Numerical risk tolerance criteria in the United States: A critique of the risk criterion used for the New Jersey Toxic Catastrophe Prevention Act

Numerical risk tolerance criteria are used around the world in the management of process safety, although federal process safety regulations in the United States do not currently employ such criteria. However, increasingly individual companies are employing numerical criteria motivated by industry practices and standards. Often, precedents are sought in setting criteria. One precedent is the first process safety regulation that was enacted in the United States in the state of New Jersey under the Toxic Catastrophe Prevention Act (TCPA). The regulation that implements the TCPA contains a numerical risk criterion. Companies covered by the regulation must demonstrate through analysis that they comply with the criterion. Unfortunately, the criterion and the procedure for using it are seriously flawed and they should not be used as a precedent by companies or other regulators. This paper identifies various problems with the criterion and describes how to overcome them in order to explain how to avoid mistakes in developing criteria.