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The purpose of this work was to develop a document that provides general guidance on how to access and use NHANES data to provide useful information for EPA risk assessment and policy needs. The Guidance was designed for EPA researchers and managers to give them ideas on how to use NHANES data in research and to support policy. It also discusses the major problems and limitations of the NHANES data and how the data can be linked to other databases (e.g., exposure data) in order to increase the usefulness of the NHANES data.

Project Status

The draft Handbook was completed in the spring of 2002 and peer reviewed. The final version was released to the public via the NCEA web page in May 2003

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The National Center for Health Statistics (NCHS) has been sponsoring National Health and Nutrition Examination Surveys (NHANES) since 1971. There have been four completed surveys, with the last one (NHANES-III) being conducted from 1988-1994, and involving over 40,000 subjects. Starting in 1999 NHANES is now in the field continuously. NHANES is designed to assess the health and nutritional status of a statistically representative sample of the civilian, non-institutionalized population of the continental US. The survey includes extensive questionnaires and standardized physical examinations, including urine and blood analyses conducted in specially equipped mobile examination centers that travel around the country. Historically only a limited part of the NHANES data have been used in research or to support policy decisions in EPA. Most notably, previous NHANES have measured blood lead levels in children and adults and provided valuable information on exposures to this environmental toxicant. Previous NHANES surveys have also provided important information on pesticide exposures, respiratory and cardiovascular health, tobacco use, and dietary consumption of numerous food items. NHANES surveys have the following research and public health goals that are highly relevant to EPA needs: 1) estimation of the prevalence of diseases and risk factors, including many environmental risk factors; 2) estimation of disease incidence; 3) development of population reference distributions of health parameters such as growth and development; 4) monitoring of secular changes in disease and risk factors; 5) identification of causes of secular changes in health status; and 6) identification of new risk factors for diseases and their contribution to the understanding of disease etiology.

NHANES provides a wealth of human data collected over the past 25 years, yet most of these data have not been adequately evaluated for their usefulness to EPA. Many, if not most, scientists in EPA are either not aware of NHANES or not aware of the content and potential usefulness of the data to support risk assessment and policy needs of the Agency. For these reasons, the Handbook was developed to make EPA scientist aware of the existence and content of this database and provide them with information on how to access and use NHANES data in research and risk assessment. The Guidance includes: 1) information about the history, purpose and content of NHANES, with emphasis on elements of interest to environmental health issues; 2) a compendium of abstracts of current EPA studies using NHANES data; 3) suggestions for analyzing data at national, regional, and urban vs rural scales; 4) discussion of major limitations to use of NHANES data (i.e., can't perform local studies; issues of confidentiality) and some precautions on use and interpretation of study results. The audience for this Handbook is assumed to be composed of epidemiologists and statisticians familiar with appropriate research methods and how to interpret the findings, but unfamiliar with the purpose, content, limitations and potential usefulness of NHANES for supporting Agency risk assessment and policy needs. The Handbook provide descriptions of studies in which EPA staff have used NHANES data to study various environmental health issues (i.e., NCEA children's respiratory study, NCEA puberty study, OPPTS pesticide study). The Handbook is designed for EPA researchers and management to give them ideas on how to use NHANES data in research and to support policy and regulatory needs. It should also alert researchers to some of the major problems and limitations of the NHANES data and how the data can be linked to other databases in order to increase the usefulness of the NHANES data.

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