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

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no-observed-effect level (NOEL) for inhibition of plasma cholinesterase activity could not be
identified. Statistically significant inhibitions of erythrocyte and brain acetylcholinesterase were seen
at 18 ppm, but inhibition was less than 20% (the cut-off for toxicological significance that is used by
the Joint Meeting) in all cases but one (males at 4 weeks), which was regarded as an outlier result.
The NOAEL for consistent adverse effects on erythrocyte acetylcholinesterase activity was
18 ppm (0.78 mg/kg bw per day), while for brain acetylcholinesterase activity it was the highest
dose tested, 54 ppm (2.35 mg/kg bw per day) (Hutchinson, et al., 1966).
Table 4. Effects on mean erythrocyte cholinesterase activity in rats fed diets
containing temephos
Dietary concentration
(ppm)
Corrected ΔpH/h per 0.04 ml packed erythrocytes (percentage
inhibition compared with value for concurrent control)
Treatment period
Recovery period
Week 4 Week 8 Week 13 Week +2
Males
0 0.471 0.411 0.486 0.389
6 0.465 0.360 0.482 0.370
18 0.358* 0.340* 0.400*
0.405
(24%) (17%) (18%)
54 0.248*
(44%)
0.220*
(46%)
0.220*
(55%)
0.260*
(33%)
Females
0 0.404 0.476 0.511 0.493
6 0.418 0.420 0.510 0.478
18 0.350* 0.402* 0.458 0.480
(13%) (16%)
54 0.290* 0.315* 0.395*
0.438
(28%) (34%) (23%)
From Hutchinson et al. (1966)
* p < 0.05 (differs significantly from control values)
Table 5. Effects on mean brain cholinesterase activity in rats fed diets containing
temephos
Dietary concentration
(ppm)
Corrected ΔpH/h per 2.0 ml homogenate
(percentage inhibition compared with value for concurrent control)
Treatment period
Recovery period
Week 4 Week 8 Week 13 Week +2
Males
0 1.239 1.336 1.229 1.191
6 1.222 1.290 1.205 1.150
18 1.092 1.190 1.078*
(12%)
1.048*
(12%)
54 1.242 1.105*
(17%)
1.023*
(18%)
1.015*
(12%)
TEMEPHOS X-X JMPR 2006