Addressing public health risks for cyanobacteria in recreational freshwaters: the Oregon and Vermont framework

Toxigenic cyanobacteria, commonly known as blue green algae, are an emerging public health issue. The toxins produced by cyanobacteria have been detected across the United States in marine, freshwater and estuarine systems and associated with adverse health outcomes. The intent of this paper is to focus on how to address risk in a recreational freshwater scenario when toxigenic cyanobacteria are present. Several challenges exist for monitoring, assessing and posting water bodies and advising the public when toxigenic cyanobacteria are present. These include addressing different recreational activities that are associated with varying levels of risk, the dynamic temporal and spatial aspects of blooms, data gaps in toxicological information and the lack of training and resources for adequate surveillance. Without uniform federal guidance, numerous states have taken public health action for cyanobacteria with different criteria. Vermont and Oregon independently developed a tiered decision-making framework to reduce risk to recreational users when toxigenic cyanobacteria are present. This framework is based on a combination of qualitative and quantitative information.