Pesticide Residue Levels in Nzoia River Catchment Area

Abstract

A lot of pesticides are oftenused to control and manage pests in agricultural areas leading to theiraccumulation in various matricesand thus polluting the environment. Some of the applied pesticides are biodegradable while others convert to other forms which are even more lethal than the original compounds. TheNzoia River catchment zone beinga sugarcane growing region has serious mosquito infestations forcing public health officialsto use DDT formosquito control. A study of pesticide residue levels in the Nzoia catchment area has been done by stratified sampling of water, soils and sedimentsfrom eight (8) different sites along the river. The samples were collected in two seasons (during dry and rainy seasons) and were extracted by liquid-liquid extraction method. The extracted samples were then screened and determined qualitatively for pesticides using GC/MS. Quantitative analysis of organochlorines and pyrethroids weredone using GC/ECD.The results show a variation of pesticide residue levels with season. Some organochlorines (lindane and endosulfan sulphate) and pyrethroids were within the WHO’s MRL (Maximum Residue Limits) while op-DDE in Webuye [0.0794±0.0017 ppm] exceeded the WHO MRL value of 0.04ppm for op’DDE.The Nzoia River catchment zone is polluted from some of the pesticidesstudiedand unless their use is checked, a serious environmental degradation is likely to ensue. To reduce consumer health concerns, routine monitoring of pesticide residues in water, soil, and sediments is advised.Farmers must be educated on the usage of organic fertilisers and integrated pest management.