Author: 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
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).
“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
“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
- 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
- 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
- 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-thansolid
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
What about chemicals?
“It’s a fuzzy area when you start talking
about environmental pollutants and
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 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
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
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
“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
Avoiding exposure to environmental risk actors
There are plenty of steps you can take to limit your exposure
to environmental risk factors.
- Avoid tobacco. The best advice is to abstain from all
tobacco products, including cigarettes. If you live with
a smoker, have him or her smoke outside; install an
air filtration system in the home and wash clothes
frequently, especially before holding a baby because
clothing can carry the toxic compounds.
- Maintain a healthy body weight and get three to four
hours of moderate physical activity per week.
- Minimize alcohol intake, which for most adults means
no more than one or two alcoholic beverages per day
(and preferably less).
- Cook meats at low temperatures to avoid charring.
- Minimize your intake of meat and other animal
products and increase your intake of whole grains and
fresh fruits and vegetables.
- Comply with cancer screening guidelines and
- Avoid electromagnetic fields (EMFs). In the home two
of the biggest sources of EMFs are hairdryers and electric
- Clean house. Remove shoes before entering the house
and dust, vacuum, and mop frequently to cut down on
chemicals that can accumulate in dust.
- Use natural or homemade cleaning products. Most
cleaning products are loaded with chemicals, and
manufacturers are not required to disclose ingredients
on the label. Read labels carefully and buy products that
disclose their ingredients.
- Get a radon detector. If you have particularly high levels
of radon in your home, you may want to seek the services
of a radon specialist. You may benefit from sealing
off your basement and installing a radon remediation
system. Sometimes these things are even covered by
- Avoid BPA. BPA is found in plastic, canned foods, and
even on receipts.