Risk assessment process, hazardous

Identifying a hazard is only a small part of the risk assessment process. Hazard must be differentiated from risk. Assessing risk involves an analysis of the likelihood that adverse effects to human health or the environment after exposure to a chemical may occur. For risk management, exposure assessments therefore play equal (if not more) important parts as evaluations of hazard. The following sections discuss how toxicology, exposure assessments, and risk characterisations contribute to the central scientific definition of risk as probability versus consequence [93-95]. 

Access, lighting, and housekeeping standards Existing risk assessment process [hazard and operability (HAZOP), MOC, unit startups, work permitting] Recommendations from prior and current incident investigation teams... 

What arc some of the important complications in the "hazard identification step of the health risk assessment process ... 

Professor Martel s book addresses specifically some of the more technical eispects of the risk assessment process, mainly in the areas of hazard identification, and of the consequence/effect analysis elements, of the overall analysis whilst where appropriate setting these aspects in the wider context. The book brings together a substantial corpus of information, drawn from a number of sources, about the toxic, flammable and explosive properties and effect (ie harm) characteristics of a wide range of chemical substances likely to be found in industry eind in the laboratory, and also addresses a spectrum of dangerous reactions of, or between, such substances which may be encountered. This approach follows the classical methodology and procedures of hazard identification, analysing material properties eind... 

Assess Chemical Reactivity Risks Process Risk Management Process Hazard Analysis Evaluation of Major Hazards... 

PBPK models improve the pharmacokinetic extrapolation aspects of the risk assessment process, which seeks to identify the maximal (i.e., safe) levels for human exposure to chemical substances (Andersen and Krishnan 1994). PBPK models provide a scientifically sound means to predict the target tissue dose of chemicals in humans who are exposed to environmental levels (for example, levels that might occur at hazardous waste sites) based upon the results of studies where doses were higher or were administered in different species. Figure 2-4 shows a conceptualized representation of a PBPK model. 

The fire risk assessment process begins by collecting basic information about the design. For new projects there may be limited information available however a list of hazards can be developed, the potential fire impact can be assessed, and preliminary risk can be calculated. The level of detail of the fire risk assessment is only as good as the level of detail of the design information. The information needed to perform a fire risk assessment could include ... 

The Risk Assessment process includes four steps hazard identification, hazard characterization (related term dose-response assessment), exposure assessment, and risk characterization. It is the first component in a risk analysis process. 

For both human health and the environment, the risk assessment process includes (i) an exposure assessment, (ii) an effect assessment (hazard assessment and hazard characterization -addressed in detail in Chapter 4), and (iii) a risk characterization (addressed in detail in Chapter 8). As a part of the effect assessment, classification and labeling of the substance according to the criteria laid down in Directive 67/548/EEC (EEC 1967) is also addressed (Section 2.4.1.8). 

It is mentioned that the TTC concept has been incorporated in the risk assessment processes in a number of regulatory schemes as a scientifically sound tool to justify waiving or generation of animal data. It is also stressed that, in contrast to approaches such as read-across or chemical categorization, the use of the TTC is not focused or limited to the identification of potential hazards but also provides a quantitative estimate of potency. 

Hazard identification is the first step in the process of risk assessment, and hazard characterization is the second step. The hazard assessment is also known as effect assessment and is addressed in detail in Chapter 4. 

Risk characterization is thus the step in the risk assessment process where the outcome of the exposure assessment (e.g., daily intake via food and drinking water, or via inhalation of airborne substances) and the hazard (effects) assessment (e.g., NOAEL and tolerable intake) are compared. If possible, an uncertainty analysis should be carried out, which produces an estimation of the risk. Several questions should be answered before comparison of hazard and exposure is made ... 

Hazard identification is the process of collecting and evaluating information on the effects of an agent on animal or human health and well-being. In most cases, this involves a careful assessment of the adverse effects and what is the most sensitive population. The dose-response assessment involves evaluation of the relationship between dose and adverse effect. Typically, an effort is made to determine the lowest dose or exposure at which an effect is observed. A comparison is often made between animal data and any human data that might be available. Next is exposure assessment, in which an evaluation of the likely exposure to any given population is assessed. Important parameters include the dose, duration, frequency, and route of exposure. The final step is risk characterization, in which all the above information is synthesized and a judgment made on what is an acceptable level of human exposure. In the simplest terms, risk is the product of two factors hazard and exposure (i.e. hazard x exposure = risk). In real risk assessments, all hazards may not be known and exposure is often difficult to quantify precisely. As a result, the calculated risk may not accurately reflect the real risk. The accuracy of a risk assessment is no better than the data and assumptions upon which it is based. 

Communicating in a manner that accurately portrays risk and the nature of confidence in results is integral to and a major challenge for practitioners of probabilistic risk assessment. Inadequate communication of scientific uncertainty about the effect, severity, or prevalence of a hazard tends to increase unease among decision makers, stakeholders, and other participants. Efforts of the risk assessors should provide clarity for decision makers who must in turn bear ultimate responsibility for communicating the parameters of any decision. The risk assessor will work within a framework that must be clearly communicated by decision makers during the problem formulation. Decision makers at the outset of the risk assessment process must articulate the following points ... 

Risk assessment is quantitative and differs from risk management, which involves weighing options to reduce the risk. The risk assessment process begins with identifying the potential hazards and their occurrence in a specihc environment (i.e., exposure assessment), their toxicity (i.e., dose-response), and a characterization of the risk (NRC, 1994). Risk assessment determines the probability of realizing harm as a result of exposure to a given hazard. 

Risk assessment starts with risk identification, a systematic use of available information to identify hazards (i.e., events or other conditions that have the potential to cause harm). Information can be from a variety of sources including stakeholders, historical data, information from the literature, and mathematical or scientific analyses. Risk analysis is then conducted to estimate the degree of risk associated with the identified hazards. This is estimated based on the likelihood of occurrence and resultant severity of harm. In some risk management tools, the ability to detect the hazard may also be considered. If the hazard is readily detectable, this may be considered a factor in the overall risk assessment. Risk evaluation determines if the risk is acceptable based on specified criteria. In a quality system environment, criteria would include impact on the overall performance of the quality system and the quality attributes of the finished product. The value of the risk assessment depends on how robust the data used in the assessment process is judged to be. The risk assessment process should take into account assumptions and reasonable sources of uncertainty. Risk assessment activities should be documented. 

Attempts to reduce the uncertainty of particular aspects of the risk assessment process do not succeed in decreasing the uncertainty attached to the overall assessment. For example, great efforts are put into standardizing methods of testing, so that a test will produce the same result time after time, from laboratory to laboratory.4 This increases the certainty as to whether a chemical has a particular hazardous property or not and enables the concentration at which it has an adverse effect to be precisely defined. However, precision and certainty are only achieved because the property is defined in relation to the very particular conditions under which the test is carried out it is doubtful that these conditions are representative of the situations that are of concern, in which heterogeneous wild animal or human populations are exposed to chemicals. We may be sure of the result of the test, but very uncertain as to its relevance with respect to the risks we are trying to assess. 

Through functional-use analysis, toxicological and environmental fate data on structurally similar chemicals can be applied to each member of a functional-use class. A focus on functional use not only offers commonality in perspective for chemical innovators, but also simplifies the risk assessment process. Within a given product dass, the use and exposure patterns are generally the same, with minor variability therefore, the hazard component of the risk equation becomes a... 

A chemical may constitute a number of hazards of different severity. However, the primary hazard (or critical effect) will be the one used for the subsequent stages of the risk assessment process. For example, a chemical may cause reversible liver toxicity at high doses but cause tumors in the skin at lower doses. The carcinogenicity is clearly the hazard of concern. 

The immediate future in risk assessment will focus on the difficult but necessary task of integrating experimental data from all levels into the risk assessment process. A continuing challenge to toxicologists engaged in hazard or risk assessment is that of risk from chemical mixtures. Neither human beings nor ecosystems are exposed to chemicals one at a time, yet logic dictates that the initial assessment of toxicity start with individual chemicals. The resolution of this problem will require considerable work at all levels, in vivo and in vitro, into the implications of chemical interactions for the expression to toxicity, particularly chronic toxicity. 

The risk assessment process involves describing the toxicological hazard profile of a chemical substance, using qualitative and quantitative data, and coupling this to an estimate of exposure to assess any risk. Consequently, the information that is required on packaging chemicals comprises (a) toxicity data and, (b) exposure data. 

Fig. 3.4. Depiction of probabilistic exposure and risk assessment process for hazardous waste disposal (Garrick and Kaplan, 1995).

Dose-Response Relationships. The primary objective of this study is to set forth the foundations of a risk-based waste classification system that applies to hazardous chemicals and radionuclides. Most aspects of the risk assessment process that provide the basis for establishing this system are conceptually the same for chemicals and radionuclides, although the specific data (e.g., solubilities) may differ. One important exception is the assumed relationship of the probability of a response to a unit dose of a substance that causes stochastic effects, which is called the dose-response relationship There are important conceptual differences in the way this relationship has been defined and used for hazardous chemicals and radionuclides, and these differences could pose a major impediment to development of a risk-based waste classification system that applies to both types of substances on a consistent basis. These differences are elucidated in the following section. 

In general, calculation of the risk or dose from waste disposal in the numerator of the risk index in Equation 6.2 or 6.3 involves the risk assessment process discussed in Section 3.1.5.1. As summarized in Section 6.1.3, NCRP recommends that generic scenarios for exposure of hypothetical inadvertent intruders at waste disposal sites should be used in calculating risk or dose for purposes of waste classification. Implementation of models describing exposure scenarios for inadvertent intruders at waste disposal sites and their associated exposure pathways generally results in estimates of risk or dose per unit concentration of hazardous substances in waste. These results then are combined with the assumptions about allowable risk discussed in the previous section to obtain limits on concentrations of hazardous substances in exempt or low-hazard waste. 

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