The many adverse health effects caused by chronic arsenic exposure are a concern for the hundreds of millions of people worldwide whose drinking water contains elevated levels of this naturally occurring element. A new rodent study suggests arsenic may also contribute to immune suppression. In this podcast, Josh Hamilton describes the potential implications of this finding for human health, including the possibility that arsenic exposure could help explain why certain populations have been hit harder by pandemic novel H1N1 flu. Hamilton is the senior author of "Low-dose arsenic compromises the immune response to influenza A infection in vivo" [doi:10.1289/ehp.0900911] and a senior scientist at the Bay Paul Center for Comparative Molecular Biology and Evolution, part of the Marine Biological Laboratory in Woods Hole, Massachusetts.

Although childhood leukemia is the most common childhood cancer, little is known about its causes. Incidence of acute lymphocytic leukemia, the most common childhood leukemia, is highest in industrialized countries and rose significantly between 1975 and 2004, suggesting environmental agents may play some role. In this podcast, Mary H. Ward explores the idea that polychlorinated biphenyls (PCBs) could be one such agent. Ward is the lead author of "Residential exposure to polychlorinated biphenyls and organochlorine pesticides and risk of childhood leukemia" [EHP 117:1007-1013 (2009)] and a senior investigator in the Division of Cancer Epidemiology and Genetics at the National Cancer Institute in Bethesda, Maryland.

The global population is undergoing sweeping changes that are shifting the balance toward an older and more urbanized population that experiences more chronic disease and a greater gap between rich and poor. In this podcast, Kenneth Olden tells what these changes mean in terms of public health challenges and how he believes we must prepare to meet these challenges. Olden was director of the NIEHS and the National Toxicology Program from 1991 to 2005. He served as NIEHS director emeritus and continued his research activities at the institute until 2008, when he left to help establish a new school of public health at the Hunter College campus of the City University of New York.

Cities and states across the United States, as well as other nations abroad, are banning bisphenol A (BPA) due to concerns about adverse health effects of low doses of this widely used industrial compound, particularly among fetuses, infants, and young children. In this podcast, Retha Newbold describes the findings of one of the few studies to study long-term effects of prenatal exposure to BPA in mice. Newbold is a staff scientist/reproductive biologist in the NIEHS Toxicology Branch and the lead author of "Prenatal exposure to bisphenol A at environmentally relevant doses adversely affects the murine female reproductive tract later in life" [EHP 117:879-885 (2009)].

In 2005 Shanna Swan and colleagues published groundbreaking research [EHP 113:1056-1061 (2005)] linking mothers' phthalate levels with altered genital development in their baby sons. In the four years since the publication of this paper, which was EHP's 2009 Paper of the Year, how much more have we learned about the health effects of phthalates? In this podcast, Swan discusses the state of the science. Swan is a professor of obstetrics and gynecology and of environmental medicine at New York's University of Rochester School of Medicine and Dentistry, where she is also director of the Center for Reproductive Epidemiology.

Children are generally more vulnerable to environmental insults because their bodies are still developing, but just as early exposures can cause lifelong adverse effects, so can early interventions produce lifelong benefits. In this podcast, Frederica Perera discusses the potential long-term benefits of reducing children's exposures to combustion emissions by mitigating modern society's reliance on fossil fuels. Perera is director of the Columbia Center for Children's Environmental Health at the Mailman School of Public Health, at Columbia University in New York and the author of "Children are likely to suffer most from our fossil fuel addiction" [EHP 116:987-990 (2008)].

In 2004 Günter Oberdörster and colleagues published a seminal review on the emerging discipline of nanotoxicology, which was later selected as EHP's 2008 Paper of the Year [EHP 113:823-839 (2005)]. In this podcast, Oberdörster tells why nanomaterials are so different from their larger chemical counterparts and describes the growing use of these materials in consumer products. Oberdörster is a professor in the Department of Environmental Medicine at the University of Rochester, New York, and director of the University of Rochester Ultrafine Particle Center.

In January 2009 Linda Birnbaum took the reins as the new director of NIEHS and the National Toxicology Program. In this podcast, Birnbaum shares her thoughts on the challenges facing the NIEHS and how she sees the institute meeting those challenges. Prior to her appointment as NIEHS/NTP director, Birnbaum was director of the Experimental Toxicology Division of the National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency.

How do you visualize something you've never seen? That's the question facing policy makers who are charged with preparing for the potential public health effects of a warming climate. In this podcast, Kristie Ebi looks at various scenarios used to power models that predict effects of climate change. Ebi is the author of "Climate change, tropospheric ozone and particulate matter, and health impacts" [EHP 116:1449-1455 (2008)] and an independent consultant who has served on numerous scientific panels including the Intergovernmental Panel on Climate Change.