Due to bioaccumulation, mercury concentrations in fish can be over 100,000 times the mercury concentration in the water. Adverse health effects from mercury include tingling of the skin, incoordination, visual and hearing impairment, and damage to the central nervous system. Infants and children exposed prenatally to high levels of mercury may exhibit neurological symptoms similar to those of a cerebral palsy- like syndrome. The fetus is at a particular risk for irreversible nervous system damage from mercury poisoning. Dioxins are unwanted by-products formed during several industrial processes, including the production of bleached paper.
Dioxins are probable human carcinogens and can cause a type of dermatitis in humans.
Adverse effects in animals include red blood cell damage, nervous system disorders, suppression of the immune system, liver and thymus abnormalities, birth defects, and reproductive effects. Health concerns from dioxins are based on long term, regular consumption of fish and shellfish contaminated with these persistent compounds. PCBs are probable human carcinogens that can persist in the environment for years and that readily bioaccumulate in fish tissue. Adverse health effects in animals include liver tumors, skin irritations, reproductive and developmental effects, suppression of the immune system, and damage to the stomach, thyroid, and kidney. They are not known to bioaccumulate in fish and are usually a reflection of the same concentration of these contaminants in water.