Decision support tool

# System assessment

## Risk assessment

Aim of the risk assessment is to analyse possible hazards in your supply system relative to each other and thus enabling priorisation of the risks. This can be done by analyzing the likelihood of occurrence and the severity of the public health impact for each hazard and deriving the risk from the combination of these criteria. For the occurrence of infectious diseases, the risk is usually classified high even if the likelihood of pathogen occurrence is only moderate (public health consequences can be severe due to secondary person-to person spreading). Where information is insufficient for categorizing the risk, a high risk may be used as default assumption.

Ranking your cyanotoxin risk in relation to the health risks from other hazards in the water will support you in decisions about priority control measures as well as improvements and long-term investment decisions.

A graphical representation of the different hazards as a risk matrix is a useful tool for ranking of specific hazards in the overall context (Fig.1). This procedure is often criticized as being subjective, however, such rankings are done anyway – implicitly – in investment decisions. It is thus better to perform the ranking consciously, to discuss the reasoning behind the ranking in the team, and to document the underlying information, assumptions and reasons.

Fig 1: Risk matrix

In the following you will find examples for fictitious water body systems with different assessment of the cyanotoxin risk in relation to risks from other hazards: