National Academies Press: OpenBook

Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam (1994)

Chapter: A: Information Gathering: Literature Searches

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Suggested Citation:"A: Information Gathering: Literature Searches." Institute of Medicine. 1994. Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam. Washington, DC: The National Academies Press. doi: 10.17226/2141.
×

Appendix A
Information Gathering: Literature Searches

The primary charge to this committee was to analyze the scientific and medical literature published on the health effects of herbicides used in Vietnam. The committee used the following methods to identify, collect, and disseminate the scientific and medical literature that formed the basis of its review.

COMPUTERIZED BIBLIOGRAPHIC DATA BASES

The initial focus of the committee's efforts was a comprehensive search of relevant computerized data bases. Sixteen data bases covering biomedical, toxicological, chemical, historical, and regulatory information were accessed utilizing Dialog, a commercial data base vendor, and the National Library of Medicine's (NLM's) Medical Literature Analysis and Retrieval System (MEDLARS). The majority of the data bases searched were bibliographic (Table A-1), providing citations to scientific literature. Factual data bases (Table A-2) were also searched to provide toxicological and chemical information.

To maximize retrieval, the search strategy incorporated the broad terms ''phenoxy herbicides" and "dioxin," specific chemical names (2,3,7,8-tetrachlorodibenzo-p-dioxin; 2,4-dichlorophenoxyacetic acid; 2,4,5-trichlorophenoxyacetic acid; dimethylarsinic acid; 4-amino-3,5,6-trichloropicolinic acid), abbreviations (TCDD; 2,4-D; 2,4,5-T), and synonyms (Agent Orange, picloram, cacodylic acid). The search term "herbicides/adverse effects" was also used to increase the comprehensive retrieval of the search. Accuracy

Suggested Citation:"A: Information Gathering: Literature Searches." Institute of Medicine. 1994. Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam. Washington, DC: The National Academies Press. doi: 10.17226/2141.
×

TABLE A-1 Bibliographic Data Bases Searched

Biosis

Books in Print

Cancer Lit

Conference Papers Index

Dissertations Abstract

Embase

Enviroline

Environmental Bibliography

Federal Register

Medline

National Institute for Occupational Safety and Health

National Technical Information Service (NTIS)

Pascal

Psych Info

Toxline

World Translations Index

was enhanced in applicable data bases by using Chemical Abstracts Service Registry Numbers, which uniquely identify each individual chemical. Individual searches were customized to reflect the structure of each data base. For MEDLARS data bases, searching was done on the standardized terminology and alphanumeric designators for each chemical found in NLM's Medical Subject Headings (MeSH) and the MeSH tree structures.

Although there is subject and content overlap, each data base serves a unique function, has a distinct subject emphasis, and indexes literature not available elsewhere. To serve the comprehensive goals of this study, it was decided to search all relevant data bases in their entirety for epidemiologic studies, case reports, and secondary literature (reviews, letters, news articles, etc.). The animal toxicology literature on this subject is extensive, and these studies build on and reference previous work. The committee decided to retrieve all animal toxicology citations from 1980 through the present.

Throughout the study, searches were updated, and targeted searches were done on specific topics such as porphyria cutanea tarda.

TABLE A-2 Factual Data Bases Searched

Chemical Carcinogenesis Research Information System

Developmental and Reproductive Toxicology

Hazardous Substances Data Bank

Integrated Risk Information System

Registry of Toxic Effects of Chemical Substances

Suggested Citation:"A: Information Gathering: Literature Searches." Institute of Medicine. 1994. Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam. Washington, DC: The National Academies Press. doi: 10.17226/2141.
×

OTHER SOURCES

Committee staff examined the reference lists of major review articles, books, and reports for relevant citations. Reference lists of individual articles were also scanned for additional relevant references.

Literature identification was an ongoing process throughout the study. A valuable source of additional information was the input received both in written and in oral form from veterans, interested persons, and speakers at the public hearings and scientific workshops (see Appendix B).

LITERATURE DISSEMINATION

All retrieved citations were entered into the study's bibliographic data base, which at the conclusion of the study contained 6,420 references to the health effects of the herbicides used in Vietnam. Given the large number of documents on this topic, it was necessary to determine a method that would organize the material most effectively and serve as a tool in dissemination of the literature to the appropriate committee members. A list of 41 terms was developed for indexing individual articles. Each epidemiologic study was categorized by the population group exposed (occupational, environmental, veteran, Vietnamese) and the general health outcome. Toxicology references were subcategorized by main topic (e.g., mechanism of action, chemistry, pharmacology, genotoxicity). Updated subject bibliographies were distributed to the committee throughout the study to reflect additions to the bibliographic data base. Copies of papers were requested as needed for the committee's information and analysis.

EPIDEMIOLOGIC STUDIES

At its first meeting, the committee realized that the epidemiologic studies would be a primary source of information for determining associations between individual health outcomes and exposure to herbicides. It was decided that a more detailed approach was necessary in indexing and critiquing these studies, and the committee developed an abstracting form. Information on the form began with descriptions of the study and comparison populations and of the study design. Exposure to herbicides was categorized through source, validation methods, exposure definition, and length of exposure. The form detailed the major health outcome categories, listing cancers by type and site; specific adverse reproductive outcomes; subcategories of neurobehavioral, cardiovascular, respiratory, metabolic, immunologic, and dermatologic disorders; and other health effects. The study's analytical methods were detailed on the form with information including confounding factors, methods used to control confounding, and consideration for latency.

Suggested Citation:"A: Information Gathering: Literature Searches." Institute of Medicine. 1994. Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam. Washington, DC: The National Academies Press. doi: 10.17226/2141.
×

Each epidemiologic study was abstracted by consultants to the committee, and the abstracted data for each study were entered into a computerized data base. The first use of this data base was to sort the studies by health outcome. Completed abstracting forms and studies were then sent to committee members with expertise in that field, who reviewed and verified the abstracted information. Throughout the study, this data base was used extensively to aid committee members in locating relevant studies on a variety of questions ranging from methods of exposure assessment to study design.

Suggested Citation:"A: Information Gathering: Literature Searches." Institute of Medicine. 1994. Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam. Washington, DC: The National Academies Press. doi: 10.17226/2141.
×
Page 735
Suggested Citation:"A: Information Gathering: Literature Searches." Institute of Medicine. 1994. Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam. Washington, DC: The National Academies Press. doi: 10.17226/2141.
×
Page 736
Suggested Citation:"A: Information Gathering: Literature Searches." Institute of Medicine. 1994. Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam. Washington, DC: The National Academies Press. doi: 10.17226/2141.
×
Page 737
Suggested Citation:"A: Information Gathering: Literature Searches." Institute of Medicine. 1994. Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam. Washington, DC: The National Academies Press. doi: 10.17226/2141.
×
Page 738
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Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam Get This Book
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Have U.S. military personnel experienced health problems from being exposed to Agent Orange, its dioxin contaminants, and other herbicides used in Vietnam? This definitive volume summarizes the strength of the evidence associating exposure during Vietnam service with cancer and other health effects and presents conclusions from an expert panel.

Veterans and Agent Orange provides a historical review of the issue, examines studies of populations, in addition to Vietnam veterans, environmentally and occupationally exposed to herbicides and dioxin, and discusses problems in study methodology. The core of the book presents

  • What is known about the toxicology of the herbicides used in greatest quantities in Vietnam.
  • What is known about assessing exposure to herbicides and dioxin.
  • What can be determined from the wide range of epidemiological studies conducted by different authorities.
  • What is known about the relationship between exposure to herbicides and dioxin, and cancer, reproductive effects, neurobehavioral disorders, and other health effects.

The book describes research areas of continuing concern and offers recommendations for further research on the health effects of Agent Orange exposure among Vietnam veterans.

This volume will be critically important to both policymakers and physicians in the federal government, Vietnam veterans and their families, veterans organizations, researchers, and health professionals.

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