Endocrine Disruptors and Children's Health

Authors
Philip Landrigan, Anjali Garg, and Daniel B.J. Droller

Title
Assessing the effects of endocrine disruptors in the National Children's Study

Journal
Environmental Health Perspectives. 111:1678-82. 2003.

Endocrine disruptors (EDs) refer to a group of chemicals that have the capacity to alter endocrine homeostasis. These chemicals are thought to be able to alter feedback loops in the brain, pituitary, gonads, thyroid, decrease in semen quality, and induce congenital malformations of the reproductive tract. It has been suggested that children are more susceptible to toxic chemicals in the environment. The susceptibility of children may be affected by greater exposure to environmental chemicals than adults on a body weight basis due to their diet, environments they occupy, play behavior, and physical size. In some cases, children are less able to metabolize and excrete certain toxic chemicals compared with adults. Also children are undergoing rapid growth and development which may be disrupted by exposure to toxic chemicals.

The National Children's Study (NCS) is a very large prospective epidemiology study that will follow 100,000 children in all regions of the United States, from early pregnancy to 21 years of age (Berkowitz et al., 2001). The goals of the NCS are to evaluate the health effects and to provide evidence-based guidance on measurement and assessment of EDs exposure in children. The NCS examines the influences of early exposure on human development and child and adult health. Evidence from animal studies, wildlife population studies, in vitro, clinical and epidemiologic studies support the biological plausibility that exposure to EDs during development and childhood can cause adverse effects on development.

Presently, the literature does not permit a conclusion to be made concerning the association between exposure to environmental chemicals and adverse health effects in children for several important reasons. The paucity of information on level and timing of past exposure is an important limitation for studies related to potential human impacts of EDs exposure. Moreover, published studies have tended to be under powered and thus unable to draw conclusions that either support or disprove the hypothesis that exposure to endocrine toxicants is associated with adverse health outcomes. The NCS aims to address these limitations by the prospective design and measuring exposure to chemical during pregnancy until adulthood. Additionally, the NCS uses a large population of 100,000 children which increase the statistical power of study to investigate the possible links between EDs exposure and human health. The NCS will study the effect of EDs on endocrine, neurodevelopment, and reproductive system by using laboratory assessment of chemical exposure and genetic analysis. However, it is important to appreciate that, although this is an important and needed study, even with the large sample size in the NCS study conclusions may not be able to be made due to the rare occurrence of many developmental abnormalities. It is also a concern that exposures in the general population may be too low to produce adverse effects in sufficiently large enough numbers to be detected in the NCS. Furthermore, since chemicals with endocrine toxic activities continue to be discovered it is not clear that the planned residue analyses will capture the toxic agents that are mechanistically linked with the adverse outcomes of interest. Regardless, examination of genetic polymorphisms will allow assessment of interindividual differences in susceptibility to EDs. Hence, the strengths of NCS will be able to determine which of the measured EDs, at what doses, and what time in development may contribute to the genesis of health problems in children and adults. Overall, for assessment of the risk associated with exposure to EDs and identification of the short and long-term health effects, a study such as NCS is essential for decreasing the gap in our knowledge.