Use the radio buttons to select a toxin or to filter by date range and site type.

Type of Toxin Sampled:
Microcystins Saxitoxin Cylindrospermopsin Anatoxin-a

Time period:
7 days 14 days 30 days 90 days 1 year All

Type of Sampling Site:
PWS Finished Drinking Water PWS Raw Water Intakes
Lakes & Reservoirs Rivers All site types

Range of Toxin Concentrations
detect - 0.29detect - 0.19detect - 0.69detect - 19.99
0.3 - 1.590.2 - 0.790.7 - 2.9920 - 79.99
1.6 - 19.990.8 - 2.993.0 - 19.9980 - 299.99
>= 20.0>= 3.0>= 20.0>= 300
Concentration Units µg/l - micrograms per liter

Site Type by Shape
Public Water System Finished Water Lakes & Reservoirs
Intakes (PWS) Rivers
Markers on the map show sites sampled for the selected cyanotoxin during the selected time period. Marker color indicates that one or more results for that time period were within the range indicated by the marker color. Marker shape indicates the type of sampling site.
Click on the sample site marker to open popup. Click on the name link to view toxin results. To view a different time period of data results, click on the legend tab and select a new time period.

Public Drinking Water thresholds for microcystin and cylindrospermopsin are based on a 10-day exposure.
All threshold values are reported in µg/L.
Type of AdvisoryMYC *ANACYLSAX*
Recreational Public Health Advisory68050.8
Elevated Recreational Public Health Advisory**20300203
Drinking Water: Do Not Drink Advisory
(for bottle-fed infants and children younger than school age)
Drinking Water: Do Not Drink Advisory (for all)1.62031.6
Drinking Water: Do Not Use Advisory20300203

MYC - Microcystins; ANA - Anatoxin-a; CYL - Cylindrospermopsin; SAX - Saxitoxin

*Microcystin and Saxitoxin thresholds are intended to be applied to total concentrations of all reported cogeners of those toxins.
**An Elevated Public Health Advisory will be issued at a public state park beach or boat ramp when cyanotoxin levels are equal to or exceed the Elevated Recreational Public Health Advisory thresholds.

Notes: µg/L - micrograms per liter; ppb - part per billion; the units are identical with respect to the cyanotoxin threshold levels.
This site contains harmful algal toxin monitoring data in Ohio for Public Water Systems and other Ohio EPA monitoring sites*.

The only data included on this site are microcystin, cylindrospermopsin, saxitoxin, and anatoxin-a.

About the data: Public Water Systems monitor for cyanotoxins as required per the HAB Rules (finalized June 1, 2016) and the 2015 Harmful Algal Bloom Strategy. Ohio EPA also monitors inland lakes for cyanotoxins in watersheds being assessed for their Total Maximum Daily Load (TMDL). Ohio EPA-collected samples are analyzed at Ohio EPA's Division of Environmental Services (DES). Data sampled by Public Water Systems are analyzed at either their own lab or a commercial lab.

About the map: The map contains symbols of varying shapes and colors to indicate the site type (i.e., public water system finished water, lake and reservoir) and the concentration range for each toxin. The map is defaulted to show all microcystin results for the past 30 days. This can be changed or refined by choosing a different date range, sampling site type, or toxin. The colors of the symbols relate to the concentration of each toxin for the date range and sampling site type selected.

  • BLUE: The toxin was not detected.
  • GREEN: The toxin was detected but it is below all recreational and drinking water thresholds.
  • YELLOW: The toxin is above a Drinking Water Do Not Drink advisory threshold.
  • ORANGE: The toxin is close to or above the Recreational Public Health advisory threshold.
  • RED: The toxin is above the Recreational No Contact and the Drinking Water Do Not Use advisory thresholds.

To get information about the sites:
  • Zoom in and out of the map using the plus (+) and minus (-) buttons on the upper left hand corner of the map.
  • To zoom to an address or city, type the location in the search box and click on the search icon.
  • To zoom to a specific lake, reservoir or public water system, click on the search drop down and select Lakes, Reservoirs, Public Water Systems.
  • Click on a point. A popup box will show the name of the site and a pie chart indicating the number of samples and the number of toxin detections.
  • Depending on the map scale, there may be more than one sampling site at that point. The upper left hand corner of the popup box will show how many sites are at that location (i.e., 1 of 5). Click on the arrow in the upper right hand corner of the popup box to scroll through all of the sites at that location. Or, you can zoom into the site to separate out the points.
  • Click on the name of the site to see the toxin results. If you have multiple sampling sites, clicking on the arrow will scroll through results from each site.

For more information:

* Map also includes Ohio River water quality data collected by ORSANCO.