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Fact Sheet 12
What Are The Human Health Effects Of PCBs?

Polychlorinated biphenyls are a group of 209 different chemicals which share a common structure but vary in the number of attached chlorine atoms. An estimated 1.3 million pounds of different types of PCBs were dumped into the Hudson River by General Electric from 1946 until 1977, when they were banned. The international treaty on Persistent Organic Pollutants, drafted by 122 nations in Johannesburg in December 2000, targeted PCBs as one of the `dirty dozen´ chemicals to be phased out worldwide.

PCBs are a probable human carcinogen.

The International Agency for Research on Cancer and the Environmental Protection Agency classify PCBs as a probable human carcinogen. The National Toxicology Program has concluded that PCBs are reasonably likely to cause cancer in humans. The National Institute for Occupational Safety and Health has determined that PCBs are a potential occupational carcinogen.

Studies of PCBs in humans have found increased rates of melanomas, liver cancer, gall bladder cancer, biliary tract cancer, gastrointestinal tract cancer, and brain cancer, [1] and may be linked to breast cancer. PCBs are known to cause a variety of types of cancer in rats, mice, and other study animals. [2]

Why are PCBs called a `probable´ carcinogen?
EPA´s regulations on cancer-causing chemicals use the term `probable´ when a chemical is known to cause cancer in animals and where there is evidence that suggests that it causes cancer in humans but which is not conclusive. Because you can´t feed chemicals to humans to see how they respond, it is much more difficult to demonstrate carcinogenicity in humans than in animals. Instead, studies are undertaken of groups who have been exposed to a chemical, and if they suffer from more cancers than would be expected at normal levels, this may indicate that the chemical was a carcinogen. However, there are many difficulties doing these studies: small numbers of people known to be exposed to a chemical; the fact that people suffer from many cancers without any chemical exposure; the fact that in some cases these people were exposed to a number of other chemicals; and the need to demonstrate high cancer rates that cannot be random in order to draw conclusions. Thus the term `probable´ reflects the limited nature of the studies, and it is rare that a carcinogen is so effective that it can be called a `known´ human carcinogen.

The fact that PCBs are called a `probable´ carcinogen should not be taken as a sign that they are benign.

Acute toxic effects.

People exposed directly to high levels of PCBs, either via the skin, by consumption, or in the air, have experienced irritation of the nose and lungs, skin irritations such as severe acne (chloracne) and rashes, and eye problems. [3]

PCBs cause developmental effects.

Women exposed to PCBs before or during pregnancy can give birth to children with significant neurological and motor control problems, including lowered IQ and poor short-term memory.

A group of children in Michigan whose mothers had been exposed to PCBs were found to have decreased birth weight and head size, lowered performance on standardized memory, psychomotor and behavioral tests, and lowered IQ. These effects lasted through at least 7 years. [4] A group of women occupationally exposed to PCBs in upstate New York had shorter pregnancies and gave birth to children with lower birth weight. [5] Another study, of the chidren of women who ate contaminated Lake Ontario fish, found significant performance impairments on a standardized behavioral assessment test. [6]

Exposure of one form of PCB to rats resulted in retarded growth, delayed puberty, decreased sperm counts, and genital malformations. [7] In other studies, exposure of PCBs to rats in utero led to behavioral and psychomotor effects that lasted into adulthood. [8]

PCBs disrupt hormone function.

PCBs with only a few chlorine atoms can mimic the body´s natural hormones, especially estrogen. Women who consumed PCB-contaminated fish from Lake Ontario were found to have shortened menstrual cycles. [9] PCBs are also thought to play a role in reduced sperm counts, altered sex organs, premature puberty, and changed sex ratios of children. More highly-chlorinated PCBs (with more chlorine atoms) act like dioxins in altering the metabolism of sex steroids in the body, changing the normal levels of estrogens and testosterone. [11] PCBs tend to change in the body and in the environment from more highly-chlorinated to lower-chlorinated forms, increasing their estrogenic effects.

Immune system and thyroid effects.

In a study of adolescents Mohawk males in New York State, PCBs were shown to upset the balance of thyroid hormones, which may affect growth as well as intellectual and behavioral development. [12]

Like dioxin, PCBs bind to receptors that control immune system function, disturbing the amounts of some immune system elements like lymphocytes and T cells. [13]

In a study of Dutch children, PCB levels were tied to an increased prevalence of ear infections and chickenpox and with lowered immune system function, and thus greater susceptibility to disease. [14]

Eating fish is the major route of exposure to PCBs.

The most common route of exposure to PCBs is from eating contaminated fish. The EPA estimates an increased cancer risk as high as 1 in 2500 for people eating certain species of fish from the Hudson River&em; thousand times higher than the EPA´s goal for protection. [15]

Air near a contaminated site may also be polluted by PCBs. By one estimate, residents of the Hudson Valley may inhale as many PCBs as they would get by eating one contaminated fish per year. [16] Although small amounts of PCBs can enter the body from swimming in highly contaminated water, this is unlikely to be significant except in the most extreme cases.

Municipalities that use the Hudson River as a drinking water source carefully monitor the water for PCBs, and there are no detectable levels in the water supplies. [17]

PCBs accumulate in the body and in the ecosystem.

Once PCBs enter a person´s (or animal´s) body, they tend to be absorbed into fat tissue and remain there.

Unlike water-soluble chemicals, they are not excreted, so the body accumulates PCBs over years. This means that PCBs also accumulate via the food chain: a small fish may absorb PCBs in water or by eating plankton, and these PCBs are stored in its body fat. When a larger fish eats the small fish, it also eats and absorbs all the PCBs that have built up in the small fish. In this way, larger fish and animals can build up a highly concentrated store of PCBs. Some types of PCBs may degrade into nontoxic form while they are stored in the body, but this process can take many years.

In the same way, PCBs accumulate in women and pass on to their infants through breast milk. This accumulation means that nursing infants may ingest PCB levels much higher than the levels in fish and other foods consumed by their mothers. [18]

PCBs have been found all over the world, including significant amounts in the Arctic and Antarctic, far from any sources. In fact, several studies have found very high levels of PCBs in the blood and breast milk of Inuit women. [19] It is thought that PCBs spread through the air, after evaporating from contaminated water and sediments, as well as through the water.

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For More Information

For more information on PCB health effects, we recommend starting with these two papers:

Carpenter, D. O. (1998). Polychlorinated Biphenyls and Human Health. International Journal of Occupational Medicine and Environmental Health, 11(4): 291-303.

Johnson, B. L. et al (1999). Public Health Implications of Exposure to Polychlorinated Biphenyls (PCBs). Agency for Toxic Substances and Disease Registry. Online at

For details on the EPA´s risk assessment for human health in the Hudson Valley, and for details of the proposed cleanup plan, see
EPA (2000). Hudson River PCBs Reassessment RI/FS Phase 3 Report: Feasibility Study. U. S. Environmental Protection Agency, and U. S. Army Corps of Engineers. Online at

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[1] Summarized in ATSDR (2000) and Johnson et al (1999)
[2] Summarized in Johnson et al (1999)
[3] See the discussion of the Yusho and Yu-Cheng episodes, in Johnson et al (1999) and elsewhere.
[4] Jacobson and Jacobson (1996)
[5] Taylor et al, summarized in Johnson et al (1999).
[6] Stewart et al (2000)
[7] Gray et al (1995)
[8] Weinand-Harer et al (1997)
[9] Mendola et al (1997)
[11] Arcaro et al (1999)
[12] Schell et al (2000)
[13] Summarized in Carpenter (1998)
[14] Weisglas-Kuperus et al (2000)
[15] EPA (2000), Table 1-9.
[16] David Carpenter, personal communication.
[18] Korrick and Altshul (1998)
[19] Summarized in Johnson et al (1999)

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Arcaro, K. F. et al 1999. Antiestrogenicity of environmental polycyclic aromatic hydrocarbons in human breast cancer cells. Toxicology, 133: 115-127.

ATSDR (2000). Toxicological Profile for Polychlorinated Biphenyls. Agency for Toxic Substances and Disease Registry.

Carpenter, D. O. (1998). Polychlorinated Biphenyls and Human Health. International Journal of Occupational Medicine and Environmental Health, 11(4): 291-303.

EPA (2000). Hudson River PCBs Reassessment RI/FS Phase 3 Report: Feasibility Study. U. S. Environmental Protection Agency, and U. S. Army Corps of Engineers. Online at

Gray, L. E. et al 1995. Functional Developmental Toxicity of Low Doses of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin and a Dioxin-Like PCB (169) in Long Evans Rats and Syrian Hamsters: Reproductive, Behavioral and Thermoregulatory Alterations. Organohalogen Compounds, 25: 33.

Jacobson, J. L. and Jacobson, S. W. (1996). Intellectual Impairment in Children Exposed to Polychlorinated Biphenyls in Utero. New England Journal of Medicine, 335(11): 783-789.

Johnson, B. L. et al (1999). Public Health Implications of Exposure to Polychlorinated Biphenyls (PCBs). Agency for Toxic Substances and Disease Registry. Online at

Korrick, S. A. and Altshul, L. 1998. High Breast Milk Levels of Polychlorinated Biphenyls (PCBs) among Four Women Living Adjacent to a PCB-Contaminated Waste Site. Environmental Health Perspectives, 106(8): 513.

Mendola, P. et al, 1997. Consumption of PCB-contaminated Freshwater Fish and Shortened Menstrual Cycle Length. American Journal of Epidemiology, 145(11): 955.

Safe, S. H. (1994). Polychlorinated Biphenyls (PCBs): Environmental Impact, Biochemical and Toxic Responses, and Implications for Risk Assessment. Critical Reviews in Toxicology, 24:(2): 87-149.

Schell, L. M. et al 2000. Polychlorinated biphenyls and thyroid function in adolescents of the Mohawk Nation at Akwesasne. In Proceedings of the Ninth International Conference, Turin, Italy.

Stewart, P. et al 2000. Prenatal PCB exposure and neonatal behavioral assessment scale (NBAS) performance. Neurotoxicology and Teratology, 22: 21-29.

Weinand-Harer, A. et al 1997. Behavioral effects of maternal exposure to an ortho-chlorinated or a coplanar PCB congener in rats. Environmental Toxicology and Pharmacology, 3: 97-103.

Weisglas-Kuperus, N. et al 2000. Immunologic Effects of background Exposure to Polychlorinated Biphenyls and Dioxins in Dutch Preschool Children. Environmental Health Perspectives, 108(12): 1203.

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