Octyl (R)-2-(4-chloro-2-methylphenoxy)propionate

Developmental toxicity / teratogenicity

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: Klimisch reliability of study is 1 (GLP guideline study); but the maximum score for read-across should be rel. 2 according to ECHA Practical Guide 6.

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1993

Report date:

1993

Reference 2

Reference Type:

secondary source

Title:

No information

Author:

The Danish Environmental Protection Agency

Year:

1998

Bibliographic source:

Mecoprop-P, EU Review Programme on active substances in Plant Protection Products, Scientific Evaluation and Assessment, Draft December 1998 (Volume 3, Annex B, ) and Addendum II July 2002; see also SANCO/3065/99-Final, 2003

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Version / remarks:

(1981)

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

(R)-2-(4-chloro-2-methylphenoxy)propionic acid

EC Number:

240-539-0

EC Name:

(R)-2-(4-chloro-2-methylphenoxy)propionic acid

Cas Number:

16484-77-8

Molecular formula:

C10H11ClO3

IUPAC Name:

(2R)-2-(4-chloro-2-methylphenoxy)propanoic acid

Constituent 2

Reference substance name:

Mecoprop-P acid

IUPAC Name:

Mecoprop-P acid

Constituent 3

Reference substance name:

MCPP-P acid

IUPAC Name:

MCPP-P acid

Details on test material:

- Stability under test conditions: The stability of the test substance suspensions over a period of up to 24 hours at room temperature was demonstrated.

Test animals

Species:

rat

Strain:

Wistar

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Strain: Chbb:THOM (SPF)
- Source: Karl Thomae, Biberach an der Riss, FRG
- Age at study initiation: about 61 or 66 days old
- Weight at study initiation: mean 222.8 g
- Housing: housed singly in type DK III stainless steel wire mesh cages supplied by BECKER & CO., Castrop-Rauxel, FRG
- Diet and water: ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 - 24 °C
- Humidity (%): 30 - 70 %
- Air changes (per hr): no data (fully air-conditioned rooms)
- Photoperiod (hrs dark / hrs light): 12 / 12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: 0.5% aqueous carboxymethyl cellulose solution (Tylose CB 30.000)

Details on exposure:

The volume administered each day was 10 ml/kg body weight. The calculation of the volume administered was based on the individual body weight determined at the beginning of the administration period (day 6 p.c.).

PREPARATION OF DOSING SOLUTIONS: Each day the test substance suspensions were freshly prepared shortly before the test substance was administered. For the preparation of the suspensions, an appropriate amount of the test substance was weighed and subsequently suspended in a 0.5% aqueous carboxymethyl cellulose solution using a high speed sonicator (Ultra Turrax, JANKE & KUNKEL KG, FRG). A magnetic stirrer was used to keep the suspensions homogeneous during treatment of the animals.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analytical verifications of the stability of the test substance suspensions up to 24 hours were carried out before the beginning of the study. The stability of the test substance suspensions was checked in a range-finding study in a comparable batch. Samples of the test substance suspensions were sent to the analytical laboratories twice during the study period for verification of the concentrations. The samples which were sent for the first concentration control analysis toward the beginning of the administration period were also used to verify the homogeneity for the samples of the low and the high concentrations (20 and 100 mg/kg body weight/day). 6 samples (2 from the top, middle and bottom in each case) were taken for each of these concentrations from the beaker with a magnetic stirrer running.
The test substance suspensions were analyzed by HPLC.

Details on mating procedure:

After an acclimatization period of at least 5 days, 4 untreated female rats were mated with one untreated fertile male animal of the same breed.
Mating took place from about 16.00 hours to about 7.30 hours on the following day. If sperm were detected microscopically in the vaginal smear in the morning, the animals were considered to be fertilized. This day was designated "day 0" (beginning of the study) and the following day "day 1" post coitum (p.c.).

Duration of treatment / exposure:

During the period of major organogenesis (day 6 to day 15 p.c.).

Frequency of treatment:

Once a day always at approximately the same time of day (in the morning).

Duration of test:

On day 20 p.c., all females were sacrificed in a randomized order and examined macroscopically. The fetuses were dissected from the uterus and further investigated with different methods.

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 20, 50, 100 mg/kg bw/day Mecoprop-P (R-isomer)
Basis:
actual ingested

No. of animals per sex per dose:

25

Control animals:

yes, concurrent vehicle

Details on study design:

- Due to technical reasons, the study was carried out in 2 sections. Each dose group was represented in each section. A treatment interval of 2 days elapsed before the next section.

- Dose selection rationale: 20 mg/kg bw as the expected NOAEL, 50 mg/kg bw as a dose which might be a minimal toxic effect level for dams and/or fetuses, 100 mg/kg bw as the dose with maternally toxic effects at which findings in fetuses may also be obtained. This doses were fixed for the full-scale prenatal toxicity study on basis of the below mentioned studies.

In an older prenatal toxicity study*, pregnant Sprague-Dawley rats (28 - 38/group) were daily administered Mecoprop (racemic form) as aqueous methyl cellulose preparation (10 mL/kg bw) from day 6 to day 15 p.c. at doses of 0, 20, 50, and 125 mg/kg body weight and day. The following possibly substance-induced findings were obtained:
- dose-dependently decreased food consumption
- slightly retarded body weight gain of the dams of the 125 and 50 mg/kg groups
- increased postimplantation loss at 125 mg/kg bw/day
- decreased mean fetal weight and diminished fetal length in the 125 mg/kg group
(*Mecoprop oral teratogenicity study in the rat, Hazleton Laboratories Europe Ltd., Otley Road, Harrogate, England, 1980)

In two range-finding studies, Mecoprop (racemic form)** or Mecoprop-P (D-form, R-isomer)*** were administered to pregnant rats (10/dose) by gavage from day 6 to day 15 post coitum at doses of 0, 50, 100 and 150 mg/kg bw and day. For a clear assessment of substance-related effects on the dams, the animals were sacrificed on day 16 p.c. Just before sacrifice, blood samples were taken for clinicochemical and hematological examinations. Furthermore, liver and kidneys were weighed. Due to the sacrifice of the dams on day 16 p.c., only limited information on embryonic and fetal toxicity could be obtained.
Findings:
Mecoprop (racemic form) - 150 mg/kg bw:
reduced food consumption, effects on body weight gain (reduced), effects on hematologic parameters (reduction of erythrocytes, hemoglobin, hematocrit, platelets, thromboplastin time increased), effects on clinical chemistry (increase of alkaline phosphatase, creatinine, glucose; decrease of anorganic phosphate, calcium, total protein, globulin, triglyceride, cholesterol), increased relative liver and kidney weights, increased postimplantation loss due to the increased number of early and late resorptions, reduced number of live fetuses/dam, questionable decrease of mean fetal bodyweights.
Mecoprop (racemic form) - 100 mg/kg bw:
reduced food consumption, effects on body weight gain (reduced), effects on hematologic parameters (reduction of erythrocytes, hemoglobin, hematocrit, platelets), effects on clinical chemistry (increase of alkaline phosphatase; decrease of anorganic phosphate, calcium, total protein, globulin, triglyceride, cholesterol), increased relative liver weights.
Mecoprop (racemic form) - 50 mg/kg bw:
marginally reduced food consumption, marginally effects on body weight gain (reduced), decreased triglyceride.
Mecoprop-P (D-form, R-isomer) - 150 mg/kg bw:
reduced food consumption, effects on body weight gain (reduced), effects on hematologic parameters (reduction of erythrocytes, hemoglobin, hematocrit, platelets), effects on clinical chemistry (increase of alanine aminotransferase, alkaline phosphatase, decrease of total protein, globulin, triglyceride, cholesterol), increased relative liver and kidney weights, increased postimplantation loss due to the increased number of early and late resorptions, reduced number of live fetuses/dam, decrease of mean fetal bodyweights.
Mecoprop-P (D-form, R-isomer) - 100 mg/kg bw:
reduced food consumption, effects on body weight gain (reduced), effects on red blood parameters (reduction of erythrocytes, hemoglobin, hematocrit, platelets), effects on clinical chemistry (increase of alanine aminotransferase, alkaline phosphatase glucose; decrease of total protein, globulin, triglyceride, cholesterol), increased relative liver weights, slightly increased postimplantation loss.
Mecoprop-P (D-form, R-isomer) - 50 mg/kg bw:
marginally reduced food consumption, marginally effects on body weight gain (reduced), effects on red blood parameters (reduction of hemoglobin, hematocrit), decreased cholesterol.
(**Results of a range-finding prenatal toxicity study with Mecoprop (MCPP racemic) in rats after oral administration (gavage); project no 10R0047/83080, BASF AG, 1990; ***Results of a range-finding prenatal toxicity study with Mecoprop (optically active D-form of MCPP) in rats after oral administration (gavage); project no 10R0342/90027, BASF AG, 1990)

Examinations

Maternal examinations:

CLINICAL EXAMINATIONS: Yes
The animals were examined for clinical symptoms at least once a day, or more often when clinical signs of toxicity were elicited (days 0 - 20 p.c.). A check for mortality was made twice a day on working days or once a day (Saturday, Sunday or on public holidays) (days 0 - 20 p.c.).

BODY WEIGHT: Yes
All animals were weighed on days 0, 1, 3, 6, 8, 10, 13, 15, 17 and 20 p.c. The body weight change of the animals was calculated from these results. Furthermore, the corrected body weight gain was calculated after terminal sacrifice (terminal body weight on day 20 p.c. minus weight of the uterus before it was opened minus body weight on day 6 p.c.).

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
With the exception of day 0, the consumption of food was determined on the same days as was body weight.

POST-MORTEM EXAMINATIONS: Yes
On day 20 p.c., the dams were sacrificed in randomized order by cervical dislocation and the fetuses dissected from the uterus.
After the dams had been sacrificed, they were necropsied and assessed by gross pathology.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Cesarean sections were performed on day 20 p.c.
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Number of dead and live fetuses: Yes
- Other: Individual placental weights were recorded.

Fetal examinations:

The fetuses were dissected from the uterus, sexed, weighed and further investigated for any external, soft tissue and/or skeletal findings.
At necropsy each fetus was weighed, sexed and examined macroscopically for any external findings. The sex was determined by observing the distance between the anus and the base of the genital tubercle and was later confirmed in all fetuses fixed in BOUIN'S solution by internal examination. If there were discrepancies between the "external" and the "internal" sex of a fetus, the fetus was finally sexed according to the appearance of its gonads.
Furthermore, the viability of the fetuses and the condition of the placentae, the umbilical cords, the fetal membranes and fluids were examined.
After these examinations, approximately one half of the fetuses per dam was placed in ethyl alcohol and the other half was placed in BOUIN's solution for fixation and further evaluation.
- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: No data

Statistics:

DUNNETT's Test was used for statistical evaluation of food consumption, body weight, body weight change, corrected body weight gain (net maternal body weight change), weight of the uterus before it was opened, weight of fetuses, weight of placentae, corpora lutea, implantations, pre- and postimplantation losses, resorptions and live fetuses.
FISHER's Exact Test was used for statistical evaluation of conception rate, mortality (of the dams) and all fetal findings.

Indices:

Calculations of conception rate (in %) and pre- and postimplantation losses (in %) were carried out.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Details on maternal toxic effects:
Cited from Mecoprop-P, EU Review Programme on active substances in Plant Protection Products, Scientific Evaluation and Assessment, The Danish Environmental Protection Agency, Draft December 1998 (Volume 3, Annex B) and Addendum II July 2002:
"In the control group one animal was not pregnant. In the mecoprop-P dosed groups 5, 2, and 5 females were not pregnant in the 20, 50, and 100 mg/kg bw/day groups, respectively. The resulting conception rate varied between 96% (control group) and 80% (the 20 and 100 mg/kg bw/day groups). Only pregnant females were used for calculation of food consumption, body weight and body weight change. The food consumption was significantly reduced in the 50 mg/kg bw/day group from day 6-8 post coitus (p<0.05), and in the 100 mg/kg bw/day group from day 6-10 post coitus (p<0.01). Both the body weight at day 8 (p<0.05) and body weight gain during days 6-15 (p<0.01), and corrected body weight gain (p<0.01) were impaired at 100 mg/kg bw/day.
Clinical symptoms were not seen in any of the dams, and no mortalities occurred. At necropsy no substance related observations were done, and the uterus weight was not affected by treatment."

Effect levels (maternal animals)

1

Dose descriptor:

NOAEL

Effect level:

50 mg/kg bw/day (actual dose received)

Basis for effect level:

other: maternal toxicity

2

Dose descriptor:

NOAEL

Effect level:

50 mg/kg bw/day (actual dose received)

Basis for effect level:

other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Details on embryotoxic / teratogenic effects:
Cited from Mecoprop-P, EU Review Programme on active substances in Plant Protection Products, Scientific Evaluation and Assessment, The Danish Environmental Protection Agency, Draft December 1998 (Volume 3, Annex B) and Addendum II July 2002:
"There were no effect of treatment on sex distribution of the foetuses, and the weight of the placentae. Weight of the foetuses was slightly (p<0.05) reduced in the 100 mg/kg bw/day group. At the external examination of the foetuses fused placenta was observed in one foetus of each of the 50 and 100 mg/kg bw/day groups. At the soft tissue examination of the foetuses no substance related changes were seen. Dilated renal pelvis and/or hydroureter was detected in all groups at levels within the range of biological variation.
In the skeletal examination the occurrence of rudimentary cervical ribs was significantly (p<0.01) increased in the 100 mg/kg bw/day group, and the number of foetuses with not ossified sternebrae was also significantly (p<0.01) increased (Table 5.6.2.2-1). These increases are clearly dose related. There was no indication of a substance related occurrence of malformations."

At 50 mg/kg and 20 mg/kg no substance-related effects on fetuses observed. At 100 mg/kg statistically significantly increased number of fetuses with a skeletal variation (rudimentary cervical rib(s)).

Effect levels (fetuses)

Dose descriptor:

NOAEL

Effect level:

100 mg/kg bw/day (actual dose received)

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

Basic teratogenicity data for Mecoprop-P

Dose (mg/kg bw/day)	0	20	50	100
No. of mated rats	25	25	25	25
No. of pregnant rats	24	20	23	20
No. of implantations/rat	13.8	14.9	13.8	14.9
No. of live foetuses/rat	12.8	13.8	13.1	13.9
Mean foetal weight (g)	4.0	4.0	4.0	3.9^#
Rudimentary cervical ribs (foetal incidence)	6	5	9	26
Sternebrae not ossified	6	12	8	24^##

^# significant p<0.05, ^## significant p<0.01

Applicant's summary and conclusion

Executive summary:

A developmental toxicity study according to OECD TG 414 was conducted with Mecoprop-P (R-isomer).

Four groups of 25 mated female Wistar rats received doses of 0, 20, 50 and 100 mg/kg bw by gavage from day 6 to 15 of gestation. The test substance was given in a 0.5% aqueous carboxymethyl cellulose suspension with a standard dose volume of 10 mL/kg. Food consumption and body weights of the animals were recorded regularly throughout the study period and the state of health of the animals was checked each day. On day 20 post coitum, all females were sacrificed and assessed by gross pathology. The fetuses were dissected from the uterus, sexed, weighed and further investigated for any external, soft tissue and/or skeletal findings.

For summary and assessment of findings see citation below.

 

Cited from Mecoprop-P, EU Review Programme on active substances in Plant Protection Products, Scientific Evaluation and Assessment, The Danish Environmental Protection Agency, Draft December 1998 (Volume 3, Annex B) and Addendum II July 2002:

"In the 100 mg/kg bw/day group dams the statistically significant reduced food consumption during days 6-10 post coitus and the statistically significant lower body weight gain day 6-15 are clearly effects related to dosing.

No adverse effects were seen in the dams at 50 mg/kg bw/day.

In the foetuses the decreased foetal weight, and the increases in skeletal variations (rudimentary cervical ribs) and in retardations (not ossified sternebrae) are clear indications that foetotoxicity occurred at 100 mg/kg bw/day.

No foetotoxicity was seen at 50 and 20 mg/kg bw/day.

The LOAEL for foetotoxicity is under the conditions of this study 100 mg/kg bw/day, and the NOAEL is 50 mg/kg bw/day.

For maternal toxicity the LOAEL is 100 mg/kg bw/day, and the NOAEL is 50 mg/kg bw/day."