Health Risk Limits Rules for Groundwater
Rulemaking and Guidance History

History of Rulemaking on Groundwater Contaminants

The 1989 Groundwater Protection Act mandates MDH to promulgate Health Risk Limits (HRLs) for contaminants found in Minnesota groundwater. MDH has amended HRLs and methods though rulemaking on several occasions since 1993. Water guidance values for several chemicals have been adopted into rule, repealed, or updated through this process. See the History of Health Risk Limits Rules, by Chemical, 1993 to present (PDF) for a record of the changes to Health Risk Limit values since 1993.

In 2008/2009, MDH made significant revisions to methods used to develop guidance for groundwater contaminants. These new methods were promulgated in 2009. The 2008/2009 Statement of Need and Reasonableness (SONAR) (PDF) for the 2009 HRL rules provides a thorough description of the scientific methods and principles used to develop HRLs. For definitions of terms, see the Health-Based Water Guidance Glossary (PDF).

MDH plans to conduct rulemaking on a biannual basis to regularly promulgate newly developed or updated water guidance.

2021/2023 Rule information

In November 2023, MDH adopted new or updated HRLs for 36 chemicals. Of these, 17 chemicals did not have previous HRLs and 19 chemicals had outdated HRLs that were repealed and replaced with updated HRLs.  In addition, an outdated HRL for n-hexane from 1994 was repealed and not replaced. New Risk Assessment Advice (another type of water guidance) is now available for n-hexane. 

The rules adoption process was completed in November 2023. A list of the new values can be viewed in a History of Health Risk Limits Rules, by Chemical, 1993 to present (PDF) or in the Human Health-Based Water Guidance Table.

2016/2018 Rule information

In late 2018, MDH adopted new or updated HRLs for 21 chemicals. Four chemicals (clothianidin, dinoseb, tetrahydrofuran, and thiamethoxam) had no previous guidance in rule. The other 17 chemicals had water guidance values that were previously adopted in 1993 or 2009. For these 17 chemicals, the outdated values were repealed and the new values replaced the old values.

2014/2015 Rule information

During the 2014/2015 rules revision, MDH added new guidance values for seven chemicals (eight chemicals, if dimethenamid and dimethenamid-p are counted separately) and repealed and replaced outdated guidance for six chemicals.

In addition, a new part, Part 4717.7865, was created to include HRLs for triclosan, per a 2013 directive from the Minnesota Legislature (Laws 2013, chapter 137, article 2, (Clean Water Fund) section 8). Unlike the other contaminants with HRL Rules, triclosan has not been reported in groundwater in Minnesota.

2012/2013 Rule information

During 2012 to 2013, MDH added guidance values for six chemicals and replaced an additional six outdated values with updated values. The outdated guidance values were repealed.

2010/2011 Rule information

In 2011, MDH added 14 new HRL values, repealed 26 outdated HRL values, and replaced eight of the 26 repealed values with updated values. (Fifteen of the 26 repealed values had already been replaced in 2009.) For the remaining three of the 26 repealed values, MDH issued alternate guidance values.

2008/2009 Rule information

Starting in 2001, MDH toxicologists and risk assessors began evaluating the methodology used to calculate HRL values. Their goals were to:

• Provide guidance on new contaminants found in Minnesota groundwater;
• Update existing HRL values with new toxicological research;
• Incorporate advances in risk assessment strategies;
• Reflect changes in values and policy regarding children's environmental health; and
• Respond to the directive in the Minnesota Statutes, section 144.0751 (Health Standards Statute) to protect sensitive subpopulations, particularly infants and children.

During the process, MDH hosted public meetings, coordinated subject matter expert reviews and invited stakeholder participation in developing new methods for creating water guidance. After the discussions, MDH replaced Minnesota Rules, Parts 4717.7100 to 4717.7800 with Parts 4717.7810 to 4717.7900. Rule revision proceedings began in 2008 and the new rule went into effect in 2009.

2007 Maximum Contaminant Level (MCL)-based rules

In separate legislation (Minnesota Session Laws 2007 Chapter 147, Article 17, Section 2., “Water level standards”), the legislature established new HRLs for chemicals that had at that time (in 2007) both a federal Maximum Contaminant Level (MCL) and an MDH HRL. The new HRL would be set at the MCL if the MCL was lower than the HRL. MDH published a list of eleven chemicals and the corresponding new HRL value in the state register in August 2007 and posted the new values on the MDH website. This legislative directive did not involve the rule making steps followed in other years. Six of these chemicals have now been re-reviewed an updated using current MDH methods for creating water guidance values. The remaining five MCL-based HRLs are shown as HRL_MCL in the Human Health-Based Water Guidance Table.

2007 Temporary perfluorochemicals rules

Minnesota Legislation in 2007 (Minnesota Session Laws 2007, Chapter 37, Section 1) directed MDH to adopt Health Risk Limits (HRL) rules for the chemicals perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). The legislation authorized the commissioner to use the good cause exemption process for rulemaking. HRL values of 0.5 μg/L for PFOA and 0.3 μg/L for PFOS were added to the rules in August 2007. The 2007 HRL values were repealed updated in 2009. Another update for these chemicals was completed in 2018.

1993 and 1994 Rule information

In 1993, MDH promulgated methods for calculating Health Risk Limits (HRLs) and derived HRL values for chemicals based on the equation. Additional HRL values were promulgated in 1994. Copies of rulemaking documents are available upon request.