Drinking Water Risk Communication Toolkit
Make Your Message

Visit the MDH page Per- and Polyfluoroalkyl Substances (PFAS) for information, factsheets, and messaging about health risks, PFAS testing in drinking water, and exposure to PFAS. Examples from systems include:

• Addressing PFAS in Drinking Water, from the city of Woodbury.
• PFAS, from the city of Hastings.

Other PFAS risk communication resources include:

• PFAS Risk Communications Hub (Environmental Research Institute of the States).
• PFAS Risk Communication (Interstate Technology Regulatory Council).

Drinking Water Cyanotoxin Risk Communication Toolkit

The drinking water cyanotoxin risk communication toolbox is a ready-to-use, “one-stop-shop” to support public water systems, states and local governments in developing, as they deem appropriate, their own risk communication materials. It includes editable worksheets, social media posts and other quick references. The materials focus on communicating risk and providing background information to the public prior to and during a drinking water cyanotoxin contamination event as well as general information on harmful algal blooms and cyanotoxins.

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

In addition to the standards set by the SDWA, MDH toxicologists develop health-based guidance values for contaminants in water. There are several types of health-based guidance developed by MDH, which are protective for the most sensitive and/or highly exposed populations. Health-based guidance values are based only on the potential health impacts and do not consider the technology available or cost associated with prevention and/or treatment. Therefore, health-based guidance values may be challenging for a water system to meet.

See Guidance Values and Standards for Contaminants in Drinking Water (PDF) for more information about drinking water values.

No water supply is ever completely free of contaminants. Drinking water standards protect Minnesotans from substances that may be harmful to their health. 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.

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.

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.

For more information: Guidance Values and Standards for Contaminants in Drinking Water

Health based guidance values (HBGVs) are set at levels which pose little or no health risk to people, including the most sensitive populations like a fetus, infants, children, elderly, and people with impaired immunity. Although the potential for harm increases as the level of a contaminant increases above the HBGV, health scientists may not be able to precisely estimate the change in risk.

Contact MDH for more information about specific contaminants.

• HBGVs include MDH Health Risk Limits, Health-Based Values and Risk Assessment Advice.
• HBGVs account for the different amounts of water people drink and the different sensitivities people have to a chemical following exposure.
• HBGVs include factors to account for uncertainties in our understanding of the health risks posed by a chemical.
• HBGVs are contaminant specific.
• HBGVs include a variety of different factors; therefore, the risk can vary from contaminant to contaminant.
• HBGVs are based on current scientific knowledge and are re-evaluated as new information becomes available.

As we learn more, the science we use to support the work of drinking water protection can evolve over time. We use the best information we have at any given time to do our work.

As investigative methods and knowledge change, sometimes conclusions about the risk of contaminants change. Consumers may interpret these changes as uncertainty or confusion. It can also incorrectly lead consumers to think that the previous conclusions were 'wrong.' It is important to discuss the fluidity of science.

Consumers may not fully understand the reasons for these changes and that the science exists on a continuum of certainty. Scientific uncertainty causes frustration for the public and activates their fears of the unknown. (Consumer Perceptions and Attitudes Toward EDCs and PPCPs in Drinking Water. Water Research Foundation. 2013.)

It is also important to distinguish between this uncertainty and risk variability. Risk variability is when the risk is different across the population (for example, a contaminant may pose a higher health risk during development or early life), but that variability is well-known. (Consumer Perceptions and Attitudes Toward EDCs and PPCPs in Drinking Water. Water Research Foundation. 2013.)

Contaminant level above the Maximum Contaminant Level (MCL) (does not meet Safe Drinking Water Act standards): Drinking water with a contaminant level above the MCL (does not meet Safe Drinking Water Act standards) poses a health risk to people. Your public water system will work to address the issue. You will be notified if you need to take action.

Contaminant level below the MCL (meets Safe Drinking Water Act standards) but above health-based guidance: Drinking water that meets Safe Drinking Water Act standards is safe to drink for most people. People of a certain age or with special health conditions - like a fetus, infants, children, elderly, and people with impaired immunity – may need to take extra precautions.

Contaminant level below the MCL and health-based guidance: Drinking water that meets Safe Drinking Water Act standards and health-based guidance is safe to drink. It poses little or no health risk to people, including the most sensitive populations - fetuses, infants, children, elderly, and people with impaired immunity.

Just because a contaminant is detected in water, it does not mean that harmful health effects will occur. Many factors play a role in whether or not a contaminant is harmful, especially:

• Dose: amount of a contaminant a person receives.
• Duration: how long a person is exposed to a contaminant.
• Whether the contaminant poses risks for short-term ("acute") or long-term ("chronic") health effects.

Contaminants that can cause short-term health effects within hours or days of exposure are called acute contaminants. Examples of acute contaminants include microbes such as E. coli and Cryptosporidium.

Contaminants that can cause health effects after regular, long-term exposure even to very low levels of the contaminant are called chronic contaminants. Examples include arsenic, pesticides and industrial chemicals, and radium. Exposure to chronic contaminants early in life may increase a person’s risk of health effects.

Scientists use a process called risk assessment to estimate the level of a contaminant that might be harmful to humans. The process combines information about the toxicity of the contaminant with information about how often a person is exposed. Risk assessments conducted at MDH also consider especially vulnerable populations or life stages where a contaminant’s effects might be more severe.

(Adapted from Pharmaceuticals and Endocrine Disrupting Compounds in Water: A Primer for Public Outreach; Water Research Foundation. 2015.)

If you have just found out about an exposure to contaminants in drinking water in your community, you may be concerned about your exposure to this contaminant before you were notified.

Here is information to consider:

• Guidance values are meant to protect most people.
• When contamination in drinking water exceeds these values, it is rare to be able to go back to the past and predict the risk to people who were exposed by using the water. Usually, we don’t have adequate knowledge about what people were exposed to and for how long people were exposed.
• This doesn’t mean that harmful effects will occur due to past exposures, just that we can’t usually predict much without information. We can say that the farther above the guidance values, the greater the risk that an effect might occur.
• All that is possible in such cases is to use available tools and information to provide safe drinking water options for the community.

Climate change impacts should be considered in all drinking water planning and operations in Minnesota.

Rising temperatures and dew points are causing changes in the amount, timing, and intensity of rain and snow. Minnesota is experiencing an increase in average annual precipitation and heavier, more localized rainfall events. These intense, local rainfall events mean some Minnesotans will experience more heavy rain and flooding, while others will face severe drought and risk of wildfires. In Minnesota today, 37% more rain comes from heavy rainfall events than it did 50 years ago.

In terms of water quality, heavy rainfall events can wash contaminants such as E. coli and Cryptosporidium into drinking water sources. Contaminated drinking water or water used for recreation can cause illness in individuals and even community outbreaks. In terms of water availability, drought can increase competing demands for water resources and lead to resource challenges, ultimately causing financial and social strain in communities.

Resources related to climate change and drinking water:

• DNR: Climate’s impact on water availability
• DNR: Climate data
• MDH Climate and Health: Water Quality and Quantity

Public health often refers to risk in terms like “1 in 10,000” or “1 in 100,000.” We use these phrases to describe the current level of risk, a limit of acceptable risk, or the increased risk of a negative health outcome due to exposure to something harmful, like a contaminant in drinking water. Using ratios like “1 in 10,000” is also a risk communication strategy that relies on using whole numbers rather than decimals because people understand whole numbers better. A 1 in 10,000 risk is the same as 0.01 percent.

But what does the ratio mean when less than 10,000 people are exposed to a contaminant? Does it mean that no one will be impacted?

Not quite. The ratio is a measure of universal, incremental risk. It indicates that everyone in a population exposed to a certain level of harm (in the case of drinking water, a certain level of a contaminant) has an increased risk of experiencing the negative health outcome.

You might think of it a bit like drawing straws. In 10,000 straws, one is short (this represents the likelihood of a negative health outcome) and everyone exposed to a harmful contaminant is drawing one straw. Even if not all 10,000 straws are drawn, everyone has a chance of drawing the short straw. The risk is not zero.

Groundwater can contain multiple chemicals. Combinations of chemicals may cause health effects that are different from the health effects of each individual chemical. MDH evaluates the health effects of groups of chemicals using the following process:

MDH has an MDH Water Guidance and Additivity Calculator (Excel) that can be used to conduct the cumulative/mixture evaluation. It is located immediately above the Water Guidance Table.

MDH uses procedures stated in the Health Risk Limits (HRLs) Rules for Groundwater for evaluating exposure to multiple chemicals. This process is based on an additive model. The U.S. Environmental Protection Agency (EPA) uses this model as a reasonable approach given what is unknown about how chemicals interact in the body.

• Chemicals that share a common health endpoint (such as change to the liver, kidney, or other organ) are evaluated together. If a chemical has no known health effect, it is not included in the group.
• For each chemical in the group, MDH calculates a ratio of the groundwater concentration of the chemical to the health-based guidance value appropriate to the length of exposure for that chemical. MDH adds the ratios for all of the chemicals in the group to create a number called a Health Risk Index (HRI).
• An HRI over one indicates a possible health risk from the group of chemicals.

More information is found on the MDH webpage Evaluating Concurrent Exposures to Multiple Chemicals.