Definitions of Hazard and Risk

Risk is the probability of harm or loss and can be considered to be a product of the probability and the severity of specific consequences. Risk, as it relates to hazardous wastes and groundwater contamination, may be defined as the chance that humans or other organisms will sustain adverse effects from exposure to these environmental hazards. Risk is inherent in the life of all organisms—Shumans, animals, and plants. Tornadoes, landslides, hurricanes, earthquakes, and other natural disasters carry a risk of injury or death to any living thing in their path. Similarly, human-caused risks such as automobile accidents, plane crashes, and nuclear disasters occur with varying levels of severity. 

Hazard is different from risk it is a descriptive term that characterizes the intrinsic ability of an event or a substance to cause harm. Hazard is one source of risk and is a function of the persistence, mobility, and toxicity of the contaminants. 

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In 1983 an important report [1] appeared which defined hazard and risk. It emanated from the United Kingdom s Royal Society, and resulted from a study group concerned with risk assessment for engineering and health risks. Definitions of hazard and risk were further elaborated by a Working Party of the United Kingdom s Institution of Chemical Engineers... 

ANSI/AIHA ZIO is an occupational health and safety management standard and its definitions of hazard and risk are, understandably, worker injury and illness related. They do not include considerations for possible damage to the environment or damage to property or business downtime. This chapter has a broader purpose, as will be seen. 

The HSE leaflet Hazard and Risk Explained presents the definitions of hazard and risk in relation to the COSHH Regulations ... 

The above definitions and the tenor of the report are based on an approach to the subject of risk from the standpoint of the natural scientist. TTie view of the social scientist had more influence in the subsequent report that places greater emphasis on the perception of risk by individuals and the public at large, especially when overlaid by media involvement. Most managers do not have the time to consider what some will view as the esoteric components of risk. The Health and Safety Executive offer the following definition of hazard and risk ... 

Definition of Terms Following are some definitions that are useful in understanding the components of hazards and risk (CPQRA, 1989, pp. 3, 4). 

The definition of safety in Guide 51 is Freedom from unacceptable risk (3.1). That definition is in concert with all previously cited definitions, other than for the dictionary definitions. It also implies an understanding of hazards and risks. 

The Center for Chemical Process Safety s projects fall into a number of general topic areas that comprise a comprehensive program. These topic areas include identification of hazards and analysis of risks, prevention and mitigation of the hazards identified, and better definition of areas affected by a release of hazardous materials. This book is the latest in the series dealing with hazard identification and risk analysis. 

Alphabetical List of Selected Generic Terms in Hazard and Risk Assessment and Their Definitions... 

The adverse reproductive effects are considered as being threshold effects, i.e., effects for which there are expected to be a threshold of substance concentration below which the effects will not be manifested. For the hazard and risk assessment, it is important to identify those dose levels at which adverse reproductive effects are observed, and the dose level at which adverse reproductive effects are not observed, i.e., to derive a NOAEL for reproductive toxicity. Crucial in the derivation of the NOAEL and/or LOAEL, is the definition of adverse effects (Section 4.2.2). In the derivation of the NOAEL and/or LOAEL, a number of factors need to be considered these issues are addressed in detail in Sections 4.2.3 and 4.2.4. An alternative approach to the derivation of the... 

In the following, several terms used to describe interactions between chemicals are mentioned as well as basic concepts used in the hazard and risk assessment of chemical mixmres. The description of these basic concepts, first outlined by Bliss (1939) and Placket and Hewlett (1952), are based on the publications by Konemann and Pieters (1996), Cassee et al. (1998), and Groten et al. (2001). The definitions of additivity, synergism, antagonism, and potentiation are those of Klaassen (1995) and Seed et al. (1995). 

Identify major hazards and inherent process risks (toxic, explosive). Systematic quantitative analysis of hazards and definition of measures to reduce them. 

The system for classification and disposal of hazardous chemical waste developed by EPA under RCRA does not apply to all wastes that contain hazardous chemicals. For example, wastes that contain dioxins, polychlorinated biphenyls (PCBs), or asbestos are regulated under the Toxic Substances Control Act (TSCA). In addition, the current definition of hazardous waste in 40 CFR Part 261 specifically excludes many wastes that contain hazardous chemicals from regulation under RCRA, including certain wastes produced by extraction, beneficiation, and processing of various ores and minerals or exploration, development, and use of energy resources. Thus, the waste classification system is not comprehensive, because many potentially important wastes that contain hazardous chemicals are excluded, and it is not based primarily on considerations of risks posed by wastes, because the exclusions are based on the source of the waste rather than the potential risk. 

Given the qualitative definitions of the three waste classes, the boundaries of the waste classes would be quantified based on explicit descriptions of how the definitions are related to risk. The boundaries would be expressed in terms of limits on amounts (concentrations) of individual hazardous substances, with specified rules for how to classify waste that contains mixtures of hazardous substances, such as the sum-of-fractions rule for mixtures of substances that induce stochastic effects. Specifically, waste would be classified as exempt if the risk that arises from disposal in a municipal/industrial landfill for nonhazardous waste does not exceed negligible (de minimis) levels. Use of a negligible risk to quantify limits on concentrations of hazardous substances in exempt waste is appropriate because the waste would be managed in all respects as if it were nonhazardous. Nonexempt waste would be classified as low-hazard if the risk that arises from disposal in a dedicated near-surface facility for hazardous wastes does not exceed acceptable (barely tolerable) levels. An essential condition of the definitions of exempt and low-hazard waste is that an acceptable (barely tolerable) risk must be substantially greater than a negligible risk. Waste would be classified as high-hazard if it would pose an unacceptable (de manifestis) risk when placed in a dedicated near-surface facility for hazardous wastes. 

PRINCIPLES, DEFINITIONS, AND PERSPECTIVES OF HAZARDOUS WASTE RISK... 

Perhaps the easiest definition of ecological risk assessment is the probability of an effect occurring to an ecological system. Note that the word "probability" is key here. Important components of a risk assessment are the estimations of hazard and exposure due to a stressor. 

These considerations lead to the most problematic part of definitions and interpretation of terms the acceptable risk, sometimes also called limit risk. A totally risk free activity, also referred to as zero risk, is feasible only if the activity is not exercised If it has been decided to go for a quantitative risk statement, this is unavoidably accompanied by the request for a scale to enable the assessment of the result. The definition of such a scale presents a subjective decision on the acceptability of risk, which splits the scale into the regions dangerous or hazardous and safe . The value for the limit risk has to be fixed in such a way that it takes into account the acceptability for the damage facing party and at the same time the tolerability from a third parties point of view. With this background it becomes obvious that the definition of a limit risk comes close to a philosophical task on the political field with societal impact. 

Before any pesticide can be authorized for use, its human and environmental safety have to be considered through risk assessment i.e., a comparison of hazard and exposure. A key element in the risk assessment process is the determination of the residue definition, i.e., the components of the residue resulting from the use of the pesticide that are considered to be relevant. Residues remaining on items for food and feed are identified in metabolism studies, in which the pesticide is radiolabeled to enable its fate and behavior to be followed. The metabolic pathways can be extremely complex but can be grouped into four distinct categories or phases [1],... 

The process whereby the risks associated with the use of pesticides are assessed has become Increasingly complex over the years, and even the definition of the term risk assessment Is widely variable. However, most Include the concepts of hazard and probability of occurrence and require Information on toxicology and exposure. In the Ideal situation there should be accurate data on the actual amount of pesticide to which the worker was exposed. Including the primary route of exposure, the absorption should be known, enabling correction of the exposure estimate, and the amount of pesticide necessary to cause toxic effects In test animals should be known. From these data. It could be determined whether the product could be used safely. 

A reasonable definition of hazard for the purposes of CRM is also provided in ISO/IEC Guide 51 1999 as a potential source of harm . One may decide to add ... to a patient to that definition to clarify that harm to a system s operators or those delivering healthcare is generally excluded. Interestingly there are other definitions of hazard which imply something which is inevitable and cannot in any way be avoided. This clearly flies in the face of risk management and such a definition would presumably preclude the existence of controls. Hazards are therefore entities which may or may not in the real world result in actual harm but certainly have the opportunity to do so should they fail to be adequately controlled. 

The following is typical of what is becoming universally accepted language with respect to hazards and risks. The section numbers appearing after some definitions refer to the ISO/IEC Guide 51. 

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