Which of these is not a carcinogen?

A. Cigarette smoke

B. Testosterone

C. UV light

D. Fat

E. All of the above are carcinogens

Graph showing the link between cigarette smoking and lung cancer
Graph showing the link between cigarette smoking and lung cancer

The correct answer is E. All of the above are carcinogens.

Cancer is a group of illnesses that all have the characteristic of uncontrolled cell division, sometimes resulting in the development of one or more tumors.

The cell cycle has at least two checkpoints during which DNA is checked for abnormalities. Usually, the DNA is repaired or the defective cell is programmed to self-destruct.

However, as we age and as we are exposed to carcinogens our cell’s ability to detect and repair damaged genetic material decreases. This means that most often cancer is more likely as we become older.

A carcinogen is an agent that has been shown to cause cancer. Today thousands of people are diagnosed with cancer leading to costly and unpleasant treatments, great disability and death. Researchers have spent considerable time investigating what causes certain types of cancer.

Chemicals found in cigarettes and many industrial chemicals are known to cause cancer. Even body fat percentage and our hormone levels can influence our risk of cancer.

People who follow a diet in which excessive saturated fat is consumed, and who do not exercise seem to have a greater risk of certain types of cancer over time.

Other environmental factors, including exposure to sunlight, is also important. In fact, frequent sunburns from UV radiation exposure does increase the risk of developing skin cancers such as basal cell carcinoma and melanoma.

What is cancer?

Cancer is a term used to describe different diseases that all are characterized by cell division that has gone out of control. These cells often replace and destroy healthy cells in the body, and in some cases, a tumor or multiple tumors can result.

The cancerous conditions are often the result of problems with the cell cycle, which is more likely as a person ages. This is why most types of cancer are more common when people become older.

Our cells have various checkpoints during the cell cycle during which DNA is checked for damage. The cells then are either programmed to self-destruct, if the damage is detected, or DNA repair is done to fix the mistakes.

This system does not work as well as we age and so mistakes are more likely to not be recognized resulting in these aberrant cells dividing leading to cancer.

Besides aging, many agents can cause DNA damage. These agents that have been implicated as causing cancer are known as carcinogens.


Some carcinogens are more obvious than others, and certainly, most people realize that chemicals such as those found in cigarettes can cause cancer. Studies have indicated the strong link between smoking cigarettes and the incidence of lung cancer.

Several chemicals are now known to be carcinogenic including, for instance, asbestos, benzene, chromium, arsenic, formaldehyde, herbicides, and vinyl chloride.

This means that people working in various industries may be at risk of developing cancer if they are not careful to avoid exposure to these chemicals.

Diet and hormones

Diet can also play a role in the development of cancer, and in fact, studies have found that a high intake of saturated fat does increase the risk of developing breast cancer.

Increased body fat has also been linked to a higher risk of developing colon cancer, particularly in people who have a high body mass index and who live a sedentary life.

There is much controversy over the relationship between testosterone and prostate cancer. Researchers have speculated that more of the hormone would increase prostate cancer risk, but the evidence is very limited in this regard.

It has however been found that men with less testosterone have a decreased risk of developing this cancer. More research studies need to be done to determine the link between this hormone and prostate cancer.

The hormone estrogen is believed to be a strong risk factor for breast cancer. In fact, many researchers have found that elevated levels of this hormone do appear to be a strong predictor of the occurrence of breast carcinogenesis.

This is also linked to fat tissue which appears to help produce the hormone in the breasts. Therefore, breast cancer is more frequently found in women who are significantly overweight and obese.

UV radiation

Ultraviolet radiation from the sun is a potent carcinogen, causing many cases of skin cancer each year. This is particularly the case among Caucasian people living in countries that receive lots of sunlight.

Some exposure to sunlight is needed for a person to stay healthy but it is when people have too much exposure and regularly have sun burns that the cancer risk seems to increase.

Individuals who have a lot of occurrences of sunburns and spend time in the sun are at increased risk of developing malignant melanoma. This is the deadliest form of skin cancer that you get, killing many people every year.

An association has also been found between the use of tanning beds and the development of melanoma and another type of skin cancer, basal cell carcinoma.

This was particularly significant among young people who frequently use tanning beds. This suggests that individuals should be cautious about using tanning beds.


Some types of cancer do have a strong genetic component which does increase the lifetime risk. For instance, in about 50% of breast cancer cases, genetic mutations of BRCA1 and BRCA2 were implicated as possible causes.

These two genes both synthesize a protein that destroys tumors. A mutation stops them from being able to do this, resulting in a higher risk of breast cancer.


  1. JD Yager, NE Davidson (2005). Estrogen carcinogenesis in breast cancer New England Journal of Medicine.
  2. S Sieri, V Krogh, P Ferrari, F Berrino, V Pala, et al. (2008). Dietary fat and breast cancer risk in the European Prospective Investigation into Cancer and Nutrition. The American Journal of Clinical Nutrition.
  3. Centers for Disease Control and Prevention (2018). Chemicals, cancer and you. Retrieved from cdc.gov.
  4. T Higenbottam, MJ Shipley, G Rose (1982). Cigarettes, lung cancer, and coronary heart disease: the effects of inhalation and tar yield.  Journal of Epidemiology & Community Health.
  5. J Costa (2018). Cancer. Retrieved from Encyclopedia Britannica.


Please enter your comment!
Please enter your name here