physical structures” (OMB 2006, p. 7), and it is clearly intended to cover such assessments. Despite these introductory statements, the bulletin focuses mainly on biologic systems, with an emphasis on human health risk assessment, and provides little guidance related to physical (engineered) systems.

In fact, the bulletin gives only minimal attention to risk assessments for which the end point is major failure of an engineered system. The vast majority of examples presented (and authorities cited) apply to toxicologic and other human health end points without corresponding attention to the failure of engineered systems. Moreover, it is unclear whether the bulletin’s occasional mention of such failures refers mainly to human health consequences (for example, death or injury from a nuclear power plant accident) or includes the probability and consequences of the engineered failure itself (for example, bridge collapse or toxic release from a chemical plant without estimating the extent of related human health effects).

The bulletin fails to take advantage of the concepts and methods developed through the engineering community’s investment of hundreds of millions of dollars in quantitative risk assessment for physical systems. Specifically, in referencing the risk studies, the bulletin is deficient in not recognizing the extensive and often effective efforts of the private sector in risk assessment of such subjects as off-shore oil platforms, chemical plants, nuclear reactors, and waste sites. Those studies have influenced positively risk assessment in the federal government. The incomplete and unbalanced approach to engineering risk assessment (as well as ecologic and other types of risk assessment) belies the bulletin’s stated objective of improving the quality of risk assessment across the federal government.

SENSITIVE SUBPOPULATIONS

The bulletin has multiple standards and requirements related to “populations” and “subpopulations” (OMB 2006, Section IV[2], V[6]), but these standards are incomplete in relation to sensitive subpopulations. Specifically, the only reference to sensitive subpopulations, such as “children or the elderly,” appears not in the bulletin, but in the supplementary information (OMB 2006, p. 19). Moreover, the strong emphasis on central estimates in the standards themselves means that the most vulnerable people in a population—who, almost by definition, lie in the tails



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