Children living near contaminated mining waste areas may have high exposures to metals from the environment, according to a study by researchers at the University of Arizona Mel and Enid Zuckerman College of Public Health and the UA Health Sciences.
The study in the journal Environmental Research looked at whether exposure to arsenic and lead is higher in children in a community near a legacy mine and smelter site in Arizona compared to children in other parts of the United States and the relationship of that exposure to the site.
The research team found exposures to arsenic were high compared to children from other areas and water and soil were important exposure pathways for arsenic. Non-site related pathways were as important as site-related ones for exposures.
Arsenic and lead were measured in residential soil, house dust, tap water, urine, and toenail samples from 70 children in 34 households up to 7 miles from the site. Soil and house dust were sieved, digested, and analyzed via ICP-MS. Tap water and urine were analyzed without digestion, while toenails were washed, digested and analyzed. Blood lead was analyzed by an independent, certified laboratory. Spearman correlation coefficients were calculated between each environmental media and urine and toenails for arsenic and lead.
Geometric mean arsenic (standard deviation) concentrations for each matrix were: 22.1 (2.59) ppm and 12.4 (2.27) ppm for soil and house dust (<63 μm), 5.71 (6.55) ppb for tap water, 14.0 (2.01) μg/L for specific gravity-corrected total urinary arsenic, 0.543 (3.22) ppm for toenails. Soil and vacuumed dust lead concentrations were 16.9 (2.03) ppm and 21.6 (1.90) ppm.
The majority of blood lead levels were below the limit of quantification. Arsenic and lead concentrations in soil and house dust decreased with distance from the site. Concentrations in soil, house dust, tap water, along with floor dust loading were significantly associated with toenail and urinary arsenic but not lead. Mixed models showed soil and tap water best predicted urinary arsenic.
Despite being present in mine tailings at similar levels, internal lead exposure was not high, but arsenic exposure was of concern, particularly from soil and tap water. Naturally occurring sources may be an additional important contributor to exposures in certain legacy mining areas.