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Deltamethrin was detectable in the urine of subjects exposed in 1 day of
spraying for up to 12 h after the beginning of exposure; urinary fenvalerate
was still detectable more than 24 h after the beginning of exposure in subjects
spraying for I day. This suggests that deltamethrin is more rapidly metabolized
than fenvalerate in humans. However, urinary levels of both pyrethroids
were higher in the groups spraying for 3 days, even 2 days after cessation of
exposure.
The deltamethrin metabolite Br2A could be detected in the urine of the 12 spray
operators in groups Ia and lb by HPLC 3-12 h after exposure. Levels peaked
3-9 h after spraying, with concentrations in the range of 8-110 g/L, i.e., 150
times higher than the level of deltamethrin in urine. This indicates that urinary
Br2A is a better indicator for biological monitoring than urinary deltamethrin.
Among groups spraying deltamethrin for 3 days, deltamethrin and its metabolite
Br2A appeared in urine samples early on the 1st day of spraying and
persisted for up to 2 days after cessation of the 3-day exposure.
In the groups spraying for 3 days, measurement of changes in nerve excitability
showed that the supernormal period in the median nerve was prolonged
compared with that before spraying. This difference became more significant
2 days after cessation of exposure (Table 7). No corresponding change in
supernormal period was found in the control group at 3-day intervals. After
spraying, nearly half of the operators displayed a prolongation of the supernormal
period in the median nerve of more than 4 ms, whereas almost none
of the control group showed similar changes. However, there was no correlation
between the nerve excitability changes and urinary deltamethrin or Br2A
excretion, nor diagnosis of acute deltamethrin poisoning.
Discussion
Pyrethroids have been classified as pesticides of high insecticida' activity and
low toxicity to mammals. However, pyrethroids can produce symptoms,
mainly involving the central and peripheral nervous systems, in humans
exposed to heavy concentrations in their work. The clinical data on the 573
reported cases of acute pyrethroid poisoning in China, including 344 accidental
poisoning cases and 229 occupational cases, provided a scientific basis for
developing the diagnostic criteria of acute pyrethroid poisoning (He et al.
1989). Exposed subjects having abnormal facial sensations without any systemic
symptoms can only be diagnosed as suspicious cases of acute poisoning.
Those who have systemic symptoms (i.e., headache, dizziness, nausea,
fatigue, and anorexia) and signs (i.e., listlessness and muscular fasciculation)
in addition to the abnormal facial sensations, causing them to miss work for
more than I day, can be diagnosed as mild acute pyrethroid poisoning after
exclusion of other diseases. Subjects with severe acute poisoning have disturbance
of consciousness, convulsive attacks, or pulmonary edema. However,
so far there have been no specific diagnostic indicators available for acute
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