Organochlorine pesticides environmental persistence

Hamer, T., Shoeib, M., et al. (2004) Using passive air samplers to assess urban-mral trends for persistent organic pollutants. 1. Polychlorinated biphenyls and organochlorine pesticides. Environmental Science and Technology, 38(17) 4474 483. 

Moreau-Guigon, E., Motelay-Massei, A.,et al (2007) Vertical and temporal distrihution of persistent organic pollutants in Toronto. 1. Organochlorine pesticides. Environmental Science and Technology, 41(7) 2172-2177. 

Much of the effort on environmental chemicals that contaminate food has concentrated on a small range of chlorinated chemicals. In addition to the chlorinated PCDDs, PCDFs and PCBs already mentioned, other chlorinated compounds can be separated into two groups chlorinated aromatic compounds and chlorinated aliphatic compounds. Although there is a number of organochlorine pesticides that are persistent in the environment, these will not be considered here, as they comprise an extensive field of study in their own right. 

Hence OP pesticides are much less environmentally persistant than are the organochlorines. However their chemical reactivity frequently renders them more acutely toxic than the organochlorine pesticides. 

Jeong, Y.P., Choi, M.K., Yeo, H.G., Cheon, M.Y., 2001c. Seasonal variations in the concentration of persistent organochlorine pesticides in atmosphere. Korean Journal of Environmental Agriculture (in Korean) 20(2), 79-85. 

The use of pesticides in Kenya dates back to the colonial era. The major areas of application include agricultural pest control and the public health control of mosquitoes, snails, and tsetse flies. However, with the rapid development of resistance of pests to the chemicals, coupled with environmental persistence, most of the organochlorines have been banned for agricultural use and restricted in the case of public health vector control. Nevertheless, there are detectable residue levels of these compoimds in amounts that lead to concern for food chain magnification. These levels arise either fi om previous application or unscrupulous use through illegal means. 

Of the several classes of synthetic insecticides, the chlorinated hydrocarbon (CH) and organophosphate (OP) insecticides have the greatest psychiatric significance [Pesticides and Neurological Diseases 1982 Ecobichon 1996). The CH insecticides, also called organochlorine insecticides, include three chemical classes di-chlorodiphenyltrichloroethane (DDT), cyclodienes (aldrin, dieldrin, heptachlor, chlordane, endosulfan), and chlorinated benzene and cyclohexanes (lindane) (Ecobichon 1996). Their ban in the United States and Europe resulted from their high chemical stability and lipid solubility that allowed environmental persistence and magnification in the food chain (Ecobichon 1996 Kaloyanova and El Batawi 1991). 

The polychlorinated biphenyls (PCBs) are synthetic organic chemicals with main sources in the environment being the processes of combustion and incineration (WHO, 1993). The organochlorine pesticides (OCPs), although banned internationally, can still be found in many environmental samples. Both classes of compounds are very persistent, tend to accumulate in the food chain and have negative effect on the human health (Cousins et al., 1998 Wade et al., 2002). For that reason many efforts have been made... 

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