Overview
Rukondo and colleagues bought dry soil sticks sold for eating at six markets in three Tanzanian regions in 2019 and measured eleven elements by flame AAS, then estimated daily intake, target hazard quotients and cancer risk. Lead, chromium and nickel were found in every sample, and cadmium only in the two Mwanza markets. Total hazard quotients exceeded 1 at every site.
Key numbers
- Lead: 3.8 ± 0.014 mg/kg (Njombe) to 6.85 ± 0.006 mg/kg (Mawenzi) (Table 4).
- Cadmium: 0.4 ± 0.00 mg/kg at Mkuyuni and Kirumba; not detected elsewhere (Table 4).
- Chromium: 62.7 to 638.6 mg/kg, highest at the Morogoro markets (Table 4).
- Nickel: 93.1 ± 0.22 mg/kg at Mkuyuni (Table 4).
Methods (brief)
Sticks were oven-dried at 110 °C, ground and sieved to 75 µm, digested in aqua regia with added perchloric acid and analyzed on a PerkinElmer Analyst-100 flame AAS. The marine sediment reference material IAEA-356 gave 96.8 to 116 percent recovery. Results are mean ± SD on a dry basis.
Evidence Fitness
Market-bought material with reference-material QA, but the number of samples per market is not stated and the tiny SDs suggest replicate readings rather than separate samples. Detection limits are not printed. Direct evidence for clay-geophagy; only a proxy for cosmetic-clay, a non-food use not comparable with food bands.