Contamination of cowpea and by-products by organophosphorous pesticide residues in Ngaoundere markets: Dietary risk estimation and degradation study

The study was carried out to monitor some organophosphorous (OP) pesticide residues in stored cowpea in Ngaoundere’s markets and two by-products (koki and fritter), to assess the dietary risk exposure through quotient risk (RQ) and to degrade some pesticides using kanwa (rock salt) solution. The levels of nine OP pesticides were determined by gas chromatography equipped with nitrogen photometric detector (GC-NPD) and GC-MS for confirmation. Six OP pesticides (dichlorvos, methyl-parathion, malathion, profenofos, diazinon and chlorpyrifos) were found in concentrations ranging from 0.02 to 5.4 mg/kg in peripheral zone while only five OP pesticides (dichlorvos, methyl-parathion, malathion, profenofos and chlorpyrifos) were found in the urban area (0.02 to 4.62 mg/kg). High amounts of these compounds were found in koki and fritter. Malathion, methyl-parathion and dichlorvos were the most frequent (27 to 89%) and some levels exceeded the maximum residue limits (MRLs) or the acceptable daily intake (ADI) per FAO; high values of RQ were found between February and May for all foodstuffs showing high risk for consumer at this period; malathion, dichlorvos, and profenofos were denatured by kanwa solution at the rate of reduction varying from 65% (malathion) to 98% (dichlorvos) with the production of malaoxon while methyl-parathion was not.   Key words: Organophosphorous, pesticide residues, monitoring, cowpea, dietary-risk, degradation.