Fish as environmental sentinels for metal contaminants of human health concern in the Lower Mississippi River Basin

Industrial expansion and population growth have lowered water quality, polluting aquatic ecosystems world-wide. Metal pollution in the rivers across the United States are a major health concern. The level of metal contamination in fish from the Lower Mississippi River Basin and their threat to public health were last evaluated 20 years ago. The goals of this study were to measure metal contamination in various fish species from the Lower Mississippi River Basin, evaluate the human consumption risk, and estimate bioindicator potential of these species for monitoring toxic metals on a larger scale. Various fish species (n = 203) were analyzed for 15 metal contaminants (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Se, and Zn). Species included: blue catfish (Ictalurus furcatus), channel catfish (Ictalurus punctatus), flathead catfish (Pylodictis olivaris), bigmouth buffalo (Ictiobus cyprinellus), smallmouth buffalo (Ictiobus bubalus), alligator gar (Atractosteus spatula), spotted gar (Lepisosteus oculatus), American gizzard shad (Dorosoma cepedianum), freshwater drum, (Aplodinotus grunniens), and white crappie (Pomoxis annularis). Fish consumption safety revealed toxic metals (As, Cd, Cr, Hg, and Pb) are a major human health concern in the Lower Mississippi River. Non-cancerous health hazard assessments indicated blue catfish, flathead catfish, gar species, and freshwater drum as species of concern. Consumption of all species posed human cancer risks. Computational modeling, with an accuracy of 98.5 %, identified Hg, Pb, Zn, Cr, Co, As, and Cd as major drivers of fish consumption safety. Using bioaccumulation factor analysis, we estimated the bioindicator potential of toxic metals for each fish species, finding Hg and Cd to be greatly bioaccumulative in predatory gar species. Overall, our data indicated that gar can serve as select environmental sentinels useful for monitoring toxic metal pollutants of public health concerns providing valuable insight to research scientist and monitoring agencies throughout the Lower Mississippi River Basin.