Trace metal pollution study on cassava flour's roadside drying technique in Nigeria

Cassava flour, generally consumed in Africa as food, is a major source of carbohydrate. Its common drying technique in Nigeria is sun drying for cost optimization whereby the flour (in powder form) is spread by the roadside for moisture content reduction process. This research was carried out at five major traffic highways in Nigeria to study the level of trace element pollution introduced through this drying method, identifying the sources of the pollutants mainly as automobile exhaust emission (major) and street dust (minor). At each site, ten samples (from the four corners and the center) were collected, mixed, digested and analyzed using Graphite Furnace Atomic Absorption Spectroscopy (FAAS) technique to determine the concentration of ten elements (Fe, Cd, As, Pb, Ni, Co, Cu, Cr, Mn and Zn). Analysis of certified standard reference material IAEA-V-10 Hay (Powder) was carried out to ensure accuracy and precision of the technique. Except for zinc, all samples have comparatively high concentrations. Specifically, Fe, As, Pb, Cu and Cd have concentrations as high as 7.2, 5.70, 17.16, 4.57 and 0.39 g/70 kg respectively as against the maximum human uptake limits of 0.01, 0.014, 0.08, 0.11 and 0.03 g/70 kg respectively. The results show that even though, cassava flour is a rich source of the essential and beneficial minerals required for healthy living, it's drying technique exposes it to the excessive intake of some of these trace metals which could be hazardous to human health. Alternative drying techniques are recommended. © 2009 Springer Netherlands