Nearly a year ago, toxicologist Linda Birnbaum was named director of the National Institute of Environmental Health Sciences and the National Toxicology Program. She sat down with Environmental Health News journalist Jane Kay in San Francisco on Wednesday to answer questions about the environmental health risks we face today.
As head of the federal institute examining environmental health, Birnbaum and her staff are taking on many controversial topics, including Bisphenol A and new flame retardants in consumer products. She talks about those issues and explains how scientists are trying to figure out what role chemicals and contaminants may play in breast cancer and other diseases and disorders.
"I’m concerned about some of the plasticizers, including phthalates, and some of the flame retardants, especially the alternative ones," she said. "In this country, we kind of jump from the proverbial fry pan into the fire without thinking about the alternative."
Environmental Health News: You say if you don’t ask the right questions in science, you are not going to find the answers. Your agency has just dedicated $30 million to study bisphenol A, the estrogenic chemical found in polycarbonate bottles and food can linings. What are some of the questions we should be asking about bisphenol A and what are we doing to get the answers?
Linda Birnbaum: The $30 million program that we have on bisphenol A is looking at what can bisphenol A do, especially developmental exposures: At what doses do these effects occur and how serious are they? Some focus is on epidemiology but much of it is animal experimentation. We brought all of these investigators together in October to facilitate collaboration – sharing of samples, standards. We’re emphasizing that we really need to look at the low-dose effects. We’re looking at many different targets – the mammary gland, the prostate and immune and cardiovascular systems. Bisphenol A has often been called a weak estrogen. But it’s going to do some things that estrogen doesn’t do. So we have to look more broadly.
There are two recent human studies, one showing an effect on cardiovascular disease and one Kaiser Permanente study on workers in China (in polycarbonate-manufacturing plants) showing effects on male sexual function. Their occupational health standards are not as stringent as ours, and so there was a much higher exposure in that population. It’s kind of a new observation. The adult male effects are very interesting because we’ve seen similar effects in our animal studies. That strengthens my confidence in the new study. It needs to be repeated in another population, and we need a better understanding of how high the exposures really were in that population.
Bisphenol A has attracted a lot of public and scientific attention. What other contaminants deserve that sort of attention?
Anything where we have wide exposures in the population. Bisphenol A is not a persistent chemical. If it stopped being made, it would rapidly go away. Chemicals that are very persistent, we all need to look at because they are not going to go away. Sixty to 70 percent of the PCBs made are still out there. The levels are lower in our bodies than in our parents’ bodies, but PCBs are going to be around for a long time. I’m concerned about some of the plasticizers, including phthalates, and some of the flame retardants, especially the alternative ones. They’ve now found chlorinated tris that was banned in babies’ pajamas 30 years ago in high levels in sediments. It’s a real concern. It’s used in carpet padding and cushion foam, and it’s being found in house dust. So people are being exposed. In this country, we kind of jump from the proverbial fry pan into the fire without thinking about the alternative.
The Food and Drug Administration has said it will announce a new policy statement on bisphenol A by the end of the month. What do you expect?
I think the FDA is looking at the newest science, and I think it is going to take some time for that to happen. I don’t expect the FDA to come out and say the information is conclusive that bisphenol A is safe. All the regulatory agencies are beginning to realize it’s important to update approaches and look at all of the available science. The guidelines from the past may not be addressing questions we’re asking today.
Which exposures in everyday life do you consider the greatest risk factors for breast cancer?
Some of our greatest risk factors are obesity because of the excess estrogen associated with it. We know that women who are obese have a greater risk of breast cancer. If we’re talking about environmental chemicals, we know there are pharmaceutical exposures that may predispose women to breast cancer later on. We know hormone replacement therapy is associated with an increase in breast cancer. Since the report that it did cause breast cancer and many women have stopped taking hormone replacement therapy, we’ve seen a decrease in breast-cancer incidence, exactly what you’d predict for our understanding of how estrogens work. I have concerns about early-life exposures, and how that may predispose for breast cancer later on. We know that exposing animals in utero, or during the infantile period, or puberty or pregnancy can alter the breast responsiveness and change what may happen later on. When you have cells rapidly dividing and differentiating, that is the time they are especially vulnerable to the effects of chemicals. If you expose an organ in utero or in the infantile period, it may never develop normally.
What recent research funded by NIEHS shows the most promise for disease prevention in the near term?
We have developed sensors to measure exposures. If we know what people are exposed to, then we can prevent the exposures. With bisphenol A, where is it all coming from? It’s not just baby bottles. It’s not just cans. How is it getting into us? Is it getting into our food, in our drinking water, in our house dust? Let’s identify the major sources of exposure, and work to control those. The very minor sources may not be an issue. NIEHS identified the BRCA1 and BRCA2 genes, which has furthered breast cancer research. There is also the “sister study” of 51,000 women followed for 10 years looking at nutrition, lifestyle, exposure to environmental chemicals and biological markers.
What are we doing to answer the big questions: Are chemicals in the environment increasing breast cancer, reproductive diseases and neurodevelopmental/behavioral problems?
We’re addressing it at this point very much on a one-chemical-at-a-time basis. We need to begin to develop strategies to look more broadly because no one’s exposed to one chemical at a time. And we need a better understanding of whether the whole suite of chemicals in our bodies is associated with the problems. Nobody’s trying to look at the sum total. A study I’m trying to encourage is where you’d make a mix of what’s in the American population and expose animals to that mix. Maybe I would start in by looking at the high-end of the population. If we saw something in our animals, that would certainly be a concern. Now if we didn’t see anything, that doesn’t mean things aren’t happening. But I think it would be a study worth doing.
Do you still have concerns about people’s exposures to the brominated flame retardants, PBDEs?
Yes. There is no convincing evidence that PBDEs are declining in people or wildlife in the United States. It’s too soon. Manufacturers stopped production of penta and octa in 2004. The chemicals are still getting into the environment from existing products. Deca continues to be produced. Until recently, scientists didn’t measure deca in people. Deca rapidly metabolizes in people and wildlife but is very stable in the environment. PBDEs look as though they are on the decline in Europe where they were never used as widely as in North America. The European Union banned them in 2004. Germany banned them in the 1980s, and Sweden stopped use in the early 1990s. The peak levels in Swedish women occurred around 1997, and have since declined.
Many experts talk about the “data gap” when it comes to our knowledge of the risks of chemicals. How substantial are these gaps and how can we fill them? What new testing should be required?
Some [gaps] we can fill by testing, and some by doing specific studies. We have to prioritize the data gaps of the greatest concern. As the first toxicologist heading NIEHS, I will bring in exposure science. Toxicology is a hybrid science that examines the safety of different exposures using all the tools of molecular biology, analytical chemistry, biochemistry, physiology and pathology. Today’s toxicology is not our grandparents’ toxicology. It’s not the old-fashioned “dose ‘em and count ‘em.” I would like to see any study done on animals get a measure of the internal dose so we can compare the animal results to humans. We need to know if the levels in experimental animals that are associated with effects are similar to the levels that we’re finding in people. If the levels where we see effects in the animals are similar, or within a factor of 10 or more than we see in people, then I think we should be concerned. The standard tagline was “the dose makes the poison.” But it’s the dose and the timing that’s critical. Different things happen at different doses.
You have said, “Animals may not be people. But people are animals.” Can you explain what you mean by that?
Nature is inherently conservative. So many of the basic processes that govern development and physiology in fish, for example, are the same processes that occur in human beings. Some people are concerned whether rats or mice, or in some cases, cats or dogs or non-human primates, are good models for humans. If we have chemicals that cause a multiplicity of effects in several species, why would we think that some people are not going to be susceptible to the effects?
This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.
