PCBs may cause Skin Cancer
Introduction
The following studies show that PCBs may cause or promote skin cancer in humans, particularly the more malignant form of skin cancer known as melanoma. PCBs are considered a "probable carcinogen" by national and international health agencies.
Several occupational studies have shown that workers had higher rates of skin cancer after exposure to PCBs when installing, maintaining and repairing electrical equipment and appliances which, for many years, contained PCBs as lubricant oils or as dielectric fluids in capacitors and transformers. (Old enclosed capacitors and transformers are still allowed to contain PCBs.)
PCBs were also used heavily in the ballasts of fluorescent lights. When PCB-containing equipment heats up during use, PCBs volatilize into the air and settle on work surfaces. Workers were exposed primarily through skin contact and inhalation. Cancers didn’t develop until many years later.
PCBs cause the artificial stimulation of cells. In addition, enzymes induced by PCBs have been shown to convert other chemicals into skin carcinogens. Studies also show a possible association between skin damage (chloracne) caused by PCBs and later development of skin cancer. (see Skin Absorption and Damage.)
PCBs are also known to mimic the human hormone estrogen, which may play a role in stimulating melanoma. Researchers have found that melanoma affects women and men differently: until age 40, women have a higher rate of melanoma than men. Between ages 45-60, the rate of diagnosis in women levels off. The University of California/Irvine College of Medicine researchers have suggested that menopause (caused by a drop in estrogen levels) provides a protective effect which keeps melanoma rates in women from increasing. Even so, over the past 25 years, melanoma has increased in women at a rate of 3.2% each year. [Report form the Society of Investigative Dermatology meeting, May 14, 2001]
Studies have also found that rates of non-Hodgkin's lymphoma have increased in the same countries over the same time periods as skin-cancer rates. In addition, both melanoma and non-melanoma skin cancers occur more often than would be expected among patients who have previously been diagnosed as having non-Hodgkin's lymphoma. Recent research has linked non-Hodgkin’s lymphoma to PCB exposure in combination with certain viruses. The lymphoma appears to develop due to the immune-system damage caused by PCBs. (see PCBs and non-Hodgkin’s Lymphoma, and PCBs and Immune System Damage.)
Melanoma is the most serious form of skin cancer. It is composed of melanocytes, a pigment cell containing melanin granules. Melanin is a dark-brown to black pigment responsible for the coloration of skin, hair, and the pigmented coat of the eye’s retina.
Melanoma accounts for only 4 percent of skin cancer cases, but 75 percent of skin cancer deaths.
Most cases of melanoma are isolated or sporadic, with no apparent family history. Only 10% of melanoma cases run in families; however, genetic factors (such as fair skin and freckles) can make a person more susceptible to skin cancer. Other risk factors include: indoor jobs with alternating intense sunlight exposure, three or more blistering sunburns before age of 20 years, three or more years of outdoor summer teenage jobs, use of certain drugs such as immuno-suppressents, and exposure to chemicals such as coal tars, arsenicals, PCBs, etc.
During the past 10 years the number of cases of melanoma has increased more rapidly than that of any other cancer. Between 1973 and 1993, the incidence of melanoma increased about 4% per year, from 5.7 per 100,000 to 12.2 in 1993. Incidence rates among Caucasians are 20 times greater than among African-Americans. Over 53,000 new cases are reported to the American Cancer Society each year, and approximately 7,800 will die of the disease. It is probable that a great many more occur and are not reported.
Although it is rare in young children, melanoma occurs in every age
group after puberty and is the most
common cancer in young adults of ages 25-29. Among women of ages 30-35
the incidence is exceeded
only by breast cancer. Overall, melanoma is the 6th most common cancer
in males and 7th in females. In the U.S., melanoma incidence now exceeds
that of new HIV infections. The incidence is currently increasing at an
epidemic rate of more than 4% annually, higher than any other cancer. On
the average, there is a melanoma death in the U.S. almost every hour.
The increasing incidence of malignant melanoma in our society may be due to the interrelation of exposure to sunlight with chemical pollution of the environment, including the widespread public exposure to PCBs.
The other, more common forms of skin cancer are basal cell carcinoma and squamous cell carcinoma. These two diseases are most often grouped as non-melanoma skin cancers. The American Cancer Society estimates that about 1.3 million new cases of non-melanoma skin cancers will be diagnosed in the United States this year, making these two combined the most common cancer in the United States.
The National Cancer Institute estimates the overall annual costs for all cancers in the U.S. at $107 billion: $37 billion for all health expenditures, $11 billion for lost productivity due to illness and $59 billion for lost productivity due to premature death. Skin cancers are responsible for a significant portion of these costs, and PCBs may be factor.
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Summary of Results Linking PCBs and Skin Cancer The Studies of Skin Cancer and PCBs Links to More Information Studies Without Abstracts References
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