August 2005: Environmental Issues and Breast Cancer

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Greater risk from toxins by air or water?

Question from JLebel: Is there a greater likelihood of breast cancer occurrence if exposure to a toxin is airborne vs. in a water supply or in contaminated land?

Answer —Devra Davis, Ph.D., M.P.H.: There's no reason to think there's any difference. What is important is whether the agent in fact affects the body's production of hormones or affects our genes.

Do fuel emissions increase risk?

Question from MEA: I read where burning fossil fuel elevates one's risk for breast cancer. I live under a flight path to a military base (VA Beach, VA) and am the third unrelated person to live on this property to develop breast cancer. I was only 42 when I was diagnosed. Any thoughts on this?

Answers —Devra Davis, Ph.D., M.P.H.: The National Academy of Sciences has evaluated the toxicity of jet fuel. Using animal evidence, they concluded there are a number of compounds found in jet fuel that increase the number of mammary tumors found in animals. We simply do not have any studies of humans. Reasonable people can disagree on this, but it's my opinion that the animal evidence is very worrisome.

In addition, there have been a couple of recent epidemiological studies finding increased risk of childhood cancers in children in England who live near heavy traffic areas. We know that some of the emissions associated with traffic have been found also to increase mammary tumors in animals. So the unfortunate answer is that the development of tumors could be associated with this exposure but we can't come to firm conclusions.

Sue Heffelfinger, M.D., Ph.D.: In addition to mammary tumors, there is evidence that immune function and asthma are also indirectly related to exposure in childhood. The real sensitive age, especially for breast cancer, can occur during maximum time of breast development, i.e. childhood and puberty. So exposure at that age is particularly worrisome.

Can mammogram radiation increase risk?

Question from KVY: Could the X-rays women are exposed to and the compression during mammograms be an environmental element that could contribute to women getting breast cancer?

Answers —Devra Davis, Ph.D., M.P.H.: It depends on the age of the person getting the mammogram and the amount of exposure involved. Unfortunately, younger women are at a higher risk from radiation than are older women. We know this because of the data developed from Hiroshima where young girls and women under the age of 20 who were exposed to radiation had a much higher risk of breast cancer when they reached middle age. But women who were already middle-aged when exposed to the radiation at Hiroshima did not show this increased risk. So diagnostic radiation from mammography in women under 40 or possibly in women before menopause in general may well carry an increased risk of cancer associated with radiation alone. We certainly know that radiation of a pregnant woman will increase the risk of leukemia in her offspring.

Jennifer Griggs, M.D., M.P.H.: We generally consider radiation therapy much more dangerous in a pregnant women than chemotherapy, which surprises many people.

Sue Heffelfinger, M.D., Ph.D.: There are studies of children who have been irradiated for specific diseases such as Hodgkin's, who developed breast cancer later on. So there really is a childhood age range where radiation should be kept to an absolute minimum.

Jennifer Griggs, M.D., M.P.H.: At the University of Rochester, we have done much of that work, looking at age of therapeutic radiation and breast cancer risk and have demonstrated that therapeutic radiation around the ages of 10 to 14 has the highest risk, and that's when breast tissue is considered to be proliferating [growing].

Devra Davis, Ph.D., M.P.H.: I have a sad personal comment—when my daughter was 10, we rushed to the hospital because she might have had a ruptured spleen. This is a serious issue, so they wanted to do a CAT scan. And CAT scans, as we know, contain higher doses of radiation.

I asked the young radiologist who was a woman if she would shield my daughter's nipple area, and she looked puzzled and asked why. I explained her breasts would be developing. She said, “She doesn't have any!” I told her the vulnerability to the cancer-causing effects of radiation is dependent on the rapid cell growth of a young girl, and this young radiologist was really perplexed. So I took my gloves and held them over my daughter's chest area because I was concerned. As others have just said, we know very well that the younger the age at first exposure (and particularly when exposure takes place at a time of great development), the greater the risk.

Sue Heffelfinger, M.D., Ph.D.: That is a very sensitive period, but mammary glands undergo periods of growth with each menstrual cycle. Radiation sensitivity probably lasts well beyond that early stage.

Devra Davis, Ph.D., M.P.H.: That's very interesting. Has anyone ever looked at whether or not the timing of mammography could have an effect, in terms of a woman's cycle?

Sue Heffelfinger, M.D., Ph.D.: Certainly the risk hasn't been found to be that definitive, so I don't know of any data off the top of my head. Cycle time and time of surgery has been studied, but I don't think there's been any study of risk of mammography and cycle time.

Devra Davis, Ph.D., M.P.H.: It might make a lot of sense. There's a lot we don't know. But we have some good scientific reasons to be concerned about some things. And I think what we're saying right now is that the timing of exposure can be as important as the dose. So that exposure to the very young girl is important, but even exposure at the time of greater cell growth of the breast in a more mature woman who is still having a menstrual cycle could still be important. So you might want to not have mammography towards the end of a menstrual cycle because that's the time the breast is in a proliferative state [when more cells are growing].

Jennifer Griggs, M.D., M.P.H.: I think we should clarify we're not talking about one, and only one, mammogram. We're talking about cumulative doses of radiation, that is, the build-up of many doses of radiation over time.

Devra Davis, Ph.D., M.P.H.: Of course, it's the cumulative dose.

Jennifer Griggs, M.D., M.P.H.: I'm wondering if the lack of compelling data supporting the use of mammography in women under 50 is because for every good that we do, we also may be undoing that with some exposure.

Does breast cancer develop as a teenager?

Question from LindaA: Are you saying that those of us who have breast cancer probably developed it in our teenage years?

Answers —Sue Heffelfinger, M.D., Ph.D.: Some current thinking on the process of breast cancer formation is that some of the initial genetic events (a process we call “initiation”) probably occur in this very young age range. Breast cancer takes years and decades to develop from the first genetic damage until there's something you can feel or see on a mammogram.

There's a great deal of debate. If a woman gets breast cancer in her 90s, how long did it take to progress? If you're in your 40s, it's a much shorter time frame, but you can't prove that either one began in childhood or teen years. We just don't know.

All breast cancers are different from one woman to the next, so the genetic pathway will also be different. Many of these very early genetic events and exposures to carcinogens we think can occur very, very early, potentially even in utero, in sensitive stem cells in the mammary glands.

Jennifer Griggs, M.D., M.P.H.: This long period for development of cancers makes the risk of developing them hard to study. For example, we're asking women in their 60s where they lived when they were teenagers. This may be one reason the answers are slow in coming.

Devra Davis, Ph.D., M.P.H.: That's a very good point. It may be that breast cancer that occurs prior to menopause may be a fundamentally different type of disease compared with breast cancer that occurs after menopause. There may be very different factors for each.

There are some things, however, that appear to protect against breast cancer no matter what age they occur at. For example, vigorous exercise is protective against breast cancer. It's especially protective for young women who have been active for much of their lives, but there's also a benefit for older women who may not have started exercising until they're older.

Jennifer Griggs, M.D., M.P.H.: Can you define “vigorous”?

Devra Davis, Ph.D., M.P.H.: Leslie Bernstein, who's done much of this work, was herself a world class swimmer and “vigorous” refers to more than an hour a day of elevated cardio workout. The question of whether more moderate exercise is a benefit is still open, although as you know there are many good reasons why women should exercise regularly.

One of the theories why exercise does work to reduce the risk of breast cancer comes from the work of Brad Lowe and others. They have shown that women who exercise regularly and vigorously have lower amounts of circulating levels of free estradiols, and the lower amounts of free estradiols appear to be associated with a lower risk of breast cancer.

Alcohol has been shown to increase the amount of circulating estradiols, and so does hormone replacement therapy. So women who are on HRT and who drink regularly have an even greater risk of breast cancer, perhaps because both alcohol and HRT increase the amount of circulating estradiols.

Jennifer Griggs, M.D., M.P.H.: Could you comment on the role of folate for women who are interested in reducing their breast cancer risk and who enjoy a glass of wine at dinner? I have been recommending that patients increase their intake of folate in vegetables and even consider supplementing their diets with folate if they want to continue to enjoy a glass of wine a day.

Devra Davis, Ph.D., M.P.H.: I think that's an excellent suggestion. Also, there are probably some other benefits of alcohol, but clearly breast cancer is problematic.

Sue Heffelfinger, M.D., Ph.D.: There's a limit to the amount of data correlating alcohol intake with family history. The data suggests it is an increased risk factor if you already have a family history.

Jennifer Griggs, M.D., M.P.H.: I just want to stress at this point in the conversation that most women with breast cancer have no obvious risk factors for breast cancer and that, even if one of the things we've talked about applies to you or your sister or your friend, what we're talking about probably has more to do with populations or groups of women rather than applying to an individual woman. So if you were indulging back in your high school and college days and wonder if your breast cancer is a result of your own indiscretions, we want to relieve you of that concern.

Devra Davis, Ph.D., M.P.H.: The sad truth is that only less than 1 in 10 cases of breast cancer occurs in a women who has inherited a defect in her genes that she received from her parents. So this means that 9 out of every 10, and more like 19 out of every 20 were born with healthy genes; they didn't inherit the disease. So something has happened in the course of their lifetimes to give them breast cancer and we know that most cancer comes about because our genes stop doing their job of keeping cells under control.

What household products cause breast cancer?

Question from Gloria: Does hair dye, lipstick, makeup, or house cleaning detergent cause breast cancer? What about canned goods that have chemicals that mimic estrogen? I wash my veggies in a vinegar wash and I am not sure if this does anything to stop the effects of harmful pesticides. HELP.

Answers —Sue Heffelfinger, M.D., Ph.D.: There are very few epidemiological data that point to any specific product or any specific chemicals as being a cause of human breast cancer. Many of these products and chemicals, when given to laboratory animals, increase the frequency of mammary cancer and therefore are worrisome. In the world today, we are exposed to many agents, some of them naturally occurring and some of them man-made, that either cause direct genetic damage and therefore might be able to produce cancers, or which alter our hormone levels which might encourage cancerous cells to grow.

But it's very difficult with all of these chemical exposures that are a daily event in our lives to know which are important. And so, when it comes to risk reduction and trying to decide whether to use a particular product or eat a particular kind of food, there are very few hard and fast recommendations other than to cut down on your exposures whenever you can.

Devra Davis, Ph.D., M.P.H.: I agree with what you just said, but there are some studies in animals that have found certain types of plasticizers (compounds put into plastics to make them harder) can accelerate breast cell growth in animals and have a number of other effects on reproduction and the endocrine system, especially in baby boys.

There have also been case reports that we describe on our website, showing that young black baby girls who developed premature breast growth between the ages of 1 and 3 years had been exposed to hormones from personal care products, which their parents had used on their daughters' hair and scalps. When this exposure stopped, the breasts went away in these baby girls. Unfortunately, very few people know about this problem.

But Dr. Chandra Tiwary, who is a pediatric endocrinologist, reported a case series of young girls with premature breast growth and exposure to hormones in hair products. He also documented finding a hormone in a number of widely used personal care products in the African-American community. The FDA does not regulate personal care products unless they are officially called “hormones.” These products are not identified as hormones. Dr. Tiwary made his report about 7 years ago, but these products are still on the market. Certainly anything that can cause a baby girl to develop breasts is a problem.

Jennifer Griggs, M.D., M.P.H.: There are a lot of policy issues coming up in our conversation tonight. Workplaces and communities can increase opportunities for vigorous exercise and help with education for risk reduction, especially if certain products are associated with increased breast cancer risk.

Have food preservatives increased occurrence?

Question from TGlobal1: What impact do food preservatives have on breast cancer occurrence?

Answer —Devra Davis, Ph.D., M.P.H.: We don't know, but at the turn of the century, arsenic and mercury were typical food preservatives. They worked! But they also created other problems. There is no free lunch. So it may be that some of today's food preservatives are problematic, but that may change. After all, we've learned not to use arsenic and mercury in our foods and are no longer poisoning people with those chemicals.

Reasons for lower cancer risk in Japan?

Question from Geri41: They say Japan has a lower risk of cancer but their air quality is not good. Do you think it is their diet?

Answers —Devra Davis, Ph.D., M.P.H.: I've actually studied the environment in Japan. They have 4 to 5 times less breast cancer, less prostate cancer, and even less brain cancer. But the trends in Japan are also increasing, especially in women in the city, when it comes to breast cancer. There are big dietary differences, and there are also big differences in exercise. People in Japan walk a lot more than we do. They also eat diets that contain a lot more vegetables and soy products, and they do not eat as much saturated fat and animal fat. In addition, until very recently in Japan, women could not even get birth control pills [so they were not exposed to estrogen from that type of medication].

There are lots of things that could explain the differences. In fact, the Japanese, if anything, have better air quality than we do, in part because they can't afford to drive. The toll roads from Tokyo to Kyoto, a trip of about 2 hours, literally costs about $90 for a car. So it's a very different world in terms of some of the pollution patterns they have.

Jennifer Griggs, M.D., M.P.H.: They also have a higher incidence of other types of cancer.

Sue Heffelfinger, M.D., Ph.D.: Yes, because they use more salted food with nitrites so there is a higher incidence of stomach cancer.

Jennifer Griggs, M.D., M.P.H.: Back to that “no free lunch” idea.

Does chlorine in pools increase risk?

Question from MarshaF: Does the chlorine in swimming pools promote breast cancer?

Answers —Devra Davis, Ph.D., M.P.H.: Well, it prevents cholera! :-) We have improved our ability to reduce the amount of free radicals and other byproducts of chlorine right now. But again, there's no question that when you chlorinate water, you do create byproducts that have been shown to increase certain types of cancer. But if we did not treat our swimming pools, we would have outbreaks of infectious diseases. So the challenge is to treat our pools with limited residual chlorine byproducts and there are ways to do that now. These are widely available, and people should ask their municipal water suppliers to tell them they are using the best and latest technologies.

Jennifer Griggs, M.D., M.P.H.: What about baby diapers in swimming pools?

Devra Davis, Ph.D., M.P.H.: We can't escape germs, and we shouldn't even try to do so. In fact, one concern I have about bactericidal soaps is that they have been shown to increase susceptibility to common bacteria in life. We need some exposure to bacteria for our immune systems. But having said that, I'm appalled that some people don't realize that when you go into a hot tub, you should be clean. Also, you should NEVER think of taking an infant in a diaper into a hot tub. It would be like swimming in a little cesspool.

Sue Heffelfinger, M.D., Ph.D.: The temperature alone is not good for a child in a hot tub!

Devra Davis, Ph.D., M.P.H.: I can't imagine subjecting a child to the stress of dehydration in a hot tub. It's appalling that people don't understand that it would be bad for the child as well for everyone else, since e.coli bacteria is transmitted by feces.

Link between antiperspirants and breast cancer?

Question from SueW: Is there any evidence that use of underarm deodorants/antiperspirants is linked to breast cancer?

Answers —Sue Heffelfinger, M.D., Ph.D.: I don't think there are any data that have shown a link. I think the concerns with some of the deodorants as well as other personal care products has been the estrogen products we mentioned earlier, but the animal data are not clear and as far as I'm aware, there are no epidemiological data to support a causal role.

Devra Davis, Ph.D., M.P.H.: That's true and probably going to be true for the rest of our lives. So what do you do in the meantime? I think a prudent avoidance of suspect material is all we can say. The reality is we do not have human evidence of harm. But that should not be confused with meaning that there is no harm. It merely means that, given the tools we have available to us now, we cannot answer the questions with studies in humans.

Could building materials increase incidence?

Question from CBabe: I worked for a company for 5 years where 6 women in our department got cancer. The building contained asbestos and other toxins. Could this be coincidence?

Answers —Devra Davis, Ph.D., M.P.H.: The asbestos studies that have been done clearly show an increase in a number of respiratory cancers in workers. Most of the workers studied have been men. There is a very clear suggestion of an increased risk in breast cancer in women who did work with asbestos. The number of women concerned is small, so the association did not achieve what we call statistical significance.

There could be an association between asbestos and breast cancer and frankly, if the environment included asbestos, it may have included other [harmful] agents as well. I'm not aware that brain cancer is associated with asbestos, but that doesn't mean there is no association, only that we don't have evidence that there is.

Jennifer Griggs, M.D., M.P.H.: Clearing asbestos is not the answer either since removal of asbestos increases the fibers in the environment, which can cause damage.

Could toxins in textiles cause breast cancer?

Question from Hbgin: My mother died of breast cancer. She worked at a chain of stores in which she cut cloth materials. Could there be some toxin in the materials that contributed to this?

Answers —Jennifer Griggs, M.D., M.P.H.: It's such a common impulse to explain things that have happened to us. Much of the conversation now has been a desire to seek answers for something we can't really explain.

Devra Davis, Ph.D., M.P.H.: All the studies we talk about here, where we have evidence of an increased risk of breast cancer, necessarily look at groups of people over time, and yet cancer affects individuals one at a time. So we are really limited when it comes to understanding the causes of breast cancer in individual women. With respect to textiles, however, many modern textiles are treated with formaldehyde and dyes, and these things have been found to increase mammary tumors. There are some workplace studies as well that indicate that this could be a risk for breast cancer in groups of people with this kind of exposure.

People who work as dry cleaners who were in that industry 20 to 30 years ago were exposed to chemicals that may cause mammary tumors. Women who use dry cleaning may be at a higher risk for developing breast cancer as well. So now there is a move to “green” dry cleaning that uses organic solvents instead of chlorinated hydrocarbon solvents. This is a good development for two reasons: some of these chlorinated solvents contribute to greenhouse gas emissions and some of these contaminate groundwater and are associated with an increased risk of health problems.

Can Teflon cause cancer?

Question from Jeri: Can Teflon on pots cause cancer? What's the risk with microwave use?

Answer —Devra Davis, Ph.D., M.P.H.: Persistent fluorinated compounds have increased dramatically in harbor seals and other animals in San Francisco over the past decade. They have also increased in breast milk. The Swedish government banned the use of these compounds, such as those used in Teflon, and found a dramatic drop in residues in breast milk within a decade of doing so.

There have been some experimental studies indicating that these compounds disrupt the immune system and could contribute to cancer. Because these compounds are so persistent in the environment, the manufacturers reported some of the evidence on their persistence to the EPA (Environmental Protection Agency) about four years ago. There's a lot of debate about whether or not they could be contributing to a wide range of health problems.

Right now, the Teflon-related compounds are everywhere. They are used to treat draperies and fabrics. A lot of people are working hard on to find less-toxic substitutes. As for the pots, high heat and burning the Teflon should be avoided at all costs. I just don't know if routine use is a problem.

Is new detoxification product safe?

Question from Fighter: There is a new product called DME Natural which is “generally recognized as safe” by the FDA which is supposed to take heavy metals, toxins etc. out of the body in a totally safe way. It is patented as “Epithelial Cell Cancer Drug” patent # 6,288,045. What do you know about this product?

Answer —Sue Heffelfinger, M.D., Ph.D.: Safety and efficacy for any compound, nutraceutical or pharmaceutical, can only be assessed in a clinical trial. To my knowledge, there have been no clinical trials for this particular product, therefore we have no data at all on safety or efficacy.

Growth hormones in beef and chicken?

Question from JacobM: Which has the most growth hormone—chicken or beef? I try to eat organic whenever possible, but would like to know which one is better when organic is not available. Thank you.

Answers —Sue Heffelfinger, M.D., Ph.D.: I'm not an expert on this, but my understanding is that they're still using a growth hormone in beef production, even in milk. Chickens and pigs can have what they call growth additives, but not hormones. There is some risk that the feed for chickens and pigs may actually have beef in it that had growth hormone. That would have to be confirmed with the Department of Agriculture, but that's my understanding. Chicken may have contaminated feed, but it's illegal to add hormones directly to chickens.

Jennifer Griggs, M.D., M.P.H.: Is it fair to say that occasionally having non-organic chicken or beef is a reasonable thing, for example at a restaurant?

Sue Heffelfinger, M.D., Ph.D.: I really think—again, it's only personal opinion—that one has to be reasonable with moderation in all things. I certainly don't avoid restaurants that don't serve organic meats. Reduction of your total meat consumption for many health reasons is a good idea. If you're fortunate enough to be able to afford and acquire organic meat, that's fine. But I think that you don't need to feel guilty if you can't afford it or if you want to go out and enjoy meat in a restaurant.

Jennifer Griggs, M.D., M.P.H.: That's good, because I'm usually too tired to cook!

Do plastics release toxins into food?

Question from ChristineM: Having read about artificial estrogens, I store everything in glass containers rather than plastic. I heard that cooking or freezing in plastic can release carcinogens (dioxin?) into the food. And what about fumes from gas heating and cooking? What about plastic water bottles?

Answers —Sue Heffelfinger, M.D., Ph.D.: There's much, much concern about plastics. Even in animal studies, it's an issue to make sure we don't contaminate experiments with plastics, especially old ones that have been used and washed many times.

As for water bottles, it depends on the plastic. Polyethylene is relatively safe. If you look at the bottom of your plastic bottle, there is a number in a little triangle. Look at Consumer Reports or The Green Guide for more info.

Generally you don't want to heat or cook with most plastics. It would be a better world if the plastics manufacturers provided us with information on these issues, rather than us having to become experts on what is a good or bad plastic.

Again, human data are just not available. So in personal practice, avoiding heating plastics and going to glassware if possible is wise.

Jennifer Griggs, M.D., M.P.H.: Just to clarify, microwaving in plastic is not advisable?

Sue Heffelfinger, M.D., Ph.D.: I would certainly avoid it, even for the concern we have with the plasticizers being released. It's really an avoidance issue in the absence of real data on human health effects.

What constitutes a cluster of diagnoses?

Question from Sue: I teach at a school that has had what some would consider a cluster of breast cancer and other cancers. My assistant and I have BOTH been diagnosed just this summer with IDC. There are rumors of toxicity, and we have a documented mold problem. What constitutes a “cluster” that can be investigated and hopefully remedied?

Answer —Sue Heffelfinger, M.D., Ph.D.: This is one of the most common questions nationally. There do appear to be neighborhoods, buildings, or workplaces where all of sudden you notice many people being diagnosed with breast cancer. Sometimes there is a culprit and sometimes there isn't, and the question is, what do you do about it? Certainly notifying physicians and health officials in your region is appropriate to see if there resources available for investigation.

But what I say often, particularly because of the deep level of concern from families in that cluster area, is to keep in mind that with the extraordinary frequency of breast cancer in our population, just by statistics alone you're going to find some of these clustering events that are really not related to local exposure, but to the fact that this is a very common disease. Many large clusters have been extremely well-investigated, and if you look at some of the websites we've mentioned, you may find information about Marin County, CA and Long Island, NY which are two of the best studies of cluster cohorts.

Does IVF increase risk?

Question from BenNZoeysmom: Do you feel that women who have gone through IVF have an increased risk of breast cancer?

Answer —Jennifer Griggs, M.D., M.P.H.: It seems that every study I see contradicts the one before. In other words, a study may come out suggesting an increase in the risk of breast cancer, and then an even better study says the association is not present.

Triggers for cancer to become invasive?

Question from Sue: I read that there is often a triggering event, or perhaps exposure/stress that gets the latent breast cancer to become invasive. Is that true?

Answers —Sue Heffelfinger, M.D., Ph.D.: By trigger event we mean an accident, some injury to the breast or other event. When breast cancer is diagnosed soon after that, it is really more related to the timing of seeing a doctor for the stressful event. The breast cancer just happens to be found by medical examination at the same time. There's probably not any biological reason that altered the rate of breast cancer development. There is data that suggests the immunosuppression related to stress can be a factor in cancer development. But having a stressful event per se will not cause a woman's breast cancer to suddenly become invasive.

Jennifer Griggs, M.D., M.P.H.: I think cancer development is so much more complicated than a stressful life event might indicate. The most recent studies looking at stress and breast cancer occurrence have indicated no connection. In other words, although minimizing stress in your life is good for other reasons, stress does not seem to be a contributing factor to breast cancer recurring.

Sue Heffelfinger, M.D., Ph.D.: My impression is that some stressful events make one more concerned about one's health in general, so women in those circumstances may then discover a cancer.

How can I enroll in risk factors study?

Question from Jana: I would love to be included in a study of where people grew up and the age at which cancer developed. I lived near a factory that produces car parts for the first 9 years of my life, then again in my early twenties.

Answer —Sue Heffelfinger, M.D., Ph.D.: I would recommend that people go to the NCI website, http://www.nci.nih.gov/clinicaltrials and search that way, to look for potential studies.

Do parabens in beauty products increase risk?

Question from DollyD: What about parabens in lotions and skin care products?

Answer —Sue Heffelfinger, M.D., Ph.D.: There are some laboratory studies that are beginning to look at parabens in terms of their hormonal activities. These are just beginning to be studied, enough that there's now some concern, but we have very little data.

Does living on a landfill increase risk?

Question from Geri41: What do you think about building houses on landfills (garbage sites)? Have you noted an increase of cancer in these areas?

Answers —Sue Heffelfinger, M.D., Ph.D.: Landfills are long-term (meaning decades to centuries) active places where there is all sort of leaching of chemicals, runoff, and released gases that occasionally catch on fire. So one should be very cautious about long-term exposure, such as building a house, close to one. Certainly all caution would say that this is not a wise place to build.

Jennifer Griggs, M.D., M.P.H.: Does either of our guest experts want to comment again on the burden put on the consumer and possible ways to share that burden with industry and regulatory agencies?

Sue Heffelfinger, M.D., Ph.D.: When you look at many of these questions, it's really not science but personal opinion. There is power in the consumer avoiding products, and letting industry know you are avoiding them. Money does talk. Through advocacy groups banding together, there is even more power in the purse. That is one kind of power we have as concerned individuals.

However, that isn't enough. Other countries take these concerns at a policy level seriously. We are fortunate in the U.S. to have some extremely active advocacy groups among breast cancer survivors and family and friends who have been pushing our legislative bodies and regulatory agencies to investigate many of these compounds experimentally.

But the unfortunate thing is there are so many chemicals in our environment, and there isn't enough money in the world to study all of them in animal studies, let alone major epidemiological human studies. So policy decisions must be made, absent definitive data.

We must work together, not just the breast cancer advocacy groups, but many other advocacy groups. Many of these chemicals don't just affect breast cancer; often they're harmful to the cardiovascular system, and other systems may be involved too. So we need to think wisely about what we as a nation want to do about many of these compounds. These are really policy level decisions that will have to be made, in the absence of real data.