Cyanotoxin bioaccumulation in freshwater fish, Washington State, USA

Until recently, exposure pathways of concern for cyanotoxins have focused on recreational exposure, drinking water, and dermal contact. Exposure to cyanotoxins through fish consumption is a relatively new area of investigation. To address this concern, microcystins and other cyanotoxins were analyzed in fish collected from nine Washington lakes with recurrent toxic blooms using two types of enzyme-linked immunosorbent assays (ELISAs) and liquid chromatography/mass spectrometry/mass spectrometry (LC-MS/MS). Microcystins or microcystin-like compounds were elevated in fish liver relative to muscle and other tissues (liver > gut > muscle). Microcystin concentrations in fish fillet samples using anti-Adda ELISA (range 6.3-11 mu g/kg wet weight) were consistently higher in all fish species than concentrations using anti-microcystin (MC)-leucine-arginine (LR) ELISA (range 0.25-2.4 mu g/kg wet weight). MC-leucine-alanine (LA) was the only variant detected in fish (2.5-12 mu g/kg in four livers) among the nine variants analyzed by LC-MS/MS. Fish fillets showed no accumulation of the MCs targeted by LC-MS/MS. Other cyanotoxins analyzed (anatoxin-a, saxitoxin, domoic acid, and okadaic acid) were not detected in fish. Based on this and evidence from other studies, we believe that people can safely consume two 8-oz fish fillet meals per week from lakes with blooms producing MCs (clean the fish and discard viscera).