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

191
(radiochemical purity, > 99%) as single oral doses at 2 mg/kg bw in corn oil. The concentrations of
radioactivity were determined in these tissues at 1, 3, 8, 14, 16, 18, 22 and 42 days after dosing (three
animals per time-point). The elimination half-lives in liver and kidney were 2.3 days and 2.0 days
respectively. Depletion of radiolabel from fat and skin was biphasic. Elimination half-lives for the
initial phase were 1.6–2.5 days, then 17–26 days for the second phase in fat, and 40 days in skin. An
analysis of pyrethroids present in the peri-renal and parovarian fat indicated that the administered
alpha-cypermethrin had undergone little or no isomerization (Logan, 1983).
In a study in humans, groups of two volunteers received capsules containing alpha-cypermethrin
as a single oral doses at 0.25, 0.50 or 0.75 mg (purity, 99.8%) in corn oil. Three weeks later, a repeatdose
trial was performed wherein the same subjects received the same dose as in the first trial, but
for five consecutive days. Urine (24 h) samples collected for 4 days after the single dose, and for
10 days after the first of the repeat doses, were analysed for cis-cyclopropanecarboxylic acid (free and
conjugated). The amount of metabolite excreted varied considerably between individuals, and was
related to dose. Excretion was rapid. When expressed as a percentage of the administered dose, the
amount of metabolite recovered in the urine was similar for the 24 h period after a single oral dose
(range, 35–57%; average, 43%) or any of the repeat doses (range, 30–75%; average 49%), and was
fairly consistent over the 5-day dosing period for each individual. Little (1–8% of the administered
dose per day) was excreted subsequent to 24 h after dosing. There was no evidence of bioaccumulation
in this study (van Sittert et al., 1985).
Figure 2. Metabolic pathways of alpha-cypermethrin, partly gained from analogy with
c ypermethrin
CYPERMETHRINS X-X JMPR 2006