Cyanobacterial toxins, the perception of water quality, and the prioritisation of eutrophication control

Mass growths of cyanobacteria (blue-green algae), leading to the production of blooms, scums, and mats can occur in nutrient-enriched waterbodies throughout the world. Cyanobacterial mass accumulations attract the attention of water authorities and utilities, environmental and health agencies, and water-user groups, since they present water-treatment, supply, conservation, and health problems. The ability of cyanobacterial populations to produce potent toxins and annual examples of associated human and animal health problems have raised the position of cyanobacteria in the priorities for the management and protection of water quality in countries where health problems associated with the toxins have been perceived. This paper reviews the occurrence of cyanobacterial toxins in waterbodies with examples from national and local surveys. Properties of the known cyanobacterial toxins, associated health problems, and the likelihood of further toxins being discovered are discussed. The need for countermeasures to reduce or prevent the undesirable effects of cyanobacterial toxins exists at several levels. Driving forces influencing the perception of this need and the formulation of management measures include increases in eutrophication increasing demands on diminishing resources for drinking, irrigation, and leisure; and the attention of environmental and health agencies. Health hazards presented by cyanobacterial toxins and derived risk assessments are likely to increasingly influence the ranking of eutrophication problems among water quality issues in drinking and recreational waters. (C) 2000 Elsevier Science B.V. All rights reserved.