Drinking Water Health Advisories
The US Environmental Protection Agency (EPA) develops health advisories to provide information on contaminants that can cause human health effects and are known (or anticipated) to occur in drinking water. Health advisories are intended to provide technical guidance to agencies and local officials when contamination situations occur.
Health advisories include levels or limits where health effects are not expected to occur and are updated as necessary. Published health advisory levels are based on non-cancer health effects for specified exposure durations; one-day, ten-day, and lifetime.
One-day and 10-day health advisories are considered acute or short-term levels that are not expected to cause adverse effects for up to one or ten days of exposure. These health advisories are intended to protect a 10-kg (22 pound) child consuming 1 liter of water per day.
Lifetime health advisories are considered chronic or long-term levels that are not expected to cause adverse effects after a lifetime of exposure. These health advisories are intended to protect a 70-kg (154 pound) adult consuming 2 liters of water per day.
Contaminants of Interest
Below is information about a few unregulated contaminants with associated health advisories of current public interest. EPA has finalized over 100 different health advisories.
EPA’s information on drinking water contaminants and health advisories can be found here.
What are cyanotoxins?
Cyanotoxins are toxins produced by some types of cyanobacteria. Cyanobacteria are often referred to as blue-green algae but they are actually bacteria that photosynthesize like algae and plants. Cyanobacteria naturally occur in freshwater environments but, under certain conditions, can reproduce rapidly and form floating mats and dense surface scums commonly referred to as harmful algae blooms (HABs). Cyanotoxins can pose a risk to human health.
EPA is in the process of determining whether to regulate cyanotoxins due to updated health effects information and additional occurrence data. EPA included several types of cyanotoxins on the fourth Unregulated Contaminant monitoring Rule (UCMR4), which requires all public water systems utilizing surface water or ground water influenced by surface water and serving over 10,000 customers as well as selected smaller systems to monitor for certain cyanotoxins.
More information on EPA’s regulatory determination process can be found here.
What are the health advisory levels?
To provide public water system users with a margin of protection from exposure to cyanotoxins in drinking water, EPA established health advisory levels for two cyanotoxins, microcystin and cylindrospermopsin in 2015. When these toxins are found in drinking water, the concentrations should be compared with the health advisory levels.
Table 1: EPA 10-day Health Advisories for Microcystin and Cylindrospermopsin
10-day Health Advisories1
(toxin concentration in micrograms per liter)
|Children (under 6 years old)||School-age Children and Adults (age 6 and older)|
|Microcystin||0.3 μg/L||1.6 μg/L|
|Cylindrospermopsin||0.7 μg/L||3 μg/L|
1. Adverse human health impacts are unlikely to occur over a 10-day period of time.
EPA’s health advisory information for cyanotoxins can be found here.
What are the health effects of cyanotoxins?
Adverse health effects from cyanotoxins depend on many factors, including the type of cyanotoxin(s) present, duration of exposure, and the age and health of the consumer. Cyanotoxins may affect the liver, nervous system, or skin, depending on the toxin. The range of health effects possible from cyanotoxin exposure are skin rashes to liver and nerve damage. No human deaths in the United States have been caused by cyanotoxins; however, pet, livestock, and wildlife deaths caused by cyanotoxins have been reported throughout the United States and the world1.
If you or your family are concerned about your health or have symptoms you think may be caused by cyanotoxin exposure, discuss your concerns with your healthcare provider.
Do public water systems monitor for cyanotoxins?
Since these contaminants are not regulated by EPA as a primary drinking water contaminant, monitoring for cyanotoxins in Idaho public drinking water systems are not required unless the system is part of the fourth Unregulated Contaminant Monitoring Rule (UCMR4), which requires all public water systems utilizing surface water and serving over 10,000 people and selected small systems to monitor. Some systems may voluntarily monitor for cyanotoxins. You may contact your public water system utilizing surface water to find out if they test for cyanotoxins.
How do I remove cyanotoxins from my water?
Do not boil the water. Boiling water will not remove cyanotoxins and will concentrate the toxins.
If your drinking water has been impacted by cyanotoxins and a “Do Not Use” or a “Do Not Drink” order has been issued, use an alternative source of water for drinking.
Point-of-use devices can be used to reduce levels of microcystins. NSF International has developed a test method—NSF Protocol 477: Drinking Water Treatment Units Microcystin—that verifies a water filter’s ability to reduce microcystin to below the health advisory levels set by EPA. A list of drinking water treatment units that reduce microcystins is found here.
Treatment devices require regular maintenance, such as changing filters, cleaning scale buildup, or disinfecting the unit. Failure to properly maintain a unit reduces its effectiveness and, in some cases, may impair the water quality. Continual maintenance and regular water testing are necessary for the life of the device. Follow the manufacturer’s recommendations for replacements and maintenance.
Once a health advisory is removed by your public water system and the drinking water is safe to use, you should flush all of your household plumbing and replace all water filters in the house to remove toxins.
- Run and flush hot water taps for 15 minutes and all cold water taps for 5 minutes.
- Change all filters on point of use units, point of entry systems, refrigerator water filters and membranes for reverse osmosis units.
- Ensure all faucets and plumbed in appliances have been flushed.
More detailed flushing instructions can be found here.
Other frequently asked questions about cyanotoxins:
Is it safe to cook with the water?
No. If a “Do Not Use” or a “Do Not Drink” order has been issued, use an alternative source of water for food preparation where the water is absorbed (e.g., rice or beans) or consumed (e.g., soup). Do not boil the water.
Is it safe to use the water for showering and bathing?
If a “Do Not Use” order has been issued, no. The toxins detected in the water may be harmful to the skin.
If a “Do Not Drink” order has been issued, bathing, swimming, and showering with water that has cyanotoxin levels above the health advisory levels is safe as long as the water is not ingested. Therefore, do not leave small children unattended.
Do not bathe your pet if the cyanotoxin levels are above the health advisory levels. Animals may lick their fur, thereby ingesting toxins.
Is it safe to consume fish caught in water with an active cyanotoxin health advisory?
Potentially. If fish have been exposed to cyanotoxins, only the fillet portion should be consumed.
Is it safe to use the water in a humidifier?
No. If a “Do Not Use” or “Do Not Drink” order has been issued, use distilled or treated water in your humidifier.
Is it safe for my pets to drink the water?
No. If a “Do Not Use” or a “Do Not Drink” order has been issued, the water is not safe for humans or pets to drink.
Is it safe to use the water for my garden?
If the cyanotoxin levels are over the health advisory level, it is not recommended to use the water for food crops. Research indicates that plants can uptake cyanotoxins into their roots from the water and soil.2
Where can I get my water tested?
Laboratories certified to test for cyanotoxins (EPA Method 546) are listed here. Laboratories only analyze cyanotoxin samples if the box “EPA 546” is marked with an "X" next to their names.
- US Environmental Protection Agency.2014. Cyanobacteria and Cyanotoxins: Information for Drinking Water Systems, EPA-810F11001.
- Saqrane, Sana and Oudra, Brahim. 2009. CyanoHAB Occurrence and Water Irrigation Cyanotoxin Contamination: Ecological Impacts and Potential Health Risks. Journal of Toxicology, ISSN 2072-6651.
What is manganese?
Manganese is a common and naturally occurring metal that is found in over 100 minerals. Manganese can be found in soil, air, water, and foods such as many nuts, grains, fruits, tea, leafy vegetables, some infant formulas, and some meat and fish. It is used in the manufacturing process of iron and steel alloys, and as a component in various products such as batteries, glass, gasoline, fertilizers, and fireworks.
Manganese is an essential nutrient for humans and animals and adverse health effects can occur with too little or too much manganese. Adults and children are primarily exposed to manganese through food. Drinking water is also a source of manganese but normally in lower amounts. Exposure to manganese from air is generally less than that from food and water but can vary substantially depending on any industrial sources nearby.
Is manganese regulated?
Manganese is not currently a regulated contaminant in drinking water nationally. Some states have set their own standards for manganese. Idaho has not adopted a drinking water standard for manganese. Manganese is a drinking water secondary contaminant, which means water that is over the secondary standard of 0.05 mg/L is known to cause cosmetic or aesthetic effects, such as a metallic taste, stained plumbing fixtures, and discolored water.
EPA is the process of determining whether to regulate manganese due to updated health effects information and additional occurrence data. EPA included manganese in the fourth Unregulated Contaminant Monitoring Rule (UCMR4), which requires all public drinking water systems serving over 10,000 people and selected small systems to monitor for manganese. EPA will also consider the health effects in their regulatory determination and evaluate potential risks to children and infants based on recent studies (81 FR 81099).
More information on EPA’s regulatory determination process can be found here.
More information on the UCMR4 can be found here.
What are the health advisory levels?
Health advisories provide information on contaminants that can cause human health effects and are known (or anticipated) to occur in drinking water. Health advisories are intended to provide technical guidance to agencies and local officials. In 2004, EPA issued a drinking water health advisory for manganese to provide guidance when the concentrations of manganese in water is above 0.3 mg/L. The EPA manganese health advisory identified a threshold or advisory level of 0.3 mg/L which has a potential to cause health problems in certain populations.
|Health advisories are used for contaminants that are a type of non-enforceable standard. DEQ will require that public drinking water systems provide immediate notification to their customers when manganese results exceed the short term health advisory of 0.3 mg/L. DEQ has the authority to require public notification for situations with significant potential to have serious adverse effects on human health as a result of short-term exposure (Idaho Rules for Public Water Systems, IDAPA 58.01.08.150.02, which incorporates 40 CFR 141.202(a)(9)).|
Health Advisory Levels: 0.3 milligrams per liter (mg/L) and 1 mg/L
Infants younger than 6 months should not consume water that contains manganese over 0.3 mg/L. Formula fed infants are at particular risk since some baby formulas contain manganese as a nutrient and should not be prepared with water that also contains manganese.
EPA established a one-day and ten-day short-term (acute) advisory at 1 mg/L for adults and children. This advisory identifies the concentrations below which potential health problems would unlikely occur for healthy individuals over 6 months old.
EPA also established a lifetime health advisory at 0.3 mg/L. Lifetime health advisories are considered chronic or long-term levels that are not expected to cause adverse effects after a lifetime of exposure. These health advisories are intended to protect a 70-kg (154 pound) adult consuming 2 liters of water per day
EPA’s health advisory information for manganese can be found here.
What are the health effects of manganese?
Adverse health effects from too much manganese depends on many factors, including how much manganese is consumed, a person’s age and current health condition as well as diet and nutritional status (EPA, 2004). Too much manganese can cause harm to the nervous system, resulting in behavioral changes and other nervous system effects, including slow and clumsy movements. Some studies have shown that too much manganese during childhood may also have effects on the brain, which may affect learning and behavior.
Some people may be more sensitive to manganese including bottle-fed infants under 6 months old, as indicated by the short-term health advisory, as well as the elderly and those with liver disease (EPA, 2004).
If you are concerned about your health from manganese exposure, discuss your concerns with your healthcare provider.
Do public water systems monitor for manganese?
Since manganese is not currently regulated by EPA as a primary drinking water contaminant, monitoring for manganese in Idaho public drinking water systems is not required unless the system is part of the fourth Unregulated Contaminant Monitoring Rule (UCMR4), which requires all public drinking water systems serving over 10,000 people and selected small systems to monitor for manganese. Some systems may monitor for manganese voluntarily.
You can contact your public water system to find out if they test the water for manganese. If your water provider does not test for manganese or you have a private well, you can arrange and pay for a certified laboratory to test your water. Certified laboratories are listed on the Idaho Bureau of Laboratories website.
How do I remove manganese from my water?
Boiling water will not remove manganese. Boiling will concentrate manganese.
Consider filtering your drinking water or using an alternate source of drinking water. Oxidizing filters, reverse osmosis units, or water softeners have been shown to be effective at lowering manganese levels in tap water, depending on the form of manganese in your water (dissolved or particulate). NSF International, the Water Quality Association, Underwriters Laboratories, and CSA International all certify home water treatment products for contaminant removal. However, current certifications do not address manufacturer claims for home treatment device manganese reduction.
Any type of treatment device requires regular maintenance, such as changing filters, cleaning scale buildup or disinfecting the unit. Failure to properly maintain a unit reduces its effectiveness and, in some cases, may make the water quality worse. Continued maintenance is necessary for the life of the device along with regular water testing to ensure the device is working properly. Follow the manufacturer’s recommendations for filter replacements and maintenance.
You may choose to reduce your exposure to manganese by using another source of water such as bottled water. However, manganese may still be present in bottled water. Contact the bottled water manufacturer for more water quality information.
EPA (Environmental Protection Agency). 2004. Drinking Water Health Advisory for Manganese. Washington, DC: EPA, Office of Water. EPA 822-R-04-003.
FR (Federal Register). 2016. “Drinking Water Contaminant Candidate List 4—Final Notice.” 81 FR 81099.
Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS)
To provide Americans, including the most sensitive populations such as children and pregnant women, with a margin of protection from exposure to PFOA and PFOS in drinking water, EPA established health advisory levels for both PFOA and PFOS at 70 parts per trillion (ppt). When these two chemicals are found in drinking water, the combined concentrations should be compared with the health advisory level.
EPA’s health advisory information for PFOA and PFOS is found here.
PFOA and PFOS are fluorinated organic chemicals that are part of the perfluoroalkyl family and polyfluoroalkyl substances (PFAS) that do not occur naturally in the environment. These chemicals have been used to make carpets, clothing, fabrics for furniture, and paper packaging for food and other materials (e.g., cookware) that are resistant to water, grease, or stains. They are also used for firefighting at airfields and in a number of industrial processes. Due to the widespread use of these chemicals, most people have been exposed to them.
While consumer products and food are a large source of exposure to these chemicals for most people, drinking water can be an additional source in the small percentage of communities where these chemicals have contaminated water supplies. Contamination is typically localized and associated with a specific facility such as an industrial facility where these chemicals were produced or used to manufacture other products or an airfield where they were used for firefighting.Do public water systems monitor for PFOA and PFOS?
Because these contaminants are not regulated, public water systems are not required to monitor for PFOA and PFOS. Idaho adopts EPA’s national primary drinking water standards, and currently, PFOA and PFOS are not regulated contaminants. Some public water systems have participated in EPA’s third round of the Unregulated Contaminant Monitoring Program, and others may have voluntarily collected samples that included testing for PFOA and PFOS. Information and results from the third round of the Unregulated Contaminant Monitoring Rule (UCMR3) is found on EPA's website.What are the health effects of PFOA and PFOS?
Adverse health effects from PFOA or PFOS depend on the level and length of exposure, and age, lifestyle, and health of the consumer. Adverse health effects may include developmental effects to fetuses during pregnancy or to breastfed infants (e.g., low birth weight, accelerated puberty, and skeletal variations), cancer (e.g., testicular and kidney), liver effects (e.g., tissue damage), immune effects (e.g., antibody production and immunity), thyroid effects, and other effects (e.g., cholesterol changes).
EPA’s health advisory level of 70 ppt was developed based on drinking water consumption of pregnant women who drink water more than other people. The health advisory offers protection against adverse health effects for the most sensitive populations including developing fetuses, breastfed infants, and other children regardless of age and length of exposure. If you or your family are concerned about your health or have symptoms you think may be caused by PFOA or PFOS exposure, discuss your concerns with your healthcare provider.How do I remove PFAS from my water?
If the PFOA or PFOS level in your drinking water is above the health advisory level, consider using alternate sources of water for drinking or installing a point-of-use device. PFOA and PFOS cannot be removed from water by boiling. Reverse osmosis home filtration units have shown the greatest removal potential. Granular-activated carbon may also be effective in removing PFAS. Point-of-use units can be installed under a sink, or point-of-entry units can be installed at your home’s main water line.
Look for units labeled as effective for removing pesticides and volatile organic compounds. We recommend units certified through third-party organizations that test the units for chemical reduction claims. These units will have a certification label from organizations such as the National Sanitation Foundation, Underwriters Laboratory, and Water Quality Association.
Any type of treatment device requires regular maintenance, such as changing filters, cleaning scale buildup, or disinfecting the unit. Failure to properly maintain a unit reduces its effectiveness and, in some cases, may make the water quality worse. Continued maintenance is necessary for the life of the device along with regular water testing to ensure the device is working properly. Follow the manufacturer’s recommendations for replacements and maintenance.Can I cook with the water?
If the PFOA or PFOS level in your water is above the health advisory level, consider using alternate sources of water for foods where the water is absorbed or consumed such as soups, rice, and beans. Tap water may be used to wash produce and dishes as very little of this water will be consumed.Can I use the water for showering and bathing?
PFOA and PFOS do not easily enter the body through the skin. Bathing, swimming, and showering with water that has PFOA or PFOS levels above the health advisory values is safe.Can I use the water for laundry?
Very little water remains on clothing and fabric that has been washed. You may use water with PFOA or PFOS levels above the health advisory values for general cleaning and washing your clothing, bedding, and linens.Can I use the water in a humidifier?
If the PFOA or PFOS level in your water is above the health advisory level, use distilled or treated water in your humidifier.Can my pets drink the water?
The health effects from PFOA and PFOS on animals are probably similar to the effects on people. If the PFOA or PFOS level in your water is above the health advisory level, or you are concerned about your pet’s health, use bottled or treated water for drinking and food preparation.Can I use the water for my garden?
At this time, we do not have adequate information to advise. Based on limited information, root vegetables and leafy vegetables may take in PFAS from water and the soil they are grown in, but other types of produce such as grains and fruits may take in less PFAS. Peeling root vegetables may reduce the amount of chemicals that could cling to the vegetables.Where do I get my water tested?
Laboratories certified to test for PFAS (EPA Method 537) are listed here. Please note laboratories can only analyze PFC samples if the box “EPA 537” is marked with "X" next to their names.