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Ohio Recreational and Drinking Water HAB Advisories

No fishing sign

When levels of toxic algae become too high in either drinking water or recreational water in Ohio, an advisory may be posted. Advisories are posted in order to protect the health of the public including both humans and animals. More information on the Ohio Harmful Algal Bloom Response Strategy for Recreational Water can be found here.

Expand the sections below to learn more about the different kinds of advisories that may be issued for HABs-contaminated drinking water and HAB-contaminated recreational water. 


Advisories for HAB-Contaminated Recreational Waters

General Informational Signs

White informational signs are posted at state park beaches and boat ramps to help visitors know how to identify a HAB and to be alert and avoid them. These signs contain images of HABs for reference. Download the General Informational Sign (PDF).

Recreational Caution Sign

A recreational caution sign will be posted at a public state park beach when an algal bloom is present but before water tests have been completed. Once this sign is posted, water will be tested for cyanotoxins.  If cyanotoxins are found at or above the recreational threshold; the  Caution sign will be replaced with a Recreational Public Health Advisory. The caution sign may be removed after algal bloom is gone. Download the Recreational Caution Sign (PDF).

Recreational Public Health Advisory

A red Recreational Public Health Advisory sign at a public state park beach when cyanotoxins are equal to or exceed a recreational threshold. The sign advises that unsafe levels of algal toxins have been found, to avoid all contact with the water, and that swimming and wading are not recommended.  Pets should also be kept away from the water. A Recreational Public Health Advisory will remain until cyanotoxin levels are below recreational thresholds. The Advisory (and Boat Ramp Caution) may be removed after two consecutive sample results, taken at least one week apart, are below recreational thresholds. If the bloom is still present, the Caution sign will remain posted. Download the Recreational Public Health Advisory (PDF).

Boat Ramp Caution Sign

A safety green Boat Ramp Caution sign will be posted and removed at public state park boat ramps in conjunction with a Recreational Public Health Advisory. The sign advises that harmful algal toxins have been found along the beach and may be present in other areas of the water body, and to avoid blooms and scums, avoid swallowing the water and keep pets away. The Boat Ramp Caution sign will be removed at the same time as the Recreational Public Health Advisory. Download the Boat Ramp Caution Sign (PDF).


Recreational Advisory Threshold

The table below shows the levels of cyanotoxins used to post the Recreational Public Health Advisory. Note: All values are reported in μg/L (micrograms per liter), which is equal to 1 ppb (part per billion).

Type of Advisory Microcystin Anatoxin-a Cylindrospermopsin Saxitoxin

 Recreational Public Health Advisory


A sign is posted on beaches warning algal toxins at unsafe levels have been detected and that all contact with the water should be avoided.

8 μg/L 8 μg/L 15 μg/L 0.8 μg/L


Ohio Beachguard provides a list of current public health advisories and water quality information for recreational waters. Visit the Beachguard web page. 

Advisories for HABs-Contaminated Drinking Water

Ohio communities and/or public water systems issue two types of Drinking Water Advisories depending upon the level of cyanotoxins in the finished drinking water:

  • A Do Not Drink Advisory for bottle-fed infants and children younger than school age, pregnant women, nursing mothers, individuals with pre-existing liver conditions or who are immunocompromised, and individuals receiving dialysis treatment. 

  • A Do Not Drink Advisory for all people of all ages as well as for pets and livestock.

The table below shows the levels of cyanotoxins from water sample results used to issue each of the two types of advisories. Note: All values are reported in μg/L (micrograms per liter), which is equal to 1 ppb (part per billion).

Type of Advisory Microcystins* Anatoxin-a Cylindrospermopsin Saxitoxins*

Do Not Drink Advisory for:

  • Bottle-fed infants and children younger than school age
  • Pregnant women
  • Nursing mothers
  • individuals with pre-existing liver conditions
  • Individuals receiving dialysis treatment

As a precautionary measure, the elderly and people with compromised immune systems may want to consider using an alternate water source as well.

0.3 μg/L 0.3 μg/L 0.7 μg/L 0.3 μg/L

Do Not Drink Advisory for:

  • All people of all ages
  • Pets
  • Livestock
1.6 μg/L 1.6 μg/L 3.0 μg/L 1.6 μg/L

*Microcystins and saxitoxins thresholds are intended to be applied to total concentrations of all reported congeners/variants of those cyanotoxins.

Precautions During a Drinking Water Advisory

During a drinking water advisory for children under six and sensitive populations, an alternative water source, such as bottled water, should be used for drinking, preparing food, making infant formula, brushing teeth, and making ice for these individuals. 

  • Children six years and younger should be supervised when bathing to prevent accidental ingestion. 

  • Skin irritation, such as a rash may occur from exposure when washing hands and bathing. 

  • Providing a final rinse of skin with uncontaminated water is recommended, especially for items that go into the mouths of infants and children under the age of six years (i.e., teething rings, nipples, bottles, toys, silverware). 

During a drinking water advisory for children and adults, alternative water should be used for drinking (including pets), making infant formula, making ice, brushing teeth and preparing food. 

  • The cautions listed for children under six and sensitive populations listed above still apply. 

  • During a drinking water advisory, healthy individuals may continue to use the water for washing hands, bathing, washing dishes, and doing laundry. 

For all advisories: 

  • Do not boil the water. Boiling the water will not remove the toxins. 

  • You may use water for flushing toilets. 

For public health guidance regarding HABs drinking water advisories in specific settings, including medical facilities, hotels, and schools, click here.