Health-Based Guidance for Water
Health-based guidance for water is a concentration of a chemical (or a mixture of chemicals) in drinking water that is likely to pose little or no health risk to humans. The values are expressed as micrograms of chemical per liter of water (μg/L), which is the same as parts per billion (ppb).
MDH Health Based Guidance for Water can be found in the Human Health-based Water Guidance Table.
MDH develops three types of guidance for water:
- Health Risk Limits (HRLs), which are promulgated guidance values adopted through a formal rulemaking process authorized in the 1989 Groundwater Protection Act.
- Health Based Values (HBVs) are developed as interim guidance until MDH can adopt an HRL through rulemaking. HBVs meet the same data requirements as HRLs. If a contaminant has been detected in groundwater, then HBVs for water may become HRLs at the time that MDH next amends the Health Risk Limits for Groundwater rule.
- Risk Assessment Advice (RAA) may be based on more limited data than HRLs, or may use new methodology. RAA may include a numerical value or may be qualitative in nature.
These guidance values constitute MDH’s recommendations for general use in risk assessment. However, it is understood that risk assessors and risk managers will exercise discretion in applying MDH guidance to specific sites and exposure situations.
For additional information see Health-Based Guidance Development Process.
At times, an old HRL value and a newer guidance value may be available for the same chemical. For an explanation, please see Dual Guidance for Drinking Water.
In situations where a sample of groundwater contains multiple chemicals, MDH evaluates exposure to multiple chemicals using an additivity model. For more information, see: Evaluating Concurrent Exposures to Multiple Chemicals.