Cancer and the Environment : Part 3

by National Cancer Institute

(Page 3 of 5)

Other Viruses

Epstein-Barr virus causes mononucleosis. In people with weakened immune systems, it can also lead to some types of lymphoma.

People with weakened immune systems may also be at risk for a cancer called Kaposi's sarcoma if they are infected with human herpesvirus 8 (also known as Kaposi's sarcoma-associated herpesvirus, or KSHV). In the United States, KSHV infection is most common in homosexual men.

Helicobacter pylori

A bacterium called Helicobacter pylori (H. pylori) is the primary cause of stomach ulcers and inflammation of the stomach. H. pylori can contribute to the development of stomach cancer, but most infections lead to neither symptoms nor cancer.

Ultraviolet (UV) Radiation

Ultraviolet radiation--which comes from natural sunlight, sunlamps, or tanning beds--can lead to melanoma and other forms of skin cancer. While some sun exposure is good for health, excessive exposure during childhood seems a particularly important factor that increases skin cancer risk, and repeated exposure as an adult can increase risk as well.

If possible, avoid sun exposure between 10 am and 4 pm. Wear protective clothing and use sunscreen. Do not use tanning beds or other types of artificial UV exposure.

Ionizing Radiation

Invisible high-energy rays called ionizing radiation can damage the body's DNA and genes, possibly enabling cancer-related mutations. There are several sources of ionizing radiation, including cosmic rays, radon, fallout from atomic bombs or above-ground nuclear testing, and screening or diagnostic X-rays.

We are all exposed to the ionizing radiation from the cosmic rays that enter earth's atmosphere from outer space. This radiation may account for a very small percentage (about 1 percent) of our total cancer risk.

Radon

Radon, a naturally occurring radioactive gas found at low levels in most soil, is produced in the soil when the element uranium starts to break down. The health effects of high radon levels were first seen in the increased cases of lung cancer found in underground uranium miners in the United States and around the world. Radon gas seeps into cracks in the foundation of homes from surrounding soil; about 1 in 20 homes has elevated radon levels. Research estimates that about 20,000 lung cancer deaths every year may be linked to radon exposures in homes.

Check the radon levels in your home regularly. A ventilation system in your basement can dramatically reduce radon levels.

Nuclear Fallout

Atomic bombs and above-ground atomic bomb testing releases ionizing radiation that can increase cancer risk. People affected by the atomic bombs in Japan at the end of World War II, those living near nuclear testing sites in Nevada in the late 1950s and early 1960s, and those near the site of the Chernobyl nuclear power plant accident in the former Soviet Union in 1986 were all exposed to ionizing radiation.

Japanese atomic bomb survivors had increased rates of cancers of the breast, thyroid, lung, stomach, and other organs. People, especially children, exposed to iodine-131 (one form of radioactive iodine) both from the above-ground nuclear testing that has occurred in the United States and from the Chernobyl accident, have an increased risk of thyroid cancer.

Diagnostic and Screening X-rays

X-rays, mammograms, and radiation therapy all involve exposure to ionizing radiation. An X-ray of the chest exposes a patient to only a small amount of radiation--about the same as one gets from two airplane flights across the United States.

Studies have not shown an elevated cancer risk associated with X-rays taken to diagnose a disease or condition. One exception to this is in children whose mothers received X-rays while pregnant: the children were found to have increased risks of leukemia and other types of cancers. Because of this finding, X-rays to diagnose a condition in pregnant women are no longer recommended.

Talk with your doctor about the need for each X-ray that he or she suggests. Ask about shields to protect other parts of your body during an X-ray.

Radiation Therapy

Radiation to treat a condition--such as cancer or ringworm--is more likely to increase cancer risk. For example, people who receive radiation to treat conditions of the head and neck have an increased risk of thyroid cancer and of tumors of the head and neck.

Pesticides

About 20 ingredients in pesticides have been found to cause cancer in animals. Studies of people with high exposure to pesticides--farmers, crop duster pilots, pesticide manufacturers--have shown higher rates of blood and lymphatic system cancers in these people, as well as melanoma and cancers of the lip, stomach, brain, lung, and prostate.

Medications

Some chemotherapy drugs used to treat cancer may increase the risk of second cancers later in life. Drugs that suppress the immune system--used to treat some cancers as well as to prepare patients receiving organ transplants--also are associated with increased risk of cancer, particularly lymphoma.

On the other hand, new estrogen-blocking drugs called aromatase inhibitors can decrease the recurrence of breast cancer.

Any medication carries risks and benefits, so always check with a health professional before starting a new drug.

About the Author

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