Environmental disaster is a disaster that is due to human activities and some of the most publicized environmental disasters are associated with the mining industry. These disasters are attributed to both natural and mining-related causes. Acid drainage, for example, formed by rainwater or snowmelt in contact with mineral deposits can damage nearby ecosystems by polluting streams and destroying wildlife. The mining and processing of ores, however, may accentuate and accelerate the natural processes. On a long-term basis, mining can increase the acidity of water in streams; cause increased sediment loads, some of which may be metal-laden, in drainage basins; initiate dust with windborne pathogens; and cause the release of toxic chemicals, some contained in exposed ore bodies and waste rock piles and some derived from ore-processing reactions. Contaminants containing such toxic chemicals as cyanide and lead may be transported far from a mining site by water or wind, polluting soils, groundwater, rivers, and the atmosphere.