March 2001: Volume 43, Number 3
Monitoring Public Water Supplies
by Kelly A. Reynolds, MSPH, Ph.D.
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In 1998, there were 168,690 public water systems supplying water to 275
million consumers in the United States. In general, the public water supply is considered
safe, with 80 percent of public systems reporting no violation of U.S. Environmental
Protection Agency (USEPA) water quality standards. Twenty percent, however, reported
a violation of some kind. The majority are by and large small systems serving less than
10,000 people. The most common violation was the failure to monitor for a specific
contaminant. Although not solely a health-based violation, the lack of monitoring means
it’s unknown if a health-based violation occurred. Six percent of all utilities reported a
The impact of such violations is difficult to assess since factor risks are highly variable
from one community to another, depending largely on the type of violation (tardy testing
or reporting vs. a discrepancy in following water treatment protocols) as well as the
number and susceptibility of persons exposed. What is known is that the greatest number
of health-based violations occur due to chronic coliform bacteria. Coliform bacteria are
commonly present in the environment, but their presence in drinking water suggests that
inadequate treatment has taken place. The most recent information estimates that greater
than 7 million people become ill and more than 1,000 die each year from disease-causing
microbes in drinking water.(1)
The following is a review of past violations of public water systems throughout the
United States. In addition, information is given to stay informed regarding the quality of
water supplied by public systems in a specific area.
State and national regulations
Under the Safe Drinking Water Act (SDWA), the USEPA is responsible for regulating
public water systems serving at least 25 people. Each state is responsible for the
supervision of water systems within its borders based on USEPA-set national limits for a
variety of contaminants and treatment requirements. Each state is required to send
quarterly reports to the USEPA for review and analysis. The quarterly informational
reports, comprised of more than 16 million computer records, are then compiled into the
Safe Drinking Water Information System (SDWIS), which is then available to the public
(see www.epa.gov/OGWDW/sdwisfed/sdwis.htm). This information is fed into the
National Contaminant Occurrence Database (NCOD), developed to satisfy statutory
requirements set by Congress in the 1996 SDWA amendments. Fifty-six states,
commonwealths and territories are required to prepare compliance reports, including
American Samoa, Guam and the Northern Mariana Islands. The USEPA also prepares
reports for states and Native American tribes that don’t have primary enforcement
responsibility for drinking water programs, including Washington, D.C., and water
systems located on Native American reservations.
The current primary drinking water standards, known as the National Primary Drinking
Water Regulations (NPDWRs), are legally enforceable standards that apply to public
water systems subject to inorganic, organic, radionuclide, microbial or other health-
affecting contaminants (see "Water Treatment Standards and Methods -- Quick
Reference Charts for the Dealer," WC&P, July 2000). These primary standards set
maximum contaminant levels (MCLs), which is the maximum permissible level of a
contaminant in water delivered to any user of a public water system. The MCL is set as
close as is feasible to the level where there are no known or anticipated health effects
with help of the best available technology or treatment techniques. Where it's unfeasible
to monitor and ascertain the level of a particular contaminant, the USEPA sets treatment
techniques instead of MCLs. The required treatment techniques are designed to prevent
known or anticipated health effects. In addition, the USEPA sets maximum contaminant
level goals (MCLGs) indicating the level of a contaminant where no known or
anticipated adverse effect on human health is noted. MCLGs are non-enforceable public
The Environmental Working Group (EWG), an activist environmental/political watchdog
organization in Washington, D.C., has collected state reports and provided a national
average for data submitted during 1994-1995. Its statistics, while they may differ slightly
from those presented by the USEPA, are similar enough to merit inclusion here. During
1994-1995, the EWG reported, more than 10 percent of the nation’s 173,000 public
drinking water systems violated health standards for chemical, radiological or microbial
contaminants, or filtration and disinfection and water treatment regulations. The 18,542
utilities in noncompliance served compromised drinking water to over 45 million people
(see Table 1).
From 1994-95, Delaware was the state with the highest percentage of systems with
violations of health standards, followed by South Dakota, Arizona and Idaho. The No. 1
violation was failure to comply with adequate testing and sampling, suggesting the
possibility that noncompliance figures are greatly underestimating the true level of
contamination. In addition, regulations are only effective at monitoring and enforcing
minimum levels of recognized health hazards, where many more unrecognized hazards
are thought to exist. Furthermore, health standards are set on the basis of known
information of public health effects of single contaminant exposures. It’s likely that
system failures result in exposure of consumers to a variety of contaminants with possible
Because of their ubiquitous nature and non-point source impact, microbes are widespread
and a difficult contaminant to control. In addition, disinfection by-products (DBPs) are
also widespread due to the addition of disinfecting agents protecting against microbial
growth. Chemical agents, i.e., from waste plants or industrial discharges, are largely from
point sources and may be easier to control. Where contaminants are naturally present --
such as radionuclide contaminants as a result of natural erosion -- the problem is
generally regional, offering increased awareness and the possibility for application of
It’s important to note that regulations are only set for recognized hazards that have been
associated with human illness. Increased knowledge of harmful agents and better
reporting by medical facilities have enabled better identification of environmental
hazards; however, new agents are frequently being discovered. The USEPA has
committed to regulation of additional environmental hazards as well as conducting
research on suspect contaminants. Even with this focused effort, no information is known
or formal testing being conducted regarding the effect of combined hazard exposures.
Thus, individual contaminants may in fact be responsible for mild disease separately but
when combined with other hazards, may invoke a more serious effect.
The most recent year for which the USEPA has completed data on state violations is
1998. USEPA results indicate that based on the information reported to the agency by
individual states, 20 percent of reporting public water systems recorded some kind of
violation -- 102,437 violations total. Eighty-four percent of the violations were for
monitoring and reporting infractions while 16 percent were health-based violations. Of
the health-based violations, 7 percent were due to chemical contaminants, 74.5 percent
exceeded the Total Coliform Rule, 1.6 percent exceeded the lead and copper rule and 17
percent violated the Safe Water Treatment Rule.
Violations from utilities serving very large populations -- more than100,000 persons --
are of particular concern since a health violation has the potential to expose a larger
number of people. The states with the most utilities serving over 100,000 consumers
reporting violations in 1996, 1997 and 1998 were Nevada, Puerto Rico, New Jersey and
Arizona; however, those states whose violations affected the most people were
California, Texas, Puerto Rico and Arizona (see Figure 1).
The mouse points the way
You can view updates on local drinking water suppliers by logging onto the USEPA’s
website at www.epa.gov/ogwdw. Select “Local Drinking Water Information” to view a
map of the United States. Clicking on a particular state provides links to specific counties
and current violations or other water quality related announcements.
The site, which is linked to a database for the Safe Drinking Water Information System,
allows consumers to obtain information pertaining to the source of their drinking water
and compliance trends. Consumer confidence reports are also available on-line for many
states. These reports provide information as to how a particular water source is treated
and what’s detected (not just violated standards) in the water source.
Even without access to the Internet, calling the Safe Drinking Water hotline at (800) 426-
4791 gives contact information for a specific utility with additional information. It’s
important that consumers be aware of the quality of their water so that appropriate
decisions may be made as to the need for point-of-use treatment options.
Although the USEPA is keeping regulatory tabs on local drinking water suppliers,
information on contamination events aren’t available until long after exposures have
occurred. Consumers may wish to access information on their particular watershed more
frequently and determine how much confidence they have in their public drinking water
supply. Local consumer confidence reports -- also known as water quality reports --
should be available from your local water utility or service provider. Knowing the
violation history of individual water supplies may help consumers determine the need for
additional point-of-use treatment options.
1. Morris, Levin, In Reichard, et al., “Estimating the incidence of waterborne infectious
disease related to drinking water in the United States, assessing and managing health
risks from drinking water contamination: Approaches and applications,” International
Association of Hydrological Sciences Press, Great Britain, 1995.
About the author
Dr. Kelly A. Reynolds is a research scientist at the University of Arizona with a focus on
development of rapid methods for detecting human pathogenic viruses in drinking water.
She holds a master of science degree in public health (MSPH) from the University of
South Florida and doctorate in microbiology from the University of Arizona. Reynolds
also has been a member of the WC&P Technical Review Committee since 1997.
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