Lancet special issue on malaria eradication: No call for more DDT


Lancet is one of the premiere research journals in the world for all of science, but especially for issues of health and medicine.

Image from Lancet illustrating malaria story

Image from Lancet

On October 29, 2010, Lancet published a special report, “Malaria Elimination.”  Much science.  Much history.  No call for more DDT.

A plan for research is laid out.  Plans to eradicate malaria from more than 90 nations are laid out, explained and debated.  Calls for more research are made.  Calls for disciplined action from nations and health care organizations, and donor organizations.

But no call for more DDT.

Go take a look at the issue.  Several of the articles are available for no charge, out from behind the usual Lancet paywall.

Get the real science, real history, real policy.  Environmentalists are not evil villains there.  malaria is the villain in that story, and serious health care researchers and deliverers discuss serious methods to beat the disease.  Consequently, DDT has only a bit part.

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7 Responses to Lancet special issue on malaria eradication: No call for more DDT

  1. Ed Darrell says:

    So, Royce, now that we’ve updated that article by 10 years, and rather refuted its claims, what do you say?

    Update 3-1-2011: The repellent qualities of DDT led to the first series of mutations that made mosquitoes resistant to the stuff — they stopped making their post-prandial stop on the walls of huts. DDT is no good if it doesn’t kill mosquitoes — claiming repellent qualities is not enough to bring back something that poisons the predators of mosquitoes more effectively than the mosquitoes themselves. DDT’s repellent qualities are a disadvantage to the functioning of DDT as a killer, but not good enough justify using DDT as a repellent.

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  2. Royce says:

    The article was in

    Nature Medicine – July 2000 – Volume 6 Number 7 – pp 729 – 731

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  3. Ed Darrell says:

    Also, Royce, see what the malaria fighters say:

    Environ Health Perspect. 2010 July; 118(7): A282–A283.
    doi: 10.1289/ehp.1002279.
    [hotlinks to references may be found at that site]

    PMCID: PMC2920925
    Copyright – This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article’s original DOI.

    Perspectives

    Correspondence

    The Role of DDT in Malaria Control

    Hans Rudolf Herren
    Millennium Institute, Arlington, Virginia, E-mail: hansrherren@mac.com

    Charles Mbogo
    icipe–International Center of Insect, Physiology and Ecology, Nairobi, Kenya
    H.R.H. is employed by the Millennium Institute, a nonprofit organization; CM is employed by icipe (International Center for Insect Physiology and Ecology), Nairobi, Kenya.

    The letter “DDT and Malaria Control” (Tren and Roberts 2010) is the latest in a long string of opinion pieces placed by authors associated with Africa Fighting Malaria (AFM). Appearing in both the popular media (e.g., AFM 2006; Bate 2009; Bate and De Lorenzo 2007; Roberts 2007a; Tren 2002) and scientific literature (e.g., Attaran et al. 2000; Roberts 2001, 2007b; Roberts et al. 2000, 2004; Tren 2009), these articles and letters reduce the complex issue of malaria control to a single, dichotomous choice between DDT and malaria. Framing the issue in this manner is a dangerous oversimplification and an distraction from the critical dialog on how to effectively combat malaria around the world—particularly in African communities.

    The question that AFM and malaria control experts must ask is not “Which is worse, malaria or DDT?” but rather “What are the best tools to deploy for malaria control in a given situation, taking into account the on-the-ground challenges and needs, efficacy, cost, and collateral effects—both positive and negative—to human health and the environment, as well as the uncertainties associated with all these considerations?”

    Tren and Roberts (2010) briefly acknowledged that alternatives to DDT exist (while denigrating them as “supposed solutions”), but in typical fashion they focused most of their letter on the chemical, arguing that the health effects of malaria are much worse that those of DDT exposure. As malaria professionals we are well aware of the dire health consequences of malaria, but also of DDT. The challenge before us is therefore to determine how much weight to give to vector control within the broader context of a malaria control program; within vector control, how much weight to allot to nets versus indoor residual spraying (IRS); and within IRS, how much weight to give to DDT or some other chemical.

    These decisions are indeed complex and location specific. In this regard, van den Berg’s commentary, “Global Status of DDT and Its Alternatives for Use in Vector Control to Prevent Disease” (van den Berg 2009), is a most useful contribution. In contrast, Tren and Roberts’ (2010) advice that “van den Berg’s concerns should be ignored” strikes us as reckless and irresponsible.

    In 2006, Allan Schapira, former coordinator of vector control and prevention of World Health Organization’s Global Malaria Programme, observed that malaria control discussions had become “polluted,” and warned, “The renewed interest in indoor residual spraying could lead to interminable debates in countries about the pros and cons of DDT” (Schapira 2006). However well intentioned, Tren and Roberts (2010)—as with much of AFM’s output—do more to fuel those “interminable debates” than to meaningfully inform decisions that will save people’s lives.

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  4. Ed Darrell says:

    Royce, can you tell us where that article came from? I’m nervous about copyright — please identify before I must strike it.

    That article provokes a question: If DDT is available now, and in use safely, why is Rutledge Taylor calling for more DDT than can be used safely?

    If that article were correct, that DDT is safe without severe restrictions, why not make the case in court to change U.S. regulations? And you know the answer: The claim DDT is safe has been falsified.

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  5. Royce says:

    This article contains important information that will
    save lives in malaria threatened countries. As will
    a movie I recently watched… 3 Billion and Counting.

    July 2000 Volume 6 Number 7 pp 729 – 731

    Balancing risks on the backs of the poor

    Amir Attaran2, Donald R. Roberts1, Chris F. Curtis3 & Wenceslaus L. Kilama4

    1. Department of Preventive Medicine and Biometrics Uniformed Services University of the Health Sciences Bethesda, Maryland 20814, USA
    e-mail: droberts@usuhs.mil
    2. Center for International Development Kennedy School of Government Harvard University Cambridge Massachussetts 02138, USA
    e-mail: amir_attaran@harvard.edu
    3. London School of Hygiene & Tropical Medicine London WC1E 7HT, UK
    4. Chairman, Malaria Foundation International; also Chairman-Coordinator, African Malaria Vaccine Testing Network C26/27 Tanzania Commission for Science and Technology Building, Ali Hassan Mwinyi Road, P.O. Box 33207 Dar Es Salaam, Tanzania

    Malaria kills over one million people, mainly children, in the tropics each year, and DDT remains one of the few affordable, effective tools against the mosquitoes that transmit the disease. Attaran et al. explain that the scientific literature on the need to withdraw DDT is unpersuasive, and the benefits of DDT in saving lives from malaria are well worth the risks.
    Few chemicals stir the feelings of the ‘man on the street’ quite like DDT (dichlorodiphenyltrichloroethane). Since Rachel Carson’s Silent Spring, conservationists in rich, developed countries have waged a decades-long campaign, no less persistent than DDT itself, to convince governments and citizens that DDT is an irredeemable pollutant. They have been very successful: Every industrial country, without exception, has ceased using DDT.

    However, DDT remains one of the few affordable, effective tools against the mosquitoes that transmit malaria, a plague that sickens at least 300 million and kills over one million, mainly children, in economically underdeveloped areas of the tropics each year. Such a toll is scarcely comprehensible. To visualize it, imagine filling seven Boeing 747s with children, and then crashing them, every day.

    Until now, developed countries have grudgingly tolerated the use of DDT against malaria in poor tropical countries; at least 23 countries do so1. However, this may now be ending. Led by the United Nations Environment Programme, more than 110 countries are negotiating a treaty to “reduce and/or eliminate…the emissions and discharges” of 12 persistent organic pollutants, citing their “unreasonable and otherwise unmanageable risks to human health and the environment.”2 If it becomes law, the treaty will likely end DDT manufacture, or at least make the supply scarce and unaffordable to tropical countries.

    This, in our view and that of nearly 400 colleagues who have signed an open letter to the diplomats negotiating the treaty, is simply dangerous3. The scientific literature is unpersuasive of the need to withdraw DDT; on the contrary, it is clear that doing so risks making malaria control ineffective, unaffordable, or both.

    Ecological effects
    DDT became emblematic of the toxics movement because of its effects on the non-human environment. Ecological studies have demonstrated that bioaccumulated DDT could cause thinning of eggshells and reproductive failure in birds of prey. The fault for this lies in the massive agricultural use of DDT. Dusting a single 100-hectare cotton field, for example, can require more than 1,100 kg of DDT over 4 weeks4.

    In contrast, DDT spraying for malaria control is less intensive, less frequent and far more contained. The current practice is to spray the interior surfaces only of houses at risk, leaving a residue of DDT at a concentration of 2 g/m 2 on the walls, ceiling and eaves, once or twice a year. Half a kilogram can treat a large house and protect all its inhabitants. Doubtless some fraction of this escapes to the outdoors, but even assuming it all did, the environmental effect is just 0.04% of the effect of spraying the cotton field. Guyana’s entire high-risk population for malaria can be protected with the DDT that might otherwise be sprayed on 0.4 km2 of cotton in a season5. Compared with its agriculture uses, public health uses of DDT are too trivial to merit banning with any urgency.

    Tonic…or toxin?
    Environment aside, health considerations arise, and with them the dilemma that one man’s benefit is another man’s risk. Environmentalists in rich, developed countries gain nothing from DDT, and thus small risks felt at home loom larger than health benefits for the poor tropics. More than 200 environmental groups, including Greenpeace, Physicians for Social Responsibility and the World Wildlife Fund, actively condemn DDT for being “a current source of significant injury to…humans.”6 But five decades of experience with DDT shows that it is highly effective and safe when deployed in house spraying7.

    Reliance on DDT reached its zenith, and malaria, its nadir, with a campaign to eradicate malaria from large parts of the world in the 1950s and 1960s. The early results were impressive: in less than two decades, spraying of houses with DDT reduced Sri Lanka’s malaria burden from 2.8 million cases and 7,300 deaths to 17 cases and no deaths. India and South America achieved similarly impressive reductions, and several countries fully eradicated malaria1. Even in sub-Saharan Africa, where mosquitoes are most difficult to control, DDT spraying resulted in great reductions in malaria8.

    Unfortunately, many of these successes were short-lived. American funds, which underwrote the eradication campaign, soon lapsed, and overuse of DDT in agriculture bred DDT-resistant mosquitoes. Back in malaria’s grip, Sri Lanka returned to a half a million cases by 1969.

    But despite ‘resistance’ in itself, DDT still works to alleviate mortality and morbidity. Resistance tests work by measuring whether mosquitoes survive a normally toxic dose of DDT. The tests wholly overlook two non-toxic actions of DDT: contact-mediated irritancy9, which drives mosquitoes off sprayed walls and out of doors before they bite, and volatile repellency10, 11, which deters their entry in the first place. Both actions disrupt human–mosquito contact and disease transmission.

    Data from the Pan-American Health Organization show a strong inverse correlation between malaria cases and rates of spraying houses (1959–1992) in South America, even after DDT resistance became widespread in the 1960s Fig. 1. Here, ‘cumulative cases’ represent the population-adjusted, ‘running’ total of cases that exceed or fall short of the average annual number of cases from 1959 to 1979 (years in which World Health Organization strategy emphasized house spraying12). Cumulative cases increase considerably in later years, coincident with a sharp decrease in rates of spraying houses.

    This inverse correlation is readily understandable because it is so biologically plausible. For mosquitoes, DDT is a toxin, irritant and repellant all rolled into one chemical. All three properties decrease the odds of being bitten by mosquitoes, and toxicity particularly reduces the odds that parasite-bearing mosquitoes will survive to infect others. Lowering these odds slows disease propagation by second- or higher-order relationships and therefore is very important13, 14. Indeed, renewing the spraying of houses with DDT, as Ecuador did in the early 1990s, rapidly decreases case rates5.

    This body of evidence is so indisputable that even environmental groups such as Physicians for Social Responsibility concede that DDT is “highly effective” in malaria control15. Campaigning for a DDT ban given this benefit would seem politically difficult unless one alleged even greater health risks associated with its use, which is precisely what environmentalists do. Recent bulletins from Physicians for Social Responsibility and the World Wildlife Fund cite animal studies indicating involvement of DDT in neurological and immune deficits, and epidemiological studies linking DDT to human cancers and endocrine-disrupting effects, such as reduced lactation15, 16.

    In this kind of ‘balance of risks’ paradigm, the evidence must be scrupulously weighed. Although the International Agency for Research on Cancer rates DDT as a possible human carcinogen (along with, notably, several pharmaceutical drugs), not one case-control study of DDT’s human carcinogenicity has been affirmatively replicated. Breast cancer furnishes the clearest example: the first study to correlate DDT exposure with statistically elevated risk17 has now failed to be replicated at least 8 times18-25, and of these later studies, some found exposure to significantly reduce risk24, 25. Much the same can be said of studies indicating involvement of DDT in multiple myeloma, hepatic cancer and non-Hodgkin lymphoma26, 27.

    That DDT interferes with maternal lactation is also questionable. The leading study to correlate DDT metabolites in breast milk with unexplained, premature weaning28 does not reach statistical significance unless the data are first ‘adjusted’ for potential confounders, but the authors did not disclose how their adjustment was done, and other labs have yet to confirm the result28. Lactation’s many social, nutritional and cultural influences make inferences difficult, but even if DDT really abridges lactation, the authors found a “lack of any detectable effect on children’s health.”28

    With such weak evidence of harm to human health, one must decide whether to set policy as a precaution and ban DDT based on animal studies. Ordinarily, this makes sense (given the alternative of experimenting on humans with toxins), but not for the spraying of houses with DDT. Acting with precaution because there are risks in animals, and thus denying people the known health benefits of malaria control, is very unethical: house spraying exposes millions of people to DDT, any of whose health can be studied, making extrapolations from animal studies unnecessary. Proper case-control studies should be done before policy is cast in treaty law.

    Indeed, if precaution is relevant, it favors spraying houses with DDT, because it is affordable or effective where other interventions may not be. Cost data from India show that, even using DDT alone, the entire national malaria-control budget is sufficient to protect only 65% of high-risk persons. Switching to malathion, the next-cheapest alternative, reduces that coverage to 21%, which leaves 71 million more persons unprotected29. House spraying also has the advantage that it protects whole families, which is sometimes overlooked in comparing it with insecticide-treated bed-nets, which protect only one or two people at a time30. Simply put, there are too few economic studies to determine with certainty whether bed-nets are more or less cost-effective than DDT house spraying31. However, the fact that spraying houses with DDT can lower the prevalence of malaria parasitemia in highly endemic African communities to levels below that achieved by bed-nets (less than 5%) indicates that it is careless to treat them interchangeably8.

    Patience in all things
    How then to reconcile DDT’s ‘Janus-faced’ character? Its benefit in alleviating the suffering of malaria, at a reasonable cost, outweighs any reasonable speculation of its health risks. Living with this may not be easy; changing it is harder still.

    Above all, rich countries must allow, and even facilitate, poor tropical countries to make choices about DDT freely, and with informed consent. African countries in particular lack the resources to dispatch health experts to the treaty negotiations, and although it provides financial assistance, the United Nations Environment Programme has declined to assist with this, or even to provide a translator when French- and English-speaking diplomats meet to discuss DDT. The resulting lack of knowledge suffocates debate. At worst, threats are used, as Belize learned when the US Agency for International Development demanded that it stop using DDT.

    Such arm-twisting is as lamentable as it is effective. Highly indebted poor countries must of necessity rank poverty reduction over environmental orthodoxy, and stimulating growth and foreign investment will require nearly eliminating malaria from economically productive zones. This is essential for development in sub-Saharan Africa, where malaria subtracts more than one percentage point off the gross domestic product growth rate, for a compounded loss (since 1965) now reaching up to $100 billion a year in foregone income32.

    Seen in this way, the insistence to do without DDT is ‘eco-colonialism’ that can impoverish no less than the imperial colonialism of the past did. Sub-Saharan Africa, which never experienced much spraying of houses with DDT, should consider starting this. South Africa, Swaziland and Madagascar, among others, run successful DDT-spraying programs and prove it can be done1, 33.

    At present, the United Nations Environment Programme mandate to “reduce and/or eliminate” DDT probably cannot be accomplished safely, without causing extra disease. As ‘preachers of precaution’, environmental groups and rich country governments should start by committing at least $1 billion annually to roll back malaria in Africa. That is the sum requested by African leaders at their first-ever Malaria Summit earlier this year34. Meeting this request is a small price to pay for respecting the lives of the poor, and will bring us much closer to no longer needing DDT. Denying it, on the other hand, is to again embrace indifference, and the pursuit of environmental goals, on the backs of world’s sickest and poorest.
    REFERENCES

    1. World Health Organization. Document SDE/PHE/DP/02 (1999).
    2. United Nations Environment Programme Governing Council. Decision 19/13C (7 February 1997).
    3. http://www.malaria.org/DDTpage.html
    4. Metcalf, C.L. & Flint, W.P. Destructive and Useful Insects: Their Habits and Control 4th edn. (McGraw-Hill, New York, 1962).
    5. Roberts, D. R. et al. DDT, global strategies and a malaria control crisis in South America. Emerg. Infect. Dis. 3, 295– 302 (1997). MEDLINE
    6. International POPs Elimination Network platform. http://www.ipen.org/pops_platform.htm.
    7. World Health Organization and United Nations Environment Programme. Environmental Criteria No. 9. (World Health Organization, Geneva, 1979).
    8. Kouznetsov, R. L. Malaria control by application of indoor spraying of residual insecticides in Tropical Africa and its impact on community health. Trop. Doct. 7, 81–91 (1977 ). MEDLINE
    9. Chareonviriyaphap, T. et al. Pesticide avoidance behavior in Anopheles albimanus, a malaria vector in the Americas. J. Amer. Mosquito Control Assoc. 13, 171–183 (1997).
    10. Grieco, J.P. et al. A comparison of 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, 62–73 (2000)
    11. De Zuleta, J. et al. Deterrent effect of insecticides on malaria vectors. Nature 200, 860–861 ( 1963).
    12. World Health Organization Expert Committee on Malaria. Seventeenth Report. World Health Organ. Tech Rep. Ser. 640 (1979). MEDLINE
    13. Macdonald, G. The Epidemiology and Control of Malaria (Oxford University Press, Oxford, 1957)
    14. Roberts, D. R. et al. A probability model of vector behavior: effects of DDT repellency, irritancy, and toxicity in malaria control. J. Vect. Ecol. 25, 48–61 (2000).
    15. Physicians for Social Responsibility. The Modern Malaria Control Handbook (Physicians for Social Responsibility, Washington, 1999).
    16. World Wildlife Fund. Resolving the DDT Dilemma (World Wildlife Fund, Toronto, 1998).
    17. Wolff, M.S. et al. Blood levels of organochlorine residues and risk of breast cancer. J. Natl. Cancer Inst. 85, 648– 652 (1993) MEDLINE
    18. Krieger, N. et al. Breast cancer and serum organochlorines: a prospective study among white, black, and Asian women. J. Natl. Cancer Inst. 86, 589–599 (1994) MEDLINE
    19. Schecter A. et al. Blood levels of DDT and breast cancer risk among women living in the north of Vietnam. Arch. Environ. Contam. Toxicol. 33, 453–456 (1997) MEDLINE
    20. Hunter D.J. et al. Plasma organochlorine levels and the risk of breast cancer N. Engl. J. Med. 337, 1253– 1258 (1997). MEDLINE
    21. Lopez-Carillo L. et al. Dichlorodiphenyltrichloroethane serum levels and breast cancer risk: a case control study from Mexico. Caner Res. 57, 3728–3732 (1997)
    22. Moysich K.B. et al. Environmental organochlorine exposure and postmenopausal breast cancer risk. Cancer Epidemiol. Biomarkers Prev. 7, 181–188. (1998) MEDLINE
    23. Zheng T. et al. DDE and DDT in breast adipose tissue and risk of female breast cancer. Am. J. Epidemiol. 150, 453– 458 (1999) MEDLINE
    24. van’t Veer P. et al. DDE and DDT (dicophane) and postmenopausal breast cancer in Europe: case-control study. Brit Med. J. 315, 81–85 (1997) MEDLINE
    25. Helzlsouer K.J. et al. Serum concentrations of organochlorine compounds and the subsequent development of breast cancer. Cancer Epidemiol. Biomarkers Prev. 8, 525–532 ( 1999). MEDLINE
    26. Longnecker M. P. et al. The human health effects of DDT and PCBs and an overview of organochlorines in public health. Annu. Rev. Pub. Health 18, 211–244 (1997)
    27. Baris, D. et al. Agricultural use of DDT and risk of non-Hodgkin’s lymphoma: pooled analysis of three case-control studies in the United States. Occup. Environ. Med. 55, 522–527 (1998). MEDLINE
    28. Gladen, B. C. et al. DDE and shortened duration of lactation in a northern Mexican town. Am. J. Pub. Health 85, 504– 508 (1995).
    29. World Health Organization. Document SDE/PHE/DP/04 (1999).
    30. Goodman, C.A. et al. Cost-effectiveness of malaria control in sub-Saharan Africa . Lancet 354, 378–385 (1999). MEDLINE
    31. Goodman, C.A. et al. The evidence base on the cost-effectiveness of malaria control measures in Africa. Health Policy Planning 14, 301–312 (1999)
    32. Gallup, J. L., Sachs J. D. The Economic Burden of Malaria (Harvard Center for International Development, 1998), http://www.hiid.harvard.edu/pub/other/mal_wb.pdf
    33. Mouchet, J. et al. Evolution of malaria in Africa for the past 40 years: impact of climatic and human factors. J. Am. Mosq. Control Assoc. 14, 121–130 (1998). MEDLINE
    34. The Abuja Declaration on Roll Back Malaria in Africa. http://www.rbm.who.int (25 April 2000).

    ACKNOWLEDGMENTS

    The views expressed are those of the authors and do not reflect the official policy or position of the Uniformed Services University of the Health Sciences, the Department of Defense or the United States Government.

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  6. James Hanley says:

    Why does Lancet want to kill 3 billion people?

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  7. karl says:

    I’m sure Africa Fighting Malaria & company are busy drafting letters to the editor of the Lancet excoriating them from not promoting DDT…..

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