What it is:

• Inorganic anion with one chlorine atom and four oxygen atoms; electrical charge of minus 1. Chemical symbol: ClO4-
• Forms salts such as potassium perchlorate (KClO4), ammonium perchlorate (NH4ClO4), sodium perchlorate (NaClO4). Also in perchloric acid (HClO4). Most salts are soluble in water.
• Powerful oxidizer.

Occurrence:

• Found naturally in subsurface soil, especially in southwest US and in deposits in Chile, and in water sources.
• Manufactured for a variety of industrial processes and products. Most common is NH4ClO4, an oxidizer in explosives, fireworks, matches, vehicle airbags and solid rocket fuel.
• Contaminates soil and groundwater around some military bases and aerospace and defense plants.
• Has been detected by US Environmental Protection Agency (EPA) in public water supplies in at least 26 states and two territories. Also in food.

Health Effects:

• In high concentrations, can interfere with iodide uptake by the thyroid gland, reducing thyroid hormone production and interfering with normal growth and metabolism.
• 2005 National Academy of Sciences (NAS) review recommended a perchlorate reference dose (RfD) of 0.7 micrograms per kilogram of body weight per day. US Food and Drug Administration (FDA) has found most people consume less than the RfD.

Regulation:

• Not regulated by EPA as a drinking water contaminant, but is on EPA’s Contaminant Candidate List. EPA has issued interim health advisory level of 15 ppb of perchlorate in drinking water. Also recommends that people who prepare infant formula with water containing more than 15 ppb use water that is lower in perchlorate. EPA will look at further studies of perchlorate.
• New enforceable maximum limits for perchlorate in public water in two states: California, 6 ppb; Massachusetts, 2 ppb.

Water treatment:

• NSF/ANSI Standard 58 requires an RO unit to be able to reduce water containing 130 ppb of perchlorate to 4 ppb or less. Additional industry standards for other devices are under consideration. Products certified for perchlorate reduction found at: www.nsf.org.
• In addition to RO, ion (anion) exchange, carbon adsorption and possibly distillation will reduce perchlorate.