Recreational Exposure to Cyanobacteria

Freshwater and coastal marine waters in many parts of the world are subject to sporadic or chronic overgrowth of cyanobacteria (aka blue–green algae). When people visit these same waterbodies for recreational activities, exposure to cyanobacteria is inevitable. Cyanobacteria are capable of producing a range of structurally and functionally unrelated toxins; contact with these potent natural toxins by cutaneous, inhalation, or oral exposures in untreated waters concerns public health workers and researchers because of the risks of acute and possibly chronic health effects. Reported illnesses range from mild, self-limiting skin rashes and hay fever-like symptoms to severe acute gastroenteritis and a possible human fatality. Ingestion of cyanotoxin-contaminated recreational water is the most hazardous exposure pathway. The potential for exposure to harmful concentrations of cyanotoxins in recreational settings remains real, despite significant methodological constraints that have affected the ability of epidemiological investigations to reliably quantify these risks. Guidelines for recreational exposure to cyanobacteria have been published by the World Health Organization, and have been modified and adopted by regional or national governments of several countries. Management responses to toxic cyanobacterial blooms in recreational waters range from issuing warnings to the public and temporary access restriction to flushing with upstream water reserves and long-term nutrient mitigation.