Overview
Bortey-Sam and colleagues sampled cassava and plantain with the farm soils they grew in, in communities around the Tarkwa gold mines in June 2012. Arsenic, cadmium, chromium, nickel, lead (ICP-MS) and total mercury (thermal decomposition AAS) were measured, and soil-to-crop transfer factors and hazard quotients were calculated by community. Table 1 reports plantain as geometric mean, SD, median, minimum and maximum for all 32 samples; per-community plantain concentrations are not printed.
Key numbers
- Plantain geometric means (Table 1, Section 3.1): lead 0.0070, total arsenic 0.012, cadmium 0.0010, total mercury 0.0010, total chromium 0.025 and nickel 3.6 mg/kg.
- Plantain lead ranged 0.0022–0.020 mg/kg and nickel 2.9–4.1 mg/kg (Table 1).
- The authors report arsenic, cadmium, chromium and mercury in all foodstuffs below Codex values and attribute arsenic partly to deposition from ore roasting (Section 3.1).
Methods (brief)
HNO3/H2O2 digestion of 0.5 g dried sample; ICP-MS (Agilent 7700); total mercury by MA-3000. Blanks and duplicates every 10 samples; sediment and tissue reference materials with 80–115% recovery; no food-matrix reference material. Detection limits are printed in ng/g at values that appear to be instrument limits.
Evidence Fitness
The basis is internally inconsistent: Table 1 and Section 3.1 label foodstuff results mg/kg wet weight, while Section 2.3 says results are expressed on a dry-weight basis after drying at 45 °C. The plantain cadmium minimum is “nd” while its geometric mean, SD and median all equal 0.0010 mg/kg. In the library copy (a text conversion with scrambled table digits) several plantain cells cannot be read unambiguously (mercury and arsenic maxima, chromium median and maximum); the geometric means are confirmed by the paper’s text. The DOI and page numbers are not printed in the library copy.