Assessment of Risk and Processing Effects on Banned Pesticide Residue Levels in Nigerian Staple Foods

The use of pesticides has overwhelming advantage to food security but not so much to the environmentalists and toxicologists. Governments of nations or regions have over the years restricted or banned the use of certain pesticides. This work examined the incidence, dietary exposure and risk characterization of some Nigerian-banned organochlorine and organophosphate pesticides in rice, cassava, maize and beans marketed in Kogi state, Nigeria. The extraction of pesticide residues was performed using the Quick, Effective, Cheap, Easy, Rugged and Safe (QuEChERS) technique, and gas chromatography tandem mass spectrometry was used for quantification of the pesticide residues in the samples. The residues detected in order of decreasing incidence were methoxychlor, α-chlordane, γ-chlordane, endosulfan II, dieldrin, aldrin, p,p'-DDE, Δ-BHC (hexachlorobenzene), endrin aldehyde, p,p'-DDD, lindane, p,p'-DDT, and endosulfan sulfate. No assayed organophosphate residue was detected. Methoxychlor and α-chlordane had the highest incidences of 46.88% and 31.25% respectively, while lindane, p,p'-DDT and endosulfan sulfate had the lowest incidence (3.13% in each case). The processing steps applied including cold water washing, warm water washing, soaking and fermentation had various effects on the level of residues ranging from -149% to 100% reduction in level of pesticide, and are recommended. Risk characterization by percentage tolerable daily intake estimation showed that aldrin and dieldrin were detected at concentrations that far exceeds the safety threshold, the hazard index also revealed that Δ-BHC (hexachlorobenzene), lindane, aldrin, dieldrin and methoxychlor were present in staples at levels with potentials to induce chronic toxicity. None detection, low incidence, low concentrations and low hazard index and risk posed by most pesticides in this study is indicative that the ban on these pesticides has been impactful in reducing their use within Nigeria and consequently in averting health challenges associated with their use. Finding them at any level should alert the regulatory agencies to further strategize towards risk mitigation and elimination.