Cancer Exposure and Risk (Part 1)
The cause of many cancer types is unknown and likely determined by the combined effects of multiple factors. However, major risk factors for cancer include lifestyle choices such as tobacco use, unhealthy diet, lack of exercise and sun exposure. Genetic factors also appear to play a role in several types of cancer.
Although environmental pollution has been a source of great public concern for decades, there have only been a few well-studied cases of environmental exposures at the community-level. The cancer risks associated with many environmental chemicals are based on studies in the workplace, where exposures are often much greater than they would be in the general public. These earlier studies provide the foundation for building evidence that supports a link between cancers and exposures to environmental pollutants.
Some environmental exposure is potentially avoidable. For example, exposures related to tobacco smoking, can be avoided with behavioral changes. Other environmental factors are less controllable such as carcinogenic compounds released into the ambient air. Furthermore, some risk factors are unavoidable such as age, race or other genetic susceptibilities. It is important to remember that having a risk factor only increases the chances that a person will develop cancer, it does not mean the individual will for sure develop cancer. Also, many people who develop cancer do not have many or any of the currently known risk factors.
Female Breast Cancer Exposure and Risk
The exact causes of breast cancer are unknown; however, women in certain categories are at increased risk for breast cancer. Known risk factors include:
- Older age
- White ethnicity
- Obesity (after menopause)
- Dense breast tissue (after menopause)
- High estrogen levels
- Unusually tall
- Early onset of menstruation
- Later age pregnancy
- Having no or few children
- Late onset of menopause
- Family history of breast cancer
- Certain genetic mutations
- Certain types of benign breast disease
- History of breast cancer
- Post-menopausal hormone use
- Heavy alcohol consumption
- Cigarette smoking
- Exposure to secondhand cigarette smoke
- Current or recent use of birth control pills
- Low levels of physical activity
- Never breast feeding or short duration of breast feeding
Lung Cancer Exposure and Risk
Smoking-the most important risk factor a person can control-is the most common cause of lung cancer.
Even for nonsmokers, exposure to secondhand cigarette smoke increases the risk for lung cancer. According to the 2006 Surgeon General's Report, the evidence suggests that secondhand smoke exposure can cause lung cancer in lifetime nonsmokers, regardless of where the exposure occurs (home, work, restaurants, etc.).
Studies also indicate that exposure to certain chemicals, such as arsenic, chromium, and silica, substances used or produced in foundries, and substances produced by processing coal may increase the risk for lung cancer, especially among smokers.
Another risk for lung cancer is exposure to radon gas. Radon can be found throughout the United States. It can infiltrate homes, offices, and schools and cause high indoor radon levels. The greatest exposure likely occurs in homes where most personal time is spent. Radon levels can be reduced in these environments with the installation of the proper equipment.
Bladder Cancer Exposure and Risk
Smoking is the greatest risk factor associated with bladder cancer. Persons who smoke have more than twice the risk for bladder cancer than non-smokers. Research indicates that smoking causes approximately 20%-30% of bladder cancers among women and 50%-65% among men.
Workplace exposures may also increase the risk for bladder cancer. Studies show that workers in the trucking, dye, rubber, textile, leather, and chemical industries have a higher risk for bladder cancer. Approximately 5%-25% of bladder cancers among men and 8%-11% among women are associated with occupational exposures.
Ingestion of high levels of inorganic arsenic can cause cancer. The effect of low-to-moderate arsenic levels in drinking water is less definitive. Long-term exposure to disinfection byproducts in drinking water may also cause a small increase in the risk for bladder cancer. Public water suppliers disinfect their water to kill viruses and bacteria. Disinfection by-products are a family of chemicals formed when drinking water disinfectants react with naturally occurring organic matter and other substances in the source water.