Severity and frequency of intoxication depend upon the mode of pesticide application and its handling. Industrial hazards in the manufacture, packing and transport, as well as public health hazards, result from the chemical nature of the pesticide and its method of application. Industrial hazards also involve contact with other toxic chemicals that contribute to the ultimate synthesis of the end product. Among factory workers, systemic uptake is likely to occur by inhalation and through the skin, or by mouth. In the countryside the farm workers are often working in the fields after the use of pesticides and their families living near fields receive a dose of chemicals sprayed by air. The possible long term effects of pesticide poisoning are carcinogenic, teratogenic, mutagenic and environmental.
Recently there have been an alarming number of ecological disasters caused by pesticides. One, for example, was a major fish kill in Thailand involving many millions of fish due to contamination of rivers by the herbicide paraquat. This kill wiped out the major source of protein for many of Thailand's people. Another disaster in the central Indian city of Bhopal in December 1984 may have been the deadliest industrial accident world-wide. An American built insecticide plant leaked poisonous gas that within hours killed or fatally injured at least 1,200 local residents, and blinded, sterilized or otherwise sickened thousands of others. Many victims were people living adjacent to the plant.
More than half of the patients admitted to UK hospitals between 1970 and 1982 for poisonings were children under 5 years of age and the bulk of them had consumed garden and home pesticides left around the house. Other than by misadventure, most nonsmokers in developed countries probably receive their highest exposure to harmful chemicals from pesticide residues in the food they eat.
Exposure to pesticides, fertilizers and heavy metals poses health risks through soil, water, air and food contamination. Global pesticide use has resulted in 3.5-5 million acute pesticide poisonings per year (WHO 1990). Recent epidemiological studies have suggested a link between organochlorine pesticides and cancer, including lymphoma and breast cancer (Zahm and Devesa 1995).