PART I

FUNDAMENTAL CONCEPTS IN RISK MANAGEMENT

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FUNDAMENTAL CONCEPTS IN RISK MANAGEMENT 1. HAZARD, RISK, AND RISK MANAGEMENT

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A thing is safe if its attendant risks are deemed to be acceptable.

This insightful phrase, coined by William Lowrance in 1976, constitutes the bedrock of modern risk management theory and practice when dealing with hazardous chemicals and other environmental contaminants in our contemporary society. But what exactly does it mean? Clearly we all desire a reasonable degree of safety with respect to our personal health and the health of our loved ones. But how willing are we to accept the fact that no activity in life is absolutely safe under all circumstances? Most of us will acknowledge that life presents us with many risks of uncertain probability and severity, and that a risk-free life would invariably be one that is impoverished, unexciting, and ultimately futile. So we often accept certain risks, some of them quite cheerfully, when they are associated with personal benefits to our lives�especially those that contribute to the betterment of our employment prospects, material prosperity, and recreational enjoyment. Many of us consider voluntary exposure to hazardous situations as acceptable whenever the expected benefits outweigh the perceived risks, assuming of course, that we retain a free choice in deciding whether or not to subject ourselves to these hazards. On the other hand, we will barely tolerate or actively oppose risks beyond our personal control, regardless of the anticipated degree of risk. Such involuntary risks include those created by the wide array of man-made chemical pollutants that seem to pervade our natural environment. We encounter these involuntary risks reluctantly, with a sense that we accrue no detectable benefit for ourselves, while worrying that our health might be seriously impaired, even to the point of premature death. Ideally, we seek to avoid these risks absolutely. So this type of risk we want minimized, or preferably eliminated

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altogether. In fact, many of us tend to be skeptical about statements made by those in government and industry who assure us that something is absolutely safe, and that �nothing can possibly go wrong.� But how feasible are strategies dedicated to the total elimination of toxic hazards in the environment? Some short-lived substances of minimum commercial value can indeed be successfully banned from production, import, and use. But to the extent that many hundreds of chemicals play an essential role in modern industrial societies, their continued use will require the implementation of environmental controls that are strict enough to reasonably ensure the health of humans and other living things, while not imposing an unnecessary burden of production limitations and costs of control for the affected industries. Thus, a realistic definition of environmental safety will often entail incurring a very small risk to personal health�one that is commonly deemed acceptable or tolerable because it produces a relatively insignificant probability of disease incidence when compared to other more prevalent disease states or compared to other more important disease causes. The risk management process is the means by which governments and other standard-setting organizations seek to define a rational level of acceptable or tolerable risk for an environmental hazard�by considering the severity and probability of harmful health effects, the amount of environmental exposure experienced by human populations, the sources and means of control for the contaminant, and the expected costs and benefits of various risk reduction strategies. Like all decision-making systems, risk management has its particular strengths and weaknesses. Its greatest strength is thought to be the scientific rigour with which the risk management process applies logical and consistent methods to arrive at sound decisions for technically complex problems. Its greatest potential weakness lies in the mindless lock-step application of formalized rules for risk decision-making, without making adequate allowance for human concerns beyond the scope of established scientific criteria. The seemingly incomprehensible technical jargon employed in the production of risk management reports is also a common problem. The former trait leads to technocratic decisions that often do not jibe well with social reality, while the latter encourages obscurity rather than clarity in communicating how decisions were achieved. In certain instances, the decision tools of a risk management system may even be misused, with possible serious consequences for population health or for the economic sustainability of a segment of society. It has been said that democracy is the least effective form of government for managing a country, except for all the others. Like democracy, risk management derives its greatest advantage, not from technocratic rationality, but by its ability to organize and examine

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scientific and socioeconomic information in a public forum open to free communication and debate by all concerned parties. In this sense, risk management should be viewed as means of promoting public accountability by communicating information about risk among stakeholders, with the objective of producing decisions that include both sound science and prudent decision-making.

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Risk and hazard are two distinct, but interrelated, concepts. A hazard represents a chemical, physical, or biological substance that has the potential to produce harm to health if it is present in the environment and comes into contact with people. The hazardous properties of an environmental agent are defined according to the nature and severity of its harmful consequences. Fortunately, many hazards can be either contained or avoided, so not every potential environmental hazard poses an actual health risk. A risk, in turn, is defined as the likelihood of adverse health effects arising from exposure to a hazard in a human population, which is conceptually expressed as the product of two factors�the probability of exposure and the severity of the consequences.

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The degree of risk can be determined in one of two ways. Some risks can be measured directly by observing past and present disease incidence patterns in the human population. Alternatively, risks can be calculated indirectly, by estimating the theoretical level of human exposure and the potential severity of health effects as predicted by experimental studies. The health risks from low-level exposure to environmental hazards are commonly determined by the indirect method, because there is not enough consistent and reliable evidence of measurable health effects in human populations exposed to low levels of hazardous environmental agents. It must be recognized that the risks from low-level environmental exposure are theoretical calculations, not observed facts. So one must exercise considerable caution when employing such risk predictions for controlling hazards in the environment. This is why risk assessment and risk management decisions are both difficult and important. The risk of illness or death arises in everyday life from many potential sources�physical risks from accidents and violence, health risks from infectious microbes and environmental pollutants, or medical risks from the adverse effects of pharmaceutical drugs and medical devices. Most people want to exert some reasonable degree of control over the important risks in their lives. They use their personal experiences or the insights of knowledgeable professionals to estimate the nature and

Hazard is commonly defined as �the potential to cause harm�. A hazard can be defined as �a property or situation that in particular circumstances could lead to harm.� � Risk is a more difficult concept to define. The term risk is used in everyday language to mean �chance of disaster�. When used in the process of risk assessment it has specific definitions, the most commonly accepted being �The combination of the probability, or frequency, of occurrence of a defined hazard and the magnitude of the consequences of the occurrence.� Royal Society (U.K.), 1992

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degree of risks from various sources; they evaluate the level of risk that they are prepared to accept or tolerate; and they try to control risk by balancing acceptable risk against the perceived benefits for a particular course of action. These three activities�risk estimation, risk evaluation, and risk control�collectively comprise the core of the decision process that we call risk management. In this sense, people continually undertake risk management in many aspects of their everyday lives. To the extent that we usually consult with other people who might be affected by our decision, before making important risk choices, the process of risk communication is also an essential component of risk management.

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In the context of environmental health, the risk management process can be organized into several distinct activities. The three core activities that constitute the essential decision-making steps in the risk management process are each involved in examining different aspects of the risk problem:

risk estimation

the use of science-based risk information and analytical methods to characterize the nature and extent of environmental health risks in the human population;

risk evaluation

consideration of the economic, social, political, and legal factors that influence a decision to adopt a particular course of action to reduce health risks�in some risk frameworks, the quantitative economic analysis of the benefits and costs of risk reduction is combined with results of the risk estimation process, so that a �risk assessment� may subsume part or all of risk evaluation;

risk control

the selection of options and the commencing of actions intended to reduce risk to an acceptable or tolerable level; this activity is often referred to as �risk management,� but the term �risk control� is more specific and better reflects the objectives of the activities it denotes.

These core processes are conventionally arranged in an ordered sequence of steps, so that risk estimation is typically thought to come first, risk evaluation second, and risk control third. This stepwise arrangement is intended to ensure that the source of information in risk decision-making flows primarily from well-validated scientific studies, before moving onto the more value-laden consideration of

In addition to the three major steps, there may also be one or more preliminary stages comprising the initiation of the review process, and the preliminary analysis of available scientific and technical information; as well as a terminal stage of implementation and monitoring of the actions aimed at risk reduction.

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socioeconomic factors and technical control options. In most countries, with the notable exception of the United States, each of the steps is intimately connected to the others by a continuous two-way flow of communication occurring in an iterative manner. An effective risk management process also requires ongoing consultation among all concerned parties, or stakeholders, to resolve questions of policy, science, and societal concerns. A stakeholder is defined as a person or group that could be affected or potentially affected by a specific health risk, any groups or organization that would be affected by efforts to manage the source of the risk, and the risk managers themselves. The risk communication process provides an essential coordinating function, by supporting the activities of information exchange and mutual consultation among various stakeholders�governmental, non-governmental, and private-sector organizations�throughout the various phases of the risk management process. Risk communication activities represent the organizing principle which links stakeholders together to enable a coherent decision-making process.

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Many organizations with responsibility for managing environmental health risks have adopted some form of risk framework to organize the activities needed to support the development of sound environmental strategies, and to improve the understanding of the stakeholders. The risk management process adheres to this systematic decision-making framework, whose activities are arranged as an ordered sequence of steps. While a risk framework describes the steps that decision-makers should follow to arrive at a final environmental control strategy, the framework is not intended merely to ensure procedural correctness or to serve as a workflow diagram. A well-designed risk framework specifies all the component activities of the risk management process, their interconnections, the flow of information, and the critical decision points within the process. Risk frameworks have been devised by several organizations in Canada, the United States and elsewhere. All are intended to provide a structured approach to health risk assessment, evaluation, and management. While various risk frameworks generally agree about broad principles, some differences do exist in risk terminology, the level of detail, the importance of factors such as risk communication, and the involvement of stakeholders in the overall process. Although at present there is no official Canadian framework for risk management, a consensus guideline for risk management has been recently developed by the Canadian Standards Association, entitled CAN/CSA-Q850-97 Risk Management: Guideline for Decision-Makers.

A risk management framework is a formal method for assessing and managing health risks. The framework that this transition team is working on will give all of Health Protection Branch (HPB) a common basis for addressing risk assessment and management. HPB transition plan -- The revised framework will provide a basis for Health Canada's strategic approach to public health risk management, and provide the foundation for development of Departmental policies on risk management. To the extent possible, the framework should be consistent with other national and international frameworks which are relevance to programs within the Health Protection Branch. The framework will provide a structured, consistent, and comprehensive approach to risk assessment and management within the Branch, but at the same time, allow for flexibility in implementation. It will also help to identify the roles, responsibilities, and interactions of partners and other stakeholders in the risk assessment and management process. INFORMATION October 1998 Health Protection Branch Branch-Facts

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An analogous risk framework, Risk Determination: A Model for Risk Assessment and Risk Management, has been developed by the Health Protection Branch (HPB) of Health Canada. In the United States, the earliest and most elaborate risk framework for environmental health was developed by the U. S. National Research Council (NRC) in 1983. The 1983 NRC report Risk Assessment in the Federal Government: Managing the Process defined the major stages of the risk assessment and risk management process, and described, in great detail, the structure and logical development of the risk assessment process. The risk assessment process is expected to deal exclusively with numerically quantifiable scientific data and statistical methods used to analyze that data, i.e., Risk Identification and Risk Estimation issues. Thus it is commonly asserted that risk assessment methods rest firmly on the foundations of �sound science�, in accordance with the principles of scientific objectivity, absence of bias or prejudice, and apolitical approaches to appraising evidence. Such worthy attributes provide the strongest rationale for a fundamental reliance on risk assessment in guiding environmental policy-making.

In addition to providing a structured guideline for decision-making, some risk frameworks also allow the flexibility needed to address specific health hazards on a case-by-case basis. In the United States, the use of 1983 NRC framework for the risk assessment and management of environmental contaminants has become institutionalized over time, serving as an official protocol with an important legal status in regulatory decision-making. In practice, such a legalistic approach in the development of environmental standards has created a relatively inflexible decision-making structure not originally envisaged by its proponents. Risk frameworks in most European Community countries tend to be more flexible; they are accorded formal recognition by governments, but are typically used as guidelines rather than regulatory protocols. The use of risk frameworks by Health Canada, Environment Canada, and other Canadian regulators is usually cited by foreign observers as representing a reasonable middle ground�less cumbersome than the U.S. EPA�s legalistic risk framework, and more consistent than the consensus-based decision-making processes employed by many European organizations.

���������� �������� In Canada, a broadly-applicable risk framework, CAN/CSA-Q850-97 Risk Management: Guideline for Decision-Makers, has recently been developed and approved under the auspices of the Canadian Standards Association (CSA). The Q850 framework is based on the collaborative efforts of representatives from government, industry, research, and environmental organizations. The most important of the major steps in the Q850 risk framework will now be described.

The NRC (1983) report has in turn provided the conceptual and operational foundation for the later development of a series of risk assessment guidelines, most notably the series of EPA guidelines for the risk assessment of environmental carcinogens, mutagens, developmental toxicants (teratogens), male and female reproductive toxicants, immune system toxicants, and neurological toxicants.

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This first step defines the context and organizational structure under which a specific risk management problem will be resolved, including such issues as: the scope of the problem, the terms of reference under which the problem will be addressed, the concerned parties or stakeholders who will be invited to act as participants in the risk management process, the decision-making bodies responsible for resolving the problem, the legislative and legal mandates for anticipated regulatory actions, and the time frame under which the process will operate.

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The Risk Identification step assesses the likelihood that an environmental agent might constitute a potential health hazard, based on its physico-chemical properties, its toxicological effects in test animals, and its observed human health effects. Because the terms risk and hazard are often used interchangeably in different parts of the world, both risk identification and hazard identification denote the same type of activity within the Q850 framework.

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The Risk Estimation step attempts to quantify the amount of risk incurred by various levels of exposure to environmental contaminants. The Risk Estimation stage is a multiphasic process which consists of the following three activities:

Dose-response assessment

The dose-response assessment step estimates the probability of occurrence of harmful effects that might arise from a specified level of exposure to a substance, based principally on epidemiological studies in human populations and toxicological studies in test animals.

Exposure Assessment

Exposure assessment determines the expected patterns and levels of exposure to a substance in various segments of the population, including estimates of the dose level, duration of exposure, and continuity of exposure over time for various environmental media�particularly air, water, soil, and food. Of special concern is the exposure incurred by possibly susceptible subgroups within the population�the young, the aged, women of reproductive age, those with pre-existing health problems, and visible minorities or disadvantaged sectors of society.

Risk Characterization

This step combines the qualitative findings about the nature of a hazard as determined by the risk identification (hazard

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identification) step, together with the quantitative estimates of harm as determined by the dose-response assessment step and the exposure assessment step. The risk characterization specifies the likelihood of harmful health effects for various levels of exposure within a range of likely exposure scenarios. The risk characterization provides a well-documented summary of the critical findings of the risk assessment process, which serves as the scientific basis for decision-making in the later risk evaluation and risk control stages. Ideally, it also serves as the basis for effective risk communication with scientists, regulators, stakeholders, and the general public.

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The major issues to be addressed at the risk evaluation stage include social factors, economic factors, political factors and legal factors. A balancing between the costs of control and the predicted health benefits from reduced exposure are estimated, informally by consensus, or analytically by cost-benefit analysis and similar economic methods. Factors not readily quantifiable, such as the societal acceptance of a risk in affected groups, and the legal and political aspects of regulation within existing federal-provincial jurisdictions are also reviewed.

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Under the Q850 framework, the Risk Control step consists of several major activities: Identifying Feasible Risk Control Options, Evaluating Risk Control Options, and Stakeholder Assessment of Options. This involves a process of evaluating alternative regulatory and non-regulatory options and selecting the most appropriate option. The option selection task entails the use of value judgments on such issues as acceptability of risk and the reasonableness of the cost of control.

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This final step includes the implementation of regulatory and voluntary actions, and monitoring of the compliance with and effectiveness of the actions.

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In addition, the Q850 framework emphasizes the critical role of Risk Communication process in the decision-making process. In earlier frameworks, this activity has often been overlooked, or treated merely as an information dissemination process, intended to explain and justify risk management decisions to concerned stakeholders and the general public. In contrast, risk communication under the Q850 framework is conceived as a bidirectional consultative exchange that works at virtually all stages within the risk management process. Risk communication involves extensive stakeholder participation, encouraging of an ongoing dialogue between the risk managers and concerned participants regarding all aspects of the entire risk

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management process. Its primary objective is to mutually inform, not to persuade or bargain, nor to act as a public relations vehicle. Risk communication activities thus run parallel to the entire spectrum of risk assessment, risk evaluation, and risk control activities. The Q850 framework also includes a series of discrete decision points interposed between each of the major stages. When critical information is deemed adequate for decision-making, an informed judgement can be passed to the following stage in the form of a summary of findings or as a recommendation for action. Conversely, when inadequate information is available, a query can be referred back to a previous stage for further data collection and analysis. This type of risk decision system is therefore constructed as an iterative process�one which can be repeated, if required, as long as essential information or analysis is missing. Accordingly, any decision step in the framework can be revisited whenever additional information or analysis is required, and the entire process can be restarted when new information becomes available at a later time. The multiple decision points also allow for intermediate decisions to terminate the risk management process when existing information indicates that further data collection or decision analysis is unwarranted. For example, if a newly detected environmental contaminant were found to be produced exclusively by natural processes which were not amenable to control measures, the risk management process could be terminated at the risk identification stage. Similarly, if a decision were made by a manufacturer to permanently withdraw a potentially toxic substance from production and distribution, then the decision process concerning possible regulatory actions could be terminated at the risk control stage.

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The Health Canada risk management framework, Risk Determination: A Model for Risk Assessment and Risk Management, was developed in the early 1990�s by the Health Protection Branch (HPB). It has served as a guideline to assist Health Canada in protecting Canadians against environmental hazards�such as chemical pollutants and food contaminants�and other public health activities to control disease and injury. In the environmental health arena, the influence of the HPB risk framework carries beyond the confines of Health Canada, as this agency also plays an advisory role for health risk assessment of environmental substances regulated by several other departments, most notably trans-boundary environmental pollutants (with Environment Canada) under the Canada Environmental Protection Act (CEPA).

The Health Protection Branch (HPB) Transition will result in a number of proposals to renew the health protection program: - a decision-making framework and process that is transparent and open to public and stakeholder input; - a legislative framework that provides the necessary authorities to protect the health of Canadians; - a comprehensive Risk Management Framework that is clear on the accountability of HPB scientists and managers; INFORMATION October 1998 Health Protection Branch Branch-Facts

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The HPB framework reflects several significant differences between Canada and the United States in government decision-making practices. Most notably, the distinction between risk assessment as an objective scientific enterprise and risk evaluation as a subjective non-scientific process is less strongly emphasized in Canada than in the United States. The HPB framework reflects a sense that a prescriptive scientific methodology for risk assessment inevitably contains hidden value assumptions and inherent societal biases. Hence, any attempts to place a �firewall� between the scientific analysis and the consideration of societal concerns is deemed neither desirable nor entirely achievable in a consensus-driven regulatory regime such as the Canada�s. Under the HPB framework, Risk Assessment is structured to include both consideration of scientific evidence in a Risk Analysis step, and analysis of socioeconomic concerns in an Option Evaluation stage. The HPB Option Evaluation step is generally equivalent to the Q850 Risk Evaluation step, and is treated by HPB as part of the overall Risk Assessment process. The HPB framework also interposes a Decision step between the risk assessment and risk management phases. The decision step is necessary to connect the risk assessment activities with the risk management activities through a decision pathway. Initially, the decision step was represented by a blank box, which contained no defined activities. Later versions of the HPB framework include some specific provisions for the decision step. A possible weakness in the HPB framework is the assumption that only one decision point exists in the flow of risk information. In practice, however, incremental decisions within the Health Protection Branch are typically made at several points throughout the risk assessment and risk management process.

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One of the earliest and most influential risk management frameworks was devised in 1983 by the U.S. National Research Council, and is commonly referred to as the NRC �Red Book.� This framework was presented in the report entitled Risk Assessment in Regulatory Decision-Making: Managing the Process. The NRC framework states unequivocally that scientific evidence and political considerations should not be allowed to mix, and that the scientific aspects of risk assessment should thus be completely separated from the non-scientific aspects of risk management. Adherence to �good science� as the foundation of the risk management

Risk Assessment

Risk Management

Risk Analysis

Option Evaluation

Hazard Identification

Risk Estimation

Development of Options

Option Analysis

Decision

Implementation

Monitoring and Evaluation

Review

Risk Determination: A Model for Risk Assessment and Risk Management (HPB, 1990)

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Scientists assess a risk to find out what the problems are. The process of deciding what to do about the problems is risk management... Despite these often conflicting pressures, risk assessment at EPA must be based on scientific evidence and scientific consensus only. Nothing will erode public confidence faster than the suspicion that policy considerations have been allowed to influence the assessment of risk. William Ruckelshaus (1983), EPA Director, addressing National Academy of Sciences.

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process is therefore deemed paramount. Without sound science in risk assessment, it is thought that credible decision-making cannot be achieved at the later stages of the risk management process.

The U.S. EPA states that its own risk assessment guidelines �� are similar to those proposed by the NRC� and it specifically endorses the NRC risk assessment terminology. As adopted and implemented for regulatory standard-setting by the U.S. EPA, the NRC framework is broadly viewed as a scientifically exhaustive, procedurally rigourous, and highly transparent means of deriving environmental health standards within the highly legalistic regulatory requirements of U.S. government system. However, EPA-style risk management has been frequently criticized as being excessively prescriptive in defining the procedural norms for conducting risk assessment of scientific evidence and as overly rigid in government decision-making, leading in many instances to over-regulation or to the establishment of excessively restrictive environmental exposure limits.

The risk management process in Canada is considerably more open to informal information exchange between stakeholders during the various steps of the process, in contrast to the United States�where the risk assessment step for environmental hazards has been isolated from the later steps by statutory or administrative restrictions on information flow. However, the United States government is now actively pursuing regulatory reform by moving gradually towards a more flexible and better interconnected risk management system.

RESEARCH RISK ASSESSMENT RISK MANAGEMENT

Laboratory and Field Observations

Information on extrapolation methods

Toxicity assessment: hazard identification and dose-response assessment

Field measurements, characterization of populations

Research needs identified from risk assessment process

Exposure assessment; Emissions characterization

Development of regulatory options

Agency decisions and actions

Evaluation of public health, economic, social, political consequences of regulatory options

Risk Characterization

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To a limited extent, such changes are already taking place. For example, the 1993 Executive Order 12866 has proposed a new regulatory plan which establishes principles concerning the analysis of risks, benefits, and costs of revised environmental regulations. The new regulatory plan would alter the current methodology for risk to allow for the economic evaluation of risks, benefits and costs within the risk assessment process. This marks a major policy shift, in that it reduces the �separation� between risk assessors and risk managers within the U. S. regulatory system.

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We often incur risk as the inevitable consequence of making decisions with incomplete and uncertain information. It is relatively easy to make decisions about risks in situations where reliable information is at hand and there is minimum uncertainty. In these circumstances, the likelihood of making a wrong decision is small. Unfortunately, decisions about many aspects of environmental health must be made under conditions of considerable urgency, where there is insufficient time to completely investigate a problem and perform an exhaustive analysis of available options. So it is not uncommon for risk assessors and risk managers to find themselves in situations where quick responses to rapidly unfolding environmental threats must be made with minimal information and large degree of uncertainty. Even in problem situations where months or years are available for further investigations, the necessary information will never be entirely complete or totally unambiguous. Risk managers must always be prepared to make hard decisions under uncertainty. A maxim in risk management states that: �not to decide is to decide��in other words, deferred decisions constitute implicit acceptance of the status quo, including the health risks and adverse outcomes that may result from the decision not to act. On the other hand, precipitate action may introduce new hazards as the result of substitution of an agent with known risks by another agent with uncharacterized, potentially greater, risks. In the longer term, further research and analysis can undoubtedly reduce ignorance and uncertainty, but deferring crucial health protection decisions to a later point in time may lead to disaster. This dilemma is exemplified by the tragic outcomes of the HIV blood transfusion problem in Canada and elsewhere, the �Mad-Cow� disease outbreak in the U.K., and the seemingly pervasive health problems associated with environmental contaminants�for example, asbestos, heavy metals such as mercury and lead, or organochlorine compounds such as PCBs and dioxins.

Recently, the report of the Presidential /Congressional Commission on Risk Assessment and Management (1997) has proposed the use of stakeholder involvement: �Involvement of stakeholders �parties who are concerned with or affected by the risk management problem�is critical to making and successfully implementing sound, cost-effective, informed risk management decisions.�

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�������������������������� The weight-of-evidence concept constitutes a foundation for risk decision-making under uncertainty, because it allows risk managers to assess the credibility of conflicting evidence about the harmful properties of an environmental contaminant in a systematic and objective manner. In order to ensure that the process of weighing the evidence is scientifically defensible, the weight-of-evidence concept requires that the available evidence is of sufficient strength, coherence, and consistency to support an inference that a serious hazard may exist. Hence, the weight-of-evidence assessment is an ongoing activity where new scientific evidence will be continually incorporated within the decision framework as it becomes available. This process can be frustrating to risk managers because earlier conclusions about a potential hazard supported by existing evidence can later become less convincing, whenever new evidence contradicts the scientific underpinnings of a decision previously taken. Another source of frustration is the inability of such inference processes to achieve a final irreversible decision with a high degree of confidence in its correctness. There is a natural desire among risk managers for achieving �closure� in risk decision-making, so that controversial issues in environmental health protection can be resolved once and for all on the basis of compelling scientific evidence. Unfortunately, it is the fate of most environmental contaminants to be subjected to repeated cycles of risk assessment and risk management review over many years or decades. While expensive and time consuming, such a periodic reappraisal of scientific evidence helps to ensure that risks are managed in accordance with the best available scientific information.

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Risk managers tend to rely on several broad principles of risk decision-making which may become explicitly stated as a formal regulatory policy for a health protection organization. Or they may play a less visible role in the day-to-day subjective judgements of individual decision-makers and decision-making bodies. The risk management process relies on two major operating principles to accomplish its health protection mission under conditions of incomplete and uncertain information. These two principles�the Precautionary Principle and Sound Science�represent a pair of conceptual anchors placed at opposite ends of the spectrum of possible decisions. The Precautionary Principle impels decision-makers towards action in situations where a serious or irreversible health hazard is believed to exist as a possibility, although the exact probability of the suspected hazard is imperfectly understood. The principle of Sound Science seeks to restrain decision-makers from attempting premature or fallacious judgements about hazards which may not constitute meaningful threats

Association and causality While risk assessment and management of discrete hazards, such as manufacturing processes within industrial facilities or the transportation of dangerous goods, is itself a difficult and complex undertaking, at least the major causal linkages between a potential hazard and its associated risks to health safety are visible, concentrated in one locality, directly quantifiable, and reasonably well understood. In contrast, environmental contaminants represent hazards that are diffuse, mobile, not easily quantifiable, and often poorly understood. Another major obstacle in establishing the causal linkages for the harmful health effects of environmental contaminants arises from the need to account for the impact of other causal agents such as smoking, radiation, and natural toxins, which can also cause ill health, either separately, or sometimes in combination with manufactured chemicals or their by-products. Moreover, there are usually large gaps in time between an exposure to a contaminant, the observation of possible ill effects, and a medical or scientific assessment about association and causation. Therefore the risk assessment and management of hazardous environmental contaminants usually requires the use of weight-of-evidence methods for determining the nature and extent of population health risks, relying on scientific inferences derived from studies both in exposed human populations and in test animals exposed in toxicological studies.

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to human health. It requires that the decision to act should be based on a reasonable probability of harm. Ideally, both principles would guide the decision-maker towards a middle ground, where the majority of substantial risks are effectively addressed and the majority of insignificant ones are dismissed. Frederick the Great of Prussia is quoted as exclaiming during the Seven Years War that: �He who would defend everything defends nothing.� Deciding what to defend and not defend is an essential task of risk decision-making.

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The Precautionary Principle states that personal health is an irreplaceable human good, and asserts that protection of public health should be treated as the paramount concern for regulatory organizations and governments. All other concerns, such as cost of control or adverse economic impact, would then be accorded secondary importance in public health policy, although consideration of the cost-effectiveness of the proposed control measures necessarily need to be considered.

In order to protect the environment, the precautionary approach shall be widely applied by States according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation. UNCED Rio Declaration - Principle 15

In Canada, the Precautionary Principle is broadly supported as an important guiding concept by most regulatory bodies at the provincial and federal level, but is often interpreted in a more narrow sense than the original Rio Declaration. For example, according to a recent definition developed for Environment Canada under the CEPA regulations, the Precautionary Principle should consist of four operative rules:

• the primary objective is minimization of harm to human health

• appropriate remedial and preventive actions shall not be postponed by the presence of uncertainty

• evaluation of evidence shall be based on adherence to sound science

• decision-making shall include a careful consideration of the cost-effectiveness of any proposed course of action

Decisions that require sound scientific evidence of harm are often seen as operating according to the �weak� or �utilitarian� Precautionary Principle. In contrast, the �strong� or �ecocentric� Precautionary Principle tends to emphasize the need for environmental protection even in the absence of convincing evidence. The distinction between

The Precautionary Principle, as stated in the historic Rio Declaration, contrasts sharply with existing regulatory policy in many countries. For example, in the United States, many of the legislative provisions for regulating environmental hazards require that the legal burden of proof to enact more restrictive controls over pollutants rests with the regulatory body, not the industry that emits the pollutant. Under this system, those regulatory actions not supported by convincing scientific evidence of a potential health risk accompanied by a well-demonstrated need for stricter emission controls, are likely to be overturned in the federal courts (e.g. rejection of the 1996 EPA proposal for a revised air quality standard for particulate air pollutants). Conversely, in the European Union, application of the Precautionary Principle is accorded official status within the EU Environment Health Policy, and is incorporated into the environmental laws of several of the member states.

The Precautionary Principle has become a declared policy issue for an increasing number of risk management deliberations within Canada in recent years. For example, the 1993 Comprehensive Air Quality Management Framework for Canada, agreed to by federal, provincial and territorial governments through the National Air Issues Coordinating Committee (NAICC), includes the precautionary principle among its list of principles of cooperation. The Framework provides that: "Preventive and corrective actions will be based on the precautionary principle, sound science, and consistency with nationally acceptable data and assumptions".

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�weak� and �strong� is basically one of values, where strong precaution favours more protection with less evidence and weak precaution favours more evidence before protective decisions are made. The Precautionary Principle is most appropriately applied in the early stages of an unfolding risk problem, when the potential for serious or irreversible health consequences is great but the likelihood of occurrence is uncertain. In such cases, responsible risk managers may formulate a reasonable worse-case scenario and act expeditiously to provide interim controls to minimize the likelihood of anticipated harmful consequences, until better information becomes available at a later time. This cautious policy approach to health risk is generally termed conservatism. Many conservative assumptions are included in a typical risk assessment process, and all are inherently biased toward a more pessimistic interpretation. Initially, the worst possible outcome across a spectrum of uncertain contingencies is carefully considered. As more credible information becomes available, the pessimism of these conservative assumptions can usually be discarded as unlikely, or redefined in a less pessimistic manner. Hence, preliminary risk estimates for environmental hazards tend to be quite high, but many will tend to diminish over time as better quality data become available. Numerous conservative assumptions are purposely built into most risk assessment methods, both to ensure public safety, and to encourage the collection of better scientific data by organizations who wish to see risk estimates adjusted downward, with a corresponding relaxation of the more stringent environmental standards. However, many business people in various regulated sectors of the economy remain concerned that routine application of compounded conservatism within the risk assessment process�always assuming the worst in every instance where information is lacking or unclear�could result in significant overestimation of health risks, thereby keeping many environmental standards at excessively restrictive levels.

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The principle of Sound Science requires that an observed pattern of events should not be accorded causal significance unless confirmed by careful data collection and thorough statistical analysis. The Sound Science requirement serves as the foundation of all of our modern experimental sciences, because it ensures that misguided ideas arising from chance occurrences, biased data collection, flawed experimental design, or defective analysis will be rejected. Sound scientific ideas based on confirmed observations from systematic experimental studies will eventually be accepted, although it may require a longer time to reach a firm conclusion.

Some environmental advocacy groups assert that the ecocentric version of the Precautionary Principle should be more strictly followed, regardless of cost, through the wholesale restructuring of modern society to emphasize environmental health over industrial productivity. Such a position is only defensible if one accepts the severe strains on society that would result from this policy. However, a more balanced application of the Precautionary Principle can also be adopted, if risk assessment methods are used to quantify the health risk associated with a particular environmental hazard, and risk management procedures are used to efficiently apportion societal resources to address those hazards presenting the greatest risk. In this sense, risk assessment and management methods should not be viewed as antithetical to the Precautionary Principle�rather the risk paradigm attempts to define the criteria under which the Precautionary Principle can be effectively applied to regulatory decision-making.

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PRECAUTIONARY PRINCIPLE, SCIENCE, AND RISK ASSESSMENT Some commentators on the Precautionary Principle view it as separate from, and even antithetical to, science. Hathcock, for example, has said the Precautionary Principle can "negate the input of science" and "overrule risk assessment," and allow "arbitrary" food safety decisions whenever there is any uncertainty about a risk. � Summing up, at the start of this section I cited the view that precaution is antithetical to science. The opposite is in fact true, and we must avoid the misleading implications of the perceived dichotomy between "science" and "precaution." Precaution is grounded in scientific analysis, and applying precaution to decisions requires rigorous scientific input from a range of disciplines. At times, precautionary approaches, with their emphasis on what science does not know as well as what is known, may in fact require more rigorous science than risk assessment, which has been known to brush aside uncertainties in order to answer too narrowly-drawn questions. Hathcock's quote could be turned around: Risk assessment can also be used to "overrule" science-based precautionary judgments. But neither scenario represents sound decision-making. Done properly, Risk Analysis uses risk assessment and precaution together, as inseparable and essential components of science-based decision-making. Science, Precaution, and Food Safety, Groth (2000)

Sound Science adheres to the concept of empirical conservatism, which is entirely distinct from the policy conservatism inherent in the Precautionary Principle. It is not surprising that research scientists and risk managers frequently miscommunicate their underlying assumptions, since both invoke conservatism in their professional judgments, but in opposite directions. Neither type of conservatism is inherently wrong, but simply different. In empirical science, where nature is studied without reference to policy consid-erations, empirical conser-vatism attempts to minimize the likelihood of �false alarms�, but accepts that a limited number of real effects may therefore go undetected for a substantial period of time. In mandated science, which informs deci-sion-making in the public health arena, policy conser-vatism attempts to ensure public safety by assuming the worst-scenario in uncer-tain situations�policy con-servatism can thus occasionally fall prey to the �Chicken Little� syndrome: �the sky is falling, and we must see the King.�

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ALARA stands for �As Low as Reasonably Achievable��a concept which asserts that environmental exposure to toxic substances should be kept as low as is reasonably achievable, using pollution control equipment and industrial processes that can be installed and operated at reasonable cost. The ALARA Principle thus occupies a broad middle ground between the mutually opposing constraints of the Precautionary Principle and Sound Science. Thus, an acceptable risk would conceivably be ensured by adopting reasonably achievable control measures which balance risks and benefits. In many jurisdictions, including Canada, the ALARA Principle is frequently applied in formulating exposure guidelines or regulatory limits for environmental hazards. In practical terms, the question of defining �acceptable risk� and �reasonably achievable� must somehow be resolved. Environmental risk management practices were initially developed under the

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assumption that the public could be entirely protected from all risk, and consequently, that no level of risk was acceptable. With the advent of progressively more sensitive means of detecting miniscule quantities of environmental contaminants, and with the realization that small exposures to carcinogenic agents may entail some possible risk, the present goal of risk management is to reduce risk to the maximum extent deemed possible by practical considerations.

The ALARA principle generally uses the word �low� to denote low exposure, which is believed to correspond in a general way to a lower health risk, although this relationship is not necessarily quantifiable in all cases. Reasonable cost of control is evaluated largely through technological criteria, such as best available control technology (BACT) or best practicable control technology (BPCT), although in recent years more consideration has been given to the balancing of costs and benefits. Some industries feel it is unreasonable to expect continual upgrading of environmental control technologies when the corresponding reduction in health risks remains questionable, or where persuasive evidence of a reasonable relationship between costs and benefits of risk reduction is absent. In practice, the ALARA principle is most readily applicable in large-scale or high-technology industries, such as the manufacture of plastics and specialty chemicals, where environmental control technology is constantly being upgraded as new equipment and processes are introduced. Because installing new equipment can, with relatively minimal expense, incorporate recent technological improvements to reduce emissions of hazardous substances, the cost of environment control is partly covered within the capital expenditure budget dedicated to increasing productivity. The ALARA principle works less well in low technology sectors or in smaller industries, where there is a slower turnover of capital equipment and where industrial processes are relatively unsophisticated. In the latter case, sectoral approaches, encompassing a group of related small- and medium-sized industries, may enable more effective use of the ALARA approach.

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A more recent concept called the Reasonable Relationship approach has proposed that the costs of control for environmental hazards should

'Acceptable' levels of environmental hazards vary with the specific application and substance being considered and, in principle, should be as low as reasonably achievable, taking into account not only the hazard but also the social and economic benefits and the available technology (the ALARA Principle). �For chemicals, the ALARA Principle is applied in setting the guidelines or legal limits for the risk, which thus constitutes the 'acceptable' risk. As a consequence of the adherence to ALARA, the 'acceptable' risk varies from application to application. Health Canada, 1998

Total Risk

(A) Intolerable region

(B) As Low As Reasonably Achievable (ALARA). Risk is acceptable only if a compensating benefit is available.

(C) Broadly Aceptable Region. No need for detailed work to demonstrate ALARA.

Risk cannot be justified on any grounds.

Tolerable only if risk reduction is impractical or if its costs are grossly disproportionate to the benefits gained.

Tolerable if cost of reduction would exceed benefits gained

Negligible risk.

ALARA � Framework for Risk Criteria

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bear a �reasonable relationship� with respect to the corresponding reductions in health risk. The approach does not strictly require that the health benefits of risk reduction must match or outweigh the costs of control, but it asserts that the balance of costs and benefits should at least approximate each other. This approach requires a risk assessment to estimate the expected reduction of the health risk, and a socioeconomic analysis to estimate the associated cost of control. If the anticipated costs and benefits are deemed in reasonable relationship, either by formal calculations such as cost-benefit analysis, or by informal consensus among stakeholders, then the proposed protective measures would be implemented.

Under the ALARA Principle, acceptable risk is commonly defined as a lifetime risk which is so small as to be considered 'essentially negligible' by most people. A quantitative criterion of one in a million (10-6) for acceptable risk, often termed the de minimis risk level, has been adopted in many jurisdictions, most notably the United States, where it is routinely applied for regulating carcinogenic chemicals in the environment. More recently, it has become apparent that one in a million risk is a very stringent criterion in situations where relatively few people are exposed. As a consequence of conforming to the ALARA Principle, the definition of a negligible risk (not necessarily as stringent as de minimis risk) may vary from case to case, depending on the practical limitations for controlling each regulated substance.

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SUGGESTED READINGS Barnard, R.C. (1987). Scientific risk assessment and the regulation of human cancer risks: background and new directions. Am Ind Hyg Assoc J 48:798-803.

Barnard, R.C. (1994). Scientific method and risk assessment. Regul Toxicol Pharmacol 19:211-8.

Barnard, R.C. (1995). Risk assessment: the default conservatism controversy. Regul Toxicol Pharmacol 21:431-8.

Barnes, D. (1994). Times are tough - brother, can you paradigm? Risk Anal 14:219-223.

Brunk, C., Haworth, L., Lee, B. (1991). Value Assumptions in Risk Assessment: A Case Study of the Alachlor Controversy. Waterloo, ON: Wilfrid Laurier University Press.

Canadian Standards Association (1997). CAN/CSA-Q850-97. Risk Management: Guideline for Decision-Makers. Etobicoke (Toronto), Canada: Canadian Standards Association.

Commission of the European Communities (2000). Communication from the Commission on the Precautionary Principle. Brussels.

De Rosa, C.T., Stevens, Y W., Johnson, B.L. (1993). Cancer policy framework for public health assessment of carcinogens in the environment. Toxicol Ind Health 9:559-75.

De Rosa, C.T., Pohl, H.R., Williams, M., Ademoyero, A.A., Chou, C.H., et al (1998). Public health implications of environmental exposures. Environ Health Perspect 106:369-78.

Dyck, W., Del Bel Belluz, D., Craig, L. (1998). Current Directions in Environmental Risk Assessment and Management. Waterloo, Canada: Network for Environmental Risk Assessment and Management (NERAM).

Environment Canada (no date). Tabs on Contaminated Sites #15: Risk assessment principles and screening processes. Environment Canada - Ontario Region, Environmental Protection Branch.

Environment Canada, Health Canada (1996). CEPA review: The government�s response. Ottawa.

Goldstein, B.D. (1999). The precautionary principle and scientific research are not antithetical [editorial]. Environ Health Perspect 107:A594-5.

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Gori, G.B., Flamm, W.G. (1991). How sick a patient? Report of a workshop on cancer risk assessment. Regul Toxicol Pharmacol 14:215-22.

Gray, J., Brewers, J. (1996). Towards a scientific definition of the precautionary principle. Marine Pollution Bulletin 32:768-771.

Groth, E. (2000). Science, Precaution and Food Safety: How Can We Do Better? Yonkers NY: Consumers Union of U.S.

Harrison, K., Hoberg, G. (1994). Risk, Science, and Politics: Regulating Toxic Substances in Canada and the United States. Montreal: McGill-Queen�s University Press.

Health Canada (1990). Health risk determination: The challenge of health protection. Ottawa: Health Protection Branch.

Health Canada. (1997). Health and environment, partners for life: Assessing and managing health risks, pp. 32-48. Ottawa.

Health Canada (1998). The health and environment handbook for health professionals: Chapter 2. Risk. Ottawa.

Jarabek, A.M., Farland, W.H. (1990). The U.S. Environmental Protection Agency�s risk assessment guidelines. Toxicol Ind Health 6:199-216.

Joint Committee on Health and Safety, Royal Society of Canada, Canadian Academy of Engineering (1993). Health and Safety Policies: Guiding Principles for Risk Management. Waterloo, ON: Institute for Risk Research.

Joint Working Group � Health Canada, Atomic Energy Control Board, Ontario Ministry of the Environment (1998). Assessment and management of cancer risks from radiological and chemical hazards. Ottawa.

Kates, R.W. (1994). Sustaining life on the earth. Scientific American Oct;271(4):114-22.

Krewski, D., Birkwood, P. (1987). Risk assessment and risk management. Risk Abstracts 4:53-61.

Krewski, D., Slovic, P., Bartlett, S., Flynn, J., Mertz, C. (1995). Health risk perception in Canada II: Worldviews, attitudes, and opinions. Human & Ecological Risk Assessment 1:231-248.

McClellan, R.O. (1994). A commentary on the NRC report �Science and judgment in risk assessment.� Regul Toxicol Pharmacol 20:S142-68.

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McClellan, R.O. (1999). Keynote Address: Human Health Risk. Assessment: A Historical Overview and Alternative Paths Forward. Inhal Toxicol 11:477-518.

Morgan, M., Henrion, M. (1990). Uncertainty: A Guide to Dealing with Uncertainty in Quantitative Risk and Policy Analysis. New York: Cambridge University Press.

National Research Council (1983). Risk Assessment in the Federal Government: Managing the Process. Washington DC: National Academy Press.

National Research Council (1994). Science and Judgment in Risk Assessment. Washington, DC: National Academy Press.

National Research Council (1996). Understanding Risk: Informing Decisions in a Democratic Society. Washington, DC: National Academy Press.

Omenn, G.S. (1995). Assessing the risk assessment paradigm. Toxicology 102:23-8.

Patton, D. (1994). The NAS risk paradigm as a medium for communication. Risk Analysis 14:375-378.

Paustenbach, D. (1995). Retrospective on U.S. Health Risk Assessment: How others can benefit. Risk: Health, Safety, and Environment 6:283-332.

Power, M., McCarty, L. (1998). A Comparative Analysis of Environmental Risk Assessment/Risk Management Frameworks. Environ Sci Technol 32:224A-231A.

Presidential/Congressional Commission on Risk Assessment and Risk Management (1997). Framework for Environmental Health Risk Management, Final Report, Volume 1: Washington DC.

Presidential/Congressional Commission on Risk Assessment and Risk Management (1997). Risk Assessment and Risk Management in Regulatory Decision-Making. Final Report. Volume 2. Washington DC.

Rodricks, J.V. (1994). Risk assessment, the environment, and public health. Environ Health Perspect 102:258-64.

Schierow, L. (1998). The role of risk analysis and risk management in environmental protection. Washington: Congressional Research Service.

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Thomas, S., Hrudey, S.E. (1997). Risk of Death in Canada: What We Know And How We Know It. Edmonton: Alberta University Press.

Tickner, J. (1999). A map toward precautionary decision making. In Protecting Public Health and the Environment: Implementing the Precautionary Principle. Ed. J. Tickner, Washington, DC: Island Press.

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