Half of all agrochemicals are used on the five main crops, cereals, corn/maize, rice, cotton and Soya.
The most common method of pest control is the use of chemical pesticides that either kill pests or inhibit their development. Chemical control of pests probably began with poisonous plant compounds. In the 18th and 19th centuries, farmers ground up certain plants that were toxic to insects or rodents--plants such as chrysanthemums or tobacco. The plant "soup" was then applied directly to either the crops or the pests. Chemists later discovered that they could extract the toxic compounds from these poisonous plants and apply the compounds as liquid sprays. Such chemicals as nicotine, petroleum, coal tar, creosote, turpentine, and pyrethrum (obtained from a type of chrysanthemum) were eventually extracted for use as sprays. Organic compounds such as these were eventually replaced by more effective inorganic chemicals, including arsenic, lime, sulfur, strychnine, and cyanide.
The hazards of chemical pesticide use are now widely recognized, although statistics are hard to gather. The World Health Organization estimates that pesticides every year and more than 200,000 die poison at least three million people. It is estimated that up to 25 million agricultural workers are poisoned every year.
• In Malaysia and Sri Lanka, 7 to 15 per cent of farmers experience poisoning at least once in their lives.
• In Thailand, a survey of 250 government hospitals and health centres revealed that some 5,500 people were admitted for pesticide poisoning in 1985 alone, of whom 384 died.
• In the Philippines, 50 per cent of rice farmers have suffered from sickness due to pesticide use.
• In Latin America, 10 to 30 per cent of agricultural workers show inhibition of the blood enzyme, cholinesterase, which is a sign of organophosphate poisoning.
• In Venezuela, 10,300 cases of poisoning with 576 deaths occurred between 1980 and 1990.