these gray-literature studies may include such items as state health-department reports, doctoral and master's theses, and reports produced by special-interest groups. In addition, the committee is aware that, with the dramatic changes in government in the former Union of Soviet Socialist Republics, large amounts of information on environmental health in that region are becoming available. Most of these reports are in the gray literature and even in that form have not appeared in the English-language literature.

Review of Gray Literature

Why is the gray literature gray? Many studies with substantial implications for environmental epidemiology are never published. A part of the problem is that in the United States and some other countries, the assessment of environmental health effects is often conducted in a context of litigation or potential regulatory action. This climate exerts strong pressures on any scientific assessment that may affect the selection of specific topics for study, protocol design, and methods of analysis, as well as public availability (e.g., sealing of records as a part of a negotiated settlement).

Earlier, the committee discussed some of the limitations that may confront public-health agencies in performing environmental-epidemiologic studies, including limited expertise, limited resources, lack of concern, secrecy of data, political pressure to conduct studies despite inadequate knowledge about the exposures or diseases in question, and the inherent limitations of uncontrolled "natural" experiments in which the populations are too small, the latent period too short, or the exposures or outcomes too poorly defined to yield useful results. In addition, there may be an issue of "publication bias" in which well-designed and well-conducted studies are not published, because of a lack of interest by journals or because of a bias against publishing negative findings in some instances and positive findings in others, especially when the "exposure'' is not of great current interest among other scientists. Agencies may have little motivation for assembling studies into a format suitable for publication as staff move from fighting one fire to another. To understand better the question of why the gray literature is not published, the committee undertook to obtain a collection of such studies that had been produced by state health departments and others. Defined criteria were used to assess the quality, strengths, and weaknesses of each study and to estimate whether each report would be publishable in the peer-reviewed literature.

NGA-ATSDR State Environmental Health Information Clearinghouse

The National Governors' Association (NGA) under contract with the Agency for Toxic Substances and Disease Registry (ATSDR) initiated a

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