Environmental Factors

Environmental Factors

This article reviews environmental factors in the development of cancer. Cancer risk factors can be generally divided between modifiable and non-modifiable risk factors. Having several relatives with breast cancer increases your risk for breast cancer and is a non-modifiable risk factor. Smoking 3 packs of cigarettes a day is a modifiable risk factor for lung cancer. Having several relatives with lung cancer and smoking heavily is an example of having both modifiable and non-modifiable risk factors. Environmental risk factors may be classified into both modifiable and non-modifiable, and this depends upon what is meant by environmental factors.

Exposure to cigarette smoke is a known risk factor for lung cancer. Second hand smoke in the surrounding environment would be one type of environmental risk factor. This risk factor might be thought of as modifiable for an adult who can choose not to be around it but non-modifiable for a child who really has no choice but be exposed to smoke in the home.

Great energy and time has been spent to investigate so-called “cancer clusters.” For example, if a particular town or neighborhood has a number of people develop pancreatic cancer or leukemia this might be called a cancer-cluster. If the number of cancers exceed the expected amount based upon pure statistics it causes some to wonder if something in the environment has caused this. Sometimes this curiosity causes people to prematurely assign blame to supposed “toxins” in the air, water or food.

One example of a cancer cluster is the high rate of thyroid cancer occurring near Chernobyl, the site of a famous nuclear power plant accident. Another example of cancer cluster being related to the environment was the increase in lung cancer (specifically the mesothelioma type of pleural disease) seen in ship workers/builders who were exposed to large amounts of asbestos. This risk was compounded because many of the ship workers also smoked heavily. It is not uncommon common for cancers to be related to the synergistic effect of two or more carcinogens.

Occupational hazards and workplace exposure to carcinogens are types of environmental risk. For the ship builders this involved the constant exposure to asbestos products and inhaling the tiny fibers that are strongly related to lung disease and cancer. Excessive sunlight exposure would be another example of a type of workplace exposure if your employment required the employee to be outside a lot. Excess sunlight exposure is a major risk factor for skin cancer. The ultraviolet light (specifically UV-B rays) has carcinogen effects on the DNA of skin cells.

Another type of workplace hazard might be exposure to ionizing radiation. People who work in a radiology imaging department or in a lab that uses radioactive products might be exposed. Typically workers at risk should have radiation exposure badges that keep track of radiation levels to ensure safe exposure. We cannot avoid radiation exposure. The atmosphere permits radiation exposure in small amounts and this is worse if one lives at higher altitudes. Every time someone takes a long airplane ride they get exposed to the amount of radiation that is the equivalent of a simple chest x-ray.

In addition there are many other industrial chemicals that are potential solvents. We may be exposed to these as a factory worker or by coming in contact with the product containing the carcinogen. Examples of these would be chromium, cadmium, beryllium, and arsenic. These metals might be found in various products such as pesticides, automotive parts and plastic products. Various solvents such as paint thinners, grease removers and dry cleaning agents can also have aromatic carbons (i.e. chemical such as benzene or chloroform) that have been linked to cancer. Federal guidelines regulate hazardous materials at the workplace, and a business should have a means to notify their employees of hazardous materials they will come in contact with.

Exposure in the environment to infectious agents is another type of cancer risk. Common examples of infectious agents identified as carcinogens include; human papilloma virus (HPV), hepatitis C virus (HCV), and the bacterium helicobacter pylori.

It may seem overwhelming to consider the potential numbers of environmental factors that can contribute to cancer development. Similar principles as with all cancer prevention might apply to minimizing environmental risk factors. Exposure to cigarette smoke and avoiding smoking is the number one overall modifiable risk factor for cancer development in the United States.

If someone has been exposed to significant environmental risk factors, appropriate screening is an appropriate course of action. For example, many centers that deal with occupational radiation exposure such as a nuclear power plant have frequent screening clinics for thyroid cancer. Ionizing radiation exposure is a major risk factor for the development of thyroid cancer. Workers in a textile mill that are potentially exposed to small particulate fibers may be best served by getting an annual chest x-ray, being counseled to avoid smoking, and having adequate workplace safety equipment with frequent inspections to ensure that the equipment is adequate.

In addition to screening for cancers based upon environmental risk factors, screening should also be done according to national guidelines. The commonest cancers are normally screened for such as colon, breast and prostate cancer. Early detection and screening reduces the morbidity and mortality of such cancers by catching them at an early stage and thereby facilitating early potentially curative therapy.


  1. www.cancer.gov/cancertopics/causes
  2. Abeloff, M.D. (2008). Abeloff: Abeloff’sClinical Oncology, 4th ed. Chapter 26. Philadelphia, PA: Churchill Livingstone – Elsevier
  3. www.cancer.gov/newscenter/pressreleases/2011/ChernobylRadiation
  4. www.cdc.gov/cancer/colorectal/basic_info/risk_factors.htm
  5. www.cdc.gov/cancer/breast/basic_info/risk_factors.htm
  6. This article was originally published on September 3, 2012 and last revision and update was 9/4/2015.