Fish Consumption Advisories: Contaminants

Contaminants

Dioxins

There are a number of dioxin compounds. Dioxins are not intentionally manufactured by industry. They are the byproduct of other industrial processes. The most heavily studied compound - 2,3,7,8-TCDD - is formed during the chlorine bleaching process at pulp and paper mills. All of North Carolina’s dioxin-related fish consumption advisories are related to paper mills. All of the paper mills have made substantial changes to their processes to reduce or prevent dioxin formation. That’s why several of the advisories have been modified since they were originally issued.

Studies have shown that exposure to 2,3,7,8-TCDD increases the risk of several types of cancer in animals. Some studies suggest that dioxin increases the risk of certain types of cancer in humans. Other studies don’t show any connection between dioxin exposure and cancer. The most common health effect in humans is chloracne. Chloracne is a severe skin disease, characterized by large, deep acne-like lesions.

Mercury

Mercury is an odorless, silver-white metal that is found naturally in the environment. Industrial sources such as coal burning industries, municipal and medical waste incinerators and chlor-alkali plants release mercury into the air. That mercury is spread through the air and may be deposited in water. Mercury builds up in fish tissue and other aquatic life. As bigger fish eat smaller fish, the bigger fish get higher levels of mercury. That’s why many advisories related to mercury warn against eating large fish like bowfin or largemouth bass or ocean fish like shark or king mackerel.

Exposure to high levels of mercury can damage the brains of unborn children and young children. Prenatal exposure to mercury can affect the way children think, learn, and problem-solve later in life. That’s why many of the advisories are stronger for pregnant women and young children who are more sensitive to the toxic effects of mercury.

In adults, the earliest obvious signs of mercury poisoning are numbness of lips, fingers or toes, fatigue and blurred vision.

Polychlorinated Biphenyls (PCBs)

Polychlorinated biphenyls are mixtures of up to 209 individual compounds known as congeners. PCBs have been used as coolants and lubricants in transformers, capacitors and other electrical equipment because they don't burn easily and are good insulators. The manufacture of PCBs was stopped in the U.S. in 1977 because of evidence they build up in the environment and can cause harmful health effects. Products made before 1977 that may contain PCBs include old fluorescent lighting fixtures and electrical devices containing PCB capacitors, and old microscope and hydraulic oils.

PCBs can still be released to the environment from hazardous waste sites; illegal or improper disposal of industrial wastes and consumer products; leaks from old electrical transformers containing PCBs; and burning of some wastes in incinerators. PCBs do not readily break down in the environment and thus may remain there for very long periods of time. In water, a small amount of PCBs may remain dissolved, but most stick to organic particles and bottom sediments. PCBs also bind strongly to soil. PCBs are taken up by small organisms and fish in water. They are also taken up by other animals that eat these aquatic animals as food. PCBs accumulate in fish and marine mammals, reaching levels that may be many thousands of times higher than in water.

Women who ate large amounts of fish contaminated with PCBs had babies that weighed slightly less than babies from women who did not have these exposures. Babies born to women who ate PCB-contaminated fish also showed abnormal responses in tests of infant behavior. Some of these behaviors, such as problems with motor skills and a decrease in short-term memory, lasted for several years. Other studies suggest that the immune system was affected in children born to and nursed by mothers exposed to increased levels of PCBs. There are no reports of structural birth defects caused by exposure to PCBs or of health effects of PCBs in older children. Few studies of workers indicate that PCBs were associated with certain kinds of cancer in humans, such as cancer of the liver and biliary tract. Rats that ate food containing high levels of PCBs for two years developed liver cancer.

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Contaminants

N.C. Advisories

Mercury

Polychlorinated biphenyls (PCBs)

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