Environmental risk factors

By Laurie Wertich

What causes cancer? It’s the million-dollar question—and if you pay attention to the messages in the media, the answer is: everything. But that isn’t really the case. There are indeed some environmental risk factors for cancer—meaning exposure to substances that could increase the risk of developing cancer—but there are also a lot of unproven claims about factors that increase the risk of cancer. The trick is learning to discern fact from fiction. The best way to protect ourselves from cancer: information and lifestyle modification.

What is an environmental risk factor?

Environmental risk factors for cancer are things in your environment that may increase the risk of developing cancer. Carcinogens are materials that are known to cause cancer. When a substance is referred to as a “known cancer risk factor” or a “known carcinogen,” it means that science has proven that exposure to that substance can increase the risk of cancer.

The term environmental risk factor usually brings to mind things like chemicals and radiation, and these things are indeed risk factors; however, there are many other factors that fall within that category, as well. In fact, the greatest risk factors we face in the United States are not exposures to radiation or chemicals in the environment around us but, rather, our own dietary and lifestyle choices—most of which can be modified.

“From a public health point of view, environmental risk factors are not just things that you are exposed to in the environment around you or the things you eat, drink, or put on your skin. They are the sum total of those factors, plus other behavioral and lifestyle factors that expose your body to carcinogens and affect how your body responds to those carcinogens,” explains Robert Wascher, MD, FACS, surgical oncologist at Cancer Treatment Centers of America® (CTCA) in Goodyear, Arizona, and author of A Cancer Prevention Guide for the Human Race (Dog Ear Publishing, 2010; $14.99).

Lifestyle factors

“When you take that broader view, tobacco in all of its forms is still the greatest environmental risk factor for cancer, whether you use it yourself or are exposed to it by others,” Dr. Wascher notes. “At least one-third of all cancer deaths are directly or indirectly related to tobacco exposure.”

The next biggest category, which also accounts for one-third of cancer deaths, is a group of lifestyle factors lumped together: obesity, alcohol intake, physical inactivity, and dietary exposure to food-related carcinogens. In other words, when you look at these two main categories of cancer risk factors, 60 percent of cancer diagnoses could be avoided through modification of these lifestyle factors.

These environmental factors are modifiable, but what about the other 40 percent? Are there other cancer risk factors that we might be able to avoid? Maybe—and some of them are more modifiable than others.

Identifying risk factors

“There are a number of compounds in the air, water supply, and food supply that carry potential risk,” explains Dr. Wascher. “Some of these environmental factors are still not well understood. However, occupational exposure to known carcinogens probably accounts for two to five percent of cancer cases and cancer-associated deaths, but it’s hard to accurately measure environmental exposure to carcinogens outside of certain work environments.”

There’s the catch: how do we measure exposure and assess risk when we aren’t sure what we’re even measuring? In the scientific community, randomized controlled clinical trials are the gold standard—meaning that one group is given some sort of intervention (like exposure to a type of medication) and another is not, and then the two groups are compared. But environmental exposure to potential carcinogens does not happen in a controlled environment like that.

“With regard to a lot of environmental exposures, we don’t have a natural control group because often everyone is exposed to them,” explains Connie Engel, science and education manager for the Breast Cancer Fund, a national nonprofit organization dedicated to preventing breast cancer by eliminating exposure to toxic chemicals and radiation linked to the disease. “We can’t control who is exposed, and we certainly can’t do a randomized study and randomly assign people to things that we think are hurting them.”

What’s more, individuals respond differently to carcinogens. “In any discussion about environmental carcinogens and environmental cancer risk, you have to say something about the fact that not all of us are going to respond in the same way,” explains Dr. Wascher. “There appears to be an underlying genetic component involved in our individual risk of actually developing cancer in response to being exposed to many known carcinogens. We’re all different, and we all have a different genetic makeup.”

Confirmed environmental risk factors

Scientists like data. Data provide greater certainty, and with greater certainty we can make better recommendations. Identifying true carcinogens is potentially complicated, but there are some environmental factors that are beyond debate.

• Tobacco: Tobacco use, particularly cigarette smoking, has been linked to almost every type of cancer, especially lung cancer. “Tobacco is by far the greatest cause of cancer cases and death,” Dr. Wascher says. According to Shelly Smekens, ND, naturopathic resident at CTCA® in Zion, Illinois, the risk is high for both smokers and nonsmokers exposed to secondhand smoke.

• Radon: Radon is a colorless, odorless gas that develops as a result of uranium decay. It is present in some level almost everywhere in the world, but some places have higher levels of radon, particularly areas with cold winters and in buildings with basements where the gas can accumulate. “After cigarette smoking, radon is the second-highest modifiable risk factor for lung cancer, which is still the number one cause of cancer death in the United States,” explains Smekens. Dr. Wascher notes, “Radon gas exposure probably accounts for five to eight percent of all lung cancer cases.”

• Air pollution: “Particulate air pollution, especially exhaust from diesel engines, has been linked to lung cancer,” Dr. Wascher says. “Individuals who live in heavily polluted areas therefore appear to have higher rates of lung cancer.”

• Charred food: Heterocyclic amines, or HCAs, are carcinogenic chemical compounds created by cooking meat at a high temperature. Grilled and heavily charred meats have been linked to colorectal, pancreatic, stomach, and breast cancers.

• Dietary choices: “Diets rich in red meat and other animal products are also associated with an increased cancer risk,” says Dr. Wascher, “and particularly cancer of the esophagus, stomach, pancreas, colon, and rectum. Diets that are low in whole grains and fresh fruits and vegetables also increase the risk of these same cancers.”

• Radiation: Exposure to radiation can increase the risk of cancer. “For most of us, that is probably not a huge deal because we didn’t live downwind of Chernobyl,” explains Dr. Wascher. “But an area of increasing concern is medical Xray exposure. In fact, recent conservative estimates suggest that one to two percent of all new cancer cases may be linked to medical X-rays and to CT [computed tomography] scans in particular.” Many of these scans are important and necessary to medical treatment, but sometimes Xrays and scans are overused. “When properly used, CT scans are very important in the management of cancer, but many of these scans are being done for less-than solid critical reasons,” Dr. Wascher says. He recommends prudent use of these scans—and the use of ultrasound or magnetic resonance imaging when possible and appropriate, instead of CT scans.

• Power lines: Smekens explains that electromagnetic fields (EMFs) have been associated with leukemia, brain tumors, and breast cancer. “There have been some occupational studies on people who worked on power lines that showed small but real increases in leukemia and brain cancer,” she says. An association has also been found between housing proximity to power lines and increased incidence of childhood leukemia.

What about chemicals?

“It’s a fuzzy area when you start talking chemicals because there are a lot of variables,” Dr. Wascher says.

The challenge comes in proving beyond a shadow of a doubt that certain chemicals pose a risk. The scientific community needs solid facts to rule against a chemical, but the available scientific data is often not black-and-white. Engel says that if you look at the full body of data— which includes both human and animal studies—there is biologically plausible concern regarding certain chemicals. She lists several chemicals of concern, including endocrine disruptors like phthalates and bisphenol A (BPA).

“You don’t have that much to lose by avoiding these chemicals, and you have everything to gain,” Engel insists.

Lindsay Dahl, deputy director of Safer Chemicals, Healthy Families, a national coalition of organizations and individuals working to raise awareness about toxic about environmental pollutants and chemicals in homes, workplaces, and products, says that peer-reviewed science has shown some strong links between cancer and some chemicals. “Two of the best examples are formaldehyde and trichloroethylene (TCE),” she says. Formaldehyde is a known human carcinogen and a common indoor air pollutant. It can be found in building materials, furniture, cabinets, countertops, cleaners, and more. TCE is used in rug cleaners, adhesives, paint removers, and spot removers. It is highly toxic and can contaminate the water supply. There have been reported cancer clusters next to manufacturing facilities that use these chemicals.

Engel says that even low doses of some compounds can be cause for concern, especially when the exposure happens at vulnerable periods of development such as during infancy, before and during puberty, and during pregnancy and lactation. “We think of this as a public health issue,” she says. “And we think it is important to give people tools to make informed decisions.”

But how do you make informed decisions about chemicals when there is so much conflicting data?

“There are so many things to worry about that you could drive yourself nuts,” admits Dahl, but she is quick to point out that the news is not all bad. “Prevention is hard to quantify, but we know that it works. For example, lead levels in the blood plummeted within ten years of when they removed lead from gasoline.”

Prevention is key

There are a variety of environmental risk factors linked to cancer, but there is no need to live in fear. It’s impossible to avoid all exposure to potential carcinogens, but it pays to know what is in your environment and to do your best to protect yourself against potential risk factors.

“Even if you’re conservative and throw out the wacky stuff and accept the known limitations of the science and the data,” says Dr. Wascher, “at least 60 percent of all new cancer cases are tied to one or more modifiable lifestyle or other environmental risk factors, and many of the types of cancers that are linked to preventable risk factors are, in fact, the cancers that cause the greatest number of cancer-related deaths.”



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