The EPA’s Office of Water has signed the prepublication version of the Contaminant Candidate List (CCL) 5 which contains a wide variety of chemicals that the agency has honed in on for future regulation, including a group of per- and polyfluoroalkyl substances (PFAS).
The CCL and previous editions
- The Safe Drinking Water Act (SDWA) was initially passed in 1974 (amended in 1986 and 1996) to protect the U.S. drinking water supply. The Act allows the Environmental Protection Agency (EPA) to set national primary drinking water regulations (NPDWR) to protect against naturally-occurring or man-made contaminants in drinking water.
- Beginning in 1996, the EPA began publishing the Contaminant Candidate List (CCL) every 5 years, covering unregulated contaminants that may pose risks for U.S. drinking water. These chemicals must be known to or anticipated to occur in public water systems, and may include hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and pesticides regulated under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). After releasing the CCL, EPA will then decide whether to regulate at least five contaminants from the CCL via NPDWR.
- There have been five total CCLs (including the most recent CCL 5). The first CCL was published in 1998 and was developed based on National Drinking Water Advisory Council (NDWAC) recommendations and contained 50 chemicals and 10 microbial contaminants. The list has since slowly expanded, with the current CCL 5 composed of 66 chemicals, 3 chemical groups, and 12 microbial contaminants.
- The SDWA also directs the EPA to consider the possible effects of contaminants on vulnerable subgroups that are at greater risk of adverse health effects due to contaminants in drinking water that comprise a meaningful portion of the general population, including children, pregnant women, and the elderly.
- The EPA is also required to publish a list of no more than 30 unregulated contaminants for public water systems to monitor under the Unregulated Contaminant Monitoring Rule (UCMR). UCMR contaminants must (1) not have been monitored under prior UCMR cycles; (2) may occur in drinking water; and (3) are expected to have a completed, validated drinking water method in time for rule proposal. The CCL process identifies contaminants that may require regulation, and the UCMR process provides the data necessary for the EPA to make regulatory decisions on the contaminants.
- The UCMR requires that the EPA enter monitoring data it has collected into the National Contaminant Occurrence Database (NCOD), which is then used to make regulatory decisions as well as initiate non-regulatory public health decisions. UCMR 5, the most recent list, was released on December 27, 2021, and focuses on 29 per- and polyfluoroalkyl substances (PFAS) and lithium in national public water supplies.
Development of CCL 5
- The EPA used a similar process to develop CCL 5 as it did with CCLs 3 and 4. The agency received expert input and recommendations from the EPA’s Science Advisory Board (SAB), the NDWAC, and the National Research Council (NRC). The agency evaluated 134 separate data sources, identifying 43 as related to the CCL mission. From those, the EPA surveyed 21,894 chemicals as possible CCL additions. However, as mentioned above, the agency cut the total number of chemicals and groups for CCL 5 to 66 chemicals, 3 chemical groups, and 12 microbial contaminants.
- In October 2018, the EPA solicited public nominations for unregulated chemicals and microbial contaminants for inclusion on CCL 5. From this solicitation, the EPA received nominations for 89 contaminants (73 chemicals and 16 microbes). The agency ended up including 47 of the 73 nominated chemicals, including 1,4-dioxane, chlorpyrifos, manganese, and molybdenum. 12 of the 16 microbes nominated for inclusion ended up on the CCL 5, with Salmonella enterica, Aeromonas hydrophila, and Hepatitis A not having high enough occurrence scores to make it onto the list, and a nomination for mycobacterium was replaced with one that occurs in drinking water.
- To evaluate those chemical nominations, the EPA compared the nominated chemicals with the top 250 chemicals (via a screening scoring system) and identified 19 chemicals that were already included within the top 250 of the potential CCL 5 chemicals that did not have associated NPDWRs.
Major aspects of CCL 5
- The EPA published the draft CCL 5 on July 19, 2021. In the notice, the EPA requested that the public comment on supporting data the EPA could use for draft CCL 5 substances, any existing data the EPA had used for CCL 5, and the improvements that the EPA implemented through the development of CCL 5.
- EPA Assistant Administrator for the Office of Water, Radhika Fox, signed the notice “Drinking Water Contaminant Candidate List 5 – Final” on October 28, 2022. Although it was submitted for publication in the Federal Register (FR), at the time of publication of this article it has not yet been published in the FR.
- One of the major new sections of CCL 5 is its focus on PFAS. PFAS are synthetic chemicals that are commonly used to make products resistant to heat, stains, or water and are found in a diverse array of products and industries. PFAS are not strictly defined, although many definitions will focus on the chemicals as a group, defining them by a substance with at least one fluorinated carbon atom. PFAS are very stable in the environment and do not readily break down. In addition, intermediates, degradates, processing aids, and byproducts of PFAS manufacturing may also meet the structural definition of PFAS, which makes individually listing PFAS difficult.
- Therefore, the EPA decided to list PFAS chemicals based on their structures in CCL 5. PFAS as defined in CCL 5 must contain one of the following three structures: (1) R-(CF2)-CF(R′)R′′, where both the CF2 and CF moieties are saturated carbons, and none of the R groups can be hydrogen; R-CF2OCF2-R′, where both the CF2 moieties are saturated carbons, and none of the R groups can be hydrogen; CF3C(CF3)RR′, where all the carbons are saturated, and none of the R groups can be hydrogen.
- The EPA has stated that if it discovers emerging PFAS contaminants or groups, the EPA will consider moving those contaminants into a future CCL or going directly to regulatory determination processes for an NPDWR.
EPA responses to comments on CCL 5
- The EPA received a total of 54 unique comment letters over the comment period, and cataloged its responses in a document entitled Comment Response Document for the Draft Fifth Drinking Water Contaminant Candidate List (CCL 5) – Categorized Public Comment.
- EPA received two comments on chemical data and data sources used in developing CCL 5. One of the comments recommended expanding the use of wastewater data and data collected under FIFRA and the Toxic Substances Control Act (TSCA) to develop the CCL. The EPA stated that it would consider expanding the use of wastewater as well as FIFRA and TSCA data for future CCL cycles.
- Additional comments criticized the EPA for the draft CCL 5 definition of PFAS. The comments focused on how the draft definition would exclude certain PFAS, such as perfluoro-2-methoxyacetic acid (PFMOAA), which has been discovered in the Cape Fear River system (an AgencyIQ article on Cape Fear River PFAS contamination is available here).
Where the CCL will go from here
- Although we will not see another CCL for almost five years, the current list as well as the EPA’s comments about future lists can shed some light on where the EPA will go from here. As the EPA gears up to release NPDWRs for perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in addition to the PFAS additions to CCL 5, it is clear that the agency will continue to focus on remediating and reducing the use and concentration of PFAS in the environment.
To contact the author of this analysis, please email Walker Livingston ( [email protected])
To contact the editor of this analysis, please email Patricia Iscaro ( [email protected])