Abstract:
Quantifying exposure to manganese (Mn) in airborne welding fume, and the resultant dose, presents many challenges. Common biomarkers such as Mn in blood or Mn in urine have not proven to be practical even in studies where positive associations were observed. Hair Mn (MnH) is another potential biomarker. It is easy to obtain and grows slowly, so it has the advantage over blood and urine of being less influenced by short term variability in Mn exposure levels. The objective of this research was to determine whether hair can be used as a biomarker for welders’ exposure to manganese. This body of work investigates three aspects of using hair as a biomarker: (1) whether airborne Mn (MnA) is associated with bulk hair Mn (MnH(B)), (2) whether MnH(B) is associated with Mn determined by laser ablation of individual hair strands (MnH(La)), and (3) whether MnH(La) can be used as an indicator of MnA exposure. MnH(B) samples (1 cm length) were collected from each of 47 welding school students and personal air sampling was conducted to determine their individual MnA exposures. A moderate association between bulk MnH (MnH(B)) and MnA was found. The investigation of whether Mn measured by laser ablation inductively coupled mass spectrometry (LA-ICP-MS) of individual hair strands (MnH(La)) is associated with MnH(B), and could be used to improve the limited time resolution provided by MnH(B), led to the development of a new calibration standard for this work. Hair strands with known Mn concentrations are not available, so a series of calibration standards consisting of gelatin samples spiked with known concentrations of Mn (MnG) were developed. The MnG calibration results were compared to Mn concentrations determined via acid digestion of bulk hair samples followed by inductively coupled mass spectrometry (ICP-MS), and indicated an association between the MnG calibration standards developed for this study and MnH(B). The final investigation found no association between MnA and temporally-resolved MnH(La). Further steps toward the achievement of this objective are discussed.