Guidance Values and Standards for Contaminants in Drinking Water - EH: Minnesota Department of Health

Guidance Values and Standards for Contaminants in Drinking Water

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Drinking Water Standards and Guidance

Minnesota Department of Health (MDH) uses and develops different types of guidance for different purposes to protect people’s health from contaminants in drinking water. Drinking water that is contaminated above the standard or guidance may pose some level of health risk to some people drinking the water.

To see state guidance and/or federal standards for contaminants in drinking water:

To see the MDH guidance:

Maximum Contaminant Levels (MCLs)

  • Established By: US EPA
  • Considerations: Health impact, cost and technology of prevention and/or treatment
  • Review: Changes to MCLs are rarely made

All public water systems in Minnesota must meet these standards. For most people, water that meets all MCLs is safe to drink.

MCLs are established through a scientific process that evaluates the health impacts of the contaminant and the technology and cost required for prevention and/or treatment. States are allowed to enforce lower (more strict) standards than MCLs, but are not allowed to enforce higher (less strict) standards. New MCLs or changes to existing MCLs are rarely made.

Maximum Contaminant Level Goals (MCLGs)

  • Established By: US EPA
  • Considerations: Health impact only
  • Review: Changes to MCLGs are rarely made

MCLGs are very protective, even for sensitive populations like infants, children, and others who may be at increased risk of negative health impacts. MCLGs do not consider cost and technology needs of prevention and/or treatment and may be set at levels that are costly, challenging, or impossible for a water system to meet. MCLGs are not enforceable and public water systems in Minnesota are not required to meet these values.

Health Advisories

  • Established By: US EPA
  • Considerations: Non-cancer health impact only
  • Review: Changes to the table of Health Advisories are made every two to three years

Health advisories for contaminants in drinking water are based on non-cancer health effects for different lengths of exposure (one day, ten days, or lifetime). Health advisories provide technical guidance to the US EPA and other public health officials and are not regulatory values.

Health-Based Values (HBVs) and Health Risk Limits (HRLs)

  • Established By: MDH
  • Considerations: Health impact only
  • Review: New or revised guidance for eight to ten chemicals per year

An HBV or HRL is the level of a contaminant that can be present in water and pose little or no health risk to a person drinking that water. HBVs and HRLs are guidance used by the public, risk managers, and other stakeholders to make decisions about managing the health risks of contaminants in groundwater and drinking water. HBVs are updated when significant new information is available. HRLs are guidance values that have been through the Minnesota rulemaking process, which includes at least one public comment period for stakeholders to provide feedback on the proposed guidance values.

HBVs and HRLs do not consider cost and technology of prevention and/or treatment and may be set at levels that are costly, challenging, or impossible for a water system to meet.

Risk Assessment Advice (RAAs)

  • Established By: MDH
  • Considerations: Health impact only
  • Review: Rare; only developed when there is not enough information to develop an HBV or HRL

An RAA can be a level of chemical in drinking water that poses little or no health risk to a person drinking that water, similar to HBVs or HRLs. RAAs can also be a written description of how harmful a chemical is, compared to a similar chemical. RAAs are generally based on more limited information than HBVs and HRLs or use an alternative risk assessment method.

Is Water Safe to Drink if Contaminant Levels Exceed Standards or Guidance?

Public water supplies that exceed MCLs for any contaminant must take action to reduce that contaminant in drinking water. For most people, water that meets all MCLs is safe to drink. Further action to protect health can be taken by a water supplier or citizen at levels below the MCL.

MDH develops its health-based guidance (HRLs, HBV, RAA) by considering health impacts to the most sensitive and most exposed populations across all stages of human development. For additional information see Health-Based Guidance Development Process.

HBVs, RAA, and EPA Health Advisories are developed on a more frequent basis than MCLs, MCLGs, or HRLs, and may also consider more recent information on the health risks of a contaminant. 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.

Minnesota’s public water systems can use health-based guidance as goals, benchmarks, or indicators of potential concern. Some public water suppliers may strive to meet health-based guidance for contaminants for which it is possible and cost effective.

No water is completely free of contaminants. 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. All Minnesotans can use the various guidance values to determine what level of a contaminant in water is acceptable for themselves and their family.

Treatment options may be available to reduce levels of contaminants in your drinking water if testing, either by you or a public water supply, shows that contaminants have been found at levels that are a concern to you. 

Contaminants in Drinking Water

No water supply is ever completely free of contaminants. Drinking water standards protect Minnesotans from substances that may be harmful to their health. Some contaminants, such as arsenic and manganese, occur naturally in our environment. Other contaminants enter our water supplies as a result of our own behaviors. Fertilizer and pesticides in run off from lawns and farm fields, cleaners and personal care products that go down household drains, and industrial leaks or improper waste disposal can all lead to water contamination.

It is normal for people to want their drinking water to be completely free of all contaminants. However, preventing or removing all contamination may not be economically or technologically feasible or necessary to protect our health. US EPA and MDH are responsible for determining the levels of contaminants that can remain in water supplies without threatening human health.

MDH’s Role in Protecting Water Quality

MDH’s scientists includes a wide variety of water quality experts (hydrologists, engineers), research scientists (toxicologists, exposure scientists, epidemiologists), and public health professionals (risk assessors, risk communicators) who work together to assess the public health risks of contaminants in drinking water and monitor drinking water. MDH provides guidance and information about safe drinking water to public water suppliers and private well owners and works with other state and federal agencies, communities, non-governmental organizations, and citizens to protect and maintain Minnesota’s groundwater, rivers, and lakes that are the sources of our drinking water.

A shorter, printable version of this information is also available: Guidance Values and Standards for Contaminants in Drinking Water (PDF).

Partners in Safe Drinking Water

The United States Environmental Protection Agency (US EPA), the Minnesota Department of Health (MDH), public water systems, and citizens work in partnership to keep our drinking water clean and safe for all Minnesotans.

The 1974 federal Safe Drinking Water Act directs the US EPA to set national drinking water standards for naturally occurring and man-made contaminants in public drinking water. These standards represent legally enforceable limits. MDH enforces these drinking water standards for public water systems in Minnesota.

Public water systems regularly test drinking water supplies. Public water supplies must meet the drinking water standards set by the Safe Drinking Water Act. Results of this testing are available to each customer through an annual consumer confidence report.

The 1989 Groundwater Protection Act directs MDH to develop health-based guidance values for groundwater that is used for drinking water. These values are used by state programs to protect people and the environment. These values are especially important when no other guidance value is available.

In Minnesota, private well construction is regulated by MDH and a water test for bacteria, nitrate, and arsenic is required when a new well is constructed. After that initial test, the well owner is responsible for well maintenance and testing their drinking water.

Every Minnesotan has a role in protecting our drinking water resources. Using water wisely, preventing contamination, and planning for future needs will help provide clean, healthy water for generations of Minnesotans.

Updated Tuesday, 26-Jul-2022 08:55:08 CDT