Governments Link PCBs and Cancer
Most government health agencies, including those listed below, consider PCBs a "probable carcinogen" for humans and a "known carcinogen" for animals, based on extensive cancer research studies included on these pages. All PCB mixtures cause cancer in animals.
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In 1991, the U.S. Environmental Protection Agency estimated that 38,255 people (or 547 people per year) faced an increased cancer risk in the Great Lakes region over a 70 year lifetime --- due to consumption of fish contaminated with 5 toxic chemicals (PCBs, Mercury, chlordane, DDE/DDT, and Dieldrin --- the last 3 are pesticides). PCBs were considered the dominant risk factor.
The risks were due primarily to consumption of Great Lakes sport fish, plus some consumption of less contaminated commercial and non-Great Lakes sport fish. Reference: U.S. EPA, Region 5. 1991. "A Risk Analysis of Twenty-six Environmental Problems - Draft." Region 5 Comparative Risk Project, Draft Working Documents.
In 1999, the draft Fox River clean-up proposal included a local cancer risk assessment for recreational anglers and subsistence anglers due primarily to consumption of fish containing PCBs. Using fish concentration data from 1990 on (and Walleye data from 1989 in Green Bay), the cancer risks were as high as 1.1 in a 100 for recreational anglers, and 1 in 67 for subsistence anglers. These risks are more than 1,000 times greater than the standard 1-in-a-million cancer risk level used by Wisconsin to regulate hazardous waste sites. These risks are 23 times higher than the cancer risks from fish-eating from Lake Winnebago, which the DNR considers a background level for PCBs (though it’s clear that Lake Winnebago fish are also contaminated.) Reference: ThermoRetec. Feb. 1999. "Draft Feasibility Study, Lower Fox River, Wisconsin, Summary of Baseline Human Health and Ecological Risk Assessment." Section 3.2.1.
In this area, we have roughly 47,000 recreational anglers, based on fishing licenses, and between 2,000 and 5,000 subsistence anglers, based on a variety of surveys. If they all fished the Fox River and lower Bay at average rates, up to 510 recreational anglers, and 30 to 75 subsistence anglers could develop cancer locally over their lifetimes. We hope people are heeding the fish advisories and not consuming contaminated fish, but subsistence fishers often need to fish for financial and/or cultural reasons.
The following are studies which suggest PCBs cause cancer. Government agencies generally require larger and more repeated studies before declaring a substance a "known carcinogen" in humans.
The agencies used the "weight of evidence" approach to classify PCBs as probable human carcinogens. They looked at the cumulative results of the studies below, plus other human studies and the overwhelming evidence that PCBs cause cancer in animals. PCB cancer risk assessments are primarily based on detailed animal cancer studies extrapolated to humans, plus human evidence.
Human cancers are largely due to chemical pollutants and unhealthy lifestyles, not genetics, according to recent research by Paul Lichtenstein of the Karolinska Institute of Stockholm, Sweden, who led a giant study of 89,576 twins and reported results in the New England Journal of Medicine (2000). The researchers found even an identical twin has about a 90% chance of not getting the same cancer as his or her cancer-afflicted twin.
At an Italian capacitor manufacturing plant, researchers studying 290 males and 1,020 females had statistically significant increased numbers of deaths from all types of cancer. In males, there was a statistically significant increase in deaths (roughly 3 times higher) from gastrointestinal tract cancers, otherwise described as higher deaths from cancers of the digestive system, the peritoneum, the lymphatic, and hematopoietic tissues. In females, all causes of death were significantly elevated, and there was a statistically significant excess risk of death from hematologic (blood-based, or leukemia) cancers compared with local, but not national rates. The study looked at workers employed at least 1 week and exposed to PCBs (specifically PCB Aroclor 1254 and 1242, both mixtures present in the Fox River). Reference: Bertazzi, Riboldi, Pesatori, Radice and Zocchett. 1987. "Cancer Mortality of Capacitor Manufacturing Workers," AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, 11:165-76.
In a study in which organochlorine compounds were measured in patients who had died of cancer and patients who had died of other diseases, higher concentrations of PCB and DDE were found in the samples for the cancer patients. The mean PCB adipose (fat) levels in 11 male cancer patients was 8.8 mg/kg and in 212 non-cancer patients, 5.9 mg/kg. Although these differences are not large, they were statistically significant. Reference: Unger, M., and Olsen, J. 1980. "Organochlorine compounds in the adipose tissue of deceased people with and without cancer." ENVIRONMENTAL RESEARCH 23: 257-263.
In New York and Massachusetts, researchers found statistically significant excess mortality from cancer of the liver, gall bladder, and biliary tract in a study of 2,588 capacitor manufacturing workers exposed to PCB Aroclors 1254, 1242, and 1016. Reference: Brown, D.P., Jones,M. 1981 "Mortality and industrial hygiene study of workers exposed to polychlorinated biphenyls." ARCHIVES OF ENVIRONMENTAL HEALTH. 36:120-9 Also: Brown, D.P. 1987. "Mortality of workers exposed to polychlorinated biphenyls – an update." ARCHIVES OF ENVIRONMENTAL HEALTH. 42(6):333-339.
A smaller study was inconclusive because of the small sample size, but suggested similar cancer increases. Reference: Gustavsson P, Hogstedt C, Rappe C. 1986. "Short-term mortality and cancer incidence in capacitor manufacturing workers exposed to polychlorinated biphenyls." AMERICAN JOURNAL OF INDUSTRIAL MEDICINE. 10:341-344.
Another small study was also inconclusive because of the small sample size, but was suggestive of increased cancer risk. Reference: Nicholson WJ, Landrigan PJ. 1994. "Human health effects of polychlorinated biphenyls." In: "DIOXINS AND HEALTH" (Schecter A, ed). New York: Plenum, pp. 487-524.
Incidents in Japan and Taiwan where humans consumed rice oil contaminated with PCBs showed liver cancer at 15 times the normal rate, but this has been attributed, at least in part, to heating of the PCBs and rice oil, causing formation of chlorinated dibenzofurans (known as "furans"). However, commercially produced PCBs, such as those used in the Fox River Valley, were routinely contaminated with furans during creation, so BOTH chemicals are present at significant levels in our river. Reference: Urabe H. Koda H, Asahi M. 1979. "Present State of Yusho Patients." ANNULS OF THE NEW YORK ACADEMY OF SCIENCES. 320:273-6. Online: http://www.cdc.gov/niosh/86111_45.html#Toxicity Also: Masuda Y, Yoshimura H. 1984. "Polychlorinated biphenyls and dibenzofurans in patients with Yusho and their toxicological significance: review." AMERICAN JOURNAL OF INDUSTRIAL MEDICINE. 5:31-44. Also: Masuda Y. 1994. "The Yusho rice oil poisoning incident." In: Schecter A, editor. "DIOXINS AND HEALTH." New York: Plenum, p 633-59.
For more details, see PCBs and Liver Cancer in Humans
The study included Mobil employees reported to have had varying exposure to PCB Aroclor 1254.The research and development employees were exposed to PCBs between 1949 and 1957 and refinery plant employees between 1953 and 1958. The extent of exposure to other chemicals is not known. The cancer incidence among these workers for the period 1957 through 1975 was determined using Mobil medical records. Because medical records for 37 employees were incomplete, these workers were excluded from this analysis. Among the 92 workers in these two groups for whom adequate medical records were available, eight cancers (in seven workers) were observed between 1957 and 1975. Of these eight cancers, three were malignant melanoma and two were cancer of the pancreas. This is significantly more skin cancer (melanoma) and pancreatic cancer than would be expected in a population of this size. The remaining cancers were found at three other sites in two employees; sarcoma of the right thigh and multiple myeloma in one employee, and recto-sigmoid cancer in the other. Reference: Bahn AK, Rosenwaike I, Herrmann N, Grover P, Stellman J, O’Leary K. 1976. "Melanoma after exposure to PCBs." Letter. NEW ENGLAND JOURNAL OF MEDICINE. 295: 450 (1976). Also: DHHS (NIOSH), CURRENT INTELLIGENCE BULLETIN 7, polychlorinated (pcbs) November 3, 1975,updated 05-01-1998. Online: http://www.cdc.gov/niosh/78127_7.html
For more details see Skin Cancer and PCBs
For more details see Brain Cancer, PCBs and Dioxin
Many countries are reporting a rapid increase in incidence of non-Hodgkin’s lymphoma.
Recent case-control studies have found associations between non-Hodgkin's lymphoma and PCB concentrations in adipose (fat) tissue (Hardell, 1996) and blood serum (Rothman, 1997). In the Rothman study of persons without known occupational exposure to PCBs, mean PCB blood levels of 13.3 ppb yield highly significant increased odds of non-Hodgkin's lymphoma. Reference: Hardell L, van Bavel B, Lindström G, Fredrikson M, Hagberg H, Lijergren G, Nordstrom M, and Johansson B.. 1996. "Higher concentrations of specific polychlorinated biphenyl congeners in adipose tissue from non-Hodgkin's lymphoma patients compared with controls without a malignant disease." INTERNATIONAL JOURNAL OF ONCOLOGY 9:603-608. Also: Rothman N, Cantor KP, Blair A, Bush D, Brock JW, Helzlsouer K, Zahm SH, Needham LL, Pearson GR, Hoover RN, et al. 1997. "A nested case-control study of non-Hodgkin lymphoma and serum organochlorine residues." LANCET 350:240-244.
In a 1998 study, researchers state: "In epidemiologic studies, non-Hodgkin’s lymphoma (NHL) has been associated with exposure to chemicals such as phenoxyacetic acids; chlorophenols; dioxins; organic solvents including benzene, polychlorinated biphenyls, chlordanes; and immunosuppressive drugs. Experimental evidence and clinical observations indicate that these chemicals may impair the immune system. The risk is increased for NHL in persons with acquired and congenital immune deficiency as well as autoimmune disorders. Also, certain viruses have been suggested to be of etiologic significant for NHL. In some cases of NHL the common mechanism for all these agents and conditions may be immunosuppression, possibly in combination with viruses." Reference: Hardell L, Lindstrom G, van Bavel B, Fredrikson M, and G Liljegren. 1998. "Some aspects of the etiology of non-Hodgkin’s lymphoma." ENVIRONMENTAL HEALTH PERSPECTIVES. 106 (Suppl 2):679-681.
Another study found an association between PCBs and hairy cell leukemia, which is a subgroup of Non-Hodgkin Lymphomas. Researchers found an "increased risk for the sum of the immunotoxic PCB group." Reference: Nordstrom M, et al. 2000. "Concentrations of organochlorines related to titers to Epstein-Barr virus early antigen IgG as risk factors for hairy cell leukemia." ENVIRONMENTAL HEALTH PERSPECTIVES 108(5):441-5.
See also PCBs and Immune System Damage
Researchers have found an association between PCB levels and pancreatic cancers. Reference: Hoppin JA, et al. 2000. "Pancreatic cancer and serum organochlorine levels." CANCER EPIDEMIOLOGY, BIOMARKERS, AND PREVENTION; 9(2):199-205.
In a second study, in a recent issue of the British journal, LANCET, pancreatic cancer patients with a specific gene mutation called K-ras show high levels of DDT, DDE, and PCBs, known as organochlorine compounds. Roughly 78 percent of patients with pancreatic cancer have the K-ras mutation, and scientific studies have established that the mutation is not inherited. This study is the first to suggest that the K-ras mutation is linked to a chemical agent in the environment. "Pancreatic cancer patients with a K-ras mutation have significantly higher levels of DDT, DDE and three major PCBs than pancreatic cancer patients without the mutation or the controls," says the lead researcher, Miguel Porta. But, he adds, "we do not think that organochlorine compounds directly cause the mutations." So what could be happening? "One possibility is that something causes the mutation and then these compounds provide some advantage for the mutated cells to grow," so that instead of dying, for example, a mutated cell continues to grow and multiply. "The other possibility is that these substances enhance the action of mutagens of K-ras." For example, PCBs may push abnormal cells that are still in a pre-cancerous phase into becoming completely cancerous.
For more detailed information, see Pancreatic Cancer, PCBs and Dioxin
A PCB-exposed group in Japan had a statistically significant increase in lung cancer deaths. This was a case involving rice oil contaminated with PCBs and furans. [Some scientists argue that the cancers were due to the furans, not the PCBs; however, commercial mixtures of PCBs generally came contaminated with furans from the manufacturer. The Fox River is contaminated with both PCBs and furans as a result, and both chemicals are picked up and accumulated in fish.] Reference: Kuratsune, Nakamura, Ikeda, & Hirohata. 1987. "Analysis of Deaths Seen Among Patients with Yusho-A Preliminary Report," CHEMOSPHERE, 16:8/9, 2085.
A second study noted that lung cancer deaths among ex-employees at a capacitor plant were higher than might have been expected, but concluded that "there were apparently no grounds for associating lung cancer deaths (although increased above expectations) and exposure in the plant." Reference: Bertazzi, Riboldi, Pesatori, Radice and Zocchett. 1987. "Cancer Mortality of Capacitor Manufacturing Workers," AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, 11:165-76.
A study followed employees who had worked at Monsanto's PCB production plant. The researchers found that the incidence of lung cancer deaths among these workers was somewhat higher than would ordinarily be expected. The increase, however, was not considered statistically significant. Reference: J. Zack & D. Munsch, Mortality of PCB Workers at the Monsanto Plant in Sauget, Illinois (Dec. 14, 1979)(unpublished report), 3 Rec., Doc. No. 11.
For more details, see Lung Cancer and PCBs
A study of workers exposed to PCBs found a consistent increase in kidney cancer, although the actual number of cases was small. Reference: Longnecker, MP, WJ Rogan and G Lucier. 1997. "The human health effects of DDT (dichlorodiphenyltrichloroethane) and PCBs (polychlorinated biphenyls) and an overview of organochlorines in public health," ANNUAL REVIEW OF PUBLIC HEALTH, 18:211-244.
For more details, see Kidney, Bladder & Urothelial Cancer and PCBs
PCBs may cause or promote prostate cancer through early alteration of hormonal development of the male in the womb, and/or through changes in the levels of glutathione enzymes. The International Agency for Research on Cancer (IARC) found an association between PCBs and prostate cancer.
For more details, see Prostate Cancer and PCBs
Our detailed Breast Cancer section includes summaries of 128 studies on the links between breast cancer and exposure to PCBs or dioxin.
At least 24 studies of human populations show a possible link between PCBs and breast cancer. More than 50 additional laboratory studies illustrate in animals or cell cultures how PCBs may cause or promote breast cancer. Also, three studies of humans show a link between dioxin and breast cancer. These last three are important because certain PCBs are dioxin-like and PCBs are frequently contaminated with dioxins.
On the other hand, approximately 13 human studies did not show that PCBs increase breast cancer risk. Nevertheless, several such studies, when re-examined statistically, have found that certain PCBs were associated with risks, or that certain subgroups of women appeared to be more vulnerable to PCBs.
For more details, see Breast Cancer, PCBs and Dioxin
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