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The facts on DDT

February 3rd, 2004

Thanks to reader Jim Norton, who points to this letter to the Oz on DDT from parasitologist Dr Alan Lymbery, demolishing the nonsense peddled by Christopher Pearson (it’s on Keneth Miles site). My take on Pearson’s nonsense was here, with links to earlier pieces. I’m pleased to see it matches Lymbery almost point for point.

One fact Lymbery adds, of which I was not aware, is that Rachel Carson, who has been much maligned in the debate on this topic, explicitly noted, in relation to the growth of resistance arising from indiscriminate use of DDT

No responsible person contends that insect-borne disease should be ignored . . . The question that has now urgently presented itself is whether it is wise or responsible to attack the problem by methods that are rapidly making it worse

Lymbery concludes

Malaria is responsible for enormous suffering and death. The facts are readily available in the scientific literature. To blame a reduction in DDT usage for the death of 10-30 million people from malaria is not just simple-minded, it is demonstrably wrong. To blame a mythical, monolithic entity called the environmental lobby for the total reduction in DDT usage is not just paranoid, it is also demonstrably wrong. Your article is not only poor journalism, it is an insult to the people who work for the control of parasitic diseases that afflict developing nations.

The same could be said of the dozens of junk science sites in the blogosphere that have reproduced the same nonsense, usually with no attempt to check original sources.

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  1. d
    February 3rd, 2004 at 11:47 | #1

    John q- why don’t you read the actual literature, for example a famous paper by Attaran I quote below. Pearson is not spouting nonsense — you are– he’s hit the nail right on the head. Sad to see you an apologist for ecoimperialism.

    Balancing risks on the backs of the poor

    AMIR ATTARAN2,

    DONALD R. ROBERTS1,

    CHRIS F. CURTIS3&

    WENCESLAUS L. KILAMA4

    Nature Medicine Vol 6 p729. (2000):

    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…

    …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.

    … …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 ‘ecocolonialism’

    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.

  2. John Quiggin
    February 3rd, 2004 at 12:09 | #2

    The policy position stated in this article, namely that more funds should be allocated to malaria and that this “will

    bring us much closer to no longer needing DDT.”

    is not far from that of the WWF, which states that

    “DDT should be banned by 2007… while still ensuring developing countries access to safe, affordable alternative malaria controls”

    As I noted in my posts, the big advantage of DDT is that is cheap, and if rich countries want it banned they should bear the costs.

    There is room for disagreement about whether replacing DDT with safer alternatives is a cost-effective investment. Obviously WWF and the authors you cite disagree on this point.

    But none of this is related to the garbage produced by Pearson, and demolished by Lymbery.

  3. John Quiggin
    February 3rd, 2004 at 12:20 | #3

    I note the following paragraph, omitted from your summary of Attaran

    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 weeks (emphasis added

    I invite readers to look at my original post and Pearson’s article and see whose position is supported by Attaran et al.

  4. d
    February 3rd, 2004 at 13:02 | #4

    John,

    Certainly there are some aspects of Pearson and Lapkin that are probably overstatements- the death toll due to the actions of environmental activst for example is by my estimates in the 100,000s not millions- but still huge. Second- there is no dispute by me that overuse (tonnes) in agriculture is unwise. But you still do not address the key point that activists continue to lobby against ddt for zero use for flimsy gain and huge costs in morbidity and mortality (eg at the persistant organic pollutants conference about 2002), and that use of cheap small quanties of ddt (gramme)for house protection is hampered by major green lobby groups, and that from Rachel Carson on they have mistated the evidence. Certainlly there is no need to assume a conspiracy – just mindless repetition of untruths by credulous people.I.e. gross negligence on the “backs of the poor”.

    And the fact that Pearson is a journo using evidence third hand does not of itself invalidate the first hand case that the green lobby are responsible for an increase in PREVENTABLE malaria deaths in the third world because they have killed people due to economies with the truth.

    Lymbery skirts around the issues and certainly does not demolish the case against green lobby groups – you clearly are spouting empty rhetoric on that.

    By the way- Michael Crighton is a medical doctor by primary training I believe, and in earlier posts at this site those who run him down should perhaps ask if they are better qualified than him on medical topics.

    Attaran’s comments are also echoed in the Lancet -just do a search at your library using search term ddt.

  5. d
    February 3rd, 2004 at 13:08 | #5

    John, since you mention part of the Attaran article that I did not quote (but which is irrelevant to my argument) I will point out you omitted to mention the following highly relevant bit that hurts key points you made about “ddt resistant moquitoes”.:

    …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: contactmediated

    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.

  6. John Quiggin
    February 3rd, 2004 at 13:33 | #6

    d, I omitted to mention the para on resistance because you’d already done so.

    That said, I think Attaran et al understate the importance of resistance compared to most of the literature I’ve read. The World Health Organization, for example (see particularly section 8.2).

    And the construction of their graph is idiosyncratic, to put it mildly. At first sight it appears to show a clear negative correlation between spraying and malaria, but the actual measure is “cumulative cases in excess of baseline”. Whenever I see a strange choice of measure like this, I’m inclined to suspect that a graph drawn with the obvious measure (in this case, prevalence of malaria) would not show the same result.

    Finally, coming back to Pearson, the fact that experts disagree about the severity of resistance problems can’t save him – he never even mentioned resistance.

  7. d
    February 4th, 2004 at 08:20 | #7

    If, as the citations I quoted show, ddt is effective, cheap, and if used in for house dusting , safe for health and the environment, why in the face of a huge disease problem for poor people ban it at all? You seem to support a ban but dont explain why.

    I suggest that the continued push for a ban is to protect the PR reputation of the lobby groups who have relied on an exaggerated story about ddt for political power. A climbdown would be too much egg on their face. So to protect their image, people in the tropics have to die. Thats the point of Pearson’s punchy message, and thats the point that being evaded by the comments you are mustering.

    Why so little from Quiggen about the anti-ddt exaggerations, since you are clearly alert to Pearsons exaggerations. If lies about ddt’s ill-effects kill people, why are those lie tellers non-culpable?

  8. John Quiggin
    February 4th, 2004 at 08:36 | #8

    If, as the citations I quoted show, ddt is effective, cheap, and if used in for house dusting , safe for health and the environment

    On the contrary, it is agreed by all that the manufacture and use of DDT is dangerous to the environment, and that there are safer and equally effective alternatives.

    The only unqualified advantage of DDT is that it is cheap. If poor countries have to foot the bill, the cheapness of DDT outweighs the moderate environmental damage caused by its use for house dusting. So if rich countries want it banned they should pay.

    But since you refer to Pearson again, where in his entire article would you discover the facts that are common ground in this debate

    (i) DDT is still available and widely used for anti-malarial house-dusting

    (ii) the ban on agricultural use of DDT was entirely justified

    (iii) in most cases, the abandonment of DDT programs has been due either to lack of sustained funding or to the growth of resistance (the Attaran view that even with high levels of mortality resistance, DDT still has some beneficial effect is a second-order qualification on this point).

    But if you point to an article (not selected out-of-context quotes) from the anti-DDT camp that contains either serious factual distortions or a call for an unconditional ban on DDT (that is, without a reference to funding for replacements), I’ll be happy to denounce it.

    Finally, at least in my eyes, your status as a careful reader of the literature would be enhanced if you spelled my name correctly – you only have to copy it from the signature on the comment.

  9. d
    February 4th, 2004 at 10:00 | #9

    “On the contrary, it is agreed by all that the manufacture and use of DDT is dangerous to the environment, and that there are safer and equally effective alternatives. ” Quiggin Quote

    No John, It is not agreed by all that DDT and its manufacture is dangerous to the environment.

    For example Lapkin in his Quadrant article cites petitions signed by numerous scientists protesting the ban, Attaran and the Lancet papers express disquiet about the ban and the reason for the disquiet is the belief that any hazards are manageable.

    Your over the top “agreed by all” assertion is patently untrue, and probably is the result of uncritical belief in rhetoric by lobby groups to enable a total ban. I’m keen to call these groups to task because of the real harm they cause-The total elimination of ddt proposed by lobby groups is killing people. Careful moderate can save lives and cause no harm, thats what Attaran argue well.

    As far as proven ddt hazards, The main established hazard is that massive overuse is hazardous to only certain raptor species but not all birds, and there are persuasive arguments that that ban has contibuted to saving those rare species in the USA. Hazards to human health are to use Attaran’s words, not suppoted by persuasive evidence.

    Sorry about mis-spelling your name, I’m a one finger typist and sometimes misspell my own on the keyboard.

  10. d
    February 5th, 2004 at 10:24 | #10

    didn’t use DDT,” says AEI’s Roger Bate, malaria

    cases shot from a few thousand to 65,000 in one season. The reintroduction

    of DDT in 2000 cut malaria rates by 80 percent in 18 months. Despite such

    successes, anti-pesticide treaties and other regulations environmentalists

    imposed have hiked the cost and curtailed access to DDT

    prof Q- how does your resistance assertion explain this, and doesnt it suggest anti-GM activist are killing many people?

  11. John
    February 5th, 2004 at 16:00 | #11

    D, your quote is too foreshortened to provide substantive anything to respond to.

    However, Googling Roger Bate, he’s obviously an ideologue and is employed by an institution notorious for academic fraud and dishonesty (if you aren’t familiar with this, Google John Lott or Karl Zinsmeister). This means that I’d have to fact-check any claims he makes. If you want me to respond to something please provide a primary source in a reputable journal, such as the Attaran article.

  12. d
    February 6th, 2004 at 07:51 | #12

    Q

    Well here some recent professional comment that confirms the basic facts that you are having difficulty taking seriouisly. Note how this conflict with your assertions that resistance is a cause of the upsurge in malaria.

    Biomedica. 2002 Dec;22(4):455-61.

    Should the use of DDT be revived for malaria vector control?

    Curtis CF.

    London School of Hygiene and Tropical Medicine, London, United Kingdon.

    Indoor residual spraying with DDT was the principle method by which malaria transmission was eradicated or greatly reduced in many countries between the late 1940s and 1970s. Since then, decreasing use of DDT has been associated with a resurgence of malaria in India, Sri Lanka, former Soviet Central Asia, Zanzibar, Venezuela and several other Latin American countries. In India and Zanzibar, DDT resistance in vectors, as well as a decline in spray coverage, are probable causes of reduced effectiveness of DDT in recent decades. In southern Europe, eradication of malaria transmission was achieved by DDT spraying in the 1940s and 50s and eradication has been sustained by adequate treatment of imported human malaria cases. In the highlands of Madagascar and South Africa, recent reversion to DDT spraying has been successful in stemming resurgences of malaria. Continued use of DDT for vector control, but not for agriculture, is approved by the Stockholm Convention on Persistent Organic Pollutants. DDE residues in breast milk have been associated with DDT anti-malaria spraying in South Africa, but it is not known whether this is harmful. A claimed association of DDE residues with breast cancer have not been substantiated. There is a recent report of association of DDE residues with probability of premature birth; the possible relevance of this to anti-malarial use of DDT should be investigated. In Colombia, testing of the DDT stockpile for suspensibility, DDT resistance in Anopheles darlingi and investigation of the present affordability of widespread spraying with DDT, compared with alternative chemicals, are recommended.

  13. d
    February 6th, 2004 at 08:08 | #13

    Lancet. 2000 Jul 22;356(9226):330-2.

    Q

    Here another one on ddt, which I mentioned before. Are these enough to persuade you to address this issue instead of dismissing comments by denigrating people and institutions?

    DDT house spraying and re-emerging malaria.

    Roberts DR, Manguin S, Mouchet J.

    Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA.

    [email protected]

    This article discusses the role of DDT in the re-emerging cases of malaria

    worldwide. It is noted that malaria is reappearing in urban areas and in

    countries that previously eradicated the disease, including the Amazon Basin,

    South and North Korea, Armenia, Azerbaijan, and Tajikistan. In addition, the

    frequency of imported malaria has also increased in industrial countries.

    Although many factors contribute to such a phenomenon, the strongest correlation

    is with decreasing numbers of houses sprayed with DDT. Early studies of DDT

    showed repellent, irritant, and toxic actions that worked against malaria vector

    mosquitoes. Sprayed on house walls, DDT exerted powerful control over indoor

    transmission of malaria. However, since the ban of DDT in the 1970s and the

    implementation of alternative malaria-control programs there has been a global

    outburst of malaria epidemics. In view of this, it is recommended that the

    global response to burgeoning malaria rates allow for DDT residual house

    spraying where it is known to be effective and necessary. Regulations and

    policies of industrialized countries and international agencies that block

    financial assistance to countries that use DDT for malaria control should be

    eliminated.

  14. John
    February 6th, 2004 at 08:12 | #14

    D, you say “Note how this conflict with your assertions that resistance is a cause of the upsurge in malaria. ”

    Your cited experts Curtis says “In India and Zanzibar, DDT resistance in vectors, as well as a decline in spray coverage, are probable causes of reduced effectiveness of DDT in recent decades.”

    and

    “In Colombia, testing of the DDT stockpile for suspensibility, DDT resistance in Anopheles darlingi and investigation of the present affordability of widespread spraying with DDT, compared with alternative chemicals, are recommended.”

    I can’t see why you persist in pushing a claim that’s so obviously wrong. Clearly, there’s some disagreement about the importance of DDT resistance (that is, whether it’s so severe as to justify abandoning DDT), but no credible scientist denies it’s an important problem for DDT-based control of malaria. Looking beyond the specific case of DDT, the rise of resistance to insect and germ control measures is about as well-verified as any phenomenon can be, and the most attractive features of DDT (broad-spectrum and persistent) are precisely those that are conducive to the rise of resistance.

    Not even the junk science writers on whom Pearson relies deny resistance – they all ignore it. Given the way in which junk science works, it’s safe to assume that people like Pearson just don’t know what they’re talking about, but Milloy, for example, is a full-time propagandist. If he had a halfway credible answer on resistance he would have used it.

  15. John
    February 6th, 2004 at 08:34 | #15

    On Roberts et al. I’ll check the full article when I get time, but it’s not obvious that it adds anything to the paper by Attaran et al. which we’ve already discussed.

    To be absolutely clear, my position is

    (i) the ban on agricultural use of DDT was fully justified by the environmental risks it posed and by its contribution to the rise of resistance

    (ii) the rise of resistance, and not environmental pressure, has been the main reason for the decline in the use of DDT as an antimalarial

    (iii) until funding can be obtained for an equally effective and safer alternative, I support the continued use of DDT for indoor house spraying in poor countries

    It seems to me that we agree on (i) and (iii), and before continuing the discussion any further, I’d like you to confirm this.

  16. d
    February 6th, 2004 at 08:52 | #16

    My position is

    (i) regulation of unlimited agricultural use of DDT is justified by the environmental risks it posed and by its contribution to the rise of resistance, provided that availability and cost of ddt for house spraying is not unduely jeapardised

    (iii) until funding, assured and workable channels of supply and practical validation of effectiveness can be demonstrated for an equally effective and safer alternative, I support the continued use of DDT for indoor house spraying in poor countries

  17. d
    February 6th, 2004 at 11:41 | #17

    Another prfessional comment documenting the ant-ddt hysteria caused difficulties in India

    Should DDT be Banned by

    International Treaty?

    C.F. Curtis and J.D. Lines

    Trends in parasitology vol 16(3) p139, 2001

    DDT and vector control

    Ninety percent of worldwide malaria morbidity and

    mortality occurs in tropical Africa, but there has been

    little mosquito control there in recent years. The few

    African countries with house spraying programmes include

    Ethiopia, Zimbabwe, Botswana, South Africa and

    the highlands of Madagascar (see Table 1); elsewhere,

    many relatively small programmes1 using insecticidetreated

    nets (ITNs) have been set up in the past decade.

    During the 1960s and 1970s, some local field trials and pilot

    campaigns of house spraying in equatorial Africa using

    DDT or other organochlorines2 were very successful, for

    example, in the islands of Zanzibar and Pemba, where

    malaria transmission is naturally extremely intense, DDT

    spraying reduced prevalence of malaria parasitaemia to

    ,5%. This was an extraordinary achievement that has

    not yet been matched by ITNs. It is argued that African

    countries should not be denied the option of taking up

    house spraying with DDT, the most affordable insecticide,

    if, in the future, they can find the resources for it.

    Apart from South Africa and Madagascar, it is from

    Asia, Europe and Latin America that there are reliable

    data showing the impact on vector-borne disease of

    energetic use of DDT, and, in several cases, the resurgences

    that have followed its partial or complete withdrawal

    (Table 1).

    Presumably, these resurgences are at

    least partly because the additional costs of using alternatives

    to DDT necessitated a reduction in the area

    covered by spraying.

    (NOTE BENE)

    In India, partly because of the

    bad publicity created by the campaign against DDT,

    the percentage of householders allowing spraying

    of their houses has declined far below that achieved in

    the heyday of the Malaria Eradication Programme

    in the 1960s.

    (NOTE BENE)

    How harmful is DDT?

    DDT was used in agriculture in the 1950s in far

    larger quantities than against malaria mosquitoes10. In

    fresh water, it was lethal to fish and it accumulated in

    food chains and harmed the eggs of attractive top

    predators such as peregrine falcons. Consequently,

    DDT has been banned since the 1970s for agricultural

    use in most countries. However, the extent of harm

    caused by the use of DDT indoors for malaria control

    is not clear; in particular, it seems unlikely to be an

    appreciable source of DDT in food chains and a link

    between DDT and ill health in humans has not been

    convincingly demonstrated (Box 1).

    Who gets the benefit of the doubt?

    Proponents of the DDT ban stress the precautionary

    principle, ie. a biologically active chemical should not

    be used until it has been proved to be harmless. However,

    one cannot prove anything to be totally safe as

    one can never exclude the possibility of unanticipated,

    rare adverse effects.

    Opponents of the ban advocate a response based on

    weighing the known health costs against the known

    health benefits. This evidence, however, tends to be

    biased, because the benefits of DDT to malaria control are

    limited to some parts of the rural tropics, while the risks

    (if any) may be difficult to measure because they are scattered

    worldwide if, as WWF contends12, DDT spreads

    from inside sprayed houses to the whole ecosystem.

    Thus, there appears to be a conflict of interest. In

    malarious areas, where DDT-spraying remains the

    most cost-effective and practicable form of control, although

    human exposure to DDT is relatively high, it

    seems unlikely that any risks from this will outweigh

    the benefits of being protected against malaria.

    Therefore, a precautionary ban on DDT without adequate

    replacement would leave people in these areas

    less healthy than before.

  18. d
    February 6th, 2004 at 12:41 | #18

    Q

    Here is a peer reviewed commentary in the BMJ that states environmentalist pressure WAS a factor in discontinuation of ddt use in south Africa- the very issue you have continued to deny, and this confirms yet again that the comments by Lapkin and by Roger Bate which you have dismissed, are factually accurate on this point.

    At the time these articles were written there was a massive environmentaist campaign to totally ban DDT as part of the POPS treaty, so the facts of environmentalist ati-ddt actions are indisputable.

    BMJ 2000;321:1403-1405 ( 2 December )

    DDT for malaria control should not be banned

    Amir Attaran, director, international health research, a Rajendra Maharaj, deputy director, vector-borne diseases. b

    a Center for International Development, Harvard University, Cambridge, MA 02138, USA, b South Africa Department of Health, Communicable Disease Control, Private Bag X828, Pretoria 0001, South Africa

    Alternatives to DDT house spraying can substitute in some cases but not all cases. Case detection and treatment can help to lower mortality from malaria but can never stop morbidity that does not present in clinic. Insecticide treated bed nets, although promising, will often have the limitation that they protect one or two people under the net and not the entire household. Integrated vector management, an ecological approach against mosquitoes touted by DDT’s opponents,6 is as yet only an experimental strategy that has never been used in a national malaria control programme (for the 33 years since 1966, Medline, Biological Abstracts and CAB Abstracts list only 19 references on integrated vector management or control). And while house spraying with alternative insecticides to DDT can work, it is often fraught with insecticide resistance, and costs double or morea real constraint in African countries, where the health ministry’s budget may be less than £3 per person.

    South Africa illustrates these limitations in practice.

    *** Facing pressure from environmentalists, the national malaria control programme abandoned DDT in favour of more expensive pyrethroid insecticides in 1996.***

    Within three years, pyrethroid resistant A funestus mosquitoes invaded KwaZulu-Natal province, where they had not been seen since DDT spraying began in the 1940s. Malaria cases then promptly soared, from just 4117 cases in 1995 to 27 238 cases in 1999 (or possibly 120 000 cases, judging by pharmacy records). Other provinces experienced similar catastrophes, and South Africa was forced to return to DDT spraying this year. It had little alternative: no other insecticide, at any price, was known to be equally effective.

    This experience raises a challenging question: if the wealthiest, most scientifically advanced, and least malarious major country of sub-Saharan Africa cannot make do without DDT, how can superendemic and impoverished countries like Tanzania, Congo, or Mozambique do so? Should they be asked to?

    We conclude that the public health benefits of DDT amply outweigh its health risksif, indeed, such risks exist at all. For doctors or their banner groups such as Physicians for Social Responsibility to campaign otherwise is not only wrong but outrageously unethical. Risk-benefit trade-offs are part of public health and medicine, and we would be swift to condemn the malpractice of doctors who would from ideology deny their patients cyclosporin, tamoxifen, chlorambucil, azathioprine, or any other lifesaving drug known to be a human carcinogen.12 The situation with DDT and malaria is hardly different. The public health malpractice of its avoidance must stop.

    Acknowledgments

    An open letter of physicians on the DDT issue is available to read and sign at http://www.malaria.org/DDTpage.html. Over 400 signatures have been collected so far.

  19. February 6th, 2004 at 16:02 | #19

    As an aside, there is an interesting paper by V. Sharma (one of India’s top malarial experts) in the 2003 edition of Current Science which looks back at ddt use in India. As India has used ddt since the late 1940′s it provides an excellent test bed (with of course, disclaimers that there are differences between conditions in India and any-other country).

    The overall conclusion was that a number of factors, including resistance, had reduced ddt’s effectiveness to the point where a phase-out was probably preferable.

  20. February 6th, 2004 at 18:34 | #20

    The paper which I referred to in the post above is;

    DDT: The fallen angel by V. P. Sharma (Current Science, Vol. 85, No. 11, 10 Dec 2003).

    I think that the current ban on POPS with an exemption for ddt as a malarial vector control, is the best possible compromise.

    I’m also skeptical about the simple correlations being thrown around by some of the cited articles, ddt is very rarely used in isolation, rather it is (or should be) used in conjugation with a variety of other methods (such as attacking larval), and social changes also play a huge role in malaria transmission. So a change in number of malaria cases may not be due to the effect of ddt.

  21. d
    February 6th, 2004 at 19:41 | #21

    I accept the point that in India and Sri lanka overuse of ddt and vector resitance had a role in phasing ddt out, I’ve found this mentioned quite a few times, but in South Africa the story is different. In a 2003 S African Med Journal article by Williams there are details of the massive 1999-2000 epidemic that occurred after dddt was phased out in 1995 due to environmentalist pressures. In that outbreak the moquito resistance problem was due to pyrythrin resistance, and the outbreak was stopped (williams reports) due to spraying with DDT in 2001-2. That is the mosquitoes were susceptible to ddt.

    Also the review

    Lancet. 2000 Jul 22;356(9226):330-2.

    DDT house spraying and re-emerging malaria.

    Roberts DR, Manguin S, Mouchet J.

    states that resistance of Anopheles species to DDT is NOT a major barrier to its use in many regions, and again, contrary to Quiggin, states directly that decreased use (and consequent malaria increases) were the result of environmentalist pressures.

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