| Summary: | Thesis (Masters Diploma (Technology)--Cape Technikon, Cape Town,1994 === Pesticides are generally used in south-Africa for the
control of various pests; from insects and fungi to weeds.
The agricultural industry is probably the biggest user of
pesticides and therefore workers in this part of the
labour force have the biggest risk of being exposed to the
hazards of these essential products.
During the 1988/89 deciduous fruit season the deciduous
fruit industry earned approximately R1000 million in
foreign exchange. It is therefore very important for this
industry to produce fruit of high quality in a very
competitive market. Of the total deciduous exports, apples
comprised approximately 62,5%. The EIgin-Grabouw area is
the biggest producer of apples.
This industry is clearly very dependant on pesticides to
protect its crops against pests. From time to time farm -
workers are exposed to pesticides, a study was therefore
performed to access the levels of exposure of farm workers.
Blood and urine samples were collected in a comprehensive
biological monitoring program in the Elgin area to determine,
uusing clinical tests, the level of exposure to pesticides.
It was decided later that the determination of
pesticide residues in blood would form part of this main
study. Other tests included serum and red cell cholinesterase.
Samples were collected during August (start of
spraying season), November (midseason) and February (end
of spraying season).
A multi-residue method was developed to extract organophosphate
and organochlorine pesticides in whole blood.
Although various methods exist, they allow only for the
extraction of either organophosphates or organochlorines
and not multi-residue extractions. This multi-residue
method is based on the liquid/liquid extraction of a
blood/Celite/ethanol mixture to extract the following
pesticides: Azinphos-methyl, Chlorpyrifos, Endosulfan,
Methidathion and Prothiophos.
The pesticide residue levels were determined on gas
chromatographs equipped with DB-5 and DB-2I0 capillary
columns and flame photometric-, electron capture- and
nitrogen/phosphorous detectors. The results were confirmed
on a gas chromatograph with mass-selective detector in
selective ion mode.
Of the 402 blood samples analysed, 23 samples showed
positive for organophoshates and 29 for organochlorines,
and were sent for analysis on the mass spectrometer. Of
those samples only one could be positively identified. The
presence of the pesticide Endosulfan-B was confirmed. The
confirmation of the pesticides was complicated by interfering
substances that leached from the rubber stoppers of
the collection vessels into the blood.
Although the study showed that for practical purposes no
pesticides were present, other important information was
obtained about the handling and analyses of blood samples
for pesticides.
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