Risk Criteria For Public Policy

The use of Quantitative Risk Assessment to evaluate the public safety for chemical plants and other hazardous installations depends on the establishment of criteria, expressed as probabilistic safety criteria. Criteria are proposed for individual risk and societal risk. For individual risk an annual probability of 1 in a million is suggested for ''de minimis'' risk and 1 in 10,000 for ''unacceptable'' risk, with risks in between subjected to a test of ''reasonable and practical'' risk control measures being in place. For societal risk criteria, ''de minimis'' risk is 1 in, a million for 10 fatalities per year and a -1 slope for the Frequency-Number (FN) curve. The unacceptable risk is an FN curve 100 times higher. The proposed criteria are supported by reference to other similar criteria in use in the world and by exploration of the critical issues in developing criteria. The paper also illustrates the use of the proposed criteria.