Exposure to natural and man-made substances in the environment accounts for at least two-thirds of all the cases of cancer in the U.S.

Exposure to a wide variety of natural and man-made substances in the environment accounts for at least two-thirds of all the cases of cancer in this country.

These environmental factors include lifestyle choices like cigarette smoking, excessive alcohol consumption, poor diet, lack of exercise and excessive sunlight exposure. Other factors include exposure to certain medical drugs, hormones, radiation, viruses, bacteria, and chemicals that may be present in the air, water, food and workplace.

It's no surprise that pesticides, radiation, certain chemicals, and second-hand smoke are hazardous. These environmental factors can raise a person's risk of getting cancer. Regulatory control, safe work environments, and product testing can help reduce these risks, but the link between cancer and the environment remains.

Understanding what factors in the environment affect our health is difficult, and it is often hard to separate fact from fiction. Here are the facts on some key environmental exposures:

Magnetic Fields: Electromagnetic fields (EMFs) are emitted from devices that produce, transmit, or use electric power. Some sources of EMFs are power lines, transmitters, and household electronics like televisions, microwave ovens and electric blankets. Over the past 15 years, there have been several studies of children and adults evaluating their residential exposure to electric and magnetic fields in relation to risks of brain cancer, leukemias and lymphomas, and breast cancer. Most findings have been inconclusive or negative.

• If you are concerned about the affect of EMFs on your health, you can take the following steps:
• Avoid standing too close to microwaves, computers, and other devices that emit EMFs
• Turn off devices such as electric blankets when you're not using them
• Discourage children from playing near power lines

Radon: Radon is a radioactive gas released from normal decay of uranium in rocks and soil. It is the second leading cause of lung cancer in the United States and is associated with 15,000-20,000 lung cancer deaths annually. Radon can enter homes through cracks in floors, walls, or foundations, and also can be released from building materials or from water obtained from wells. About one in 15 U.S. homes are estimated to have radon levels that exceed the standard set by the U.S. Environmental Protection Agency (EPA) - 0.4 picocuries per liter.

• If you suspect you may have high levels of radon in your home, your best defense is to test for it. Short- and long-term tests are available, but experts recommend using a long-term test as it gives a more accurate reading. Tests can be purchased at home improvement stores. Also, when purchasing a new home, ask your realtor to check radon levels during home inspections. The EPA recommends taking action to reduce radon in homes with high levels (see above). Scientists estimate that lowering radon levels can reduce lung cancer deaths by 2-4 percent.

Environmental Tobacco Smoke (Secondhand Smoke): Scientists estimate that secondhand smoke is responsible for 3,000 lung cancer deaths each year. Reports also conclude that children of parents who smoke have more respiratory symptoms and acute lower respiratory tract infections, as well as reduced lung function. Separating smokers and nonsmokers within the same space, like a restaurant, may lower but does not eliminate a nonsmoker's exposure to secondhand smoke. In addition, while most research has focused on lung cancer, secondhand smoke has also been linked to other cancers, including nasal sinus cavity, cervix, breast and bladder.

• Sometimes it's hard to avoid secondhand smoke. Try to avoid or limit your time in smoky places. If family members smoke, ask them to smoke outside and be sure to monitor children's exposure to smoke. Some municipalities even have laws that regulate whether neighbors can smoke next door to one another.

Pesticides: Pesticides are used to help maintain the agriculture food supply, but some can pose a danger as well. Therefore, it is crucial that pesticides be used properly and continue to be studied. High quantities of some pesticides have been linked to cancer. Scientists are exploring whether pesticides affect the health of farmers and their families, and there is evidence that those who handle pesticides regularly are at greater risk.

• The use of pesticides is regulated. However, when eating vegetables or fruits, be sure to wash them well before eating. Those who work in agricultural fields or who may handle pesticides should take special precautions to avoid contact with pesticides. If contact occurs, wash the skin thoroughly. Also, wearing the proper protective equipment is crucial to prevent exposure.

Case Example: John Martin is proud of the solid brick house his father built in the mid-1930s on Iowa farmland. John brags that he helped his father build the house, and that it was so well-constructed and airtight that they have never had problems with Iowa's cold and heat. He and his sister grew up in the house, and he, his wife, and his oldest daughter now live there. Then John's sister, who lives nearby, is diagnosed with lung cancer. Soon after, his daughter, who is in her mid-40s, starts to develop shortness of breath and coughing. She undergoes a battery of medical tests and is eventually diagnosed with lung cancer. A savvy local public health official recommends testing for radon in the house and finds that the levels are off the chart.

Mary Jordan has been trying to get her husband to quit for over 20 years. She is worried about him getting lung cancer. He smokes constantly -- while watching TV, eating dinner and even driving. But he has never had any health problems. While Mary is at her annual physical, however, her physician notices a lump in her lung after a routine x-ray. He recommends that she gets a biopsy to help explain the x-ray results. To her horror and disbelief, the tests show that she has lung cancer. Her husband is very worried and feels responsible for her illness. While visiting his wife in the hospital, he signs up to be in a support group for people trying to quit smoking.