Risk assessment is a tool for the objective evaluation of risk, and is commonly performed by veterinary epidemiologists. Its use in the setting of veterinary epidemiology has increased in recent years, particularly as a tool for the objective consideration of the risk of movement of pathogens through international trade in animals and animal products. Risk assessment is only one component in an overarching risk analysis process, which also incorporates risk management (the process whereby procedures are implemented in order to reduce the risk) and risk communication (which involves the ongoing dissemination of relevant information to stakeholders). However, these other components of the risk analysis process will not be covered in further detail here as they are predominantly the responsibility of risk managers and policy makers.
What is risk?
In the context of risk assessment, the concept of risk can be viewed as the product of the likelihood of an event occurring and the consequences of that event. Additionally, the perception of the event is an important consideration, which can have a large impact upon risk. One example of a hazard which is generally perceived to be risky is radiation from nuclear power plants, due to a number of characteristics such as invisibility, association with long-term human health risks (including cancers), not viewed as being necessary, and being created from a process which many people do not understand. Therefore, when deciding where to site a nuclear power plant, consideration of the risk should include the likelihood of radiation release (which will generally be very low/negligible), the consequences of this (which are very high) and the perception of the risk by people who would live near to the power station.
Stages of a risk assessment process
Although the general process adopted during risk assessment is not affected by the intended application, a number of different risk assessment strategies have been developed. Of interest to veterinary epidemiologists are the OIE framework and the Codex Alimentarius Commission framework. The OIE approach is intended to estimate the risk of events (with associated consequences) occurring, and therefore is the framework used when investigating the movement of pathogens through animal trade. The CAC framework is based upon a model devised by the National Academy of Sciences National Research Council (NAS-NRC) in order to investigate the levels of chemicals of interest, and therefore devise maximum acceptable limits of these. As such, it is used in order to investigate the levels of pathogens and other contaminants in food.
As the OIE framework is most commonly used by veterinary epidemiologists investigating diseases of animals, this framework will be described in more detail here. The framework consists of three consecutive steps, all linked through risk communication in order to create an iterative, repeating process. These steps are hazard identification, risk assessment and risk management, and the first two of these will be covered in more detail below.
Hazard identification
Before a risk assessment can be conducted, the hazard(s) of interest must be identified. It is vital that all hazards of interest are identified, as if they are not identified in this stage, they will not be accounted for in the final risk assessment. For example, if a risk assessment was conducted in order to investigate the risk of Examples of hazards are 'the movement of at least one animal infected with pathogen x into a country over the course of one year', 'a level of contamination of meat of more than CFUs of Salmonella per cm2'
Risk assessment
Release assessment
Exposure assessment
===Consequence assessment