When a limited number of studies suggest that a link exists, but without reasonable certainty, the evidence is said to be LIMITED OR SUGGESTIVE OF AN ASSOCIATION. This category describes the evidence for links between combustion products and nasal, oral, laryngeal, and bladder cancers; asthma; and low birth weight and preterm births by women exposed while pregnant. Likewise, the evidence for an association between hydrazine exposure and lung cancer fits this definition.

If several studies of adequate quality consistently fail to show a positive association at any level of exposure, the evidence is described as LIMITED OR SUGGESTIVE OF NO ASSOCIATION. And evidence that lacks sufficient quality, consistency, or statistical power to draw any conclusion is judged to be INADEQUATE OR INSUFFICIENT TO DETERMINE WHETHER AN ASSOCIATION EXISTS. The majority of the evidence on fuels, combustion products, and propellants falls into this final category.

The study was sponsored by the U.S. Department of Veterans Affairs. The Institute of Medicine is a private, nonprofit institution that provides health policy advice under a congressional charter granted to the National Academy of Sciences. A committee roster follows.

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The National Academies
20-Dec-2004