Protecting Human Health from Cyanotoxin Exposure During Recreation

The EPA develops criteria to protect people from organisms, such as viruses and bacteria, including cyanobacteria, and their associated toxins in water bodies (e.g., lakes, rivers, beaches).  Swimming and other recreational activities in contaminated water can make people ill.

The EPA's recommended criteria limit certain organisms and their associated toxins in water bodies to protect human health. State and Tribal governments can use the recommended criteria as guidance when setting their own water quality standards to protect human health.

In 2019, the EPA issued final recommended recreational ambient water quality criteria or swimming advisories for two cyanotoxins, microcystins and cylindrospermopsin. The Agency has identified recommended concentrations of these cyanotoxins at or below which human health is protected while swimming or participating in other recreational activities in and on the water. States, territories, and authorized Tribes can consider adopting these recommended criteria into their water quality standards and using them for Clean Water Act purposes. Alternatively, they can use these same values as the basis of swimming advisories for public notification purposes at recreational waters.

^aThese recommendations can apply independently within an advisory program or in WQS. States can choose to apply either or both toxin recommendations when evaluating excursions within and across recreational seasons.

^bAn excursion is defined as a 10-day assessment period with any toxin concentration higher than the criteria magnitude. When more than three excursions occur within a recreational season and that pattern reoccurs in more than one year, it is an indication the water quality has been or is becoming degraded and is not supporting its recreational use. As a risk management decision, states should include in their WQS an upper-bound frequency stating the number of years that pattern can reoccur and still support its recreational use.

For information on cyanobacteria toxin criteria or swimming advisories to protect human health, including technical support for adopting and implementing these in water quality standards or advisory programs, please visit the EPA Recreational Water Quality Criteria (RWQC) webpage:

• Recreational Water Quality Criteria and Methods

The EPA conducts reviews of its current national recommended RWQC every five years. These reviews, including information on the status of existing and future Cyanobacterial Toxin Criteria, can be found at:

• Five-Year Reviews of EPA’s Recreational Criteria