Government, industry and the community recognize the need to identify, assess and control the industrial risks (occupational and public) to people and the environment. Awareness of hazards and of the accidents that may result in significant loss of life and property have led to the development and application of systematic approaches, methods and tools for risk assessment and communication.

The risk assessment process involves: system description, the identification of hazards and the development of accident scenarios and outcomes for events associated with a process operation or a storage facility; the estimation of the effects or consequences of such hazardous events on people, property and the environment; the estimation of the probability or likelihood of such hazardous events occurring in practice and of their effects, accounting for the different operational and organizational hazard controls and practices; the quantification of ensuing risk levels outside the plant boundaries, in terms of both consequences and probabilities; and the assessment of such risk levels by reference to quantified risk criteria.

The process of quantified risk assessment is probabilistic in nature. Because major accidents may or may not occur over the entire life of a plant or a process, it is not appropriate to base the assessment process on the consequences of accidents in isolation. The likelihood or probability of such accidents actually occurring should be taken into account. Such probabilities and resultant risk levels should reflect the level of design, operational and organizational controls available at the plant. There are a number of uncertainties associated with the quantification of risk (e.g., mathematical models for consequence estimation, setting of probabilities for different accident scenarios, probability effects of such accidents). The risk assessment process should, in all cases, expose and recognize such uncertainties.

The main value of the quantified risk assessment process should not rest with the numerical value of the results (in isolation). The assessment process itself provides significant opportunities for the systematic identification of hazards and evaluation of risk. The risk assessment process provides for the identification and recognition of hazards and enables the allocation of relevant and appropriate resources to the hazards control process.

The objectives and uses of the hazard identification process (HIP) will determine in turn the scope of the analysis, the appropriate procedures and methods, and the personnel, expertise, funding and time required for the analysis, as well as the associated documentation necessary. Hazard identification is an efficient and necessary procedure to assist risk analysts and decision making for risk assessment and management of occupational safety and health. A number of major objectives may be identified:

• to establish what dangerous situations exist within a plant or a process operation
• to establish how these dangerous situations may come about
• to assist in the assessment of the safety of a hazardous installation.

The first general objective aims at extending the general understanding of the important issues and situations that might affect the risk analysis process for individual plants and processes; the synergy of individual hazards to the area study level has its special significance. Design and operational problems can be identified and a hazard classification scheme can be considered.

The second objective contains elements of risk assessment and deals with accident scenario development and interpretation of results. Consequence evaluation of various accidents and their impact propagation in time and space has special significance in the hazard identification phase.

The third objective aims at providing information that can later assist further steps in risk assessment and plant operations safety management. This may be in the form of improving the scenario specifications for risk analysis or identifying appropriate safety measures to comply with given risk criteria (e.g., individual or societal), or advice for emergency preparedness and accident management.

After defining objectives, the definition of the scope of the HIP study is the second most relevant element in the management, organization and implementation of the HIP. The scope of the HIP in a complex risk assessment study can be described mainly in terms of the following parameters: (1) potential sources of hazards (e.g., radioactive releases, toxic substances, fire, explosions); (2) plant or process damage states; (3) initiating events; (4) potential consequences; and (5) prioritization of hazards. The relevant factors that determine the extent to which these parameters are included in the HIP are: (a) the objectives and intended uses of the HIP; (b) the availability of appropriate information and data; and(c) the available resources and expertise. Hazard identification requires the consideration of all relevant information regarding the facility (e.g., plant, process). This might typically include: site and plant layout; detailed process information in the form of engineering diagrams and operating and maintenance conditions; the nature and quantities of materials being handled; operational, organizational and physical safeguards; and design standards.

In dealing with the external consequences of an accident, a number of such consequences may result (e.g., number of fatalities, number of people being hospitalized, various types of damage to the ecosystem, financial losses, etc.). The external consequences from an accident caused by the substance i for an identified activity j, can be calculated from the relationship:
Cij = Aa f_a f_m, where: Cij = number of fatalities per accident caused by the substance i for an identified activity j; A = affected area (ha); a = population density in populated areas within the affected zone (persons/ha); f_a and f_m are correction factors.

The consequences of (major) accidents to the environment are more difficult to estimate due to the variety of substances that can be involved, as well as the number of environmental impact indicators relevant in a given accident situation. Usually, a utility scale is associated with various environmental consequences; the relevant utility scale could include events related to incidents, accidents or catastrophic outcomes.

Evaluating monetary consequences of (potential) accidents requires a detailed estimate of possible consequences and their associated costs. A monetary value for special classes of consequences (e.g., loss of life or special biological habitats) is not always accepted a priori. The monetary evaluation of consequences should also include external costs, which are very often difficult to assess.

The procedures for identifying hazardous situations which may arise in process plants and equipment are generally considered to be the most developed and well established element in the assessment process of hazardous installations. It must be recognized that (1) the procedures and techniques vary in terms of comprehensiveness and level of detail, from comparative checklists to detailed structured logic diagrams, and (2) the procedures may apply at various stages of project formulation and implementation (from the early decision-making process to determine the location of a plant, through to its design, construction and operation).

Techniques for hazard identification essentially fall into three categories. The following indicates the most commonly used techniques within each category.

• Category 1: Comparative Methods: Process or System Checklist; Safety Audit Review; Relative Ranking (Dow and Mond Hazard Indices); Preliminary Hazard Analysis
• Category 2: Fundamental Methods: Hazard Operability Studies (HAZOP); “What If” Analysis; Failure Mode and Effect Analysis (FMEA)
• Category 3: Logic Diagrams Methods: Fault Tree Analysis; Event Tree Analysis.

Cause Consequence Analysis; Human Reliability Analysis

The appropriateness and relevancy of any one particular technique of hazard identification largely depend on the purpose for which the risk assessment is being undertaken. When further technical details are available one can combine them in the overall process for risk assessment of various hazards. Expert and engineering judgements can often be employed for further evaluation of risk for installations or processes. The primary principle is to first examine the plant or operations from the broadest viewpoint possible and systematically identify possible hazards. Elaborate techniques as a primary tool may cause problems and result in missing some obvious hazards. Sometimes it may be necessary to adopt more than one technique, depending on the level of detail required and whether the facility is a new proposed installation or an existing operation.

Probabilistic safety criteria (PSC) are associated with a rational decision-making process which requires the establishment of a consistent framework with standards to express the desired level of safety. Societal or group risks should be considered when assessing the acceptability of any hazardous industrial facility. A number of factors should be borne in mind when developing PSC based on societal risk, including public aversion to accidents with high consequences (i.e., the risk level chosen should decrease as the consequence increases). Whilst individual fatality risk levels include all components of risk (i.e., fires, explosions and toxicity), there may be uncertainties in correlating toxic concentrations with fatality risk levels. The interpretation of “fatal” should not rely on any one dose-effect relationship, but should involve a review of available data. The concept of societal risk implies that risk of higher consequences, with smaller frequency, are perceived as more important than those of smaller consequences with higher probabilities.

Irrespective of the numerical value of any risk criteria level for risk assessment purposes, it is essential that certain qualitative principles be adopted as yardsticks for risk assessment and safety management: (1) all “avoidable” risks should be avoided; (2) the risk from a major hazard should be reduced whenever practicable; (3) the consequences of more likely hazardous events should, wherever possible, be contained within the boundaries of the installation; and (4) where there is an existing high risk from a hazardous installation, additional hazardous developments should not be allowed if they add significantly to that existing risk.

In the 1990s an increasing importance has been given to risk communication, which has become a separate branch of risk science.

The main tasks in risk communication are:

• identifying controversial aspects of perceived risks
• presenting and explaining risk information
• influencing risk-related behaviour of individuals
• developing information strategies for emergency cases
• evolving cooperative/participative conflict resolution.

The scope and objectives of risk communication can differ, depending on the actors involved in the communication process as well as the functions and expectations they attribute to the communication process and its environment.

Individual and corporate actors in risk communication use manifold communicative means and channels. The main issues are health and environmental protection, safety improvement and risk acceptability.

According to general communication theory, communication can have the following functions:

• presentation of information
• appeal
• self-presentation
• definition of a relationship or decision path.

For the risk communication process in particular it can be helpful to distinguish between these functions. Depending on the function, different conditions for a successful communication process should be considered.

Risk communication can sometimes play the role of a simple presentation of facts. Information is a general need in a modern society. In environmental matters in particular there exist laws which, on the one hand, give the authorities the duty to inform the public and, on the other hand, give the public the right to know about the environmental and risk situation (e.g., the so-called Seveso Directive of the European Community and “Community Right-to-Know” legislation in the United States). Information can also be determined for a special public segment; for example, the employees in a factory must be informed about the risks they face within their workplace. In this sense risk communication must be:

• as neutral and objective as possible
• complete
• comprehensible for those who should get the information.

Appeals tend to incite someone to do something. In risk-related matters the following appeal functions can be distinguished:

• appeal to the general public or to a special segment of the public about risk prevention measures which could or should be taken (e.g., appeal to employees in a factory to take safety measures at work)
• appeal to the general public or to a special segment of the public about preventive measures for emergency cases
• appeal to the general public or to a special segment of the public about measures to be taken in case of an emergency situation (crisis management).

Appeal communication must be:

• as simple and comprehensible as possible, and as complete as necessary
• reliable; having confidence in the persons, authorities or other bodies which make the appeal is essential for the success of the appeal.

Self-presentation does not impart neutral information, but is mainly part of a persuasion or marketing strategy in order to improve the public image of an individual or to achieve public acceptance for a certain activity or to get public support for some kind of position. The criterion for the success of the communication is whether the public believes in the presentation. In a normative view, although the self-presentation aims at convincing someone, it should be honest and sincere.

These forms of communication are mainly of a one-way type. Communication aimed at reaching a decision or agreement is of a two-way or many-way type: there is not only one side which gives information—various actors are involved in a risk communication process and communicate with each other. This is the usual situation in a democratic society. Especially in risk- and environment-related matters communication is considered as an alternative regulatory instrument in complex situations, where easy solutions are not possible or accessible. Therefore the risky decisions with a relevant political importance have to be taken in a communicative atmosphere. Risk communication, in this sense, may include, among others, communication about highly politicized risk topics, but it may also mean, for example, the communication between an operator, the employees and the emergency services in order that the operator be best prepared in case of accident. Thus, depending on the scope and objective of the risk communication, different actors can participate in the communication process. The potential main actors in a risk communication environment are:

• the operator of a risky facility
• the potential victims of an undesired event (e.g., employees, neighbours)
• the regulatory authorities and appropriate political bodies
• the emergency services and general public
• interest groups
• the media
• insurers
• scientists and experts.

In a systems-theory approach all these categories of actors correspond to a certain social system and therefore have different codes of communication, different values and interests to be communicated. Very often it is not easy to find a common basis for a risk dialogue. Structures must be found in order to combine these different views and to achieve a practical result. Topics for such types of risk communication are, for example, a consensus decision about siting or not siting a hazardous plant in a certain region.

In all societies there exist legal and political procedures in order to deal with risk-related issues (e.g., parliamentary legislation, government or administrative decisions, legal procedures before a court, etc.). In many cases these existing procedures do not result in solutions that are entirely satisfactory for the peaceful settlement of risk disputes. Proposals reached by integrating elements of risk communication into the existing procedures have been found to improve the political decision process.

Two main issues have to be discussed when proposing risk communication procedures:

• the formal organization and legal significance of the process and of its results
• the structure of the communication process itself.

For the formal organization of risk communication there are various possibilities:

• The communication can take place inside or between existing bodies (e.g., between an agency of the central government, a local authority and existing interest groups).
• New bodies can be established specifically for the process of risk communications; various models have been developed (e.g., citizen juries, citizen panels, negotiation and mediation structures, mixed commissions consisting of operators, authorities and citizens). Most of these models are based on the idea of organizing a structured discourse in small groups. Significant differences of opinion exist about whether these groups should consist of experts, laymen, representatives of the political system, etc.

In any case the relationship between these communication structures and the existing legal and political decision-making bodies has to be clarified. Usually the result of a risk communication process has the effect of a non-binding recommendation to the deciding bodies.

Concerning the structure of the communication process, under the general rules of practical discourse, any argument is allowed if it fulfils the following conditions:

• adequate logical consistency
• sincerity (This means: The discourse should not be influenced by strategic or tactical thinking.)
• that the one who promotes an argument must be ready to accept the consequences of that argument also against himself or herself.

In the risk communication process various special rules and proposals have been developed in order to concretize these rules. Among these, the following rules are worth mentioning:

In the risk communication process a distinction must be made between:

• communicative claims
• cognitive claims
• normative claims
• expressive claims.

Correspondingly, differences of opinion can have various reasons, namely:

• differences in information
• differences in the understanding of facts
• differences in normative values.

It may be helpful to make clear through the risk communication process the level of differences and their significance. Various structural proposals have been made for improving the conditions for such a discourse and, at the same time, to help decision-makers to find fair and competent solutions—for example:

• For a fair discourse the result must be open-ended; if the aim is just to achieve acceptance for a decision that has already been made, it would not be sincere to open a discourse.
• If some solutions are simply not possible for factual, political or legal reasons, this must be clarified from the beginning.
• It may be helpful first to discuss not the alternatives, but the criteria which should be applied in evaluating the alternatives.

Effectiveness of risk communication can be defined as the degree to which an initial (undesired) situation is changed toward an intended state, as defined by initial goals. Procedural aspects are to be included in the evaluation of risk communication programmes. Such criteria include practicability (e.g., flexibility, adaptability, implementability) and costs (in terms of money, personnel and time) of the programme.

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