Overview
Nkansah and colleagues bought 30 pieces of baked white clay sold for eating at 10 Kumasi markets and measured elements by portable XRF, with arsenic checked by ICP-MS in six samples. Every sample contained arsenic and lead, mercury was detected in three samples, and cadmium was below detection in all. The authors estimate intakes and cancer risk for a 70 g daily portion.
Key numbers
- Arsenic: 8.11 to 14.18 ppm across samples; mean 10.55 mg/kg (Table 1b; Table 4a).
- Lead: 21.35 to 30.90 ppm; mean 25.06 mg/kg (Table 1b; Table 4a).
- Mercury: detected in ASA1 (5.71 ppm), ASY2 (9.75 ppm) and BAN3 (8.72 ppm); others below the 1.70 ppm LOD (Table 1b).
- Cadmium: below the 1.90 ppm LOD in all 30 samples (Table 1b).
Methods (brief)
Clay was air-dried to constant weight, crushed and sieved to 250 µm, then scanned for 180 s with a Thermo Niton XL3t XRF analyzer (USEPA Method 6200), calibrated with a soil reference material. Six samples were also digested in modified aqua regia and run by ICP-MS, with results shown only in a figure. Results are on a dry basis.
Evidence Fitness
Thirty market samples of a ready-to-eat clay, analyzed by field-portable XRF with ppm-level detection limits, so cadmium and mercury non-detects are weakly bounded. The printed overall mercury mean (0.81 mg/kg) counts non-detects as zero and sits below the LOD. Direct evidence for clay-geophagy; only a proxy for cosmetic-clay, which is a non-food use and should not be read against food bands.