Drinking Water Regulation

In the United States, the Environmental Protection Agency, through its Office of Ground Water and Drinking Water, regulates drinking water under the Safe Drinking Water Act. Under terms of the 1996 SDWA amendments, the agency performs that job through two processes:

1. Identifying contaminants to regulate


CCL/Regulatory Determination

EPA identifies unregulated contaminants that may warrant regulation in a Contaminant Candidate List that is updated every five years. For every CCL, the agency then determines whether each listed contaminant meets SDWA criteria for regulation, including whether regulation provides a "meaningful opportunity for reducing public health risks."

Through the first two CCL cycles, EPA identified one contaminant  – perchlorate – for regulation and decided not to regulate 20 contaminants.  EPA published its Preliminary CCL3 Determination in October 2014, which identified strontium for regulation and rejected regulation of dimethoate, 1,3-dinitrobenzene, terbufos and terbufos sulfone. In the Final Third Regulatory Determinations, if EPA continues on its path to regulate strontium, a final rule would be expected in 2019 or 2020. EPA also decided to include chlorate and nitrosamines in its Third Six-Year review that is scheduled to be released in 2016.

The agency released results of UCMR3 monitoring in April 2016.

In February 2015 EPA published and sought comment on a draft of CCL4 that lists 100 chemicals or chemical groups and a dozen microbial contaminants.

AWWA released a 239-page report in March 2015 (PDF, 6MB) that provides recommendations for CCL4, as well as recommendations for a more robust process to develop future CCLs. 

AWWA’s recommendations would result in a much shorter CCL4 than the list proposed by EPA in the February 2015. AWWA would include seven compounds plus one "super group" of disinfection by-products (DBPs) as the top priorities. An additional 11 compounds are also recommended, noting that occurrence data is needed for these 11 compounds through a future national monitoring program. This approach results in 18 compounds plus one super group on CCL4 as opposed to 100 chemicals or groups on the Draft CCL4 published by EPA.

The AWWA report, which is the outcome of a lengthy process led by the AWWA CCL Technical Advisory Workgroup, serves as a foundation for the Association’s official CCL4 comments to EPA (PDF) that were submitted in April.

Six-Year Review

EPA reviews existing regulations every six years to determine whether they still adequately protect public health, given any new health effects information that may have become available. If revisions to a standard are warranted, they can be made provided that no existing standard is revised in a way that reduces protection of public health.

2. Developing a regulation


Once EPA determines that a contaminant should be regulated or have its standard revised, the agency uses a two-step process for developing national drinking water regulations:

  1. First, a non-enforceable Maximum Contaminant Level Goal is established. The MCLG is the maximum level of a contaminant at which no known or anticipated adverse health effect would occur, allowing for an adequate margin of safety. By policy, the MCLG for carcinogens is set at zero.
  2. Next, an enforceable standard is developed, known as the Maximum Contaminant Level. The MCL is set as close to the MCLG as is feasible. The term “feasible” is defined by the SDWA as the level that may be achieved with the use of the best available technology or treatment techniques that EPA finds available (under field conditions and not solely under laboratory conditions), taking cost into consideration. EPA can establish a regulatory treatment technique when there is no reliable method that is economically and technically feasible to measure a contaminant.

additional information

CCLs/Regulatory Determinations

The SDWA amendments of 1996 set forth a cyclical process for EPA to identify "candidate" contaminants for possible regulation and then determine whether any meet SDWA requirements for being regulated. Collectively, this is referred to as the CCL/Regulatory Determination process.

Unregulated Contaminant Monitoring Program

One way that EPA identifies contamininants for possible regulation is through the Unregulated Contaminants Monitoring program, which generates a new rule every five years that requires certain systems to monitor for certain contaminants, but no more than 30 under each rule.

Monitoring under the third Unregulated Contaminant Monitoring Rule (UCMR 3) began in January 2013. The agency has posted summaries of monitoring results through January 2015. All UCMR results are added to the the National Contaminant Occurrence Database.

AWWA has provided resources to help utilities understand and respond to inquiries about the UCMR3 data.

EPA is expected to propose the fourth Unregulated Contaminant Monitoring Rule (UCMR4) in 2016

Contaminant Candidate Lists

The Contaminant Candidate List is the starting point for EPA’s regulatory development process for new contaminants. The Safe Drinking Water Act requires EPA to develop a list of potential contaminants to consider for regulation on every five years.

EPA has published three CCLs:

  • CCL1 in 1998 – 60 contaminants
  • CCL2 in 2005 – 51 contaminants;
  • CCL3 in 2009 – 116 contaminants.

AWWA has contributed the following resources on CCL3:

In February, 2015, EPA published and sought comment on a draft of CCL4 that lists 100 chemicals or chemical groups and a dozen microbial contaminants. Included on the draft list are cyanotoxins, which plagued Toledo, Ohio, in 2014.  EPA has issued a fact sheet for water systems on cyanotoxins (PDF).

AWWA released a 239-page report in March 2015 (PDF, 6MB) that provides recommendations for CCL4, as well as recommendations for a more robust process to develop future CCLs.

AWWA submitted comments on the draft CCL4 (PDF) in April 2015. AWWA recommends that the final CCL4 include 20-50 compounds rather than the 100 chemical and 12 microbial contaminants listed on the draft CCL4. Additionally, AWWA recommends the use of an alternative contaminant identification process to select a shorter list of compounds of greatest potential concern.

Regulatory determinations

The SDWA also requires EPA to make decisions, known as regulatory determinations, on at least five contaminants every five years. These decisions are typically decisions to regulate or not to regulate. But EPA can also decide to issue guidance, to issue a health advisory or conduct additional research.

The SDWA lists three criteria for EPA to take into account when making these decisions:

  1. The contaminant has or is likely to have an adverse health effect;
  2. The contaminants occurs at, or near, levels of health concern; and
  3. In the sole judgment of the EPA Administrator, a national regulation provides a meaningful opportunity for health risk reduction.

EPA has made two rounds of regulatory determinations:

  • First regulatory determination in 2003 – EPA decided not to regulate nine contaminants
  • Second regulatory determination in 2008 – EPA decided to regulate perchlorate.

EPA published its Preliminary CCL3 Determination in October 2014, which identified strontium for regulation and rejected regulation of dimethoate, 1,3-dinitrobenzene, terbufos and terbufos sulfone. In the Final Third Regulatory Determinations, if EPA continues on its path to regulate strontium, a final rule would be expected in 2019 or 2020. EPA also decided to include chlorate and nitrosamines in its Third Six-Year review that is scheduled to be released in 2016.

Six-Year Reviews


The SDWA requires EPA to review all existing drinking water regulations every six years to consider whether revision is appropriate given new informaiton on analytical methods, health effects, occurrence and treatment.

EPA has developed a National Contaminant Occurrence Database as part of its decision-making process for each Six-Year Review. EPA analyzed occurrence data from several states for the two reviews completed through 2012 to determine if revisions to the regulations were needed.

In the first Six-Year Review of 2003, EPA reviewed 69 standards and decided to revise the Total Coliform Rule.

In the second Six-Year Review of 2010, EPA reviewed 71 standards and decided to revise four standards: trichloroethylene (TCE) , tetrachloroethylene (PCE), epichlorohydrin and acrylamide.

The revised standards for TCE and PCE could potentially be incorporated into the carcinogenic volatile organic chemicals group rule scheduled to be proposed in 2013. The timeframe for revising the epichlorohydrin and acrylamide standards is unclear at this time.

AWWA most recently submitted comments (PDF) to EPA on the second Six-year Review.

The Third Six-Year Review is scheduled to be published in 2016. EPA has decided to include chlorate and nitrosamines in the Third Six-Year review.