Overview
Adam and colleagues bought three samples each of four cereals and three legumes at one Tamale market in December 2017. They measured arsenic, lead, cadmium, copper and zinc by flame AAS and estimated intake and risk. Cadmium was not detected in any food, and lead only in soybean and groundnuts.
Key numbers
- Arsenic means: rice 0.150, cowpea 0.079, sorghum 0.068, groundnuts 0.068, millet 0.059, soybean 0.055, maize 0.050 mg/kg (Tables 2 and 3, p. 3).
- Lead: not detected in maize, rice, millet, sorghum and cowpea; soybean mean 0.017 mg/kg with a minimum (0.020) above its maximum (0.015); groundnut values printed as negative (Table 3).
- Cadmium: not detected in all seven foods (Tables 2 and 3).
Methods (brief)
Dried, ground samples were digested with nitric acid and read by flame AAS. Printed detection limits (units not stated) include lead 2.0 and arsenic 0.02. Recoveries of 92 to 103% refer to calibration standards; no reference material was used.
Evidence Fitness
Very small (three samples per food, composited) and internally inconsistent. Lead values sit below the printed lead detection limit, one minimum exceeds its maximum, groundnut lead is negative, and copper and zinc are about 100 to 1000 times below normal grain levels. Arsenic by flame AAS at these levels is also uncertain. Raw maize grain is a proxy for corn-grits and bran-cereal-with-raisins, and cowpea and soybean are proxies for pinto-beans, refried-beans and pork-and-beans-canned; none of the thin pages are linked.