Hexyl acrylate

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Data source

Reference

Reference Type:

publication

Title:

Relative Developmental Toxicities of Acrylates in Rats following Inhalation Exposure.

Author:

Saillenfait AM et al.

Year:

1999

Bibliographic source:

Toxicol. Sciences 48: 240-254

Materials and methods

Principles of method if other than guideline:

Groups of 20-29 bred female rats (17-25 pregnant) were exposed to the compound 6h/day on days 6 through 20 of gestation. Control animals were exposed concurrently to filtered room air. The test concentrations of n-butyl acrylate were 100, 200, and 300 ppm (corresponding to approx. 0.52, 1.05, and 1.57 mg/L)*.
* Calculation of concentrations (mg/L) based on Derelanko MJ (2000). Toxicologist's Pocket Handbook, CRC Press, conversion table, p. 57

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Butyl acrylate

EC Number:

205-480-7

EC Name:

Butyl acrylate

Cas Number:

141-32-2

Molecular formula:

C7H12O2

IUPAC Name:

butyl acrylate

Details on test material:

- Test substance: n-butyl acrylate
- Analytical Purity: > 99 %
- Supplier: Aldrich Chemical Co. (Milwaukee, WI)

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: IFFA CREDO Breeding Laboratories (Saint-Germain-sur-l' Arbresle, France)
- Age at study initiation: Young, nulliparous females
- Weight at study initiation: 200-220 g
- Housing: Single in clear polycarbonate cages with stainless-steel wire lids and hardwood shaving as bedding.
- Diet: Food pellets (UAR Alimentation Villemoisson, France), ad libitum
- Water: Filtered tap water, ad libitum


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 ± 2
- Humidity (%): 50 ± 5
- Photoperiod (hrs dark / hrs light): 12 hrs dark/12 hrs light

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure (if applicable):

whole body

Vehicle:

unchanged (no vehicle)

Details on exposure:

EXPOSURE
Exposures were conducted in 200-L glass/stainless-steel inhalation chambers with dynamic and adjustable laminar air flow (6-20 m3/h). The chamber temperature was set at 23 ± 2°C, and the relative humidity at 50 ± 5 %. The air-flow rate passed through the fritted disk of a heated bubbler containing the test chemical. Concentrations of acrylate ester were monitored continuously with a gas-chromatograph equipped with a flame ionization detector and an automatic gas-sampling valve. In addition, exposure levels were determined once during each 6-h exposure period by collecting atmosphere samples through glass tubes packed with activated charcoal. The charcoal samples were then desorbed with carbon disulfide. The resulting samples were analyzed by gas chromatography using appropriate internal standards.


GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Glass/stainless-steel inhalation chambers
- Source and rate of air: Test atmospheres were generated through an additional air-flow  rate passed through the fritted disk of a heated bubbler containing ethylhexyl acrylate. The vaporized compound was introduced into the main air inlet pipe of the exposure chamber.
- Air flow rate: 6-20 m3/h


TEST ATMOSPHERE
- Brief description of analytical method used: GC/FID
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analytical concentrations (mean ± SD):
103.3 ± 6.7 ppm (nominal: 100 ppm)
202.8 ± 9.7 ppm (nominal: 200 ppm)
302.5 ± 10.1 ppm (nominal: 300 ppm)

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1/2-3
- Length of cohabitation: Overnight
- Proof of pregnancy: sperm in vaginal smear referred to as day 0 of pregnancy

Duration of treatment / exposure:

days 6 to 20 of gestation

Frequency of treatment:

6 hours/day

Duration of test:

until gestation day 21

No. of animals per sex per dose:

20

Control animals:

yes, sham-exposed

Details on study design:

- Dose selection rationale:
Exposure concentrations were based on preliminary studies in which marked decreases in maternal weight gain were observed at 200 and 300 ppm of butyl acrylate. Results from previous prenatal inhalation toxicity studies on butyl acrylate were also considered (Merkle and Klimisch, 1983). The high concentrations of butyl acrylate for the definitive study (200 and 300 ppm, respectively) were chosen to maximize the opportunity of identifying embryolethal or teratogenic potential.

Examinations

Maternal examinations:

BODY WEIGHT: Yes
- Time schedule for examinations: On gestation day (GD) 0, 6, 13 and 21.


FOOD CONSUMPTION: YES
Food consumption was measured for the intervals GD 6-13 and 13-21.


POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 21
- Organs examined: The uteri were removed and weighed. The number of implantation sites, resorptions, and dead and live fetuses were recorded.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
The number of implantation sites, resorptions, and dead and live fetuses were recorded. Uteri which had no visible implantation sites were stained with ammonium sulfide (10 %) to detect very early resorptions.

Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: No data
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes

Fetal examinations:

Live fetuses were weighed, sexed, and examined for external anomalies including those of the oral cavity. Half of the live fetuses from each litter were preserved in Bouin's solution and examined for internal soft tissue changes. The other half were fixed in ethanol (70 %), eviscerated, and then processed for skeletal staining with alizarin red S for subsequent skeletal examination.

- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: Yes: all per litter

Statistics:

Data were presented as mean ± SD. The number of  implantation sites and live fetuses and the various body weights were analyzed by one-way analysis of variance (ANOVA), followed by Dunnett's test if differences were found. The percentages of non-live  implants and  resorptions and the proportions of fetuses with alterations in each litter were evaluated by using the Kruskal-Wallis test, followed by the Dixon-Massey test where appropriate. Rates of pregnancy, fetal sex ratio, and percentage of litters with malformations or external, visceral, or skeletal variations were analyzed by using Fisher's test. Where applicable, least-squares analysis was carried out. For all statistical tests, the level of significance was set a priori at alpha = 0.05.

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

not specified

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

During the entire exposure period, maternal weight gain was signifciantly reduced at 200 ppm and 300 ppm compared to the control group. Absolute weight gains (expressed as the day 21 body weight minus the gravid uterus weight and minus the day 6 body weight) were reduced in a dose-rependent manner in all exposure groups.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Decreases in food consumption was observed during the first half of the study for the females in the 100 ppm dose group and throught the exposure period at 200 and 300 ppm. The maximum decrease was 40-50% at the highest concentration.

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

not examined

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Maternal developmental toxicity

Number of abortions:

no effects observed

Pre- and post-implantation loss:

no effects observed

Total litter losses by resorption:

no effects observed

Early or late resorptions:

no effects observed

Dead fetuses:

no effects observed

Changes in pregnancy duration:

not examined

Description (incidence and severity):

Migrated Data from removed field(s)
Field "Effects on pregnancy duration" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsMaternalAnimals.MaternalDevelopmentalToxicity.EffectsOnPregnancyDuration): not examined

Changes in number of pregnant:

no effects observed

Effect levels (maternal animals)

Key result

Dose descriptor:

LOAEC

Effect level:

ca. 0.52 mg/L air (nominal)

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Fetal body weight changes:

effects observed, treatment-related

Description (incidence and severity):

Fetal body weight was significantly reduced at 200 ppm (for both sexes combined and males) and at 300 ppm (both sexes combined, males and females). These decreases amounted to 7-8 % (p<0.05) and 26-28 % (p<0.01) of control values for the 200 and 300 ppm groups, respectively.

Reduction in number of live offspring:

no effects observed

Changes in sex ratio:

no effects observed

Changes in litter size and weights:

not specified

Changes in postnatal survival:

no effects observed

External malformations:

no effects observed

Skeletal malformations:

no effects observed

Description (incidence and severity):

A few sporadic malformations were seen in the 300 ppm and the control group. The incidence of individual skeletal variations (mainly incomplete ossification of sternebrae and of vertebral centra) was similar in the control and treated groups.

Visceral malformations:

no effects observed

Effect levels (fetuses)

1

Key result

Dose descriptor:

NOAEC

Effect level:

ca. 0.52 mg/L air (nominal)

Basis for effect level:

other: fetotoxicity

2

Key result

Dose descriptor:

NOAEC

Effect level:

ca. 1.57 mg/L air (nominal)

Basis for effect level:

other: teratogenicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Maternal body weights:

Concentration [ppm/6h/d]	Maternal body weight GD 6 [g]	Absolute weight gain [g]
0	294 ± 23	32 ± 15
100	289 ± 23	18 ± 14*
200	299 ± 24	-16 ± 20**
300	292 ± 23	-60 ± 26**

Absolute weight gain: (Day 21 body weight) - (gravid uterus weight) - (Day 6 body weight)

Reproductive parameters:

Conc. [ppm/6h/d]	No. of litters	No. of implantation sites/litter	% of non-live implants/litter	% of resorption sites/litter	No. of live fetuses/litter	Average fetal body weight/litter [g]
0	25	15.68 ± 3.17	10.9 ± 15.49	10.64±15.62	14.12 ± 4.01	5.74 ± 0.43
100	24	15.58 ± 3.05	6.82 ± 10.19	6.82 ± 10.19	14.71 ± 3.57	5.71 ± 0.35
200	24	15.08 ± 4.23	4.72 ± 5.96	4.72 ± 5.96	14.46 ± 4.20	5.33 ± 0.40*
300	25	15.40 ± 5.24	6.48 ± 15.94	6.48 ± 15.94	14.68 ± 5.38	4.25 ± 0.94**

Concentration [ppm/6h/d]	0	100	200	300
Mean % of fetuses with:
- any malformations/litter	2.00 ± 7.33	0	0	0.62 ± 2.65
- external variations/litter	1.33 ± 6.67	0	0	0.22 ± 1.11
- visceral variations/litter	8.81 ± 14.64	0	0	4.17 ± 20.41
- skeletal variations/litter	13.70 ± 15.48	17.01 ± 14.53	18.71 ± 24.21	24.65 ± 20.69
- any variations/litter	12.60 ± 10.80	13.27 ± 15.07	10.10 ± 10.32	15.90 ± 19.98

* ,** Significant differences from the control (0 ppm) value, p 0.05, and p 0.01, respectively.

Applicant's summary and conclusion

Executive summary:

In a developmental toxicity study, pregnant Sprague-Dawley female rats (20-29 per dose) were exposed to the compound 6h/day on days 6 through 20 of gestation. Control animals were exposed concurrently to filtered room air. The test concentrations of n-butyl acrylate were 100, 200, and 300 ppm (corresponding to approx. 0.52, 1.05, and 1.57 mg/L). Significant decreases in maternal body weight gain were observed at 200 ppm and 300 ppm, and decreased absolute weight gain were observed in all dose groups through the entire exposure period. Decreased fetal body weight was observed at 200 ppm (7-8%) and 300 ppm (26-28%) in the presence of significant maternal toxicity. No significant increases in malformations was observed in n-butyl acrylate exposed fetuses.