What Causes Cancer?
Cancer is a complex group of diseases with many possible causes. In this section you can learn more about the known causes of cancer, including genetic factors; lifestyle factors such as tobacco use, diet, and physical activity; certain types of infections; and environmental exposures to different types of chemicals and radiation.
Genetics and Cancer, family cancer syndromes
Cancer is such a common disease that it is no surprise that many families have at least a few members who have had cancer. Sometimes, certain types of cancer seem to run in some families. Sometimes, this is because family members have certain risk factors in common, such as smoking, which can cause many types of cancer. It can also be due in part to other factors, like obesity, that tend to run in families and influence cancer risk.
But in some cases the cancer is caused by an abnormal gene that is being passed along from generation to generation. Although this is often referred to as inherited cancer, what is inherited is the abnormal gene that can lead to cancer, not the cancer itself. Only about 5% to 10% of all cancers result directly from gene defects (called mutations) inherited from a parent.
Advances in science have improved our knowledge of the inner workings of cells, the basic building blocks of the body. All living things are made of cells. Complex animals such as humans have trillions of cells. Cells work together to form organs, such as the heart, liver, and skin. Human bodies have several organ systems.
Cancer begins when genes in a cell become abnormal and the cell starts to grow and divide out of control.
Carcinogens in Tobacco Products, Tobacco smoke
Cigarettes, cigars, and pipe tobacco are made from dried tobacco leaves. Other substances are added for flavor and to make smoking more pleasant. The smoke from these products is a complex mixture of chemicals produced by the burning of tobacco and its additives.
Tobacco smoke is made up of more than 7,000 chemicals, including over 70 known to cause cancer (carcinogens). Some of the chemicals found in tobacco smoke include:
Nicotine (the addictive drug that produces the effect people are looking for and one of the harshest chemicals in tobacco smoke)
Methanol (wood alcohol)
Acetylene (the fuel used in welding torches)
The poison gases carbon monoxide and nitrogen oxide
Polynuclear aromatic hydrocarbons
Many of these substances cause cancer. Some cause heart and lung diseases, too. All of these products can be deadly.
Diet and Physical Activity: What’s the Cancer Connection?
How much do daily habits like diet and exercise affect your risk for cancer? Much more than you might think. Research has shown that poor diet and not being active are 2 key factors that can increase a person’s cancer risk. The good news is that you do something about this.Besides quitting smoking, some of the most important things you can do to help reduce your cancer risk are:
Get to and stay at a healthy weight throughout life.
Be physically active on a regular basis.
Make healthy food choices with a focus on plant-based foods.
The evidence for this is strong. The World Cancer Research Fund estimates that about 20% of all cancers diagnosed in the US are related to body fatness, physical inactivity, excess alcohol consumption, and/or poor nutrition, and thus could also be prevented.
Sun and UV Exposure
Learn more about the link between too much sun exposure and cancer.
Does UV radiation cause cancer?
Yes. In fact, most skin cancers are a direct result of exposure to the UV rays in sunlight. Both basal cell and squamous cell cancers (the most common types of skin cancer) tend to be found on sun-exposed parts of the body, and their occurrence is typically related to lifetime sun exposure. The risk of melanoma, a more serious but less common type of skin cancer, is also related to sun exposure, although perhaps not as strongly. Skin cancer has also been linked to exposure to some artificial sources of UV rays, such as the solarium.
Radiation Exposure and Cancer
X-rays, Gamma Rays, and Cancer Risk
When talking about radiation and cancer risk, it is often x-rays and gamma rays that people think about.
Cancer Compensation Programs for People Exposed to Radiation as Part of Nuclear Weapons Testing
Between 1945 and 1962, several countries tested nuclear weapons in the open air. The US government has passed several laws to compensate military veterans, people who worked in the nuclear industry, and others exposed to radiation as part of nuclear testing programs who later develop certain types of cancer or other diseases.
*Infectious Agents and Cancer
In the United States and other developed countries, a small portion of cancers are thought to be linked to infections.
*At Home and around the home, including radon, lead, and arseni, contained in products such as cosmetics, hair dyes, and cell phones.
*In the Workplace For some people, the workplace can be a source of exposure to some potentially harmful substances, such as asbestos, benzene, or formaldehyde.
*Pollution these are some common sources of pollution, what are all around us: secondhand smoke, benzene, radon, diesel exhaust…
*Medical Treatments medical tests and treatments can be an important part of getting and staying healthy. But some types of tests and treatments may actually increase a person’s risk of developing cancer.