Volume 43 Number 3
Monitoring Public Water Supplies
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 health-based violation.
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
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 health goals.
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 synergistic effects.
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 control measures.
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.
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
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.
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