Health Risk Assessment of the Mount Isa Population from Lead Exposure

摘要

The Lead Pathway Air Study (2007-2012) provides an understanding of sources of lead and human exposure at Mount Isa. The project carried out hazard assessment, exposure assessment and health risk assessment of lead by utilizing the Australian risk assessment framework. Potential exposure routes of lead getting into the human body are via two routes: ingestion through the mouth to the digestive system; and inhalation through the mouth and nose into the lungs; absorption through the skin is insignificant. Lead particle size in the environment and chemical form are critical factors. Thus, inhalation is shown to be <5 % of the total exposure for people living in Mount Isa, while ingestion is >95 %. Extensive dust/soils sampling of mining/smelting origins and residential area provided physico-chemical characteristics of samples including Synchrotron-based X-ray absorption spectroscopy (XAS) method for lead speciation/composition data and high resolution lead isotope measurements to understanding complexity of multiple sources including past and present, natural and anthropogenic inputs. The study indicates that PM10 air particulates exiting from the Mount Isa smelter stacks were not the major sources of lead exposure via inhalation in the Mount Isa city area at the times the samples were taken. The major source is via ingestion of air particulates (<250 ?m diameter) from ground deposition as fallout. This conclusion is based on lead isotope ratios showing a clear fingerprint of lead originating from the Urquhart Shale on the mine site and outcrops in the city area. Copper smelter stack samples have a distinct fingerprint, not visible in samples obtained from the city during this study. Lead isotope ratios can show origin of lead in air particulates and dusts regardless of chemical or mineral form while XAS analysis gives the chemical form. XAS can show differences even when lead isotope ratios are the same.