PCBs Polychlorinated biphenyls

6. How has PCB exposure affected human health?

• 6.1 Has exposure to PCBs lead to more cancer cases?
• 6.2 Has exposure to PCBs affected human reproduction and development?
• 6.3 Have PCBs caused other health effects?

PCB exposure varies greatly from person to person in terms of amount and type of PCB mixture. In addition, humans can be exposed to different contaminants in PCB mixtures, as well as PCB combustion by-products. Differences in exposure make it difficult to establish a clear relationship between PCB exposure and any observed effects on human health.

Nonetheless, the evidence suggests that exposure to PCBs is associated with an increased risk of certain cancers of the digestive tract, liver and skin. PCB exposure is also associated with reproductive deficiencies, such as reduced growth rates, retarded development, and certain neurological effects which may or may not persist beyond infancy. The immune system can also be affected, leading to increased infection rates, and changes in the skin such as chloracne and pigmentation disturbances.

This text is a summary of: IPCS - WHO Polychlorinated biphenyls : Human health aspects. Concise international chemical assessment document 55
Section 9.0, Effects on humans 

6.1 Has exposure to PCBs lead to more cancer cases?

Fifty studies conducted since 1976, mainly on people exposed to PCBs at work, indicated increases in mortality from cancers of the gastrointestinal tract, the liver, the organs and tissues involved in the production of blood, including bone marrow, the spleen, tonsils, and lymph nodes, and from malignant melanoma.

Exposure at workplaces was studied at several plants manufacturing PCB-impregnated capacitors, where exposure occurred through the air. Other studies involved exposure through foods, such as fish and rice oil or rice bran-oil, which had been contaminated with PCBs, but also with other toxic chemicals. The variation between these studies and the mixed results means that no consistent picture emerges for PCB-induced cancer of any particular organ/tissue. However, one study found a strong dose-response relationship between serum PCB levels and non-Hodgkin lymphoma, a cancer of the lymphatic system.

This text is a summary of: IPCS - WHO Polychlorinated biphenyls : Human health aspects. Concise international chemical assessment document 55
Section 9.1, Carcinogenicity 

6.2 Has exposure to PCBs affected human reproduction and development?

Various studies examined effects on fertility due to PCB exposure through fish consumption and at the work place. In a study of New York women, a decrease in the ability to conceive was observed amongst those who regularly ate locally-caught fish that were contaminated with PCBs. In men, a study of 55 transformer repair workers found no association between exposure to PCBs and sperm counts. However, in another study, for men with a low sperm count the ability of sperm to move decreased as the concentration of three coplanar PCBs in their blood serum increased. Another study reported higher levels of certain PCBs in infertile men compared with the control population.

Since the 1980s numerous studies have investigated the effects of PCB exposure both during and after pregnancy on child growth and development. Researchers can estimate the degree of PCB exposure in the womb by measuring the level of PCBs in the umbilical cord blood serum. By analyzing breast milk samples, the extent of PCB transmission from mother to child can be deduced.

Effects of exposure to PCBs on the developing fetus have been investigated in women who consumed PCB-contaminated fish from Lake Michigan over a 6-year period. Overall fish consumption and levels of PCBs in cord blood serum were associated with lower birth weight, smaller head circumference, and shorter pregnancies.

Fish consumption during pregnancy was related to lesser neuromuscular maturity of the newborn. PCB-contaminated fish consumption has also been linked to impaired involuntary muscle actions and abnormally weak reflexes.

High levels of PCBs in umbilical cord blood serum have repeatedly been linked with poor performance in standard tests carried out to assess the mental and motor abilities of the newborn. Follow-up studies on children aged 4 and 11 indicated that PCB exposure in the womb was linked to impaired memory and attention, specifically short term memory and performance in IQ tests. Contrastingly, other follow up studies have shown that psychomotor deficits do not persist beyond childhood. Although one study indicated exposure to PCBs through breast-milk did not affect memory performance, another study showed lower mental development in 7-month old infants fed with breast milk containing high levels of three common non-planar PCBs.

This text is a summary of: IPCS - WHO Polychlorinated biphenyls : Human health aspects. Concise international chemical assessment document 55
Section 9.3, Reproductive toxicity 

6.3 Have PCBs caused other health effects?

The effects of PCBs exposure on the immune system of adults and children have been examined in two different studies.

An analysis of blood samples showed that Swedish males who consumed a large amount of fish from the Baltic Sea had higher PCB levels and lower numbers of natural killer cells in their blood than a group of males who did not consume any fish. It should be noted, however, that the presence of DDT may have influenced the results.

Another study on infants exposed to PCBs and dioxins both before and after birth found no relationship between exposure and respiratory abnormalities. When these children were three and a half years old, a follow-up assessment showed that higher PCB levels in the blood plasma were associated with a higher frequency of recurrent middle-ear infections and chicken pox.

Information on neurological effects of PCB exposure in adults is limited. People (accidentally) exposed to PCBs in the workplace reported headaches, dizziness, depression, fatigue, and a tingling sensation in the hands. People regularly consuming fish from PCB-contaminated waters performed poorly on tests requiring reasoning, word naming, auditory recall, and complex motor tasks. However, heavy metals and pesticides may also have been present in these contaminated fish. Significantly higher concentrations of PCBs, especially two highly chlorinated PCBs, were found in the brains of Parkinson’s disease patients than in control groups. Adults that ingested rice oil contaminated with PCBs and dioxins showed various neurological symptoms such as numbness, weakness, and limb pain, partial loss of sensation, and headaches. Exposure also caused a reduction in the speed of nerve impulse transmission.

Skin problems, particularly rashes and chloracne, have been observed in workers exposed to PCB mixtures used in commercial processes, as well as among people who ingested rice oil contaminated by PCBs and dioxins.

Characteristic skin changes included blocked pores, acne, hyper-pigmentation, skin thickening, and deformed nails. Such skin problems affected many parts of the body and improved over time.

In infants born to exposed mothers, similar skin problems were commonly observed but generally diminished as the infants grew older.

This text is a summary of: IPCS - WHO Polychlorinated biphenyls : Human health aspects. Concise international chemical assessment document 55
Section 9.4, Immunological effects,  Section 9.5, Neurological effects   and
Section 9.6, Irritation and sensitization