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Background to Risk Assessment and Management

1.1 The Case for Risk Assessment, Leading to Risk Management

Many different definitions of risk exist, using such terms as hazard, danger, and exposure. Therefore, to put oneself "at risk" means to participate voluntarily, or involuntarily, in an activity or event that could lead to injury, damage, or loss. Hence, "risk" refers to the possibility of experiencing harm from a hazard, and thus risk assessment involves evaluating the likelihood or frequency of experiencing a risk.

Since risks are about events that cause problems, risk identification typically starts with attention to the source of the problem or risk. According to US EPA, a risk assessment involves the evaluation of scientific information, including such dimensions as a dose-response relationship, and the extent of human exposure to a chemical. "Someone or something that creates or suggests a hazard" would be an example.

There is a distinction between hazard and risk; we need to understand this so that attention of resources can be directed to actions based primarily on the level of risk rather than just the existence of a hazard.

It is also important to be mindful of the distinction between risk and uncertainty. Risk can be characterized by consequences or impacts multiplied by probability. On the other hand, uncertainty is a term that applies to, for example, the predictions of possible events (e.g. the chemical concentration to which someone is exposed). Perhaps some of the events are only partially observable. Uncertainty might exist due to limited knowledge - perhaps we just do not know enough about how to describe a circumstance or a future outcome. The result is that both risk and uncertainty are highly relevant to the subject of risk assessment; both dimensions must be incorporated. Given this differentiation between "risk" and "uncertainty," the first set of chapters in this book will focus on "risk" where some possible outcomes are undesired or may result in a significant loss. Alternatively, attention to uncertainty is discussed primarily in Chapters 4 through 12.

Another important element of risk assessment is that society is moving toward more involvement in many decisions (e.g. where is a landfill to be sited?). This involves working toward rejecting having risks imposed on the public, and hence, an appreciation of the attitudes of the public is essential. There is an association of risk with chance or probability. One of the important dimensions of this is that it requires the quantification of the probability. It also means that the procedures by which risk assessment are developed must be logical and transparent to allow open dialogue with the public about how the risks are calculated.

As apparent from the above, there is a multistage process in which the elements of risk are calculated: first, the dimensions of risk are assessed, which is then followed by a decision whether risk management is required (is the risk sufficiently severe that efforts to control or manage the risk are required?). This is accomplished by the first step in this process being to identify the risks, followed by the determination whether management of the risks is necessary and feasible. This will include consideration of the probability of recurrence (Table 1.1).

Table 1.1 Steps related to risk management.

1. Establish the context of the risk - Criteria appropriate to judge the risks need to be carefully laid out. This will include consultations and communications with the needs of pertinent stakeholders to be initiated early in the process
2. Identify the risks - The hazards (what can go wrong) and the causes of such hazards need to be carefully delineated
3. Analyze the risks - The likelihood (probability) and severity (magnitude) of any and all consequences need to be characterized
4. Evaluate the risks - The risk estimates need to be considered in relation to the criteria set out in the beginning of the procedure
5. Treat risks - Practical options feasible to manage the high priority risks and monitor the low priority risks need to be determined
6. Monitor and review - Because circumstances may change, the basis must be monitored and periodically reviewed
7. Periodically communicate and consult - Extensive experience has consistently demonstrated that leaving communication and consultation steps to the end of the risk management process will usually create stakeholder outrage and avoidable conflicts

The development of risk assessment and management processing is definitely "a work in progress" as the profession continues to learn about the issues. There is substantial uncertainty that still remains. Regardless, it is important to understand the underlying principles; the assembly of data will continue to evolve. An example of a challenge is an individual who decides to undertake a potentially dangerous activity such as skydiving. The scientific approach to risk analysis does not necessarily allow the person to decide on how to deal or manage this type of risk although there may be strong evidence that certain activities are dangerous. Instead, most of the attention herein will be on risk in its most fundamental form. The approach in this book will involve the following: (i) identify a hazard, (ii) analyze the risk associated with that hazard, and (iii) determine if the elimination, or control, of the risk is warranted.

Risk enters the purview of the public in a wide spectrum of dimensions. Examples of risks that we may encounter on a daily basis are indicated in Table 1.2. Each day we weigh risks of different types of activities. We weigh the risk of injury when driving a car or riding a bicycle. We assess the number of people engaged in the activities and our perceived rate of injury and we decide whether or not to participate.

Table 1.2 Examples of risks encountered on a daily basis.

In words, innumerable aspects of everyday society involve a risk. It should be apparent that we cannot make all of the risks become zero but we can, and often do, avoid some risks. Different approaches are needed for different circumstances and different degrees of data availability. One of our concerns will be in establishing how to assemble and interpret data as a basis from which risk assessment can be developed. The strategies must consider both humans and the environment. In this context, the book develops the concepts and then builds the concepts and techniques into a strategy to undertake risk assessments.

This book primarily focuses on environmental risk. As will be shown, risks are pervasive. We can use parallels to other risks we face in society to develop reasonable trade-offs to allow decisions on risk management.

Ultimately, what is needed is to describe exposure assessments to human health and the environment, but the complications of risk assessment will be apparent when confronted with the spectrum of dimensions such as the degrees to which a chemical bioaccumulates and biomagnifies, the importance of ecological modeling, and dose-response methodologies. The preceding should be sufficient to demonstrate that the field of risk assessment and management is very data intensive and requires careful appreciation of data variability.

The emphasis herein will be on risk assessment. Risk management procedures go far beyond risk assessment and must deal with multifaceted aspects of a problem and must be responsive to the severity of conditions as well as to how much money is available and the degree to which management is feasible.

1.2 The Need for Risk Quantification

Key words in the preceding definition of risk in Section 1.1 are "voluntary" and "involuntary." Voluntary risks are hazards associated with activities that we undertake voluntarily such as walking down the stairs, riding a motorcycle, smoking cigarettes, or skydiving. Involuntary risks are negative impacts that may occur without a...