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What is Perchlorate?

Recently, the California Department of Public Health (CDPH) found perchlorate in a number of drinking water sources in California. Perchlorate is an inorganic chemical derived from ammonium perchlorate, which is used in the manufacture of solid rocket propellants and explosives.

Because perchlorate historically has not been considered a common contaminant, no federal or state drinking water standards exist. However, the CDPH has adopted a provisional action level for perchlorate in drinking water of 18 micrograms per liter, or parts per billion (ppb). The primary human health concern related to perchlorate is that it can interfere with the thyroid gland's ability to utilize iodine to produce thyroid hormones. Perchlorate in very high doses has been used in medicine in the treatment of Graves' disease, a condition in which excessive amounts of thyroid hormone are produced.

Although perchlorate contamination of local water supply sources is not considered likely, factors such as the widespread use of the material in defense/aerospace activities and the detection of perchlorate in other areas of California prompted San Jose Water Company to conduct additional monitoring in our service area. Monitoring completed in January 1998 confirmed that perchlorate is not present in any of our water supplies.

Additional information on perchlorate is available on the CDPH Website at: