The Environmental Protection Agency said that mining giant Xstrata is operating within the regulatory requirements, even though its Mount Isa facilities are among the nation's largest polluters.

The National Pollutant Inventory this week has identified the north west Queensland operations as being the top emitter of seven substances, including lead and sulfur dioxide.

Mr David Wainwright of EPA's said that the data is an estimate of what is released from the mine's smoke stacks and is not a surprise. He said that "The actual levels don't bear a relationship to what actually people are being exposed to in the community there.”

He added that "There's the process of dilution and dispersion after those substances get emitted from the stacks and it's really the monitoring that takes place on the ground that gives an indication of what the air quality is."