Maximum contaminant level (MCL) is an enforceable numeric standard for drinking water contaminants in public water supplies. An MCL is typically enacted by the United States Environmental Protection Agency (U.S. EPA) and then adopted by individual states through state-led rulemaking procedures. U.S. EPA has not yet enacted an MCL for any PFAS. In response, the Illinois EPA has decided to undertake a statewide study of the prevalence and occurrence of PFAS in drinking water in order to aid in the development of Illinois-specific MCLs for certain PFAS.            

As specified in the Illinois Environmental Protection Act (Act), the Illinois Pollution Control Board (Board) is authorized to adopt a state MCL or treatment technique requirements. The Board may adopt a state MCL even in situations where a federal standard has not been set and may adopt more stringent requirements than the federal Safe Drinking Water Act (SDWA) and accompanying regulations. For the Board to consider adoption of a state MCL, Illinois EPA will need to provide scientific data and studies as well as analyses of technical feasibility and economic reasonableness to justify a proposed MCL. This supporting data is required by the Act and the procedural rules adopted by the Board. The scientific data, studies, and analyses will also be necessary for Illinois EPA to defend and enforce the state MCL in a court of law.

Below is an outline of the process required to prepare, develop, and implement an MCL.

Phase 1: Develop the Necessary Science, Data, Technical Feasibility, and Economic Reasonableness

1) Illinois EPA will conduct statewide sampling and analysis of occurrence data to determine the prevalence and occurrence of PFAS in drinking water.Drinking Water.JPG

Public water supplies are comprised of community and non-community water supplies. The Illinois EPA is launching the Statewide PFAS Investigation Network to conduct a sampling initiative to determine the prevalence and occurrence of PFAS in drinking water provided by Community Water Supplies (CWS). Illinois EPA regulates 1,749 CWS (e.g., water supplies owned and operated by municipalities or private companies serving cities and towns) that serve 12,001,944 individuals. The Illinois Department of Public Health (IDPH) regulates 3,785 non-community water supplies (e.g., schools, factories, campgrounds, rest areas) that serve approximately 500,106 customers.

These two state agencies work to assure that all persons served by public water supplies receive water that is safe and adequate in quantity.

In conducting the Statewide PFAS Investigation Network, Illinois EPA will obtain PFAS occurrence data from 1,456 entry points to the distribution systems (finished water) serving all 1,749 CWS. The Illinois EPA intends to use this occurrence data as well as other data and analysis to support the development of MCLs for PFAS.             

2) Illinois EPA will coordinate with IDPH to review and develop the necessary risk assessment and health effects data in support of any proposed state MCLs for PFAS.

Illinois EPA's Office of Toxicity Assessment will coordinate with the IDPH Environmental Toxicology Section to review the scientific literature and apply nationally accepted risk assessment policy and guidance to calculate proposed MCLs. These technical experts will testify in Board hearings and proceedings in support of any proposed state MCLs for PFAS.

3) Illinois EPA will establish the technical feasibility and economic reasonableness of complying with any proposed state MCLs for PFAS.

Such a demonstration will require Illinois EPA to:

  • Research and establish best available treatment technologies to adequately and consistently remove PFAS to levels below the proposed MCLs. Illinois EPA will develop standards for treatment, design, construction, operations and efficacy.
  • Determine any simultaneous compliance concerns or unintended consequences with drinking water regulations or other applicable laws and regulations in Illinois.
  • Research and establish required laboratory analytical methods, sample collection procedures, and Quality Assurance/Quality Control requirements for sample collection and analysis.
  • Ensure adequate laboratory capacity and capability and establish and maintain a state laboratory accreditation program for PFOA, PFOS, and other relevant PFAS. Laboratories must be able to utilize the proper analytical methodology and achieve detection and reporting limits that are below any proposed MCLs for PFAS.  

4) Illinois EPA will conduct an economic impact study for any proposed state MCLs for PFAS.

At a minimum, the economic impact study shall address:

  • The economic, environmental, and public health benefits that may be achieved through compliance with the proposed state MCLs for PFAS.
  • The effects of the proposed state MCLs for PFAS on employment levels, commercial productivity, the economic growth of small businesses with 100 or less employees, and the State's overall economy.
  • The cost per unit of pollution reduced and the variability in cost based on the size of the facility and the percentage of company revenues expected to be used to implement the proposed rules.

Phase 2: Initiate the Proposed Rulemaking Process as prescribed by Act and Board Procedural Rules

The Illinois EPA will work to initiate a proposed rulemaking with the Board to establish state MCLs for PFAS.  Illinois EPA will conduct outreach with stakeholders on proposed PFAS MCLs prior to submitting a formal proposal with the Board. Once Illinois EPA submits a formal proposal, the Board's rulemaking procedures require at least two public hearings and the opportunity for public comment before new regulations are adopted.