Windblown lead carbonate as the main source of lead in blood of children from a seaside community: an example of local birds as "canaries in the mine".

In late 2006, the seaside community in Esperance, Western Australia, was alerted to thousands of native bird species dying. The source of the lead was thought to derive from the handling of Pb carbonate concentrate from the Magellan mine through the port of Esperance, begun in July 2005. Concern was expressed for the impact of this process on the community. This study was designed to evaluate the source of Pb in blood of a random sample of the community using Pb isotope ratios. The cohort comprised 49 children (48 < 5 years of age) along with 18 adults (> 20 years of age) with a bias toward higher blood lead (PbB) values to facilitate source identification. Mean PbB level of the children was 7.5 microg/dL (range, 1.5-25.7 microg/dL; n = 49; geometric mean, 6.6 microg/dL), with four children whose PbB was > 12 microg/dL. The isotopic data for blood samples lay around two distinct arrays. The blood of all children analyzed for Pb isotopes contained a contribution of Pb from the Magellan mine, which for young children ranged from 27% up to 93% (mean, 64%; median, 71%). Subtraction of the ore component gave a mean background PbB of 2.3 mug/dL. Several children whose PbB was > 9 microg/dL and most of the older subjects have complex sources of Pb. The death of the birds acted as a sentinel event; otherwise, the exposure of the community, arising from such a toxic form of Pb, could have been tragic. Isotopic data and mineralogic and particle size analyses indicate that, apart from the recognized pathway of Pb exposure by hand-to-mouth activity in children, the inhalation pathway could have been a significant contributor to PbB for some of the very young children and in some parents.