GIS Applications to Exposure Assessment of Airborne Crystalline Silica (Quartz) and Its Health Impacts in Mohammad and Malakand Agency, Northern Pakistan

Geographic Information System (GIS) has recently emerged as innovative tool in the field of exposure assessment and environmental epidemiology to analyze the spatial distribution of the disease burden and the relationship of environmental risk factors including the causative agents, routs of exposure, exposure assessment and the demographic information. During this study forty (40) samples of rock and airborne particulates of thoracic fraction (PM10µ), respirable fraction (<2.5µ), fine particles (<2.5µ) and total suspended particulates (TSP) were collected from various silica mining and milling units located in the target area. These samples were analyzed using AD spectroradiometer, X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and Polarized Light (PLM). The type of silica was identified as alpha quartz and the exposure level was estimated as thousand times beyond the permissible exposure limit in all units. General incidence and cohort cases of lung cancer, silicosis, and asthma and eye allergies were identified. These results were interpreted using GIS techniques including geocoding, spatial clustering, spatial interpolation (kriging method) and cumulative exposure assessment. Geocoded maps display the geographic location of silica deposits, mines and milling units and population information of the area under investigation. Spatial geographic clustering and interpolation maps define and verify the relationship between the exposure level, exposed groups and the silica related diseases burden including morbidity and mortality rate in the study area. Overall this study emphasizes the role and value of geographical information systems (GIS) and spatial autocorrelation in exposure modeling and environmental epidemiology.