AIRBORNE PARTICULATE QUARTZ AND RELATED HEALTH EFFECTS IN IOWA

Iowa is one of the five dustiest states in the nation due primarily to extensive perturbation of loess and glacial tills by modern agricultural practices. As a result, Iowa residents are subjected to an elevated risk of overexposure to particulate matter and the adverse health effects accompanying it. Crystalline quartz is classified as a group 2A carcinogen by IARC and is a primary constituent of airborne particulate matter 10 microns in diameter and smaller. OSHA’s current exposure limit for a dust composed of 10% quartz is 1.0mg/m³. Although the Iowa DNR monitors PM10 and PM2.5 statewide, this study will provide a more detailed look at the individual components of dust according to their relative sizes and abundance. Respirable dust is broken down into ten size classifications using a Multi-Orifice Uniform Deposit Impacter (MOUDI^TM). Particle size is sieved as a function of velocity in the following steps: 10µm, 5.6µm, 3.2µm, 1.8µm, 1.0µm, 0.55µm, 0.335µm, 0.180µm, 0.098µm and 0.055µm. The particulate matter is deposited onto a 47mm filter, which is then dissolved and its material sorbed onto a 25mm silver membrane filter for use on an x-ray diffractometer. The x-ray analysis not only provides the mineral identifications, but in conjunction with a calibrated set of standards can yield quantitative results. Modal mineralogy may then be compared regionally, statewide, or nationwide. Sampling will occur throughout the year in both rural and residential areas to record fluctuations caused by seasonal agricultural implementation and climatic changes. These results along with archived PM2.5 data from the DNR will be utilized in compiling statistical airborne particulate silica data. Prolonged exposure to high levels of airborne particulate quartz may be related to health risks including pulmonary diseases, such as silicosis, mesothelioma, and lung cancer. This study, coupled with demographic and health data from across Iowa, will help identify possible high-risk regions statewide.