Algal Toxins and Human Health

Abstract

The blue-green algae, more correctly called cyanobacteria, are becoming an increasing problem in fresh, brackish and marine waters. They respond to increased nutrient concentrations in the water, particularly soluble phosphorus, to form water-blooms. Frequently these water-blooms are toxic to livestock, and present a potential hazard to human health. Cyanobacterial neurotoxins include anatoxin-a, a neuromuscular blocking agent; anatoxin-a(s) an antiacetylcholinesterase, and saxitoxins, the paralytic shellfish poisons which block axonal sodium channels. Hepatotoxins include the cyclic peptide toxins microcystin and nodularin, which cause severe liver injury and promote tumour growth and the alkaloid toxin cylindrospermopsin which causes widespread tissue injury, including damage to the gastrointestinal lining, liver and kidneys. Exposure to these toxins can be through recreational activities in lakes and rivers, through the drinking water supply, or through water used in renal dialysis. Examples of human illness from these three sources occur. Water treatment can be developed to extract or destroy the toxins. Human epidemiological studies are needed to support the experimental animal studies in order to refine recommendations for guideline concentrations for cyanobacterial toxins in drinking water.