2-ethylhexyl (4-chloro-2-methylphenoxy)acetate

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

12.09.1991 - 10.10.1991

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Cross-reference

Reason / purpose for cross-reference:

read-across source

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1991

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

(4-chloro-2-methylphenoxy)acetic acid

EC Number:

202-360-6

EC Name:

(4-chloro-2-methylphenoxy)acetic acid

Cas Number:

94-74-6

Molecular formula:

C9H9ClO3

IUPAC Name:

(4-chloro-2-methylphenoxy)acetic acid

Test material form:

liquid

Details on test material:

pH = 10.9

Test animals

Species:

rat

Strain:

Wistar

Details on test animals or test system and environmental conditions:

Animals:
Healthy young adult virgin femeles strain Wistar were used. The females aged 3 months. At the start of the study there average weight was 218 t 19g. They came from the Central Experimental Animals Farm, Silesian Medical Academy in Katowice. The males were from the same farm in the same condition. 20 pregnant females per each group were used.

Housing
The animals were caged in plast-metalic cages with UV-sterilized wood spruces in one experimental room. On each cage was a shield with cod of the experiment, cage number, number of animal, start and finish date of study, dose and eventually date of death.
Feeding
Conventional laboratory food for rodents "Murigran" and drinking water were supplied unlimited. Toxic impurities (heavy metals, aflatoxin, nitrosamines) in food were determined. All values were under the FDA - limits.

Administration / exposure

Route of administration:

oral: gavage

Details on exposure:

Dose levels
Doses were chosen on the basis of the sub-chronic, chronic and embriotoxic/teratogenic values. In a pilot study in the doses 250 mg/kg b. w. 8 from 9 tested females died in the days 11 – 15 of the experiment, Three followed doses of MCPA were determined: 0.5, 5 and 50 mg/kg b. w. A control group received only water. The volume of the applied solution was constant , a 1 ml per 100 g of b.w.

Results and discussion

Results: maternal animals

Effect levels (maternal animals)

Key result

Dose descriptor:

NOAEL

Effect level:

50 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

body weight and weight gain

food consumption and compound intake

Results (fetuses)

Effect levels (fetuses)

Key result

Dose descriptor:

NOAEL

Effect level:

50 mg/kg bw/day

Based on:

test mat.

Sex:

female

Basis for effect level:

fetal/pup body weight changes

changes in litter size and weights

external malformations

skeletal malformations

Overall developmental toxicity

Key result

Developmental effects observed:

no

Any other information on results incl. tables

Results

At a pilot doses 250 mg/kg a bight death rate of the females (8/9) was noted. By this reason this doses cannot be evaluated. In the remaining doses during the whole experiment time the females were in good form without any toxic signs in the control as well as in the treated groups. Only in the dose 50 mg/kg b.w. temporarily there was observed a lower motility and distinctly reaction on external impulses. No statistically significant differences were noted between the controls and the intoxicated groups in food consumption (Tab. 1) and body weight (Tab.2)

Table No 1 Food intake (gram/rat/day)

Day of pregnancy	Dose (mg/kg b. w.)
	Control	0.5	5.0	50.0
5	21.2 ± 3.5	20.8±3.6	21.9±32	21.7±19
10	20.9 ± 1.8	22.4±2.0	21.3±2.4	20.0±18
15	22.5 ± 2.0	22.7±2.8	22.5±2.0	21.0±27
20	24.5 ± 1.8	25.1± 2.9	24.1±3.1	22.7±28

 

 

Table No 2 MCPA - Body weight of females (g)

Day of	Dose (mg/Kg b.w.)
pregnancy	Control	0.5	5.0	50.0
1	214±21	221±19	214±20	223±17
6	237±23	244±20	237±20	246±19
7	238±23	246±20	238±20	247±17
8	243±24	250±21	242±20	252±19
9	246±23	253±20	245±20	254±18
10	247±23	253±19	246±21	254±19
11	254±24	259±18	256±20	260±18
12	255±25	261±19	255±21	262±18
13	263±25	267±19	261±21	266±18
14	264±25	270±18	266±22	270±19
15	276±30	274±19	270±23	276±20
20	328±27	331±24	326±28	329±24

 

The number of fetuses obtained from 20 females in the control and each intoxicated group were similar. Also the average number of fetuses in one litter in all groups was similar. All fetuses were alive. No anomaly were stated. The number of resorpations per one female differ from 0 to 2 in all groups but the average number was 0.25 – 0.45 in the in toxicated groups and 0.05 in the control.

But the values are in the range of the physiological norm for this strain. The average number of corpus luteum was similar in each group, The data are listed in table 3.

 

Table no 3 Number of corpus luteum, fetuses and resorptions

Dose mg/Kg bw	Number of females	Number of corpus luteum average	Number of fetuses				Number of resorptions
			Sum	in one litter min. - max.	Average in one litter	Anomaly	Sum	in one female min. - max.	Average in one female
Control	20	10.9±1.6	218	8 - 13	10.9  ±  1. 5	0	1	0 - 1	0.05
0.5	20	11.3 ± 2.7	222	5 - 16	11.1 ± 2.8	0	5	0 - 1	0.25
5.0	20	11.3 ± 1. 5	217	7 - 14	10. 8 ± 1. 9	0	9	0 - 2	0.45
50.0	20	11.3± 2.3	221	6 - 14	11. 0  ±  2. 5	0	7	0 - 2	0.35

 

The weight of fetuses with the placenta and amnostic fluids and without placenta were similar in the control and in the doses 0.5 and 50 mg/kg. But in the dose 5 mg/kg b.w. this parameters was significantly higher. But this results are not dose - respondent. The length of the fetuses with the tails and without the tails in the intoxicated groups differ not from the control, This data are given in table 4.

Table no 4 Weight of fetuses and placenta and length of fetuses

Dosis mg/Kg        b.w.	Number of fetuses	weight of fetuses (mg)		Length of fetuses (mm)
		with placenta	without placenta	with tail	without tail
Control	218	4610 ± 176	3272 ± 238	50.0 ± 0.8	37.6 ± 0.7
0.5	222	4771 ± 337	3344 ± 224	50.7 ± 0.9	38.1  ±  1.0
5.0	217	4868 ± 235	3484 ± 228	51.3 ± 1.3	38.3 ± 0.9
50.0	221	4684 ± 240	3408 ± 250	51.0 ± 1.4	38.0 ± 0.9

 

The macroscopic findings in the fetuses were not significant, The body integuments, the legs, the conchaes of auricle, nares, eyelids and oral cavities were well developed.

After sagittal section the exanimated soft tissues of the fetuses were well developed and normally located in the body cavities. There were no differences between the control and the exposed groups. The percentage of ossification points of the sternum in the intoxicated groups, regardless of the dose, did not differ significantly from the control (Tab, 5 and 7),

Table no. 5 number of ossification points of sternum (X)

Dosis mg/kg              b.w.	Number of fetuses		Humber of ossification points
		4		5	6	7
Control	112	100.	0	97.3	79.5	3.6
0.5	115	100.	0	99.1	87.8	0.0
5.0	113	100.	0	99.1	90.3	0.9
50.0	114	100.	0	100.0	86.0	1.7

 

Table no 6 Number of ossification points of legs (X)

Dosis   mg/Kg b.w.	limber of fetuses	Humber of ossification points
		Fore leg		Hind leg
		3	4	3	4	5
Control	112	100	45.5	100	100.0	0.0
0.5	115	100	70.4	100	97.4	0.9
5.0	113	100	81.4	100	100.0	0.9
50.0	114	100	87.7	100	100.0	0.0

 

The same is true for the ossification of the metacarpus and metacarpus (Tab 6 and 7).

Table no 7 Average number of ossification sternum and legs

Dosis   mg/kg b.w.	Number of fetuses	Sternum	Metacarpus	Metatarsus
Control	112	5.9 ± 0.3	3.5 ± 0. 3	4.0 ± 0.0
0.5	115	5.9 ± 0.2	3.7 ± 0.3	4.0 ± 0.1
5.0	113	5.9 ± 0.2	3.8 ± 0.3	4.0 ± 0.0
50.0	114	5.9 ± 0. 2	3.9 ± 0.2	4.0 ± 0.0

The ossifications of the skull, axial skeleton, ribs, scapular and pelvis region with legs were well developed and did not differ between the treated groups and the control.

Applicant's summary and conclusion

Conclusions:

It was stated that MCPA in doses till 50 mg/Kg b.w, has no embriotoxic and teratogenic effects on the rats fetuses.
MCPA in a dose of 250 mg/kg b.w. was very toxic for the pregnant females

Executive summary:

MCPA in the form of soluble concentrate was applied to young healthy female rats strain Wistar orally by a gevage daily in the 6 - 15 day of pregnancy. Three groups consisting of 20 pregnant females each received MCPA (Chwastox extra) diluted with water in doses 0.5, 5 and 50 mg/Kg b. w. The control received only water. Females in all groups survived the pregnant period without any toxic effect. One day before the expected birth the females were sacrificed and the following parameters were examined: number of implantation sides, resorpations and corpora lutes, number of dead, living and malformed fetuses, their weight, length and external look. One - half of each litter was prepared for examination for skeletal deformations. The remained fetuses were fixed in Bouen solution for soft tissue examination.

It was stated that MCPA in doses till 50 mg/Kg b.w, has no embriotoxic and teratogenic effects on the rats fetuses.