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

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ratios in males at all doses and in females of the group at 10 000 ppm. In the absence of morphological
changes, many of these differences might be considered to be adaptive in nature, but the marked
increases in total cholesterol concentration and in γ-glutamyl transferase activity at 10 000 ppm are
nevertheless adverse. Since these increases also occur in the absence of morphological changes, it
was not clear whether the other blood chemistry changes observed at 10 000 ppm were toxicologically
relevant. All other statistically significant differences were considered to be incidental and within
the normal range of biological variation.
No toxicologically significant effects were observed in the quantitative and qualitative analyses
of urine. There was a slight to moderate increase in ketone body formation for males at 250 ppm,
1500 ppm and 10 000 ppm, as well as females at 10 000 ppm. The increases in the rats at 10 000 ppm
were attributed to reduced food consumption and/or prolonged fasting. The few other statistically
significant differences were considered to be incidental and within the range of normal biological
variation. Almost all organ weights were significantly reduced in the group of rats at 10 000 ppm,
but because of the reduced carcass weights, the organ-to-body weight ratios were actually increased
in this group. There were statistically significant reductions in liver weight of males at 250 ppm and
10 000 ppm, while there was a statistically significant increase in liver weight in the group at 1500
ppm. This lack of a dose–response relationship paralleled the fluctuations in male body weight described
earlier. In female rats, there were no significant changes in absolute liver weight at any dose;
however, liver weights relative to body weights were significantly increased in males and females
in the groups at 1500 and 10 000 ppm. In the group at 1500 ppm, kidney weights relative to body
weights increased in males, while absolute kidney weights were decreased in females. Decreased
spleen weights were seen in males of the group at 250 ppm, but not in the group at 1500 ppm or in
females at either of these doses. No treatment-related observations were recorded at autopsy or upon
microscopic examination. Thus, on the basis of organ-weight changes, the liver appeared to be the
target organ for toxicity (Suter, 1986a).
The NOAEL in rats given diets containing difenoconazole for 33 days was 250 ppm, equal to
27 mg/kg bw per day, on the basis of liver-weight changes at 1500 ppm, equal to 156 mg/kg bw per day.
Changes in liver weight observed at 250 ppm were considered to be adaptive responses. The m aximum
tolerated dose (MTD) was clearly exceeded at 10 000 ppm, equal to 841 mg/kg bw per day.
Groups of 10 male and 10 female Wistar rats (outbred KFM-Han, SPF) were given diets containing
difenoconazole technical (purity, 94.5%) at a concentration of of 0, 40, 250 or 1500 ppm,
equal to 0, 3.3, 20 and 121 mg/kg bw per day in males and 0, 3.5, 21 and 129 mg/kg bw per day in
females, for 13 weeks. An additional 10 males and 10 females were included in the control group
and the group at 1500 ppm for the 13 weeks and then continued on control diet for a 4-week recovery
period. The doses were selected on the basis of the results of a 28-day study (Suter, 1986a), in
which treatment-related effects were seen at 1500 ppm and the MTD was exceeded at 10 000 ppm.
The stability of difenoconazole in the diet had been verified for the 33-day study (see above) that
was conducted within 2 months of this study. The homogeneity of the dietary mixtures was verified
before the start of the study. Analyses for correct concentration also were performed before the start
of the study and were satisfactory.
Food consumption and body weight were determined once per week. The state of health was
checked twice per day. Hearing tests and eye examinations were carried out before the start and at the end
of dosing and recovery periods. Blood samples were taken from all rats for haematology and blood chemistry
examination at the end of the dosing period. Urine was analysed at the end of the exposure period.
All rats were subjected to complete gross examinations, and weights of selected organs were d etermined.
Microscopic examinations were conducted routinely on selected tissues and all gross lesions.
There were no mortalities in the study and difenoconazole did not induce clinical signs of
toxicity at any dose. Body weights of the group of rats at 1500 ppm were significantly and/or clearly
DIFENOCONAZOLE 201–272 JMPR 2007