Toxicological consequences of pesticidal use in the Republic of South Africa

Doctoral Thesis


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University of Cape Town

Chemicals used in agricultural activities, could possibly be the most potent group of compounds used on a regular basis by employees representing a significant fraction of the unskilled, economically active, labour market of a country. Certainly, such a statement will hold true for South Africa and probably for most Third World and developing states. All chemical compounds contain the inherent property of being toxic and/or hazardous. However, pesticides are chemicals intentionally used to kill. They are therefore not avoidable and in contrast to other chemicals are used only because of their ability to kill. As in most other countries in the world, poisoning in the Republic of South Africa is to be expected due to the use of pesticides. In the handling of pesticides, statistics show South Africa to be vulnerable to an appreciable number of deaths and poisoning cases. There could be a number of reasons for this phenomenon, two of them probably being ignorance and negligence on the part of officers in charge of handling pesticides, and perhaps the most important, the exploitation of unskilled labour in applying and handling pesticides. It is believed that the South African agricultural industry represents both the First and Third World and should thus be ideally suited for investigating: (1) acute intoxication due to chemicals used in the agricultural industry. It was found that the annual consumption of pesticides in the Republic of South Africa results in a dose of approximately 250 mg/m² which compares very favourably with consumption rates of developed countries. An analysis of the products registered indicates a total of 1 211 products containing 359 different active ingredients. The three chemical groups responsible for 73% of the poisoning cases (organophosphates 55%, carbamates 14%, organochlorines 4%) are with the exception of pyrethroids, also the chemicals most frequently formulated. Products containing these three chemical groups constitute only 41% of all formulated products, but are responsible for 73% of all intoxications. It is concluded that the poisoning rate by pesticides is appreciably higher than officially notified, and that the fatality rate could be two orders of magnitude higher than developed countries. A compendium - the first of its kind in South Africa for use by hospitals and clinical practitioners and containing trade names, chemical classification, active ingredients, toxicology, symptomatology and proposed treatment procedures for each product, is presented as an appendix. (2) chronic exposure to residues of agricultural products in the diet of South Africans is investigated. Food intake data was calculated from 24-hour dietary recall studies. Residues of only 4 compounds were present in 33 composite, ready-to-eat foods, consisting of 5 538 foodstuffs sampled over a period of one-year country wide, and representing 142 different food items categorised into 11 food groups. The residues found were well within acceptable levels and compare very favourably with those found in the diets of developed countries. It has to be concluded that possible chronic exposure due to agricultural chemical contaminants, to the white population at least, does not exist, and emphasises a sound regulatory policy towards the use of these chemicals in South Africa. (3) a hypothesis of this study that it is not possible that neither the inherent toxicities of pesticidal compounds, nor a paucity of knowledge about the toxicological, chemical and physical properties of these compounds could be mainly responsible for the numerous intoxications recorded annually. An epidemiological 400 case study (descriptive design), investigated the contribution by occupational, environmental, cultural and socio-economic variables to poisoning. The numerous effects by these variables are described and amongst many others, it is concluded that the recommendations of the World Health Organization to classify pesticides by hazard, is confusing to illiterate and semi-educated users and should not be recommended to developing countries.