Overview
Okorafor and colleagues measured arsenic, nickel, aluminum, copper and macro elements by ICP-OES in six dry seeds, cereals and legumes from four markets in Nasarawa, Nigeria, and estimated hazard and cancer risks. Per-crop means are shown only in a bar chart; the text gives the range across crops. Reported arsenic of 5 to 31 mg/kg is far above typical crop values.
Key numbers
- Arsenic across crop means: “5.0 to 31.1 milligrams per kilogram”, highest in sesame (Section 3.1, p. 39).
- Aluminum: “104 to 580 milligrams per kilogram in soya bean and sesame”; copper “20.8 to 102” in sorghum and sesame (Section 3.1, p. 39).
- Soya bean arsenic is listed as ND in the hazard tables (Tables 1-3, pp. 41-43).
Methods (brief)
Composited samples were digested in aqua regia with hydrogen peroxide and read by ICP-OES (Agilent 720) following an adapted US EPA Method 200.7. Spike recoveries were 93 to 117 percent; no detection limits are given.
Evidence Fitness
Composites hide market-to-market variation, and per-crop values are figure-only, so only cross-crop extremes are extracted. Arsenic at tens of mg/kg by ICP-OES is implausible for grains and legumes and should be treated with caution. Black eye bean is a dry legume proxy for canned-green-beans; no canned beans were measured, and that page is not linked. The manifest listed the first author by her given name (Lydia).