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Risk communication between risk
assessors and managers1


Joseph V. Rodricks, Ph.D., is a Principal of Environ International Corporation,
Life Sciences Group (Arlington, Virginia, United States) and a Visiting Professor
at The Johns Hopkins University School of Public Health.

An understanding of the potential risks to human health posed by exposures to food contaminants is a central component of the process involved in establishing health protective standards. Thus, risk managers - those with the responsibility for establishing and implementing such standards - are required to engage in a dialogue with risk assessors, and to extract from that dialogue a firm grasp of what scientific evaluation can and cannot reveal about the risks associated with specific exposures. Because most risk assessments involving chemical toxicity and microbial pathogenicity are beset with scientific uncertainties, and because the nature of these uncertainties varies among different chemical and pathogenic agents, a general understanding of the risk assessment process, while important, is not adequate to support informed decision-making in specific cases. A dialogue between risk assessors and managers regarding the nature of and justification for the scientific analysis supporting specific risk results is essential if risk information is to be used in ways that are consistent with scientific understanding and its limits.

Risk managers are burdened with many other difficult tasks. When dealing with food contaminants, they need to consider factors other than health risk - the availability of technical means to reduce risk, the consequences for food supply of any actions taken, public perceptions and desires, and even the possibility of unintended and offsetting reductions in health benefits. Each of these considerations can and should be supported by additional technical ana-lyses, and a systematic and transparent methodology should be applied to integrate these considerations and the risk information to arrive at risk management decisions.

Unfortunately, the difficult task of risk management does not end with a decision, but usually involves the responsibility for explaining the basis for the decision to various affected parties (many of which will have contributed to the decision-making process). At the least this involves an exposition of how adequate safety criteria have been met.

Substantive, open communication is essential to the successful completion of every phase of the risk management process, and decisions emerging from this process will gain creditability in direct proportion to the care with which communication has been encouraged and managed. In this brief discussion of the topic, communications between risk assessors and managers, and between technical analysts and the lay public, will be emphasized, but it should be kept in mind that many other types of dialogues are involved in risk management de-cisions (Slovic et al., 1980).

All parties involved in the process of developing risk-based decisions are in some sense concerned about the ultimate consequences of these decisions; they are thus tempted to influence communi-cation in ways that favour their preferred outcomes. That risk communication can be impeded because of the introduction of extraneous concerns (sometimes in the guise of legitimate concerns) is well recognized, and probably unavoidable. Conscious awareness of the existence of such potentially impeding factors in ourselves and others, and constant efforts to engage in clarifying dialogue, are perhaps the only feasible means to avoid the undue influence of such factors. Figure 1 lists some typical impediments to risk communication.

Risk assessors and risk managers

Scientists prefer to communicate with other scientists in their own disciplines, and are often hesitant to explain their work to non-scientists, or even to scientists in other disciplines. Explanations of the methodology and results of risk assessments in ways that do not distort scientific understanding and that are also useful to an audience of non-specialists are especially problematic, because they require explicit discussion of the bases for choosing among different sets of toxicity and dose-response data. Even more difficult are explanations for dealing with extrapolations across species and with variability in response among species and among humans. Risk assessment involves the use of certain assumptions to deal with variability and other uncertainties; most are not fully supported by scientific evidence, and so are categorized as "science policy" choices, more commonly known as choices made by "default". Such choices are, however, different in kind from those policy choices concerning, for example, risk acceptability, which are components of the risk management process instead (see Figure 2). Unless these distinctions are understood, managers may believe that assessors are encroaching upon their territory when they apply default assumptions. In ad- dition, dialogue is essential if managers are to grasp the scientific meaning of various risk results, whether the issue is tolerable daily intakes (TDIs) or the like for non-cancer effects, or cancer-potency factors (low-dose cancer-risk estimates per unit of dose) for carcinogens (Finkel, 1990).


Some impediments to risk communication

Risk assessors

Risk managers

The public and various
interest groups

  • are reluctant to reveal scientific limitations;
  • may sometimes confuse science and policy.
  • are reluctant to acquire all the necessary understanding of science;
  • are uncomfortable admitting to the acceptance of any risk;
  • may be excessively concerned about political repercussions.
  • may not trust science and policy-makers;
  • find that costs of compliance are irrelevant to some and highly relevant to others.

And everyone is influenced by perceptions that do not match the technical understanding of risk (see section on Risk perception and risk communication in the text).


The relative roles of science and policy in protecting people
from risks of chemical toxicity


Risk assessment

Risk management

How should knowledge be acquired?
What do we know and how well do we know it?

How should acquired knowledge be interpreted to understand risks?
What don't we know?

What means are available to reduce risks?
How effective are they? What are the costs?
Will they introduce other risks?

What knowledge should be acquired and who should pay?

What should be done when scientific knowledge is lacking?

How much risk reduction is necessary?
What other factors should influence the decision?
What means for reducing risk should be adopted?

* The National Research Council (1994) distinguished “risk assessment policy” from “risk management policy”. The former involves the selection of various assumptions and models to deal with uncertainties in the risk assessment process (these are the “default” choices). Risk management policies are different in nature. - Source: Rodricks, 2001.

Risk assessor-manager dialogue: some examples

It is useful for managers to acquire a grasp of what might be called the "anatomy" of specific risk assessments. Some of the useful anatomical characteristics of risk assessments for the effects of non-carcinogenic agents, generally assumed to act only when exposures exceed a threshold dose, are listed in Box 1 and illustrated in Figure 3. For the effects of carcinogenic agents, which may not obey threshold rules, see Box 2. Indeed, managers would be advised to seek out this type of information, on a substance-specific basis, through direct dialogue with risk assessors.

One aspect of the information shown in Boxes 1 and 2 that has been insufficiently discussed concerns the appropriate methods for characterizing human exposures to food contaminants. The risk assessment process for threshold agents leads to an estimate of a lifetime daily intake that is likely to be protective (i.e. to represent a threshold dose) for the most sensitive members of the human popu-lation (see Figure 3). To assess risk for such an agent it is necessary to understand whether, and to what extent, exposures to such an agent exceed the estimated threshold dose. The best approach to the latter evaluation requires the development of sufficient data to estimate the distribution of such exposures within the population. Having this type of infor-mation allows: 1) estimation of the fraction of the population with exposures that exceed the threshold; and 2) estimation of the effects on the exposure distribution that would result from the imposition of various maximum limits (MLs) for the agent in food. Similar analyses may be made for carcinogens, based not upon the criteria of exceeding the threshold, but rather on the criteria of the magnitude of the risk reduction achieved.

Much could be gained were it possible to estimate accurately the probability (which, in most cases, would be extremely small) that individuals at the "high end" of contaminant exposure were also at the "high end" of susceptibility to toxic effects. Such certitude could assist in defining protective tolerance levels that did not place undue weight on extremely unlikely exposure/risk scenarios. Scientific methodologies for gaining such knowledge are under study, but are perhaps not ready for routine application.


What do risk assessors need to tell risk
managers about threshold effects?


  • the strength of the scientific evidence that contaminant x causes health effect y;
  • a clear assessment regarding derivation and meaning of TDI (see Figure 3);
  • the relative influence of both data and assumptions;
  • the basis for deviations from standard assumptions (defaults) in derivation;
  • major scientific limitations and disagreements.


  • the distribution of chronic exposures in population, without and with the imposition of tolerances;
  • a clear assessment of derivation of distribution;
  • risk of exposure from non-food sources, if any;
  • major scientific limitations and disagreements.

Carcinogenic risks

Explicit recognition of risk is a feature of low-dose risk assessment for carcinogens, together with the concept that the only no-risk condition is when there is no exposure (Box 2). Because exposure avoidance is possible only in the case of intentionally introduced ingredients in food, decision-making for unavoidable contaminants requires both acknowledgement of and some tolerance for risk. Most decision-makers would prefer not to be placed in such circumstances, for understandable reasons. They are offered some comfort when told by risk assessors that low-dose risk estimates are "upper bounds" on actual risk (because actual risks cannot be predicted), and that "actual risk may be zero". But they are nevertheless required to admit to the possibility that some small risk may exist at contaminant intake levels which they have selected as acceptable.


What do risk assessors need to tell risk managers about carcinogenic risks predicted through low-dose extrapolation?

  • Extrapolation can be carried out from either human or animal data; the strength of evidence of carcinogenicity should be discussed.
  • Extrapolation yields upper bound on lifetime risk: actual risk is likely to be lower, and may even be zero.
  • It is not clear whether estimated low-dose risk for a given exposure represents the "most sensitive" members of the risk distribution.
  • While the risk for a given exposure will be the same for all individuals, risk will vary among individuals according to their lifetime average intakes.
  • Ideally, knowledge of contaminant intake distribution is used to estimate distribution of population risks (number of people at risk times risk per individual).

Analysis of the following characteristics of risk-based decision-making may assist risk managers in dealing with this difficult problem.


Towards conceptual clarity regarding the meaning of
acceptable daily intake (ADI) and tolerable daily intake (TDI)


- Typical derivation of TDI/ADI from animal data: factor of 10 for animal-human extrapolation, and factor of 10 for "average" to "sensitive" extrapolation within human population (note: factors other than 10-fold often used).
-The fraction of the human population that might be at risk below a derived ADI/TDI, while almost certainly very small, cannot be proven to be zero. Thus, it is not possible to claim that ADI/TDI is "absolutely safe". Development of a contaminant intake distribution would reveal the fraction of the exposed population that falls within the zone of potential risk (i.e. near or above the ADI/TDI).
- The effectiveness of various MLs in shifting intake distributions toward safer zones can be evaluated for purposes of risk management decision-making (note: the exposure distribution averaging time must match the averaging time upon which the ADI/TDI is established).

Risk perception and risk communication

Notwithstanding the advantages of risk-based decision-making, it is clear from much research in social psychology that most people do not think of risk in terms of probabilities, but focus on the other attributes of a risk. Thus, it is possible, with some simplification, to categorize risks as "tolerable" or "non-tolerable" to people, irrespective of any objective measure of probability (Table 1). These other attributes appear to be far more important to most people (possibly including risk managers) than do the measures of risk provided by risk assessors. These varying degrees of risk toleration need to be considered by risk managers (and most managers sense their existence intuitively) when their decisions are offered for public consumption. Note that food contaminants, to which people are exposed involuntarily and from which they derive no benefit, especially those that are carcinogenic and are of industrial origin, generally pose risks of the highly "non-tolerated" type, so that communication of risk decisions regarding them is exceedingly troublesome.

It is interesting to note that many of the very large risks people face - from smoking, excessive caloric intake and inadequate caloric expenditures, other unhealthy dietary habits, excessive alcohol consumption, automobile accidents - tend to have attributes of the "tolerable" type, and public health officials find themselves seriously challenged when they seek ways to reduce these large risks. Those required to manage the many thousands of small risks of the "non-tolerable type" face a completely different challenge. It is to be recommended that several of the available guidance documents on this topic, which are listed in the bibliography, be given study by anyone involved in risk communication (Rodricks, 2001).

Pesticides being applied to tomato plants. Pesticides are used in accordance with good agricultural practice to reduce risk - FAO/19436/A. Conti

Although an understanding of risk perception is important in the communication process, it should nonetheless be only a minor part of formal risk management decision-making. Such decision-making will be most successful if it is based to the maximum extent possible on technical analyses, and if it avoids significant reliance upon subjective factors, such as those listed in Table 1, because their relative influences vary widely among individuals. Only when decisions rest primarily on technical analyses, communicated openly among all parties involved, is it possible for risk managers to offer credible explanations for them; without that possibility decisions will not easily find broad acceptance.


Subjective attributes of risks that influence public perceptions



voluntarily assumed

imposed by others

of high personal benefit

of no perceived personal benefit

scientists agree

scientists disagree

not catastrophic


natural in origin

industrial in origin

not fearsome

highly dreaded

common event

rare event

equitably distributed

not equitably distributed

* “Tolerable” risks are those that people tend to find less threatening than intolerable types, irrespective of the magnitude of the risk (Slovic et al., 1980).

1 This article is based on a presentation at the Joint FAO/WHO Seminar on Risk Analysis of Contaminants, held in Rotterdam, the Netherlands,10 March 2002.
2 Variability among species and individuals within species is a fact of nature, and must be dealt with in every risk assessment. The fact of variability is scientifically certain; its magnitude in specific circumstances (e.g. the variability in response among humans to a specific level of methylmercury exposure) is highly uncertain. Risk assessors have adopted so-called "default assumptions" to deal with uncertainties; these are based in part upon scientific knowledge but also include an element of caution.
3 Only in the trivial cases in which it is possible to ban a substance completely is absolute safety assured.
4 Adoption and enforcement of MLs can do much to reduce the "high end" of cancer risk distributions for individuals (i.e. MLs can be set so that no individual is expected to incur risks from carcinogen exposure greater than, say, 10-5/lifetime). But an analysis of how exposure distributions shift by imposition of an ML will generally reveal that such an imposition will do very little to the exposures incurred by the vast majority of a population. Thus, population risks will be affected very little by imposition of an ML. Only contamination prevention will significantly affect population risk.


Finkel, A.M. 1990. Confronting uncertainty in risk management. A guide for decision-makers. Washington, DC, Resources for the Future.

National Research Council. 1989. Improving risk communication. Washington, DC, National Academy Press.

National Research Council. 1994. Science and judgment in risk assessment. Washington, DC, National Academy Press.

Rodricks, J.V. 2001. Some attributes of risk influencing decision-making by public health and regulatory officials. Amer. J. Epi., Suppl. 154(12): S7-S12.

Slovic, P., Fischhoff, B. & Lichtenstein, S. 1980. Facts vs. fears: understanding perceived risk. In R. Schwing & W.A. Albers Jr, eds., Societal risk assessment: how safe is safe enough? New York, USA, Plenum Press. 374 pp.

summary résumé resumen

Risk communication between risk assessors and managers

FOOD SAFETY ISSUES may be particularly subject to controversy because of the unique role that food plays for individuals and in society. Among the barriers to public acceptance of food safety decisions are lack of public trust in regulatory agencies, ineffective and outdated methods of risk communication, and unequal access and funding for participation of all stakeholders in the debate leading to regulatory decisions. Applying participatory risk-communication strategies in the decision-making process of food safety risk analysis has been suggested as one way to decrease controversy and facilitate openness and transparency. A new paradigm has evolved that includes two-way communication throughout the risk analysis process. Specific guidelines have been elaborated in a series of three expert consultations on risk analysis and risk communications related to food safety, conducted by FAO and WHO, and are included in the article.A SUBSTANTIVE DIALOGUE between risk assessors and managers regarding the nature of and justification for the scientific analysis supporting specific risk results is essential if risk information is to be used in decision-making in ways that are consistent with scientific understanding and its limits. The need for risk managers to explain the bases for their decisions to the public and to various interest groups further underscores the value of such dialogue. Risk managers need not devote their time to in-depth explorations of the contents of specific risk assessments, but can derive large benefits if they focus on specific elements that are common to all risk assessments and that greatly affect outcome. This article provides guidance on specific elements of risk assessments that are useful for managers to grasp, concerning both the selection of toxicology data and appropriate uncertainty factors (or low-dose risk models), and the derivation of estimates of human exposures to the chemicals of interest. Of particular importance is an understanding of both quantitative and qualitative descriptions of risk, and of how both such descriptions can influence decision-making. Understanding the effect on risk reduction of various strategies to limit human exposures is also of importance, and is critical because efforts to limit exposures by the imposition of tolerances will, at some point, yield only marginal reductions in risk. Knowledge of the circumstances under which this phenomenon occurs can be of great value to decision-making. As they undertake communication with the public on the bases for their decisions, risk managers need to understand that they do not perceive risks in the same way as the public. Rather, individual perceptions are strongly influenced by certain risk attributes (e.g. whether voluntary or imposed, whether it is of natural or industrial origin) that risk assessors do not take into consideration in their work. Risk managers need to understand both technical risk assessment and the various influences on public perception of risk, and work to bridge the gap between them.

Communication des risques entre évaluateurs des risques et responsables de la gestion des risques

IL EST ESSENTIEL D'ASSURER UN DIALOGUE de fond entre évaluateurs des risques et responsables de la gestion des risques quant à la nature et à la raison d'être de l'analyse scientifique concernant des risques spécifiques, si l'on souhaite faire usage de l'information des risques dans le processus de prise de décisions, en accord avec les connaissances scientifiques et leurs limites. Un tel dialogue est d'autant plus important que les responsables de la gestion des risques doivent expliquer les fondements de leurs décisions au public, ainsi qu'aux différents groupes d'intérêts. Les responsables de la gestion des risques ne doivent pas consacrer leur temps à des études approfondies sur les évaluations de risques spécifiques, mais peuvent en tirer avantage s'ils se consacrent plus particulièrement à des éléments spécifiques communs à toutes les évaluations des risques, et qui influent fortement sur la prise de décisions finale. Cet article donne des conseils qui peuvent être utiles aux responsables, tant en ce qui concerne les éléments spécifiques d'évaluation des risques en matière de sélection de données sur la toxicologie et de facteurs d'incertitude appropriés (ou des modèles de risques à faible dose), que l'estimation des expositions de l'homme aux produits chimiques en question. La compréhension, aussi bien d'un point de vue qualitatif que quantitatif, des descriptions du risque, ainsi que de leur influence sur la prise de décisions, est d'une grande importance. Comprendre l'effet de différentes stratégies sur la diminution des risques, dans le but de limiter l'exposition de l'être humain au risque, n'est pas non plus négligeable. Cet aspect est d'autant plus important que les efforts visant à limiter l'exposition, par l'imposition de seuils de tolérance, finiront à un certain moment par n'entraîner que des réductions marginales des risques. Une bonne prise de connaissance des conditions dans lesquelles cela se passe peut se révéler d'une grande importance dans le processus de prise de décisions. Etant donné qu'ils se chargent d'informer le public des raisons de leurs décisions, les responsables de la gestion des risques doivent comprendre que la plupart des individus ne perçoivent pas les risques de la même manière que les évaluateurs. En fait, la perception individuelle du risque est fortement influencée par de nombreuses caractéristiques du risque (son caractère volontaire, ou son origine naturelle ou industrielle), qui ne sont pas prises en compte dans le travail des évaluateurs. Les responsables de la gestion des risques doivent comprendre d'une part les aspects techniques de l'évaluation du risque et, d'autre part, les différents éléments qui peuvent influencer la perception du public face au risque, et combler le fossé entre les deux.

Comunicación de riesgos entre los responsables de su evaluación y su gestión

ES ESENCIAL QUE HAYA UN DIÁLOGO SUSTANTIVO entre los responsables de la evaluación y gestión de los riesgos en lo que se refiere a la naturaleza y la justificación del análisis científico, que es la base de los resultados específicos en materia de riesgos, si se desea utilizar la información relativa a los riesgos en la adopción de decisiones de forma coherente con el conocimiento científico y sus límites. La necesidad de que los responsables de la gestión de riesgos expliquen las razones de sus decisiones al público y a diversos grupos de interés acentúa aún más el valor de ese diálogo. No hace falta que los responsables de la gestión de riesgos se dediquen a realizar estudios detallados del contenido de evalua-ciones de riesgos específicas, pero pueden sacar grandes beneficios si se centran en elementos que son comunes a todas las evaluaciones de riesgos y que tienen una gran influencia en el resultado. Este artículo proporciona orientación sobre elementos específicos de las evaluaciones de riesgos cuya comprensión resulta útil a los responsables de la gestión, y que se refieren a la selección de datos sobre toxicología y factores adecuados de incertidumbre (o modelos de riesgo de dosis bajas), y a las conclusiones que se derivan de la exposición de los seres humanos a los productos químicos de que se trate. También es de particular importancia entender la descripción cuantitativa y cualitativa del riesgo y la manera en que ambas pueden influir en la adopción de decisiones. Asimismo, es importante entender los efectos en la reducción del riesgo de diversas estrategias para limitar la exposición de los seres humanos. Este último aspecto es decisivo porque los esfuerzos para limitar las exposiciones mediante la imposición de niveles de tolerancia sólo originarán, en un momento dado, reducciones marginales del riesgo. Conocer las circunstancias en que esto se produce puede ser de gran ayuda en la adopción de decisiones. Al comunicarse con el público sobre las razones de sus decisiones, los responsables de la gestión de riesgos tienen que entender que la mayoría de las personas no perciben los riesgos de la misma manera en que suelen presentarlos los responsables de su evaluación. La percepción individual suele estar más bien fuertemente influenciada por muchos elementos del riesgo (por ejemplo, su grado de voluntariedad o si es de origen natural o industrial), que no se tienen en cuenta en la labor de los responsables de su evaluación. Los responsables de la gestión de riesgos tienen que entender tanto la evaluación técnica de los riesgos como los distintos aspectos que influyen en la percepción pública del riesgo, y tratar de colmar el vacío entre ambas.

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