Freshwater cyanobacteria periodically accumulate, or bloom, in water bodies across the United States (US). These blooms, also known as cyanobacterial harmful algal blooms (CHAB), can lead to a reduction in the number of individuals who engage in recreational activities in lakes and reservoirs, degrade aquatic habitats and potentially impact human health. In 1998, Congress passed the 1998 Harmful ... [Show full abstract] Algal Bloom and Hypoxia Research and Control Act (HABHRCA) to address CHABs that impacted living marine resources, fish and shellfish harvests and recreational and service industries along US coastal waters. In 2004, as part of its reauthorization, HABHRCA requires federal agencies to assess CHABs to include freshwater and estuarine environments and develop plans to reduce the likelihood of CHAB formation and to mitigate their damage (NOAA 2004). Many federal agencies recognize the potential impacts of CHABs and share risk management responsibilities; an interagency task force was established and charged to prepare a scientific assessment of the causes, occurrence, effects and economic costs of freshwater. The United States Environmental Protection Agency (EPA) has included “cyanobacteria (blue– green algae), other freshwater algae, and their toxins” in its Contaminant Candidate List (CCL) as one of the microbial drinking water contaminants targeted for additional study, but it does not specify which toxins should be targeted for study (EPA 2005b). Based on toxicological, epidemiology and occurrence studies, the EPA Office of Ground Water and Drinking Water has restricted its efforts to 3 of the over 80 variants of cyanotoxins reported, recommending that Microcystin (MC) congeners LR, YR, RR and LA, Anatoxin–a (AA) and Cylindrospermopsin (CY) be placed on the Unregulated Contaminant Monitoring Rule (UCMR) (EPA 2001). The EPA uses the UCMR program to collect data for contaminants suspected to be present in drinking water that do not have health–based standards set. This monitoring supplies information on the nature and size of populations exposed to cyanotoxins through tap water use.