Two new studies link diseases with exposure to low levels of chemical pollution. One study suggests the chemical Bisphenol-A, found in some plastic bottles and food cans, can promote prostate cancer. The other study finds small amounts of pesticides can stimulate allergic reactions, including asthma. Dr. Pete Myers, chief scientist for Environmental Health Sciences, tells host Steve Curwood about the studies.
CURWOOD: It’s Living on Earth. I’m Steve Curwood. Despite advances in modern medicine two epidemics seem to be growing; those of prostate cancer and of asthma. Now there are some provocative new studies that link these diseases to exposure to tiny amounts of pollutants. One study finds that low-level exposure to the chemical bisphenol A found in some plastic bottles and some food cans can promote certain prostate cancers. That study has just been published in the Journal Molecular Cancer Therapeutics.
The other study indicates tiny amounts of pesticides and PCBs that mimic estrogen can stimulate the process of allergic reactions, most notably asthma. That’s reported in the current issue of Environmental Health Perspectives. Joining me now to talk about this emerging research is Dr. Pete Myers. He’s the chief scientist for Environmental Health Sciences, which publishes the online journal Environmental Health News.
Hello, Dr. Myers.
MYERS: Hi Steve, how are you today?
CURWOOD: Good. Now the first study we’re going to look at, the researchers for this one found a link between certain environmental contaminants that mimic estrogen and allergic reactions including asthma. What’s going on here?
MYERS: Well the big question out there is why are so many allergic diseases increasing. Asthma’s increasing. Allergies to things like peanuts is increasing. It’s really an epidemic of allergic disease. And scientists have been looking for clues about what could be driving this. And this new study shines a very bright light on one possible explanation. Our immune system depends upon estrogen signals to adjust how sensitive it is. A little bit more estrogen and your immune system becomes a little bit more sensitive. And so what these scientists did, was a different type of question. They recognize that there are actually chemicals in the environment that behave like estrogen. And so they began to perform a series of experiments where they took cells from mice and from people and they looked at the effective exposure to these estrogenic chemicals on the sensitivity of the cells immune systems. And low and behold they found a very very strong effect.
CURWOOD: So what kind of environmental contaminants are we talking about here? Where are they found and how do they wind up in our bodies?
MYERS: Well, these contaminants are a series of persistent organic pollutants: old pesticides, DDT, DDE. Things that have lingered, been used for a long time in the environment, even if they’re not being used now. But because they are persistent they still make it into our food supply.
CURWOOD: Now, why has it taken so long to figure this out? What is it about the effects of these chemicals that makes it hard to see the link between allergic reactions and these chemicals that act like estrogens?
MYERS: Well first of all you have to think that the question is relevant. And it’s taken a while for the scientists who work on these types of issues simply to ask about the potential contribution of estrogenic substances to allergic disease. But now that they’ve started asking the questions they’ve discovered a very interesting aspect of how these contaminants alter immune system function. What they’re seeing is that really low doses ratchet up immune system sensitivity but that higher doses shut it down. And that dose response relationship is both something that’s relatively new to toxicology but it’s also one that’s hard to investigate.
CURWOOD: So, wait a minute. You’re telling me that someone who was exposed to a lot of DDT it wouldn’t have affected their allergic response to something but if it was just a little bit it would?
MYERS: Well, it isn’t so much that a high dose wouldn’t have affected it. A high dose would shut it down. Think about the surge protector that you use for your computer. Your computer needs electricity but if all of a sudden too much comes through it shuts down the system. Well that’s the sort of thing that appears to be happening here. Our immune system has to be able to respond to the signals that the body naturally sends it. Those signals are taking place at really low levels. As they increase the reactivity of the immune system rises. But if all of the sudden there is a surge that’s unexpectedly high, the system shuts down and that’s what appears to be happening.
CURWOOD: So that is very confusing if you’re doing research and you’re just looking at the chemical and its effect it’s paradoxical. Sometimes it works and sometimes it doesn’t.
MYERS: It is. It’s been one of the great challenges to research in this area and especially to how we go about establishing health standards. Typically the toxicological tests that are used to figure out whether this compound is safe and at what level it is safe. They begin at high doses and then they work down until they don’t see an effect. Well if the chemical that you’re working on at low doses causes an increase and at high doses causes a suppression you’re not going to be asking the right questions.
CURWOOD: Dr. Myers I know the study didn’t look at this at all but the asthma epidemic is really big in cities and really big among poor people. What questions would you want to ask as a researcher to link that prevalence of disease in those populations to what is being found in this research?
MYERS: That’s a great question, Steve and all the science isn’t in on the answer yet. But there are a couple of clues that we can take from this. One is that the biggest source of exposure to these things is dietary. Diets that are high in fat are more likely to expose you to some of the persistent contaminants that this study focused on. The other thing that science is pointing toward is the fact that cheaper grade construction materials often contain compounds that the science links to increased immune system sensitivity.
CURWOOD: In other words your house could be causing you asthma.
MYERS: Your house definitely could be causing you asthma. There have been some very interesting studies looking at the composition of dust in houses and the relationship to risk of asthma and there are significant associations being found.
CURWOOD: And so what does this research suggest? I mean, what’s the big picture here in terms of asthma?
MYERS: Well, the big picture is this: we know that we’re in the middle of an asthma epidemic. And people have been struggling with the question. Why are we seeing this? Why is asthma increasing at a time when for the most part air quality has been getting better? The answer this study suggests is it isn’t that there’s more pollution, it’s that we’re more sensitive to the pollution that’s there. Our immune system is responding more strongly to the irritants that have been around the whole time. It’s just that we’re more sensitive to them now.
CURWOOD: Let’s take a look now at that other study that considers tiny doses of toxic substances and this is the one that links prostate cancer to bisphenol A, which is commonly found in plastic bottles and the lining of some food cans. Now I understand that this study shows that tiny amounts of the toxin can interfere with a common treatment for prostate cancer. How did they come to that conclusion?
MYERS: What these scientists did was they implanted prostate tumor cells from people into mice. And then they looked at the effect of exposing those mice to bisphenol A. And what they found was that bisphenol A made the cells switch into a state where they couldn’t be controlled by the normal way physicians manage prostate cancer.
CURWOOD: How could BPA interfere with prostate cancer treatment?
MYERS: Well, normally when a guy has prostate cancer it turns out that those tumors need testosterone to divide and grow. And that’s a condition that’s called Androgen Dependence. Testosterone is an androgen. So, if the physician can either lower the guy’s circulating testosterone levels or somehow make him less sensitive to testosterone using pharmaceuticals they can keep the tumor under control. So what this new science tells us is that if the tumor is exposed to bisphenol A, it shifts. All the sudden it’s no longer dependent on testosterone to proliferate.
CURWOOD: How do you avoid bisphenol A? I understand it’s in 95 percent of us.
MYERS: It’s in 95 percent of us but not all at the same levels. I’ve taken one very practical step which is I avoid canned food. I also don’t use those wildly popular sports bottles that are made out of polycarbonate plastic. There are ways that individuals can decrease their exposures. There’s no question about that.
CURWOOD: Ok, so we’ve got this one new study from the University of Cincinnati that finds a link between bisphenol A and prostate cancer. And then we’ve got the other new study from the University of Galveston that we talked about earlier, linking some persistent organic pollutants with asthma. So, tell me Dr. Myers what do these two studies say about the chemicals we’re being exposed to on a daily basis and our general health.
MYERS: Well they say two things. They say that the health standards that we have developed over the last 30 years are in the scientific Jurassic. They just haven’t been asking the right questions. But they say something else which I find very encouraging. The science is telling us that if we pay attention to it and we start making individual choices and societal choices about how we manage these chemicals and how we work to avoid exposures we can probably prevent some of the diseases that here to for we hadn’t thought were preventable. That’s pretty exciting.
CURWOOD: Dr. Pete Myers is chief scientist for Environmental Health Sciences in Charlottesville, Virginia. They publish Environmental Health News. Thank you so much sir.
MYERS: Thank you, Steve.
CURWOOD: You can find references for this research and a link for the Environmental Health News site at loe dot o-r-g.
[MUSIC: T-Rek “Drug Punk Lady” from ‘Rubber Records Sampler 2007’ (Rubber Records - 2007)]
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