measures. Where surrogate measures are used, however, it is especially important to
identify and document the differences between such measures and the decision
objectives they represent.
Guideline 2.4-- Risk Measures. Risk measures should account for relevant
parameters critical to distinguishing between decision options. To accomplish this,
the following parameters should be considered:
a. Relevant hazards and contingent outcomes.
b. Likelihood of occurrence and severity of consequences.
c. Timing and duration.
a. Relevant Hazards. Risk measures should consider relevant hazards or contingent
outcomes associated with the decision options. The following list indicates some
typical risk measures considered by RBP systems-- risk measures may be added
or removed as determined by the end-user objective:
1. Public health and safety (i.e., acute and chronic risks, including cancer risks).
2. Worker health and safety.
3. Environmental impacts.
4. Security and safeguards.
5. Regulatory risks.
6. Implications for and risks to public assessment/perception.
7. Implications for and risks to science and technology capabilities.
8. Implications for and risks to science and technology scope/mission.
In addition to considering the full population at risk, attention should be directed to
subpopulations (including future generations) that may be particularly susceptible
to such risks and/or may be more highly exposed.
b. Likelihood and Severity. Risk measures sensitive to likelihood and severity may
be needed to properly distinguish high risks from low risks. Generally, risk is the
likelihood of an adverse event with respect to impact on a decision objective and
the consequence of that event. The risk of an adverse event may be high
because (1) the likelihood of the event's occurrence is very high, (2) the
consequence of the event is very high, or (3) both likelihood and consequence are
c. Timing and Duration. Several issues pertaining to risk timing and duration may be
important in distinguishing between decision options. First, some decision options
may be viable only when implemented within a limited time window; in contrast,
other decision options may be implemented at any time. For example, a decision
option intended to limit the spread of contamination into an aquifer may be
technically much simpler if it is quickly implemented; thus, a potentially limited
window of opportunity exists before the nature and magnitude of the risk
associated with the decision option is fundamentally changed. Second,
performance measures should distinguish between (1) decision options that