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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study with acceptable restrictions

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2001

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other: EPA-Pesticide Assessment Guidelines, Subdivision F, Hazard Evaluation, Human and Domestic Animals, Series 81, 82, and 83, US Department of Commerce, National Technical Information Service PB91-154617, 1991.
Deviations:
not specified
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): 2,4-D DMA
- Analytical purity: 66.2% active ingredient in aqueous based manufacturing concentrate
- Source of test material: Industrial Task Force on 2,4-D Research Data

Test animals

Species:
rabbit
Strain:
New Zealand White
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Hazleton Research Products, Inc., Denver, PA
- Age at study initiation: 5 - 7.5 months
- Housing: individually in cages with wire floors
- Diet: certified Laboratory rabbit chow No. 5322 (Purina Mills, Inc. St. Louis, MO)
- Water: municipal water ad libitum
- Acclimation period: at least two weeks

ENVIRONMENTAL CONDITIONS
The animal rooms of the facility were designed to maintain environmental conditions with respect to temperature, relative humidity, airflow
and lightning conditions, and were regulated for rabbits.

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
other: Not specified if vehicle is corn oil, sterile deionized water or aqueous methylcellulose
Details on exposure:
VEHICLE
- Amount of vehicle (if gavage): 1 - 10 mL/kg body weight
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The concentration of the test substance in the dosing solution was confirmed by validated analytical methods (HPLC of GC)
Details on mating procedure:
- Impregnation procedure: artificial insemination, day of insemination is considered day 0 of gestation
- Any other deviations from standard protocol:
After insemination, rabbits were given an intravenous injection of 20 - 100 international units of human chorionic gonadotropin.
Duration of treatment / exposure:
Gestation days 6 - 18
Frequency of treatment:
once daily
Duration of test:
29 days
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
12, 36.1 and 108.4 mg/kg bw/day
Basis:
nominal conc.
active ingredient
Remarks:
Doses / Concentrations:
10, 30 and 90 mg/kg bw/day
Basis:
other: 2,4-D acid equivalent
No. of animals per sex per dose:
20
Control animals:
yes, concurrent vehicle

Examinations

Maternal examinations:
DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: all animals were observed twice daily for signs of treatment related effects

BODY WEIGHT: Yes
- Time schedule for examinations: Body weights were recorded on GD 0, either daily or every third day during the dosing period, and on days 20, 24, 28 and/or 29 of gestation

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 28 or 29
- post-mortem examinations were also performed on all females who died spontaneously or were sacrificed in a moribund condition.
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes (including their positions)
- Number of resorptions: Yes
Other:
- live and dead fetuses were counted
- Uteri with no visible implantations were stained with a 10% solution of ammonium sulphide, and examined for evidence of early resorptions.
Fetal examinations:
- External examinations: Yes
- Skeletal examinations: Yes
- Each fetus was individually identified, weighed, sexed, and given a gross examination for external malformations/variations to include observation for palatal defects.
- All fetuses were euthanized and examined by dissection for evidence of visceral alterations. This also included a fresh examination of the brain.
All fetuses were then preserved in alcohol, eviscerated, cleared and stained with alizarin red-S and examined for skeletal alterations.
Statistics:
Different statistical tests were used (e.g. Bartlett, Anova, Wilcoxon) to analyse maternal body weight, maternal body weight gain, gravid uterine weight, feed consumption, litter averages for percent male fetuses, fetal body weights, number of fetuses, litter size, number of corpora lutea, number of implantations, fetal ossification sites, and percent fetal alterations.
Historical control data:
Data was compared to historical control data, but these data were not explicitly given.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
Dose-related clinical signs of toxicity were seen at or above a dose of 36.1 mg/kg bw/day (30 mg/kg bw/day acid equivalent). With higher acid equivalent doses (90 mg/kg/day), more severe maternal effects were noted. Clinical signs of toxicity (myotonia, ataxia, and impaired/lost righting reflex) became evident. The lack of effect on maternal body weight gain may be explained with the low increase observed with the control group. The body weight gain throughout the observation time was only half in comparison to the other controls of experiments conducted in parallel.

Effect levels (maternal animals)

open allclose all
Dose descriptor:
NOAEL
Effect level:
36.1 mg/kg bw/day
Based on:
act. ingr.
Basis for effect level:
other: maternal toxicity
Dose descriptor:
NOAEL
Effect level:
108.44 mg/kg bw/day
Based on:
act. ingr.
Basis for effect level:
other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
There were no effects on maternal reproductive parameters observed (litter size, resorption rates, etc.) or on fetal body weights. No evidence of teratogenicity was observed. Low incidences of malformations were seen scattered through the different dose groups, including control. The incidences of the individual malformations observed were consistent with historical control data.

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Any other information on results incl. tables

Table 1: 2,4-D DMA Teratology: maternal, reproductive and fetal parameters in rabbits

 

DMA - Dose (mg/kg/day)

0

12

36.1

108.44

2,4-D equivalent (mg/kg/day)

0

10

30

90

Maternal parameters

 

 

 

 

No. bred

20

20

20

20

No. deaths

0

0

4

0

Sacrificed

0

0

0

0

Aborted

0

1

1

0

Maternal body weight gain (GD 6 – 19) (kg)

0.10

0.10

0.12

0.14

Reproductive parameters

 

 

 

 

No. Litter

20

16

18

14

No. of implantations

177

133

163

112

% implantations resorbed

4.0

5.3

4.9

11.6

% Litters with resorptions

30.0

43.8

33.3

57.1

Fetal body weight (g)

43.6 ± 5.6

42.9 ± 7.1

40.9 ± 5.9

44.5 ± 7.0

Fetal parameters

 

 

 

 

Fetuses examined*

170 (20)

126 (16)

155 (18)

99 (14)

Visceral alterations

 

 

 

 

- Lung lobe, agenesis*

3 (3)

2 (1)

1 (1)

0

Skeletal alterations

 

 

 

 

- Ribs. 7th cervical

0

0

0

0

Total external malformations

0

0

1 (1)

1 (1)

Total visceral malformations

3 (3)

2 (1)

1 (1)

1 (1)

Total skeletal malformations

2 (2)

2 (1)

2 (2)

5 (5)

Study was performed at Argus Laboratories

* - No. of fetuses (No. of litters)

** - considered a malformation

Maternal toxicity was noted at or above a dose level of 36.1 mg/kg bw/day (30 mg/kg bw/day acid equivalent). At these dose levels, embryonal and fetal development was essentially unaffected, and there was no indication of any teratogenic effect. Therefore the test substance is not considered to be teratogenic under the conditions of this test.

Applicant's summary and conclusion