Impact of - IDL-BNC @ IDRC - International Development Research ...

Cholinesterase levels in red blood cells were determined before and after
monocrotophos exposure using the Michel method. Twenty-four hour urine
was collected before spraying, during the 3 days of application, and 1 day after
completion of the spraying. The urinary metabolite, dimethyiphosphate, was
determined by gasliquid chromatography.
For all three studies, operational details (crop height, row spacing, area
covered, and rate of application) and meteorological data (wind speed, wind
direction, air temperature, and relative humidity) were recorded as recommended
by the WHO protocol.
Results and discussion
Postexposure levels of p-nitrophenol in urine were not significantly different
from baseline levels. Two factors explain this: over the previous 9 years,
subjects have been exposed to a number of different pesticides, thus the
relatively short exposure to methyl parathion during this study may not have
been sufficient to have an additional effect; the method used to measure
p-nitrophenol may not have been sensitive enough to detect changes.
In keeping with the WHO protocol, contamination of the cotton overalls and
potential dermal contamination represented by the gauze patches were
assessed. Mixing and loading activities, which were carried out three to five
times during the 1-h study periods, accounted for 55% of the contamination
of clothing; that of the "all activities" group represented 28% of total contamination.
Spraying at any of the three stages did not account for a large
proportion of the contamination of clothing. The risks were equal for the RI
and R2 stages (spraying at the vegetative and maximum tillering stages,
respectively) and accounted for 8% each. The R3 group (spraying at the
booting stage) represented only 1% of all contamination of clothing.
Potential dermal contamination, i.e., penetration of clothing, was assessed by
measuring the amount of pesticide in the gauze patches. Of total contamination,
47% was found in the "all activities" groups. Farmers in these groups
performed all activities in I h. They were exposed for a longer period and at
greater pesticide concentrations than those undertaking specific activities.
Mixing and loading accounted for 12.0%; RI for 16.0%; R2 for 21.0%; R3 for
3.0%; and cleaning and disposal 1.0%. There was no dermal contamination
during the reentry periods on days I and 7.
The distribution of methyl parathion contamination over different regions of
the body was assessed by comparing the various cloth sections and patches
for the "all activities" group and the R2 group (Fig. 2). Hands had the highest
potential for dermal contamination and penetration. The high degree of
contamination of the left hand of those in the "all activities" group was due
to the farmers' practice of applying the pesticide with their right hand, while
the left held the cover of the tank sprayers used for measuring the pesticide.
66