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Environmental Factor, October 2012

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Birnbaum talks science and strategy at Dioxin 2012

By Eddy Ball

Logo for 32nd International Symposium on Halogenated Persistent Organic Pollutants — Dioxin 2012
Linda Birnbaum, Ph.D.

One of Birnbaum’s important messages is that primary prevention is the best, and often the most cost-effective, way to promote public health. (Photo courtesy of University of Illinois)

NIEHS/NTP Director Linda Birnbaum, Ph.D., was one of nearly a thousand delegates attending Dioxin 2012, where she made three invited oral presentations and was lead researcher on four poster presentations.

The meeting, held Aug. 26-31 in Cairns, Queensland, Australia, attracted scientists from throughout the world to the 32nd International Symposium on Halogenated Persistent Organic Pollutants — Dioxin 2012, offering Birnbaum an international forum for raising awareness of NIEHS advances in the promotion of environmental public health.

The program covered a broad range of core topics on analytical and environmental chemistry, environmental and human toxicology, epidemiology, and exposure assessment, as well as regulation, risk assessment, and management. Focal points for the meeting were emerging contaminants, marine and ecotoxicology, and chemical regulation and policy.

Engaging the unique toxicology of endocrine disrupting chemicals

Birnbaum addressed an emerging paradigm for understanding the health effects of endocrine-active chemicals, such as the flame retardant chemicals she studies in her lab at NIEHS, in her first talk Aug. 27, “Endocrine disruptors: Where do we go from here?”

The presentation surveyed the increasing rates of diseases with a probable link to the environment and the many chemicals that scientists have shown to have effects on the endocrine system, triggering adverse effects on reproductive function, brain development, lung function, and other physiological properties that rely on proper development and optimal endocrine function in order to maintain health. Then, she introduced the concept of nonmonotonic dose response, the pattern seen in exposure to hormones and endocrine-active chemicals found virtually everywhere in the environment.

“Modern science around toxicology has moved beyond the simple dichotomy of toxic versus nontoxic, which implies that all substances can be harmful at high doses, and at some lower dose, no harm is done,” she explained. “A nonmonotonic relationship [in contrast] allows for decreases in the effect at some doses and increases at others.”

These effects can be long lasting, Birnbaum explained in the course of the talk. “Exposure to endocrine disruptors during development can result in profound changes in later life … by subtly altering the structure of the DNA molecules and chromosomes,” she said. “These changes can potentially affect gene expression for several generations. This is the relatively new science of epigenetics.”

The strategic plan — integrating toxicology and risk assessment

The next day, Birnbaum turned to the new NIEHS strategic plan with her talk on “Environmental health research at NIEHS: current priorities and plans for the future.” The presentation described the year-long process of creating the plan’s mission statement, addressed its vision, and discussed each of the 11 strategic goals.

Following her discussion of implementing the strategic plan, with its overall commitment to translating bench science into environmental public health, Birnbaum underscored the public health implications of environmental effects and the impressive return on investment that can be achieved through environmental interventions.

Pointing to a New England Journal of Medicine study published this summer, she told the audience, “Environmental interventions are generally more cost-effective than clinical interventions, such as medical care and vaccines, and such non-clinical person-directed interventions as personal exercise programs. … This [study] suggests that there may be many cost-effective environmental interventions that are not yet recognized and deserve more attention.”

Wrapping up — a personal perspective

Birnbaum was also one of six distinguished speakers featured in the “Plenary Series: State-of-the-Art and Future Challenges” session Aug. 31 that brought Dioxin 2012 to a close. Her talk surveyed the area of toxicology and health, with a presentation titled “Key recent achievements in toxicology and health: a personal perspective.”

The talk could easily have been subtitled “Lessons learned in the course of a three-decades career in toxicology,” as Birnbaum ranged across a number of areas where experience has caused her to question conventional wisdom and pat assumptions. Topics included health effects of concern, critical windows of sensitivity and susceptibility, effects of exposure to mixtures and low dose effects, and the role of lipid adjustment in moderating toxicity.

“We haven’t learned our lessons,” Birnbaum said, before she ended the presentation with a question that also served as a challenge. “Why are we still allowing persistent, bioaccumulative chemicals to enter the marketplace?”

Citations: Blum A, Babrauskas V, Birnbaum L. Replacements for pentaBDE flame retardant: Is there an improvement in fire safety or health impacts?

Schecter A, Lorber M, Guo Y, Wu Q, Yun SH, Kannan K, Miller J, Hommel M, Imran N, Hynan LS, Cheng D, Colacino J, Birnbaum LS. Phthalates and hexabromocyclododecane (HBDE) in U.S. Food.

Sanders JM, Knudsen GA, Birnbaum L. The disposition of beta-hexabromocyclododecane (HBCD) in mice.

Scott L, Mortimer D, Birnbaum L. Brominated flame retardants (BFRs) in food and food products and impact of dietary intake on body burden: policy implications for regulating BFRs in the U.S.

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