Frequently Asked Questions about MDH Water Guidance

This page provides answers to frequently asked questions about Human Health-Based Water Guidance. For questions or additional information, contact the Health Risk Assessment Unit.

On this page:
What is Human Health-Based Water Guidance?
How are the water guidance values used?
How are MDH water guidance values developed and updated?
How do MDH water guidance values protect my health?

What is Human Health-Based Water Guidance?
Human Health-Based Water Guidance is a concentration of a chemical (or a defined mixture of chemicals) in water that are likely to pose little or no risk to human health. There are currently three types of health based water guidance, including Health Risk Limits (HRL), Health Based Values (HBV), Risk Assessment Advice (RAA). All three values are stated in micrograms of chemical per liter of water (µg/L), which is the same as parts per billion (ppb). The guidance values developed since 2008 utilize methodology designed to account for highly exposed populations and different durations of exposure (e.g., one day, up to 30 days, more than 30 days or 10% of a lifetime, or more than 10% of a lifetime).

All of the health-based water guidance values are based solely on health effects information. Other factors such as the ability to detect or monitor a chemical, the cost of controlling a chemical, or background concentrations of a chemical are not considered in their development.

How are the water guidance values used?
The water guidance values are used by the Minnesota Department of Health and other state agencies, such as the Minnesota Pollution Control Agency (MPCA) and Minnesota Department of Agriculture (MDA), to assist in the assessment of potential health risks from exposures to chemicals in water. The Health-Based Water Guidance Values can be used for assessing risks in the environmental review process, issuing water permits, risk assessments and other site-specific assessments. The application of Human Health-Based Water Guidance is not specified in Minnesota rule.

It is important to note that the absence of a chemical from any of the health-based value lists does not imply that there are no health risks associated with occurrence of the chemical in water.

How are MDH water guidance values developed and updated?
The water guidance values are developed using the best peer-reviewed science and public health policies available at the time of their development and are based on the U.S. Environmental Protection Agency (US EPA) guidelines. New guidelines are developed or existing values are updated when new data becomes available. For more information, see the Health-Based Guidance Development Process and Chemicals Under Review.

How do MDH water guidance values protect my health?
MDH water guidance values are developed using methods to ensure that exposure to an individual chemical in drinking water, or mixture of chemicals, will not result in an adverse health effect. The values are intended to protect the health of most individuals, including at-risk and susceptible individuals (including but not limited to children, pregnant women and their fetuses, individuals compromised by pre-existing diseases, and elderly persons). However, guidance values may not be protective of every individual. Health-Based Water Guidance Values are not necessarily protective of hypersensitive individuals who may respond to low level chemical exposures.