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Level of exposure
J Group 1, 1.5-2 hours . Group 2, 3-3.5 hours
Time after exposure (hours)
Fig. 1. Acetylcholinesterase levels in whole blood of participating farmers at selected
times after they had finished spraying pesticide.
farmers were asked not to handle pesticides for at least 3 days before blood
samples were taken.
Mean AChE activity (measured as change in absorbance per mm per mL of
whole blood) was 19.13 ± 0.394 (mean ± standard error) at the end of the season
compared with 23.34 ± 0.470 during the spraying season, a significant difference
of 22% for Group IVa and 15% for Group IVb. This result was opposite
to what we expected, i.e., lower AChE activity during the spraying season due
to the effects of organophosphate and carbamate pesticides on cholinesterase
enzymes.
The seasonal differences in AChE activity may be the result of excessive
contact with pesticides resulting in enzyme induction (Burgess and Roberts
1980). Roberts (1980) mentions the possibility that persistent exposure to
pesticides may cause "cumulative biological changes." Individual differences
in AChE activity are common (Loosli 1980). The farming population in the
Jordan Valley has been using pesticides for at least the past 20 years.
Dermal exposure
Before 2 24 48
exposure
Dermal exposure generally accounts for 90% of total exposure to pesticides by
farmers. Seven pads were placed on each subject to determine which areas of
the body were most exposed (Table 1). As expected, Group TI, which operated
spraying equipment twice as long as Group I, experienced a higher degree of
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