Perchlorate is soluble in water and persists in soils and water for long periods. It is biologically active at relatively low-levels in the environment, and its role as an endocrine-disrupting chemical has been well characterized in some amphibians and fish. Uptake by plants and microbial degradation has also been established. Known or suspected health effects include thyroid dysfunction and interferences with brain development. There are currently no national aquatic, drinking water, or consumptive standards for perchlorate, although eight States have set advisory standards ranging from 1-18 ppb. U.S. Environmental Protection Agency has proposed a drinking water limit of 1 ppb in 2002. Subsequent review by the National Academy of Sciences resulted in a recommendation that the human health exposure be increased about 20 times the initial level proposed by the U.S. Environmental Protection Agency.
Although perchlorate has been documented as a point-source contaminant in groundwater near areas where ammonium perchlorate is produced and where solid-fuel rockets, fireworks, and other explosives are manufactured or used, recent studies have found perchlorate in areas with no apparent anthropogenic sources and in areas where agricultural activities (fertilizers and irrigation) are prevalent. Recent small-scale studies have documented perchlorate in potash-bearing soils, evaporitic materials, some naturally-occurring fertilizers, fish and invertebrates. It has been suggested that perchlorate may accumulate in areas with low precipitation (deserts). The identification of perchlorate in sodium nitrate fertilizers derived from Chilean caliche may support this suggestion. Thus there was a need to obtain information on the occurrence of perchlorate areas not impacted by the manufacture and use of explosives and rocket fuel.
This web site documents a reconnaissance study by the U.S. Geological Survey that was conducted in 2004 to determine the occurrence of perchlorate in shallow groundwater and in streams and rivers in the Central and Southwestern United States