Sources, distribution, and risk assessment of organochlorine pesticides in Nairobi City, Kenya. Journal of Environmental Sciences, 96, 178–185

Abstract

The distribution and sources of organochlorine pesticides (OCPs) in air and surface waters were monitored in Nairobi City using triolein-filled semipermeable membrane devices (SPMDs). The SPMDs were extracted by dialysis using n-hexane and cleaned adsorption chromatography on silica gel cartridges. Sample analysis was done by GC-ECD and confirmed by GC-MS. Separation of means was achieved by analysis of variance, followed by pair-wise comparison using t-test (p≤0.05). The total OCPs ranged between 0.018 ng m^(-3)-1.277 ng m^(-3) in the air and <LOD-1391.000 ng m^(-3) in surface waters. From the results, means of Industrial Area, Dandora and Kibera were not significantly different (P ≤ 0.05), but were higher (P ≤ 0.05) than those of City square and Ngong’ Forest. The results revealed non-significant (P ≤ 0.05) contribution of long-range transport to OCPs pollution in Nairobi City. This indicated possible presence of point sources of environmental OCPs in the city. The water-air fugacity ratios indicated volatilization and deposition played an important role in the spatial distribution of OCPs in Nairobi City. This indicated that contaminated surface waters of could be major sources of human exposure to OCPs, through volatilization. The incremental lifetime cancer risks (ILCR) determined from inhalation of atmospheric OCPs were 2.3745 x 〖10〗^(-13)-1.6845 x 〖10〗^(-11) (adult) and 5.5404 x 〖10〗^(-13)-3.9306 x 〖10〗^(-11) (child) in the order: Dandora>Kibera>Industrial Area>City Square>Ngong^' Forest. However, these were lower than the USEPA acceptable risks, (〖10〗^(-6)-〖10〗^(-4)). This study concluded that atmospheric OCPs did not pose significant cancer risks to the residence.