September 18, 2023

Carcinogens 101: What You Need to Know About the Cancer-Causing Agents

Carcinogens are lurking everywhere. We’ve got the info on how they might impact you, and what you might be able to do about it.

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Carcinogens. You’re probably aware that they can be dangerous to our health, but most of us lay people probably don’t even know whether they’re animal, vegetable, or mineral. That brings us to the natural next questions: What are these elusive little terrors? Where are they lurking? And most importantly, can we avoid them? In our newest edition of The Exact Science Of, we consulted cancer expert Dr. Tom Beer, chief medical officer of multi-cancer early detection at Exact Sciences. He explains what carcinogens are, how to keep yourself safe from them, and what might help limit your exposure to some of the most common ones.

What is a carcinogen?

If your first thought was “a cancer-causing agent,” you’re right — but the term is pretty broad. According to Dr. Beer, “There’s not one specific substance you can point to that defines carcinogens,” he explains. “It could be a chemical, radiation, or even an infectious agent. What all carcinogens have in common is that if you’re exposed to them, you’re at higher risk of cancer, because they create errors in our DNA which over time may eventually cause cancer.”

Examples of the most common sources of carcinogens

You’re probably already familiar with the carcinogens you’re most likely to encounter on a day-to-day basis: UV radiation from sun exposure, tobacco smoke, and air pollutants from sources like vehicle emissions. But there are other carcinogens you might not recognize, like certain viral or bacterial infections. “To be clear,” says Dr. Beer, “most infections aren’t going to cause cancer. So if you get the flu, that doesn’t mean you’re at a higher risk for cancer.” That said, some infections do increase your risk of cancer. “HPV is the main precipitant of cervical cancer, hepatitis C can predispose a person to liver cancer, and certain bacteria like H. pylori may increase your risk of gastric cancer,” says Dr. Beer. Luckily, these are all carcinogens that routine tests can identify, so add that to your list of reasons to get your annual checkup. 

How harmful are carcinogens?

Unless you’re exposed to a massive amount of carcinogens at once (say, for example, you were working at Chernobyl at the time of the explosion) it takes a very long time for carcinogen exposure to cause cancer. So if you get a bad sunburn, you’re not going to get skin cancer next week. In fact, you might never develop cancer at all. “Many people who are exposed to carcinogens don’t get cancer,” explains Dr. Beer. “Not every smoker gets lung cancer, but [smoking] makes your chances of getting it much higher.” The most important thing to know is that most of these risks are incremental: If you smoked one cigarette at age 18, it won’t have a huge impact on your chances of getting lung cancer. But if you’re a regular smoker, the dose is delivered slowly and adds up over time. That’s part of the reason why most of these cancers occur in older adults.

Why do some people get cancer from carcinogens and not others?

The answer, unfortunately, usually comes down to luck. “A lot of it is individual vulnerability,” says Dr. Beer. “Some of us just have more efficient DNA repair mechanisms than others.” There’s no test you can take that’ll tell you whether or not your DNA is going to be able to repair itself. And more often than not, there’s no genetic link you can look to. “The randomness of it can be a bit frustrating for people,” says Dr. Beer. “Your aunt and uncle might have smoked the same amount, and one got lung cancer and the other one didn’t. It’s just the nature of life.” Similarly, avoiding carcinogens entirely — if that were even possible — doesn’t guarantee that you won’t get cancer, because not all cancer is directly linked to carcinogens.

How come I’m hearing about new carcinogens all the time?

While medicine has advanced significantly over the past 50 or so years, there’s still a lot that doctors don’t know. “The truth of the matter is,” says Dr. Beer, “The world’s moving too fast for us to know everything. All we can do is continue to learn and make adjustments as we figure things out. There was a time when you’d see ads that said ‘Four out of five doctors recommend Camel cigarettes.’ That wasn’t too long ago, but we’ve learned a lot since then. I would anticipate that some things we use today may turn out to be carcinogenic, and some things we’re concerned about today may turn out to be safe.”

How to avoid carcinogens

Apart from avoiding excessive sun exposure and smoking, there are a few lifestyle changes you can make that might help reduce your exposure to carcinogens. For example, alcohol consumption can increase your likelihood of developing cancer, as can obesity: “Obesity is associated with a pro-inflammatory state in the body, which leads to metabolic changes,” says Dr. Beer. “Those changes contribute to the risk of cancer as well as other issues like cardiovascular disease. This elevated risk isn’t enormous, but it’s measurable on a population basis.”

The thing to know is that we’re being exposed to carcinogens all the time, but for most of us, this exposure won’t cause cancer. If you’ve had any unusually high exposure (for example, if you lived near an atomic bomb testing site, were exposed to toxic burn pits while serving on active military duty, or work as a firefighter and regularly encounter excessive smoke and burning chemicals), a genetic syndrome that could predispose you to illness, or any other major medical concerns, talk to your doctor. Other than that, focus on controlling the controllable.


The information provided is not clinical, diagnostic, or treatment advice. You should consult with a qualified healthcare provider about any questions you may have regarding a medical condition or treatment. Never disregard professional medical advice or delay in seeking it because of something you have read in this article.