Air Date: Week of June 8, 2007
Dr. Devra Lee Davis it Professor of Epidemiology at the University of Pittsburgh's Graduate School of Public Health. (Courtesy of University of Pittsburgh)
A recent meta-study published by the American Cancer Society suggests that over 200 chemicals found in everyday products cause breast cancer in animals. Devra Lee Davis is director of the Center for Environmental Oncology at the University of Pittsburgh Cancer Institute. Dr. Davis tells Living on Earth’s Steve Curwood about the evidence that links environmental factors to breast cancer and how reducing exposure can help prevent women from getting the disease.
GELLERMAN: It’s Living on Earth. I’m Bruce Gellerman. Just ahead: Eavesdrop on the globe, Google-style. But first: For years now, many activists and a growing number of scientists have been convinced that there’s a link between environmental contaminants and cancer in people—especially breast cancer.
Now that concern seems to be emerging from the margins to the mainstream. Recently, five major research institutions reviewed more than 900 scientific studies, which identified more than 200 chemicals that cause breast cancer in animals. Now, the researchers believe these chemicals, found widely in pesticides, cosmetics, dyes, drugs, gasoline and diesel exhaust, may be linked to breast cancer in humans. Their results were published online by the American Cancer Society.
Devra Lee Davis is director of the Center for Environmental Oncology at the University of Pittsburgh Cancer Institute. Dr. Davis recently spoke with Living on Earth host Steve Curwood about the connections between toxic pollutants and breast cancer.
CURWOOD: Now, how might pollution cause or promote breast cancer? What’s going on here? And what about men?
DAVIS: We know that the more hormones in a woman’s body over her lifetime, the greater the chance that she will develop breast cancer. The earlier in life she starts her period, if she has no children the more hormonal cycles she will have and the greater her risk of having breast cancer. We also know that there are a number of environmental materials that can act like hormones. And these hormone-acting or hormone-mimicking compounds can also play a role in contributing to the increased risk of breast cancer. So you have natural hormones that the body makes itself and you have synthetic agents that can act like hormones. And the combination we think is what results in breast cancer in many cases.
Because think of this: only one in ten women who develop breast cancer do so because they inherited a defective gene from their parents. That means that 9 out of 10 women who get the disease were born with healthy genes. And yet something happened to those genes in the course of a lifetime to give them breast cancer.
DAVIS: Well, if you’re an adopted child your risk of breast cancer and other cancers parallels that of the family that you grow up in, not the one into which you were born. We know that because in Scandinavian countries they have detailed registries to follow people from birth to death. And they followed adopted children and they found this out. What we understand is that if cancer runs in your family it could be because your family had similar eating patterns, similar lifestyle patterns as well as lived in the same area.
CURWOOD: So, this report says what there are some 216 chemicals with carcinogenic properties that could be responsible for breast cancer. What sorts of chemicals are we talking about here?
DAVIS: Well, let’s first establish this: every chemical that we know for sure causes cancer in humans has been shown to cause it in animals when experimentally tested. That’s a very important fact. Now the question is, is the obverse true? Namely, is every chemical we know that causes cancer in animals – should it be regarded as though it causes cancer in humans? I happen to think yes it should. We should pay attention to these animal tests and that’s what this study of Silent Spring Institute has done.
They’ve identified 216 chemicals that are shown to cause breast cancer in animals when tested under controlled conditions. Some of the chemicals that they are talking about are very widely spread in our environment. For example 1-3 butadiene is a common air pollutant. It’s in gasoline. It’s obviously found in the urban environment wherever there are cars or trucks or busses. Benzene is a similar pollutant found in gasoline and therefore engine exhaust. Methylene chloride you may not know it but some furniture, polish some fabric cleaners, and a lot of wood sealants in the past have used methylene chloride and although it is supposed to be being phased out you don’t know whether it is in these compounds now or not.
CURWOOD: So, almost anywhere it seems then you could be exposed to a chemical that gives you breast cancer.
DAVIS: Well, let’s just say that the exposures are widespread and that’s why it’s really important that we take another look at the way we are organizing our society and the kinds of chemicals that we are using everyday. We think that there are alternatives that can be used. Here in Pittsburgh we are leading the way with green chemistry. We don’t want to wait until we have proof in humans that the chemicals that we now know cause cancer in animals will do so in humans. But in many cases we already have that evidence for some chemicals and we ought to act on the basis of what we know now to continue to reformulate and redesign our products. Big business is going to make a lot of money by doing that.
CURWOOD: Now, how do we look at 216 chemicals one at a time? How do we make sound policy out of that?
DAVIS: That is the sixty-four thousand dollar or perhaps the sixty-four million dollar question. One of the things that’s being done in Europe now is the REACH program. They are reregistering and evaluating chemical hazards by asking manufacturers to give them information that will be used to reregister and reconsider some of the highest volume chemicals in commerce today.
CURWOOD: Dr. Davis, what’s the purpose of releasing a metastudy like this, is this a call to regulators to individuals?
DAVIS: I think the purpose of this study was two things. First, was to show there was a robust and extensive literature out there; studies in animals, studies in cell cultures, and some studies in humans. The second point of this review is frankly, you have to see where it’s been published. It’s being published in the major journal of the American Cancer Society. The American Cancer Society has been somewhat slow to embrace the environment as an issue. And I think the fact that the American Cancer Society published it is really signaling a sea change in public attitudes about the environment.
CURWOOD: Why is it that while there’s a great deal of work been done to look at the link between diet and breast cancer, there’s a lot less that links environmental contaminants and breast cancer?
DAVIS: Well, there are two reasons. First, is it’s hard to do the research. It’s not easy. Life doesn’t come at you as we test it in these animals. You don’t get exposed to one chemical at a time. You are exposed to a mixture. Life is a mixture. It’s hard to study mixtures. And right now the funding for public health research is at an all time low. So, we’re not asking the question. We’re not collecting the data. It’s difficult to do it well. That’s for starters. The second reason is that if you don’t look, if you don’t ask, you can’t find it. And right now we are not asking this question. Even though it’s a hard question to ask. We don’t for example when you go into the hospital, when you go to your doctor, your doctor doesn’t ask you, “Where do you work? What chemicals do you work with? Where do you live? What’s in your drinking water? What are your good and bad habits?” Those questions are not generally asked.
CURWOOD: So, where do we go from here? There are all of these chemicals that can cause breast cancer or promote it in women. What should people take away from this news?
DAVIS: Well, there’s some good news Steve. The good news part comes from the work on nutrition. What we can do, knowing that we live in the modern world with these exposures is be vigilant about what we eat and where we live. And the way I say it is, it’s important to try to live high in the watershed, above pollution. And eat low on the food chain, which means that you want to eat foods that are low in pesticides. The fattier the food the more opportunity it has to absorb many toxic chemicals. So, having a diet that is low in animal fat is important. At this point we have no excuse not to act based on this information. But it’s not a reason for panic. It’s a reason to strengthen our resolve to make sure that we eat better and exercise, and reduce our exposures and do the same things with our families and children.
GELLERMAN: Dr. Devra Lee Davis spoke with Living on Earth host Steve Curwood. She is director of the Center for Environmental Oncology at the University of Pittsburgh Cancer Institute. Her new book is called “The Secret History of the War on Cancer.”
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