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

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range appeared to exist for the group of sprayers between the before and after exposure measurements.
There was no evidence that these changes were compound-related; they probably reflected seasonal
variations. The general conclusion is that under the conditions of this study the application of Ripcord
caused no detectable adverse health effects (Annex 1, reference 33; Prinsen & Van Sittert, 1979).
Transient facial sensory symptoms after exposure to synthetic pyrethroids (e.g. cypermethrin,
permethrin, fenvalerate and fenpropathin) in some workers have been reported. Among 23 workers
exposed to synthetic pyrethroids, 19 had experienced one or more episodes of abnormal facial sensation
that developed between 30 min and 3 h after exposure and persisted for 30 min to 8 h. There were
no abnormal neurological signs and electrophysiological studies were normal in the arms and legs. It
was concluded that the symptoms are most likely to be due to transient lowering of the threshold of
sensory nerve fibres or sensory nerve endings after exposure of the facial skin to pyrethroids, similar
to the phenomena that have been described in Wouters & van den Bercken (1978), after exposure of
animal nerves to pyrethroids (Annex 1, reference 37; Le Quesne et al., 1981).
Skin sensations experienced by those handling cypermethrin or other pyrethroids are believed
to arise by repetitive firing of sensory nerve terminals in the skin. It is said to be a strictly local effect,
which may occur as soon as the concentration of pyrethroid on or in the skin reaches a certain level and
is not considered as a sign of general intoxication (provided the pyrethroid does not reach the blood
in any significant concentration). A possibility exists, however, that repeated occurrence of intense
repetitive firing can perhaps eventually lead to dysfunction of sensory nerve terminals and sense organs
and finally to degeneration of sensory nerve fibres (Annex 1, reference 33; van den Bercken, 1980).
A monitoring study was undertaken to determine the dermal exposure of two pilots and two
mixer-loaders, and the systemic absorption by five mixer-loaders during operations for the aerial
application to cotton of a ULV formulation of cypermethrin in oil. Cypermethrin absorption was
measured in three mixer-loaders by assessing the concentrations of the cypermethrin metabolites
3-(2,2-dichloroethenyl)-2-2-dimethylcyclopropanecarboxylic acid (DCEA, cis and trans),
3-phenoxybenzoic acid (3PBA) and 4´-hydroxy-3-phenoxybenzoic acid (4OHPBA) on the day
of application and for 6 days thereafter. The formulation used (Cymbush 3E) contained 360 g/kg
cypermethrin which was diluted in fully refined soya bean oil to a spray concentration of 2.9% w/v
cypermethrin. Each replicate application used 15 l of Cymbush. All mixer-loaders wore protective
equipment. Dermal exposure to cypermethrin was 0.67 mg/8 h for pilots, and 2.4 mg/8 h for
mixer-loaders. For pilots, most exposure was to the hands, while exposure was more uniform for
mixer-loaders, principally involving the arms, trunk and hands, reflecting a high degree of protection
afforded by gloves. The metabolites 4OHPBA and 3PBA were detected in the urine of all three
subjects, and trans-DCEA (but not cis-DCEA) was detected in two subjects. The most persistent
urinary metabolite was 4OHPBA, which was not detected on day 4 in two subjects, and was just
detectable in the third subject on days 5 and 6. It was concluded that as the major metabolites in the
urine were 3PBA and 4OHPBA, metabolism and excretion in humans resembled that in rats more
closely than that in mice. Calculations of cypermethrin excreted indicated that systemic absorption
(46–78 μg of cypermethrin) represented a small proportion of actual dermal exposure (approximately
0.63–3.6 mg of cypermethrin) (Chester et al., 1987).
A review of 573 cases of acute pyrethroid poisoning reported in the Chinese medical literature
during 1983–1988 showed that 45 cases were involved cypermethrin. Of these, six were due to
occupational exposure and 39 were accidental. In most cases of occupational pyrethroid poisoning,
effects were reversible, so the prognosis was generally good. Details specific to the cypermethrin
cases were not provided. After occupational exposure, symptoms of burning or itching sensations
CYPERMETHRINS X-X JMPR 2006