What it is:

  • Perchlorate (ClO4) is both a natural product and a synthetic chemical with numerous uses including in rocket fuel, fireworks, flares and explosives. It is also present in some fertilizers.
  • It was once used as pharmaceutical to treat Grave’s disease (hyperthyroidism).
  • Perchloric acid (HClO4) forms salts such as potassium perchlorate (KClO4), ammonium perchlorate (NH4ClO4) and sodium perchlorate (NaClO4).

Occurrence:

  • Perchlorate is found naturally in subsurface soil, especially in the southwest U.S. and in deposits in Chile, and in water sources.
  • Perchlorate has been found in just over 4 percent of public water systems in the U.S. It was sampled as part of the Unregulated Contaminant Monitoring Regulation 1 (UCMR 1) program.
  • The chemical contaminates soil and groundwater around some military bases and aerospace and defense plants.

Health effects:

  • At sufficiently high doses, perchlorate can interfere with iodide uptake by the thyroid gland, reducing thyroid hormone production and interfering with normal growth and metabolism.
  • A 2005 National Academy of Sciences (NAS) review recommended a perchlorate reference dose (RfD) of 0.7 micrograms per kilogram of body weight per day from a NOEL of 7 micrograms per kilogram per day. It was based upon uptake of radioactive iodine which is not an adverse effect per se; serum hormone levels were not significantly altered at the NOEL. The U.S. Food and Drug Administration (FDA) estimated lowest intake levels at 0.08 to 0.11 µg/kg/day for 25 to 30-year-old men and highest intakes at 0.35 to 0.39 µg/kg/day for two year olds. It concluded that no adverse health effects were expected at those levels. The American Thyroid Association reported that there were no effects on thyroid function for women in early pregnancy at typical environmental exposures even for mildly iodine deficient individuals.

Regulation:

  • The U.S. Environmental Protection Agency (EPA) has decided to regulate perchlorate under the Safe Drinking Water Act (SDWA). This decision reverses a 2008 preliminary determination.

Water treatment:

  • NSF/ANSI Standard 58 requires an reverse osmosis (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.
  • In addition to RO, ion (anion) exchange, carbon adsorption and possibly distillation will reduce perchlorate.

Sources: Agency for Toxic Substances and Disease Registry, American Thyroid Association, Joint FAO/WHO Expert Committee on Food Additives, NSF International, U.S. Environmental Protection Agency, U.S. Food and Drug Administration, U.S. Geological Survey.