Exhaled Breath Condensate: A Novel Matrix for Biological Monitoring to Assess Occupational Exposure to Respirable Crystalline Silica

Biological monitoring (BM) is a useful way of determining overall exposures to chemical substances; however, in the case of respirable crystalline silica (RCS), this has not been analytically feasible in conventional biological matrices. The aim of this study was to investigate the utility of exhaled breath condensate (EBC) as a potential biological matrix in which to determine exposure to RCS. A small pilot study was undertaken collecting EBC from six quarry workers and six occupationally unexposed persons; the samples were analysed using both single particle inductively coupled plasma mass spectrometry (spICP-MS) and transmission electron microscopy (TEM). The results showed that EBC obtained from the occupationally unexposed persons exhibited low background levels of dissolved silica whilst silica particles of various sizes were present in samples from quarry workers. This is the first study to report EBC as a potential biological matrix that allows differentiation of RCS concentrations between samples from workers and occupationally unexposed controls. The results shown here confirm the presence of RCS in EBC by both spICP-MS and TEM. However, there are difficult analytical challenges still to be overcome before this can be used as a BM method to determine workplace exposure, these are currently being investigated.