Why is perchlorate a problem?


Perchlorate is a negatively charged ion, or anion, that consists of one chlorine atom and four oxygen atoms (ClO4-).   This anion is commonly associated with the solid salts of ammonium, potassium, and sodium perchlorate. Perchlorate is a very strong oxidizing agent and its salts are manufactured for use in a variety of applications including solid rocket propellant, pyrotechnics, blasting agents, matches, lubricating oils, textile dye fixing, automobile air bag inflators, paint and enamel production, and even pharmaceuticals. 
Perchlorate salts are highly soluble in water and can be very mobile in surface water and groundwater.  Perchlorate is relatively inert under typical groundwater and surface water conditions and as a result, may persist for extended periods of time without treatment.  This is a potential health concern because perchlorate interferes with iodide uptake by the thyroid gland.  If perchlorate is consumed in sufficient quantity, this inhibition may affect growth hormone production and metabolism in children and adults. 
From 2001 to 2005, the Environmental Protection Agency (EPA) collected perchlorate data from 3,865 public water supplies as part of the Unregulated Contaminant Monitoring Regulation 1 (UCMR 1) program.  Perchlorate was found in just over 4 % of public water systems evaluated in 26 states. 
Currently, there is no Federal drinking water standard established for perchlorate.  In February 2005, EPA established an official reference dose of 0.0007 milligrams of perchlorate per kilogram of body weight per day.  This reference dose translates to a Drinking Water Equivalent Level (DWEL) of 24.5 ppb and this concentration was identified by EPA as a preliminary remediation goal.  A DWEL assessment assumes that all of a contaminant comes from drinking water.  Additional studies indicate that perchlorate exposure may occur from sources other than drinking water.  As a result, in January 2009, EPA revised the preliminary remediation goal by issuing an interim health advisory of 15 ppb in drinking water.
Some States have established drinking water standards for perchlorate.   For example, the State of California established a maximum contaminant level (MCL) of 6 ppb, effective October 2007.   Thus, drinking water wells in California with perchlorate present at or above this regulatory limit are shut down until a treatment solution is implemented. ARA has been developing perchlorate contamination cleanup solutions since 1990.

Additional information describing perchlorate characteristics, occurrence, and regulation can be found using the following online resources.