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PCBs in Sport Fish:
Answers to Questions on Health Effects

Polychlorinated biphenyls (PCBs) are a large group of industrial chemicals with a common structure. They are oily liquids or solids, clear to light brown in color, and have no smell or taste. PCBs do not occur naturally in the environment. Along with methylmercury, they pose the greatest health concern in eating sport-caught fish in several parts of the state, including San Francisco and Santa Monica bays. They are also one of the main chemical contaminants that have been found in fish in other parts of the country.

Excessive exposure to PCBs may cause a wide variety of adverse health effects. Our knowledge of the effects is based on both studies of people exposed in the workplace or who ate contaminated food, and on experimental studies with animals. Of particular concern are the effects on development in infants whose mothers have been exposed before and during pregnancy.

This document will give you information about PCBs and their potential health effects. It will explain the purpose of the health advisories that the Office of Environmental Health Hazard Assessment (OEHHA) has issued in areas where high levels of these chemicals have been found in fish. These health advisories give guidelines for limiting the amount of sport fish you eat and tell how to prepare and cook fish in a way that will remove some of the PCBs.

Summary of main points

  • PCBs had many industrial uses before their manufacture ended in 1977.
  • PCBs remain in the environment for years and can build up in fish.
  • Eating contaminated fish can cause PCBs to build up in your body over time. PCBs become stored in your fat.
  • In certain areas in California, PCBs have been measured in sport-caught fish at levels well above 100 ppb. These elevated levels may pose a health concern. OEHHA advises you to limit how much you eat of fish taken in these locations.
  • Some of the children whose mothers ate fish from the Great Lakes containing high levels of PCBs had delayed development of mental functions and muscular coordination. The levels of PCBs in the fish eaten by these mothers were 5 to 10 times higher than those found in fish in San Francisco Bay or other California waters where PCBs have been found at elevated levels.
  • PCBs can be transferred to nursing infants through breast milk. However, breast feeding is very beneficial to your baby. Do not stop breast feeding without first speaking to your doctor.
  • PCBs may cause cancer in humans because they have been found to cause cancer in laboratory animal studies.
  • Workers have experienced skin and eye irritation from contact with PCBs in the workplace. Many serious health effects have also been seen in studies with animals. These effects include liver, stomach and thyroid gland injuries; anemia; chloracne; and effects on reproduction.
  • At the PCB levels found in fish in California, a single large meal, or a few such meals, of fish should not make you ill. Frequent eating of PCB-contaminated fish over a period of years may lead to the build up of PCBs in your body. Although this might not lead to a distinct illness, prevention is the best remedy. The fish consumption guidelines that we provide in the advisories will protect health by preventing PCBs from building up to unsafe levels in your body.
  • You can lower the amount of PCBs in fish by following preparation and cooking methods that get rid of fat.

How were PCBs used and how did they get into fish?
The PCB group consists of 209 individual compounds, called congeners because they are structurally related. Commercial mixtures containing 40 to 70 PCB congeners were marketed under the trade name Aroclor, such as Aroclor 1260. Because they do not burn easily and are good insulators, PCBs were used extensively in transformers, capacitors, and other electrical equipment.

PCBs have entered the environment partly because of accidental leaks and fires in electrical equipment, past disposal in dumps, accidents in transport, and leakage from hazardous waste sites. Their widespread distribution in the environment was also caused by their use as plasticizers, in inks and dyes, as ingredients in pesticides, in adhesives, in protective wood coatings, and in carbonless-copy paper.

Manufacture of PCBs stopped in the United States in 1977 because of evidence that PCBs build up in the environment and cause harmful effects. In the environment they persist for a long time. Usually they stick to soil or sediments and may remain there for years, but they also are found in the air, water and food. PCBs enter the bodies of fish from water, sediment, and from eating prey that have PCBs in their bodies. PCBs build up in fish and can reach levels hundreds of thousands of times higher than the levels in water.

How might I be exposed to PCBs?
Eating contaminated fish is a major way of being exposed. Exposure to PCBs can also come from breathing workplace air (indoor air around older electrical parts or outdoor air at waste sites) or from skin contact with contaminated soil.

What levels of PCBs have been found in fish in California?
In 1994, the San Francisco Water Quality Control Board conducted a pilot study on chemical contaminants in fish in San Francisco Bay and found significant levels of PCBs in fish throughout the bay. The levels of PCBs ranged from a low of 21 parts per billion (ppb) in brown smoothhound sharks to a high of 638 ppb in white croaker. The highest levels of PCBs were found in fish taken at sites near industrial parts of San Francisco and Oakland, but elevated levels were also found in the north and south parts of the bay.

These levels are about the same, or less than, levels of PCBs found in fish from Santa Monica Bay. In both of these bays, white croaker, a very fatty fish, had the highest amounts of PCBs. These levels are greater than PCB levels in fish from San Diego and Monterey Bays. They are also higher than PCB levels found in most lakes and rivers in California except for some freshwater sites that are mainly in Los Angeles and Orange counties.

Levels of PCBs in San Francisco and Santa Monica bays are about five to ten times below the levels found in sport fish in the Great Lakes region. That region has some of the most extensive PCB contamination in the country.

OEHHA has issued advisories where sport-caught fish have been found to contain PCBs above 100 ppb. The advisories provide guidance on how much fish you can safely eat. The consumption limits are often specific to the species and fishing locations. The advisories are available from OEHHA and are printed in the California Sport Fishing Regulations booklet.

Are the levels of PCBs going down?
Data from the California State Mussel Watch program indicate that the levels of PCBs, DDT, and chlordane in San Francisco Bay have been steadily declining in the past 15 years since measurements have been taken. The PCB levels in the bay are four to seven times lower than when they were first measured. Although they are going down, PCBs last for a long time and are still at levels of concern in some areas.

What happens to the PCBs when you eat contaminated fish?
If you swallow food, water, or soil contaminated with PCBs, most of the PCBs will pass from the stomach into the bloodstream within minutes, and be distributed throughout your body. Most of the PCBs become stored in fatty tissue. Human milk may contain more PCBs than blood due to the high fat content of milk. Newborns can be exposed to PCBs through their mothers' milk, and fetuses may be exposed to PCBs from their mothers' blood through the placenta.

The most highly chlorinated PCB congeners are the most fat soluble and stay in the body the longest. Other congeners are eliminated more rapidly from the body. The PCB mixtures found in fish and in human tissues may differ significantly from the commercial PCB mixtures, but commercial mixtures are what have been used in studies with laboratory animals to determine toxicity. Therefore, some scientists prefer to evaluate health effects based on human studies. These studies usually compare populations who have been exposed to PCBs, such as in the workplace or from eating highly contaminated fish, with populations that have not been exposed. Human studies, however, also have limitations, as noted in examples below.

How do PCBs affect health?
Workers exposed on the job to PCBs at high levels have had irritation of their skin (acne, rashes, and coloring of the nails and skin) and eyes (redness, burning, irritation, and discharge). Rats that ate food containing large amounts of PCBs for a short period had mild liver damage, and some died. Animals that ate smaller amounts of PCBs in their food over several weeks or months had many serious health effects including liver, stomach and thyroid gland injuries; anemia; acne; and damaged reproduction. These effects have been seen in many different kinds of animals, including monkeys, as well as in the offspring of animals that ate PCBs. No birth defects have been reported.

At the PCB levels measured to date in fish in California, we would not expect you to become ill from any single large meal of fish or a few fish meals. Even if you ate PCB-contaminated sport fish frequently over a period of years, you might not develop any illness. This does not mean you should not be concerned. We do know that PCBs build up in the body over time, and that exposure to higher levels of PCBs in fish can cause measurable effects in children. There is also the potential for increased risk of cancer occurring after many years of exposure.

We do not have the tools to measure subtle effects, if any, that may be caused in people who are exposed to the levels of PCBs generally found in California. Sensitive medical tests may be able to detect physiological changes, but it would be hard to differentiate the changes caused by PCBs from those caused by other agents or illness. What we do is take the known effects from human and animal studies and estimate what would be a safe level of exposure to prevent those effects from happening. Our sport fish eating guidelines are designed to prevent PCBs from building up in your body above a safe level of exposure.

What is the main health concern from exposure to PCBs?
All PCB mixtures tested have caused adverse effects in the development of offspring of experimental animals, and several human studies have also suggested that PCB exposure may cause adverse effects in fetuses and children.

The results of human studies, while not consistent, are of particular concern. One of these studies examined pregnancy outcomes in women who had consumed PCB-contaminated fish from Lake Michigan over an average of 16 years, and who had exposure both before and during pregnancy. Children of the mothers who had eaten the contaminated fish had smaller heads, lower birth weights, and were more frequently born before their due date. They also had delayed neuromuscular development. When tested at seven months, the children were slower to recognize objects that they had been shown before. The women in this study were exposed to fish with estimated PCB levels between 168 and 3012 ppb. It was difficult, however, to determine how much PCBs the women in this study were exposed to because this information was based on their memory of how much they ate over many years. This study was further complicated because the women had exposures to other chemicals, and the exposed women, on average, drank more alcohol and caffeine before and during pregnancy, weighed more, and took more cold medications during pregnancy than the nonexposed women.

A recent study in North Carolina noted much more moderate effects of PCB exposure in the development of children whose mothers had been exposed. No changes in birth weight or head size were seen. Deficits seen in intellectual and muscle function in children up to two years of age were not detectable at ages three, four, and five. In this study, DDE (a product of the pesticide DDT) was also found in blood and milk samples from the mothers. PCBs measured in the mothers' blood were used as a measure of exposure, rather than the mothers' recall of their fish intake.

Evaluations of blood samples from women who aborted, miscarried or delivered prematurely showed associations between these effects and concentrations of PCBs. However, these effects were seen at higher levels of PCBs than typically found in California, and there was exposure to other chemicals beside PCBs.

Studies conducted in primates found neurological effects, including deficits in cognitive function in animals born to mothers exposed to PCBs when they were pregnant. Primates, which are similar to humans in neurological development, showed greater sensitivity than rodents did to PCBs.

The effects in these studies have mainly been from prenatal exposure of the fetus through the mother, but infant exposure through breast feeding is also of concern. Because the developing nervous system in the very young is more sensitive to PCBs, OEHHA recommends lower consumption limits for women who are pregnant or may become pregnant, or who are breastfeeding, and for children under 6.

What about cancer?
PCBs are considered likely to cause cancer in humans based on evidence that they cause cancer in laboratory animal studies. However, studies of humans exposed to PCBs have not yielded conclusive results. We do not know for certain whether PCBs cause cancer in humans. It is difficult to obtain conclusive results in such studies because of the long period between exposure and potential appearance of cancer 15 to 20 years later. Factors such as exposure to other chemicals and lifestyle differences also complicate the results. If the advisory guidelines are followed, the risk of developing cancer would be too low to be of health concern even if you eat sport-caught fish for many years.

Are all the health effects of PCBs known?
The health effects of PCBs are still under active evaluation. Immune system and hormone level effects are some of the more recent discoveries. The implications of some recent findings to humans are not yet known.

The U.S. EPA has identified a long list of studies needed to fill in areas of uncertainty. As new studies are reported, OEHHA scientists will continue to evaluate the results and update its fish consumption advisories.

Is there a way to reduce PCBs in fish to make them safer to eat?
As general advice, OEHHA recommends that you clean and gut the fish you catch before cooking it because some chemicals, including PCBs, tend to concentrate in the organs, particularly in the liver. PCBs are mainly stored in the fat and can be reduced by getting rid of the fat. You should also trim the fat, remove the skin, and fillet the fish before cooking. Fat is located along the back and the belly, and in the dark meat along the lateral line running along the side of the fish. Skinning fish will remove the thin layer of fat under the skin. You should use a cooking method such as baking or grilling that allows the juices to drain away, and then discard the cooking juices. Using these methods may eliminate about half or more of the PCBs in fish.

When properly prepared, fish provide protein that is low in saturated fats. Replacing high fat foods in the diet with low fat foods can provide real health benefits. You can get the health benefits of fish and reduce unwanted contaminants by following this advisory.

OEHHA also recommends fishing in different locations in case the location where you are accustomed to fishing is highly contaminated. Also, as a rule, eating a variety of fish species is likely to reduce your exposure to a species that has high contamination.

Where can I get more information?
The health advisories for sport fish in all parts of California are printed in the California Sport Fishing Regulations booklet, which is available wherever fishing licenses are sold. They are also available from the Office of Environmental Health Hazard Assessment, including new updates. OEHHA has additional educational materials and reports on fish contamination in the state.

Follow this link to download a copy of this fact sheet as an Adobe Acrobat PDF file.

The following reports and fact sheets also include PCB contamination in sport fish:

Evaluation of Potential Health Effects of Eating Fish
from Black Butte Reservoir (Glenn and Tehama Counties): Guidelines for Sport Fish Consumption
[03/30/00] Download the Draft Report

Prevalence of Selected Target Chemical Contaminants
in Sport Fish From Two California Lakes: Public Health Designated Screening Study
[02/14/00] Download the Study

1991 Study of Chemical Contamination of Marine Fish
from Southern California (pdf - summary)

Summary of Chemicals of Concern Found in Fish

 
 
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