California Guidelines for Cyanobacteria in Recreational Inland Waters - Voluntary

Help is out there for local health agencies, lake managers, park rangers, and the public.

The California Cyanobacterial and Harmful Algal Bloom Network (CCHAB) provides this guidance to assist environmental and public health managers in responding to inland harmful algal blooms (HABs). Inland HABs include blooms occurring in freshwater and estuarine environments. The primary audience for the guidance are public health officials, environmental health officials, resource managers, and other interested persons who require a streamlined approach to address the risks posed by HABs as well as templates for advisory signs.

Participating agencies - State Water Resources Control Board, Office of Environmental Health Hazard and Assessment (OEHHA), and California Department of Public Health (CDPH) - have developed this and are further refining guidelines for addressing human and animal health concerns for cyanobacteria HABs in recreational waters.

Note: This guidance does not address cyanotoxins in drinking water, resources for addressing cyanotoxins in drinking water are found here. This guidance is informational only and does not represent policy or regulation.


Decision Tree

The decision tree was developed to guide users through necessary steps to post and/or de-post advisory signs. To download the decision tree and narrative, click here (PDF).

Figure 1 Decision Tree

Trigger Levels

Table 1 below provides recommendations to post advisory signs based on trigger levels for the following criteria: concentrations of three major cyanotoxins in water, cell count of potential toxin producers, and site specific indicators. These trigger levels were developed to protect human and animal (dogs, livestock) health from cyanobacteria HABs; for more information on how these levels were derived refer to Appendix A - Description of cyanotoxin trigger levels in recreational water bodies. The advisory signs communicate potential risk to the public.

Trigger Levels Download (PDF)

Table 1: Trigger Levels For Human and Animal Health
Action Trigger
Primary Triggers      
 Total Microcystins b 0.8 µg/L 6 µg/L 20 µg/L
 Anatoxin-a Detection c 20 µg/L 90 µg/L
 Cylindrospermopsin 1 µg/L 4 µg/L 17 µg/L
Secondary Triggers      
 Cell Density (Toxin Producers) 4,000 cells/mL -- --
 Site Specific Indicators of CyanoHAB Visible bloom/discoloration, scum, algal mats, satellite imagery. -- --
  1. The primary triggers are met when ANY toxin exceeds criteria
  2. Microcystins refers to the sum of all measured microcystin congeners
  3. Must use an analytical method that detects ≤ 1 µg/L Anatoxin-a

Reporting of Blooms

When a bloom is occurring, it is critical that there is understanding of the cyanobacteria and cyanotoxins present and communication of the potential risk to protect human and animal health. Blooms of cyanobacteria and algae, as well as animal or human illnesses associated with exposure to HAB toxins, are recommended to be immediately reported to the California HAB Hotline. The HAB Hotline is a central reporting hub that is managed by the State Water Resources Control Board (State Water Board) and the information collected by the hotlines is used to maintain a interactive map of current harmful algal bloom reports and advisories on the California HABs Portal.

Reports of potential HAB occurrences and any related illnesses can be reported to the HAB Hotline by using any of the following:

Advisory Signs

English and Spanish versions of advisory signs are provided for download.

  • The PDF downloads provide pre-made signs and space to insert local agency contact information; it is recommended to laminate paper signs or use professional sign printing services.
  • The PowerPoint downloads allow customization of signs by deleting individual icon/text message components that are not appropriate for a specific water body. However, text with each component cannot be changed. Components can be moved to allow more space for local agency contact information (text box at the bottom of each sign). Signs Version 8/5/2016

Supplemental Information – sign and icons (PowerPoint format)

Outreach and Communication

Aside from the placement of advisory signs, other forms of public information and education may be appropriate, including factsheets, press releases, local information on county websites, public service announcements, or social media messages.

Doctors and veterinarians may not be familiar with the symptoms of cyanotoxin exposure in humans, pets, and livestock.  Symptoms of cyanotoxin poisoning may be misdiagnosed without proper information on their acute and chronic effects. Facts sheets should be provided to local doctors, hospitals, clinics and veterinarians with information about the occurrence and symptoms of cyanotoxin exposure. In addition, downstream users of the impacted waterbody should be informed since cyanotoxins can be transported downstream; cyanotoxin transport of 20+ miles have been documented.

Outreach resources are available on California HABs Portal.