250SOCs are generally toxic and can have substantial health impacts from both acute (short-term)
and chronic (long-term) exposure. Many are known carcinogens (cancer causing). EPA has set
Maximum Contaminant Levels (MCL) for 30 SOCs under the Safe Drinking Water Act. The Safe
Drinking Water Act requires that all water sources of all public water systems be periodically
monitored for regulated SOCs. The monitoring frequency can be adjusted through a waiver if
SOCs are not detected.EPA established Maximum Contaminant Levels (MCL), Maximum Contaminant Level Goals
(MCLG), monitoring requirements and best available technologies for removal for 65 chemical
contaminants over a five year period as EPA gathered and analyzed occurrence and health effects
data. This series of rules are known as the Chemical Phase Rules and they define regulations for
three contaminant groups:
Inorganic Chemicals (IOC),
Synthetic Organic Chemicals (SOC), and
Volatile Organic Chemicals (VOC).
The Chemical Phase rules provide public health protection through the reduction of chronic risks
from:
cancer;
organ damage; and
circulatory,
nervous, and
reproductive system disorders.
They also help to reduce the occurrence of Methemoglobinemia or "blue baby syndrome" from
ingestion of elevated levels of nitrate or nitrite.All public water systems must monitor for Nitrate and
Nitrite. Community water systems and Non-transient non-community water systems must also
monitor for IOCs, SOCs, and VOCs.
This is a list of the organic chemicals—which include pesticides, industrial chemicals, and
disinfection by-products—that are tested for in public water systems (those that provide water to
the public), along with the maximum standard for the contaminant, and a brief description of the
potential health effects associated with long-term consumption of elevated levels of the
contaminants.
The federal standard for most contaminants is listed as a Maximum Contaminant Level (MCL), the
lowest concentration at which that particular contaminant is believed to represent a potential health
concern. Unless otherwise noted, the MCL is expressed as parts per billion (ppb). Also, because
of technological limitations or other factors, it is not possible to test for some contaminants in a
reliable fashion. Instead, public water systems are required to use specific Treatment Techniques
(TT) that are designed to remove these particular contaminants from the water.
In addition to the chemicals listed, monitoring is done for approximately 60 organic chemicals for
which MCLs have not been established. If unacceptable levels are found of these “unregulated”
contaminants—based on established state health standards and an assessment of the risks they
pose—the response is the same as if an MCL has been exceeded: the public water system must
notify those served by the system.