P.191 The impact of physical activity and fitness on resilience to modern-life stress and the role of brain-derived neurotrophic factor (BDNF)

Abstract

Although zinc is ubiquitous in ambient particulate matter (PM), exposure to size fractionated residual oil fly ash (ROFA) PM is of particular concern due to several studies implicating particle zinc in mortality, adverse respiratory and cardiac effects. The lack of zinc speciation data is an impediment to our understanding of the biological mechanism of Zn induced toxicity. ROFA PM2.5+ samples (i.e. particle with aerodynamic diameter >2.5 μm) are prepared in a small 732 kW practical fire tube boiler by combusting one No. 5 and three No. 6 residual oil(s) of varying sulfur and ash contents. The combined X-ray absorption spectroscopy and selective extraction method is used to determine the Zn speciation in PM2.5+ samples. The Zn speciation in ROFA PM2.5 (i.e. particle with aerodynamic diameter <2.5 μm) samples, reported earlier, is included here for comparison purposes. The data show that zinc sulfate is predominant in both fractions. In addition, an appreciable amount of zinc phosphate was detected in the PM2.5 fraction. The insoluble zinc forms in both the fractions are identified as Zn-sorbed-ferrihydrite and zinc sulphide. The variation of Zn speciation across different size fractions has implication on the bioavailability and toxicity of Zn. Such source specific speciation data are needed for developing source inventories, and for amending existing regulations/framing new regulations for different size fractions.