As its name suggests, a Preliminary Quantitative Risk Assessment (PQRA) is generally the first iteration of a risk assessment. The methods and assumptions prescribed in a PQRA are conservative and generally ensure that risks are not underestimated. Thus, if acceptable or negligible risks are predicted, then it is almost certain that risks are either acceptable or negligible.
However, if a PQRA suggests the potential for unacceptable risks, it does not mean that unacceptable risks are present. Instead, further assessment may be necessary to resolve conservatism and uncertainty in risk calculations before the actual health risk can be defined.
When risk management activities are implemented based on a PQRA, the result will generally be a greater reduction of risk than was necessary. A more detailed risk assessment will usually result in risk management activities that are more in line with actual risks. The complexity of a risk assessment is often decided based on cost and the feasibility of the proposed risk management approach.
More detailed risk assessments are called detailed Site Specific Risk Assessments, SSRAs. Generally in a risk assessment there is only one PQRA iteration. However, there may be multiple SSRA iterations, each building upon the last one (Health Canada 2004). The POPs Toolkit presents a risk assessment approach consistent with a PQRA. Additional reading and/or training will be required before participants can successfully conduct a SSRA.