Recreational Health Advisory Guidance:
Harmful Algal Blooms

There are no official regulatory or health-based standards for safe levels of cyanobacteria or toxins in recreational waters. However, the Environmental Protection Agency (EPA) has developed a Draft Human Health Recreational Ambient Water Quality Criteria and/or Swimming Advisories for Microcystins and Cylindrospermopsins to protect the public from incidental ingestion of these two cyanotoxins during primary-contact recreation such as swimming.

Guidance Documents

Health Advisory Decision Diagram. Click for larger view.

In the absence of regulatory standards, the Utah Department of Health (DOH) and Utah Department of Environmental Quality (DEQ) adopted Recreational Health Advisory Guidance based on ambient water-quality criteria recommended by the World Health Organization (WHO), US EPA, and other US States to protect human health and safety. DOH and DEQ developed this Guidance to help local health departments (LHDs) determine if a health advisory is warranted for a waterbody experiencing a harmful algal bloom (HAB).

This Guidance identifies four independent indicators to protect recreational users from adverse health effects from HABs:

  1.  Cyanobacteria cell concentrations
  2.  Microcystins
  3.  Cylindrospermopsin
  4.  Anatoxin-a

If any of these indicators is exceeded, a recreational health advisory is recommended. The Guidance also provides a multi-tiered approach to public-health advisories.

Public Health Advisory Tiers. Click for larger view.

Tier 1

At this level, providing information to recreational users is considered sufficient. Indicator levels:

  • Cyanobacteria cell counts less than 20,000 cells per milliliter (cells/ml)
  • Microcystins levels below 4 micrograms per liter (µg/L)
  • Cylindropspermopsin levels less than 8 µg/L
  • Anatoxin-a levels non-detect

Tier 2

At this level, a WARNING public-health advisory is recommended. Indicator levels:

  • Cyanobacteria cell counts between 20,000 and 10,000,000 cells/ml OR
  • Microcystins levels between 4 and 2,000 micrograms per liter (µg/L) OR
  • Cylindrospermopsin levels greater than 8 µg/L OR
  • Anatoxin-a levels from detection to 90 µg/L

Tier 3

At this level, a DANGER public-health advisory is recommended. Consider closure of the affected waterbody. Indicator levels:

  • Cyanobacteria cell counts greater than 10,000,000 cells/ml OR
  • Microcystins levels greater than 2,000 µg/L OR
  • Cylindrospermopsin levels greater than 8 µg/L OR
  • Anatoxin-a levels greater than 90 µg/L

Health Advisories and/or Beach Closures

DOH and DEQ recommend that local health departments (LHDs) use the table and accompanying decision algorithm when determining the appropriate level of health risk and public-health action for a given waterbody. If an LHD receives reports of human or animal illness or death that is plausibly linked to cyanobacteria, an immediate public health advisory is recommended.

Once an advisory is issued, the Guidance recommends at least two weeks of measurements indicating that the hazard has passed before removing the advisory.

The HABs Communication Workgroup has developed the following WARNING and DANGER signs that LHDs may use when issuing a health advisory.

Guidance for Waterbody Sampling

The recommended standard operating procedure (SOP) for collecting samples for HABs and HAB toxins are described in the Division of Water Quality’s Standard Operating Procedure for the collection of Phytoplankton Samples during Harmful Algal Blooms. Excerpts from the SOP:

Guidance for Fish and Wildlife Mortality Sampling

The recommended standard operating procedure (SOP) for collecting samples for carcasses of fish and wildlife associated with a HAB event is described in the USFWS and DWQ Guidance for Fish and Wildlife Mortality Sampling.

Fish Consumption from High Cyanobacteria Count Areas

Cyanotoxins can accumulate in fish in waters with high toxin levels. The highest concentrations are in the organs (particularly the liver) and fat deposits. Muscle tissue typically has lower toxin levels. Fish taken from waters with intermittent blooms such as occur in Utah are unlikely to have toxin levels in muscle that present a health concern. However, there remains considerable uncertainty.

UDOH and UDEQ recommend carefully cleaning and thoroughly cooking fish harvested from waters where cyanobacteria are present. This includes discarding the guts and skin, eating only the fillets, and rinsing the meat in clean water before cooking.