Use of lead isotope ratios to identify sources of lead exposure in Alaska Natives

Abstract

Objectives. Although banned nationwide for waterfowl hunting, lead shot is still used for hunting in regions of Alaska. Consumption of birds hunted with lead shot may be a route of human lead exposure in susceptible populations. The Centers for Disease Control and Prevention (CDC) and Alaskan health officials conducted a cross-sectional exposure assessment and used isotope ratios (IR) to test that assumption. Study Design. Cross-sectional exposure assessment study. Methods. We compared isotopic profiles of blood lead in Alaska Native women from Bethel (n=10) and Barrow (n=10) to lead shot samples purchased from the respective regions. To evaluate the source of lead for the buckshot, we evaluated IR profiles for lead mineral and ore from a smelter in Torreon, Mexico, a suspected source of origin for the lead. Results. The lead IRs for the blood lead differed significantly from the lead shot IRs (p< 0.001); thus, lead shot is unlikely to be the sole source of lead exposure of public health significance in participants of this study. Overlap in IRs for the lead shot and blood lead existed for 6 (30%) of the women from Bethel and Barrow; however, no correlation was noted between lead levels and the IRs for the blood lead. IR profiles for lead mineral and ore from Mexico were substantially different from the IRs of lead shot from Alaska, confirming that buckshot in this study is unlikely to originate from the Mexican smelter. Conclusions. Lead shot from the manufacturer in this study does not appear to be the sole source of lead exposure in most participants; nonetheless, lead shot could yet be a potential source of exposure in some populations, possibly those whose diet consists of game hunted with lead shot.

Biological Fractionation of Lead Isotopes in Sprague-Dawley Rats Lead Poisoned via the Respiratory Tract

“…Patel et al [4] reported that there was no correlation between lead levels and the isotope ratios for the lead from blood of Alaska Natives. Moreover, there are no other published reports that show a relationship between the blood lead concentration and the blood lead isotope ratios.…”

“…When lead is extracted from its ore, its isotopic composition was frozen at the time [3]. The comparative abundance of the four natural isotopes is characteristic for different lead sources and the isotope ratios can serve as a ‘fingerprint’ of the lead from that source [2], [4], [5]. As Cheng and Hu [5] reported that lead undergoes a minimal mass-dependant isotope fractionation in natural physical, chemical, and biological processes due to its large atomic weight.…”

Sources of exposure to lead in Arctic and subarctic regions: a scoping review

“…Conversely, in the more southern location of Hamilton, Ontario, the majority of lead isotope ratios in humans were similar to the ratios in lichen (atmospheric exposure) [ 167 ]. However, Indigenous women in Alaska had lead isotope ratios that were not similar to lead ammunition [ 45 ].…”

Identifying the origin of lead poisoning in white-backed vulture (Gyps africanus) chicks at an important South African breeding colony: a stable lead isotope approach

“…Furthermore, as Pb is a heavy element, the fractional mass differences between its different isotopes are small, resulting in minimal fractionation during biological and industrial processes (Cheng and Hu 2010). Consequently, distinct isotope ratios could be associated with many anthropogenic sources of Pb, providing a powerful tool for inferring the origin of Pb in a tissue sample (Patel et al 2008). Should the isotopic compositions of multiple Pb sources vary, these differences will be evident in the isotopic composition of tissue Pb, providing opportunities to accurately link blood Pb and its potential source(s) (Patel et al 2008).…”