Overview
Mafe and colleagues review the microbiological and chemical safety of calabash chalk eaten during pregnancy, covering minerals, pesticide residues, heavy metals, pathogens and animal toxicology studies. The heavy metal section compiles lead, cadmium, arsenic and mercury ranges in calabash chalk and edible clays from several countries, quoted from earlier studies. It reports no new measurements.
Key numbers
- Table 3 quotes ranges such as lead 0.2 to 3.5 mg/kg and cadmium 0.05 to 1.2 mg/kg for clay from south-east Nigeria, attributed to an earlier paper (Table 3, p. 6).
- The same table prints a “WHO Standard” of 0.01 mg/kg for lead, cadmium and arsenic and 0.001 mg/kg for mercury, which is not a recognized limit for clay (Table 3).
Methods (brief)
Narrative review of the literature; no search protocol or new sampling is described.
Evidence Fitness
Context only. The quoted ranges come from other studies and could not be checked against those papers here, so they should not be used as occurrence data. Use the primary studies instead. The review does not measure cosmetic clays and is not evidence for cosmetic-clay.