Module 3: Toxicology - Section 8: Pesticides
TOX 8.1: Introduction and Classification
 

INTRODUCTION

Pesticides are chemicals which are used to control a wide variety of organisms which are a threat to health or compete with for food or other materials. Pesticides act through selective toxicity but organisms are similar at the cellular level and thus humans are easily affected. 1

Pesticides are widely used in South Africa with the expenditure having increased tremendously in the past ten years. South Africa is currently the main agrochemical market in sub-Saharan Africa. Sales of pesticide products totaled approximately R900 million in 1995. 2

In the United States of America and many other countries organophosphates in particular have replaced other pesticides because they are more effective than other agents are. As a result increasing numbers of workers are exposed to organophosphates. According to data assembled from the poison control centres, there are approximately 10 000 cases of organophosphate poisonings annually in the US. 3

CLASSIFICATION OF PESTICIDES:

Category of Pesticide Example Health Effect
Herbicides
Triazine Atrazine Anti-oestrogenic
Chloroacetanilides Alachlor Carcenogenic
Dinitrophenols Dinoseb Carcinogenic
Chlorophenoxy 2,4D and 2,4,5 T Anti-oestrogenic
Genotoxic
Quarternary Ammonium Compounds Paraquat
Diquat		 Acute lung fibrosis
Dematitis
Nosebleeds
Insecticides
Organophosphates Malathion
Parathion		 Inhibits cholinesterase
Carbamates Aldicarb Mutagenic
Teratogenic
Organochlorines DDT
Chlordane		 Neurotoxic and hepatotoxic
Pyrethrins and Pyrethroids Permethrin
Fenvalerate		 Sodium channel blockers producing neurotoxicity
Fumigants
  Methyl bromide Neurotoxicity
Genotoxic
  Chloropicrin Pulmonary oedema
Cardiac arrhythmias
Genotoxic
  Phosphine Neurotoxic
Inhibits cholinesterase
Pulmonary oedema
Fungicides
Chloroalkyl thio fungicides Captan Carcinogenic
Thiocarbamates Maneb CNS depressant
Benzimadoles Benomyl A teratogen in animals
Methylmercury Compounds   Neurotoxicity
Birth defects

REFERENCES:

  1. Goodman and Gilman or Katzung and Bardin PG. Van Eeden SF and Joubert JR. Intensive care management of acute organophosphate poisoning. S Afr Med J 1987 72:593-597.
  2. Environmental and Occupational Medicine. W N Rom. 3rd Edition. Chapter 83. Pages 1157 to 1171.
  3. London L, Myers J. Critical Issues for Agrichemical Safety in South Africa. American Journal of Industrial Medicine.1995. Vol 27. P 1-14.
  4. Steenland K, Jenkins B. Chronic Neurological Sequelae to Organophosphate Pesticide Poisoning. American Journal of Public Health. 1994. Vol 84. No 5. P731-738.
  5. L London. Biological monitoring of workers exposed to organophosphate pesticides: Guidelines for filed application.1995. Occupational Health Southern Africa. 1(4). 13-17.
  6. http://www.pesticideinfo.org/Index.html



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Postgraduate Diploma in Occupational Health (DOH) - Modules 3: Occupational Medicine & Toxicology (Basic) by Profs Mohamed Jeebhay and Rodney Ehrlich, Health Sciences UCT is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.5 South Africa License. Major contributors: Mohamed Jeebhay, Rodney Ehrlich, Jonny Myers, Leslie London, Sophie Kisting, Rajen Naidoo, Saloshni Naidoo. Source available from here. For any updates to the material, or more permissions beyond the scope of this license, please email healthoer@uct.ac.za or visit www.healthedu.uct.ac.za. Last updated Jan 2007.
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