Methyl (R)-2-(4-(3-chloro-5-trifluoromethyl-2-pyridyloxy)phenoxy)propionate

Repeated dose toxicity: dermal

Administrative data

Endpoint:

sub-chronic toxicity: dermal

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2013

Report date:

2013

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 410 (Repeated Dose Dermal Toxicity: 21/28-Day Study)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.9 (Repeated Dose (28 Days) Toxicity (Dermal))

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.3200 (Repeated Dose Dermal Toxicity -21/28 Days)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Methyl (R)-2-(4-(3-chloro-5-trifluoromethyl-2-pyridyloxy)phenoxy)propionate

EC Number:

406-250-0

EC Name:

Methyl (R)-2-(4-(3-chloro-5-trifluoromethyl-2-pyridyloxy)phenoxy)propionate

Cas Number:

72619-32-0

Molecular formula:

C16H13ClF3NO4

IUPAC Name:

methyl 2-(4-{[3-chloro-5-(trifluoromethyl)pyridin-2-yl]oxy}phenoxy)propanoate

Test material form:

solid

Specific details on test material used for the study:

Haloxyfop-R-Methyl Ester
Lot # OC30150101 (TSN102229)
Purity: 96.7% R + 1.09% S

Test animals

Species:

rat

Strain:

Wistar

Details on species / strain selection:

The rat (Rattus norvegicus) was selected as a test system because it is a readily available laboratory rodent species. It has been historically shown to be a suitable model for repeated dose toxicity studies. The OECD and other regulatory authorities also recommend it. The results of the study are believed to be of value in predicting the toxicity of the test item to man.

Sex:

male/female

Administration / exposure

Type of coverage:

semiocclusive

Vehicle:

corn oil

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Triplicate samples from each concentration and corn oil (Vehicle) were sent for homogeneity and active ingredient concentration analysis on day 1. The results of A.I. concentration and homogeneity from the samples collected on day 1 (pre-dosing) revealed mean percent recovery of 107, 110 and 108 at the concentrations of 2 (low dose), 10 (mid dose) and 50 (high dose) mg/mL, respectively. The homogeneity and active ingredient content of the test substance in corn oil was within the allowable limit of ± 15% of nominal concentration.

Duration of treatment / exposure:

6 h

Frequency of treatment:

Daily

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

2 mg/kg bw/day

Remarks:

G2 (Low dose)

Doses / concentrations 2

Dose / conc.:

10 mg/kg bw/day

Remarks:

G3 (Mid dose)

Doses / concentrations 3

Dose / conc.:

50 mg/kg bw/day

Remarks:

G4 (High dose)

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Description (incidence and severity):

No abnormality was observed in any animal during the detailed physical examination of animals.

Dermal irritation:

no effects observed

Description (incidence and severity):

No local skin reaction was observed in any treatment group during the study period.

Mortality:

no mortality observed

Description (incidence):

No mortality or morbidity was observed in any group throughout the study period.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

No statistically significant changes in mean body weight and body weight change were observed in any treatment group when compared to the control group throughout the study period.

Food consumption and compound intake (if feeding study):

effects observed, non-treatment-related

Description (incidence and severity):

A statistically significant increase (27.49%) in mean food consumption was observed in the female rats of the high dose group (G4-50 mg/kg b. wt.) during day 1-8 when compared with the control group (G1-0 mg/kg b. wt.) which was not considered as a treatment-related finding as this was not observed during subsequent periods of the study.
No other differences in the mean food consumption were observed for male and female rats of treatment groups compared to control group during the study.

Ophthalmological findings:

no effects observed

Description (incidence and severity):

No ophthalmological changes were observed in male and female rats of any group.

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

A statistically significant increase (23.71 %) in platelet count of male rats from the mid dose group (G3) and decrease (17.50 %) in female rats of the high dose group (G4) was observed when compared with the control group. These variations observed in platelet counts were either inconsistent or not dose-dependent and, hence, were not considered as treatment-related findings. All other haematological parameters among different dose groups were comparable with the control group.

Clinical biochemistry findings:

effects observed, non-treatment-related

Description (incidence and severity):

Statistically significant increase in albumin level (4.89 %) and ALB:GLB ratio (33.53 %), and a reduction (21.46 %) in globulin level of male rats from the high dose group (G4) were observed when compared with the control group. These changes were within historical control data of testing laboratory (albumin: 4.33-5.11 g/dL, globulin: 1.24-3.34 g/dL and ALB:GLB ratio:1.38 - 3.99) hence, all these variations were not considered as treatment-related findings. All other clinical chemistry parameters among different dose groups were comparable with the control group.

Urinalysis findings:

no effects observed

Description (incidence and severity):

All the urine analysis parameters in both males and females from the treatment (G2 to G4) groups were comparable with the control (G1) group.

Organ weight findings including organ / body weight ratios:

effects observed, non-treatment-related

Description (incidence and severity):

The terminal body weight, absolute organ weight and relative organ weight in all the animals belonging to all the treated groups (G2 to G4) were comparable with the control group (G1). However, although not statistically significant, there was slight increase (8.26% and 6.80% in males and females, respectively) in absolute liver weight of the animals belonging to the high dose group (G4). This change was of slight magnitude without an evidence of any histopathological finding and thus, was considered not related to the treatment with the test item.

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

External and internal examination of terminally sacrificed animals did not reveal any lesions of pathological significance.

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

Microscopic examination did not reveal any treatment related lesion of pathological significance.

Effect levels

Key result

Dose descriptor:

NOAEL

Effect level:

>= 50 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Applicant's summary and conclusion

Conclusions:

21-Day Dermal Rat NOAEL (male/female): ≥50 mg/kg b. wt./day

Executive summary:

The study was conducted to determine the systemic toxicity potential of the test substance in Wistar rats following 21 days of repeated dermal exposure. This study was performed as per the requirements of guidelines of European Commission for repeated dose (28 Days) toxicity (Dermal), January 1997, guideline of OECD N° 410 (May 12, 1981) and guideline of US EPA OPPTS 870.3200 (August 1998).

A total of 20 male and 20 female Wistar rats were randomly allocated into four groups. Each group comprised 5 male and 5 female rats. Not less than 10 percent of the body surface area was clipped free of hair 24 h prior to the first dermal application of the test substance and weekly thereafter. One group (G1) served as the control and was treated with corn oil at a dose volume the same as that used for the high dose group. The other groups were treated at the dose levels of 2 mg/kg b. wt./day (G2), 10 mg/kg b. wt./day (G3) and 50 mg/kg b. wt./day (G4) of the test substance through dermal application. The test substance was applied over the clipped area by a single dermal application and was held in contact with the skin using porous gauze dressing and a non-irritating tape throughout the 6 h of exposure every day to prevent any loss of the test substance and also to ensure that the animals did not lick or ingest it. At the end of the exposure period, the residual test substance was removed using cotton moistened with corn oil. The fixed dose volume of 1 mL/kg b. wt. was used to dose each of the animals. The dose formulations were prepared by dissolving the test substance in corn oil. The dose formulation analysis was performed on day 1.

Each rat was observed for visible signs of reaction to treatment and for morbidity and mortality twice daily during the treatment period. All animals were observed for local skin reaction once daily as per protocol. The detailed clinical observations were performed before commencement of study and at weekly intervals until terminal sacrifice. Body weight was recorded on day 1 (prior to treatment) and at weekly intervals thereafter during the treatment period. Food consumption was calculated at weekly intervals until terminal sacrifice.

Ophthalmological examination was performed on all animals prior to commencement of treatment and prior to terminal sacrifice. Haematology, clinical chemistry investigation and urinalysis were performed on day 22 for all animals following an overnight fast.

All the terminally sacrificed rats were subjected to a detailed gross pathological examination. Absolute organ weights were recorded and relative organ weights were calculated for the organs viz., adrenals, brain, epididymides, heart, kidneys, liver, ovaries, spleen, testes, uterus, thyroid and parathyroid and thymus for all rats. Histopathological examination was carried out for the organs and tissues of G1 (control) and G4 (high dose group). As microscopic findings were observed in the livers of high dose group animals, histopathological examination was extended to the low and mid dose groups.

No mortality was observed during the study period. No clinical signs were observed in any animal from any of the groups.

No significant changes were observed in mean body weight and percent body weight change of male and female rats treated with the test substance in the low dose, mid dose and high dose groups when compared with the control group throughout the study period.

No treatment-related changes were observed in mean food consumption for treatment groups when compared with the control group.

No treatment-related alterations were observed in clinical pathology estimations for treatment groups when compared with the control group.

No significant changes were observed in mean terminal body weights, absolute organ weights and relative organ weights of animals from low dose, mid dose and high dose groups when compared with the control group.

External and internal examination of terminally sacrificed animals did not reveal any lesions of pathological significance. Microscopic examination did not reveal any treatment related lesion of pathological significance.

Based on the results of this study, it is concluded that the test substance did not produce any local as well as systemic adverse, treatment-related effects upto the dose level of 50 mg/kg b. wt./day after repeated dermal application for 21 days in Wistar rats. Hence, the NOAEL for the test substance is considered as ≥50 mg/kg b. wt./day under the conditions and procedures followed in the present study.