Toxicological Review of Cyanobacterial Toxins: Microcystins Lr, Rr, Yr and La (External Review Draft)

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The National Center for Environmental Assessment has prepared the Toxicological Reviews of Cyanobacterial Toxins: Anatoxin-a, Cylindrospermopsin and Microcystins (LR, RR, YR and LA) as a series of dose-response assessments to support the health assessment of unregulated contaminants on the CCL. The purpose of these documents is to compile and evaluate the available data regarding toxicity of these toxins to aid the Office of Water in regulatory decision making.

The Safe Drinking Water Act (SDWA), as amended in 1996, requires the Environmental Protection Agency (EPA) to publish a list of contaminants which, at the time of publication, are not subject to any proposed or promulgated national primary drinking water regulations, that are known or anticipated to occur in public water systems, and which may require regulations under SDWA. This list, known as the Contaminant Candidate List (CCL), was first published in 1998 and then again in 2005. The 1998 and 2005 CCLs include cyanobacteria (blue-green algae), other freshwater algae, and their toxins as microbial contaminants. In 2001, a meeting was held among EPA, researchers from the drinking water industry, academia and government agencies with expertise in the area of fresh water algae and their toxins. The goal of this meeting was to convene a panel of scientists to assist in identifying a target list of algal toxins that are likely to pose a health risk in source and finished waters of the drinking water utilities in the U.S. Toxin selection was based on four criteria: health effects, occurrence in the United States, susceptibility to drinking water treatment and toxin stability. Anatoxin-a, cylindrospermopsin and microcystins were identified at this meeting as being the toxins of highest priority based on those criteria.


Following the public comment period and external peer review, EPA will incorporate the comments in a Final report to be released in 2007.


U.S. EPA. Toxicological Review of Cyanobacterial Toxins: Microcystins Lr, Rr, Yr and La (External Review Draft). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-06/139, 2006.


Jul 2006Internal Review completed and comments addressed.