 5 days/week

Doses / concentrations

Remarks:

Doses / Concentrations:
25; 75; 225 ppm (corresponding to 0.10; 0.31; 0.92 mg/L)
Basis:
nominal conc.

No. of animals per sex per dose:

8/sex/control group (2 control groups); 10 animals/sex/exposure group

Control animals:

yes, sham-exposed

Positive control:

no

Examinations

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: each exposure day

- Monthly physical examinations were conducted on a subgroup of 10 rats/sex/group. The physical examinations included handling as well as observation of appearance and demeanor and visual examination of excreta.
- Palpable mass examinations were conducted prior to initiating exposure and monthly thereafter on all animals.


BODY WEIGHT: Yes
- Time schedule for examinations: Body weights were recorded weekly for the first 3 months, biweekly during the 4-6 months interval.


OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: prior to exposure and after 3 months of exposure
- Dose groups that were examined: Preselected subgroups of 16 rats/sex/control group and 20 rats/sex/exposure group


HAEMATOLOGY: Yes
- Time schedule for collection of blood: at the various interim evaluations (3, 6 months)
- Parameters examined: Total erythrocyte counts, packed cell volumes, hemoglobin concentration, total and differential leucocyte counts


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the various interim evaluations (3, 6 months)
- Parameters examined: alkaline phosphatase activity, serum glutamic-pyruvic transaminase activity, blood urea nitrogen and glucose, cholesterol, fasting blood sugar, triglycerides, total protein, albumin and globulins

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
Liver, kidneys, brain, heart, spleen and  testes were weighed. The following tissues and any gross lesions were collected at necropsy: Liver, heart, pancreas, spleen, brain, pituitary, vertebrae with spinal cord, peripheral nerve, adrenals, kidneys, stomach, small intestine, cecum, large intestine, rectum, mediastinal lymph node, mesenteric lymph node, testes, epididymides, seminal vesicle, coagulatinggland, prostate, urinary bladder, ovaries, oviducts, uterus, cervix, lungs, skeletal muscle, salivary gland, thymus, mediastinal tissue, aorta, esophagus, thyroid, parathyroid, trachea, skin, eyes, tongue, nasal turbinates, head, lacrimal glands, larynx, zymbal glands,  mesenteric tissue. Histologic examinations were conducted on all tissues collected from subgroups of animals in each control group in the high exposure group. Target organs or tissues identified in the high-exposure group were also examined histopathologically in the middle and low exposure groups.

Other examinations:

no

Statistics:

Haematology, clinical chemistry, organ weights, final body weights, and organ to body weight ratios were evaluated by analysis of variance and Dunnett's test. Variances of group body weights and body weight changes were analyzed by Bartlett's test for homogeneity of variance. Body weight changes were evaluated by analysis off variance, and differences between means of treatment and control groups were examined by Duncan's multiple range test.

Results and discussion

Results of examinations

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):

not examined

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
There were no spontaneous deaths during the first 6 months of exposure.
All groups of rats appeared to be in good health throughout the study period. Rats in the high dose group (225 ppm) were quite aggressive when the EA vapour concentrations were falling or increasing. Circling activity, fighting and occasional twitching were observed. The animals were far less active, when the concentrations stabilized, and they appeared lethargic at the end of the exposure periods. Animals in the lower dose groups showed identical behaviour as control animals.


BODY WEIGHT AND WEIGHT GAIN
There was a dose-related retardation of mean body weight gains for male and female rats exposed to 25, 75 or 225 ppm EA vapours. The retardation of growth was judged moderate-to-severe for animals in the 225 ppm group, slight-to-moderate for animals in the 75 ppm group, and slight-to-negligible for animals in the 25 ppm group after 6 months of exposure.



OPHTHALMOSCOPIC EXAMINATION
Examinations after 3 months exposure to EA vapours revealed no treatment-related changes in either the external or internal appearance of the eyes.


HAEMATOLOGY
There were no effects at any exposure level on haematologic parameters.


CLINICAL CHEMISTRY
Alkaline phosphatase values were significantly higher in male rats in the 225 ppm group after 3 months and in female rats in the 225 ppm group after 6 months of exposure; these were considered probable effects of exposure to EA, possibly related to the elevated relative kidney weights of these animals. However, no effects on kidneys were observed in gross or histopathological examinations.


URINALYSIS
There were no effects at any exposure level on urine parameters which were considered to be related to exposure with the possible exception of a slight effect on specific gravity of urine from female rats in the 225 ppm group after 3 and 6 months of exposure.


ORGAN WEIGHTS
Relative kidney weights were higher than controls for male rats in the 225 ppm group after 3 months of exposure, and for both male and female rats in the 225 ppm group after 6 months of exposure. These increased relative kidney weights were considered to be probable effects of exposure to the test material.


GROSS PATHOLOGY
Decreased amounts of adipose tissue in animals in the 225 ppm group was the only treatment-related effect observed at gross necropsy after 3 and 6 months. This observation coincides with pronounced retardation of growth of animals in this group.


HISTOPATHOLOGY: NON-NEOPLASTIC
Histopathological examination of tissues from rats exposed to EA for 3 months revealed lesions of the nasal mucosa in animals of the high and middle dose groups. Lesions of the nasal mucosa were not observed in animals of the low dose group after 3 months exposure. After 6 months exposure, there was a dose-related evidence of irritation of the nasal turbinates at all exposure levels, resulting in areas of focal squamous metaplasia in animals in the 225 and 75 ppm exposure groups.

Effect levels

1

Dose descriptor:

NOAEC

Effect level:

0.1 mg/L air (nominal)

Sex:

male/female

Basis for effect level:

other: Local and systemic effects

2

Dose descriptor:

LOAEC

Effect level:

0.31 mg/L air (nominal)

Sex:

male/female

Basis for effect level:

other: systemic effects: body weight; local effects: lesions of the nasal mucosa

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

The 225 ppm exposure was terminated after six months because the pronounced effects on growth indicated that this level was in excess of the maximum tolerated dose. The animals of the high-dose group were retained for continuing post-exposure observations.

The presented data indicate that histopathological changes of the nasal mucosa may be the most sensitive index for long-term exposure to EA vapours. These lesions of the nasal mucosa were not observed in animals of the low dose group after 3 months exposure. The retardation of body weight gains was considered slight-to-negligible by the authours in this dose group. Thus, the NOAEC for a 90 -days vapour exposure to Ethyl acrylate was set at 25 ppm (corresponding to 0.1 mg/L).