A Comparative Analyses of Granulometry, Mineral Composition and Major and Trace Element Concentrations in Soils Commonly Ingested by Humans.

This study compared the granulometric properties, mineralogical composition and concentrations of major and trace element oxides of commonly ingested soils (geophagic soil) collected from different countries with a view of understanding how varied they may be in these properties and to understand the possible health implications of ingesting them. Soil samples were collected from three different countries (South Africa, Swaziland and Democratic Republic of Congo (DRC)) and their granulometric properties, concentrations of major and trace element oxides as well as mineralogical composition determined. Differences were observed in the granulometric properties of geophagic soil from the three different countries with most of them having <20% clay content. The soils also showed varied degrees of weathering with values of Chemical Index of Alteration (CIA) and Chemical Index of Weathering (CIW) being between 60% and 99.9% respectively. The mineral assemblages of the soils from South Africa and Swaziland were dominated by the primary minerals quartz and feldspar whereas soils from DRC had more of kaolinite, a secondary mineral than primary minerals. Soils from DRC were associated with silt, clay, Al2O3, and CIA unlike most samples from South Africa which were associated with SiO2, sand, K2O, CaO, and MgO. The soils from Swaziland were closely associated with silt, H2O and Fe2O3(t). These associations reflect the mineralogy of the samples. These soils are not likely to serve as nutrient supplements because of the low concentrations of the nutrient elements contained. The coarse texture of the samples may also result in dental destruction during mastication. Sieving of the soils before ingestion to remove coarse particles is recommended to reduce the potential health threat associated with the ingestion of coarse-textured soils.

Influence of physico-chemistry and mineralogy on the occurrence of geohelminths in geophagic soils from selected communities in the Eastern Cape, South Africa, and their possible implication on human health.

Geophagic soils from selected communities in Eastern Cape, South Africa were characterised to determine their properties and geohelminth content. The soils were coarse-textured with cation exchange capacity values ranging from 6.35 to 18.94 cmol (+)/kg. Quartz was the dominant mineral in the samples with SiO2, Al2O3, and Fe2O3(t) having the highest concentrations among major element oxides. The soil properties, mineralogical composition, and low amounts of particle binding substances may favour the survival of geohelminth ova in the soils. Seven of the samples contained at least one of the following geohelminths: Ascaris lumbricoides, Trichuris trichiura, Necator americanus, Ancylostoma duodenale and Strongyloides stercoralis. The presence of these geohelminths in the soils was attributed to agricultural and sanitary practices inherent in the communities and the soil properties. Communities need to be sensitised on the importance of safe sanitary and animal husbandry practices to reduce the prevalence of helminth infection among geophagists.

Microbiological characterisation of southern African medicinal and cosmetic clays.

The effects of traditionally used medicinal and cosmetic clays in southern Africa on selected microorganisms were studied using microbiological media. The clay pH, microchemical composition, kind of associated microorganisms and antimicrobial activity of clays against test microorganisms were determined. The clays contained varying numbers of microorganisms which ranged from 0 up to 105 CFU/g. Clay pH ranged from 2.3-8.9. Neither Escherichia coli, nor other faecal coliforms were detected. Clays of pH value of <4 displayed antimicrobial activities. Clays which were active against test microorganisms had Na(2)O, Al(2)O(3), SiO(2), SO(3), CuO or Cl(2)O as major components. Microbial activity of clays was attributed mainly to low pH but cations such as Cu, Al, S or Cl and various anions might have contributed to the microbicidal effects. No antimicrobial activity was established for many of the clays commonly used in the treatment of common ailments of microbial origin.