The influence of lead content in drinking water, household dust, soil, and paint on blood lead levels of children in Flin Flon, Manitoba and Creighton, Saskatchewan.

Lead exposure continues to be an important health issue despite the general removal of lead sources in commercial and industrial applications. Low levels of lead exposure have been found to produce adverse neurodevelopmental effects in children with no evidence that a threshold exists for this critical endpoint. Blood lead levels (BLLs) were measured in children (n=118) under the age of 7years in the northern Canadian smelter community of Flin Flon, Manitoba and Creighton, Saskatchewan. An environmental sampling component was included to examine the relationship between lead content in outdoor soil, household dust, tap water, and paint within a given household and the corresponding BLLs in participating children. The geometric mean (GM) BLL for study participants was 1.41µg/dL. Blood lead levels varied slightly by age category with the lowest levels found among the children under age 2 (GM=1.11µg/dL) and the highest levels found among children between 2 and 3years of age (GM=1.98µg/dL). Results from the multivariate modeling indicated that BLLs had a significant positive association with the age of housing (p<0.05), with children living in households constructed prior to 1945 being more likely to have higher levels (p=0.034). Outdoor soil (GM=74.7µg/g), household dust from kitchen floors (GM=1.34µg/ft2), and maximum household lead paint were found to be significantly correlated (p<0.05) to BLLs. Although a statistically significant association between concentrations of lead in these household media and the corresponding BLLs exists, the variability in BLLs was poorly explained by these factors alone (r2=0.07, 0.12 and 0.06 for soil, household dust, and paint, respectively). Lead concentrations in flushed (GM=0.89µg/L) and stagnant (GM=2.07µg/L and 1.18µg/L) tap water samples were not significantly correlated (p>0.05) to BLLs.

The bioaccessibility of soil-based mercury as determined by physiological based extraction tests and human biomonitoring in children.

Environmental contaminants associated with soil particles are generally less bioavailable than contaminants associated with other exposure media where chemicals are often found in more soluble forms. In vitro methods, such as Physiological Based Extraction Tests (PBET), can provide estimates of bioaccessibility for soil-based contaminants. The results of these tests can be used to predict exposure to contaminants from soil ingestion pathways within human health risk assessment (HHRA). In the current investigation, an HHRA was conducted to examine the risks associated with elevated concentrations of mercury in soils in the northern Canadian smelter community of Flin Flon, Manitoba. A PBET was completed for residential soils and indicated mean bioaccessibilities of 1.2% and 3.0% for total mercury using gastric phase and gastric+intestinal phase methodologies, respectively. However, as many regulators only allow for the consideration of in vitro results for lead and arsenic in the HHRA process, in vitro bioaccessibility results for mercury were not utilized in the current HHRA. Based on the need to assume 100% bioaccessibility for inorganic mercury in soil, results from the HHRA indicated the need for further assessment of exposure and risk. A biomonitoring study was undertaken for children between 2 and 15 years of age in the community to examine urinary inorganic mercury concentrations. Overall, 375 children provided valid urine samples for analysis. Approximately 50% of urine samples had concentrations of urinary inorganic mercury below the limit of detection (0.1 µg/L), with an average creatinine adjusted concentration of 0.11 µg/g. Despite high variability in mercury soil concentrations within sub-communities, soil concentrations did not appear to influence urinary mercury concentrations. The results of the current investigation indicate that mercury bioaccessibility in residential soils in the Flin Flon area was likely limited and that HHRA estimates would have been better approximated through inclusion of the in vitro study results.