Risk is often defined as the likelihood of a certain event times a measure of the severity of its consequences. Most risk assessment studies concentrate on estimat­ing the likelihood of certain events. They often concern the release of chemicals, or accidents in engineering projects and the project outcome. In this section, the subject of accidents is not covered. Risk assessment (RA), as a technique, has been adopted by various national governments, by EU,1 and by OECD.2 RA has four basic components.

1. The collection of problems at the “formulation stage,” which identifies the compound or activity of concern, the persons or species to be protected, and the effect and end-point evaluation.

2. Hazard evaluation or the definition of the effects that may occur, including dose-response characteristics and other intrusive processes.


3. The evaluation of the actual exposure circumstances. The hazard evaluation and the exposure evaluation are then combined in a fourth component.

4. The risk characterization, where the likelihood of an exposure sufficient for an impact is estimated.

If no significant risks are found, no further evaluation is made. If a signif­icant risk is found, the RA is refined with more comprehensive hazard evalua­tions, exposure assessments, and mitigation actions. The components of the RA process are detailed further in Fig. 15.6. Concepts such as “risk percep­tion” and “risk management” often appear together with risk assessments. The risk perception by various population groups may be investigated as part of a risk management program.

Using formalized risk assessment techniques for industrial ventilation projects may complicate the issue more than necessary. The work environment and its exposure conditions are the focus. However, when evaluating new technology, including waste management, the risk assessment approach may be valuable.


1. Technical Guidance Document in Support of the Commission Directive 93/67/EEC on Risk Assessment for New Notified Substances and the Commission Regulation (EC) 1488/94 on Risk Assessment for Existing Substances, European Commission, 1996.

2. OECD, Environmental Health and Safety Documents, 1988-1999.