Identification of environmental sources of lead exposure in Nunavut (Canada) using stable isotope analyses.

BACKGROUND

Blood lead levels (BLLs) were measured in the adult Inuit population of Nunavut, Northern Canada, during the Inuit Health Survey (IHS) in 2007-2008. Approximately 10% of the adult participants had BLL over the Health Canada's guidance of 100μg/L.

OBJECTIVES

1. To repeat the measurement of BLL among the IHS participants with high BLL and household members including pregnant women and children under 10years of age; 2) to measure lead (Pb) concentrations in environmental samples to identify potential sources and 3) to explore how Pb from environmental samples contributes to BLL using Pb stable isotopic analyses.

METHODS

Blood samples were collected from 100 adults and 56 children in 2012. A total of 169 environmental samples (tap water, house dust, paint, country food, soil, and ammunition) were collected from 14 houses from three communities where the IHS participants had the highest BLL. Total Pb concentrations and Pb isotope mass balance were determined by inductively coupled plasma-mass spectrometry (ICP-MS).

RESULTS

The geometric mean of BLL was 43.1μg/L; BLL increased with age and was higher in adults than children (71.1 vs. 17.5μg/L). Median Pb concentrations in water (1.9μg/L) and dust (27.1μg/m(2) for wiped dust, 32.6mg/kg for vacuum dust coarse fraction, and 141.9mg/kg for vacuum dust fine fraction) were generally higher than in other parts of Canada. Median Pb concentrations of food and soil coarse and fine fractions were low (36.6μg/kg, 5.4mg/kg and 11.8mg/kg respectively); paint chips exceeded the Canadian guidelines in two houses (median: 3.8mg/kg). Discriminant analyses and isotope ratio analyses showed that ammunition and house dust are major sources of Pb in this study population.

CONCLUSION

Analyses of Pb stable isotopes are useful to identify the routes of exposure to Pb. This approach can contribute to develop targeted public health programmes to prevent Pb exposure.