Common Carcinogens and Cancer Risk

Carcinogens are substances or agents that can cause cancer. These can occur in nature, such as with ultraviolet radiation and some viruses, or be manmade, as seen in car fumes and cigarette smoke.

While it's impossible to eliminate all carcinogen exposure, you can take steps to reduce what you come in contact with.

A process of an asbestos removal
SamBurt / Getty Images

How Carcinogens Cause Cancer

Carcinogens cause cancer by affecting the genetic information, or DNA, in cells.

A carcinogen can directly damage DNA and cause changes called mutations. Other times a carcinogen may cause cells to divide more rapidly than normal, which increases the chances of DNA becoming altered and raises the risk of developing cancer.

Exposure to Carcinogens and Increased Cancer Risk

Carcinogens have the potential to cause cancer, but being exposed to these substances does not definitely mean you will get cancer.

Your risk of cancer increases based on several factors:

  • Length of exposure: The amount times you are exposed and for how long each time plays a role in your risk. But it also depends on your individual health and other personal factors that either raise or lower your risk of cancer.
  • Amount of exposure: Some carcinogens are related to the intake of substances such as acetaldehyde and ethanol in alcoholic beverages. The more you consume these carcinogens, the more likely you are to develop cancer.
  • Genetic disposition: Your inherited genes, or genome, may put you at risk for certain conditions when exposed to specific carcinogens.

How Long Before Carcinogens Cause Cancer?

The latency period, the time between exposure to a carcinogen and clinical onset of cancer, depends on the type of carcinogen and your risk factors, but often it takes a long time, sometimes decades, before cancer is detected.

It's also important to note that cancer is most often caused by an accumulation of mutations, rather than a single incident. This means a number of issues, not just carcinogens, may work together to increase or decrease the risk of developing cancer.

Even when damage to DNA occurs, your body can produce proteins that either repair damaged DNA or eliminate damaged cells before a normal cell is transformed into a cancer cell. Tumor suppressor genes also slow down cell division and do repairs.

Types of Carcinogens

Carcinogens exist in a range of indoor or outdoor environments. They include chemicals, viruses, medications, and pollutants.

Some carcinogens are linked to specific types of cancer.

How Carcinogens Are Classified

The International Agency for Research on Cancer (IARC), which is part of the World Health Organization (WHO) has evaluated more than 1,000 possible carcinogens. These are divided into the following groups:

  • Group 1: Carcinogenic to humans (only about 120 substances are confirmed to be in this group)
  • Group 2A: Probably carcinogenic to humans
  • Group 2B: Possibly carcinogenic to humans
  • Group 3: Not classifiable as to its carcinogenicity in humans

Home and Workplace Chemicals

Many chemicals used in building materials or products in the home or workplace may be carcinogenic. Two common ones are formaldehyde and asbestos.

  • Formaldehyde: This carcinogen in building materials, furniture, and household products emits chemicals in a process known as "off-gassing." Formaldehyde is also a byproduct of cigarettes and smoking. Reduce formaldehyde exposure by purchasing composite wood products certified to reduce emissions, using an air conditioner and dehumidifier in humid areas, and improving ventilation.
  • Asbestos: Old pipe insulation, attic insulation, textured ceilings, or floor tiles contain this carcinogen. If the material is disturbed, tiny asbestos fibers may be released into the air. Asbestos can lead to a specific type of lung cancer called mesothelioma. Professional contractors or agencies can remove asbestos if needed.

Environmental Radiation

Ultraviolet (UV) radiation from the sun is a well-known cause of skin cancer. You can protect your skin by wearing hats and protective clothing when outdoors. Also use an SPF 30 broad-spectrum sunscreen, which protects you from both UVA and UVB rays, the two types of UV light linked to skin cancer.

Another common form of environmental radiation is radon, which is emitted from the normal decay of uranium in the soil and then gets trapped in homes. Radon is the second leading cause of lung cancer after smoking.

You can have your home tested for radon and install a radon mitigation system if levels are high.

Medical Radiation

Radiation exposure that occurs during certain diagnostic tests, such as computed tomography (CT scan), and radiation therapy used to treat cancer is carcinogenic.

For example, women who receive radiation therapy after a mastectomy, a procedure to remove a breast due to breast cancer, are at an increased risk of developing lung cancer due to the radiation that is delivered to the chest area.

However, the risks of not getting such imaging or treatment when needed are often considered greater than those associated with medical radiation.

Viruses

There are several viruses linked to cancer. These affect healthy cells’ genetic makeup and can make it more likely that they will turn into cancer.

Viruses that can lead to cancer include:

There are HPV vaccines and hepatitis B vaccines that can reduce your risk of getting these viruses and the cancers linked to them. They are only effective if vaccination occurs prior to being exposed to the virus.

Medications

Some chemotherapy and hormonal therapy drugs can raise the risk of cancer.

For example, chemotherapy drugs such as Ellence (epirubicin), used for early-stage breast cancer, can sometimes lead to leukemia when administered in high doses.

Oral contraceptives may increase the risk of breast cancer or cervical cancer, but they may lower the risk of endometrial, ovarian, and colorectal cancers.

Pollution

Both outdoor and indoor air may contain pollutants that are carcinogenic.

Common outdoor air pollutants from industrial or power plants, engine exhaust, and fire smoke are strongly linked with lung cancer.

Indoor air pollutants can come from a variety of sources such as building materials, fire retardants, paint fumes, cleaning products, and dust. Indoor air pollutants can also lead to the development of lung cancer.

Lifestyle Factors

There are a variety of lifestyle factors that can contribute to mutations that result in cancer.

Lifestyle-related carcinogens include:

  • Smoking or exposure to secondhand smoke
  • Alcohol use
  • Obesity
  • Poor diet (e.g., eating too much processed meat and not much produce)
  • Lack of physical activity

There is also some evidence that cooking meat at high temperatures—grilling or pan frying it, for example—may create carcinogenic compounds that can then be consumed.

Cooking meats for longer times at lower temperatures and removing any charred portions before eating may help reduce your risk.

How to Reduce Exposure to Carcinogens

Because not every substance that may be a carcinogen has been tested, it's important to practice discretion with any potential carcinogens you may be exposed to.

These tips can help you get a sense of what those might be and what to do if you encounter them:

  • Read labels and research ingredients if you are not familiar with them. The American Cancer Society's website has a quick-reference list, and the International Agency for Research on Cancer (IARC) Monographs and National Toxicology Program databases are good resources for doing more digging. Some home products, like certain brass cleaners, even make a note that they contain human carcinogens on their packaging.
  • Follow directions for safe handling of chemicals at home. Read the small print on containers. Some labels recommend wearing gloves. Others suggest good ventilation, wearing a face covering, or even putting on a special ventilation mask.
  • Consider using gloves to handle it. Many substances can be absorbed easily through the skin.
  • Follow recommended procedures at work when handling chemicals on the job. Employers are required to provide Material Safety Data Sheets on any chemicals you will be exposed to at work. Take the time to read these carefully.
  • Consider alternatives to substances with long lists of ingredients. For example, instead of having an abundance of commercial cleaning supplies, you can effectively clean your home using only vinegar, lemon juice, olive oil, and baking soda.

Summary

Carcinogens cause cancer by damaging your cell's DNA or by causing damage and inflammation that leads to mutations. Exposure to a carcinogen does not necessarily mean you will definitely go on to have cancer, but it is a factor that should not be ignored.

Exposure can come from home chemicals, environmental or medical radiation, medications, viruses, polluted air, and lifestyle choices. They are a part of daily life, so you really can't avoid them entirely. But you can take steps to protect yourself, such as wearing gloves, reading labels, and not smoking.

19 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American Cancer Society. Carcinogens and the cancer connection.

  2. National Cancer Institute. Environmental carcinogens and cancer risk.

  3. American Cancer Society. Known and Probable Human Carcinogens.

  4. Carpenter DO, Bushkin-Bedient S. Exposure to chemicals and radiation during childhood and risk for cancer later in lifeJ Adolesc Health. 2013;52(5 Suppl):S21-S29. doi:10.1016/j.jadohealth.2013.01.027

  5. Jackson M, Marks L, May GHW, Wilson JB. The genetic basis of diseaseEssays Biochem. 2018;62(5):643-723. doi:10.1042/EBC20170053

  6. National Institutes of Health: National Human Genome Research Institute. Tumor suppressor gene.

  7. International Agency for Research on Cancer. Preamble to the IARC monographs on the identification of carcinogenic hazards to humans.

  8. Environmental Protection Agency. Facts about formaldehyde.

  9. Environmental Protection Agency. Protect against exposures to formaldehyde.

  10. Skin Cancer Foundation. UV radiation & your skin.

  11. American Cancer Society. Radon and Cancer.

  12. American Cancer Society. Understanding radiation risk from medical tests.

  13. American Cancer Society. Viruses that Can Lead to Cancer.

  14. MedlinePlus. Epirubicin.

  15. American Cancer Society. Determining if something is a carcinogen.

  16. Turner MC, Andersen ZJ, Baccarelli A, et al. Outdoor air pollution and cancer: An overview of the current evidence and public health recommendationsCA A Cancer J Clin. 2020;70(6):460-479. doi:10.3322/caac.21632

  17. American Lung Association. Indoor air pollutants and health.

  18. National Cancer Institute. Cancer prevention overview (PDQ)-patient version.

  19. National Cancer Institute. Chemicals in meat cooked at high temperatures and cancer risk.

By Lynne Eldridge, MD
 Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."