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

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weekly throughout the study. At the end of the scheduled period, five male and five females per
group were perfused in situ. Selected nervous system tissues were removed, processed and examined
m icroscopically.
There were no deaths; this is a remarkable difference between this study, in which cage-side
observation is an important feature, and an earlier single-dose study (Argus, 1987) in which there was
40% mortality and significant clinical signs of toxicity at 2000 mg/kg bw. Evidence of a toxic effect
at 2000 mg/kg bw per day on day 1, at the time of peak effect, was reflected in a number of adverse
clinical abnormalities, with females being more affected than males. The more common signs were
upward curvature of the spine, tip-toe gait and decreased activity. All treatment-related clinical signs
seen on day 1 showed complete recovery by day 5 (males) and day 7 (females). In addition on day 1,
body weights at 2000 mg/kg bw per day were lower than those of males and females in the control
group (approximately 7%). Body weight remained lower for males throughout the study (4% by day
15) with food consumption lower for males in week 1. At 200 mg/kg bw per day, body weights were
statistically significantly lower (2%) than those of the controls on day 1 for both sexes.
On day 1, forelimb grip strength was lower than that of controls for males at 200 and 2000
mg/kg bw per day. Forelimb grip strength was statistically significantly higher than that of controls
on day 15 for females at 2000 mg/kg bw. The difference was seen only in females at one time-point;
in the absence of any other findings at this time-point, this small difference from control values was
considered to be incidental to treatment. There were no other differences from control values for
forelimb grip strength. At the 200 mg/kg bw, the lower forelimb grip strength observed on day 1 in
males was not associated with perturbations in any of the other functional assessments or microscopic
pathology. There were no treatment-related effects on hindlimb grip strength, landing-foot
splay measurements, or time to tail-flick at any dose.
At 2000 mg/kg bw, motor activity was lower than that for controls for females on day 1, with
evidence of some recovery on day 8 and complete recovery by day 15. This lower motor activity in females
was not associated with perturbations in any of the other functional assessments or microscopic
pathology, but may have reflected the adverse general clinical observations that had not recovered
until day 7. On day 1, at the time of anticipated maximum effect, males at 200 or 2000 mg/kg bw had
slightly higher activities than did males in the control group. The differences were small, the response
was not proportional to dose and was in the opposite direction from females and inconsistent with the
general clinical condition of the rats (e.g. decreased activity). Therefore, these small differences from
control values were considered to be incidental to treatment. There were no treatment-related effects
on body weight, food consumption, FOB or motor activity in rats at 25 mg/kg bw.
There were no effects on brain weight, nor any treatment-related microscopic findings in the
tissues of the nervous system after single doses of difenoconazole of up to 2000 mg/kg bw.
The NOAEL for neurotoxicity in rats treated with difenoconazole was 25 mg/kg bw on the basis
of reduced forelimb grip strength in males at 200 mg/kg bw. The Meeting considered that this effect
was not necessarily an expression of neurotoxicity, although it was an adverse effect of treatment,
because it was not observed in females as well as males, even at a dose that was 10 times higher,
and in males it was not supported by any of the multiple other possible end-points for neurotoxicity
examined (Pinto, 2006a).
In a multiple-dose study of neurotoxicity, groups of 12 male and 12 female Alpk:AP f
SD
(Wistar-derived) rats were given diets containing difenconazole (purity, 94.3 %) at a concentration of
of 0, 40, 250 or 1500 ppm, equal to 0, 2.8, 17.3 and 107.0 mg/kg bw per day in males and 0, 3.2, 19.5
and 120.2 mg/kg bw per day in females, for at least 90 days.
Food and water consumption and body weights were measured once each week throughout the
study. A check of the general state of health of the rats was made before the study began and daily
throughout the study. Detailed observations (during which each rat was removed from its cage and
DIFENOCONAZOLE 201–272 JMPR 2007