Key Elements of the Safe Drinking Water Act (SDWA) and National Drinking Water Regulations
The Safe Drinking Water Act (SDWA) is a cornerstone of public health protection, ensuring the quality of drinking water across the United States. This law establishes the regulatory framework that the Environmental Protection Agency (EPA) follows to review and update drinking water regulations, ensuring that the water supplied to homes is safe and healthy. The SDWA mandates a periodic review every six years of the national primary drinking water regulations (NPDWRs), taking into account the impact of contaminants on public health and the available technologies for addressing them.
The national drinking water regulations include both primary and secondary standards aimed at managing contaminants that could affect public health or cause aesthetic issues. Through these efforts, the EPA seeks to enhance public confidence in the water supply, ensuring that communities are protected from potential risks associated with drinking water.
Major Elements of Six Year Review
The major issues EPA considers in conducting the Six-Year Review of national primary drinking water regulations include the elements listed below.
-Initial Review is conducted to identify regulations for which a detailed technical review would not be appropriate in the current review cycle.
-Health Effects information is reviewed for drinking water contaminants to identify the national primary drinking water regulations for which there is potential to revise the maximum contaminant level goal (MCLG) and maximum contaminant level (MCL).
-Contaminant Occurrence and Exposure Analysis information on the frequency, levels and geographic distribution of contaminants is analyzed to determine how changing an MCL or required treatment technique may affect health risks of water consumers and impact compliance costs for public water systems.
–Analytical Method Improvements are evaluated to determine whether there have been advances in laboratory technology to potentially enable a revision to the MCL for a regulated contaminant.
–Treatment Methods Feasibility review is conducted to ascertain there are technologies that could support a potentially lower MCL or a new treatment technique requirement.
-Risk-Balancing is conducted to address whether a change to an MCL and/or treatment technique will affect the risk from one or more other contaminants, and, if so, to consider revisions that will balance these overall risks.
–Implementation Issues are considered based upon EPA’s or states’ experience in implementing the regulations as written.
Six Year Review of Drinking Water Standards
Six Year Review 1 of Drinking Water Standards
In July 2003, EPA announced the review results for the first Six-Year Review (called the Six-Year Review 1). EPA reviewed 69 national primary drinking water regulations (NPDWRs) that were established prior to 1997. These 69 NPDWRs include 68 chemical NPDWRs and the Total Coliform Rule (TCR). Based on the Agency’s review, as well as the public comments received and other new information, EPA found that it was appropriate to revise the Total Coliform Rule (TCR). EPA found that it was not appropriate to revise the 68 chemical NPDWRs at that time.
Six Year Review 2 of Drinking Water Standards
In March 2010, EPA announced the review results for the Agency’s second Six-Year Review (called Six-Year Review 2). After performing a detailed review of 71 national primary drinking water regulations (NPDWRs), the Agency found that 67 NPDWRs remain appropriate (i.e., do not need to be revised) and four NPDWRs were candidates for regulatory revision. These four NPDWRs identified as revision candidates included:
Acrylamide
Epichlorohydrin
Tetrachloroethylene and
Trichloroethylene
In addition to the 71 NPDWRs reviewed in detail for the Six-Year Review 2, fourteen other NPDWRs were included in the review but did not need a detailed review because of recent or ongoing regulatory actions (i.e., disinfection byproducts (DBPs), lead and copper, and microbials).
Six Year Review 3 of Drinking Water Standards
EPA announced the review results for the third Six-Year Review (called Six-Year Review 3). Based on the agency’s detailed review of 76 national primary drinking water regulations (NPDWRs), EPA concluded that eight NPDWRs are candidates for regulatory revision. The eight candidates are Chlorite, Cryptosporidium (under the SWTR, IESWTR and LT1), Haloacetic acids, heterotrophic bacteria, Giardia lamblia, Legionella, Total Trihalomethanes, and viruses (under the SWTR). These eight NPDWRs are included in the:
-Stage 1 and Stage 2 Disinfectants and Disinfection Byproducts Rules
-Surface Water Treatment Rule
-Interim Enhanced Surface Water Treatment Rule
-Long Term 1 Enhanced Surface Water Treatment Rule
EPA determined that for the contaminants regulated under these rules there is new information on health effects, treatment technologies, analytical methods, occurrence and exposure, implementation and/or other factors that provide a health or technical basis to support a regulatory revision that will improve public health protection. This announcement is not a regulatory decision. Instead, it initiates a process that will involve more detailed analyses of health effects, analytical and treatment feasibility, occurrence, benefits, costs and other regulatory matters relevant to deciding whether a rulemaking to revise a regulation should be initiated. EPA is seeking public comment and information to help inform potential regulatory revisions for the eight candidates.
In addition to the 76 NPDWRs, this review included 12 other NPDWRs that did not need a detailed review because of recent, ongoing, or pending regulatory actions. Those contaminants having recent or ongoing regulatory actions are: lead, copper, total coliforms (under ADWR and RTCR), E. coli, and eight carcinogenic volatile organic compounds (cVOCs).
Six Year Review 4 of Drinking Water Standards
In July 2024, EPA announced the results of the fourth cycle of its Six-Year Review of existing national primary drinking water regulations (NPDWRs). Based on the agency’s review of existing NPDWRs, EPA determined that there are no additional candidates identified for regulatory revision.
The Six-Year Review Process
The Safe Drinking Water Act (SDWA) requires the EPA to conduct a review every six years of existing NPDWRs and determine which, if any, are appropriate for revision. The purpose of the review is to evaluate available information for regulated contaminants to determine if any new information on health effects, treatment technologies, analytical methods, occurrence, exposure, implementation, and/or other factors provides a basis to support a regulatory revision that would improve or strengthen public health protection.
The Six-Year Review is not a final regulatory decision to revise or not revise an NPDWR, but rather the initiation of a planning process that involves more detailed analyses of factors relevant to deciding whether a rulemaking effort to revise an NPDWR should be considered.
Criteria for Revision
For NPDWRs not identified as a candidate for revision, it means that the agency has concluded that it is not appropriate for revision at the time based on available information. The criteria that EPA has applied to help identify when an NPDWR might be considered as a “candidate for revision” are, at a minimum, that the regulatory revision presents a meaningful opportunity to improve the level of public health protection, and/or achieve cost savings while maintaining or improving the level of public health protection.
Exclusion of PFAS Regulations
EPA did not include in this Six Year Review cycle the recently promulgated per and polyfluoroalkyl substances (PFAS) regulations. The PFAS regulations, promulgated in April 2024, established six new NPDWRs. The EPA anticipates that once the PFAS regulations go into effect and sufficient information regarding compliance monitoring becomes available, those NPDWRs will be subject to a more detailed regulatory review under a future Six Year Review cycle.
National Secondary Drinking Water Regulations (NSDWRs)
NSDWRs (or secondary standards) are non-enforceable guidelines regulating 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 with the standard. However, states may choose to adopt them as enforceable standards.
While secondary standards are not federally enforceable, EPA requires a special notice for exceedance of the fluoride secondary standard of 2.0 mg/L. Community water systems that exceed the fluoride secondary standard of 2 mg/L, but do not exceed the primary standard of 4.0 mg/L for fluoride, must provide public notice to persons served no later than 12 months from the day the water system learns of the exceedance (40 CFR 141.208).
| List of National Secondary Drinking Water Regulations | |
| Contaminant | Secondary Standard |
| Aluminum | 0.05 to 0.2 mg/L |
| Chloride | 250 mg/L |
| Color | 15 (color units) |
| Copper | 1.0 mg/L |
| Corrosivity | noncorrosive |
| Fluoride | 2.0 mg/L |
| Foaming Agents | 0.5 mg/L |
| Iron | 0.3 mg/L |
| Manganese | 0.05 mg/L |
| Odor | 3 threshold odor number |
| pH | 6.5-8.5 |
| Silver | 0.10 mg/L |
| Sulfate | 250 mg/L |
| Total Dissolved Solids | 500 mg/L |
| Zinc | 5 mg/L |
Unregulated Drinking Water Contaminants
This list of contaminants which, at the time of publication, are not subject to any proposed or promulgated national primary drinking water regulation (NPDWRs), are known or anticipated to occur in public water systems, and may require regulations under the Safe Drinking Water Act (SDWA).
Conclusion
The Safe Drinking Water Act (SDWA) plays a vital role in safeguarding public health by establishing rigorous standards for drinking water quality. The periodic reviews conducted by the EPA ensure that these regulations remain relevant and effective in addressing emerging contaminants and advancements in treatment technologies. By continuously evaluating health effects, exposure risks, and implementation challenges, the SDWA fosters a proactive approach to water safety.
As the landscape of public health evolves, so too must the regulations that protect it. The commitment to revising and updating national drinking water standards reflects a dedication to improving public health outcomes and maintaining the integrity of water systems across the nation. Ultimately, these efforts contribute to a safer and more reliable drinking water supply, reinforcing the essential role that clean water plays in the well-being of communities.
To explore the latest innovations in water and energy technologies, and discover a wide range of products and solutions from around the world, you can visit the virtual exhibition AQUA ENERGY EXPO which featuring leading companies in water treatment, desalination, and sustainable energy through the following link: https://aquaenergyexpo.com/
Reference
1.Six-Year Review of Drinking Water Standards
https://www.epa.gov/dwsixyearreview
2.Major Elements of Six-Year Review
https://www.epa.gov/dwsixyearreview/major-elements-six-year-review
3.Drinking Water Regulations
https://www.epa.gov/dwreginfo/drinking-water-regulations
4.Drinking Water Regulations and Contaminants
https://www.epa.gov/sdwa/drinking-water-regulations-and-contaminants
