Organochlorines in Nigeria and Africa

Abstract

Many organochlorine compounds including DDT, lindane, HCB and PCBs which are persistent and bioaccumulative, have been used in Africa including Nigeria for almost half a century without environmental considerations. The main uses are in crop protection, animal and public health as well as industries. Nonetheless, there is gross misuse and abuse of these ecologically harmful chemicals including unorthodox pathways of human exposure. Despite the paucity of data on organochlorine use and contamination levels in the continent, the residue levels in Nigeria are used as a microcosm of the African environment contamination problems by these xenobiotics. Degradation studies on aldrin, DDT and lindane show that these organochlorines degrade much faster with short half-lives of a few weeks in Nigerian soils compared to several weeks and even years reported in cold temperate soils. This raises the problem of transposition data from developed countries to African countries and underscores the need for local research to obtain true persistence data derived from empirical models. Environmental contamination by organochlorines to different extents in the aquatic environment, land, wildlife, foodstuffs, human diets, human blood and breast milk in Nigeria was established from a literature review, and the data compared with those from other sub-regions in the African continent, Asia and the developed countries. The estimated maximum daily intake (EMDI) of aldrin + dieldrin in some Nigerian foodstuffs was greater than the FAO’s acceptable daily intake (ADI) which calls for caution and control action. Compared to more industrialized countries and with the exception of some hot-spots sites, the concentrations of organochlorines were low. Nonetheless, the gross contamination of human blood and mothers’ milk place children especially and the human population at risk from exposure to organochlorines. The foregoing situation underscores the fact that contamination of the environment and humans is a problem of both developed and developing countries. With increasing population, greater demand for food and industrialization, organochlorines use may increase. Priority attention should therefore be given in Africa to capacity building in organochlorine residue analysis and regulatory control of toxic chemicals including the tracking of organochlorines from cradle to grave.