"Assessing Health Risks Associated with Metal-Rich Soils, Mine Tailings and Household Dust"

Heather Jamieson, Queen’s University, Canada

The risk to human health associated with ingestion or inhalation of metal-bearing particles is expected to be directly influenced by the chemical form of the metal as well as the particle size. We have applied synchrotron-based micro-analytical methods to characterizing complex samples at the micron scale, with an emphasis on microXANES and microdiffraction experiments performed at beamline X26a, NSLS. The first project to be presented involves arsenic-rich mine tailings distributed at publicly-accessible abandoned gold mine sites in Nova Scotia. These areas are regularly used for recreational activities such as dirt bike racing and are increasingly surrounded by housing developments. We used X-ray microprobe analysis to examine 20 samples from five gold mine sites and found that each sample contained four or more different arsenic-bearing minerals. These include sulfides, Fe arsenates, Ca-Fe arsenates, As-bearing Fe oxides. In-vitro bioaccessibility tests simulating the stomach (low pH) and intestine (high pH) were conducted on the same suite of samples. Arsenic hosted in sulfide and Fe arsenate particles exhibits low bioaccessibility, whereas As from samples rich in Ca-Fe arsenates had higher bioaccessibility. The correlation between mineralogy and bioaccessibility could not have been discerned without the ability to identify As-hosting particles using the X-ray microprobe. The second project involves the characterization of various metals in household dust. It is estimated North Americans spend over 80% of their time indoors. Frequent hand-to-mouth activity results in particularly high exposure of young children to ingested dust. Our preliminary investigation of dust samples provided by Health Canada indicate that element mapping using the X-ray microprobe reveals metal-rich hot spots which can then be analysed using microdiffraction. This approach shows great promise for identifying the source of the particles and predicting metal bioaccessibility and potential health risk.