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

Carcinogenicity

Description of key information

2-Year Rat Diet: Not Carcinogenic. GLP study; Reliability = 2

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

Additional documentation provided in IUCLID assesment reports (Chapter 13) supports the read across approach

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

no guideline followed

Principles of method if other than guideline:

The 2-year dietary study conducted to assess the potential chronic toxicity and oncogenicity of the test substance after dietary administration to CDF Fischer 344 rats. Male and female rats were maintained on diets of test substance formulated to provide 0, 0.01, 0.03, 0.065, or 0.10 and 0, 0.01, 0.03, 0.065, or 1.0 mg/kg body weight/day, respectively. Parameters evaluated included: body weight, food consumption, in-life clinical observations/palpable masses, hematology, clinical chemistry, urinalyses, gross pathology, organ weight, and histopathology.

GLP compliance:

yes

Specific details on test material used for the study:

DOWCO 453
Lot # AGR 187381
Purity: 99.6%

Species:

rat

Strain:

other: CDF Fischer 344

Details on species / strain selection:

CDF Fischer 344 strain was selected because of the available historical data, reliable commercial source and general acceptance for use in toxicity studies.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc., Portage, Michigan.
- Housing: Two per cage
- Diet: Purina Certified Rodent Chow, ad libitum
- Water: ad libitum
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature: 22±2°C
- Humidity: 40-60%
- Air changes: 10-12 per hr
- Photoperiod: 12 hrs dark /12 hrs light

Route of administration:

oral: feed

Details on exposure:

DIET PREPARATION
- Test material/feed concentrates (premixes) containing the test substance were prepared biweekly during the study. Treated diets were prepared at weekly intervals through the first 3 months of the study and biweekly thereafter through the 2-year sacrifice by serially diluting the 5E-3 or 5E-4% premixes with Purina Certified Laboratory Rodent Chow #5002.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Assay of the diets for the test substance concentrations, using an electron capture/gas chromatograph technique, was conducted on all test diets for weeks 1, 15, 38, 51, 67, 79, 91, and 103. Results of these analyses indicate that over the duration of the study the mean concentration for all dose levels ranged from 92% to 100% of the targeted concentration

Duration of treatment / exposure:

2 years

Frequency of treatment:

daily

Dose / conc.:

0.01 mg/kg bw/day

Remarks:

Male/Female

Dose / conc.:

0.03 mg/kg bw/day

Remarks:

Male/Female

Dose / conc.:

0.065 mg/kg bw/day

Remarks:

Male/Female

Dose / conc.:

0.1 mg/kg bw/day

Remarks:

Male

Dose / conc.:

1 mg/kg bw/day

Remarks:

Female

No. of animals per sex per dose:

50

Control animals:

yes, plain diet

Observations and examinations performed and frequency:

OBSERVATIONS: All rats were generally observed twice daily for overt signs of toxicity or changes in demeanor. Monitoring on weekends and holidays consisted of performing routine animal husbandry procedures which ensured availability of food and water.

BODY WEIGHT: Body weights were recorded weekly on all rats for the first three months of the study and once per month thereafter.

FOOD CONSUMPTION: Food consumption was determined weekly for all rats during the first three Months and over a period of one week each month for the remainder of the study.

HAEMATOLOGY
- Hematologic evaluations of packed cell volume (PCV), hemoglobin (Hgb), red cell indices (MCV, MCH, and MCHC) and the total erythrocyte (RBC), leukocyte (WBC), and platelet (PLT) counts were done on 19 or 20 rats/sex/dose at 18 months (days 547-550) and all surviving rats at 24 months (days 714-721). Stained blood smears were prepared from all of these animals, but only those from the control and high-dose groups were examined and differential leukocyte counts determined.

CLINICAL CHEMISTRY
- Clinical chemistry parameters evaluated from 19 or 20 rats/sex/dose at 18 months and from all surviving rats at 24 months included: serum concentrations of urea nitrogen (BUN), glucose (Gluc), total protein (TP), albumin (Alb), globulin (Glob), and enzyme activity of alkaline phosphatase (AP) and glutamic-pyruvic transaminase (SGPT).

URINALYSIS
- Urine was analyzed for specific gravity and a semiquantitative estimate of pH, protein, glucose, blood, ketones, bilirubin and urobilinogen. Samples were obtained at the same time and on the same animals as the blood samples for hematologic determinations.

Sacrifice and pathology:

GROSS PATHOLOGY
All rats surviving until the 24-month sacrifice were fasted overnight, weighed and subjected to a complete gross necropsy examination. Eyes were examined by means of a moist glass slide technique. The weights of the brain, heart, liver, kidneys, and testes were determined following examination. A complete set of tissues from each rat was collected and preserved in neutral phosphate-buffered 10% formalin. The lungs were infused with formalin to their approximate normal inspiratory volume and the nasal passages were gently flushed with fixative. Testes and epididymides were fixed in Bouin's solution. Rats which died spontaneously or were sacrificed in a moribund condition were necropsied in a similar manner, however, final body and organ weights were not obtained and testes and epididymides were fixed in formalin. Eyes from rats dying spontaneously were not examined by the glass slide technique due to the rapid onset of postmortem artifacts.
The tissues obtained and preserved from all animals at the time of necropsy are: liver, heart, skeletal muscle, pituitary, bone marrow, small intestine, mesenteric lymph node, epididymis, prostate, uterus, urinary bladder, mediastinal tissue, esophagus, trachea, mammary gland, lacrimal/Harderian gland, any gross mass or lesion, spleen, salivary gland, peripheral nerve, adrenal, cecum, mesenteric tissue, seminal vesicle, ovary, cervix, lungs, mediastinal lymph node, thyroid gland, larynx, eye, kidney, pancreas, brain, spinal cord, stomach, large intestine, testicle, coagulating gland, oviduct, vagina, thymus, aorta, parathyroid gland, skin, nasal tissues, oral tissues.
The tissues obtained but are not routinely evaluated histologically are: bone/sternum, auditory sebaceous gland, tongue (with lower jaw), clitoral/preputial gland.

HISTOPATHOLOGY
A complete set of tissues was processed for histologic evaluation from 1) aII control and high-dose rats; and, 2) intermediate-dose level rats which died or were sacrificed in a moribund condition prior to the scheduled 24-month sacrifice. The liver, kidneys, spleen, pancreas, pituitary gland, adrenal glands, thyroid/parathyroid glands, testes, and any tissue which had a gross necropsy observation suggestive of a neoplasm were prepared for histologic evaluation from all intermediate dose level rats which were sacrificed at 24 months.

Statistics:

Body weights collected through day 546 and clinical chemistry, hematology (excluding red cell indices and differential white cell counts), and urine specific gravity obtained at 18 months were evaluated by Bartlett's test for equality of variances. Based on the outcome of Bartlett's test, a parametric or nonparametric analysis of variance was performed followed respectively by Dunnett's test or the Wilxocon Rank-Sum Test with Bonferroni's correction if the ANOVA was significant. Outliers were identified by the sequential outlier test.
Cumulative mortality data are tabulated monthly and analyzed for overall differences by the Gehan-Wilcoxon test. Since there is no significant difference in mortality, cumulative 24-month histopathology data are analyzed without adjustment for differential survival rates. For histopathologic observations, treatment group comparisons of cumulative incidence are examined primarily by Fisher's Exact Probability Test.
In the absence of a positive Fisher's test for a histopathologic lesion, the Cochran-Armitage test for a linear trend in incidence is performed, providing the requirements for a valid chi-square statistic are met (i.e., no expected value less than 2).
Statistical analyses of histopathologic data from low- and mid-dose as well as high-dose animals, are performed on those tissues which are processed for all rats: liver, kidneys, spleen, pancreas, pituitary gland, adrenal glands, thyroid/parathyroid glands, and testes. For all other tissues, only control versus high-dose comparisons are statistically made; consequently, no trend tests or Bonferroni corrections are used. However, gross and histological observations made on low- and mid-dose animals are always considered in the final assessment of treatment related effects.

Mortality:

mortality observed, non-treatment-related

Description (incidence):

22, 30, 28, 22 and 16 males died in control, 0.01, 0.03, 0.065 and 0.1 mg/kg/day groups, respectively.
24, 20, 12, 20 and 20 females died in control, 0.01, 0.03, 0.065 and 1.0 mg/kg/day groups, respectively

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

slight decrease in the kidney weight (absolute and relative) observed in high-dose female rats.

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

very slight increase in the quantity of renal pigment histopathologically observed in the proximal convoluted tubules of high-dose female rats

Histopathological findings: neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

Evaluation of the incidence of specific tumor types or groups of tumors, whether benign or malignant did not demonstrate an increase which is interpreted to be treatment related. During the course of the study a few observations suggestive of a neoplasm could not be histopathologically examined due to cannibalism or the inability to locate the lesion grossly or microscopically. These missing lesions were few in number and distributed throughout the dose levels indicating that they would have no effect on the interpretation of the oncogenic portion of the study.

Relevance of carcinogenic effects / potential:

The results indicate that the administration of the test substance was not associated with an increase in the incidence of neoplasms.

Key result

Dose descriptor:

NOEL

Effect level:

0.065 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

organ weights and organ / body weight ratios

Table 1: Organ weight data (significant observations)

	Dose (mg/kg/day)	Absolute kidney weight (g)	Relative kidney weight (g/100 g)
Males	0	2.896 ±0.241	0.778 ±0.076
	0.01	3.003 ±0.375	0.747 ±0.092
	0.03	2.897 ±0.320	0.722 ±0.067
	0.065	2.814 ±0.266	0.722 ±0.064
	0.1	2.856 ±0.357	0.724 ±0.092
Females	0	2.056 ±0.224	0.798 ±0.099
	0.01	2.035 ±0.166	0.815 ±0.119
	0.03	2.013 ±0.264	0.769 ±0.101
	0.065	1.972 ±0.232	0.767 ±0.096
	1.0	1.893 ±0.176	0.723 ±0.061

 

Table 2: Histopathological observations of Kidneys (significant observations)

				Males					Females
Dose (mg/kg/day)		0	0.01	0.03	0.065	0.1	0	0.01	0.03	0.065	1.0
Increased pigment, tubules	Very slight	0	0	0	0	0	1	1	0	2	24*

*Indicates a statistical difference from the control group, Fischer's Exact Probability Test,α=0.05, one-sided.

Conclusions:

Rat NOEL: 0.065 mg/kg/day

Executive summary:

A 2-year dietary study in Fischer 344 rats has been completed to assess the chronic toxicity and oncogenicity of the test substance. Male and female rats were maintained on diets of the test substance formulated to provide 0, 0.01, 0.03, 0.065, or 0.10 and 0, 0.01, 0.03, 0.065, or 1.0 mg/kg body weight/day, respectively. Parameters evaluated included: body weight, food consumption, in-life clinical observations/palpable masses, hematology, clinical chemistry, urinalyses, gross pathology, organ weight, and histopathology.

The administration of the test substance was not associated with an increase in the incidence of neoplasms in any organ or tissue.

Treatment-related nontumorous effects were noted in the kidneys of the high dose level female rats designated for sacrifice at 24 months and consisted of a very slight increase in the amount of pigment within the kidneys and a slight decrease in organ weight. This was not considered an adverse effect as demonstrated by the lack of an increase in the incidence or severity of renal disease.

Similar treatment-related effects were also observed in the high dose level male and/or female rats at the 6- and 12-month interim sacrifices. Although treatment-related effects in liver, hematologic and clinical chemistry parameters were seen at the 6- and 12-month interim sacrifices similar effects were not apparent from the data collected at 18 or 24 months.

Treatment-related effects were not observed in male or female rats administered 0.01, 0.03, or 0.065 mg/kg body weight/day thereby establishing the no-observable-effect-level (NOEL) at 0.065 mg/kg/day.

Reference 2

Endpoint:

carcinogenicity: oral

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Additional documentation provided in IUCLID assesment reports (Chapter 13) supports the read across approach

Reason / purpose for cross-reference:

read-across source

Key result

Dose descriptor:

NOEL

Effect level:

0.065 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

organ weights and organ / body weight ratios

Conclusions:

Rat NOEL: 0.065 mg/kg/day

Executive summary:

A 2-year dietary study in Fischer 344 rats has been completed to assess the chronic toxicity and oncogenicity of the test substance. Male and female rats were maintained on diets of the test substance formulated to provide 0, 0.01, 0.03, 0.065, or 0.10 and 0, 0.01, 0.03, 0.065, or 1.0 mg/kg body weight/day, respectively. Parameters evaluated included: body weight, food consumption, in-life clinical observations/palpable masses, hematology, clinical chemistry, urinalyses, gross pathology, organ weight, and histopathology.

The administration of the test substance was not associated with an increase in the incidence of neoplasms in any organ or tissue.

Treatment-related nontumorous effects were noted in the kidneys of the high dose level female rats designated for sacrifice at 24 months and consisted of a very slight increase in the amount of pigment within the kidneys and a slight decrease in organ weight. This was not considered an adverse effect as demonstrated by the lack of an increase in the incidence or severity of renal disease.

Similar treatment-related effects were also observed in the high dose level male and/or female rats at the 6- and 12-month interim sacrifices. Although treatment-related effects in liver, hematologic and clinical chemistry parameters were seen at the 6- and 12-month interim sacrifices similar effects were not apparent from the data collected at 18 or 24 months.

Treatment-related effects were not observed in male or female rats administered 0.01, 0.03, or 0.065 mg/kg body weight/day thereby establishing the no-observable-effect-level (NOEL) at 0.065 mg/kg/day.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Study duration:

chronic

Quality of whole database:

Carcinogenicity study data is available in rats

Carcinogenicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Carcinogenicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Based on the results of chronic feeding study in rats, it can be concluded that the test substance does not pose a carcinogenic concern for humans. Therefore, the test substance is not classified for carcinogenicity according to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.

Additional information

A 2-year dietary study in Fischer 344 rats has been completed to assess the chronic toxicity and oncogenicity of the test substance. Male and female rats were maintained on diets of the test substance formulated to provide 0, 0.01, 0.03, 0.065, or 0.10 and 0, 0.01, 0.03, 0.065, or 1.0 mg/kg body weight/day, respectively. Treatment-related nontumorous effects were noted in the kidneys of the high dose level female rats designated for sacrifice at 24 months and consisted of a very slight increase in the amount of pigment within the kidneys and a slight decrease in organ weight. This was not considered an adverse effect as demonstrated by the lack of an increase in the incidence or severity of renal disease. Similar treatment-related effects were also observed in the high dose level male and/or female rats at the 6- and 12-month interim sacrifices. Although treatment-related effects in liver, hematologic and clinical chemistry parameters were seen at the 6- and 12-month interim sacrifices similar effects were not apparent from the data collected at 18 or 24 months. Treatment-related effects were not observed in male or female rats administered 0.01, 0.03, or 0.065 mg/kg body weight/day thereby establishing the no-observable-effect-level (NOEL) at 0.065 mg/kg/day.