Mount Isa: Lead contamination from mines

Macquarie University research reveals there is unequivocal evidence that the environmental lead source at Mount Isa, Queensland, is derived from the mining and smelting activities.

The research findings have important and significant implications for current and future residents of Mount Isa – particularly for children under age five. The research demonstrates that the current educational advice given to Mount Isa residents to minimise their exposure to environmental lead by reducing dust in the home environment is inadequate because it does not address the primary cause and source of the problem – the mining and smelting operations.

The research found that surface soils within 2km of the mining operations were significantly enriched with cadmium, copper, lead and zinc compared to sites at greater distances. The researchers tested their hypothesis that the Xstrata Mount Isa Mines operations had caused surface contamination by examining soil profiles in and around Mount Isa. These investigations confirmed that it was only the top few centimetres of soil that were enriched with metals. At depths of 10-20 cm, soil metals were close to normal concentrations. The study also demonstrated that surface lead and copper concentrations were highly correlated, indicating that they must have a common source of origin.

Previously, Xstrata Mount Mines and various Queensland Government agencies have contended that the primary source of contaminated urban soils was a result of natural mineralisation effects from local geology. However, the study shows that elevated copper concentrations associated with the surface soils cannot be derived from the copper orebody, which is found at a minimum of ~240 m below the surface.

These facts reveal that the surface enrichment of soils with both lead and copper can only have been derived from atmospheric emissions from Xstrata Mount Isa Mines.