Potential Changes To Microbial And DBP Rule

Including THMs and HAAs

EPA Seeks Public Input From Drinking Water Professionals
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The Environmental Protection Agency (EPA) is seeking feedback from the general public and drinking water treatment professionals to inform the possibility of changes to eight National Primary Drinking Water Regulations included in Microbial and Disinfection Byproducts rules following their third 6-year review.

The 8 regulations being looked at are as follows:

  • Chlorite
  • Cryptosporidium
  • Haloacetic Acids
  • Heterotrophic Bacteria
  • Giardia Lamblia
  • Legionella
  • Total Trihalomethanes
  • Viruses

The EPA first held a virtual public event in October, 2020 to;

solicit input on further improving public health protection from (microbial) DBPs in drinking water. Throughout 2021, EPA intends to continue to seek input relevant to any potential rule revisions through a series of public meetings focusing on specific topics identified through public comments and information.”


The Safe Drinking Water Act (SDWA) requires the EPA to review each national primary drinking water regulation at least once every six years and revise them, if appropriate. Revisions must maintain or strengthen public health protection.

The Six-Year Review 3 announcement was not a regulatory decision, but initiated a process involving more detailed analyses of health effects, analytical and treatment feasibility, and other regulatory matters relevant to deciding whether a rulemaking to revise a regulation should be initiated. 

How To Participate:

2021 Virtual Meeting Dates and Topics (Subject to Change) – All Meetings Held From 1:00 – 4:00 PM ET.

  • May 20, 2021: Disinfectant Residual Levels and Opportunistic Pathogens (including Legionella)
  • June 24, 2021: Regulated and Unregulated Disinfection Byproducts
  • (All topics for proceeding months TBD):
  • July 14, 2021
  • August 10, 2021
  • September 1, 2021
  • September 29, 2021
  • November 9, 2021


EPA plans to select future meeting topics based on priority areas identified through current public input. Additional meeting topic examples may include drinking water distribution systems, finished drinking water storage, source water considerations, and consecutive drinking water systems.

EPA appreciates any additional public input to be provided to the docket as soon as possible to help inform the content, focus, and sequencing of the meetings.

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