EPA: Perchlorate, MTBE Require Further Study

05/11/2007

In April 2007, the US EPA made a preliminary determination not to regulate 11 of the 51 contaminants on the second drinking water contaminant candidate list (CCL 2). The Safe Drinking Water Act requires regulatory determination of at least five contaminants from the most recent CCL every five years.

US EPA stated that additional information may be needed to more fully characterize perchlorate exposure, and that the health risk assessment of MTBE has not been finalized. The agency provided a summary of current health, occurrence, and exposure information, and it is seeking comment and additional information to determine if regulation of these chemicals in drinking water would reduce risks to human health.

US EPA has found that the following contaminants do not occur at levels of public health concern in public water systems and, therefore, will not be regulated:

• boron
• dacthal mono-acid degradates
• dacthal di-acid degradates
• 2,4-dinitrotoluene
• 2,6-dinitrotoluene
• fonofos
• s-ethyl propyl thiocarbamate (EPTC)
• terbacil
• 1,1-dichloro-2,2-bis(p-chlorophenyl)- ethylene (DDE)
• 1,3-dichloropropene (Telone)
• 1,1,2,2-tetrachloroethane

These findings were published in the May 1, 2007 Federal Register. US EPA will take comments for 60 days with final determinations expected in 2008. For complete information, please visit www.epa.gov/safewater/ccl/index.html.