Occasionally water utilities, DOHS or EPA find new contaminants that are present in groundwater or surface waters due to improved chemical detection methods or new information on potential contaminant sources. Many water utilities are on the leading edge of research to identify new contaminants. Two such contaminants recently found to be of concern include perchlorate and NDMA.

Perchlorate
Perchlorate is an inorganic compound used as an oxidizing agent in solid rocket fuel. In 1997, concern about the potential for perchlorate contamination in drinking water wells prompted DOHS and utilities to monitor for perchlorate near aerospace facilities or other potential sources of contamination. DOHS investigated drinking water supplies near aerospace, munitions, and fireworks facilities throughout the state. The primary health concern related to perchlorate is its potential to interfere with the thyroid gland's ability to utilize iodine to produce thyroid hormones. Based on the potential health effects in drinking water, DOHS established an Action Level for perchlorate at 18 micrograms per liter.

Further information on perchlorate in California can be found at http://www.dhs.cahwnet.gov/ps/ddwem/chemicals/perchl/perchl_overview.htm.

NDMA
N-nitrosodimethylamine (NDMA) is used in many ways, including a use as a research chemical. It was formerly used as an intermediate chemical in the production of liquid rocket fuel. In 1998, concern about the potential for NDMA contamination prompted utilities to sample for the chemical. A limited number of drinking water wells located near hazardous waste sites or rocket fuel generation and storage sites have detected NDMA in the groundwater. Because NDMA is classified as a probable human carcinogen, in April 1998, DOHS established an Action Level for NDMA at 0.002 micrograms per liter. However, no validated analytical technology exists to detect NDMA levels down to 0.002 micrograms per liter. DOHS recommends utilities detecting any level of NDMA remove the source from service immediately.

Further information on NDMA in California can be found at http://www.dhs.cahwnet.gov/ps/ddwem/chemicals/NDMA/NDMAindex.htm.

Other Contaminants
The EPA and the DOHS are continuously evaluating new information for the potential regulation of emerging contaminants. There is a long list (up to 200) of unregulated contaminants that water utilities routinely monitor. The purpose of this monitoring is to help the regulatory agencies track the occurrence of (or lack of) contaminants in drinking water. When occurrences begin to be detected, the EPA and DOHS begin the process to regulate these chemicals to reduce exposure to the public.

CWA will continue to update you on important information pertaining to new contaminant levels. In a recent development, the DOHS adopted a secondary maximum contaminant level for Methyl Tertiary-Butyl Ether (MTBE). This substance is used in gasoline to promote more complete combustion and reduce exhaust emissions. Over the past several years, this substance has been detected in ground water and surface water in California and throughout the United States. Until a primary MCL is adopted, the DOHS will use its 13-ppb advisory action level to protect against health risks associated with exposures to MTBE in drinking water.