EPA810-F-99-017
December 1999
Drinking Water Standards
& Health Effects
SAFE DRINKING WATER ACT • CELEBRATING 25 YEARS • PROTECT OUR HEALTH FROM SOURCE TO TAP
Drinking water standards are set by the U.S.
Environmental Protection Agency (USEPA) to
control the level of contaminants in the nation's
drinking water. The Safe Drinking Water Act
(SDWA) requires USEPA to set these standards,
which public water systems in the U.S. are "
required to meet. USEPA has set standards for
90 chemical, microbiological, radiological, and
physical contaminants in drinking water. Seven
of these are new standards which will be enforce-
able January 1, 2002. USEPA and others are
currently conducting research and collecting
information to determine which currently unregu-
lated contaminants pose the greatest public health
risk and will therefore be regulated in the future.
USEPA also sets Secondary Drinking Water
Regulations, which are non-enforceable guide-
lines 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 USEPA 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, busi-
nesses, campgrounds, and shopping malls are
served by public water systems).
Private Wells
The 10 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. USEPA 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/faq/
sco.html 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
USEPA sets for tap water. For information on
bottled water regulations, call the FDA at 1-800-
463-6332.
Steps in Drinking Water Standard Setting:
USEPA uses the following steps to set enforce-
able, health-based drinking water standards.
1. 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 subpopulations);
how easily the contaminant can be detected
in drinking water; whether technology exists
to remove it from drinking water; and the
likely impact of regulation on water systems,
public health, and the economy.
2. Set a Maximum Contaminant Level Goal
(MCLG) (the level of a contaminant in drink-
ing water below which 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 enforce-
able levels because they do not take available
technology into consideration, and therefore
are sometimes set at levels which public
water systems cannot meet.
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3. Propose an enforceable standard in the form of a
Maximum Contaminant Level (MCL) (the maximum
amount of a contaminant allowed in water deliv-
ered 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 tech-
niques 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, USEPA must complete an economic
analysis to determine whether the benefits of that
standard justify the costs. If not, USEPA 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."
USEPA may not adjust the MCL if the benefits
justify the costs to large systems and small systems
that are unlikely to receive variances.
4. USEPA sets an enforceable MCL or TT. After
considering comments on the proposed standard
and other relevant information, USEPA makes final
an enforceable Maximum Contaminant Level or
Treatment Technique, including required testing
and reporting schedules.
5. 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 USEPA 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 compli-
ance. 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 require USEPA to
establish every 5 years a list of contaminants which are
known or anticipated to occur in public water systems,
and may require future regulations under SDWA. In
establishing this contaminant candidate list USEPA has
divided the contaminants among those which are
priorities for additional research, those which need
additional occurrence data, and those that are priori-
ties for consideration in rulemaking. The list was
developed with significant input from the scientific
community and other interested parties. The next
steps for USEPA are to determine which contaminants
to address first in all categories, and to outline plans of
action for making regulatory decisions for five or more
contaminants by the year 2001.
In order to support this decision-making, USEPA has
also established a National Contaminant Occurrence
Database (NCOD), which stores data on the occur-
rence of both regulated and unregulated contaminants.
USEPA is also required to list and develop regulations
for monitoring certain unregulated contaminants. This
monitoring data will provide the basis for identifying
contaminants that may be placed on future Contaminant
Candidate Lists and support the USEPA Administrator's
decisions to regulate contaminants in the future.
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The Current Contaminant Candidate List and Next Steps
CCL
Regulatory
Determination
Priorities
20 contaminants
Research and
Occurrence
Priorities
40 contaminants
Actions/Next Steps
2001 Decision
Further Analysis
Research...
on health
15 contaminants
on treatment technologies
12 contaminants
on analytical methods
15 contaminants
Occurrence Data Collection
34 contaminants
Regulate
Don't Regulate
Other (Guidance)
Next CCL
(2003)
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 USEPA'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 a list of current drinking water standards, information on potential health effects of specific contami-
nants, and guidance to persons with severely compromised immune systems, see the USEPA web site at
http://www.epa.gov/safewater/dwhealth.html or call the Safe Drinking Water Hotline at 1-800-426-4791.
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