Overview
Onakpa and colleagues bought seven vegetables and banana at Gwagwalada Central Market, Abuja, in July 2019 and measured copper, manganese, lead, nickel, cadmium and chromium by atomic absorption spectrometry. Samples were washed, oven-dried at 100 °C and powdered, so results appear to be on a dry-weight basis, although Table 1 does not say so. The paper adds daily intake and hazard index estimates.
Key numbers
- Lead (Table 1, mg/kg, mean ± SEM): cucumber 8.65 ± 1.1, cabbage BDL, banana 100.40 ± 10.0, lettuce 68.00 ± 7.0, green pea 64.76 ± 5.8, carrot 61.28 ± 5.6, onion 8.92 ± 1.1.
- Cadmium was detected only in cabbage (0.10 ± 0.1 mg/kg); nickel was below detection in every vegetable (Table 1).
- Chromium reached 193.87 ± 12.6 mg/kg in green pea (Table 1).
Methods (brief)
Two grams of dried powder were digested in nitric acid at 80 °C. Cadmium, chromium, nickel and lead were read by graphite furnace AAS, and copper and manganese by flame AAS. The paper reports blanks every five samples and recoveries within 2% of certified values for an unnamed reference material. Results are given as mean ± standard error of the mean.
Evidence Fitness
The number of samples per vegetable is not reported, and all samples come from one market in one month. The lead values (up to about 100 mg/kg) are far above what market produce normally holds, and the daily intake table does not follow from the concentrations, so treat the numbers with caution. The paper prints the Latin name for cucumber as an amaranth species. Raw carrot here is only a proxy for root-vegetable-purees, so that page is not linked. Cucumber, cabbage, lettuce, green pea and onion bear directly on non-root vegetables.