The Effects of Common Toxins on Freshwater Fish
- Mercury, Hg, is a natural metal that is often found in fish, both freshwater and marine. There is no way to clean or cook the mercury out of a fish because it is stored in the muscle fibers. Consumption of mercury can lead to impaired neurological development in children, infants and fetuses. This affects memory, language development, motor skills and cognitive thinking among other things. For this reason, pregnant women, nursing mothers and young children are cautioned against consumption of fish that might be laden with mercury, such as bass. The effect of mercury on fish is mostly negated by high levels of alkyglycerols, which boost the immune system and helps prevent mercury poisoning.
- Polybrominated Diphenyl Ethers, or PBDEs, are chemicals that are used to increase the heat resistance and flame retardant nature of consumer products. PBDEs are leeched into the environment through the soil and water table. They have been detected in a number of foods including freshwater fish. Samples of breast milk and blood have shown PBDEs in humans. The effects of PBDEs on humans or fish are not known. Studies have not linked the toxin with any specific conditions, though they are presumed to be harmful because they are not naturally occurring.
- Polychlorinated biphenyls, or PCBs, are harmful industrial compounds that have been used to create many useful items including transformers, hydraulic fluids, lubricants and paper. There are more than 200 different types of PCBs in existence. However, all PCB manufacturing was banned in the U.S. during the late 1970s. PCBs were introduced into the environment in solid form. Because they do not mix with water, they simply settled on top of soil and stream beds, where they were eaten by small fish and became present in large fish through consumption of prey. The effects of PCB are similar to mercury. Children and exposed fetuses may experience retarded development, both physical and cognitive. Adults who consumed PCBs showed decreased performance on memory and learning tests. Salmon and rainbow trout are both low in PCBs, according to the Environmental Defense Fund.
- Harmful algal blooms, or HABs, are bacterial growths that occur both in saltwater and freshwater. Sometimes referred to as blue-green algae, HABs are not algae, but rather cyanobacteria, a toxic organism that engages in photosynthesis. HABs have been seen in a variety of colors from green to purple and red. There are three main classes of toxins associated with cyanobacteria: neurotoxins, hepatotoxins and dermatotoxins, which affect the nerves, liver and skin, respectively. In fish, these toxins and the presence of large cyanobasterial blooms can result in clogged gills, loss of hearing, depletion of oxygen and death.