U.S. Environmental Protection Agency


Date of this Version



Published in Cyanobacterial Harmful Algal Blooms: State of the Science and Research Needs, ed. H. Kenneth Hudnell (Springer, 2008).


Two types of approaches may be used to evaluate the toxicity of environmental agents:

• Observational population studies may be used to investigate humans or animals in contact with the agent of interest, either prospectively or retrospectively.
• Experimental studies may be performed under controlled conditions on animals, living tissues or cells. These results may be extrapolated to human and animal populations.

Observational epidemiological studies of human and animal populations have the advantage of investigating the effects of environmentally relevant exposures to naturally–occurring mixtures of toxins. Health effects may be identified in the target species of concern. These studies are difficult to implement however, as monitoring of cyanobacteria toxin occurrence in ambient water is essential to document exposure status, and specific associations between exposure and effect are difficult to establish in free– living populations.