Drinking Water Standards
I & Health Effects
SAFE DRINKING WATER ACT • 1974-2004 • PROTECT OUR HEALTH FROM SOURCE TO TAP
Drinking water standards are set by the U.S.
Environmental Protection Agency (US EPA) to control
the level of contaminants in the nation's drinking
water. The Safe
Drinking Water Act
(SDWA) requires US EPA
to set these standards,
which public water
systems in the U.S. are
required to meet. US
EPA has set standards
for 90 chemical,
microbiological,
radiological, and
physical contaminants
in drinking water. US
EPA and others are
currently conducting
research and
collecting information
to determine which
currently unregulated
contaminants pose the
greatest public health
risk and will therefore
be regulated in the
future.
US EPA also sets
Secondary Drinking
Water Regulations,
wh ich are non -
enforceable guidelines
for contaminants that
may cause cosmetic
effects (such as skin
and tooth discoloration)
or aesthetic effects
(such as taste or odor).
Water systems are not required by US EPA to adopt
these secondary standards, but states may choose to
adopt and enforce them.
Public Water Systems Must Meet
National Drinking Water Standards
Drinking water standards apply to public water
systems, which provide water to at least 15
connections or 25 persons at least 60 days out of
the year (most cities and towns, schools, businesses,
campgrounds, and shopping malls are served by
public water systems).
Private Wells
The 1 0 percent of Americans
whose water comes from private
wells (individual wells serving
fewer than 25 persons) are not
required to be protected by these
federal standards. People with
private wells are responsible
for making sure that their own
drinking water is safe. Some
states do set standards for private
wells, so well owners should
check their state requirements.
US EPA recommends testing
your water once per year to
see if it meets federal and state
standards. Call the Safe Drinking
Water Hotline at 1 -800-426-
4791 or see the Safewater home
page at www.epa.gov/safewater/
privatewells to find out how to get
a list of certified testing labs in
your state.
Bottled Water
Bottled water is regulated
by the U.S. Food and Drug
Administration as a food product,
and is required to meet standards
equivalent to those US EPA sets
for tap water.
Steps in Drinking Water
Standard Setting:
US EPA uses the following steps
to set enforceable, health-based drinking water
standards.
Determine whether a contaminant should be regulated
based on peer-reviewed science, including data on:
how often the contaminant occurs in the environment;
how humans are exposed to it; the health effects of
exposure, (particularly to vulnerable su bpopu lotions).
Set a Maximum Contaminant Level Goal (MCLG) (the
level of a contaminant in drinking water below which
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there is no known or expected health risk. MCLGs
allow for a margin of safety). These goals take into
account the risks of exposure for certain sensitive
populations, such as infants, the elderly, and persons
with compromised immune systems. These goals
are not enforceable levels because they do not take
available technology into consideration, and therefore
are sometimes set at levels which public water systems
can not meet.
Propose an enforceable standard in the form of a
Maximum Contaminant Level (MCL) (the maximum
amount of a contaminant allowed in water delivered
to a user of any public water system) or a Treatment
Technique (TT) (required procedure or level of
technological performance set when there is no
reliable method to measure a contaminant at very low
levels). MCLs are set as close to MCLGs as feasible,
considering available technology and cost. Examples
of rules requiring treatment techniques are the Surface
Water Treatment Rule (requires disinfection and
filtration) and the Lead and Copper Rule (requires
optimized corrosion control). Water samples that
contain lead or copper exceeding the action level
trigger additional treatment or other requirements
that a water system must follow. Required testing
(monitoring) schedules are part of the enforceable
standard.
After determining a proposed MCL or TT that is as
close to the MCLG as possible based on affordable
technology, US EPA must complete an economic
analysis to determine whether the benefits of that
standard justify the costs. If not, US EPA may adjust
the MCL for a particular class or group of systems to
a level that "maximizes health risk reduction benefits
at a cost that is justified by the benefits." US EPA may
not adjust the MCL if the benefits justify the costs to
large systems and small systems that are unlikely to
receve varances.
US EPA sets an enforceable MCL or TT. After
considering comments on the proposed standard and
other relevant information, US EPA makes final an
enforceable Maximum Contaminant Level or Treatment
Technique, including required testing and reporting
schedu les .
States are authorized to grant variances from
standards for systems serving up to 3,300 people
if the systems cannot afford to comply with a rule
(through treatment, an alternative source of water,
or other restructuring) and the systems install EPA
approved variance technology. States can grant
variances to systems serving 3,301 - 10,000 people
with US EPA approval. SDWA does not allow small
systems to have variances for microbial contaminants.
Under certain circumstances exemptions from
standards may be granted to allow extra time to seek
other compliance options or financial assistance. After
the exemption period expires, the public water system
must be in compliance. The terms of variances and
exemptions must ensure no unreasonable risk to public
health.
Determining Whether Standards Are
Needed for Other Contaminants - the
Contaminant Candidate List
The 1996 Amendments to SDWA requires that every
5 years US EPA establish a list of contaminants which
are known or anticipated to occur in public water
systems and may require future regluations under
SDWA. The list is developed with significant input from
the scientific community and other interested parties.
After establishing this contaminant candidate list,
US EPA identifies contaminants which are priorities
for additional research and data gathering. US EPA
uses this information to determine whether or not a
regulation is appropriate and this process is repeated
for each list, every 5 years.
In order to support this decision-making, US EPA
has also established a National Contaminant
Occurrence Database (NCOD), which stores data on
the occurrence of both regulated and unregulated
contaminants. US EPA is also required to list and
develop regulations for monitoring certain unregulated
contaminants. These monitoring data will provide the
basis for identifying contaminants that may be placed
on future Contaminant Candidate Lists and support
the US EPA Admin istrator's decisions to regulate
contaminants in the future.
Health Effects
Adverse health effects from contaminants that may
occur in drinking water include acute effects that may
immediately impact health and chronic effects that
may occur if contaminants are ingested at unsafe
levels over many years.
Drinking water that meets US EPA's health-based
standards is generally safe. People who are not
healthy as a result of illness, age, or weakened
immune systems, are more likely to be at risk from
certain contaminants that may be found in drinking
water. Infants and very young children are also
more susceptible to some contaminants. Individuals
concerned about their particular situations should
consult their health care providers.
For More Information
To learn more about dcurrent drinking water
standards, information on potential health effects of
specific contaminants, and guidance to persons with
severely compromised immune systems call the Safe
Drinking Water Hotline at 1-800-426-4791 or visit the
safewater web site at www.epa.gov/safewater.
Office of Water (4606)
www.epa.gov/safewater
EPA 816-F-04-037 June 2004
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