Issuing a Public Health Advisory
DPH recommends issuing a public health advisory for HABs at recreational freshwater locations when at least one of the following criteria is met:
- A visible cyanobacteria scum or mat is evident;
- Total cell count of cyanobacteria exceeds 70,000 cells/mL;
- Concentration of the toxin microcystins exceeds 8 µg/L; or
- Concentration of the toxin cylindrospermopsin exceeds 15 µg/L
Guideline values are based on US Environmental Protection Agency (US EPA)1 and World Health Organization (WHO)2,3 recommendations. When issuing an advisory, signage should be posted at each access point at the waterbody warning against any contact with the water.
Rescinding a Public Health Advisory
Cyanobacteria cells can release cyanotoxins into the water when they die. Therefore, algal toxins may be present when a visible scum or mat is no longer evident. DPH recommends the rescinding of a public health advisory after two successive samples, collected a week apart, demonstrate cell counts or toxin levels below the quantitative guideline values.
|Last updated:||May 1, 2021|