20.1 Introduction
If one searches the Internet for risk assessment', the result is a long list with a large variety of web pages. These pages relate to a wide range of disciplines such as medicine, safety at the workplace, finance, insurance, fire-fighting, and on-line gambling. Risk assessment is a tool that has been used since the earliest history and is used in almost any area, also in daily life. Central in every risk assessment is ahazard': an event with a possibly
negative impact that is poorly predictable or has a random character. In a risk
assessment one evaluates the probability of occurrence of the hazard and the
adverse effect of the hazard. As a daily-life example of a risk assessment, we can
think of a commuter who takes the bus to work every morning to arrive at 8:20
at the office. A couple of times a year the bus has a delay that causes him to
arrive at 8:35. One morning, this commuter has an important meeting at 8:30. He
decides to take an earlier bus to make sure he arrives at the office in time. Of
course the probability of having a delay is no different from any other day, but
the negative impact of the delay will be much larger on the day of the meeting.
The `risk' for the commuter, which is a function of probability and adverse
effect, is thus unacceptably high on the day of the 8:30 meeting, hence his
decision to take an earlier bus.
As a risk assessment is an evaluation of the probability of occurrence and the
adverse effect of a hazard, every risk assessment can be thought to consist of
four parts: (1) identify the hazard, (2) determine the probability of occurrence,
(3) determine the adverse effect, and (4) combine the above to estimate the risk.
Not every risk assessment scheme mentions these four parts explicitly, yet the
microbiological risk assessment according to the Codex Alimentarius
20
Risk assessment in hygiene management
I. H. Huisman, Nutricia, The Netherlands and E. Espada Aventı¬n,
Unilever R&D Vlaardingen, The Netherlands