Summary of the particle size data for the soil samples, presented for all soil samples together and by endemicity.

<p>Summary of the particle size data for the soil samples, presented for all soil samples together and by endemicity.</p

Summary of the characteristics of the pure-phase reference minerals used in this study, including specific surface area (SSA), particle size (in water and deflocculant), Zeta Potential (ζ) and the haemolytic potential (given as the slope of absorbance versus soil suspension concentration).

<p>Summary of the characteristics of the pure-phase reference minerals used in this study, including specific surface area (SSA), particle size (in water and deflocculant), Zeta Potential (ζ) and the haemolytic potential (given as the slope of absorbance versus soil suspension concentration).</p

Box and whisker plot for normalised HA for the soil samples from podoconiosis-endemic, -non-endemic and areas with unknown endemicity.

<p>Box and whisker plot for normalised HA for the soil samples from podoconiosis-endemic, -non-endemic and areas with unknown endemicity.</p

Summary of the chemistry and mineralogy of the soils, presented for all soil samples together and by endemicity.

<p>Summary of the chemistry and mineralogy of the soils, presented for all soil samples together and by endemicity.</p

Potential nanoparticle penetration routes through the skin.

<p>A) 1) via broken epidermis, 2) intercellular route, 3) transappendageal route via hair follicles (or sweat ducts) and 4) intracellular route (modified from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0177219#pone.0177219.ref010" target="_blank">10</a>]) B) magnified schematic of a silica nanoparticle in the capillary, showing example surface features that are thought to contribute to HA in vitro.</p

HA of the soil samples (shown in terms of their endemicity) and PPRMs, presented as the slope of the HA normalised to DQ12.

<p>9A) shows the haemolysis curve for two selected samples.</p

Size distribution curves for sample DM-SE SO 22B and SO 4003.

<p>(A) and (E) were analysed in water (C) and (G) with deflocculant. Figs (B), (D), (F) and (H) represent the cumulative curved of (A), (C), (E) and (G), respectively.</p

Duration of shoe wearing (up to the date of interview) among cases and controls who owned shoes.

<p>Duration of shoe wearing (up to the date of interview) among cases and controls who owned shoes.</p

Average age of first wearing of shoes compared with income and age of onset of podoconiosis among cases.

<p>Average age of first wearing of shoes compared with income and age of onset of podoconiosis among cases.</p

Scatter matrix showing cases that were treated for podoconiosis^§.

<p><i>§No</i>t<i>e</i>: First noticed swelling and first treatment <i>r</i> = 0.9, age at first wearing shoes and income <i>r</i> = −0.04, age at first wearing shoes and first noticed <i>r</i> = 0.2, age at first wearing shoes and first treatment <i>r</i> = 0.2, first noticed swelling and income <i>r</i> = −0.1, income and first treatment <i>r</i> = 0.01.</p