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.