10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Concentration Levels of Airborne Nanoparticles in Taconite Processing
NIMA AFSHAR-MOHAJER, Rebecca Foos, Karl Braun, John Volckens, Gurumurthy Ramachandran, Johns Hopkins School of Public Health
Abstract Number: 883 Working Group: Workplace Aerosol
Abstract Most studies of health risks in taconite mining and processing have focused on respirable dust mass concentrations and elongated mineral particles. However, many ore processing steps generate large amounts of nano-sized aerosol. Such particles, particularly ultrafine particles (UFPs, those with an aerodynamic diameter smaller than 0.1 µm) have been linked to increased cardiovascular disease in urban air pollution studies. Ultrafine particles contribute very little to the overall mass but are abundant in number. There is some evidence that particle number and surface area concentrations may be better metrics of exposure than mass concentrations.
In this study, we monitored concentrations of the airborne nanoparticles at four major processing units of a taconite surface mine: crushing, dry milling, wet milling, and pelletizing (United Taconite Mine, Iron Junction, MN, USA). We used three stations of direct-reading instruments to estimate particulate mass concentrations (PM1, PM2.5, Respirable, and PM10) and particulate number concentrations (PN) and lung-deposited surface area concentrations (LDSA) of the nanoparticles, on two different days. Results revealed that pelletizing operation produces the highest nano-aerosol pollution as measured by three Partector (Naneos GmbH, Windisch, Switzerland), three DiSCmini (Testo GmbH, Titisee-Neustadt, Germany) nano-aerosol monitors, and two DustTrak (Model 8534, TSI Inc., St. Paul, MN, USA), on both days. However, the maximum instant LDSA concentrations (323 µm2/cm3 as measured by Partector units and 409 µm2/cm3 as measured by DiSCmini units) were related to the crushing operation. In Day 1, the average concentrations of nanoparticles across processing operations, from the highest to the lowest, were: (LDSAPartector = 192 µm2/cm3, LDSADiSCmini = 144 µm2/cm3, PN = 1.55⨯105 #/cm3, PM1: 199 µg/m3 in the pelletizing operation; LDSAPartector = 125 µm2/cm3, LDSADiSCmini = 142 µm2/cm3, PN = 1.54⨯105 #/cm3, PM1: 148 µg/m3 in the crushing operation; LDSAPartector = 96 µm2/cm3, LDSADiSCmini = 73 µm2/cm3, PN = 9.96⨯104 #/cm3, PM1: 97 µg/m3 in the dry milling operation; LDSAPartector = 85 µm2/cm3, LDSADiSCmini = 77 µm2/cm3, PN = 9.06⨯104 #/cm3, PM1: 103 µg/m3 in the wet milling operation. Power spectrum analysis was conducted to identify periodicity in the concentrations resulting from processing operations. The intraclass correlation coefficient (ICC) was used to evaluate between-day measurements.