Environmental Factor, January 2011, National Institute of Environmental Health Sciences
Birnbaum presents Whittenberger Symposium keynote lecture
Birnbaum has spent much of her two years as director representing NIEHS at conferences, symposia, community meetings, and congressional hearings. (Photo courtesy of Steve McCaw)
NIEHS/NTP Director Linda Birnbaum, Ph.D., added yet another laurel to her long list of honors, when she presented the keynote talk at the 13th James L. Whittenberger Symposium Dec. 17 at the Harvard University School of Public Health (HSPH). Introduced by NIEHS grantee Douglas Dockery, Sc.D., Birnbaum delivered a lecture on "Continuing Vulnerability: Adolescence and the Reproductive Years."
Held each year to honor the contributions of former Harvard University Professor James Whittenberger, M.D., to the field of environmental health, the seminars are sponsored by the Department of Environmental Health and the Harvard NIEHS Center for Environmental Health at the Harvard School of Public Health. Until his retirement in 1982, for 36 years, Whittenberger served the HSPH in a variety of capacities, including as founder and director of the Harvard NIEHS Center for Environmental Health.
Like the 12 previous Whittenberger lecturers (see text box), Birnbaum addressed an emerging and important topic in the field of environmental public health. She pointed to several diseases and conditions that have increased over the past 40 years, including testicular cancer, birth defects, some childhood cancers, asthma, difficulty conceiving and maintaining pregnancy, prematurity, pre-eclampsia, gestational diabetes, autism, and attention deficit hyperactivity disorder.
Emphasizing the importance of the total environment in the rising incidence of these diseases, Birnbaum said, "We know the human genome hasn't changed over that time, so a genetic cause is unlikely." However, she noted, environmental factors - chemicals, diet and nutrition, drugs, stress, climate, infections, and other factors - have changed dramatically over the past decades.
As with exposure to developmental stressors during gestation and childhood, Birnbaum continued, exposures during the sensitive adolescent and reproductive periods can trigger epigenetic alterations that lead to disease, as people move into middle life and later life. "During development, environmental stressors cause functional changes, such as altered gene expression, altered protein activity, and/or altered number of cells," she explained, "and these functional changes persist after the environmental stress is gone."
From the role epigenetic marks play in later development of disease, Birnbaum moved into several other areas where NIH and NIEHS research has started to shed light on disease progression through gene and environment interactions. Noting the involvement of three important chemical classes - phenols, phthalates, and phytoestrogens - in the decreasing age of puberty, Birnbaum connected them with increases in body mass index and the rate of breast and pubic hair development.
Birnbaum also noted studies of glucocorticoid receptor (GR) gene expression that have provided insights into the long-term effects of maternal behavior on offspring. "From studies looking at GR methylation and suicide," she said, "we see a clear connection to a history of childhood abuse, and specific effects in certain areas of the brain of suicide victims."
After discussing epigenetics and asthma, Birnbaum turned to NIEHS- and NIH-funded research programs on neurodevelopment and breast cancer - complex diseases influenced by a matrix of environmental exposures, such as chemical exposure, diet, and ionizing radiation, during sensitive periods of development. She concluded by reinforcing the central concepts that are the foundation for the gene-environment interaction paradigm to explain the increase of disease.
Previous lectures in the James L. Whittenberger Symposium series
- 1984 Norton Nelson, Ph.D., "Airborne Particles: Poisons, Probes, and Prophylactics"
- 1986 Ian Higgins, M.D., "Environmental Epidemiology: Dose Response"
- 1987 Bernard Goldstein, M.D., "Topics in Ozone Toxicity"
- 1988 David Bates, M.D., "Ozone - Myth and Reality"
- 1989 Margaret Becklake, M.D., "Industrialization: A Challenge to the Lung"
- 1992 John M. Peters, M.D., "Environmental Factors and Childhood Leukemia"
- 1994 Symposium on Respiratory Physiology and Environmental Health in Honor of James L. Whittenberger's 80th Birthday
- 1997 Jonathan Samet, M.D., "Radon"
- 1999 Scott Weiss, M.D., "The Asthma Epidemic: Is It Due to Genes, the Environment, or Both?"
- 2007 David Schwartz, M.D., "Epigenetics and Environmental Asthma"
- 2008 David Barker, M.D., Ph.D., "Nutrition in the Womb: The Origins of Chronic Disease"
- 2009 Philip J. Landrigan, M.D., "The Unique Vulnerability of the Developing Human Brain to Toxic Chemicals in the Environment"