The information used by the committee was developed through a comprehensive search of the literature. The search used public and commercial databases that cover biologic, medical, toxicologic, chemical, and regulatory information; most of the databases are bibliographic and provide citations to the scientific literature. The references of major review and research articles, books, and reports were also examined.
The specific compounds identified in the literature were divided into three main categories: combustion products, fuels, and hydrazine and nitric acid. The Committee advised staff in identifying appropriate synonyms, Chemical Abstracts Service registry numbers, and additional, related terms. Terms were compared with the controlled vocabularies of the databases to be searched, and database-specific terms were used as search terms. In April 2003 three searches were performed—one for each of the main categories.
The searches were conducted in two major biomedical electronic databases: MEDLINE and EMBASE. MEDLINE, produced by the National Library of Medicine (NLM), indexes 4,600 biomedical journals and contains about 11 million citations. The database covers entries from 1966 to the present. EMBASE, based on the Excerpta Medica database, is produced by Elsevier Science and indexes over 4,000 international journals covering such fields as drug research, toxicology, clinical and experimental human medicine, public health, and occupational health. It covers entries from 1974 to the present. EMBASE has more of an international focus than does MEDLINE. EMBASE contains more than 9 million records and adds about 450,000 records each year. Staff also searched the publication lists of the International Agency for Research on Cancer and the Agency for Toxic Substances and Disease Registry for reference material pertinent to the substances to be examined. In addition, the reference lists of review articles were examined for related citations. Results of searching these various sources were imported into ProCite, a software program designed to store and manage bibliographic data.
This original ProCite database consisted of about 33,000 records. The titles and abstracts of those records were reviewed by staff and committee members, and the citations deemed relevant for the study were copied into a “working” ProCite database, which consisted of about 8,500 records. The working database consisted mostly of epidemiologic studies but also contained case reports, series papers, background documents, and references to pertinent toxicologic sources.
Additional searching in PubMed explored various specific subjects that might be relevant to this study. Literature searches were performed in PubMed for hydrocarbons and for “Gulf War” by using many synonyms and related terms. The combined toxicologic information and environmental-health database called Toxnet and found on the NLM web site was used to search for toxicologic literature related to the three main categories.