Lessons from Preventive Medicine for the Precautionary Principle and Ecosystem Health

.

©2000 Blackwell Science, Inc.

Lessons from Preventive Medicine for the Precautionary Principle and Ecosystem Health

M.C. Calver

Biological Sciences, Murdoch University, Murdoch, Western Australia

ABSTRACT

Preventive medicine establishes clear links between dis-eases and their causes, therefore illness can be avertedor minimized by preventive measures. If this informationis widely dispersed through community education, it em-powers individuals to undertake decisions likely to im-prove their health. Significant cost savings are often possi-ble because preventive measures may be cheaper thancurative ones. In the case of ecosystem health, the pre-cautionary principle is analogous to preventive medicinebecause it argues for anticipatory action to protect theenvironment from possible serious or irreversible harm. Theprecautionary principle empowers people by involving

them in environmental decisions and has a clear need forcommunity education to encourage awareness and par-ticipation. It may also save society money in the long termby avoiding the costs of ecological rehabilitation. How-ever, the precautionary principle is fundamentally differ-ent from preventive medicine because it argues that ac-tion to protect the environment should be undertaken if acausal relationship is only suspected, not established. Thus,the analogy of preventive medicine and the precautionaryprinciple is valuable in highlighting this critical differenceand suggests that the precautionary principle will alwaysbe deeply contentious because of its focus on uncertainty.

INTRODUCTION

For many years, the Health Department of West-ern Australia has run an annual media “Quit”campaign to encourage smokers to break thehabit. The theme varies from the shocking to theinformative to the comical, but the central mes-sage of prevention and its influence on humanhealth is always clear. In 1999, a second healthmessage appeared in Western Australia’s dailypress. A group of local physicians ran advertise-ments claiming that management in Western Aus-tralia’s hardwood forests was making the forestsunhealthy and calling for reforms to prevent irre-trievable damage to ecosystem health. A centralmessage of the advertisements was the need forprecaution in environmental management. Theadvertisements were controversial, with some cor-respondence to the newspaper editor claiming

that physicians were unqualified to comment onthe environment. The exchange highlights themetaphor between human health on the onehand and ecosystem health on the other. It alsoinvites a specific comparison between preventivemedicine and the precautionary principle whichargues for anticipatory action to prevent environ-mental damage. One widely used definition is:

Where there are threats of serious or irrevers-ible damage, lack of full scientific certaintyshould not be used as a reason for postponingmeasures to prevent environmental degrada-tion. In the application of the precautionaryprinciple, public and private decisions shouldbe guided by: (i) careful evaluation to avoid,wherever practicable, serious or irreversibledamage to the environment; and (ii) an as-sessment of the risk-weighted consequences ofvarious options (The Intergovernmental Agree-ment on the Environment, May 1992, quotedin Deville & Harding 1997; p. 13).

Since its emergence in the last decade, the pre-cautionary principle has become a significant

Address correspondence to: M.C. Calver, Biological Sciences, Murdoch University, Murdoch, Western Australia 6150; E-mail [email protected].

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Ecosystem Health Vol. 6 No. 2 June 2000

force in environmental politics in Europe and thePacific (Calver

et al.

1999 and included refer-ences). Its emphasis on action before damage oc-curs establishes a clear conceptual link with pre-ventive medicine.

Several authors (e.g., Ehrenfeld 1995; Rap-port 1998) have already explored the humanhealth/ecosystem health metaphor, but detailedcomparative studies of preventive medicine andthe precautionary principle are lacking. This arti-cle compares and contrasts characteristics of theprecautionary principle with those of the estab-lished discipline of preventive medicine to high-light any lessons that preventive medicine cangive to the precautionary principle and the impli-cations of these lessons for ecosystem health. Thediscussion reveals that prevention and precautionshare a common concern for acting in anticipa-tion of adverse impacts, but prevention deals withestablished threats whereas precaution is con-cerned with threats that are poorly understood.Established scientific methodologies are alsomore readily accepted in studies of prevention. Asa result, precaution is always likely to be morecontentious than prevention in both humanhealth and ecosystem health. However, the em-phasis on prevention in medicine and on precau-tion in environmental matters suggests that pre-ventive medicine and the precautionary principlehave much to teach each other.

CHARACTERISTICS OF PREVENTIVE MEDICINE

HISTORY AND APPLICATIONS

Every bed on which the man with a dischargelies down shall be ritually unclean, and every-thing on which he sits shall be unclean. Anyman who touches the bed shall wash hisclothes, bathe in water and remain uncleantill evening. Whoever sits on anything onwhich the man with a discharge has sat shallwash his clothes, bathe in water and remainunclean till evening. If the man spits on onewho is ritually clean, the latter shall wash hisclothes, bathe in water and remain uncleantill evening. Everything on which the man sitswhen riding shall be unclean. Whoever touchesanything that has been under him shall be un-clean till evening, and whoever handles suchthings shall wash his clothes, bathe in waterand remain unclean till evening. Any earth-enware bowl touched by the man shall be

smashed, and every wooden bowl shall berinsed with water (Leviticus chapter 15, verses4–12, New English Bible).

As the above quote shows, preventive medi-cine, or action taken to reduce a known healthrisk, has a long history. Preventive approachesempower citizens because by their own behaviorand lifestyle choices they may alter health risks.This empowerment underlies the broad appeal ofpreventive medicine and ensures that it will con-tinue, in one form or another, as an enduringaspect of human culture. It also explains why pre-ventive medicine is embraced by both main-stream medicine and alternative approaches suchas naturopathy (Beckham 1994). Applications in-clude dental health (Boehmer

et al.

1999), regula-tion of fertility (Silva

et al.

1999), cardiovasculardisease (Zhang

et al.

1999), and many others. Thepublication of journals such as

Preventive Medicine,Preventive Veterinary Medicine

, and

European Journalof Cancer Prevention

reinforces the acceptance ofpreventive approaches as part of mainstreammedicine.

METHODOLOGICAL ISSUES

Common to all the examples listed is a quantifica-tion of the risks associated with particular behav-iors or lifestyles and a demonstration, using estab-lished scientific methodologies, of how these riskscan be prevented or reduced. These methodolo-gies are reviewed critically and revised and up-dated constantly (Abramson 1990; DeAngelis 1990;Bausell 1991; Holder & Howard 1992; McConway1994; Grbich 1999). Ideally, this leads to a situa-tion in which there is widespread acceptance andconfidence of the nature of risks, and the costsand benefits involved in preventing them can beconsidered.

Nevertheless, it is also true that a clear link-age of cause and effect is rarely concluded with-out some subjectivity and judgment. In an assess-ment of passive smoking risks, NHMRC (1997;p. 7) noted, “It is always possible to propose alter-native, noncausal explanations for associations be-tween disease and possible risk factors. However,it is not possible to postpone indefinitely makinga conclusion about the possible hazards of passivesmoking, since scientific evidence is always incom-plete. In practice, all science depends on judg-ments, and judgments about cause and effect arealways based on the evidence that is currentlyavailable.” In this light, peer review within the sci-

Calver: The Precautionary Principle and Ecosystem Health

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entific community, both before and after a workis published, is a common yardstick used to evalu-ate the merits of findings (Hull 1988; Harding1998) and periodically understandings of causeand effect can be overturned (McDonel 1999).Thus while scientific methods in preventive medi-cine can quantify risks, they do not do so with to-tal certainty.

LEGAL, ECONOMIC, ANDEDUCATIONAL IMPLICATIONS

The element of uncertainty that is almost alwayspresent in applications of preventive medicinehas important implications for legal disputes overpreventive measures, such as the responsibilitiesof employers for issues such as passive smoking(NHMRC 1997). One must also consider whetheror not the economic cost of preventive measuresis justified, although many studies suggest thatpreventive medicine approaches save consider-able sums compared to curative actions (e.g.,Chapter 15 of Whelan 1984; Chapter VII of Koven1996; Pelletier 1999). Also important is the choiceof educational approaches to best empower peo-ple to use preventive measures in their own lives(Cowie 1990; Paul & Sanson-Fisher 1996). Allthese elements are illustrated in two contentiousexamples in preventive medicine: cigarette smok-ing and vaccination.

EXAMPLES

In the case of cigarette smoking, the main aim ofpreventive medicine is simply to induce people toeither stop or never adopt a habit that is harmfulto health. The health effects of both direct andpassive smoking are widely accepted by medicalpractitioners (NHMRC 1997; Bergen & Caporaso1999). They are often succinctly documented inhealth promotion campaigns of professional bod-ies and are presented as established fact in under-graduate textbooks for students in the health andlife sciences. Huge savings on medical bills of upto $100 billion annually in the United States areestimated to be available by slashing tobacco use(Koven 1996). Nevertheless, this position was es-tablished in the face of intense challenges fromthe tobacco industry (Whelan 1984). This ap-proach exploited the inevitable incompletenessof scientific knowledge to challenge causal rela-tionships between smoking and health. It high-

lights the contention that plagues accepted scien-tific views in preventive medicine when financialinterests or strongly held personal values are in-volved. The contest between smoking advertise-ments on the one hand and health promotionson the other also illustrates the role of educationin disseminating knowledge critical to preven-tion.

Vaccination represents a medical interven-tion for the purpose of preventing a diseaserather than a call to desist from unhealthy behav-ior. The mainline medical position is well ex-pressed by the Commonwealth of Australia (1994):

Immunisation is one of the most effectivepublic health measures for the control ofcommunicable diseases. Modern vaccines pro-vide high levels of protection against a num-ber of potentially serious diseases. Althoughthere is no vaccine which is entirely free of se-rious side-effects, in every instance the bene-fits of disease prevention far outweigh therisks of vaccination (p. v).

However, cases of serious adverse reactions toimmunization (e.g., Howson & Fineberg 1992)are the basis of a range of popular publicationseither opposing the practice or urging parentsto research the risks themselves before immuniz-ing their children (Australian Vaccination Net-work 1998). Bazeley & Kemp (1994) concludedthat parental attitudes were critical in compliancewith immunization schedules. Issues important insecuring compliance were awareness of the im-portance, effectiveness, and safety of vaccines, withworries about side-effects a major concern. Com-munity level information and support campaignswere judged more effective than mass campaignsin the media or the influence of professionals inincreasing compliance with immunization sched-ules.

Overall, preventive medicine has a long his-tory, accepted methodologies, and a strong po-tential to empower individuals. In many cases italso offers considerable cost savings relative to thecost of treatment. However, it relies on commu-nity education for success, and choosing the ap-propriate educational approaches is critical inshaping attitudes and behavior. Ironically, the ac-cepted methodologies that underpin preventivemedicine are also a weakness. Scientific debateand dispute can be used to undermine or contestconclusions, with the defense mounted by the to-bacco industry a pertinent example. Many ofthese themes are echoed in applying the precau-tionary principle to protect ecosystem health.

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CHARACTERISTICS OF THE PRECAUTIONARY PRINCIPLE

HISTORY AND APPLICATIONS

The precautionary principle is little more than adecade old. While its origins are unclear, it is ac-cepted that it arose within the environmentalmovement in Germany and first came to Euro-pean prominence through its acceptance andpromulgation at the Second International NorthSea Conference in 1987 (Gray & Bewers 1996).The participating nations agreed to limit dis-charges of persistent, toxic, or bioaccumulablesubstances into the North Sea if harm was onlysuspected, without requiring scientific evidence(Gray

et al.

1991). The new approach focused onscientific uncertainty, placed the burden of proofon industry rather than on environmental advo-cates, and gave priority to anticipation by man-agement to avert possible, but not certain, dam-age (Garcia 1994). The precautionary principle isnow invoked widely in national legislation and in-ternational declarations in many environments(Deville & Harding 1997).

However, even supportive authors are oftenfrustrated by the difficulty of applying the precau-tionary principle. O’Riordan & Cameron (1994;p. 12) called it a “shambolic concept,” whileHickey & Walker (1995; p. 426) complained thatit was “ill-defined” and “ambiguous.” Frustrationarises mainly because there has been no consis-tent, widely held definition of the precautionaryprinciple and key terms within existing defini-tions may be undefined (Gray & Bewers 1996).Thus the precautionary principle differs signifi-cantly from preventive medicine in dealing withuncertainty, not established risks, and in not hav-ing an agreed corpus of methodologies.

METHODOLOGICAL ISSUES

Boehmer-Christiansen (1993) asserted stronglythat the absence or minimal participation of sci-ence in political applications of the precautionaryprinciple is a strength. However, as invocations ofthe precautionary principle become more andmore frequent, many authors seek to establish arole for scientific methodology in applying theprecautionary principle in those cases where it isinvoked, but there are no agreed procedures forits implementation. Approaches include Baye-sian statistics (Varis & Kuikka 1997), risk analysis(Rogers

et al.

1997), and statistical power analysis

(Underwood 1997). At present, the power analy-sis approach has the highest prominence in theliterature and therefore will be discussed in de-tail. However, this does not mean that the otheroptions lack importance or might not ultimatelyprove superior.

In statistical hypothesis testing, “. . . power isthe probability of rejecting the null hypothesiswhen it is in fact false and should be rejected” (Zar1984, p. 43). It is extremely relevant to environ-mental issues, since it deals with cases where an ex-perimental test of a putative environmental impactis not significant. These cases are of special con-cern since they may arise either because there isno effect or because the experiment/monitoringlacked the sensitivity to detect an impact that actu-ally occurred (Peterman 1990). Power analysis helpsby determining the probability that an impact ofgiven magnitude would have been detected if ithad actually occurred. If power is low (commonlydefined as less than 0.85 or 0.9; Thomas & Juanes1996), then the test is insensitive and a possible im-pact has not been discounted. Power is directly re-lated to sample size/replication in the study, thelevel of significance (

a

) chosen for the test, andthe effect size (ES), which is the minimum differ-ence/change that one wishes to detect. Highpower in a test can be achieved by increasing sam-ple size, relaxing

a

above the traditional level of0.05, or seeking to detect only a large ES.

Given the likelihood of low power in manyecological studies and environmental monitoring,several authors have argued for a reversal of theburden of proof in impact studies, asking industryto demonstrate with high power that an unaccept-able impact is unlikely (Peterman 1990; Peterman& M’Gonigle 1992; Underwood 1997). Such a re-versal is entirely consistent with the precautionaryprinciple. It protects against the potential abuseof impact studies by designing studies with lowpower, which could be used to argue that envi-ronmental impacts have not been demonstratedeven though the chance of detecting them waslow. Required effect sizes and power for particu-lar situations could be stipulated by legislation orconvention, or groups of stakeholders could beconvened to decide these issues before a test pro-ceeds (Mapstone 1995).

LEGAL, ECONOMIC, ANDEDUCATIONAL IMPLICATIONS

The legal and economic implications for privatecompanies or government instrumentalities of re-


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strictions on resource use or development areconsiderable, so it seems inevitable that applica-tions of the precautionary principle will be testedin court (e.g., cases referred to in Calver

et al.

1999). Thus, in addition to attempts to introducescientific methodology to the precautionary prin-ciple, legal definitions have been proposed in aneffort to expedite or avoid court cases (Hickey &Walker 1995 and included references). However,it is important to emphasize that precaution doesnot mean saying “no” in all cases. Deville & Hard-ing (1997) point out that there may be strongeconomic or social grounds for arguing that anactivity should proceed. In such cases, precautioncould entail allowing the activity to proceed instrictly defined stages, accompanied by carefulmonitoring and with provision for halting and re-versing it if a serious problem is detected. It is alsowrong to consider applications of the precaution-ary principle as an overall cost to society, becausethe cost of environmental damage if an inappro-priate activity proceeds may well outweigh anybenefits that accrue (Shrader-Frechette & McCoy1992). If the precautionary principle is to be un-derstood and applied in this sense, then there isalso a clear need for educating those involved inenvironmental projects and decision-making onthe principle’s full implications.

EXAMPLES

There are impressive successes of the precaution-ary principle when used as part of the politicalprocess. For example, Santillo

et al.

(1998) docu-ment the general resolve of the relevant govern-ments to end emissions into the North Sea withina generation. A second case concerned decidingwhether mining for heavy minerals, followed byrehabilitation, should be permitted on the east-ern shores of Lake St. Lucia, South Africa. The re-sults of a detailed environmental impact assess-ment were submitted to a panel of eminent laypeople who considered them and then recom-mended to the South African government thatmining not proceed, invoking the precautionaryprinciple in justification of their decision. Criticalto the decision was the perceived value of thearea; uncertainty about the magnitude of possibleimpacts and concern that impacts could not bemitigated (Kruger

et al.

1997). It is significant thatthese successes in applying the precautionaryprinciple as a political process took place in an at-mosphere of accord regarding goals. In other

cases, applications of the precautionary principlehave been contested politically or in the courtsand judgment has been complicated by the lack ofclear, quantitative definitions (Calver

et al.

1999).Underwood (1997) addressed this need for

clarity in the decision-making process with a de-tailed discussion of the possible impacts of a hypo-thetical wastewater discharge on a marine coastalenvironment. He proposed a monitoring systemto evaluate putative impacts, based on the densi-ties of a hypothetical benthic worm living in theregion of the discharge. The worm would be animportant indicator of the health of the benthicsediment, while maintenance of worm populationdensity would be important in sustaining regionalfood webs.

Underwood argued that statistical hypothesistesting procedures could be used to compare thedensities of worms in control sites to those nearthe discharge so the discharge could be halted ifany impact occurred. To accord with a precau-tionary approach, the magnitude of change inworm numbers that should trigger a managementresponse (effect size) would be chosen in advanceand management would be required to demon-strate with an agreed level of statistical power thatsuch a change had not occurred. In turn, thiswould demand detailed consideration of samplesizes for the trial and the level of

a

chosen forthe test. Such an approach requires agreement inadvance from all stakeholders on power and ef-fect size, and it is then the responsibility of man-agement to design and implement the monitor-ing to achieve these goals. Underwood saw thisapproach as having four significant advantages: (1)highlighting the need for good sampling designto truly monitor the putative impact; (2) definingin advance the magnitude and direction of changesthat should cause concern; (3) forcing explicitconsideration of statistical power and avoidingthe problem of misleading, insensitive tests; and(4) providing very clear arguments about the levelof funding required to monitor at a standard ac-ceptable to all stakeholders.

Mapstone (1995) and Keough & Mapstone(1997) extend these ideas by suggesting that deci-sion-making should consider the costs of eitherfalsely concluding an impact has occurred when ithas not (type I error), or falsely concluding noimpact when in fact one has occurred (type II er-ror). Then it is possible to express the ratio ofcost of type II error:cost of type I error and usethis ratio to judge the acceptable ratio of type II:type I errors in a study. For example, if a type II

104


error carried four times the cost of a type I error,then the study would be weighted to ensure thatthe chance of a type II error was only a quarter ofthat of a type I error. This approach has the excel-lent advantage of requiring stakeholders to agreeon the magnitude of the impact to be detectedand the costing of the respective errors. It istherefore a participatory process.

Critics of the statistical approach highlightthat it only acts after an impact has occurred,which may be unacceptable (see discussion inSantillo

et al.

1998). Therefore, the true role of astatistical approach may be when an activity is per-mitted under the precautionary principle, with anunderstanding that it is monitored and halted ifan impact of a particular magnitude occurs.

WHAT CAN PREVENTIVE MEDICINE AND THE PRECAUTIONARY PRINCIPLE TEACH EACH OTHER?

PREVENTION DOES NOTEQUAL PRECAUTION

Preventive medicine promises empowerment bylinking cause and effect in health issues, enablingpeople to make choices that reduce serious healthrisks. While the precautionary principle is an em-powering approach to uncertainty in environ-mental matters, it differs from prevention in ap-plying specifically to cases where risk is suspected,not known (Deville & Harding 1997; Cameron1999). In an interesting twist, Davis

et al.

(1998)and David (1999) argued that the concept of act-ing on suspicion of risk, rather than establishingcause and effect, could translate from environ-mental practice to preventive medicine. Healthprofessionals would be required to act on suspi-cion of harm before definitive evidence was avail-able. However, Wainwright (1998) warned thatthis could lead to a paralysis in health policy, withadministrators afraid to initiate reform for fear ofpossible negative consequences. Similar criticismshave been made of the precautionary principle inenvironmental issues (see brief review in Harding& Fisher 1999; pp. 17–19). These cases highlightpeople’s concern to deal with uncertainty in rela-tion to their health as well as the environment,but warn against using the precautionary princi-ple as an argument against all change.

The uncertainty inherent in the precaution-ary principle means that it is far more likely to becontentious than preventive measures. There isalso the problem that commercial interests mayblock input from private citizens into precaution-ary decisions, negating the potential for applyingthe precautionary principle to be an empoweringprocess. Industry also finds precaution difficult todefine and therefore hard to include in strategicplanning (Segal 1999).

ESTABLISHED METHODOLOGY DOES NOT ENSURE RESULTS WILL BE ACCEPTED

Superficially, preventive medicine enjoys the ad-vantage of established methodologies which prom-ise unambiguous studies providing a clear guideto action. However, the promise cannot always bedelivered because of the inevitable subjectivityinherent in interpreting scientific results. Thuslobby groups arguing from a preconceived posi-tion may either dispute the methods used in astudy, or contest the meaning of the findings. Dis-putes over the health impacts of direct and pas-sive cigarette smoking indicate that lobby groupsmay exploit characteristics of the scientific methodto contest unfavorable findings.

Should the precautionary principle seek todevelop scientific definitions and methodologiesof its own, or should it recognize that these arepotentially fraught with contention and seek toremain solely a sociopolitical process? If the pre-cautionary principle is used as a guide to decisionmaking as an explicitly political process, with in-put from all stakeholders, it may function effi-ciently without recourse to science and avoid thedebates between experts that dog some applica-tions of preventive medicine. However, if this pro-cess fails, quantitative scientific methods, such asstatistical power analysis, may allow stakeholdersto develop explicit decision rules for the applica-tion of the precautionary principle in specificcontexts. Such approaches are worth pursuing,especially because they require all stakeholders todiscuss decision criteria frankly before any actionthat might endanger the environment begins. Inthis regard, the precautionary principle can learnfrom the experiences of preventive medicine.Similarly, preventive medicine may benefit by em-bracing the participatory approach to choosingaction in the face of uncertainty that character-izes the precautionary principle. Davis

et al.

(1998) argue strongly for this approach in the ep-idemiology of breast cancer.


105

EDUCATION AND PARTICIPATION ARE THE KEYS TO ACTION

Even where cause and effect are not contested,preventive medicine campaigns may have low suc-cess rates if people are unaware of their optionsor are not highly motivated to implement them.Gambel

et al.

(1999) reported low compliance ofmilitary personnel in Haiti with preventive proce-dures to reduce the risk of dengue fever and rec-ommended the very military solution of “com-mand enforcement” to overcome the problem.Such measures contravene basic civil liberties inmost areas of personal health for private citizens,so education is often the key to successful adop-tion of preventive measures. Significantly, success-ful education campaigns and choice of preventivestrategies vary from culture to culture (e.g., Kall-estal

et al.

1999) and a high degree of participa-tion from community groups is often valuable(Bazeley & Kemp 1994). The important lesson forthe precautionary principle is that enhancedawareness can help in increasing compliance, butthat measures need to be responsive to local is-sues and participatory to have the greatest chanceof success.

In return, the precautionary principle warnspreventive medicine that attention to local issuesand community participation may also be the keyto avoiding frustrated rejection of expert adviceby people wishing to assess their own health orthe quality of their environment. Verweij (1999)drew attention to the growing problem of “medi-calization” in which increasing aspects of people’slives are classed as “unhealthy” or “healthy” andthere is resentment of unwanted intrusion in pri-vate decisions. In ecosystem health, such views areexpressed in political approaches that deny sci-ence a prominent place in the precautionaryprinciple’s application. An alternative may be touse mediation approaches in cases of dispute,drawing on scientific information to quantify is-sues where possible (see the case study of Cocks

etal.

1996 for an environmental application). How-ever, the interfaces between decision making, riskmanagement, and the social psychology of man-agement are turbulent (Maguire & Sondak 1996),and there is no easy “formula” decision.

CONCLUSION

Many authors acknowledge the conceptual attrac-tiveness of the precautionary principle in ecosys-

tem health (O’Riordan & Jordan 1995; Deville &Harding 1997). If community participation is en-couraged, it empowers lay people by giving thema place in environmental debate and decision-making. It also has the potential to save societies,as larger units, the costs of restoring environmen-tal degradation. These potential benefits endorsecommunity education programs to enhance theapplication of the precautionary principle (Dev-ille & Harding 1997). However, it is also arguedthat the promise of the precautionary principlewill fail unless the term is “sharpened” (O’Rior-dan & Jordan 1995). This implies a need forclearer definitions and better methodologies inapplication. All these points can be interpreted aslessons from preventive medicine, which also hascharacteristics of individual empowerment, costsavings and community education, as well as es-tablished methodologies. Nevertheless, preven-tion deals with established risks, while precautiontackles cases where risk is uncertain. This funda-mental difference will always characterize applica-tions of the precautionary principle. However,the desire of many people to have a protocol foraction where health risks are suspected but notyet established probably explains the resurgenceof precautionary views in medicine. Thus the pre-cautionary principle is now giving lessons of itsown to preventive medicine.

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Lessons from Preventive Medicine for the Precautionary Principle and Ecosystem Health