This section describes the risk assessment process and its relationship to risk management in the context of a hazardous chemical incident. The information provided in this section can be used to support various aspects of the planning and decision-making process described in Section 2 above. In general, risk assessment methods are used to evaluate the probability and consequence of exposure in a given chemical incident, for example: chemicals detected in the environment in terms of their inherent toxicity; how people may come into contact with the chemicals; the total dose to those exposed, and; who may be exposed now and in the future (e.g., response workers, children, the elderly, populations experiencing high and adverse human effects of environmental events, practices or programs). The results of the analysis are used by risk managers to determine if chemical contamination is at a magnitude requiring remediation/cleanup (human health risk above targets) and the appropriate scope of the response action.
In the context of a hazardous chemical release, different risk assessment methods may be used to support consequence management planning and decision making. As data on the nature and extent of contamination become available, safety and health experts will use certain risk assessment tools to evaluate the immediate threats to exposed populations and provide guidance for first responders on the type of PPE that may be necessary and other protective measures detailed in the HASP. In later phases of the response, other risk assessment tools will be used to evaluate the protectiveness of pre-calculated, health-based exposure guidelines, evaluate potential risks associated with residual contamination, and to derive protective clearance goals.
Overall, the effective remediation of hazardous chemicals following a hazardous chemical release depends on accurate information being factored into the risk assessment, such as the nature and extent of contamination; the inherent toxicity of the chemicals; how people come into contact with the chemicals; the exposure duration and frequency; the total dose; and who may be exposed now and in the future. However, adequate information is not always available, especially in the early stages of a response. A further complication can be the existence of classified toxicity information that cannot be shared freely, especially in the early stages of the response. As the amount and quality of the data used to develop risk-based estimates increases, uncertainty in decision-making decreases.