As director of the National Institute of Environmental Health Sciences and the National Toxicology Program, Linda Birnbaum, PhD, DABT, ATS, oversees federal funding for biomedical research on how the environment influences human health and disease. A toxicologist by training, Dr. Birnbaum’s research is concerned with how environmental chemicals interact with the body, including their disruption of the endocrine system. In this Q&A, she discusses the difficult task of assessing tens of thousands of chemicals, how cities are increasingly healthy places to live, and a recent study of arsenic by Prof. Joseph Graziano. On April 23, Dr. Birnbaum will deliver the 21st Annual Sewell Distinguished Lecture, titled “When Our Environment Acts like Medicine...,” which will be broadcast live online.
How much of human disease is related to environmental exposure?
The World Health Organization has put that estimate as high as 85%. Some of it depends on how you define the environment.
How do you define the environment?
The environment includes things like industrial pollutants and pesticides and chemicals in commerce, but also includes the foods that we eat, the air that we breathe, and the water that we drink. It also includes things like our microbiome—bacteria, viruses, and fungi that inhabit us and certainly impact us. There is also the psychosocial environment and even pharmaceuticals and over-the-counter drugs.
How many chemicals are we exposed to, and how many of those have been tested?
There are 80,000 chemicals listed for commercial or industrial use [in the United States] and probably less than 20% of those have had any safety testing. And a smaller percent have had adequate testing. In addition to the listed chemicals are compounds and the breakdown products of chemicals—all of which we may be exposed to. The European Union has an estimate of about 143,000 chemicals.
Tell me about your new program Tox21 that allows researchers to assess greater numbers of chemicals.
Tox21 is a move to make toxicology a more predictive science by using various kinds of high-throughput and mid-throughput testing to develop pathways of toxicity, which are really pathways of disease, and to get a faster read on what may be the potential for human health effects. Doing animal studies is not only expensive but it takes years. And there are times when animal results may not be predictive of human results or all human results. Tox21 is a cross-government effort that is coordinated between the NIEHS, NCATS, the EPA and FDA. We are testing very large numbers of compounds through many, many different kinds of short-term tests, both in vitro and some that may be in C. elegans, drosophila, or zebrafish.
A recent study by Joseph Graziano here at the Mailman School and funded by the NIEHS looked at arsenic in well water in Maine—
A very important study and I’m glad it got published!
You know the study.
Absolutely. Joe of course has been one of the leaders in doing studies on the impacts of early life exposure to arsenic as well as adult exposures. Until recently, much of his work has focused on what’s going on in Bangladesh. He recently started looking at schoolchildren in Maine. Well water does not have to meet the same kind of standards as municipal water supplies. Joe looked at schoolchildren who were using well water and divided the population into the well water exposures at levels below and above 5 parts per billion, which is far below the regulatory maximum contaminant level of 10 parts that EPA and WHO have set. He found that in children [who drank water with] greater than 5 parts per billion the IQ distribution was shifted compared to those who had less arsenic in their drinking water.
Was it surprising to see this kind of problem in the United States?
Those of us who are interested in arsenic are not surprised. We know there are many areas in our country where arsenic in the water is a problem. There are 15 million people in the U.S. who may be drinking water from wells with arsenic that exceeds the EPA’s regulatory levels. And there have been some studies that suggest in adult populations an increase in heart disease. But frankly there have not been many studies in the U.S. population looking for the effects. It’s often easier to look for effects that occur at higher concentrations. Joe’s research included a population in New England where you have elevated groundwater arsenic.
From an environmental health point of view, where is the safest place to live? Is there a rule of thumb about rural vs. urban areas?
No, there is no rule of thumb. There is growing evidence that living near a lot of traffic is not the best thing for your health because of agents related to air pollution. But every area may have its own issues.
I wonder if cities are becoming healthier places.
This is certainly the case with the reduction in cigarette smoking and the controls on secondhand smoke—for example in many indoor environments—that we know is good for our health. Some of the regulations on idling diesel buses and trucks are also good for our health. As far as our cities becoming healthier places, overall levels of obvious air pollution are down, but we are beginning to find that even at lower levels there are still health concerns.
It goes without saying that environmental health is a planetary issue. Some countries are facing problems far worse than ours, particularly in relation to air pollution. What role does the NIEHS play beyond our borders?
While all pollution is local, it’s also global. What China generates reaches our West Coast within four to five days and continues to travel across the country. One of the major crosscutting themes of NIEHS has to do with global health and health disparities. We are funding studies in more than 35 countries. We have just been designated a WHO Collaborating Center and are focusing on the issue of training and capacity-building in the less-developed world, and we’re looking at issues of climate change and indoor cookstoves, e-waste recycling, children’s health, and the developmental origins of human adult disease.
Some chemicals of concern like phthalates are not listed as ingredients in the products that contain them, yet they are ubiquitous in the environment. A related problem is that when one chemical is banned like with bisphenol A in sippy cups, its replacement might be just as harmful. Is it ever possible to protect ourselves by being vigilant consumers? When is regulation necessary?
Knowledge is power. Consumers would be able to make informed choices if they had the information available to them about what we know about certain chemicals and what is in our products. The removal of BPA from baby bottles and sippy cups was in many ways a response to the market basket pressure when health studies began to be reported that raised concerns. A big issue is whether we are moving down what’s often called the “chemical conveyer belt” where we go from one chemical to another chemical about which we know less and sometimes that chemical might turn out to be worse.