Abstract
Most of the microorganisms occurring in geophagic clays are undesirable and may to some extent be harmful to geophagists; it is therefore important to develop a cheap and sustainable technique for the treatment of these clays prior to consumption. In this study, a solar treatment simulated in a chamber has been investigated for its potential to inactivate the microorganisms found in the geophagic clays obtained from mining sites and from the markets. The results have shown that irrespective of the sources of the clays, they were contaminated with large amount of potentially harmful microorganisms which could have been sustained by suitable conditions such as relatively high moisture content (average of 3.6%) and the presence of organic carbon (between 1.06 and 1.5%). Treatment with simulated solar irradiation has resulted in most instances to the reduction of the number (up to 100% inactivation) of microorganisms although in few cases the same conditions have stimulated the growth of some dormant microorganisms including Bacillus subtilis, Paenibacillus, Bacillus cereus, Bacillus thuringiensis, Bacillus humi and Arthrobacterarilaitensis. This study shows that the solar treatment has the potential to significantly reduce the amount of microorganisms occurring in the geophagic clays, but require further investigation for improvement of the technique. Key words: Geophagic clays, solar treatment, microorganisms, moisture content, organic carbon, mining sites, markets.  
Highlights
A solar treatment simulated in a chamber has been investigated for its potential to inactivate the microorganisms found in the geophagic clays obtained from mining sites and from the markets
The results have shown that irrespective of the sources of the clays, they were contaminated with large amount of potentially harmful microorganisms which could have been sustained by suitable conditions such as relatively high moisture content and the presence of organic carbon
This study shows that the solar treatment has the potential to significantly reduce the amount of microorganisms occurring in the geophagic clays, but require further investigation for improvement of the technique
Summary
A correlation has been established between the occurrence of Yersinia enterocolitica, Escherichia coli, Streptococcus faecalis, Helicobacter pylori, and Mycobacteria and the aetiology of Crohn’s Disease which is characterized by a severe, non-specific, chronic inflammation of the intestinal wall (Liu et al, 1995; Rubery, 2002; Lamps et al, 2003) Geophagists often pretreat their clays using heat treatment (baking and burning) mostly to improve the taste of the clays (BisiJohnson et al, 2013). Its germicidal effect is based on the combined effect of thermal heating of solar light and optical inactivation (UV radiation) (McGuigan et al, 2012) This means that the disinfection of microorganisms increases (inactivate pathogens at faster rate) when they are exposed to both thermal inactivation and UV-A light at the same time. To the best of our knowledge no study has so far considered to investigate the impact of solar treatment on the disinfection of geophagic clays
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