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The aim of this study was to investigate the types, levels and distribution of pesticide residues in Eastern Lake Tanganyika basin in Tanzania. Water, soil and sediments samples were collected from various sites in Kigoma region. Analyses of cleaned sample extracts were performed using gas chromatographyelectron capture detection (GC-ECD) and gas chromatography-mass spectrometry (GC-MS). Six pesticide residues and metabolites were detected, namely, p,p '-DDT, o,p'-DDT, p,p'-DDE, p,p'-DDD, diazinon and chlorpyrifos. DDT, DDD and DDE were the predominantly detected compounds in all of the samples. Diazinon and chlorpyrifos were detected in soil samples only. The highest concentrations of total DDT in sediments and soil ranged from 10.02 to 116 µg/kg dry weight (dw) and 7.5 to 564.2 µg/kg dw, respectively. Chlorpyrifos and diazinon had concentrations up to 36 and 184 µg/kg dw, respectively. The concentrations of DDT residues were greater in soil samples than in sediments. The highest concentrations of DDT residues were detected in soil samples. The ratios of (p,p'-DDE + p,p'-DDD)/p,p'-DDT indicated recent inputs in most samples. The study reveals that there were recent uses of DDT, diazinon and chlorpyrifos in the region. Continued use of DDT indicates risks and may result into serious environmental problems. The area therefore needs serious environmental monitoring.

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In this study, the levels and status of dichlorodiphenyltrichloroethane (DDT) residues in fish samples collected from Eastern Lake Tanganyika were investigated. The analytes were determined using gas chromatography equipped with an electron capture detector (GC-ECD) and by gas chromatography-mass spectrometry (GC-MS). The compounds p,p'-DDE (4,4'-DDE), p,p'-DDD (4,4'-DDD), o,p'-DDT (2,4'-DDT) and p,p'-DDT (4,4'-DDT) were detected in all the samples, with total DDT concentrations ranging from 23 ± 8.3 to 339 ± 27 µg kg-1 fresh weight and 1736 ± 1388 µg kg-1 to 25 552 ± 4241 µg kg-1 lipid weight. The highest concentrations of total DDT were detected in Lates stappersii species. The ratios of the metabolites (DDD + DDE) to the parent compound (p,p'-DDT) were low (< 1) in all the fish samples, indicating exposure to fresh DDT. The concentrations of the DDT residues exceeded the extraneous maximum residue limit of 1.0 µg kg-1 , indicating risks and concerns for public health and the environment because of the indication of fresh application of banned pesticides and bioaccumulation. There is need for continued monitoring of the residues in Lake Tanganyika environs and controlling the pesticides used in the area.

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