Are all distributions of risk with the same 95^thpercentile equally acceptable?

Abstract

When evaluating a probabilistic health risk assessment, say at a hazardous waste site, risk managers need a risk management policy that distinguishes an acceptable distribution of risks to individuals in a population from an unacceptable one. If a risk manager decides that the distribution of risk for the status quo is unacceptable, then a risk assessor needs a way to compute cleanup targets, i.e., the risk assessor needs a policy statement against which to estimate distributions of exposure point concentrations which, if engineered at a site, will achieve an acceptable distribution of risk. Some regulatory agencies base acceptability on whether the 95^th percentile of the risk distribution falls at or below a given value, without considering the behavior of the rest of the distribution. As regulatory agencies adopt risk management policies for use with probabilistic risk assessments, we recommend that they base their new policies on two simultaneously binding constraints‐one on an upper percentile and one on the arithmetic mean of the distribution of risk‐in addition to other non‐risk criteria.

Key words:

• acceptable risk
• risk distribution
• risk management
• Monte Carlo

Notes

Alceon Corporation, PO Box 382669, Harvard Square Station, Cambridge, MA 02238–2669; TEL: [phone]; FAX: [phone]; e‐mail: [email protected].

Environ Corporation, 214 Carnegie Center, Princeton, NJ 08540.

Additional information

Notes on contributors

Eristen G. Edelmann

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