Analytical methods to investigate occupational exposure to toxic elements and their species

With many occupations involving the use of chemicals considered hazardous to health, the use of biological monitoring to monitor and control exposure to chemicals may help to reduce the risk of ill health. However, this is not always possible for all elemental workplace exposures. The work in this PhD thesis outlines the improvement of existing methodologies and,the development of novel speciation methodologies, including single particle analysis. It furthers biological monitoring research of elements that are of a carcinogenic occupational concern, i.e. inorganic arsenic, hexavalent chromium and respirable crystalline silica (RCS). Current biological monitoring methods are either no longer deemed fit for purpose (arsenic), not ideal (chromium) or are not available (RCS). The limitations of occupational exposure assessment of hexavalent chromium and RCS are linked to the unsuitability of biological matrices for biological monitoring purposes. Therefore, the work in this thesis also evaluates exhaled breath condensate (EBC) for its potential as a new biological matrix for biological monitoring of chromium and RCS. The analytical technique used for arsenic speciation, chromium speciation and single particle analysis of RCS was inductively couple plasma – mass spectrometry (ICP-MS). Separation was achieved for the chromium and arsenic methodologies by hyphenating the ICP-MS with a micro liquid chromatography (μLC) system coupled to an anion exchange column. For arsenic speciation, a novel and robust 6-minute method was established. Additionally, a background levels study was conducted to establish an unexposed background reference range for five species of arsenic, to improve interpretation of biological monitoring results. Unexpected arsenic peaks in routine biological monitoring samples were also investigated, with one of which being determined as thio-DMA. For chromium speciation, a novel method to simultaneously separate and detect both hexavalent and trivalent species in EBC was developed, incorporating a storage stability study of both species of chromium in EBC. This was followed by a feasibility study, which determined that both species of chromium can be detected and measured in ‘real’ EBC samples and that occupationally exposed workers showed significantly higher levels of both chromium species in EBC samples compared to an unexposed control group. For RCS, the potential of utilising EBC to both detect and measure occupational exposure to RCS, employing the new and challenging analytical technique of single particle ICP-MS, was studied. The work demonstrated that individual particles of silica can be detected and counted in an EBC sample, with occupationally exposed workers showing significantly more RCS particles than an unexposed control group.