Pesticide residues in food — 2007: Toxicological ... - ipcs inchem

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hepatocellular enlargement. In the group at 3000 ppm, this affected all males and females and was
of minimal (two males and three females) or slight (eight males and seven females) severity. Diffuse
hepatocellular enlargement also affected all males at 1500 ppm (minimal severity, 9 out of 10; slight
severity, 1 out of 10) and four females at 1500 ppm (minimal severity, 4 out of 10), compared with
one male and no females in the control groups. There was no indication of a treatment-related association
for the other histopathological changes in liver or in other organs (Cox, 1987b). The slight
effects observed as liver weight increase and minimal diffuse hypertrophy were regarded as adaptive
responses to treatment.
The NOAEL in rats given diets containing difenoconazole for 3 months was 200 ppm equal to
13 mg/kg bw per day, on the basis of a reduction in body-weight gain, an increase in liver weight and
haematological effects at 750 ppm equal to 51 mg/kg bw per day and above.
Difenoconazole technical (purity, 91.8%) suspended in 1% carboxymethyl cellulose (CMC) in
0.1% Tween 80 was applied to the skin of 10 male and 10 female HanIbm:WIST (SPF) rats at doses
of 0, 10, 100 or 1000 mg/kg bw for 28 days. Applications were for 6 h per day, 5 days per week for the
first 3 weeks and every day thereafter. Analysis of test article dosing suspensions before testing (three
samples per dose) indicated that the suspensions were close to nominal concentrations, homogeneous
and stable. Mean concentrations of the dosing suspensions used during the test were found to be
109%, 116% and 111% of the nominal concentrations at 10, 100 and 1000 mg/kg bw, respectively.
Samples of suspensions taken during the test were also found to be homogeneous and stable for 7 h
at room temperature.
The state of health of the rats was checked twice per day and clinical signs were recorded daily.
Eye examinations were conducted on all rats on day −4 before dosing and on all surviving rats in the
control group and those at 1000 mg/kg bw on day 23. Body weights were measured daily for dosing
purposes and were recorded weekly. Food consumption was recorded weekly. Detailed clinical
examinations (in the home cage, in a standard arena, and during handling) were performed before
the dosing period and once per week thereafter. Neurological examinations were performed after the
detailed clinical examinations, and included tests for sensorimotor function (approach, touch, vision,
audition, pain, vestibular). Laboratory investigations were carried out on all rats at the end of the
treatment period. Rats were killed on study day 29 and were subjected to a detailed gross pathological
examination. Selected organs were collected, weighed, and examined microscopically.
There was no treatment-related mortality or clinical signs indicative of a treatment-related
effect. Also, there were no abnormal findings in the neurological examinations and no signs of irritation
at the skin application site. There were no effects on body weights or body-weight gains at any
dose. No significant differences or treatment-related trends were observed in any of the haematology
parameters, although one male at 1000 mg/kg bw had a high leukocyte count with associated neutrophilia,
lymphopenia, eosinopenia and high monocyte and large unstained-cell counts. Treatmentrelated
changes in blood chemistry parameters were slightly lower values for globulin with an associated
increase in the albumin to globulin ratio and minimally lower plasma bilirubin and calcium
concentrations in males at 1000 mg/kg bw. An elevated mean value for ALT activity among females
at 10 mg/kg bw was due to high individual values for two rats that, clearly, were not dose-related.
Mean absolute liver weights of groups of male and female rats at 1000 mg/kg bw were 12% and 9%
higher than their respective controls, and relative liver weights were similarly 16% and 11% higher.
All other organ weights were comparable among the control and treated rats. No treatment-related
observations were noted at autopsy. However, microscopic examination revealed treatment-related
changes in the skin application site, liver and thyroid gland (Table 4). The skin changes were statistically
significant minimal to slight increases in the number of epidermal cell rows, as well as in thickness
of the retained lamellar keratin layer (hyperkeratosis) in male and female rats at 1000 mg/kg bw.
There was an increased incidence of minimal centrilobular hepatocellular hypertrophy in males and
DIFENOCONAZOLE 201–272 JMPR 2007