What environmental factors actually contribute to cancer development and what you can do about it

By Mikkael Sekeres, MD

As much as we all want to avoid consuming or breathing in dangerous chemicals and pollutants, they may be impossible to escape.

Half the world’s population is exposed to increasing amounts of air pollution, mainly due to energy production, industry and transport. Additionally, our contact with environmental radiation has been increasing, from natural sources such as radon in rocks and soil and cosmic radiation, to artificial sources such as industrial and occupational exposures and even medical imaging — which is often necessary, and the benefits of diagnosing an immediate problem far outweigh the remote chance of boosting cancer risk at some point in the future. Forever chemicals, or PFAS, also contaminate the soil, which can in turn affect the food we eat and the water we drink, and have been associated with cancer.

This can all sound pretty scary. But which of these common environmental exposures have actually been shown to increase our risk for developing cancer, and what can we do to lower that risk? Here are the ones I am most concerned about.

Radon
Radon is a radioactive gas given off by rocks, soil and even water. It results from the breakdown of naturally occurring radioactive isotopes in uranium buried deep underground. Studies involving 65,000 coal miners found a linear relationship between cumulative radon exposure and the risk of lung cancer death: The more miners were exposed to radon, the higher their chances of developing and dying from cancer.

These findings suggested that chronic radon exposure in homes could also lead to lung cancer, with the highest potential exposure underground — in basements. Another study, conducted in women living in Iowa for at least 20 years in the same home, comparing those with lung cancer to those without it, confirmed that chronic elevated radon exposure increased the risk for lung cancer. A subsequent investigation conducted in Europe that included over 21,000 people came to the same conclusion.

Because it is a gas, radon concentrates in the lungs as we breathe it in. According to the U.S. Environmental Protection Agency, radon is the second-leading cause of lung cancer (behind smoking cigarettes) and the number one cause of lung cancer among nonsmokers. It is responsible for about 21,000 lung cancer deaths every year, with about 2,900 of those deaths occurring among people who have never smoked. Someone who smokes and is exposed chronically to radon has almost 10 times the risk of developing lung cancer.

The first step to reducing your exposure is to test your home for radon, which you can do by buying a detector online or at a home improvement store. If you find that your home has radon levels beyond the EPA’s recommended threshold, there are strategies to mitigate that risk. The most common method diverts the radon gas from under the basement floor through a pipe to the outside — either through a chimney or through a wall to a vent. The EPA provides resources to find a certified radon professional in your area who is qualified to do this work.

Asbestos
Asbestos is a group of six fibrous minerals that occur naturally in the environment. The material has been used in commercial and industrial applications such as strengthening cement and plastics, insulation, roofing, fireproofing and for sound absorption. In homes, it’s most commonly found in older ceiling and floor tiles or insulation wrapped around pipes and furnaces.

Asbestos has been linked to cancers of the lung, larynx and ovaries, and possibly other cancers. Most importantly, chronic asbestos exposure unequivocally leads to mesothelioma, a cancer that affects the lining of the lungs and abdomen — presumably because when asbestos fibers are inhaled or ingested, they get trapped in the lungs or intestinal tissues, causing scarring and long-term inflammation. Smoking increases the risk of cancer manyfold.

The EPA finally banned asbestos in 2024. Many industries phased it out in the late ’70s and ’80s, but it’s often found lingering in older homes and other buildings.
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When I was buying a house in Shaker Heights, Ohio, more than 15 years ago, a home inspector peered into the crawl space and discovered discarded asbestos wrapping from the basement’s hot water pipes. I asked the owners to properly dispose of it before the closing.

I love a good do-it-yourself project around the house, but I didn’t go anywhere near the asbestos in my former home. Potential asbestos exposure should be taken seriously, and its disposal handled by professionals who are specially trained to do it safely. Again, the EPA offers a list of resources by state.

Microplastics
Microplastics are fragments of plastic between 1 nanometer and 5 millimeters wide. One nanometer is narrower than a human hair, and 5 millimeters is about the width of a wedding ring. Some microplastics start out small — like microbeads added to face washes — while most come from the disintegration of larger plastics, such as plastic wraps, water bottles, takeaway containers, tires and paint. Our exposure is lifelong: Microplastics have even been detected in human placentas and in meconium (poop) from newborns.

Theoretically, microplastics may contribute to an increase in cancer rates in a couple of ways. First, the plastics may carry on their surface toxic chemicals, such as polycyclic aromatic hydrocarbons (PAHs), that can cause cancer by damaging a cell’s DNA. They could also carry forever chemicals, which do not break down over time and have been associated with kidney cancer, postmenopausal breast cancer and testicular cancer. Or, the plastics could cause a break in the protective colon lining, allowing cells to be more exposed to toxins, or become embedded in the wall lining of our colons, like asbestos, and cause chronic inflammation followed by cancer.

But the data is all indirect: To date, no study has conclusively tied microplastics to colon cancer, or to any cancer. However, given what we know about how microplastics can cause damage in the body, the increase in early onset colorectal cancer in the U.S. and the similarities in timing between the increase in cancer rates and the rapid increase in microplastics in the environment, many experts suspect that microplastics are a risk.

I try to minimize my exposure to microplastics by reviewing the contents of personal care products before using them, to avoid microbeads. I also use glass containers to store food and metal or glass water bottles to reduce my exposure to plastics, and consume food that is not heavily packaged.

Air pollution
Exposure to outdoor air pollution is considered a serious public health problem because, of course, it’s not something we can easily control on an individual level.

The International Agency for Research in Cancer classifies outdoor pollution in general, and particulate matter specifically, as carcinogenic to humans. An analysis of 18 studies involving more than 4 million people found that the risk of lung cancer was 8 to 9 percent higher for people chronically exposed to higher concentrations of particulate matter, such as in high traffic or urban areas. Worldwide, it is estimated that air pollution contributes to 14 percent of lung cancer deaths. Higher particulate matter exposure may also be associated with developing bladder, breast, kidney and colorectal cancers, though there’s less evidence supporting these associations than for lung cancer.

Interventions to reduce the amount of air pollution, including reductions in biomass burning, and improvements in cooking stoves and indoor ventilation, are expected to help lower cancer resulting from air pollution worldwide. In the meantime, there are a few things you can do. Personal respirators (face masks) have been shown to reduce particulate matter exposure, as have air purifiers, which you can buy and use in your home to improve the air quality.

At the end of the day, there are plenty of things in the world around us that can contribute to cancer risk. While we may not be able to avoid them completely, there’s plenty we can do to minimize our exposure, in addition to adopting lifestyle practices that are more within our control — like exercising regularly, eating a healthy diet, and taking sun protection seriously — that can further mitigate our overall cancer risk.
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Mikkael A. Sekeres, MD, MS, is the chief of the division of hematology and professor of medicine at the Sylvester Comprehensive Cancer Center, University of Miami. He is author of the books “When Blood Breaks Down: Life Lessons from Leukemia” and “Drugs and the FDA: Safety, Efficacy, and the Public’s Trust.”

Credit: Washington Post