Cigarette smoking causes lung cancer, as well as cancers of the esophagus, larynx, mouth, throat, kidney, bladder, pancreas, stomach and cervix. Other tobacco products (such as smokeless tobacco, cigars and pipes) also increase cancer risk. Smoking is the leading cause of premature, preventable death in the U.S. and much of the world; 79,000 men and 56,000 women in the U.S. die annually from lung cancer caused by cigarette smoking. In addition, about 3,000 nonsmokers die from lung cancer each year in the U.S. due to secondhand smoke. If you use tobacco, quitting is by far the most important step you can take to protect your health. It is never too late to quit.
Studies suggest that obesity contributes to about 14 percent of the cancer deaths of American men and 20 percent of those in women. Obese people are at greater risk of developing colorectal, esophageal, gallbladder and liver cancer, leukemia, multiple myeloma and non-Hodgkin’s lymphoma. In addition, obese postmenopausal women are at increased risk for breast and uterine cancer. Lab studies show that fat cells increase blood levels of hormones that can fuel the growth of certain types of cancers. Obesity is also linked to chronic inflammation in the body, which can contribute to cancer development.
Activity is important in cancer prevention—not just because it can help control weight. Exercise may reduce risk by lowering hormones and cellular growth factors, improving insulin resistance and, in moderation, enhancing the immune system. The best evidence of potential benefit concerns colorectal cancer. The effect on breast cancer risk has been studied a lot, with mostly positive results. For prostate, lung and endometrial cancers, research is promising but less consistent. It's hard to tease out whether it’s the exercise, healthy lifestyle or both that lower risk. It's also unclear what kind of exercise is most beneficial and at what age you need to start.
Consume a high-fiber diet as close to vegetarian as possible. Eat at least five (or, better, nine) servings of a variety of vegetables and fruits daily. Limit red meat and pork, especially processed meats. Choose whole grain over refined. Avoid salty and salt-preserved foods. Don’t be confused by studies that suggest fruits and vegetables do little to reduce risk. There are many types of produce—and cancer—so specific connections may be hard to spot. It's possible that your genes determine if, and how much, certain fruits and vegetables protect you, and that what you ate when you were young plays a key role in preventing or promoting cancer.
Cooking high-protein foods (poultry, meat, fish) over coals or flames at high temperatures creates polycyclic aromatic hydrocarbons (PAHs) and heterocyclic amines (HCAs), thought to increase cancer risk. This is true for any high-heat method, such as pan-frying. Studies show very high levels of these compounds can cause many types of cancer in rodents. Observational studies find that people who eat lots of charred foods like fried or barbecued meat are at higher risk for colorectal, pancreatic and prostate cancer. If you cook this way, precook meat in the microwave for a few minutes, then turn it frequently while cooking to help reduce HCAs and PAHs.
Alcohol increase the risk of various cancers, and the more you drink, the greater the risk. The evidence is strongest for cancers of the esophagus, mouth, throat and larynx. Your risk is greater if you drink and smoke. Research also suggests that alcohol may also increase the risk of liver, colorectal and breast cancer. In particular, if you are at high risk for breast cancer, or have had breast cancer, you should consider not drinking or drink only occasionally. If you drink, do so in moderation. Women should consume no more than one drink a day; men, no more than two drinks a day. Those over 65 should drink even less.
Ultraviolet radiation from the sun or tanning beds is responsible for the great majority of the two million cases of skin cancer diagnosed annually in the U.S. Most are basal cell carcinomas, which rarely spread. Many others are squamous cell carcinomas, which start as skin lesions called actinic keratoses. About two-thirds of all cases of melanoma, the most dangerous skin cancer, can be attributed to sun exposure. Used properly, sunscreen reduces the risk of most skin cancers. But most of us don’t use enough sunscreen or reapply it as often as needed. Don’t let sunscreen give you a false sense of security, since no product blocks 100 percent of the sun's rays.
Americans, on average, are exposed to six times more radiation from medical imaging, especially CT scans, than they were three decades ago. The risk from a single CT scan, appropriately done, is minuscule, but radiation exposures add up over a lifetime. Before undergoing a diagnostic scan, ask if the test is necessary and improves your health care. Also ask if there is an equally good nonradiation alternative, such as ultrasound or MRI. Make sure imaging tests are done only when the benefit is clear and outweighs risks—and that the minimal level of radiation will be used. Before having any imaging scan, discuss the pros and cons with your doctor.
A colorless, odorless radioactive gas formed during the natural breakdown of uranium in soil, rock and water, radon is related to about 15,000 to 20,000 annual lung cancer deaths in the U.S. Exposure to radon is the second leading cause of lung cancer. People who smoke and are also exposed to radon have the highest risk of developing lung cancer. Radon can get into your home through cracks and holes in floors, walls or foundations and be released from building materials and well water. Testing is the only way to know if your home has high radon levels. To find out about radon testing, call the National Radon Hotline at 800–55–RADON or go to EPA.gov/radon.
If you live in a rural area and get water from a private source, such as a well, have it tested for arsenic, a tasteless, odorless chemical element naturally in rocks, soil, water and air. Exposure to high levels of arsenic has been linked to cancers of the bladder, colon, kidney, liver, lung and skin. (If your water comes from a public drinking water system, you probably don’t need to worry about arsenic.) If arsenic levels are high, switch to bottled water. Water filters don't remove arsenic. For more on water testing, call the EPA’s Safe Drinking Water Hotline at 800-426-4791.
Exposures to workplace carcinogens cause an estimated 40,000 new cancer cases and 20,000 cancer deaths in the U.S. annually. Bartenders and waitstaff may be exposed to secondhand smoke; workers in chemical plants, gasoline-related industries and printing to benzene; and workers in the funeral industry and hair and nail salons to formaldehyde. If you think your job exposes you to carcinogens, check government regulations for your workplace. You can also download a government guide to occupational chemical hazards at cdc.gov/niosh/npg.
About one in every 28,000 Americans may develop cancer due to outdoor air pollutants. But more than 2 million people live where the lifetime cancer risk is particularly high. Go to AirNow.gov for local air quality reports. If the air quality is bad, go to the gym or spend time indoors; limit time outside during peak traffic and walk along side streets, not busy roads. To help keep the air cleaner, carpool or use public transportation, reduce or eliminate fireplace and wood stove use, don't use gas-powered lawn and garden equipment and don't burn leaves or other materials.
Home air can often be more polluted than outdoor air. Tobacco smoke is by far the worst pollutant. Cleaning products, mothballs and manufactured wood products can release volatile organic compounds (VOCs); some are known or suspected carcinogens. Plywood and other manufactured wood products can release formaldehyde. Limit exposure to these sources, open windows and doors often and use venting systems in bathrooms, kitchens and any room with a fireplace, wood stove or range. Avoid incense, air fresheners or scented candles.