Assessing potential health risks from microcystin toxins in blue-green algae dietary supplements

The presence of blue-green algae (EGA) toxins in surface waters used for drinking water sources and recreation is receiving increasing attention around the world as a public health concern. However, potential risks from exposure to these toxins in contaminated health food products that contain EGA have been largely ignored. EGA products are commonly consumed in the United States, Canada, and Europe for their putative beneficial effects, including increased energy and elevated mood. Many of these products contain Aphanizomenon flos-aquae, a EGA that is harvested from Upper Klamath Lake (UKL) in southern Oregon, where the growth of a toxic EGA, Microcystis aeruginosa, is a regular occurrence. M, aeruginosa produces compounds called microcystins, which are potent hepatotoxins and probable tumor promoters. Because M. aeruginosa coexists with A. flos-aquae, it can be collected inadvertently during the harvesting process, resulting in microcystin contamination of EGA products. In fall 1996, the Oregon Health Division learned that UKL was experiencing an extensive M. aeruginosa bloom, and an advisory was issued recommending against water contact. The advisory prompted calls from consumers of EGA products, who expressed concern about possible contamination of these products with microcystins. In response, the Oregon Health Division and the Oregon Department of Agriculture established a regulatory limit of 1 mu g/g for microcystins in EGA-containing products and tested EGA products for the presence of microcystins. Microcystins were detected in 85 of 87 samples tested, with 63 samples (72%) containing concentrations > 1 mu g/g. HPLC and ELISA tentatively identified microcystin-1R, the most toxic microcystin variant, as the predominant congener.