insecticide and solvent terms but also other spelling variations, synonyms, and commercial names. Thus, a series of search strategies were developed to take advantage of the classification scheme, controlled vocabulary, and distinct structure of each database.

In addition to the complexities presented by the databases, the literature on the insecticides and solvents being reviewed in this study afforded its own set of challenges as committee members and staff worked to identify the pertinent literature comprehensively while minimizing the retrieval of nonrelevant citations. For instance, ethylene glycol and butyl acetate, two solvents under study, are referred to in numerous articles that describe laboratory procedures but not human health effects. Searching for the solvent ethanol was confounded by the retrieval of numerous articles on alcoholism. Similarly, many efficacy and treatment-related studies, such as those of the effectiveness of various insecticides on mosquito nets or evaluating treatment options for head lice, were retrieved by a search for malathion and permethrin. It is not always possible to design a comprehensive search strategy that retrieves the citations needed for the committee’s purposes but eliminates all citations that are not useful to the committee.

The search for insecticides included the 11 insecticides listed in the congressional legislation and three additional insecticides (d-phenothrin, azamethiphos, and bendiocarb) identified by the Office of the Special Assistant for Gulf War Illnesses as having been used by military personnel during the Gulf War. The search for solvents included the 53 specific solvents that were sent to the Gulf War as determined by the Department of Defense’s Defense Logistics Agency.

Although the search strategies varied somewhat with their purpose and the structure of the databases being searched, the foundation of every major search contained the same basic elements: specific insecticides and solvents, their synonyms, alternative spellings, trade names, CAS registry numbers, insecticide and solvent classes (such as organophosphates, carbamates, acetates, and glycols), and the general terms pesticides, insecticides, and solvents. All databases were searched in their entirety, and all foreign-language citations were retained; any studies that the committee deemed significant were translated into English.

Because the focus of the committee’s work was to review the literature regarding the human health effects of insecticide and solvent exposure, the primary searches used the comprehensive search strategy discussed above and then limited the retrieval to human studies. For some database searches, terms like adverse effects, epidemiologic study, controlled study, and cohort were added to the search strategies. Nearly 30,000 citations were initially identified and reviewed for their relevance to the committee. However, as discussed above, because of the attempt to be as comprehensive as possible, the search strategies retrieved many references that were not relevant for the committee’s purposes.

A second goal of the literature search was to provide the committee with a broad overview of the toxicology of insecticides and solvents so that it could assess biologic plausibility. Textbooks and reports, such as the Agency for Toxic Substances and Disease Registry (ATSDR) Toxicological Profiles, provided much of the background material, but online bibliographic databases were used to identify the current literature and review articles.

Throughout the study, smaller targeted searches were conducted on specific topics, such as insecticide and solvent interactions, occupational exposures, and inert ingredients found in insecticide and solvent formulations. The secondary searches were especially

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