David Dorman is a professor of veterinary toxicology at NC State. He recently served on a committee for the National Academy of Sciences (NAS) assigned to provide strategies to the Environmental Protection Agency (EPA) for evaluating low-dose effects of endocrine-active chemicals on human health. On July 18, the committee delivered its report and recommendations to the EPA. Dorman has agreed to do a Q&A with the Abstract to talk about the report and its findings.
The Abstract: Tell us a little more about the committee and its charge. What were the chemicals you looked at, and why were they chosen?
Dorman: The EPA wants to improve its overall strategy for determining low-dose chemical effects, particularly in regards to endocrine-active chemicals. They wanted the National Academies to evaluate human and animal evidence for low-dose effects from two chemicals, and show how you could integrate animal and human data. The committee could choose any two endocrine-active chemicals – we chose to look at phthalates and a class of flame retardant chemicals (PBDEs) because we have human epidemiological and animal toxicity data for both.
TA: You recommended the use of systematic review as a way to monitor the effects of these chemicals. What is a systematic review, and why is it a useful strategy?
Dorman: With a systematic review we formulate a question – in one case it was, “Does in-utero exposure to phthalates result in male reproductive effects in humans or animals?” Then we extract literature that addresses that question and analyze the body of evidence, looking for consistency across a group of studies to draw conclusions about what the evidence is showing. It is useful because it allows us to see what the literature is actually telling us, without cherry-picking studies. In the end you can say that overall, the evidence is pointing in a particular direction. The committee was able to illustrate how systematic reviews can be performed. We also demonstrated to the EPA a path forward for them to use existing systematic reviews.
TA: Were there any other important findings?
Dorman: Another thing we showed was that animal data has a predictive value for outcomes of concern, but they did not predict exposures that could result in effects in people. For example, phthalates were shown to affect male reproductive endpoints in exposed mice and rats, in controlled conditions. Human epidemiologists looked at those same endpoints in boys and in some cases identified the same effects, but there isn’t direct data about how much the children were exposed to. So we recommended that more studies should be developed to help bridge animal and human studies so we can better interpret the data.
TA: You’ve served on a number of these committees. What makes this work meaningful for you?
Dorman: The NAS serves as a trusted advisor to the government and it’s important for the public to have someone they can trust. I’m heavily invested because I want to see good decisions being made by government and I want to protect public health, and this is a powerful mechanism by which I can help influence and shape decision making.