Around the world, large-scale biomonitoring programs have provided extensive information about human exposure to a large number of environmental chemicals. As these programs extend to look at vulnerable populations, including pregnant women, fetuses, and the elderly, our knowledge of the widespread distribution of many of these chemicals continues to climb. However, the mere presence of a chemical in humans is not necessarily cause for concern. What is concerning is the increasing number of epidemiological studies showing associations between the concentration of these chemicals in the general population and adverse health end points. Although high exposures following accidental or occupational exposures to endocrine disruptors, industrial chemicals, pesticides, and pharmaceuticals have shown striking effects, epidemiological studies suggest that low doses may also be unsafe, even for populations that are not typically considered “vulnerable.”
Making connections between the exposome and risk assessment is a difficult but important venture. Risk assessments typically examine the effects of high doses of administered chemicals to determine the lowest observed adverse effect levels (LOAELs) and no observed adverse effect levels (NOAELs); reference doses, which are assumed safe for human exposure, are then calculated from these doses using a number of safety factors. Thus, human exposures to thousands of environmental chemicals fall in the range of nonnegligible doses that are thought to be safe from a risk assessment perspective. Yet the ever-increasing data from human biomonitoring and epidemiological studies suggests otherwise: Low internal doses of endocrine disruptors found in typical human populations have been linked to obesity, infertility, neurobehavioral disorders, and immune dysfunction, among others.
Source:
Birnbaum LS 2012. Environmental Chemicals: Evaluating Low-Dose Effects. Environ Health Perspect 120:a143-a144. http://dx.doi.org/10.1289/ehp.1205179
http://ehp03.niehs.nih.gov/article/fetchArticle.action?articleURI=info:…
Linda S. Birnbaum, director of the NIEHS and the NTP, oversees a budget that funds multidisciplinary biomedical research programs and prevention and intervention efforts that encompass training, education, technology transfer, and community outreach. She recently received an honorary Doctor of Science from the University of Rochester, the distinguished alumna award from the University of Illinois, and was elected to the Institute of Medicine. She is the author of > 700 peer-reviewed publications, book chapters, abstracts, and reports. Birnbaum received her M.S. and Ph.D. in microbiology from the University of Illinois, Urbana. A board-certified toxicologist, she has served as a federal scientist for 31 years, 19 with the U.S. EPA Office of Research and Development, preceded by 10 years at the NIEHS as a senior staff fellow, a principal investigator, a research microbiologist, and a group leader for the institute’s Chemical Disposition Group.
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