According to the US EPA, Arizona mines are once again Arizona's biggest polluters. Each year, the EPA releases it's Toxic Release Inventory (TRI) data for each state. This inventory, required by law since 1987, tallies pollution released into our air, water, and ground. These releases are not verified independently and come form the companies themselves, so the figures are probably conservative.
For 2008, 7 out of the top 10 polluters in Arizona are mines. The report shows that toxic release in Arizona increased by 7% in 2008 while the national average dropped 6%. The Arizona figures do not include billions of pounds of tailings that Congress exempted from the reporting requirements.