There are three major sources of air pollution:
Fumes from Smelters: The worst source of problems for possible damage to lungs is from smelter fumes; therefore, smelters are regulated and have to have environmental equipment installed. However, the equipment has to be maintained and in operation. In a case in the mid-1990's in Green Valley, AZ, at the Cyprus Duval facility, the roasters were kept running while the environmental equipment was turned off for cleaning.
Moral: Don't put tailing impoundment were it's windy!
Articles that discuss ways to reduce dust at tailings ponds:
Pond for growing algae to apply to tailings to prevent dust—Phelps Dodge Sierrita