19 – Mining and the Lake Eyre Basin environment 179 copper grades have also declined, even though steady until 2003 (Fig. 19.5). The Mount Isa field has had significant historical pollution problems with lead and heavy metals, particularly via airborne dispersion of smelter emissions and dusts. There are ongoing issues affecting public health, especially blood lead levels in children (Munksgaard et al. 2010 Taylor et al. 2010). Although the lead and copper smelters were to close in 2016, they were recently extended to ~2020, with expansion plans involving two major open cut mines (lead–zinc– silver and copper). These would require the relocation of all milling and smelting plants and Fig. 19.4. Mount Isa mining complex, one of the world’s largest mines for production of base metals, showing the extent of industrial infrastructure, including the copper and lead smelters, and an open cut mine in the background (photo, R. T. Kingsford). Table 19.2. Cumulative production (1931–2014) and available mineral resource (2014) from the Mount Isa field (updated from Mudd 2009). Resources Ore mass (Mt) Metal Ore grade Metal mass Cumulative production 218.7 Lead 5.4% 8.72 Mt Zinc 6.6% 9.88 Mt Silver 129 g/t 20.3 kt 269.9 Coppera 3.2% 8.09 Mt Available resource 704.3 Lead 3.0% 21.4 Mt Zinc 5.2% 36.7 Mt Silver 59 g/t 41.4 kt 352.2 Copper 1.4% 4.87 Mt a Includes at least 41.4 t silver