Microcystins in Aquatic Food Products: Linking Environmental Transfer, Consumed Matrices, and Dietary Risk

Microcystins (MCs) produced by cyanobacteria can contaminate aquatic foods, but drinking water surveillance does not directly characterize dietary exposure. This critical narrative and framework review evaluates environmental transfer, tissue residues, analytical coverage, toxicity, exposure assessment, and management for fish, bivalves, crustaceans, and related products, with a separate assessment of algal dietary supplements. Evidence is organized by species, consumed tissue, concentration basis, analytical fraction, congener coverage, and consumption scenario. Reported concentrations are not directly comparable when studies analyze different organs or use different extraction procedures and mass bases. Paired analyses of tilapia muscle illustrate how measurements limited to free congeners can miss a substantial additional burden, while shellfish studies show why clearance requires verification in the edible tissue. Structural and toxicological evidence explains why MC-LR provides a reference for assessment but does not fully characterize every mixture. We propose a framework linking environmental warnings to product sampling, validated quantification, explicit exposure scenarios, and proportionate management. Priorities are comparable occurrence reporting, interlaboratory validation, characterization of the oral relevance of bound fractions, and congener-specific toxicity data. Neither a positive screening result nor an exceedance of a chronic intake benchmark alone establishes the probability of illness from an individual meal.