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Ground Water and Drinking Water

Additional Information about Cyanotoxins in Drinking Water

U.S. EPA Cyanotoxin Drinking Water Health Advisories

Under the SDWA, EPA may publish Health Advisories (HAs) for contaminants that are not subject to any national primary drinking water regulation 42 § 300g-1(b)(1)(F)EXIT. EPA develops HAs to provide information on the chemical and physical properties, occurrence and exposure, health effects, quantification of toxicological effects, other regulatory standards, analytical methods, and treatment technology for drinking water contaminants. HAs describe concentrations of drinking water contaminants at which adverse health effects are not anticipated to occur over specific exposure durations (e.g., one-day, ten-days, several years, and a lifetime). HAs also contain a margin of safety to address database uncertainties. HAs serve as informal technical guidance to assist federal, state and local officials, as well as managers of public or community water systems in protecting public health when emergency spills or contamination situations occur.

In 2015, EPA developed Health Advisories (HA) for the cyanotoxins, cylindrospermopsin and microcystins:

These HAs are not regulations and should not be construed as legally enforceable federal standards. HAs may change as new information becomes available.

Cyanotoxin Drinking  Water Health Advisory (10-day)
Bottle-fed infants and pre-school children School-age children and adults
Cylindrospermopsin 0.7 µg/L 3 µg/L
Microcystins 0.3 µg/L 1.6 µg/L

EPA also developed Health Effect Support Documents (HESD) for the following cyanotoxins: anatoxin-a, cylindrospermopsin and microcystins. The HESDs constitute a comprehensive review of the published literature on the chemical and physical properties of these toxins, the toxin synthesis and environmental fate, occurrence and exposure information, and health effects.

As a companions to the HAs, EPA also developed a support document entitled Recommendations for Public Water Systems to Manage Cyanotoxins in Drinking Water for states and utilities to assist them as they consider whether and how to manage cyanobacterial toxins in drinking water. The recommendations in this document are intended to assist public drinking water systems (PWSs) manage the risks from cyanobacterial toxins in drinking water, including information and a framework that PWSs can consider in their cyanotoxin risk management efforts.

Several U.S. states have implemented standards or guidelines that apply to cyanotoxins in drinking water. For more information on the state-specific standards or guidelines, contact your state environmental or public health department; a list of state health and environmental agencies is available here

Safe Drinking Water Act: Drinking Water Protection Act, CCL and UCMR

Drinking Water Protection Act

EPA developed, and submitted to Congress, a strategic plan outlining how the agency will continue to assess and manage algal toxins in drinking water provided by public water systems. The strategic plan outlines approaches and projects to better understand human health impacts from cyanotoxins, control and manage algal toxins in source water, and treat algal toxins in drinking water, with the goal of ultimately protecting water quality and public health. EPA developed this strategic plan in response to the 2015 Drinking Water Protection Act (also known as H.R. 212).

Contaminant Candidate List (CCL)

The Safe Drinking Water Act (SDWA), as amended in 1996, requires the EPA to publish a list of contaminants every five years that are known or anticipated to occur in public water systems and which may require regulation under the SDWA. This list is called the Contaminant Candidate List (CCL). The EPA's Office of Water listed cyanobacteria (formerly known as blue-green algae), other freshwater algae and their associated toxins on CCL 1 (1998) and CCL 2 (2005). Cyanotoxins were included on CCL 3 (2009) and the CCL 4 (2016). Based on toxicological, epidemiological and occurrence studies, the cyanotoxins anatoxin-a, cylindrospermpsin, microcystins and saxitoxin were listed as examples of cyanotoxins of concern.

Fourth Unregulated Contaminant Monitoring Rule (UCMR 4)

The 1996 Safe Drinking Water Act (SDWA) amendments require that once every five years EPA issue a new list of no more than 30 unregulated contaminants to be monitoried by public water systems. The fourth Unregulated Contaminant Rule (UCMR 4) was published in the Federal Register on December 20, 2016. UCMR 4 requires monitoring for 30 chemical contaminants, including cyanotoxins, between 2018 and 2020 using analytical methods developed by EPA and consensus organizations.