Organochlorine Residues in Kenya's Rift Valley Lakes

Publisher Website
Google Scholar
Abstract
Of the farms surveyed in the Nakuru [Kenya] catchment basin, 47% used DDT or dieldrin for control of cereal pests. The most commonly used acaricide (for cattle tick control) was toxaphene (camphechlor); 73% of the 90 cattle dips used 16,770 kg/yr. The 2nd most commonly used acaricide was Delnav or dioxathion at .apprx. 5430 kg/yr. The largest single source of pesticides was the town of Nakuru (mosquito, weed and rodent control, dog washes, stored grain protection and household pest control). DDE residue levels were low. Low, undetectable or trace DDE levels were found in algae and Tilapia from Lake Naivasha, algae and corixid larva from Lake Nakuru and vegetation from Lake Baringo. Higher DDE levels were found in bottom-feeding fish Labeo cylindricus from Lake Baringo (2.13 mg/l), an otter from Lake Nakuru (0.35 mg/l) and ferns from the shores of Lake Naivasha (0.11 mg/l). Of bird eggs sampled, lowest DDE levels were found in the Lake Naivasha cattle agrets (0.22 mg/l) and the highest in the Lake Nakuru African darter (5.75 mg/l). For bird muscle tissue analyzed, the sequence was the same, with Lake Naivasha''s red-knobbed coot showing no detectable levels and Lake Nakuru''s marabou storks containing 1.09 mg/l. Lake Elmenteita was possibly the most highly contaminated lake, based on vegetation and lower aquatic life. Of the 3 other basins, Lake Nakuru showed the highest DDE levels. Incidences of biological magnification were observed in the various lake food chains with Lake Naivasha ferns providing deviation from the norm. Data interpretation was based on behavior and ecology of species involved. Frogs and toads collected from Lake Baringo should logically be grouped as amphibians, but their respective habits and microhabitats obviated grouping them for residue considerations. Before characterizing Lake Elementeita by residues in great white pelicans that breed there, their food source (Lake Nakuru) was recognized. There is a need to establish a periodic monitoring progam for contaminants in African nations. Specific research incudes: elucidating the role of unique spectrum of light, volatilization, codistillation, runoff, metabolism and the food chain in the ecosystemic translocation of pesticides in these and other African lake basins; determining the pharmacodynamic relationships between residues in eggs, brains, muscle and blood in a few common and widely distributed birds, which can be used in a monitoring program; and characterizing the relationships between ecological and socioeconomic factors which will determine the fate of African wildlife.

This publication has 1 reference indexed in Scilit: