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Die bepaling van sekere plaagdoderreste in die bloed van plaaswerkers op appelplase in die Elgin-distrik
Morren, Carel-Jan Hendrikus
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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.