Water

Some of the toxic heavy metals "leach" from tailings ponds into nearby fields. Tailings from the milling of metal ores often contain traces of heavy metals, such as lead, mercury, cadmium, tin and arsenic.

As water or rainfall runs over tailings rivers, they poison the soil, and make water unfit for drinking, or crop irrigation. These "heavy metals" interfere with the body's enzyme reactions.

This processed waste material is much finer, and less densely packed than the parent rock. It creates a larger volume of waste, 20 - 40% more. Environmental problems of waste disposal increase, particularly the dispersal of small particles into the atmosphere.

Natural weathering can release heavy metals into the environment. Mining and its associated processes cause artificially high levels.
After the ore has been extracted, milled and separated, it is ready for smelting. This process produces metals by heating their ores.