With which carcinogens should we concern ourselves?

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Cancer is one of our top health concerns – it’s the top killer after heart disease, and a family history of cancer can make even the healthiest people anxious. Healthy New Albany spoke with Dr. Susan Olivo-Marston from The Ohio State University Wexner Medical Center on carcinogens and the role they play in our lives.

Healthy New Albany: Can you explain what a carcinogen is?

Dr. Susan Olivo-Marston: A carcinogen is anything that can cause cancer. It can be a specific exposure, such as tobacco or ultraviolet light, or it can be a specific element, such as asbestos or radon. A carcinogen doesn’t necessarily cause cancer in every person to which it is exposed.

HNA: We hear that everything from microwaves to plastic water bottles causes cancer. Is this just fearmongering, or is there any truth behind these more outlandish statements?

SO-M: It is extremely challenging to determine if something is a carcinogen. Sometimes, we have research in humans to justify that something is a carcinogen, but often, the research may be in lab animals, which are obviously quite different from people. The most widely recognized system for identifying carcinogens is the International Agency for Research on Cancer (IARC), which classifies carcinogens (based on research in animals and humans) into one of five groups: 1) Carcinogenic to humans; 2A) Probably carcinogenic to humans; 2B) Possibly carcinogenic to humans; 3) Unclassifiable as to carcinogenicity in humans; and 4) Probably not carcinogenic to humans.

I believe the above statement is just out of lack of knowledge and fear. Currently, there is no evidence that I am aware of that microwave ovens, when used according to the directions, pose a cancer risk to humans. With regard to plastic water bottles, again, I’m not aware of data in humans suggesting they can increase risk of cancer. The materials that make up plastic water bottles are classified by IARC in group three, which is “unclassifiable as to carcinogenicity in humans.”

HNA: What are some common household carcinogens we should all be aware? What’s the best way to address them?

SO-M: In a common central Ohio home, there may not be a lot of common household carcinogens with the exception of alcohol, tobacco (including exposure to secondhand smoke and smokeless tobacco) and processed meat. These are things that it is pretty easy to limit exposure.

HNA: What are some common workplace carcinogens we should all be aware? What’s the best way to address them?

SO-M: Common workplace carcinogens really depend on the occupation. Specific substances that are listed in IARC’s list as “carcinogenic to humans” that people may be exposed to at work include things such as diesel engine exhaust, formaldehyde, outdoor air pollution, rubber manufacturing industry, soot and UV radiation. The National Institute for Occupational Safety and Health, part of the Centers for Disease Control and Prevention along with Occupational Safety and Health Administration – part of the Department of Labor – exist to make sure work environments are safe for employees.

HNA: We all know there are lifestyle factors such as smoking that can cause cancer. But what other lifestyle decisions can impact our health when it comes to cancer?

SO-M: Other lifestyle factors that can increase risk of cancer include diet, such as processed meat consumption and alcohol. In addition, obesity is known to increase risk of several types of cancer including postmenopausal breast cancer, colorectal cancer and endometrial cancer, so maintaining a healthy weight is really important. Physical activity may decrease risk of cancer, so an active lifestyle is also important.

HNA: How do researchers determine if something is carcinogenic?

SO-M: It is a combination of lab data from animal studies and research in humans. Researchers use epidemiologic studies – which just means studies in large populations of people – to assess whether specific exposures increase cancer risk. Data is looked at from many studies over long periods of time to determine if something is carcinogenic. IARC, which is part of the World Health Organization, has been determining whether exposures are potentially carcinogenic for 30 years and has looked at more than 900 exposures. Only a little more than 100 of these were determined to be “carcinogenic to humans.”

HNA: What does some of the latest research in this area tell us about carcinogens?

SO-M: At the beginning of November, seven new substances were added to the National Institutes of Health Annual Report on Carcinogens. Five of them were viruses, one was a chemical and one was a metal. Cobalt has been added as “reasonably anticipated to be carcinogenic,” which means although there is some research in animals that suggest it can cause cancer, there isn’t enough research in humans to support this. Trichloroethylene was also added although exposure is unlikely in the general population. Certain occupations – it is used as a metal degreasing agent – may have a higher risk of exposure, but it is believed that exposure in the general population is actually decreasing.

The five viruses added to the list include HIV and Epstein-Barr (EBV). There are approximately 1.2 million people in the U.S. who are infected with HIV and EBV is one of the most common human viruses. While infection with some of the other listed viruses is common in the U.S., most infected people remain healthy and symptom-free. Cancer risk increases in people that are infected with these viruses if they also have a weakened immune system.

HNA: Which carcinogens affect DNA directly?

SO-M: Many carcinogens affect DNA directly, such as UV and ionizing radiation. It would really be impossible for me to list all the carcinogens that directly affect DNA and, although there is research to support that certain exposures increase cancer risk, there is still a lot of research being done to really understand how many of these exposures work biologically to increase cancer risk.

Hannah Bealer is an editor. Feedback welcome at hbealer@cityscenecolumbus.com.

About the Expert

Dr. Susan Olivo-Marston is currently an assistant professor in the Division of Epidemiology in the College of Public Health at The Ohio State University. Previously, she was a postdoctoral fellow in the National Cancer Institute’s Cancer Prevention Fellowship Program during which time she earned a Master’s of Public Health concentrating in Epidemiology and Biostatistics at the Johns Hopkins Bloomberg School of Public Health in 2005. Olivo-Marston also earned a Ph.D. in Tumor Biology from Georgetown University in 2004 and a master’s of science in cancer biology from the University of Texas MD Anderson Cancer Center in 2001. 

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