Pesticide residues in food — 2006: Toxicological ... - ipcs inchem

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No clinical signs or increased mortalities were detected at any dose; the appearance and behaviour
of the dams was unaffected by treatment up to and including 50 mg/kg bw per day. Feed consumption
of the dams was distinctly decreased, especially during the first few days after initiation of treatment at
50 mg/kg bw, leading to body-weight losses during the first few days after initiation of treatment and
to a reduction of total body-weight gain, so that cumulative and corrected body-weight gains during
gestation were significantly decreased at 50 mg/kg bw per day (Table 32). Water consumption and
the amount of excreted faeces were decreased during the first few days after initiation of treatment at
50 mg/kg bw per day, while increased water consumption and urine excretion were observed towards
and during the second half of gestation at the highest dose (50 mg/kg bw per day). At gross necropsy no
test compound-related gross pathological findings were evident in any of the experimental groups.
At caesarean section, an increased incidence of late resorptions and one total resorption
were observed at 50 mg/kg bw per day, resulting in a slightly decreased number of live fetuses
and mean litter size at the highest dose. Also, mean fetal weight was decreased at the highest
dose. (Table 32). There was no effect on placental weight. An increased incidence of placental
border necrosis was apparent in all dose groups; however, values were within the range for
historical controls for the laboratory (0–17.65% of placentas with findings; 0–42.86% of litters
with findings).
The external examination of the fetuses revealed forelimb deviations in two fetuses from a
single litter at 50 mg/kg bw per day. These limb findings were considered to be treatment-related
since they were confirmed by skeletal evaluation (bone dysplasia) and similar findings were observed
at 50 mg/kg bw per day in other fetuses in several litters which were incompletely evaluated.
Visceral examination of fetuses revealed an apparent increase in the incidence and severity of
renal pelvis dilatation in groups at 10 mg/kg bw per day and greater. Since the combined incidence
of slight renal pelvis dilatation and renal pelvis dilatation did not display dose-dependency and in
the group at the highest dose was only marginally greater than (fetal incidence) or less than (litter
incidence) the control value for a study of a developmental toxicity with comparable study design (fetal
incidence, 23.2%; litter incidence, 69.2%), the finding was not considered to be related to treatment.
Table 32. Relevant findings in a study of developmental toxicity in rats given thiacloprid by
gavage
Finding
Dose (mg/kg bw per day)
0 2 10 50
Body weight (g):
Day 6 228.4 231.6 228.4 230.5
Day 9 236.0 238.8 234.2 212.8**
Day 14 255.6 256.9 252.8 232.2**
Day 20 314.7 314.1 308.8 279.6**
Bosy-weight gain (g), days 6–19 77.6 74.0 71.7 42.0**
Feed consumption (g/animal per day):
Days 6–11 17.7 17.6 16.9 6.4**
Days 11–16 19.1 19.1 19.0 16.4**
Days 16–20 21.6 21.4 20.9 19.6**
No. of dams with implantations (a) 28 31 32 30
No. of dams with viable fetuses (b) 28 31 32 29
No. of implantations per dam (b) 12.4 11.5 11.4 11.8
% Implantations per dam (b) 91.1 92.5 95.7 79.3**
% Postimplantation loss per dam (a) 0.9 0.9 0.5 2.8*
THIACLOPRID X-X JMPR 2006