Pesticides. Plastics. Cosmetics. Deodorants. Cookware. Stain-resistant furniture. Computers.
What do all these seemingly unrelated items have in common?
At one time or another, all have been suspected of increasing the risk of breast cancer.
The important point to recognize is that most researchers agree that there are no solidly proven links between these -- or other similar environmental factors -- and the risk of breast cancer.
The troubling aspect of this, however, is that many believe it's just a matter of time before we connect the scientific dots and see a picture of increased risk.
"It's true that we have no direct links. But what we do have is a compilation of epidemiological studies, cell culture studies, and animal data that are all consistent and I believe are coming together to show us that some of what women are exposed to every day may be increasing their risk of breast cancer," says Janet Gray, PhD, professor and chairman of the department of psychology at Vassar College. Gray, together with experts from the University of Pittsburgh Cancer Institute, recently compiled a report on what we know thus far about the environmental links to breast cancer.
Gray says that while there may be no smoking gun that implicates any one area of concern, or even one chemical, she says the evidence is starting to mount indicating that steady, personal exposure to low levels of lots of different chemicals does matter.
"What's really new in this field," says Gray, is that "finally people are starting to look at interactions -- and the fact that exposure to low doses of lots of different chemicals may yield a result similar to a high-dose exposure to one chemical."
Our Chemical Exposure
And just how many chemicals are we exposed to on regular basis? According to Richard Wiles, senior vice president of the Environmental Working Group (EWG), more than you might imagine.
He reports that an ongoing EWG monitoring project which regularly tests blood, cord blood, urine, and breast milk from 72 adults has so far identified the presence of 455 chemicals that should not be in the body.
"If you had one or two you would say not a big deal. But you can't say that the whole 455 aren't doing something harmful to the body. That just doesn't seem plausible," says Wiles.
Moreover, he reports that a recent EWG survey of some 2,300 Americans found that the average adult is exposed to 126 chemicals every day -- just in their personal care product use alone.
"One in every 13 women is exposed to a known or a probable human carcinogen every day, with one in every 24 women -- or 4.3 million total -- exposed to personal care ingredients that are known or probable reproductive and developmental toxins," says Wiles.
"Is there a direct connection we can make between the use of these products and breast cancer?" asks Julia Smith, MD. "No. But there are strong scientific suspicions that some of the chemicals found in the environment, including those used in cosmetics and other personal care items, might increase the risk, especially if there is heavy exposures before the age of 25." Smith is the director of breast cancer screening and prevention and of the Lynne Cohen Breast Cancer Preventive Care Program at NYU Cancer Institute and Bellevue Medical Center in New York City.
How Breast Cancer Develops
Though the lines between environmental assaults and breast cancer may be somewhat blurred, understanding a bit more about how breast cancer occurs brings at least some of the suspicions into focus.
As Smith explains, breast cancer doesn't happen overnight -- or even as the result of one chemical exposure. It is, in fact, a long and arduous process that begins years before you discover that lump in your breast.
"Problems usually begin when something goes awry in breast tissue on a cellular level many years earlier," says Smith.
Every healthy cell in our body goes through a life cycle that involves growth and division -- a process known as mitosis. That process, says Smith, is controlled by multiple factors. These include a number of genes that tell the cells to grow and those that tell them to stop growing.
If something happens which damages this process, Smith says, cells can begin growing out of control.
"Over time, these cells come together to form a tumor -- the lump you find in your breast," says Smith.
So what does all this have to do with the environment? Many doctors believe that exposure to certain chemicals may damage one or more of the "control" genes, thus putting the cancer process in motion.
"We don't have any clear evidence yet that this is what's happening, but it's one of the possibilities," says Smith.
Though almost any woman has the potential to be affected, experts now believe those at greatest risk are young women -- between puberty and age 25.
Why? These are the years when breast tissue is developing, and, says Smith, is most susceptible to outside influences.
Smith tells WebMD that women won't see the effect right away. But exposures, which occur during these early years, may launch a domino effect of cellular activity that can eventually result in breast cancer.
This is much the same thinking that led researchers to conclude that the cellular damage that occurs as the result of a sunburn before age 17 starts a process that can end up as a deadly melanoma skin cancer decades later.
The Role of Genetics
While every woman has at least the potential to succumb to environmental influences, not every one will. What makes the difference? Our genetics -- the individual blueprint that governs how every cell in our body is supposed to act.
"Inside each cell is all our genetic material -- the total number of genes from both parents," says Smith. The genes that are "expressed," she says, are those that we see -- for example, blue eyes or brown hair.
But what we see is only a small portion of our genetic makeup. Most of what is in our cells is "unexpressed" -- including our risk for certain diseases.
And while there are some clear-cut genetic links to breast cancer that a woman can inherit, this group makes up a relatively small segment of the breast cancer population.
What is likely to affect many more of us, says Smith, is a genetic predisposition -- a gene that is lying dormant in our body that, when awakened by some circumstance, increases the risk for breast cancer.
"Once the gene is aroused, it begins to express itself -- and that expression can cause the kind of cellular changes that eventually lead to cancer," says Smith.
Many believe that it is environmental exposures -- including chemicals -- that can awaken at least some of those dormant genes and put a woman on the cellular path to breast cancer.
Reducing Risks: What Women Can Do
While we can't change our genetics, experts say we can, to some extent, control our environment.
And while you may be thinking this means avoiding carcinogens -- chemicals known to cause cancer -- experts say when it comes to breast cancer, of far greater concern is exposure to what are called "endocrine disrupters." These are chemicals and byproducts that, when inhaled, ingested, or absorbed through the skin, can either mimic the effects of estrogen in the body or cause estrogen to act in a way that isn't normal.
Since it is estrogen that can spark the growth of many tumors, Gray says anything that interferes with estrogen metabolism has the potential to cause harm.
"These chemicals cause a 'triple whammy' -- they increase levels of estrogen, alter cell metabolism, and influence the pathways that increase the risk of cancer," says Gray.
Antiperspirants and Breast Cancer
Based on a recent study in the Journal of Applied Toxicology, cancer researcher Philippa Darbre, PhD, of the University of Reading in England, says the evidence is mounting that the aluminum-based active ingredient in antiperspirants can mimic estrogen in the body.
At the same time, in a report released in 2004, officials with the National Cancer Institute wrote that there was "no conclusive research" linking the use of underarm antiperspirants or deodorants to breast cancer.
And the American Cancer Society (ACS) says that most research on environmental links to breast cancer remains unproven and that research linking deodorant use to breast cancer remains weak.
ACS spokeswoman Elizabeth Ward, PhD, previously told WebMD that there is not much evidence that any environmental exposure has a big impact on breast cancer risk. She points out that studies examining pesticides known to mimic estrogen have failed to show a link between exposure and breast cancer.
"This is a topic that is still under study, and it is important to study it further," she says. "But no strong evidence has emerged of a relationship [between breast cancer risk] and exposure to environmental contaminants."
Smith offers this advice: "You have to accept in life that there is a great deal we don't know -- and just stay as close as possible to a natural state of living. Cut down where and when you can and minimize risks when and where you can in all areas of your life."
To help all women make more intelligent lifestyle, personal care, and environmental choices, Gray and her colleagues at Vassar and the University of Pittsburgh Cancer Institute have created an educational CD that can be requested via their web site (www.erbc.vassar.edu).
Additionally, the Environmental Working Group offers an online database of some 14,000 personal care products rated by their level of chemical contaminants.