[[(2-ethylhexyl)oxy]methyl]oxirane

Repeated dose toxicity: dermal

Administrative data

Endpoint:

sub-chronic toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Study was performed according to test guideline and in compliant with GLP for Oxirane, mono[(C12-14-alkyloxy)methyl] derivs / ERC Nr 17, which is structurally similar to EHGE (EC#:219-553 -6). Thus, the study is used for read-across to avoid duplicate tests.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1997

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 411 (Subchronic Dermal Toxicity: 90-Day Study)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Oxirane, mono[(C12-14-alkyloxy)methyl] derivs.

EC Number:

271-846-8

EC Name:

Oxirane, mono[(C12-14-alkyloxy)methyl] derivs.

Cas Number:

68609-97-2

Molecular formula:

C15H30O2 + C17H34O2 + C19H38O2 + C12H26O + C14H30O + C30H60O4 + C32H64O4

IUPAC Name:

Oxirane, 2-((C12-14-alkyloxy)methyl)derivs

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

Male and female Fischer 344 rats from Charles River Laboratories Inc. (Raleigh, NC) were used in the study. Upon arrival at the laboratory (fully accredited by the Association for Assessment and Accreditation of Laboratory Animal Care International (AAALAC International)), the general health of each animal was evaluated by a laboratory veterinarian. The animals were housed two per cage in stainless steel wire cages and acclimated to the laboratory for at least one week prior to study start day.
Housing: Following randomization, rats were housed one per cage in stainless steel cages in rooms designed to maintain adequate conditions (temperature, humidity, and photocycle). Cages had wire-mesh floors and were suspended above catch pans containing absorbent cageboard. Cages contained a feed crock and a pressure activated nipple-type watering system.
Age at Start: Animals were approximately 8 weeks old at the study start.
Identification: Rats were uniquely identified via subcutaneously implanted transponders which were correlated to a unique identification number. The transponders were implanted caudal to the interscapular region (in the sacral region) to avoid interference with the dosing site.
Feed and Water: Animals were provided Purina Certified Rodent Chow #5002 (Purina Mills, Inc., St. Louis, MO) in meal form. Feed and tap water were provided ad libitum. Analysis of the chow was performed by Purina Mills Inc. to confirm the diet provided adequate nutrition and to quantify the levels of selected contaminants associated with the formulation process. Drinking water obtained from the City of Midland, Michigan was analyzed for chemical and biological contaminants by the City of Midland Water Department. In addition, specific analyses for chemical contaminants were conducted at periodic intervals as stated in the Standard Operating Procedures of The Toxicology Research Laboratory, The Dow Chemical Company. The feed and water did not contain unacceptable levels of any contaminant nor did they contain anything that would interfere with the interpretation of this study.
Randomization: Rats for both the range finding and 13-week studies were assigned one per cage to study groups using a computer-generated randomization program based on body weights. The dispositions of rats not placed on study were documented in the study file.
In-Life Dates
Range finding: October 8, 1996 to October 22, 1996 (test day 15).
Repeated Dose Study: November 20, 1996 to February 20, 1997 (test day 93).

Administration / exposure

Type of coverage:

open

Vehicle:

acetone

Details on exposure:

Dose solutions were mixed weekly (twice) during the range finding study and approximately monthly (4 times) during the 13 week study. Dose solutions were applied to the interscapular region of each rat. The application site (approximately 16 cm²) was clipped approximately 24 - 72 hours prior to the first application and as needed, thereafter.
The application site was not occluded, nor was the test material washed from the application site between doses. The concentration and dose volume was held constant throughout the dosing period. The volume of material applied and the relative portion of the skin surface to which it was applied represented the maximum levels recommended by the EPA.
For the range finding study, animals received 300 µL topical applications of AGE in acetone at concentrations of 0, 0.75%, 7.5% or 75% (male rats) or 0, 0.5%, 5% or 50% (female rats) 5 days/week for up to 2 weeks.
For the repeated dose study, animals received 300 µL topical applications of AGE acetone at concentrations of 0, 0.075%, 0.75% or 7.5% (male rats) or 0, 0.05%, 0.5% or 5% (female rats) 5 days/week for 13 weeks.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

No analytical verification was conducted on the range finding study dose solutions.
Stability and homogeneity of AGE in the acetone vehicle was established concurrent with the start of the 13-week study. Analyses to verify the concentration of the test material in the vehicle were conducted at the start, approximately midway through the dosing period and near the end of the 13-week study.

Duration of treatment / exposure:

continuous

Frequency of treatment:

5 days/week for 13 weeks

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

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

Remarks:

in main study

Doses / concentrations 2

Dose / conc.:

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

Remarks:

in main study

Doses / concentrations 3

Dose / conc.:

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

Remarks:

in main study

Doses / concentrations 4

Dose / conc.:

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

Remarks:

in main study

No. of animals per sex per dose:

10 rats/sex/dose level

Details on study design:

A range finding study was conducted in which two rats/sex/dose level were administered 0, 10, 100, or 1000 mg/kg/day AGE as acetone solutions, 5 days/week for up to 2 weeks via non-occluded dermal application. The high dose of 1000 mg/kg/day for the range finding study represented the limit test defined by several regulatory agencies for subchronic dermal studies. In-life observations, dermal scoring, gross pathology and limited histopathology were evaluated. Test material administration for all animals began on October 8, 1996. Animals from the high-dose were sacrificed after 4 applications due to the loss of integrity of the epidermis. Remaining male and female rats were necropsied on October 22, 1996 (test day 15).

In the non-occluded dermal repeated dose study, ten rats/sex/dose level were administered 0, 1, 10, or 100 mg/kg/day AGE as acetone solutions, 5 days/week for 13 weeks (66 total applications). Standard toxicologic parameters were evaluated. Test material administration for all animals began on November 20, 1996. Male and female rats were necropsied on February 20, 1997 (test day 93).

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
Observation for morbidity, moribundity, mortality, and the availability of feed and water was made each day of the work week, as well as twice daily on weekends.
Clinical examinations were conducted on all animals from the range finding and 13-week studies prior to the start of the study and weekly throughout the dosing periods. These examinations included careful, handheld evaluations of the skin, fur, mucous membranes, respiration, nervous system function (including tremors and convulsions), swelling, masses and animal behavior. A daily cageside examination was made each day of the work week and to the extent possible the above parameters were evaluated. A cageside was not necessary when a clinical examination was performed, since the clinical was a more thorough examination.
DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: weekly
DERMAL IRRITATION (if dermal study): Yes
- Time schedule for examinations: daily
BODY WEIGHT: Yes
- Time schedule for examinations: weekly
FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: Yes
WATER CONSUMPTION: No data, ad libitum
OPHTHALMOSCOPIC EXAMINATION: Yes
The eyes of all 13-week animals were examined by indirect ophthalmoscopy by a veterinarian prior to the dosing period and the week prior to necropsy. One drop of 0.5% tropicamide ophthalmic solution was instilled in each eye to produce mydriasis prior to examination.
HAEMATOLOGY: Yes
All animals were fasted overnight, anesthetized with methoxyflurane and blood samples collected via puncture of the orbital sinus. Hematology samples were mixed with EDTA and blood smears prepared and stained with Wright's Stain. No blood samples were collected from animals which died prior to their scheduled necropsy. Hematology parameters were analysed pre-study, at approximately 30 days and following 13-weeks administration on all repeated dose study animals. The following were assayed using a Technicon H.1E Hematology Analyzer (Miles, Inc., Tarrytown, New York): hematocrit, hemoglobin concentration, erythrocyte count, total leukocyte count, platelet count, automated differential counts, erythrocyte, leukocyte and platelet morphology.
- Time schedule for collection of blood: 0, 30, 90 days
- Anaesthetic used for blood collection: Yes (methoxyflurane)
- Animals fasted: Yes / No / No data
- How many animals: all

CLINICAL CHEMISTRY: Yes
All animals were fasted overnight, anesthetized with methoxyflurane and blood samples collected via puncture of the orbital sinus. Blood samples were allowed to clot in serum tubes and the sera were collected following centrifugation. No blood samples were collected from animals which died prior to their scheduled necropsy. Serum parameters were analysed pre-study, following approximately 30 days of dosing, and following 13 weeks administration for all repeated dose study animals. The following were assayed using a Monarch 2000 Chemistry System (Instrument Laboratory Inc., Lexington, Massachusetts): enzyme activities of alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, and creatine phosphokinase; concentrations of urea nitrogen, creatinine, total protein, albumin, globulin, glucose, total bilirubin, electrolytes (Na, K, P, Cl, Ca), cholesterol, and triglycerides.
- Time schedule for collection of blood: 0, 30, 90 days
- Animals fasted: Yes
- How many animals: all
URINALYSIS: Yes
-Urine samples were collected from all repeated dose study animals via manual compression of the abdomen after approximately 1 month of dosing and the week prior to necropsy. No urine samples were obtained from animals which died prior to their scheduled necropsy. The urinalysis consisted of the determination of urine specific gravity (refractometer), a qualitative assessment of color and appearance, a microscopic examination of the urinary sediment and a semi-quantitative determination of (Mulistix, Elkhart, Indiana): pH, bilirubin, glucose, proteins, ketones, occult blood and urobilinogen. The urine sediments from a single pooled sample/sex/dose group were microscopically evaluated.
- Time schedule for collection of urine: 30 and 90 days
- Metabolism cages used for collection of urine: No
- Animals fasted: No
NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
Anatomic Pathology
All rats submitted alive for necropsy were anesthetized by the inhalation of methoxyflurane vapors, blood/serum samples were obtained from the orbital sinus, their tracheas were exposed and clamped, and the animals were euthanized by decapitation.
Fasted terminal body weights were recorded. A complete necropsy was conducted on all animals by a veterinary pathologist (Diplomate, American College of Veterinary Pathologists) assisted by a team of trained individuals. The necropsy consisted of an examination of the external tissues and all orifices. The head was removed, the cranial cavity opened and the brain, pituitary and adjacent cervical tissues were examined. The eyes were examined in situ by application of a moistened microscope slide to each cornea. The nasal cavity was flushed via the nasopharyngeal duct and the lungs were distended to an approximately normal inspiratory volume with neutral, phosphate buffered 10% formalin using a hand-held syringe and blunt needle. The skin was reflected from the carcass, the thoracic and abdominal cavities were opened and the viscera examined in situ. All visceral tissues were dissected from the carcass, re-examined and an incision was made in selected tissues. Weights of adrenal glands, brain, heart, kidneys, liver, and testes or ovaries were recorded and the ratios of organ weights to terminal body weights were subsequently calculated for all animals. Samples of skin were obtained from: 1) the clipped test material application site, 2) an unc1ipped site adjacent and caudal to the application site (control tissue for assessment of possible mechanical irritation of skin by clipping), and 3) a site on the ventral side of the animal
distant from the application site (associated with mammary gland, not used for comparative purposes). For the 13-week study, representative samples of tissues were collected from each animal and preserved in neutral, phosphate-buffered 10% formalin with the exception of the testes which were fixed by infusion with 1.5% glutaraldehyde/4% formaldehyde solution followed by immersion in the same solution.
Only skin (treated and adjacent site) and organs with appropriate gross lesions were collected and preserved in formalin from rats from the range finding study. Similar necropsy procedures were followed for animals that died during the course of the study, except that body weights, organ weights and blood samples were not obtained. Only sections of the skin, from both the dermal test site and the adjacent untreated site, and appropriate gross lesions (stomach) were examined from the range finding study. For the 13-week study, all preserved tissues with the exception of auditory sebaceous glands and bone joint were examined for all control and high-dose group rats.

The following tissues from intermediate and low dose group animals were examined: lungs, liver, kidneys, skin at application site, skin adjacent to application site, and any tissues having grossly observable lesions. A complete set of tissues was also examined from all animals that died prior to the end of dosing.

For all organs except testes, paraffin embedded tissues were sectioned approximately 6 µm thick and stained with hematoxylin and eosin. A cross section through the approximate center of each testis was dehydrated through a series of graded ethanols and infiltrated with glycol methacrylate resin. The testes were sectioned at approximately 3 µm, and separate sections were stained with modified periodic acid-Schiff-hematoxylin or hematoxylin and eosin from each testis. The sections were examined for overt pathologic lesions as well as the presence of all stages of the spermatogenic cycle, following the methods described by Russell et at. (1990). The slides were examined by a veterinary pathologist (Diplomate, American College of Veterinary Pathologists) using a light microscope.

Histopathologic findings were subjectively graded to reflect the severity of specific lesions to evaluate: 1) the contribution of a specific lesion to the health status of an animal; 2) exacerbation of common naturally occurring lesions as a result of the test material; and 3) dose-response relationships for treatment-related effects. Very slight and slight grades were used for conditions that were present in excess of the normal textbook appearance of an organ/tissue, but were of minimal severity and involved less than 25% of the parenchyma. This degree of change would not be expected to significantly affect the function of the specific organ/tissue nor have a significant effect on the overall health of the animal. A moderate grade was used for conditions that are of sufficient severity and/or extent (up to 50% of the parenchyma) that the function of the organ/tissue may be adversely affected, but not to the point of organ failure. The health status of the animal may or may not have been affected, depending on the organ/tissue involved, but generally lesions graded as moderate would not have been life threatening.

The effects at the dermal site of treatment were diagnosed and graded.

Statistics:

All parameters examined statistically were first tested for equality of variance using Bartlett's test. If the results from Bartlett's test were significant, then the data for the parameter were subjected to a transformation to obtain equality of the variances. The transformations that were examined were the common log, the inverse, and the square root, in that order. When Bartlett's test was satisfied, that form of the data was used. The data were then subjected to the appropriate parametric analysis as described below.
In-life body weight, hematologic parameters (excluding differential WBC), and clinical chemistry parameters were evaluated using a three-way repeated measures (RM) analysis of variance (ANOVA) for time (the repeated factor), sex, and dose (Winer, 1971). In the three-way RM-ANOVA, differences between the groups were detected primarily by the time-dose interaction.
One-Way ANOVA:
Bartlett's test (Winer, 1971) alpha = 0.01
ANOVA (Winer, 1971) Dose Factor alpha = 0.05
Dunnett's Test (Winer, 1971) alpha = 0.05 (two-sided)
Two-Way ANOVA:
Bartlett's test (Winer, 1971) alpha = 0.01
First ANOVA (Winer, 1971):
Sex-dose interaction alpha = 0.05
Dose Factor alpha = 0.05
Dunnett's test alpha = 0.05 (two-sided)
Second ANOVA (Winer, 1971):
Dose Factor alpha = 0.05
Dunnett's test alpha = 0.05 (two-sided)
Three-Way Repeated Measures ANOVA:
Bartlett's test (Winer, 1971) alpha = 0.01
First ANOVA (Winer, 1971):
Time-sex-dose interaction alpha = 0.02
Time-dose interaction alpha = 0.05
Contrast Time-dose alpha = 0.02
(Bonferroni corrected comparison-wise error; Miller, 1966)
Second ANOVA (Winer, 1971):
Time-dose interaction alpha = 0.05
Contrast Time-dose alpha = 0.02
(Bonferroni corrected comparison-wise error; Miller, 1966)

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Dermal irritation:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

effects observed, treatment-related

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

effects observed, treatment-related

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

effects observed, treatment-related

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not specified

Details on results:

Stability, homogeneity and concentration verification were analysed. The test material was found to be stable in the acetone vehicle for at least 63 days. The dose solutions for the 13-week study were found to be homogeneously mixed with an RSD of less than 2.4%. Dose checks indicated solutions were 98 - 107 mean% of the targeted concentrations. Based upon the analytical results and body weight data, time-weighted average doses for the 13-week study were 0, 1, 10 or 97 mg/kg/day for males and 0, 1, 10 or 94 mg/kg/day for females.
CLINICAL SIGNS AND MORTALITY
There were no apparent treatment-related observations noted in any group except at the dermal application site.
The dermal scoring data for male and female rats are summarized: generally, one to two more high-dose male rats were noted with more severe dermal scores or increased presence of scabs than females from the same dose throughout the study.
Treatment-related observations in high-dose animals consisted of very slight to well defined erythema, very slight to moderate edema and slight scaling to slight fissuring. Six males and one female administered 10 mg/kg/day were noted with slight scaling during the final week of the study. This was consistent with the slight scaling observed in 10 mg/kg/day rats in the range finding study. The slight scaling appeared as a yellowish discoloration on the skin, however upon closer examination consisted of small scales.
There were no treatment-related dermal observations noted in animals from the 1 mg/kg/day dose group. One control male had a small scab on a part of the dermal test site (indicated by scabs covering less than 25% of the test site) between test days 22 and 85 but appeared normal during the week of necropsy. The focal nature of the scab and its occurrence in only a single rat suggested this was secondary to a clipping injury.
BODY WEIGHT AND WEIGHT GAIN
Mean body weight and body weight gain data for male and female rats were summarized and recorded. The body weights and body weight gains of treated females were slightly less than controls over much of the 13-week dosing period. However, these differences were not statistically identified as different from their concurrent controls and were likely due to normal biological variability. Male body weights were similar between control and treated groups.
FOOD CONSUMPTION
Mean feed consumption data for male and female rats were calculated. There were no consistent differences in the amount of feed consumed by any treated groups when compared to their respective controls suggestive of a treatment-related effect.
OPHTHALMOSCOPIC EXAMINATION
There were no treatment-related observations noted in any group when compared to their respective controls. All observations were typical of this age and strain of rat.
HAEMATOLOGY
Hematology data for male and female rats were summarized and recorded. There were no biologically or statistically significant changes in any of the hematologic parameters for male and female rats. Morphologic parameters of erythrocytes, platelets, and differential white blood cell counts were also unaffected by treatment.
CLINICAL CHEMISTRY
Clinical chemistry data for male and female rats were recorded. There were no treatment-related changes in any parameter evaluated. The statistically identified decreased high-dose triglycerides was considered not to be of toxicologic significance due to a lack of a dose response. In addition, treatment-related changes are normally associated with increases in triglycerides rather than decreases. The statistically identified difference in low-dose phosphorus was considered to be not treatment related due to the variability in directionality of the change compared to controls (lower after one month, higher after 3 months), the lack of a dose response and absence of other relevant treatment-related changes in clinical or histopathological parameters.
URINALYSIS
Urinalysis data for male and female rats was recorded. Urine parameters were normal for males after approximately one month, although due to insufficient urine volumes, two separate collections were required at that time in order to assess both the urinalysis parameters and perform the microscopic examination. Specific gravity data that were available suggested that both control and treated male rats were concentrating their urine. There were no apparent differences between control and treated rats, The nipple-type water system was verified to be working. There was no histopathological correlation to suggest decreased urine production and no similar effect in females, thus this was of questionable biological or exposure-related significance. There were no treatment-related urinary microscopic changes observed in male and female rats after 13-weeks of dosing.
ORGAN WEIGHTS
Terminal body and organ weight data for male and female rats were recorded. There were statistically identified decreases in high-dose adrenal and increases in low-dose liver weights. However, due to a lack of a dose-response and/or the absence of associated histopathologic changes in these organs, these weight differences are not considered to be biologically significant. In addition, decreases in adrenal weights did not reflect stress, as this would normally be associated with increases in adrenal weight. There were no other differences in organ weights between control and treated groups of rats.
GROSS PATHOLOGY
The gross pathologic observations were recorded. The only effects noted at necropsy that were attributed to AGE treatment were at the site of dermal application of 100 mg/kg bw/day rats. The skin of all rats, except one female at this dose level were noted to be slightly thickened with scales present. Other sporadic observations were noted at necropsy, generally in only one rat per dose group, and without apparent association to dose level. These observations were considered to be typical of common, spontaneous conditions expected in Fischer 344 rats of this age and experimental history. All were considered to be of a type or severity as to have no adverse effect upon the rat.
HISTOPATHOLOGY: NON-NEOPLASTIC
Histopathologic observations were recorded. Treatment-related effects were confined to the skin of rats given dermal applications of 100 mg AGE /kg bw/day. The effects could be characterized as a protective response which involved thickening of the skin along with a minimal inflammatory reaction. The skin reaction was characterized by epidermal hyperplasia with hyperkeratosis and hyperplasia of the sebaceous glands. The effects involved the treated site uniformly and there was minimal difference between animals. Generally, the skin effects were graded as slight, except for hyperkeratosis which was considered moderate in about one-half the treated rats. A mild subacute to chronic inflammatory response was also noted in all rats. The skin response was considered equivalent between the sexes; the minor differences in grades were attributed to individual variability.
The epidermal hyperplasia, hyperkeratosis and sebaceous gland hyperplasia found after 13 weeks of treatment with 100 mg AGE /kg bw/day were qualitatively similar to those noted after 2 weeks of dosing. However, crusts were not present after 13 weeks, although they were noted after 2 weeks, and the effects were of equivocally less severity than at the earlier time point. This is also consistent with the clinical observations (reported elsewhere). This suggests that the skin adapted to AGE treatment over the time course of the study. The morphologic manifestations of this adaptation were a generalized epidermal hyperplasia and hyperkeratosis with sebaceous gland hyperplasia.
There were no other treatment related effects noted in other organs. A number of mild spontaneous changes were noted in rats from all dose groups, including control rats. The most frequent changes included foci of mineralization, particularly in the vasculature of various organs, and small aggregates of mononuclear inflammatory or lymphoid cells in several organs. Unilateral lesions of the trigeminal nerve or lacrimal gland were present in some rats that were attributed to blood samples taken at mid-study. Unilateral atrophy of the retina and/or degeneration of the optic tracts were found in a few rats and were likely of similar etiology.
The testes were fixed, processed and stained to allow for detailed examination and staging of the spermatogenic cycle for each testis. Very slight unilateral atrophy of seminiferous tubules was present in three control males. This consisted of less than five tubular profiles lacking spermatogenesis with predominantly Sertoli cells remaining on the periphery of the tubule. One rat given 100 mg/kg bw/day had one slightly smaller testis as noted both grossly and by testes weights. This was associated with atrophy of about one-fourth of the seminiferous tubules of this testis. Normal spermatogenesis with the presence of all stages of the spermatogenic cycle was present in the remaining seminiferous tubules of the affected testis as well in the contralateral testis. The testes of all other rats examined lacked any overt lesions and the presence of all stages of the spermatogenic cycle was confirmed. No effects attributed to treatment were found in the testes.
Two female rats, one each from the 1 and 100 mg/kg bw/day dose groups, died after sampling for clinical pathology after one month on study. There were no major gross or histopathologic lesions found for these rats other than decreased ingesta in the digestive tract at necropsy and generalized visceral congestion histopathologically. The cause of death is consistent with anesthetic overdose.

Effect levels

1

Dose descriptor:

NOEL

Remarks:

systemic toxicity

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

dermal irritation

2

Dose descriptor:

NOEL

Remarks:

local effects

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Four daily dermal doses of 1000 mg/kg bw/day in the dose range finding study exceeded the maximum-tolerated dose as defined by loss of integrity of the epidermal barrier. Thus, 100 mg/kg bw/day was the maximum dose selected for the main study.
There were no treatment-related changes in clinical or ophthalmologic observations, body weights, feed consumption or clinical pathology during the thirteen-week study. Treatment-related gross and histopathologic lesions were limited to skin at the dermal treatment site of high-dose rats. Dermal applications of 100 mg/kg/day for thirteen weeks reached the maximum-tolerated dose as defined by the EPA (EPA, 1988) with a definitive, uniform reaction at the dermal treatment site consisting of epidermal hyperplasia, hyperkeratosis, sebaceous gland hyperplasia and a mild inflammatory response. The no-observed-effect level (NOEL) of systemic toxicity was 100 mg/kg/day.

Executive summary:

The repeated dose study was conducted to evaluate the sub-chronic dermal toxicity potential of test substance in Fischer 344 rats following a 5 days per week dosing regimen for approximately 13 weeks.

A range finding study was conducted in which two rats/sex/dose level were dosed dermally with 0, 10, 100, or 1000 mg/kg bw/day test substance in acetone, 5 days/week for up to a total of 10 applications. In-life observations and dermal scoring indicated an ungroomed appearance in high-dose group rats; erythema, edema, scaling/fissuring and scabs in high and middle-dose group rats and slight scaling in low dose group rats. Four doses of 1000 mg/kg bw/day exceeded the maximum-tolerated dose as defined by loss of integrity of the epidermis. Grossly, the skin of high-dose rats appeared scaly, thickened and was ulcerated. Microscopically, the response consisted of epidermal hyperplasia with hyperkeratosis and parakeratosis along with hyperplasia of the sebaceous glands with ulceration, inflammation and edema. The epidermal response was similar at 100 mg/kg bw/day, however the epidermis remained intact. Treatment-related effects in low dose rats were limited to slight scaling at the dermal test site.

Based on the results of the range finding study, non-occluded dermal doses of 0, 1, 10, and 100 mg AGE/kg bw/day in acetone were administered to ten rats/sex/dose level 5 days/week for 13 weeks. Standard toxicologic parameters were evaluated. Treatment-related gross and histopathologic lesions were limited to the skin of high-dose rats. Applications of 100 mg/kg/day reached the maximum-tolerated dose defined by the USEPA (1988) with a definitive, uniform reaction at the dermal treatment site consisting of epidermal hyperplasia, hyperkeratosis, sebaceous gland hyperplasia and a mild inflammatory response. The response was similar after 2 or 13 weeks, although the response was equivocally of greater severity after 2 weeks. Crusts, underlain by intact hyperplastic epidermis, were present after 2 weeks but not after 13 weeks. The no-observed effect level for systemic toxicity was 100 mg/kg bw/day.