Risk assessment of microcystin in dietary Aphanizomenon flos-aquae

Aphanizomenon flos-aquae, a cyanobacterium that is marketed as a health foo d supplement, is harvested from natural blooms in Klamath Lake (Oregon) tha t are occasionally contaminated by Microcystis spp. Regulatory agencies in several countries are developing regulations to control the amount of micro cystin in drinking water and other products, including products produced fr om A. flos-aquae. Regulation of microcystin (MC), a toxin produced by Micro cystis spp. that is potentially present in natural culture of A. flos-aquae , should be based on studies in which a test species is exposed to the natu ral mixture of these cyanobacteria. A 1984 feeding trial to determine the e ffects of high dietary levels of A. flos-aquae on reproduction and developm ent of mice is reanalyzed in light of recent analyses for microcystin-LR (M CLR) in the diets of those mice. Young adult mice consuming up to 333 mu g MCLR/kg body weight (bw)/day exhibited no adverse effects on growth and rep roduction, fetal development, and survival and organ weights of neonates. B ased on a NOAEL of 333 mu g MCLR/kg bw/day, a safety factor of 1000, consum ption of 2 g/day of A. flos-aquae by a 60-kg adult, the safe level of MCLR as a contaminant of A. flos-aquae products is calculated to be 10.0 mu g MC LR/g. (C) 1999 Academic Press.