Of the approximately 800 studies reviewed in detail for this report, most involved individuals who were exposed to these agents in occupational settings over long periods of time. Only a small number actually studied veterans who may have been exposed while serving in the Persian Gulf. The committee carefully assessed the quality, limitations, and relevance of each epidemiologic study, and used five categories to describe the strength of the evidence.
SUFFICIENT EVIDENCE OF A CAUSAL RELATIONSHIP, the strongest level of evidence, means that many studies have established a clear link between exposure to an agent and a health outcome. Among the other requirements, there must be a plausible biological explanation for the relationship. None of the compounds evaluated in this report met these criteria.
Evidence that establishes a link between exposures and a health outcome with reasonable certainty, but fails to meet the higher standard of proof needed for causality, is characterized as SUFFICIENT EVIDENCE OF AN ASSOCIATION. The evidence for an association between lung cancer and combustion products falls into this
Contact: Christine Stencel or Chris Dobbins
The National Academies