Overview
Dada and colleagues bought five traditional leafy vegetables from vendors at three Ibadan markets, in the morning and in the evening, over 12 weeks, and measured lead, cadmium, zinc, nickel and copper by AAS after drying. Table 1 gives mean ± SD by vegetable and time of day. Lead was higher in evening purchases for every vegetable.
Key numbers
- Lead, all samples (Table 1, mg/kg): soko 0.94 ± 0.81, ewedu 1.08 ± 1.41, ugwu 0.43 ± 0.35, waterleaf 1.71 ± 2.07, tete 1.50 ± 1.50.
- Cadmium, all samples (Table 1, mg/kg): 0.02 (soko) to 0.17 (ugwu, waterleaf).
- Pooled lead rose from 0.62 mg/kg in morning purchases to 1.65 mg/kg in evening purchases (Table 2).
Methods (brief)
Leaves were washed, oven-dried at 105 °C, ground and digested by microwave in nitric acid, perchloric acid and hydrogen peroxide (USEPA 3052A), then read by AAS. No reference material, recovery or detection limit is reported.
Evidence Fitness
The number of samples per vegetable is not stated and the standard deviations are often larger than the means. Table 2’s pooled cadmium and nickel means do not agree with Table 1, and the zinc values are unusually low for leafy vegetables, so analytical quality is uncertain. Values appear to be dry weight. All five foods are leafy vegetables and bear directly on non-root vegetables.