Six-Year Review 3 of Drinking Water Standards
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EPA announced the review results for the Agency’s 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. Read more about these activities.
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).
|Summary of Review Outcomes||Regulated Contaminants|
maximum contaminant levelThe highest level of a contaminant that is allowed in drinking water as delineated by the National Primary Drinking Water Regulations. These levels are based on consideration of health risks, technical feasibility of treatment, and cost-benefit analysis.
1. Contaminants nominated for Integrated Risk Information System (IRIS) assessments per Six-Year Review Protocol.2. Long Term 2 Enhanced Surface Water Treatment Rule (LT2), Filter Backwash Recyling Rule (FBRR), and Ground Water Rule (GWR) also identified as not appropriate for revision at this time. See Section VI.B.4 of the Federal Register notice for additional information on the results of EPA’s review of these regulations.
at this Time2
Due to Recently Completed, Ongoing,
or Pending Regulatory Action
1,2-Dichloroethane (Ethylene dichloride)
Dichloromethane (Methylene chloride)
Total coliforms (under ADWR and RTCR)
Health effects assessment in process (as of December 2015)
or contaminant nominated for health assessment
Polychorinated biphenyls (PCBs)
No new information, NPDWR remains
appropriate after review
2,4,5 -TP (Silvex)
Chloramines (under D/DBPR)
Chlorine (under D/DBPR)
Low priority and/or no
|Candidate for Revision||New Information||
Cryptosporidium (under SWTR, IESWTR, LT1)
Haloacetic Acids (HAA5)
Viruses (under SWTR)