Spatial distributions of arsenic exposure and mining communities from NHEXAS Arizona

Within the context of the National Human Exposure Assessment Survey (NHEXAS ), metals were evaluated in the air, soil, dust, water, food, beverages, an d urine of a single respondent. Potential doses were calculated for five me tals including arsenic. In this paper, we seek to validate the potential do se calculations through spatial analysis of the data. Others report elevate d arsenic concentrations in biological and environmental samples from resid ents of mining towns, particularly Ajo, Arizona. These reports led us to ex pect potential arsenic doses above the 90th percentile of the NHEXAS exposu re distribution to be from residents of mining communities. Arsenic dose wa s calculated using media concentrations, time activity patterns, and publis hed exposure factors. Of the 179 homes evaluated, 54 were in mining communi ties; 11 of these were considered separately for reasons of population bias . Of the 17 homes with the greatest potential arsenic doses, almost half (4 7%) were in mining communities. We evaluated the potential doses by media f rom nonmining and mining areas using the nonparametric Mann-Whitney U test. Statistically significant(p = 0.05) differences were found between mining (n = 43) and nonmining sites (n = 122) for total exposure and for each of t he following media: house dust, yard soil, outdoor air, beverage consumed, and water consumed. No differences were found in either food or indoor air of mining and nonmining areas. We eliminated outliers and repeated the test for all media; significance increased. Dietary, organic arsenic from fish consumption contributed to elevated arsenic exposure among people from nonm ining communities and acted as an initial confounder. When controlling for fish consumption, we were able to validate our potential dose model using a rsenic, particularly in Ajo. Further, we identified three mining communitie s lacking elevated arsenic exposure. Additional work is needed speciating t he arsenic and evaluating health risks. The utilization of Geographic Infor mation System facilitated spatial this project and paves the way for more s ophisticated future spatial analyses.