Globally, metal mining is one of the biggest sources of air pollution.

These toxins are harmful to workers and local communities. Exposure to mercury, for example, can result in illnesses ranging from impaired vision and muscle weakness to permanent kidney and nerve damage, depending on the level of exposure. Arsenic is a carcinogen. And high zinc exposure can lead to conditions such as anemia and metal fume fever - 
http://nodirtygold.earthworksaction.org/impacts/air#.VJbC2l4AIA