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

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Table 6. Transmembrane migration of boscalid in rat and human epidermis in vitro
Time (h)
Mean cumulative absorption of [ 14 C]boscalid (μg/cm 2 skin)
Administered dose (μg/cm 2 )
10 100 1000
Rat Human Rat Human Rat Human
0.5 0.264 0.002 0.302 0.009 NA NA
1 0.462 0.014 0.657 0.032 7.703 1.404
2 0.691 0.029 1.178 0.108 11.47 1.929
4 0.977 0.046 1.667 0.157 13.03 2.026
6 1.143 0.061 1.890 0.204 15.63 2.143
10 1.366 0.103 2.593 0.304 20.64 4.295
24 1.906 0.264 3.650 1.320 27.87 5.283
Lag time (h) 0.055 0.185 0.110 0.227 0.219 0.115
Mean rate of penetration
(μg/cm 2 per h) 0.302 0.015 0.685 0.050 3.813 0.498
Permeability coefficient
(× 10 -5 cm/h) 51.6 2.572 7.188 0.53 6.571 0.858
From Thornley & Bryson (2001)
NA, not applicable.
7.2 and 6.6 for rat epidermal membranes and 2.6, 0.53 and 0.86 for human epidermal membranes
exposed at 10, 100 and 1000 μg/cm 2 , respectively (Table 6).
Transfer of radioactivity across rat epidermal membranes was rapid during the early sampling
times of the experiment, with a lag time at all doses of less than 14 min. Thereafter, the amount of
radioactivity transferred decreased with time, the transfer rate between 10 h and 24 h being less than
14% of the initial rate. At the end of the study, the radioactivity transferred was 33%, 4% and 3%
of the 10, 100 and 1000 μg/cm 2 doses, respectively. At the lowest, intermediate and h ighest doses,
respectively, 31%, 73% and 96% of the applied radioactivity was recovered in the skin w ashings and
was therefore unabsorbed. For a 10- and a 100-times increase in the concentration of the f ormulation
applied to rat membranes, a corresponding 2.18- and 12.63-times increase in the initial rate of
a bsorption was apparent.
Radioactivity was absorbed through human epidermal membranes within 14 min of a pplication,
regardless of the concentration of formulation. As with the rat, there was evidence to suggest an
i nitial high rate of absorption within the first 4 h for some human epidermal membranes. The rate of
absorption increased 3.3-fold and 33.2-fold for a 10- and 100-times increase in the concentration of
boscalid.
The time-courses of transfer across rat and human epidermal membranes at each concentration
of boscalid are shown in Figures 2–4.
BOSCALID X-X JMPR 2006