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adequately demonstrate adverse effect and dose-response relationships for general toxicological responses and for reproductive and developmental effects. Furthermore, there is a significant need for data that characterize human exposure or provide reasonable estimates based on the pattern of use of the agent. The essence of the evaluative process is that the interpretation of those data should reflect expert judgment, rather than acquiesce to the passive use of a repetitive series of default assumptions. A valuable adjunct to the evaluation of an exposure to an agent is the inclusion of a statement of what is known and the certainty with which it is known. That should lead to the identification of critical data needs that might stimulate investigations to yield useful information that will enhance certainty of judgment and better serve the U.S. Navy.

Weight of Evidence

With a weight-of-evidence approach that considers both toxicity and human exposure information, evaluators can determine whether human or experimental animal data can reasonably be used to predict reproductive or developmental effects in humans under particular conditions of exposure. The approach must distinguish those agents for which there is firm evidence about human risk potential, based on relevant data, from those for which the potential for human effects is uncertain or unlikely. It will aid in setting priorities and developing programs to protect personnel from undue exposure to toxic quantities of agents or from undue costs of unnecessary control measures.

Using a weight-of-evidence approach to communicate a judgment about human risk, taking into consideration exposure potential, should diminish reliance on the assumption that reproductive and developmental toxicity observed in animals predicts similar effects in humans. Because the evaluative process requires a judgment about human risk potential based on the weight of the evidence, its approach and its results will be useful to the Navy. That approach differs from several programs that assess carcinogenic potential, including the International Agency for Research on Cancer (IARC) monographs, which invoke “sufficiency of evidence” determinations for experimental data; the Science Advisory Panel for the California Proposition 65 listing pro-

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