Spatial distributions of arsenic exposure and mining communities from NHEXAS Arizona

Abstract

Within the context of the National Human Exposure Assessment Survey (NHEXAS), metals were evaluated in the air, soil, dust, water, food, beverages, and urine of a single respondent. Potential doses were calculated for five metals including arsenic. In this paper, we seek to validate the potential dose calculations through spatial analysis of the data. Others report elevated arsenic concentrations in biological and environmental samples from residents of mining towns, particularly Ajo, Arizona. These reports led us to expect potential arsenic doses above the 90th percentile of the NHEXAS exposure distribution to be from residents of mining communities. Arsenic dose was calculated using media concentrations, time activity patterns, and published exposure factors. Of the 179 homes evaluated, 54 were in mining communities; 11 of these were considered separately for reasons of population bias. Of the 17 homes with the greatest potential arsenic doses, almost half (47%) were in mining communities. We evaluated the potential doses by media from 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 the 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 nonmining communities and acted as an initial confounder. When controlling for fish consumption, we were able to validate our potential dose model using arsenic, particularly in Ajo. Further, we identified three mining communities lacking elevated arsenic exposure. Additional work is needed speciating the arsenic and evaluating health risks. The utilization of Geographic Information System facilitated spatial this project and paves the way for more sophisticated future spatial analyses.

Measured versus modeled dietary arsenic and relation to urinary arsenic excretion and total exposure

“…The minimum detection limit in water was 0.20 μg/L (26,30). Arsenic exposure via drinking water and water used for food preparation (generally tap water) were calculated separately, as the product of the concentration (μg/L) times the quantity consumed (L/day).…”

“…NHEXAS used a proportion-based sample of the total population in Arizona to evaluate multiple contaminant exposures via multiple pathways (25–27). The methods used for sampling and analysis of metals have been described in detail by O’Rourke et al, 1999 (30). Diet and time-activity diaries were completed and duplicate food samples, water sample from multiple sources, urine and other media were collected for 179 subjects.…”

Arsenic uptake and speciation in vegetables grown under greenhouse conditions

“…Arsenic in these contaminated soils may cause adverse effects due to inhalation of dust, ingestion, or from the consumption of fruits and vegetables grown in these soils. The ingestion of As-contaminated soils for example, has been linked to elevated As blood concentrations in children living around or near smelter or mining processing facilities (Orouke et al 1999;Carrizales et al 2006). Currently, human exposure to As-contaminated soils is conservatively estimated as the total metal concentration in the soil or dust multiplied by the amount of material inhaled or ingested (Ruby et al 1999).…”

Comparison of global positioning system (GPS) tracking and parent-report diaries to characterize children's time–location patterns

“…One of the most widely used diaries for human exposure assessment in the US is the National Human Exposure Assessment Survey (NHEXAS). Approximately 600 people in four EPA regions participated in this survey between 1994 and 1999 (Echols et al, 1999;Freeman et al, 1999;O'Rourke et al, 1999;Robertson et al, 1999;Whitmore et al, 1999;Quackenboss et al, 2000;Freeman et al, 2001). The diary timeline, which was one component of the larger survey, was designed to provide data whose resolution was comparable to the temporal resolution of the environmental and human samples collected (Freeman et al, 1999).…”