Use of Biomonitoring for Arsenic, Mercury and Lead to Assess Exposure and Health Risks in Children in a Northern Canadian Smelter Community

摘要

Emissions from a mine and base metal smelting complex in a northern Canadian community have resulted in elevated concentrations of a number of metals and metalloids in the surrounding environment. Results from a human health risk assessment indicated that arsenic, lead, and inorganic mercury were present at concentrations in the local environment that warranted further assessment of exposure and risk. An initial biomonitoring study was undertaken for local children to examine urinary arsenic, blood lead, and urinary inorganic mercury levels. Overall, 447 children participated in the study providing 202 blood samples and 379 urine samples. The biomonitoring study was conducted to assess exposure and potential health risks, as well as to identify personal factors that may be associated with measured internal exposures of children in the community. Results demonstrated that despite elevated concentrations of arsenic and mercury in soils and other environmental media, exposure among children was low and consistent with levels measured in national surveys and reference communities. The geometric mean (GM) blood lead level (BLL) (2.73 ug/dL) was higher than national averages, with 13% of children with BLLs above 5 ug/dL, indicating atypical sources of lead exposure. A second biomonitoring study was conducted approximately 26 months after the closure of the smelter and the implementation of several exposure reduction measures. This follow-up study included the collection of 119 blood samples and was designed to examine the impact of various environmental media, including outdoor soil, household dust, tap water and lead paint, on the BLLs of local children. Environmental samples were collected from the households of study participants, and the relationship between lead content in co-located environmental samples and children's BLLs was examined. The GM BLL was 1.41 ug/dL, representing a statistically significant reduction in BLLs between studies, with 2% of participants with BLLs greater than 5 ug/dL. Despite statistically significant relationships between BLLs and lead content in soil, household dust, and paint, the variability in BLLs was poorly explained by these factors alone (r2= 0.07, 0.12 and 0.06, respectively). BLLs were considered to be within the normative range and study results indicated additional intervention strategies were not likely to further influence BLLs in the community. These results have important implications on future assessment of risks associated with exposure to arsenic, lead, and inorganic mercury in soils and indicate that soil remediation or removal may not be warranted to reduce exposure.