Total (GSx) and reduced glutathione (GSH) remaining in synthetic RTLF following a 4 h incubation with three separate dung cake (DC) samples at 50 and 100 μg/ml. Reduced glutathione concentrations after 4 h are illustrated by dark grey bars, whilst the corresponding total glutathione concentration (GSx) are shown in light grey beneath the corresponding GSH data. The impact of co-incubation with the transition metal chelator DTPA (200 μM) is illustrated by the white bars, otherwise the figure is formatted as outlined in the legend to figure 1 with the following amendments. Notably DTPA incubation prevented not only the PM-induced loss of GSH but the background auto-oxidation seen in the particle-free controls. 'a" indicates that the concentration of GSH remaining after 4 h following co-incubation with DTPA was significantly greater than that in the 4 h particle-free control.