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Basic Information


What is the drinking water CCL?
The drinking water CCL is the primary source of priority contaminants for which EPA collects data to inform decisions about whether regulations are needed. The contaminants on the list are known or anticipated to occur in public water systems. However, they are currently unregulated by existing national primary drinking water regulations.

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How often is the CCL published?
The Safe Drinking Water Act (SDWA) requires EPA to publish a CCL every five years. EPA published the first CCL (CCL 1) of 60 contaminants in March 1998 and the CCL 2 of 51 contaminants in February 2005. The Final CCL 3 was published in September, 2009.

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What contaminants are included in the Final CCL 3?
The final CCL 3 includes 104 chemicals or chemical groups and 12 microbiological contaminants. The list includes chemicals used in commerce, pesticides, biological toxins, disinfection byproducts, and waterborne pathogens. The contaminants on the list are not regulated by existing national primary drinking water regulations, are known or anticipated to occur in public water systems, and may require regulation. We evaluated approximately 7,500 chemicals and microbes and selected 116 candidates for the Final CCL 3.

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Does the CCL impose any requirements on public water systems?
No. The CCL alone does not impose any requirements on public water systems. However, we may regulate contaminants on the list in the future. Before regulating a contaminant, EPA would 1) publish a preliminary determination to regulate; 2) issue a final determination; 3) publish a proposed regulation; and 4) issue a final regulation. Once a regulation is promulgated, public water systems typically have three years to come into compliance with a new regulation.

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What happens to contaminants on the CCL?
After the listing process, the CCL 3 contaminants are evaluated further to determine if a contaminant has sufficient data to meet the regulatory determination criteria set forth in SDWA section 1412(b)(1). EPA characterizes each contaminant included on the CCL for their data needs in three categories; health effects, occurrence, and analytical methods. The health effects, occurrence, and analytical methods needs are listed in the Federal Register notice for CCL 3. The data and information used to evaluate data needs are provided in the contaminant information sheets, and in the supporting documentation. If the data are sufficient for a particular contaminant, then a regulatory determination may be made.

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What is a regulatory determination?
A regulatory determination is a formal decision on whether EPA should issue a national primary drinking water regulation for a specific contaminant. The law requires EPA to make regulatory determinations for five or more contaminants from the most recent CCL. The Agency published the final regulatory determinations for 9 contaminants on the first CCL in July of 2003. The Agency published the final regulatory determinations for 11 contaminants on the second CCL in July 2008.

It is important to note that EPA is not limited to making regulatory determinations for only those contaminants on the CCL. The Agency can also decide to regulate other unregulated contaminants if information becomes available showing that a specific contaminant presents a public health risk.

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What criteria does EPA consider to make regulatory determinations?
When making a “determination” to regulate, the law requires that EPA make three findings:

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How were CCL 1 and CCL 2 developed?
CCL 1 was developed based on the review by technical experts of readily available information and contained 50 chemicals and 10 microbial contaminants. In developing the CCL 1, EPA consulted with the scientific community and the National Drinking Water Advisory Council (NDWAC) on a process to identify contaminants. Based on the NDWAC recommendations, the Agency developed and used screening and evaluation criteria to develop a list of chemical contaminants for CCL. CCL 2 consisted of CCL 1 contaminants that were not removed from the list through the first regulatory determination process.

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Why did EPA change the CCL process?
During development of CCL 1, EPA received comments that indicated a need for a broader, more comprehensive approach for selecting contaminants for future CCLs. In response, the Agency sought advice from the National Academies of Science - National Research Council and the National Drinking Water Advisory Council. We revised the CCL process based, in part, on their recommendations.

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What did the National Academy of Sciences (NAS) recommend for creating future CCLs?
The 2001 NAS report proposed a broader, more comprehensive screening process to assist EPA in identifying those contaminants for the CCL. The NAS recommended that we identify a broadly defined "universe" of potential drinking water contaminants, then assess and reduce the universe to a preliminary CCL (PCCL) using simple screening criteria that indicate public health risk and the likelihood of occurrence in drinking water. NAS recommended that EPA assess the PCCL contaminants in more detail using a classification approach and expert judgment to evaluate the likelihood that specific contaminants could occur in drinking water at levels of public health concern, and which should be on the CCL.

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What did the National Drinking Water Advisory Council (NDWAC) recommend for creating future CCLs?
In 2002, EPA consulted with NDWAC and received advice for implementing the 2001 NAS recommendations. NDWAC recommended that EPA move forward with the NAS recommendations using a step-wise adaptive management approach. This approach provides a framework to implement recommendations in phases. The phased implementation allows EPA to refine and adjust the CCL process as more information and experience are attained.

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Why did EPA solicit public nominations for the CCL3?
EPA asked the public for information on contaminants in October 2006 to help identify unregulated contaminants that may require a national drinking water regulation and which should be considered for the CCL 3.

The contaminant nominations process was an opportunity for EPA to gather information from the public on contaminants they thought should be considered for the CCL. NDWAC and NAS recommended that EPA include public participation early in the CCL development process.

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Where can I find data and information on CCL contaminants?
For information on the CCL and the contaminant selection process, please visit the CCL 3 home page at: http://www.epa.gov/safewater/ccl/ccl3.html. For general information on drinking water, please visit the EPA Safewater Web site at www.epa.gov/safewater or contact the Safe Drinking Water Hotline at 1-800-426-4791. The Safe Drinking Water Hotline is open Monday through Friday, excluding legal holidays, from 10:00 a.m. to 4:00 p.m., Eastern time, except legal holidays.

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