Overview
Mouri and colleagues collected 12 geophagic soils and clays from the places where residents of three villages in Limpopo collect them, and measured major elements by XRF and trace elements by ICP-MS. They also tested gastric and intestinal bioaccessibility on seven samples and calculated hazard quotients. Chromium, manganese and arsenic drove hazard indices well above 1 in every sample.
Key numbers
- Lead: 0.18 mg/kg (DRI-01) to 2.68 mg/kg (GAM-01), average 1.85 mg/kg (Table 2).
- Arsenic: 0.32 to 4.37 mg/kg (TAU-01), average 1.56 mg/kg (Table 2).
- Chromium: 25.02 to 357 mg/kg, highest in a mining-dump sample (DRI-02), average 105 mg/kg (Table 2).
- Nickel: 17.55 to 77.7 mg/kg, average 40.5 mg/kg (Table 2).
Methods (brief)
Trace elements were measured by ICP-MS after microwave digestion of 0.30 g with nitric and hydrochloric acid; major oxides by XRF on fused discs. Bioaccessibility used a two-step physiologically based extraction test. No detection limits or reference materials are reported, and cadmium and mercury were not measured.
Evidence Fitness
Twelve single samples from three villages, with no QA data or detection limits. Three samples come from mining dumps, so the set is not a general background. Values are pseudototal concentrations, and bioaccessible fractions were low for arsenic and chromium (figure-only per sample). These are eaten soils and clays, so they are direct evidence for clay-geophagy; they are only a proxy for cosmetic-clay, a non-food use, and should not be compared with food bands.