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TRACKING DOWN REPRODUCTIVE HEALTH RISKS FOR HUMANS EXPOSED TO ENVIRONMENTAL CONTAMINANTS
Citation:
Darney, S P. TRACKING DOWN REPRODUCTIVE HEALTH RISKS FOR HUMANS EXPOSED TO ENVIRONMENTAL CONTAMINANTS. Presented at Society for the Study of Reproduction, Cincinnati, OH, July 19-22, 2003.
Description:
Government agencies charged with protecting public health are concerned about the same things you are: being able to conceive and deliver healthy babies, and watching them grow up to be strong, disease-free adults capable of having their own children. The rules that governments promulgate to ensure that the products we use, the food we eat, and the air and water we enjoy are safe depend for their effectiveness on the quality of science upon which they are based. Current concerns include the extent to which environmental contaminants might impair either reproductive development during fetal life or reproductive function in adulthood. Compounds that mimic hormones or alter their activity, such as certain dioxins, PCBs, and plastics, are of particular concern, as are specific pesticides, chemical byproducts resulting from the disinfection of drinking water, and components of air pollution derived from the combustion of fossil fuels. In laboratory test species such as the rat, individual chemicals can be tested under controlled conditions to identify the dose-response relationships, target organs/tissues and cells, and detailed mechanisms of toxicant action. This information is then used to set exposure limits for humans. However, in the real world, humans are exposed to complex and ever changing mixtures of potential toxicants. It can be difficult to distinguish adverse effects related to inadvertent chemical exposures from those arising from intentional exposures such as cigarette smoke, alcohol, or pharmaceuticals, or from genetic variation, or the consequences of infectious diseases. To make such distinctions requires the conduct of carefully designed studies in which exposures are well characterized, confounders are identified, and sensitive disease indicators are measured in a sufficiently large sample of people. EPA has recently conducted a series of studies in collaboration with scientists from the Czech Republic to examine the impact of intermittent exposure to high levels of air pollution (at or exceeding current U.S. air quality standards) on male reproductive health. These studies provided the first evidence for an association between such exposures and adverse effects on sperm morphology and genomic integrity. Importantly, while these effects are likely transient, each sperm affected could potentially transmit the genetic damage to the conceptus, resulting in early pregnancy loss or other adverse developmental outcomes. Another project, The Healthy Men Study, conducted by EPA in partnership with epidemiologists at UNC-Chapel Hill, is evaluating potential effects of disinfection byproducts (DBPs) in drinking water on human semen quality. This DBP study is focused on the brominated acetic acids which have been shown to affect spermatogenesis in rodents. Volunteers from three geographically diverse municipalities that differ in DBP levels will participate by completing a health and exposure history via telephone interview and then mailing a semen sample to the EPA laboratory for analysis. We expect that this approach will encourage participation and allow us to measure both genomic and proteomic indicators of sperm quality. While these studies draw attention to male reproductive health, a variety of human studies underway in many countries around the world are addressing related questions about environmental exposures and adverse effects on fertility, pregnancy outcomes and reproductive tract cancers.