Dual Guidance for Drinking Water

Water quality studies and monitoring in Minnesota find contaminants from products or sources we never suspected in places we never expected, like our lakes, rivers, groundwater and drinking water. These emerging contaminants are found because:

• improved research methods allow us to look for new chemicals at lower levels than previously possible;
• industry and individuals are using new chemicals in a variety of products and applications; and
• old chemicals are being used in new ways.

The work of the Contaminants of Emerging Concern (CEC) Initiative helps the Minnesota Department of Health (MDH) understand the potential health effects of these contaminants.

In support of our mission to protect the health of all Minnesotans, MDH scientists find the amount of a contaminant in water that will not harm a person who drinks it and shares the results of this research with the public. This amount of contaminant is called “health-based guidance.” MDH lists guidance values in the Human Health-Based Water Guidance Table.

Some guidance values for contaminants that have been found in Minnesota groundwater can also be promoted as a rule (the Health Risk Limits for Groundwater rule or HRLs). Rulemaking occurs approximately every two years. Guidance is developed in-between rulemaking and may update an older rule. As a result, both rules and guidance values may be available for a contaminant and the two values may be different. This is called having dual guidance.

MDH is currently publishing both HRL rule values and newer guidance values (Health-Based Values or Risk Assessment Advice) on the MDH website in the Human Health-Based Water Guidance Table. Both values are available and useful for risk evaluations and risk management. For descriptions of the differences and similarities between values adopted into rules and MDH guidance, please visit: Minnesota Guidance.

Displaying both the old HRL value and new guidance for a chemical is temporary. At the first rulemaking opportunity MDH aims to either replace the old value with a new HRL value or repeal the old value without replacement. Once the new rule is promoted the guidance table will show only the new HRL value or the guidance if no new HRL was promoted, and this chemical will no longer have dual advice. However, as MDH continues to reevaluate existing HRLs for more chemicals, new guidance will be found and posted. MDH expects that the guidance table will always include a few chemicals that will have both an old HRL value and a new guidance.

All guidance values (HRLs, Health-Based Values, and Risk Assessment Advice) are available to state programs. Some state regulatory programs may be restricted to using HRLs or prefer to use HRLs because the values are promulgated into rule. MDH guidance is only one of many considerations that risk management programs use to determine fitting responses to contamination issues. In particular, site-specific situations may raise questions for the risk manager regarding which value to apply. When choosing one value over another, it’s important to know the reason why a newer value was developed or know the populations at risk and how each value protects those populations. While the selection and use of values is the responsibility of programs that are applying MDH rules and guidance, our staff are available for consultation concerning the basis and potential use of MDH values.

Spotlight

Subscribe to receive notification when reviews are initiated for water contaminants, and other announcements.

Chemical(s) Under Review: MDH reviews information about chemicals in response to requests for assistance and guidance from programs within MDH and from other state agencies.

Guidance Development Process: MDH has developed a guide with information about the guidance development process.