A geochemical and mineralogical characterization of soils associated with podoconiosis.

Podoconiosis is a disease that causes swelling and disfiguration of the lower legs found in several developing countries where shoes are not regularly worn. The current model for the etiology of the disease proposes that mineralogical agents enter the lymph system through the skin leading to inflammation that causes swelling of the feet and legs. We collected 125 soil samples from 21 towns associated with podoconiosis, 8 towns unassociated with Podoconiosis as controls, and 3 towns of unknown status. Data collected for each soil sample included color, particle size, mineralogy, and geochemistry to distinguish unique components within the podoconiosis-associated soils. Our results indicate podoconiosis-associated soils are more highly weathered than non-podoconiosis associated soils. The enrichment of kaolinite and gibbsite suggests that these minerals, their surface chemistry, and trace elements associated with them should be prioritized in future podoconiosis research. In addition, we found that color may be a valuable tool to identify soils at greater risk for inducing podoconiosis.

Regional bedrock geochemistry associated with podoconiosis evaluated by multivariate analysis.

Podoconiosis is a disease whose etiology remains murky. Currently, the disease is attributed to particles that are believed to move through the skin and into the lymphatic system causing swelling of the lower legs. Identity of these particles or their composition remains unclear, though the presence of silicon and/or aluminum is often noted and frequently cited as causal agents. We applied multivariate analyses to the bedrock compositions of a large set of cases from an online database in an effort to identify underlying patterns or combinations of relative element abundances associated with podoconiosis-endemic regions. Using a combination of principal component analysis, discriminant function analysis, and ANOVA, we analyzed ten oxides from five regions on the African continent known to be associated with podoconiosis. The Hawaiian Islands were included as a control group since they are not known to have cases of podoconiosis despite similarity in geology and agricultural practices. Our analyses suggest that a unique alkaline- and silicon-rich geochemistry underlies regions associated with podoconiosis. Our results also imply that minerals enriched in incompatible elements, such as Ca, K, Mg, and Na, may be stronger predictors of the presence of the disease than either silicon or aluminum.