The Top 6 Carcinogens in America

Cancer is an unfortunate fact of life for many: It affects nearly 1.66 million people in America annually, and this number does not include those diagnosed with many skin cancers. While doctors have determined that certain cancers often have a genetic basis, others are due to environmental factors. While it may not be completely possible to prevent cancer, you can take steps to avoid exposure to proven carcinogens (cancer-causing agents). Below are the major carcinogens known in the U.S.— some of which may surprise you:

1. Tobacco

No shocker here—smoking cigarettes is the single biggest risk factor for cancer worldwide, accounting for 30 percent of all cancer deaths in this country alone. Why? Of the 7,000 chemicals in tobacco, at least 70 are known carcinogens, including polycyclic aromatic hydrocarbons, nitrosamines, benzene, and formaldehyde. It’s estimated that 87% of lung cancer cases in men and 70% in women are due to smoking, but smoking is also a culprit in head, neck, esophageal, bladder, and other cancers.

What you can do: Quit smoking and avoid being near people who are smoking.

2. Alcohol

Alcohol doesn’t just affect your liver and quality of life, according to researchers: "Alcohol consumption is associated with a variety of different cancers," says David Eastmond, PhD, professor, and chair of the Department of Cell Biology & Neuroscience and a research toxicologist at the University of California, Riverside. Among the notable alcohol-related cancers are head and neck cancers (such as cancers of the oral cavity and voice box), as well as esophageal, liver, breast, and colorectal (colon and rectal) cancers. Even modest alcohol consumption (defined by the government as one drink per day for women and two for men) can raise the risk. A recent study in the American Journal of Public Health estimated that about 3.5 percent (19,500) of all U.S. cancer deaths are alcohol-related.

The reasons for this are varied. One major cause is that the body breaks down ethanol, which is found in alcohol, into the carcinogenic chemical acetaldehyde. "Some people don’t eliminate acetaldehyde easily and are at a much higher risk of esophageal cancer," Eastmond says, adding that this is usually a genetic problem that’s more common in certain ethnic groups, including Asians.

What you can do: Cut down on the amount of alcohol you drink. Aim for no more than a few drinks per week at the most.

3. Sunlight

That’s right—that mood-lifting sunshine you love can be a killer. The sun emits various types of ultraviolet (UV) rays, which damage skin cells’ DNA and can ultimately lead to cancer. (Tanning beds also produce risky and damaging UV rays.) More than 3.5 million cases of basal and squamous cell skin cancer are diagnosed each year, in addition to 73,000 cases of potentially deadly melanoma. Skin cancer may not show up until after decades of sunbathing, but doctors say they are seeing more young adults with skin cancer than ever before.

What you can do: Stay out of the sun during the hottest part of the day—between 10 AM and 4 PM. If you must venture out, wear light, long-sleeved garments and a wide-brimmed hat. Reapply a broad-spectrum (UVA- and UVB-screening) sunscreen at least every two hours, and get full-body skin exams from a dermatologist regularly.

4. Infectious Agents

Responsible for about 10 percent of all cancers in the U.S., infectious agents include the sexually transmitted human papilloma virus (HPV), hepatitis B (also transmitted sexually as well as through contact with blood and other bodily fluids), and Helicobacter pylori (spread via infected food or utensils and also by direct mouth-to-mouth contact).

What you can do: Use condoms if you’re sexually active, and practice good hygiene.

5. Environmental/Product Chemicals

Modern life exposes us to a variety of chemical substances that may cause healthy cells to mutate into cancerous ones. For instance, benzene is found in tobacco smoke and gasoline; soot and particulates from diesel fuel are often present in the air wherever there are trucks, buses, and other large vehicles, and formaldehyde is released from manufactured wood products and cigarette smoke; it’s also formed by the breakdown of substances found in about one in five cosmetic products.

What you can do: Buy cosmetics from companies that have a safe rating from the Environmental Working Group ( Question manufacturers before buying furniture or other items that may contain toxic chemicals, and avoid polluted locations.

6. Ionizing Radiation

People who get a lot of medical tests such as x-rays and CT (computer tomography) scans are exposed to significant levels of ionizing radiation. However, while there is no safe level of radiation exposure, experts feel that the benefits of medical testing outweigh the potential risks. And there has been great improvement in diagnostic equipment over the past few years in order to lower patients’ radiation exposure.

What you can do: Keep careful records of your medical-imaging tests to avoid any unnecessary ones, particularly elective whole-body CT scans for individuals without symptoms. Ask your provider if a scan is really necessary. Make sure your doctors use only newer digital x-ray and CT scan machines, as they deliver less radiation than older equipment.

David Eastmond, PhD, reviewed this article.


Eastmond, David, PhD. Phone conversation with source. June 9, 2015.

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"Known and Probable Human Carcinogens." American Cancer Society. Page last revised March 26, 2015.

"Alcohol and Cancer Risk." National Cancer Institute. Page last reviewed June 24, 2013.

Nelson D.E., D.W. Jarman, J. Rehm, et al. "Alcohol-Attributable Cancer Deaths and Years of Potential Life Lost in the United States." American Journal of Public Health (2013): 103, 4: 641-648.

"Sun and UV Exposure." American Cancer Society. Accessed on June 12, 2015.

"What Can I Do to Reduce my Risk of Skin Cancer?" Centers for Disease Control and Prevention. Page last updated May 29, 2014.

"Chemicals in Tobacco Smoke." Centers for Disease Control and Prevention. Page last updated March 21, 2011.

"Known and Probable Human Carcinogens." American Cancer Society. Page last revised March 26, 2015.