Water: Regulation Development
Regulating Public Water Systems and Contaminants Under the Safe Drinking Water Act
EPA defines a water contaminant as any physical chemical, biological, or radiological substance or matter in water. EPA sets legal limits on the levels of certain contaminants in drinking water. The legal limits reflect both the level that protects human health and the level that water systems can achieve using the best available technology. Besides prescribing these legal limits, EPA rules set water-testing schedules and methods that water systems must follow. The rules also list acceptable techniques for treating contaminated water. The Safe Drinking Water Act gives individual states the opportunity to set and enforce their own drinking water standards if the standards are at least as strong as EPA's national standards. Most states and territories directly oversee the water systems within their borders.
- How does EPA decide which contaminants to regulate?
- How does EPA make a regulatory determination?
- Do regulatory determinations impose any requirements on public water systems?
- What are drinking water standards?
- Once EPA decides to regulate a contaminant, how does the Agency develop a regulation?
- When must public water systems comply with new primary standards?
- Are there special considerations for small systems?
- Who must comply with drinking water standards?
- After a drinking water regulation is established, can it be changed?
- Where can I find the federal drinking water regulations?
- Where can I find out more about EPA's rulemaking process?
How does EPA decide which contaminants to regulate?
EPA has drinking water regulations for more than 90 contaminants. The Safe Drinking Water Act includes a process that EPA must follow to identify and list unregulated contaminants, which may require a national drinking water regulation in the future. EPA must periodically publish this list of contaminants (called the Contaminant Candidate List or CCL) and decide whether to regulate at least five or more contaminants on the list (called Regulatory Determinations). EPA uses this list of unregulated contaminants to prioritize research and data collection efforts to help the Agency determine whether it should regulate a specific contaminant.
Based on public comment and other considerations, EPA then makes regulatory determinations from the list of contaminants, and publishes them in the Federal Register. A regulatory determination is a formal decision on whether EPA should initiate a rulemaking process to develop a national primary drinking water regulation for a specific contaminant.
There are two categories of drinking water standards:
A National Primary Drinking Water Regulation (NPDWR or primary standard) is a legally- enforceable standard that applies to public water systems. Primary standards protect drinking water quality by limiting the levels of specific contaminants that can adversely affect public health and are known or anticipated to occur in water. They take the form of Maximum Contaminant Levels or Treatment Techniques, which are described below.
A National Secondary Drinking Water Regulation (NSDWR or secondary standard) is a non-enforceable guideline regarding contaminants that may cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, or color) in drinking water. EPA recommends secondary standards to water systems but does not require systems to comply. However, states may choose to adopt them as enforceable standards. This information focuses on national primary standards.
- Alphabetical list of national primary and secondary drinking water standards PDF (6pp, 946K, About PDF)
- Regulatory Determinations for Priority Contaminants on the Second Drinking Water Contaminant Candidate List
How does EPA make a regulatory determination?
When making a determination to regulate, the Safe Drinking Water Act requires consideration of three criteria:
- the potential adverse effects of the contaminant on the health of humans,
- the frequency and level of contaminant occurrence in public drinking water systems, and
- whether regulation of the contaminant presents a meaningful opportunity for reducing public health risks
Do regulatory determinations impose any requirements on public water systems?
No. EPA’s determinations of whether a national primary drinking water regulation is necessary for a contaminant impose no requirements on public water systems. When making a determination, the Agency first publishes a preliminary regulatory determination in the Federal Register (FR) and provides an opportunity for public comment. After review and consideration of public comment, EPA publishes a final FR notice listing the regulatory determination decisions. If EPA makes a decision to regulate a particular contaminant, the Agency initiates the rulemaking process to establish the national primary drinking water regulation (NPDWR). Once the Agency establishes the NPDWR for a contaminant, public water systems would then have to follow specific requirements to comply with a regulation.
What are drinking water standards?
Drinking water standards are regulations that EPA sets to control the level of contaminants in the nation's drinking water. These standards are part of the Safe Drinking Water Act's "multiple barrier" approach to drinking water protection, which includes assessing and protecting drinking water sources; protecting wells and collection systems; making sure water is treated by qualified operators; ensuring the integrity of distribution systems; and making information available to the public on the quality of their drinking water. With the involvement of EPA, states, tribes, drinking water utilities, communities and citizens, these multiple barriers ensure that tap water in the United States and territories is safe to drink. In most cases, EPA delegates responsibility for implementing drinking water standards to states and tribes.
Once EPA decides to regulate a contaminant, how does the Agency develop a regulation?
After reviewing health effects studies, EPA sets a Maximum Contaminant Level Goal (MCLG), the maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would occur, and which allows an adequate margin of safety. MCLGs are non-enforceable public health goals. Since MCLGs consider only public health and not the limits of detection and treatment technology, sometimes they are set at a level which water systems cannot meet. When determining an MCLG, EPA considers the risk to sensitive subpopulations (infants, children, the elderly, and those with compromised immune systems) of experiencing a variety of adverse health effects.
- Microbial Contaminants: For microbial contaminants that may present public health risk, the MCLG is set at zero because ingesting one protozoa, virus, or bacterium may cause adverse health effects.
- Chemical Contaminants -- Carcinogens: If there is evidence that a chemical may cause cancer, and there is no dose below which the chemical is considered safe, the MCLG is set at zero. If a chemical is carcinogenic and a safe dose can be determined, the MCLG is set at a level above zero that is safe.
- Non-Carcinogens (not including microbial contaminants): For chemicals that can cause adverse non-cancer health effects, the MCLG is based on the reference dose. A reference dose (RfD) is an estimate of the amount of a chemical that a person can be exposed to on a daily basis that is not anticipated to cause adverse health effects over a person's lifetime. In RfD calculations, sensitive subgroups are included, and uncertainty may span an order of magnitude.
--The RFD is multiplied by body weight and divided by daily water consumption to provide a Drinking Water Equivalent Level (DWEL).
--The DWEL is multiplied by the relative source contribution which is the percentage of the RfD remaining after considering other exposure routes (e.g. food, inhalation, etc.) to determine the MCLG.
Once the MCLG is determined, EPA sets an enforceable standard. In most cases, the standard is a Maximum Contaminant Level (MCL), the maximum permissible level of a contaminant in water which is delivered to any user of a public water system. When there is no reliable method that is economically and technically feasible to measure a contaminant at particularly low concentrations, a Treatment Technique (TT) is set rather than an MCL. A treatment technique is an enforceable procedure or level of technological performance, which public water systems must follow to ensure control of a contaminant. Examples of Treatment Technique rules are the Surface Water Treatment Rule (disinfection and filtration) and the Lead and Copper Rule (optimized corrosion control).
The MCL is set as close to the MCLG as feasible. EPA must determine the feasible MCL or TT which the Safe Drinking Water Act defines as the level that may be achieved with the use of the best available technology, treatment techniques, and other means which EPA finds are available (after examination for efficiency under field conditions, not solely under laboratory conditions) are available, taking cost into consideration.
As a part of the rule analysis, Section 1412(b)(3)(C) of the 1996 SDWA Amendments also requires EPA to prepare a Health Risk Reduction and Cost Analysis (HRRCA) in support of any NPDWR . EPA must analyze the quantifiable and non-quantifiable benefits that are likely to occur as the result of compliance with the proposed standard. EPA must also analyze any increased costs that will result from the proposed drinking water standard. EPA must also consider (a) incremental costs and benefits associated with a range of MCL values, (b) health effects to the general population and sensitive sub-populations, and (c) any increased health risk to the general population that may occur as a result of the new MCL. 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."
When must public water systems comply with new primary standards?
Primary standards go into effect three years after they are finalized. If capital improvements are required, EPA's Administrator or a state may allow this period to be extended up to two additional years.
Under certain circumstances, exemptions from standards may be granted by States 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.
Are there special considerations for small systems?
Small systems receive special consideration from EPA and states. More than 90 percent of all public water systems (PWSs) are small, and these systems face the greatest challenge in providing safe water at affordable rates. The 1996 SDWA Amendments provide states with tools to comply with standards affordable for small systems. When setting new primary standards, EPA must identify technologies that achieve compliance and are affordable for systems serving fewer than 10,000 people. These may include packaged or modular systems and point-of-entry/point-of-use treatment devices under the control of the water system. When such technologies cannot be identified, EPA must identify affordable technologies that maximize contaminant reduction and protect public health. Small systems are considered in three categories: serving 10,000-3301 people; 3,300-501 people; and 500-25 people.
Who must comply with drinking water standards?
Drinking water standards apply to PWSs, which provide water for human consumption through at least 15 service connections, or regularly serve at least 25 individuals. Public water systems include municipal water companies, homeowner associations, schools, businesses, campgrounds and shopping malls.
After a drinking water regulation is established, can it be changed?
The Safe Drinking Water Act (SDWA) requires EPA to review each national primary drinking water regulation at least once every six years and revise, as appropriate. SDWA specifies that any revision must maintain or increase public health protection.
Where can I find the federal drinking water regulations?
Federal drinking water regulations are codified in Title 40 of the Code Federal Regulations (CFR).
- CFR Part 141: National Primary Drinking Water Regulations. These set maximum levels for contaminants allowed in drinking water.
- CFR PART 142: National Primary Drinking Water Implementation Regulations. These cover how the States, Tribes, and EPA shall carry out the Public Water System Supervision (PWSS) program.
- CFR Part 143: National Secondary Drinking Water Regulations. These set recommended standards that relate to the acceptability of drinking water to consumers. These are not enforceable (except for the public notice required for exceedance of the fluoride standard).
Where can I learn more about EPA's rulemaking process?
- From Risk to Rule: How EPA Develops Risk-based Regulations: PDF (95p. 1M)
- Unregulated Contaminants
- Current Drinking Water Regulations
- Other Actions
- Requirements of the Public Health Security and Bioterrorism Preparedness and Response Act of 2002 (Bioterrorism Act)
- Drinking Water Regulation Timeline PDF (1 pp, 86K) This chart shows the order in which EPA regulated more than 90 drinking water contaminants.
- Drinking Water Contaminant Fact Sheets are available on regulated contaminants that may be found in some public or private drinking water supplies.
- Health advisories provide information on certain contaminants. Health Advisories are guidance values based on non-cancer health effects for different durations of exposure (e.g., one-day, ten-day, longer-term, and lifetime).
- For links to drinking water guidance dealing with standards and their implementation, see Compliance Guidance.