Environmental Associates
Know Your Environment
Standards for Safe Drinking Water
by Roland Wall, November 2001
- Introduction
- Safe Drinking Water Act
- Safe Water Terminology
- Safe Drinking Water Standards
- Conclusion:
- References
Introduction
Water is one of the fundamental requirements of life, and as such, guaranteeing the availability of safe drinking water has long been a function assumed by governments. One of the most basic expectations of citizens from industrialized nations is that tap water will be clean and safe. Few people in the U.S. realize that this is actually an extraordinary expectation, and that many people in the world cannot share it.
In many of the developing nations, obtaining safe drinking water is a constant challenge. Waterborne intestinal bacteria alone kills three million children a year, most from desperately poor countries. The World Water Forum estimates that on the order of 2 billion people globally will have difficulty finding safe water sources in the coming decade. In Africa alone, 19 nations are listed by the UN Environment Program as being the most water stressed in the world.
Yet, even in the so-called "developed" nations, clean drinking water is not guaranteed. In 1999 the World Health Organization (WHO) announced a startling conclusion - one in seven people in Europe have difficulty obtaining clean drinking water. [1] Diseases such as cholera and typhoid, more often "associated with developing countries or perhaps medieval Europe" are now being seen in modern European nations.
A sizable proportion of these disease outbreaks occur in the poorer nations of eastern Europe (in Albania, 25 people died in 1994 just from waterborne cholera, while in Latvia 55% of shallow wells were found to have pathogenic microorganisms). Yet even the most technically advanced countries have not been spared. Sweden, for example, had over 27,000 cases of waterborne disease from 1989 to 1999.
The problem is even more pronounced in Asia and Africa. The former Soviet republic of Tajikistan had 4000 cases of typhoid fever in 1996, and, while some areas like Singapore have well developed water distribution, others such as Indonesia may have as few as 35% of the population able to obtain clean, safe water. Government reports from Kazakhastan indicate that groundwater is "polluted everywhere."
Nor is bacterial infection the only danger water can present. A variety of artificial and natural chemical contaminants can affect human health. Simply delaying the tightening of arsenic standards earlier this year in the U.S. led to an enormous public outcry, but in some parts of Asia people routinely consume water with arsenic levels 10 times higher than any found in North America. Other chemicals—even those added to water for good reasons—can be present in dangerous amounts. In Moscow, where the danger of microbial contamination of water is slight, the excessive use of chlorine to purify water has nonetheless led many to seek out sources of bottled water.
Given this situation around the world, it is all the more remarkable that water in the U.S. (and, comparably, in Canada) is maintained at such high standards. In 1996, for example, less than 2% of the nation's 55,000 community water systems had any water treatment violations at all. During 1997—1998 the Centers for Disease Control and Prevention (CDC) reports [2] that 2038 people, less than one ten-thousandth of a percent of the nation's population, became ill from drinking water, with no fatalities. When waterborne diseases do occur (as in 1993, when accidental introduction of the microbe Cryptospora in the Milwaukee water system left almost half a million sickened and killed dozens) it becomes national news. The response is rapid and intensive.
Most people in the U.S. take for granted that what comes out of the tap is clean and healthy. (And cheap. Americans on the average spend just one penny for every five gallons of water they consume.) Though many people may be unclear as to exactly how drinking water is regulated, most would be certain that "the government" has some processes of inspection and enforcement that oversee this vital resource.
For the most part, in the U.S., they are correct. The Environmental Protection Agency (EPA), empowered by the Congress and working in conjunction with state and local governments, sets and enforces a variety of specific standards for evaluating drinking water. To a great extent it is a very effective system.
Still, much of this work happens behind the scenes, is highly technical, and in some cases, such as the recent controversy over arsenic standards, is dogged by some level of scientific uncertainty not easily assessed by lay persons. For the most part, as long as there is no sense that water supplies are endangered, the public has been willing to trust a system of experts to craft the drinking water standards. Considering, however, that issues do arise from time to time that bring safe drinking water to the forefront, it is useful to have an understanding of how this issue is regulated.
Safe Drinking Water Act
In the U.S., the Safe Drinking Water Act (SDWA) is the policy cornerstone for protecting the nation's drinking water supplies. Passed in 1974 with major amendments in 1986 and 1996, the Act is designed to ensure that drinking water is safe at all stages in its delivery, from the source to the consumer. Any water system, public or private, that serves more than 25 users must comply with regulations established under the SDWA.
The SDWA is based on the realization that there are a number of ways the quality of drinking water can be compromised. It directs the EPA to set safe limits of possible contaminants in any water that is being used for human consumption. In addition to microbes, it regulates a number of other substances—ranging from cyanide to uranium—that can compromise human health and can become present in the water supply. Some of these, like atrazine pesticides, are entirely the result of human activity. Others, including the mineral arsenic, are more likely to come from natural deposits.
In addition to setting the Safe Drinking Water Standards (discussed below) the SDWA calls for a broad spectrum of education, monitoring, testing, inspection and enforcement, promoting safe drinking water through "multiple barriers against pollution." These "barriers" are designed to act at each stage of the acquisition and distribution of water.
Though the initial version of the SDWA emphasized regulations for filtration and treatment, subsequent amendments broadened the scope of protections while expanding the regulations that water systems must follow. For example, there are now requirements for the assessment of "source water," i.e. the ground or surface source from which drinking water is withdrawn, and other regulations that govern some of the so-called "injection wells" which are used to pump waste into deep underground storage.
The 1996 Amendments also direct the EPA to use public education, including meetings and informational materials, to make the public better aware of how drinking water is obtained and protected. "Consumer confidence reports"—through which each water system reports on safety issues to it's customers—are also part of the public information goals. According to the EPA, "The [consumer confidence] report provides information on your local drinking water quality, including the water's source, the contaminants found in the water, and how consumers can get involved in protecting drinking water." [3]
Much of this monitoring and enforcement is actually performed by state drinking water programs under the oversight of the EPA. The law allows for state governments to have "primacy" over implementation of the SDWA, provided they enforce standards that are as stringent as those promulgated by the federal government. At this time all but two state jurisdictions have such primacy.
Recognizing that the costs of meeting new standards may be significant, the 1996 Amendments established a "Drinking Water State Revolving Fund" from which states can obtain money to assist water systems in making necessary structural improvements. The EPA is directed to consider cost as well when calculating the benefits of a standard relative to the expense of implementation.
The law also takes into account that there are a variety of systems supplying water in the U.S., serving different groups of people at different times. These can range from a large municipal system that supplies hundreds of thousands of consumers, to a seasonal park that seldom supplies water to more than a handful of people a few months of the year. Because the risk of toxicity of many contaminants is based on the cumulative time that a person is exposed to them, regulations differ somewhat depending on the length of time which consumers use a particular source of water.
In general, the majority of people receive water from Community Water Systems, which serve the same people year round, or from Non-Transient, Non-Community Water System, which serves the same people for less than the whole year but more than six months at a time. The first includes the general systems that provide water to residences while the latter may be a school with its own water system. Transient, Non Community Systems, serving consumers for six months or less a year (a summer camp, for example) have slightly less stringent regulations as it is assumed exposure to the water will be briefer.
Systems are also recognized as differing according to the number of persons served. Those serving less than 3300 people are considered "small" systems which—while numerous—serve only a fraction of the U.S. population. To address the difficulties of such systems in meeting the requirements of the SDWA, the current version of the law offers assistance from the state revolving fund, variances in regulation to allow the best technologies for small systems, and also encourages small systems to consolidate or re-configure.
The National Drinking Water Advisory Council (NDWAC) is an appointed body which provides guidance and review of all EPA actions under the SDWA. The Council consists of fifteen members, five each from the general public, from state and local water agencies and from private organizations "demonstrating an active interest in the field of water hygiene and public water supply," including two from small, rural public water systems. Serving staggered, three year terms, the Council has working groups that advise the EPA on topics such as regulation review, microbial and disinfectant by-product rules, and most recently, arsenic standards.
Safe Water Terminology
Like all legislation, the Safe Drinking Water Act has its own terminology and definitions. Here are a few of the important terms used in enforcing the SDWA:
- Community Water Systems
- Public or private water systems that serve the same people year round.
- Non-Transient, Non-Community Water System
- Public or private water systems that serve the same people more than six months of the year (e.g. a school).
- Transient, Non Community Systems
- Public or private water systems that serve various people less than six months of the year (e.g. a summer camp.
- "Small" Water Systems
- Systems serving less than 3300 consumers.
- Candidate Contaminant List (CCL)
- The regularly updated list from which the EPA chooses which substances that appear in water will be regulated.
- Maximum Contaminant Level Goal (MCLG)
- The ideal goal of the level that a substance in water will remain below.
- Maximum Contaminant Level (MCL)
- The enforceable, regulated goal for a substance in water.
- Treatment Technique (TT)
- An alternative to regulating the level of a substance in water. For those contaminants for which it is not practical to set an MCL, a treatment technique is required to address the presence of the substances.
- Primary Drinking Water Standards
- The principle standards that regulate the presence of specific substances in water, currently applied to about 80 possible contaminants.
- Secondary Drinking Water Standards
- A set of non-enforceable recommendations as to the level of particular substances that might affect the taste or appearance of water.
Safe Drinking Water Standards
When considering the Safe Drinking Water Standards—the central feature of the SDWA— it is important to remember that all water contains "impurities." These range from naturally occurring minerals and salts (some of which are considered to improve the taste of water and may be marketed as such) all the way to potentially toxic chemicals and pathogenic microorganisms.
Not all substances in water are contaminants, not all contaminants are equally dangerous, and even dangerous contaminants may be less than toxic at lower concentrations. Though scientific estimates have an inherent level of uncertainty, it is well understood that the risk of a substance causing a health problem is highly dependent on both the amount of it consumed and the length of time to which one is exposed to it. The point of regulations is not to provide "pure" water—something virtually non-existent in nature—but to guarantee water that is safe and wholesome according to the best scientific understanding.
Towards this end, the US EPA is empowered to set standards for the Maximum Contaminant Level (MCL) of potentially dangerous substances in water. In all, there are over 80 substances which water providers are responsible for monitoring and controlling. These range from well-known contaminants like lead, to new concerns like Cryptospora (which became a focus of regulation following the Milwaukee experience).
In 1974, the original version of the SDWA gave the EPA broad flexibility in how standards were set. "However," according [4] to the Congressional Research Service, "by the early 1980s, EPA had regulated only one additional contaminant beyond the 22 standards issued by the Public Health Service before EPA's creation." Concerned that process was moving too slowly, Congress—in the 1986 Amendments—specified that the EPA set standards for 83 priority contaminants by 1989 and that at least 25 contaminants be added every three years from then on.
Several problematic issues arose as a result of this amendment. The EPA Administrator at the time warned that "requiring the Administrator to regulate all chemicals listed would preempt decisions based on good scientific evidence and could lead to unsound and unwarranted regulations." [5] Furthermore, the amendments required that water systems meet specific standards to the greatest extent "feasible," regardless of whether or not the techniques used to reach that particular standard might actually diminish the overall quality of the water
The 1996 Amendments were intended to strike a balance between previous versions of the law—ensuring standards for safe drinking water while giving the EPA the flexibility to address costs, scientific concerns, and overall risk-reduction benefits of particular regulations. It also removed the numerical requirement that the EPA regulate 25 new contaminants every 3 years. In its place, the law now requires the EPA maintain a list of "candidate" contaminants from which, every five years, at least five new items are chosen for regulation.
In setting these standards, the EPA goes through a three step process. First, they identify those substances that may cause problems with human health. Items on the "Candidate Contaminant List" (CCL)—last published in 1998 and revised every five years—are chosen from substances that appear in water and that cause health effects. Candidate contaminants are not currently regulated, but may be in the future.
After potential contaminants have been identified, the CCL is prioritized according to whether scientists believe a substance should be immediately regulated, should be researched further, or should be monitored for occurrence in water supplies. The next five (or more) substances from the list to be regulated are then chosen based on whether, "regulating the contaminants would present a meaningful opportunity to reduce health risk." [6]
The second step, once a decision to regulate has been made, is to establish the maximum contaminant level goal (MCLG). This is the maximum amount of the substance which will result in no known health risk, in other words, the most that can be consumed without having any noticeable effect on a human being. By determining this standard, agencies are given a goal towards which to strive; in the case of cancer-causing substances the MCLG is usually zero.
The MCLG, however, is not an enforceable standard but rather represents a theoretical ideal. The third step of the regulating process is to determine the amount of a substance that will actually be present in the water. The legally enforceable standards, known as the maximum contaminant level (MCL) are designed to be "as close as feasible" to the MCLG. Feasibility includes both technical and economic considerations within the best current technology, taking cost into account.
Thus, it may be permissible to have a known carcinogen with a MCL above zero because it may simply not be feasible to remove it completely from a water supply within the constraints of current technology and current water supply systems. In other cases, such as the heavy metals beryllium or copper, the MCL and the MCLG are the same, indicating that it is feasible to require a level at which the substance has no known effect on human health.
When technical or economic factors make it unfeasible to measure low doses of a contaminant, the standards specify a Treatment Technique (TT) instead of an MCL. "A treatment technique (TT) is an enforceable procedure or level of technological performance which public water systems must follow to ensure control of a contaminant." [7] This could be a specific filtration or chemical treatment process and it is designed to protect human health when MCL's would be difficult or impossible to measure.
Standards for substances with health effects are referred to as Primary Drinking Water Regulations; the EPA also sets Secondary Drinking Water Regulations that are neither mandatory nor enforced, but act as guidance for water systems in preventing "nuisance" problems like poor water taste or unusual color. In some cases these may be substances that are also regulated (at higher amounts) under the primary standards. Four parts per billion (ppb) is the level, for example, at which fluoride may cause bone disease, but at 2 ppb—its secondary standard—it can discolor teeth. Iron, on the other hand, is not regulated at all as a health hazard but at .3 ppb can give water an unpleasant taste.
Ideally, setting the Primary Drinking Water Standards would be based entirely on sound scientific evidence as to the risk presented by the substance being regulated. In reality, risk assessment remains an inexact science, and a number of political and economic factors enter into the decision making.
The fact that the MCL often differs from the ideal goal, in itself suggests that compromises have to be made based on realistic expectations. The public may not approve of their water being contaminated but at some point scientific uncertainty and financial reality require the acceptance of standards that are less than perfect.
On the other hand, water safety can be a politically volatile issue. Citizens may accept minute amounts of substances in their water, if they clearly understand the risk is minimal and the cost of remediation prohibitive. Public reaction, however, will not tolerate a demonstrated health threat. Thus the 1996 Amendments, probably reflective of the Milwaukee crisis, make several specific references to control of the Cryptospora microbe.
Control of microbial contamination, however, is illustrative of the sorts of balances that must be struck in protecting drinking water. While the use of disinfectants, such as chlorine, can greatly reduce the possibility of pathogen contaminants, the disinfectants themselves, or their byproducts, may also cause health problems. The 1996 Amendments require the EPA to develop rules that weigh the relative hazards of both microbes and disinfectants.
Setting of standards is time consuming and labor intensive. Reviews of research, expert opinion, and input from stakeholders (water suppliers, the public, etc.) must be taken into account. Therefore, the EPA must prioritize the possible contaminants to be regulated and work towards controlling those substances for which the most public benefit can be achieved quickly.
Currently there are five areas on which efforts for standard-setting are being concentrated. First, as mentioned, determining practical rules for microbes and disinfectants. Secondly, standards that would apply to possible microbial contamination of groundwater, a recently discovered concern. Third is limiting exposure of water to the natural radioactive gas radon while fourth is setting standards for the amount of uranium and other radionuclides. And finally, the 1996 Amendments instructed the EPA to set new standards for the presence of arsenic in drinking water. This final item resulted—for a time—in a generally quiet regulatory process becoming a matter of public controversy.
When the incoming Bush Administration announced that it would be delaying all new regulations during it's opening months in office, and then followed up with an order to delay new arsenic standards pending further scientific study, it found itself in a vocal debate with a variety of environmental advocates. Litigation seemed likely and many critics felt that the Administration was gambling with public health. The Administration countered however, that the potential high cost of implementing the regulations and the scientific uncertainty regarding the health effects justified a delay.
The arsenic debate, however, serves to demonstrate that the safe drinking water system in the U.S. has a self-correcting quality. Within months of the announcement that arsenic standards would be delayed, the National Research Council issued a new report reiterating the possible dangers of even low levels of arsenic in water. In response, the EPA has indicated that upcoming standards will be at least as stringent as those proposed by the Clinton Administration. Once again, the political process was able to mesh with scientific data to promote public health.
Conclusion: The Safest Water in the World
There has been a growing trend in the U.S. for consumers to purchase expensive bottled water out of fear that tap water may not be safe. A 1999 study, however, by the Natural Resources Defense Council (NRDC) revealed that many bottled waters—which are not regulated under the SDWA—actually have higher levels of contaminants than would be allowed in tap water. Ironically, then, many Americans forsake what is probably the safest water in the world to buy water that is marketed with unproven claims of purity and cleanliness.
It has been suggested that the high standard of water quality enjoyed in the U.S. can be ranked as one of the great technological achievements of the past century. It should also be recognized, however, as a significant political accomplishment. The development and consistent enforcement of drinking water standards, along with the institutional structures to provide expertise and resources to water suppliers, is at the heart of the process. Both technically and politically, it is an achievement of which Americans can be justifiably proud.
References
- WHO, 1999.Water and health in Europe:"Medieval" diseases lurking in the water supplies. Press Release 17 Mar. 99, EURO/06/99 World Health Organization, Copenhagen. [go back]
- Barwick, R., D. Levy, G. Craun, M. Beach, R. Calderon, 2000. Surveillance for Waterborne-Disease Outbreaks —United States, 1997—1998. CDC Morbidity/Morality Weekly Report-Surveillance Summaries. 49(SS04); 1-35. [go back]
- U.S. EPA, 2000a. It's YOUR Drinking Water: Get to know and protect it. U.S. Environmental Protection Agency, Office of Water. Publication No. EPA-810-K-99-002. [go back]
- Tiemann, M. 1996. Safe Drinking Water Act: Implementation and Reauthorization. Congressional Research Service, Issue Brief for Congress, No.91041. [go back]
- Tiemann, M. 1996. Cited above. [go back]
- U.S. EPA, 2000b, Setting Standards for Safe Drinking Water.
www.epa.gov/safewater/standard/setting.html [go back] - U.S. EPA, 2000b. Cited above. [go back]