Disposing of gypsum waste is another challenge. Some scientists have proposed using the material as drywall filler or road base, but the EPA says it contains too much naturally occurring radioactivity and so forbids its use.

The Southern Environmental Law Center is suing the state of North Carolina over its approval of an 11,500-acre expansion of phosphate ore mining by PCS Phosphate in wetlands along the Pamlico River. Says staff attorney Geoff Gisler, "Eventually these mines will close down, and we will be dealing with the impacts for years."

This photo shows one area of a holding pond at a Lousiana fertilizer factory. The plant is one of many along an eighty-five-mile stretch of the Mississippi River known as the "chemical corridor."