Polychlorinated Biphenyls (PCBs)
What are PCBs?
PCBs, or polychlorinated biphenyls, are members of a chemical family that were widely used in the past in industry as lubricants, coatings, and insulation materials for electrical equipment like transformers and capacitors.
They also found widespread use in common consumer items such as hydraulic fluid, fluorescent lights, various appliances, televisions, etc. Because PCBs tend to persist for long periods in the environment and have negative effects on wildlife, they were banned from use in 1977. 
PCBs have been released into the environment from several sources:
- Poorly maintained hazardous waste dumps and city landfills
- Illegal or improper dumping of hydraulic fluids/coolants
- Leaks from electrical transformers and other equipment
- Burning of medical, industrial, or city waste
- From older consumer goods like televisions  
These chemicals are often discussed along with dioxins because both families of compounds share similar chemical structures, are often found in fatty tissues, and tend to accumulate in the body over time.
How can my child or I be exposed to PCBs?
Because of their tendency to persist in the environment, small amounts of PCBs are present in almost all outside air, inside air, water, soil, and plants. Possible sources of exposure include:
- An important route of environmental PCB exposure is through the diet, especially milk (breast and dairy), fish, and other meats.
- One reason for this is that PCBs tend to be stored in fatty materials such as meat. Since breast milk contains fat, nursing infants may be exposed to relatively high PCB levels from breast milk.
- Another reason is that PCBs tend to accumulate in the body. Fish caught from PCB-contaminated waters tend to have higher levels of PCBs than the smaller fish or plant material they eat. When a pregnant mother eats these fish, these PCBs are once again poorly eliminated from the body. This phenomenon is called bioconcentration.
- Increased exposure to PCBs may occur through breathing indoor air in buildings that have electrical appliances that use PCBs. 
- PCBs may be found in old fluorescent lighting fixtures and old appliances such as television sets and refrigerators. When they get hot during use, these products may leak small amounts of PCBs into the air. 
- Also, higher levels of exposure can occur in outdoor air close to certain hazardous waste facilities. 
- Exposure to PCBs can occur through various sources of contaminated water including wells, surface water, swimming areas, etc.
- Since PCBs cannot dissolve well in water, these sources of exposure are not considered nearly as important as the diet. 
- As mentioned, very small amounts of PCBs are found in almost all soils.
- Children playing in soils near certain hazardous waste sites may be exposed to relatively high levels of PCBs. This may occur from eating the soil or by absorbing them across the skin. 
- Workplace exposures tend to involve relatively higher levels of PCBs than exposures from the home or general environment. 
- Possible sources of exposure in this setting include:
- disposal of PCB contaminated wastes
- repair of certain electrical transformers
- accidents involving transformers 
What are the health effects of PCBs?
We will discuss these health effects in terms of acute, high level exposure and chronic, low level exposure.
- Acute high-level exposure
In the late 1960s and early 1970s, there were two large-scale episodes of exposure to PCB-contaminated rice oil in Japan and Taiwan.  These episodes have provided much of our knowledge of the health effects of acute, high-level exposure to PCBs. This type of exposure has also been studied in occupational settings.
This type of exposure may cause various forms of skin rashes and acne in exposed adults or children. The type of acne caused by PCBs is called chloracne and is very similar in appearance to regular acne.  However, the main health effects of PCBs in these settings were experienced by the children born to exposed mothers. Based upon follow-up studies of these two incidents in Japan and Taiwan, pregnant mothers exposed to high-levels of PCBs may have children with the following problems lasting months to years after birth:
- darkening of skin color 
- facial abnormalities 
- nail changes 
- lowered IQ 
- altered nerve function 
- abnormal behavior 
- Chronic low-level exposure
Compared with high-level exposure, our knowledge of the health effects of lower-level exposure is much less complete. Based upon limited human evidence, this type of exposure may cause the following effects in children born to exposed mothers:
Each of these effects is discussed below:
- problems with movement 
- abnormal reflexes 
- problems with memory 
- learning disabilities 
- problems with attention 
- altered thyroid function 
- problems with immune response 
- increases in certain forms of cancer 
- Child Development
As stated, chronic lower-level exposure to PCBs may cause developmental problems in children born to exposed mothers. There is evidence both for and against the the developmental toxicity of PCBs in the medical literature. 
Nevertheless, there is enough human evidence that we should be concerned about the possible developmental health effects of PCBs, especially to infants and children. Several studies have suggested that the developing fetus may be relatively more vulnerable to the influence of PCBs than nursing infants .
- Neurobehavioral function
Several human studies have demonstrated subtle, but significant neurobehavioral deficits in children exposed to chronic, low levels of PCBs. . However, the specific neurobehavioral deficits found have varied somewhat from study to study. Our knowledge of these neurobehavioral is far from complete.
Several animal studies have also given us reason for concern. Such studies have consistently shown that exposure to low levels of PCBs similar to the levels commonly found in human breast milk may have negative health effects. These effects include problems with learning, behavior, and memory. 
- Hormonal function
There is limited evidence associating PCBs with altered thyroid function. There is also evidence against such an association, but there appears to be more evidence in favor of this association. .
- Immune function
With regards to immune function, there is little human evidence linking chronic, low-level exposure to PCBs with impaired immune response.  However, several animal studies have suggested that PCBs can have negative effects on the immune system. 
There is little human evidence that PCBs can cause cancer in humans. Most of this data is from studies of workers exposed to relatively high doses of PCBs and may not be relevant to the children exposed to background levels of PCBs.  Also, there has been some concern that exposure to PCBs are associated with increased risk of breast cancer, but the weight of the available evidence argues against this association. 
However, several animal studies have demonstrated that animals enough quantities of PCBs over time had higher rates of certain cancers than unexposed animals.  Based upon this evidence, the EPA and the International Agency for Research on Cancer (IARC) have classified PCBs as probable human carcinogens. 
Is there a test to see if my child has been exposed to high levels of PCBs?
There are medical tests that can detect the amount of PCBs in the blood, breast milk, or body fat. Of these, the blood test is probably the easiest and safest method of testing. 
However, these cannot tell how when the exposure occurred or long the exposure has gone on. Also, if the test reveals that your child has high levels of PCBs, it cannot be used to predict whether this exposure will cause health problems. 
How can I limit PCB exposure to myself and my child?
Because PCBs are nearly universal in the environment, it may be impossible to avoid exposure altogether. Some ways to avoid excess exposure are:
- If you discover that a particular shipment of food is contaminated with high levels of PCBs, do not eat this food.
- Pregnant mothers should limit consumption of sport fishes caught from waters contaminated with PCBs.  Your state environmental department can tell you whether your local waters are contaminated.
- If you live near a hazardous waste facility, encourage your children not to play in the soil and especially not to eat the soil.
- If any member of the household works with old electrical equipment including transformers, be sure that the equipment is well maintained and the area is well ventilated.
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