The Environmental Protection Agency is researching and evaluating a list of 51 unregulated, new or emerging drinking water contaminants for possible regulation.
The 1996 Amendments to the Safe Drinking Water Act (SDWA) created a Contaminant Candidate List (CCL) process to determine if new regulations were needed to protect drinking water safety. The SDWA directs EPA to periodically publish a list of contaminants that “at the time of publication, are not subject to any proposed or promulgated national primary drinking water regulation, which are known or anticipated to occur in public water systems, and which may require regulation.”
EPA said the latest list consists of unregulated contaminants that are known or anticipated to occur in drinking water. The SDWA requires EPA to conduct extensive research into the occurrence and health effects of the listed contaminants before issuing new regulations or standards.
The latest CCL, EPA’s second, carries over a number of contaminants from the first CCL. In July 2003, EPA removed nine contaminants from the first CCL after it concluded that the data justified that action.
EPA also reported on its efforts to improve the CCL selection process. It said it is considering more contaminants for inclusion in the third CCL and plans a more transparent system for selecting contaminants.
The agency said that “approach will produce a more comprehensive CCL because the process will address a wider range of information and screen contaminants more systematically, as was recommended by the National Academy of Sciences and the National Drinking Water Advisory Council.”
More information on the Contaminant Candidate List may be found at: www.epa.gov/safewater/ccl/ccl2_list.html
EPA Sets Reference Dose for Perchlorate
Also in February, EPA established an official reference dose (RfD) of 0.0007 mg/kg/day of perchlorate, exposure to which can block iodide uptake to the thyroid gland.
Perchlorate has been used in rocket propellants, munitions, fireworks, flares, auto airbags and pharmaceuticals. It may also occur naturally. Perchlorate has been detected in drinking water in some systems around the country, as well as in certain foods.
EPA said its RfD is consistent with the recommended reference dose in a January 2005 National Academy of Sciences report. A reference dose is a scientific estimate of a daily exposure level that is not expected to cause adverse health effects in humans.
The agency said its reference dose, which assumes total intake from both water and food sources, protects all populations, including the most sensitive subgroups.
EPA said the new RfD translates to a drinking water equivalent level (DWEL) of 24.5 ppb. A DWEL, which assumes that all of a contaminant comes from drinking water, is the concentration of a contaminant in drinking water that will have no adverse effect with a margin of safety. EPA said because there is a margin of safety built into the RfD and the DWEL, exposures above the DWEL are not necessarily considered unsafe.
Meanwhile, AWWA released a study that found perchlorate in drinking water in 26 states and Puerto Rico, but most of the detections were at levels below 12 micrograms per liter (ug/l).
Tom Curtis, AWWA’s deputy executive director, said, “As more sensitive analytical methods are developed, perchlorate detection is likely to increase.”
AWWA said most of the detections were not associated with EPA-identified releases of perchlorate.
It said perchlorate was found in 5% of the nation’s large community water systems. The highest density was found in Southern California, west central Texas, along the East Coast between New Jersey and Long Island, and in Massachusetts.
