Mississippi River-caught fish contain toxic metals of human health concern, research reveals

 

Winding its way south over 2,300 miles from Minnesota down to the Gulf, the Mississippi River is well-known as one of the world’s largest rivers and a cultural symbol for generations of North Americans. We even use it as a geographical point of reference (we’ve all heard the term “this is the biggest/smallest so-and-so east/west of the Mississippi…”). But a dark secret lurks beneath. And it’s not just dangerous undercurrents.

Drs. Scoty Hearst and Trent Selby, professors in the Chemistry and Biochemistry Department at Mississippi College in Clinton, Mississippi, are analyzing fish caught out of the Lower Mississippi River Basin to determine the level of toxic metals that accumulate in their flesh as part of a study funded by the Mississippi IDeA Network of Biomedical Research Excellence (Mississippi INBRE). Their results, published in a recent issue of Elsevier, indicated that some fish species, such as gar, contained levels of toxic metals exceeding safe consumption limits outlined by the World Health Organization, including lead and mercury.

“We surveyed concentrations of toxic metals in fish we collected from the Mississippi River in Warren County, Mississippi,” said Dr. Hearst. “Our results indicate that consumption of some fish species, such as gar, from this location should be limited due to unsafe mercury levels.”

High rates of pollution flow into the Mississippi River from anthropogenic and industrial sources. These pollutants can accumulate in soil too, possibly contaminating food crops grown in major agricultural production areas along the river such as the Mississippi Delta. High rates of pollution could be entering fresh water and food sources across Mississippi, leading to the public health concerns.

Dr. Hearst explained, “The health of the environment directly impacts human health. Our results warrant further study into these concerns.”

And the fish collected in this study weren’t just “trash fish,” as fishermen commonly call fish species that aren’t usually kept and consumed when caught. The fish analyzed included channel catfish, blue catfish, and white crappie, prime targets for those looking to catch a meal on the banks of the Mississippi.

All of this begs the question: should we be limiting our consumption of fish from the Mississippi River?

“Fish should be surveyed from multiple locations in the Mississippi River to fully determine consumption safety,” explained Dr. Hearst.

Farm-raised fish is probably the safer option, based on the results of an analysis comparing toxic metal accumulation in wild-caught and farm-raised fish conducted by the Hearst Lab.

“My team has performed mercury analysis on farm-raised and wild-caught salmon. These results indicated that farm-raised fish were lower in mercury and a safer choice for human consumption,” said Dr. Hearst.

Dr. Hearst suspects this is because farmers can control the diet and aquatic environment of farm-raised fish. Wild-caught fish, on the other hand, are often subjected to environmental pollution, contaminating both the food they eat and the water they breathe. Contaminants in farmed fish can often be corrected with modern chemicals and adjustments to diet, but that would be impossible in a natural aquatic environment. Even if one could, unchecked environmental pollution continues to seep into the Mississippi River every day, making for a never-ending uphill battle.

The solution, as readers might have already guessed, is to reduce pollution in the Mississippi River, and furthermore, the world, reducing human exposure to these toxic metals whether through the food we eat or the water we drink. As is often the case, educating future generations is key.  

“We need more public outreach and education to warn people of potential hazards in their environment or in their food supply, so that every day people can make better health choices,” explains Dr. Hearst.

Education invariably ignites passion, the kind of passion that might push future generations to pursue environmental research as a career. More research translates into new, innovative methods to solve the current pollution crisis and, furthermore, the many public health threats humans face in our rapidly evolving modern world.

“Training students in biomedical research is key for a better future. These young minds create new ideas that lead to scientific innovations, helping to improve healthcare, discover new diseases, and develop treatments for them,” Dr. Hearst explains.

“At least in my case, I know my students will always be thinking about environmental contaminates and their impact on human health. Hopefully, these ideas will foster innovative, research-based solutions to these problems in their future careers.”