Rules and Regulations: Drinking Water HABs Response Plan

What is a Health Advisory?

The Safe Drinking Water Act provides the authority for EPA to publish health advisories for contaminants not subject to any national primary drinking water regulation. HALs describe non-regulatory concentrations of drinking water contaminants at or below which adverse health effects are not anticipated to occur over specific exposure durations (e.g., one-day, 10-days, several years, and a lifetime). They serve as informal technical guidance to assist federal, state and local officials, and managers of public or community water systems by providing information on the health effects of and methods to sample and treat these non-regulated contaminants in drinking water. HALs are not legally enforceable federal standards and are subject to change as new information becomes available (US EPA 2015a).

U.S. EPA Health Advisory Levels for
Microcystins, Cylindrospermopsin, and Anatoxin-a

Cyanotoxins are currently not regulated by the U.S. Environmental Protection Agency (EPA) and do not currently have maximum contaminant levels. However, they are on EPA’s Contaminant Candidate List (CCL), and are thereby under consideration for regulation under the Safe Drinking Water Act in the future. In 2015 the EPA established ten-day non-regulatory HALs for total microcystins and cylindrospermopsin (U.S. EPA, 2015b and 2015c). The health advisories identify concentrations at or below which no adverse human health effects would be expected for up to 10 days of exposure. The EPA issued health effects documents for microcystin, cylindrospermopsin, and anatoxin-a along with the 2015 HALs but did not include an acute reference dose for anatoxin-a, as adequate toxicity data were not available at the time. The HALs for microcystin and cylindrospermopsin are given for two separate population groups. The first group includes Infants, Pre-School Children (under six years old), and Susceptible Adults (more susceptible to the health effects of cyanotoxins than the typical adult). The second group includes School-Aged Children (six years and older) and other Adults.

In the interest of human health and safety, the Utah Division of Drinking Water recommends that Public Water Systems use the low-tier HALs (for Infants, Pre-School Children, and Susceptible Adults) as limitations for total microcystins and cylindrospermopsin in drinking water. The advisory levels are shown in Table 1. More Susceptible Group includes pregnant women, nursing mothers, elderly, immune-compromised, and dialysis patients.

Table 1: Drinking Water – Do Not Drink Health Advisory Levels (from U.S EPA)

10-Day Health Advisories Levels


Children pre-school age and younger (under 6 years old) 0.3 µg/L
School-age children (6 years and older) 1.6 µg/L


Children pre-school age and younger (under 6 years old) 0.7 µg/L
School-age children (6 years and older) 3.0 µg/L

* More Susceptible Group includes pregnant women, nursing mothers, elderly, immune-compromised, and dialysis patients.

The Future for Drinking Water Contaminant Regulations

The EPA has proposed ten cyanotoxin variants for inclusion in the next round of monitoring for unregulated contaminants at selected public water systems under the Unregulated Contaminant Monitoring Rule (UCMR4). Inclusion of cyanotoxins in UCMR 4 is a step toward establishment of regulatory limits for these contaminants in drinking water in the future (NHDES 2016).

In addition to microcystins and cylindrospermopsin, Utah Division of Water Quality has confirmed the presence of anatoxin-a and saxitoxin in Utah water bodies. Other cyanotoxins may also be present depending on the type of cyanobacteria found in the water. Many cyanotoxins have yet to be identified.

Several states (MN, OH, VT, OR) have implemented guidance values for anatoxin-a and/or saxitoxin using risk assessment methods and the guidelines provided by the World Health Organization (WHO) for recreational waters. As the presence of those cyanotoxins has been confirmed in Utah water bodies, the State may choose to take a similar route in the future.

The most stringent limits for each state are shown in table 2.

Table 2: Drinking Water Advisory Levels

State – Advisory TypeAnatoxin-a (µg/L)Saxitoxin (µg/L
Minnesota0.1 µg/LNo Data
Ohio20 µg/L0.2 µg/L
Vermont0.5 µg/LNo Data
Oregon0.7 µg/L0.3 µg/L

Until the State of Utah has adopted maximum contaminant levels for cyanotoxins, compliance with the Health Advisory Levels (HALs) by Public Water Systems is voluntary. Although not enforceable, the published HALs are intended to trigger utility actions including increased monitoring, changes in treatment strategies, and public notification of “do not drink/do not boil” advisories (cyanotoxins are not destroyed by boiling). In the event that a Public Water System exceeds the HALs for any cyanotoxin and fails to provide public notification to its customers, the Division is available to provide such notice.

Public Water Systems that detect cyanotoxins in raw water other than those addressed above should continue to follow the treatment and finished water monitoring guidelines recommended in this document. Any public notification should be coordinated with the Division of Drinking Water.