Assessment of levels of pesticides residues in raw and processed maize grains and flour from selected areas in Dar es salaam and Ruvuma

This dissertation reports the types and concentrations of pesticides residues in maize grains and flour and the effects of processing methods on the levels of pesticides residues in the maize products samples collected from selected areas in Dar es Salaam and Ruvuma. Sampling and sample treatments were done as appropriate. Analysis of cleaned up extracts was done using GC-MS. Twelve pesticides were detected in maize grains and their highest concentrations were as follows: p,p’-DDT 113 µg/kg, o,p’-DDT 3.4 µg/kg, p,p’-DDD 120.2 µg/kg, o,p’-DDD 2.5 µg/kg, α-endosulfan 522.1 µg/kg, β-endosulfan 154 µg/kg, aldrin 9 µg/kg and dieldrin 430 µg/kg, chlorpyrifos 3810.3 µg/kg, pirimiphos methyl 11200 µg/kg, fenitrothion 132.1 µg/kg and cypermethrin 14 µg/kg. In maize flour eight pesticides were detected in both polished and unpolished flour and their highest concentrations were as follows: α-endosulfan 270 µg/kg, β-endosulfan 63.3 µg/kg, aldrin 1 µg/kg and dieldrin 1.2 µg/kg, chlorpyrifos 1402 µg/kg, pirimiphos methyl 2220 µg/kg, fenitrothion 65 µg/kg and cypermethrin 2 µg/kg. The detection frequencies ranged from 2.63% to 57.89%. Only dieldrin (2 µg/kg) was detected in cooked samples. The concentrations of p,p’-DDD, aldrin, dieldrin, chlorpyrifos, and pirimiphos methyl in some samples in maize grains exceeded the MRLs. In maize flour, the concentrations of chlorpyrifos in some samples exceeded the MRL. The findings indicate risks and concerns for public health. There were significant differences in mean concentrations for α-endosulfan, β-endosulfan and cypermethrin between maize grains and maize flour whereas aldrin, dieldrin, chlorpyrifos and pirimiphos methyl did not show significant differences. Processing methods were found to cause transformation or reduction of the pesticides. There is need to monitor pesticides usage in Tanzania