CASE TEACHING NOTES
for
"To Spray or Not to Spray:
A Debate Over Malaria and DDT"

by
Frank J. Dinan and Joseph F. Bieron
Department of Chemistry and Biochemistry
Canisius College

BACKGROUND

This case was originally written to introduce a group of freshmen students entering Canisius College to case study teaching.  It was subsequently modified (version presented here) for use in a senior honors seminar filled with both majors and non-majors that deals with the nature and impact of science and technology on society.  This modified version was also used in an organic chemistry course for science majors.  Prior student background includes an introduction to organic chemistry, chemical insecticides (types, structures, properties), risk/benefit analysis, and the precautionary principle.

Objectives

• To explore the controversy and uncertainty that often arise in the interaction of science and technology with society using the current debate over the use of DDT to control malaria for that purpose.
  
  
• To introduce the major concepts of risk/benefit analysis and the precautionary principle, two techniques that are used extensively when making policy decisions involving science/technology and society issues.
  
  
• To explain the strengths and weaknesses inherent in the risk/benefit and precautionary principle techniques.
  
  
• To raise awareness of the ethical and moral implications that often underlying taking or avoiding technological risks.

CLASSROOM MANAGEMENT

We distribute a copy of the case in advance of the class in which it will be taught and ask students to come prepared to discuss it.  The day of the class, students are put into four- or five-person teams to discuss controversial and problematic aspects of the case for about 10 minutes.  We then assign one of the questions to each team for discussion within that team.  After about 10 minutes of discussion, we ask each of the groups to report their conclusions to the rest of the class.  Our experience indicates that it is best if the groups report on the questions beginning with question 1 and proceeding through question 5.  We allow about five minutes for each presentation.  The floor is then opened for a general discussion of the case.  Unfailingly, we have found the discussion to be animated and insightful.

BLOCKS OF ANALYSIS

In this case we have raised several questions concerning DDT's use to control malaria in a manner that reflects the real-world complexity surrounding this issue.  Both environmentalists who oppose all uses of DDT and advocates who favor its use for malaria control have strong and valid points.  We have attempted to represent their positions in a fair and balanced manner.

When this case was being written, the United Nations Organization was still considering invoking a worldwide ban on DDT use by the year 2004.  The World Health Organization, although part of the UN, was opposed to the proposed ban, and the outcome of the debate over DDT's future was uncertain.  On December 10, 2000, an international committee convened by the UN to make a decision on the matter recommended that the use of DDT for the control of malaria be allowed until a more effective solution to the malaria problem is found.  Both sides seem to agree that DDT is more effective controlling of malaria than the naturally occurring pyrethroids that have been extensively used as a replacement for DDT.  The pyrethroids have an effective lifetime measured in months rather than years and are much more expensive than DDT.  In addition, mosquitoes have developed an immunity that protects them from the effects of pyrethroids.

This case demonstrates the complex nature of the risk/benefit analysis process often used to make decisions in situations involving science and technology and society.  In particular, it points out that the concepts of "risk" and "benefit" are not as clearly etched as ome may think.  For example, the "benefits" of using DDT to the people who live in malaria-infested regions of the world are inextricably linked to the "risks" that environmentalists envision resulting from its spraying.

The "precautionary principle" is an important and controversial concept that students are unlikely to be familiar with at this time.  It is, however, rapidly becoming more important in the process of technological decision making.  As this is being written, Sweden is considering banning any substance that persists in the environment and accumulates in living organisms.  This proposed legislation is based on the precautionary principle and argues that a substance need not be proven toxic to be removed as an item of commerce.  The precautionary principle arose in Europe and is widely used there in cases involving economic and environmental policy.  It has become the focal point of a heated controversy raging between environmentalists and technology advocates.

In summary, this case intends to give students a critical look at a complex contemporary issue that has major scientific, technological, and social importance.  It seeks to illustrate the difficulties that arise when scientific/technological choices must be made and there is no clearly "right" choice.  Introducing students to the two controversial methods used to help make these decisions, risk/benefit analysis and the precautionary principle, is designed to make them aware of some of the strengths and weaknesses of these methods.  The accompanying questions require students to look at both sides of this complex question and to realize that there is no single course of action that will be "right" for everyone.  We wish to have our students realize that, when dealing with real-world questions such as those raised in this case study, an imperfect decision often must be made and its consequences accepted.

Comments on the Discussion Questions

Question 1. At one point in the discussion, Ambassadr Iogu comments, "Malaria is not a problem in most of the developing world, although that may be changing." This comment is not followed up in the case study.  What changes could the ambassador be referring to?  How can this comment be related to the West Nile virus problem troubling parts of the northeastern United States?

An increase in the occurrence of malaria and other diseases of tropical origin is being observed in temperate regions in recent years.  This phenomenon is generally attributed to two causes, global warming and increasing international travel, and could result in the incidence of tropical diseases in countries normally thought to be safely removed from that risk.

Modern travel and communications technologies have greatly increased our ability to move rapidly around the globe, and our need and desire to do so.  Business and vacation travel between tropical and temperate regions has become commonplace over the past decade.  When travelers from temperate regions of the globe, most of whom have little resistance to tropical diseases, are exposed to these diseases during their travels, they return home infected.  As a result, malaria and other infectious tropical diseases can be propagated in regions of the globe in which they were thought to pose no threat to human health.

Question 2. What are the strengths, weaknesses, and implications of the precautionary principle as a method for deciding whether a technology should be used?

The precautionary principle, strictly interpreted, would prevent the implementation, or force the removal, of technologies that carry any perceived risk to human life or to the environment.  It is currently the basis for a law in Sweden that would ban the use of any substances that do not decompose in the environment and bio-accumulate in living things.  Strict interpretation of this new law has forced the Swedish glass industry to reverse the centuries-old practice of placing lead in glass, since lead is perceived to represent a threat to the environment.  Proponents of the precautionary principle argue that it reduces the risk associated with the introduction of new technologies.  They also argue that those seeking to introduce a new technology must prove that it is "safe" before it can be used.  Since the risks associated with a technology are frequently not obvious for some time after its implementation and since safety is a subjective judgment (see the discussion of question 3, below), it is difficult to see how it could be proven.

Opponents believe that the precuationary principle would strongly inhibit the development of needed new technologies.  Citing examples from the past, they identify many socially and commercially valuable technologies (DDT, microwave ovens, cell phones) that would not have passed the precautionary principle's stringent standard and would never have been available to society.  They also argue that technologies can never be made entirely risk free and the quest for a "zero-risk" society is unattainable.

Question 3. What are the strengths, weaknesses, and implications of risk/benefit analysis as a method for deciding whether a technology should be employed?

Extensive literature is available dealing with risk/benefit analysis.  Some key points to consider are the nature of the terms "risk" and "benefit." Risk is an objective, quantitatively measurable entity.  It is determined by counting the number of adverse outcomes associated with a given activity and dividing that number by the total number of exposures to that activity.  Safety, on the other hand, is a subjective judgement.  One person, for example, may judge the risk associated with visiting a malaria-infected area to be "safe," while another person considering exactly the same objective risk may judge it to be unacceptably high.

The term "benefit" also has a subjective element associated with it since what one person may see as a benefit, another may view as a risk.  In this case, the use of DDT for malaria control is judged to be a benefit by some and a risk by others.

Question 4. Compare risk/benefit analysis to the precautionary principle.  Which of these methods do you feel would generally lead to better decisions on questions involving potential applications of technologies in society?  On what reasoning is your conclusion based?

Advocates of the precautionary principle urge regulators to "take no action unless you are sure that it will do no harm." They argue that "the lack of full certainty is not a justification for failing to prevent an action that might be harmful." This asks that a negative premise be proven, a logically impossible task.

In contrast, those choosing the risk/benefit method to evaluate technologies argue that all actions (technologies) have associated risks.  Whether those risks are judged to be acceptable is what should determine whether a technology is appropriate for use in society.

The relative strengths and weaknesses of the two methods can be illustrated by asking students to apply the methods not to the evaluation of new technologies but to existing, widely accepted technologies.  Considering the automobile and nuclear power plants in this context has proven to be an instructive exercise that quickly illustrates the relative merits of the alternative evaluation methods.

The precautionary principle presents an alluring argument since the elimination of risk is intrinsically appealing.  Risk/benefit analysis, on the other hand, argues for the proper management of risk, not its elimination.  Applying these methods to existing technologies reveals that risk cannot be eliminated and that an attempt to do so would, in fact, lead to a significant inhibition of technical innovation.  The societal cost that would result from strict implementation of the precautionary principle clearly would be very high.

Question 5. How do you think that the question of using DDT for malaria control vs. banning its use worldwide will be resolved?  Is your answer to this question the same as your view on how this matter should be resolved?  Explain.

Students using this case study will come to very different conclusions about the action that the United Nations will take regarding the proposed ban on the production and use of DDT.  We prompt the students to express their reasoning clearly so that other students may agree with or challenge that reasoning.

Asking what action the United Nations should take raises a different set of issues.  The second question requires that the difference between the practical concerns of this issue be contrasted to the moral and ethical dimensions of the proposed ban.  During class discussion, some students will express the view that a substantial difference exists between these two dimensions of the problem while other students will not.  Debating, however, opens students to the viewpoints of others.

REFERENCES

Carson, R.  1962.  Silent Spring. New York:  Houghton-Mifflin Company.

Curtis, C.F.  2000.  Should DDT be banned by International Treaty?  Parasitol.  Today 13:119-121.

Foster, K.R., P. Vecchia, and M.H. Repacholl.  2000.  Science and the precautionary principle.  Science 288:979-981.

Fredholm, L.  2000.  Sweden to get tough on lingering compounds.  Science 290:1663.

Grieco, et.al.  2000.  A comparison study of the house entering and exiting behavior of Anopheles vestitipennis using experimental huts sprayed with DDT or deltamethrin in the Southern district of Toledo, Belize.  J. Vector Ecol. 25:119-121.

Mack, A.  1997.  Collaborative efforts underway to fight malaria.  The Scientist 11:1-5.

Raloff, J.  2000.  The case for DDT.  Science News (12 July) 158:12-14.

Roberts, D.R., S. Manguin, and J. Mouchet.  2000.  DDT house spraying and re-emerging malaria.  The Lancet 356:330-332.

Satchell, M.  2000.  DDT:  Dangerous Scourge or last resort?  U.S. News & World Report (Dec. 11) 64-65.

Slovic, P.  1987.  Perception of risk.  Science 236 (April 17) 280-285.

VanderZwaag, D.  1999.  The precautionary principle in environmental law and policy:  elusive rhetoric and first embraces.  J. Environ. Law and Practice 8:355-358.

WHO Expert Committee on Malaria.  Use in vector control.  Available at http://mosquito.who.int/docs/ecr20_annex1.htm.

Acknowledgements:  Publication of this case study on the National Center for Case Study Teaching in Science web site has been made possible with support from The Pew Charitable Trusts.

Date Posted:  03/14/01 mb.  Revised  09/06/02 nas.
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