Risk assessment is the systematic scientific characterization of potential adverse health effects resulting from human exposures to potentially hazardous agents or situations. This type of assessment includes qualitative information on the strength of the evidence and the nature of the outcomes, quantitative assessment of the exposure and the potential magnitude of the risks, and a description of the uncertainties in the conclusions and estimates. The essence of chemical (or material) risk assessment, in particular, even when that chemical originates from within a medical device (i.e. as an additive or indirect processing aide), is describing a system in which a hazard reaches its host and causes harm. Chemical or material risk assessment consists of four steps: hazard identification, exposure assessment, dose-response assessment, and risk characterization. The knowledge in each step is combined to represent a cause-and-effect chain from the prevalence and concentration of the chemical agent to the probability and magnitude of health effects. In risk assessment, risk consists of both the probability and impact of disease. In this way, risk reduction can be achieved in either dimension – by reducing the probability of disease or by reducing its severity. Risk assessment is different from both risk analysis and risk management, two processes which have recently gained in due importance by drug and device manufacturers.
In the hazard identification process of risk assessment, an association between disease and the presence of a chemical agent (or mixture, or material) is documented. The information may describe conditions under which the chemical causes adverse effects in biological systems. Epidemiologic and surveillance data, challenge testing, and scientific studies of pathogenicity also contribute information. Data collected during hazard identification are later used in exposure assessment, where the impact of processing, distribution, and preparation of the chemical agent are incorporated.
Exposure assessment, a second critical component or risk assessment, describes the pathways through which a chemical agent or other xenobiotic is introduced and distributed within an organism. This step differs from hazard identification in that it will usually describe a particular exposure pathway. Depending on the scope of the risk assessment, exposure assessment can begin with chemical prevalence in raw materials, or it can begin with the description of the final-form chemical at subsequent steps (e.g., during final clinical application). In any case, the intent of risk assessment is to track the chemical or material and estimate the likelihood of its exposure by the consumer (or patient). By completing the pathway to the exposed individual, we incorporate the important issues of dose-response assessment.
Dose-response assessment is used to translate the final exposure to a chemical or material into a health response in the population of exposed individuals. This step is usually very difficult because of the shortage of data on chemical-specific responses and because those responses may depend on the pre-existing health status, or genetic predisposition, of the exposed individual(s). However, even limited knowledge of the shape and boundaries of a dose-response function can be informative in comparing the efficacy of alternate controls. As noted, the differences in response among various susceptible populations are important features in this step.
Risk characterization, the final component of the risk assessment process, involves integrating the information gathered in the previous steps to estimate the risk to a population, or in some cases, to a particular type of exposed individual. In this step, by modifying the assumptions in the parameters of previous steps, we can study the effects of these alternate assumptions on ultimate health risk. Assumptions can be changed to study the impact of lack of knowledge and the potential gains through further research or to suggest the impact of a suspected trend. For this type of analysis, or more specifically when the opportunity or a material change exists, risk assessments are typically done in a computer environment to ease the computational burden and provide rapid responses to "what-if" questions using alternate assumptions and situations. These allow generation of complicated probabilistic models that had previously only been available through expensive custom software. Within this paradigm, existing situations are measured and compared according to a measure of population health risk. Similarly, proposed interventions are compared according to the reduction in population health risk that each intervention confers.
The adoption of risk assessment was primarily a result of legal and administrative challenges to regulatory authority during the 1970s. Regulatory agencies were required to provide a clear connection between an imposed regulation and an expected health benefit. If the expected health benefit could be quantified, the regulatory agencies were required to demonstrate that it was substantive. Quantitative risk assessment has since become widespread for different reasons. In environmental risk assessment, for example, it is now used proactively to support decisions such as selection of waste treatment technologies, contaminated site cleanup operations, and state and municipal priority setting for public health initiatives. For medicinal agents and devices, the assessment typically balances the improvement in “quality of life” with any imposed adverse effects, and they may oftentimes be used in lieu of actual product testing.
Numerous regulatory agencies have developed directives focusing on the general techniques of risk assessment and their role in public health decisions. Most directives have exploited the successes and failures and the wealth of constructive criticisms of frameworks, decisions, and methods for addressing pervasive uncertainties. Evidence-based best practices are employed by Walker Downey & Associates to characterize a client’s product risk. Our ultimate goal is to deem the risk “acceptable” by thorough expert analysis or, conversely, to provide recommendations as to how to achieve that objective. To that end, every risk assessment conducted by Walker Downey & Associates will generally include the following:
The principle audiences for this toxicological risk assessment are health professionals at the Federal, State, and local levels; interested private sector organizations and groups (i.e., Investigation Review Boards), and members of the public when “freedom of information” is required.Case Studies