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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well documented, acceptable study report

Data source

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
1980
Report Date:
1980
Reference Type:
publication
Title:
Subchronic and Reproductive Toxicology Studies on Acrylic Acid in the Drinking Water of the Rat.
Author:
DePass LR et al.
Year:
1983
Bibliographic source:
Drug and Chemical Toxicology 6(1): 1-20
Reference Type:
publication
Title:
Subchronic and Reproductive Toxicology Studies on Acrylic Acid.
Author:
DePass LR et al.
Year:
1981
Bibliographic source:
The Toxicologist 1: 103, Abstr. 375
Reference Type:
other company data
Title:
Unnamed
Year:
1981
Report Date:
1981

Materials and methods

Principles of method if other than guideline:
Groups of 15 Fischer 344 rats/sex/dose were administered acrylic acid in the drinking-water at doses of 83, 250, and 750 mg/kg bw/day over a study period of 3 months.
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Acrylic acid
- Analytical purity: 97.75 %
- Impurities (identity and concentrations):
- Dimer, Wt % 0.15
- Acetic Acid, Wt % 0.18
- Propionic Acid, Wt % 0.20
- Acrolein, ppm < 25
- Ethyl Acrylate, ppm < 25
- Iron, ppm < 1
- Phenothiazine, ppm 0.4
- Proto-anemonin, ppm < 20
- Furfural, ppm < 20
- Source: Celanese Chemical Company, Houston, Texas
- Analytical Results Reference: No.: MRS-159-78
- Analysis: The sample was analyzed for concentration of acrylic acid, total acid and dimer using a titration method at regular intervals during the study. The concentrations of acrylic acid (by weight) were found to be 97.75 % and 96.55 % at the start and end, respectively, of the study. An increase
in dimer concentration from 1.1 % at the start to 2.3 % at the end of the 90-day-study was observed.

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Microbiological Associates, Inc., Walkersville, MD
- Age at study initiation: 41 days
- Weight at study initiation: males: 105-142 g; females: 81-110 g
- Housing: 3 males or 5 females/cage
- Diet (ad libitum): Zeigler Brothers NIH-07 Rat and Mouse Ration
- Water (ad libitum): tap water originating from the Beaver Run Reservoir, Westmoreland County, PA


Administration / exposure

Route of administration:
oral: drinking water
Vehicle:
water
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS:
Fresh test solutions were prepared each week, with the percentage of acrylic acid in the water adjusted to maintain a relatively constant dosage level in g/kg bw.

Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The stability of aqueous solutions of acrylic acid was determined using a gas chromatographic procedure. Samples were stored for up to 3 weeks at room temperature with aliquots tested for acrylic acid content at frequent intervals. Stability of acrylic acid was determined for solutions stored in standard glass bottles as well as dosing solutions stored in water bottles under actual study conditions. In addition, the concentration of acrylic acid in the dosing preparations was determined monthly during the study.
Aqueous solutions of acrylic acid were found to be stable for at least 3 weeks when stored at room temperature. Solutions stored in animal water bottles were stable for at least 1 week.
Duration of treatment / exposure:
90 days
Frequency of treatment:
continuously
Doses / concentrations
Remarks:
Doses / Concentrations:
83, 250, and 750 mg/kg bw/d
Basis:
nominal in water
No. of animals per sex per dose:
15
Control animals:
yes, concurrent no treatment
Details on study design:
Post-exposure period: none
Positive control:
none

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily


BODY WEIGHT: Yes
- Time schedule for examinations: weekly


FOOD CONSUMPTION:
- Food consumption for cage determined: Yes, weekly



WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations: weekly


OPHTHALMOSCOPIC EXAMINATION: No


HAEMATOLOGY: Yes
- Time schedule for collection of blood: approx. 2 weeks before sacrifice
- Anaesthetic used for blood collection: No
- Animals fasted: Yes
- How many animals: 15
- Parameters examined: red and white blood cell counts (RBC and WBC), measurement of hemoglobin, calculation of hematocrit and differential and reticulocyte counts.


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: approx. 2 weeks before sacrifice
- Animals fasted: Yes
- How many animals: 15
- Parameters examined: measurement of serum concentration of total cholesterol (CHOL), serum urea nitrogen, glucose, alkaline phosphatase (ALP), aspaitate transaminase (AST), alanine transaminase (ALT) and creatine phosphokinase (CPR).


URINALYSIS: Yes
- Time schedule for collection of urine: approx. 2 weeks before sacrifice
- Metabolism cages used for collection of urine: Yes
- Animals fasted: No data
- Parameters examined: specific gravity, pH, protein, glucose, ketone, bilirubin, occult blood, nitrite, color and turbidity.


NEUROBEHAVIOURAL EXAMINATION: No
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
All rats were given a complete gross necropsy examination and organ weights were recorded for the liver, kidneys, heart, spleen, brain and testes.

HISTOPATHOLOGY: Yes
The following tissues were taken and fixed in 10 % neutral buffered formalin:
Pituitary*, Thyroids*, Parathyroids*, Adrenals*, Heart*, Great vessels - Aorta, Thymus*, Spleen*, Cervical lymph node, Uterus, Cervix, Vagina, Vulva, Testes*, Epididymides*, Prostate, Seminal vesicles, Rectum, Kidneys*, Bronchial lymph node, Mesenteric lymph node*, Mediastinal lymph node, Nasal cavity*, Larynx, Trachea*, Lungs*, Ovaries*, Oviduct*, Liver*, Pancreas*, Brain*, Spinal cord, Sciatic nerve, Eyes*, Extraorbital lacrimal gland, Harderian gland, Inner and middle ears, Skin*, Urinary bladder*, Mammary gland*, Tongue*, External ear, Submandibular salivary gland, Adipose tissue, Parotid salivary gland, Sternal bone marrow, Sublingual salivary gland, Gastrocnemius muscle, Esophagus*, Stomach*, Duodenum*, Jejunum, Ileum, Cecum, Colon*, Anterior thigh muscle, Knee joint, Femur, Costochondral junction, Sternum*, Vertebrae, Any lesions*.

The tissues marked with *, as well as any other tissues with gross lesions, were etamined microscopically on all high dose and control animals. Only those tissues with gross lesions were examined microscopically from the intermediate and low level animals.
Statistics:
For every experimental parameter measured, the results of each of the three test levels (high, medium, low) were compared with the control group. To evaluate the statistical significance of possible changes in continuous data, the analysis of variance (ANOVA) validated by Bartlett's test for homogeneity of variance, was used. Individual mean differences were identified by Duncan's multiple range test when indicated by a significant F value for ANOVA. In the case of heterogenous variances, as indicated by Bartlett's test, the Paired group F test, and either the Cochran or the Student t-test were used to identify significant differences. Enumerative data were evaluated statistically by NxR Chi Square test; differences between groups were delineated by Fisher's Exact test. Non-parametric data were compared by a distribution-free multiple comparison method. The fiducial limit of 0.05 was employed as the critical level of difference not attributable to chance.

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):
effects observed, treatment-related
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
effects observed, treatment-related
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY
There were no deaths in the three-month study period. No clinical signs were observed in any of the animals.


BODY WEIGHT AND WEIGHT GAIN
Body weight gain was depressed markedly for both sexes at the high dosage level. This effect was statistically highly significant in these groups throughout the study. Further examination shows statistical reduction of body weight gain for the intermediate level males at 4 of the 10 comparison intervals and for the females from 41 through 90 doses.


FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
Significant reductions in diet consumption were observed for both sexes at the high dosage level.


WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study)
There was a dose-related reduction in water consumption for all male test animals and for females at the high and intermediate levels as well. Water consumption for the low level males, while statistically significant, was numerically close to that of the controls. Furthermore, in a previous study by the same laboratory (Report 42-558), water consumption in male rats receiving as much as 420 mg/kg bw/day of acrylic acid in the drinking water was
numerically and statistically equivalent to the controls. Therefore, the change in water consumption observed for the low level male rats is not considered to be toxicologically important.


HAEMATOLOGY
The only significant finding was an elevation of the red blood cell count for the low level females. This change was not dose-related and is not considered biologically important; it is probably an artifact.


CLINICAL CHEMISTRY
An increase in serum urea nitrogen was noted for the high level male rats. In the females, a decrease of serum cholesterol and increases of serum urea nitrogen, glucose, alkaline phosphatase and aspartate transaminase were observed among the high dosage level animals. In addition, dosage-related increases of serum urea nitrogen and alkaline phosphatase and a decrease in serum cholesterol were observed at the intermediate dosage level for the females.


URINE ANALYSIS
In both sexes at the high and intermediate levels, increases of urine specific gravity and urine protein were observed. A decrease in urine pH was noted for the high level female rats as well. Alterations in fluid balance resulting from decreased fluid intake may underlie the changes in serum urea nitrogen, urine specific gravity and urine protein. An alternate explanation of direct or indirect renal toxicity supported by increased relative kidney weights in both sexes at the high and intermediate levels is possible.


ORGAN WEIGHTS
The effect of acrylic acid on the organ weights of the rats was obvious in the high dosage level in both sexes.

In the male rats this effect included:
(1) Significant reduction in absolute liver, spleen, heart and brain weights.
(2) Significant increase in relative (as % of body weight) liver, kidney, spleen, brain and testes weights.

In the female rats, the effects on the organ weights at the high dose level included:
(1) Significant reduction in absolute liver, spleen and heart weights.
(2) Significant increase in absolute kidney weight and relative kidney and brain weights.

Furthermore, the significant increases in relative kidney and testes weights for the intermediate level males and absolute and relative kidney weights for the intermediate level females are dose-related deleterious effects.


GROSS PATHOLOGY
No significant treatment related gross lesions were noted in any animal on the study.


HISTOPATHOLOGY: NON-NEOPLASTIC
No significant difference in prevalence of microscopic lesions was noted between animals treated with acrylic acid and controls. Malacia within the optic nerves was observed in 2/15 high dose males versus 0/15 control males (P = 0.48) and 1/15 high dose females versus 0/15 control females (P = 1.00). The true prevalence of this lesion in the study could not be determined. However, the unilaterality of this lesion concomitant with absence of lesions within the spinal cord and sciatic nerve indicate that this lesion is not attributable to the treatment with acrylic acid.


Effect levels

open allclose all
Dose descriptor:
NOAEL
Effect level:
83 mg/kg bw/day (nominal)
Sex:
male/female
Dose descriptor:
LOAEL
Effect level:
250 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
other: Diet and water consumption, body and organ weight changes and abnormal clinical chemical and urine analysis parameters

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

Deleterious effects were observed at the high dosage level (750 mg/kg bw/day) and at the intermediate level (250 mg/kg bw/day) in both sexes. These effects included diet and water consumption, body and organ weight changes and abnormal clinical chemical and urinalysis parameters. At the low dosage level (83 mg/kg bw/day), a significant reduction in water consumption was noted for the male rats. Since this effect is only a moderate reduction of water intake and since the variance is relatively small, the toxicological significance is considered minimal. The slight increase in red blood cells noted for the low dosage level females is considered to be an artifact. Accordingly, the maximum no ill-effect level for three-month ingestion of acrylic acid in the rat is estimated to be at or slightly lower than 83 mg/kg bw/day. Based on this consideration and the findings concerning the effect of acrylic acid at the intermediate and high levels, the minimum effect level is estimated to be 250 mg/kg bw/day.

Summary of results of 90 days of inclusion of Acrylic acid in the drinking water of male rats:

 

Dosage goal [mg/kg bw/d]

750

250

83

control

 

Mean

SD

Mean

SD

Mean

SD

Mean

SD

Dosage attained [mg/kg bw/d]

740

50

250

10

84

4

0

0

 

 

 

 

 

 

 

 

 

Diet consumption [g/kg bw/d]

14.0***

0.6

16.2

0.6

16.4

0.9

16.9

0.6

Water consumption [mL/rat/d]

13.0***

0.7

17.5***

0.8

19.4**

1.3

21.4

0.7

Body weight gain [g]

141.5***

21.5

188.2

23.5

196.7

17.3

200.6

20.2

 

 

 

 

 

 

 

 

 

Liver weight [g]

9.33***

1.25

11.30

1.64

11.17

0.85

11.08

0.89

Liver wt as % bw

3.52*

0.15

3.61

0.38

3.50

0.15

3.40

0.14

 

 

 

 

 

 

 

 

 

Kidney weight [g]

2.06

0.22

2.20

0.18

2.14

0.16

2.15

0.13

Kidney wt as % bw

0.78***

0.04

0.71***

0.03

0.67

0.03

0.66

0.02

 

 

 

 

 

 

 

 

 

Spleen weight [g]

0.53**

0.05

0.60

0.08

0.61

0.06

0.60

0.06

Spleen wt as % bw

0.20**

0.02

0.19

0.02

0.19

0.02

0.18

0.01

 

 

 

 

 

 

 

 

 

Heart weight [g]

0.71**

0.09

0.81

0.10

0.83

0.08

0.82

0.10

Heart wt as % bw

0.27

0.02

0.26

0.02

0.26

0.02

0.25

0.03

 

 

 

 

 

 

 

 

 

Brain weight [g]

1.74**

0.08

1.81

0.08

1.81

0.08

1.84

0.06

Brain wt as % bw

0.66***

0.05

0.58

0.04

0.57

0.03

0.57

0.03

 

 

 

 

 

 

 

 

 

Testes weight [g]

2.72

0.17

2.82

0.14

2.73

0.14

2.72

0.32

Testes wt as % bw

1.04***

0.06

0.91*

0.07

0.86

0.07

0.84

0.11

 

 

 

 

 

 

 

 

 

* p< 0.05, ** p< 0.01, *** p< 0.001

Summary of results of 90 days of inclusion of Acrylic acid in the drinking water of female rats:

 

Dosage goal [mg/kg bw/d]

750

250

83

control

 

Mean

SD

Mean

SD

Mean

SD

Mean

SD

Dosage attained [mg/kg bw/d]

720

50

250

10

84

3

0

0

 

 

 

 

 

 

 

 

 

Diet consumption [g/kg bw/d]

8.7**

0.3

10.2

0.6

10.6

0.2

10.4

0.4

Water consumption [mL/rat/d]

8.6***

0.5

11.8***

0.7

14.9

0.8

15.0

0.7

Body weight gain [g]

48.0***

8.2

68.4*

9.8

82.1

11.1

78.0

10.8

 

 

 

 

 

 

 

 

 

Liver weight [g]

4.91***

0.50

5.61

0.47

5.84

0.57

5.70

0.45

Liver wt as % bw

3.27

0.22

3.29

0.18

3.16

0.14

3.19

0.13

 

 

 

 

 

 

 

 

 

Kidney weight [g]

1.34**

0.10

1.37***

0.07

1.29

0.08

1.24

0.08

Kidney wt as % bw

0.89***

0.04

0.80***

0.06

0.70

0.04

0.69

0.03

 

 

 

 

 

 

 

 

 

Spleen weight [g]

0.37***

0.04

0.43

0.04

0.46

0.05

0.43

0.05

Spleen wt as % bw

0.24

0.02

0.25

0.02

0.25

0.02

0.24

0.02

 

 

 

 

 

 

 

 

 

Heart weight [g]

0.45***

0.04

0.54

0.05

0.55

0.06

0.54

0.07

Heart wt as % bw

0.30

0.02

0.32

0.02

0.30

0.02

0.30

0.03

 

 

 

 

 

 

 

 

 

Brain weight [g]

1.61

0.12

1.68

0.08

1.66

0.10

1.65

0.14

Brain wt as % bw

1.07***

0.09

0.99

0.08

0.90

0.08

0.93

0.10

 

 

 

 

 

 

 

 

 

* p< 0.05, ** p< 0.01, *** p< 0.001

 

 

Applicant's summary and conclusion