University at Albany Institute
for Health and the Environment

Contaminants Found in Farmed Salmon

PCBs

Banned in the U.S. in 1976 and among the "dirty dozen" toxic chemicals slated for global phase-out under a United Nations Convention signed by the U.S., these industrial insulators and lubricants persist in the environment for decades. They can accumulate up the food chain to humans.

Health Risks:

PCBs have been implicated in a variety of diseases, including cancer. The U.S. Environmental Protection Agency (EPA) has classified PCBs as probable human carcinogens. PCBs have also been linked to reproductive, neurological, and developmental effects in humans and animals. They can suppress the immune system and cause disruption of thyroid and sex steroid endocrine systems. PCB exposure, particularly before birth, has been linked to lower IQ, hyperactivity, shortened attention span, and delayed acquisition of reading skills.

Sources:

Because of their fire-retardant and insulating properties, PCBs were produced for use in electrical equipment, hydraulic fluids, and many other industrial and commercial applications. Although production of PCBs was banned in 1977 because of environmental and health concerns, thousands of tons of PCB-contaminated fluids are still in use in electrical and industrial equipment. PCBs continue to enter the environment from leaking equipment, illegal dumping, and disposal of equipment containing PCBs in hazardous waste sites.

Exposure:

PCBs can persist in soil and in marine sediments for years. They can also travel thousands of miles in the atmosphere, resulting in contamination of pristine areas such as the Arctic and the oceans. PCBs tend to accumulate in the fatty tissues of living organisms and their levels increase up the food chain until they reach levels thousands of times higher than their original concentration in water (a process called biomagnification). As a result, people can be exposed to PCBs through consumption of fish, meat, and dairy products. Individuals typically eliminate half of their body burden of PCBs after a period of 7 to 10 years.

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Dioxins

Dioxin and dioxin-like compounds are byproducts of high-temperature industrial and waste treatment and disposal processes, especially the burning of chemicals that contain chlorine and incineration. Dioxin and dioxin-like compounds persist in the environment for decades. They can cause cancer and are toxic to the fetal endocrine system.

Health Risks:

Dioxins and furans have been linked to many serious health effects in humans, including cancer, reproductive and developmental effects, altered immune function, and disruption of the endocrine system. Dioxins are listed by several governmental and international agencies as known causes of cancer in humans. Dioxins continue to be studied, and health effects have been found at increasingly lower levels.

Sources:

Dioxin and dioxin-like compounds are a family of more than 150 compounds formed as industrial waste by-products during waste incineration, chemical manufacturing, PVC production, paper bleaching, metal smelting, and a variety of other processes. Dioxins enter the environment primarily by deposition from the air.

Exposure:

Dioxin-like compounds persist in the environment by attaching to soil particles and sediment in water. Once attached to such particles, they enter the food chain by accumulating in the fatty tissues of animals and humans where they can remain for long periods. Most human exposure to dioxins comes from consumption of dioxin-contaminated meat, fish, and dairy products. Less common routes of exposure include living near waste sites and incinerators and working at industrial sites that produce dioxins.

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Toxaphene

Toxaphene is a banned pesticide that persists in the environment. It can contaminate fish and drinking water. Toxaphene is associated with a variety of possible health effects and is considered a probable carcinogen.

Health Risks:

High level exposure to toxaphene can damage the lungs, nervous system, and kidneys, and can cause death. There is little information on the effects of low level exposures. Studies show effects on the liver, kidneys, adrenal glands, and immune system of animals that ate food or drank water containing toxaphene. Animal studies have reported that toxaphene affects the development of newborn animals when their mothers are exposed during pregnancy. An animal study reported that toxaphene caused cancer of the thyroid gland when the animals were exposed to high levels over their lifetimes. The EPA has determined that toxaphene is a probable human carcinogen. The U.S. Department of Health and Human Services has determined that toxaphene may reasonably be anticipated to be a carcinogen.

Sources:

Before it was banned for general use in 1982, toxaphene was widely used in the mid-1970s as a replacement for the banned pesticide DDT. It was used as an agricultural insecticide on cotton, cereal grains, fruits, nuts, and vegetables. It was also used to control ticks and mites in livestock and to kill unwanted fish species in lakes.

Exposure:

Once introduced into the environment, toxaphene persists for long periods of time. It binds strongly to soil and sediment, and is ubiquitous in both fresh water and saltwater. The chemical evaporates and moves on global air currents from which it can precipitate as rain or snow in regions where the chemical was never used. It is consistently found in certain fish. Humans are most commonly exposed to toxaphene through eating contaminated fish or breathing air near a hazardous waste site containing toxaphene. Once consumed by humans, it remains stored in body fat for long periods of time.

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Dieldrin

Dieldrin is a banned pesticide that is highly persistent in the environment. It can contaminate fish, meat, and dairy products. Dieldrin is considered a probable human carcinogen by the U.S. EPA.

Health Risks:

Dieldrin has been shown to cause liver cancer in mice. The EPA has determined that dieldrin is a probable human carcinogen, although the International Agency for Research on Cancer (IARC) has determined that dieldrin is not classifiable as to human carcinogenicity. In animals, oral exposure to low levels of dieldrin for long periods affected the liver and reduced immune system function. Animals exposed to high amounts demonstrated nervous system effects. Studies in animals have given conflicting results about whether dieldrin can affect reproduction in male animals and whether these chemicals may damage the sperm. It is not known whether dieldrin can affect reproduction in humans.

Sources:

Dieldrin is a pesticide and is also formed as the breakdown product of another pesticide, Aldrin. It was originally used on cotton, corn, and citrus crops; to control diseases carried by insects such as mosquitoes and tsetse flies; and as a wood preservative to control termites. Dieldrin’s peak production occurred from the 1950s to the early 1970s. It was banned in the U.S. in 1974 for nearly all uses.

Exposure:

Dieldrin binds tightly to soil and slowly evaporates in the air. Plants take in and store dieldrin from the soil. It can then be stored in the fat of animals and fish, leaving the body very slowly. Most common exposures are from eating food like fish or shellfish from lakes or streams contaminated with dieldrin, contaminated root crops, dairy products, and meats. Some people are exposed from living in homes that were once treated with aldrin or dieldrin to control termites.

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Information from the study's authors