The Great DDT Hoax

Anti-environmentalist writers frequently claim that after DDT had all but eliminated malaria from Sri Lanka, environmentalist pressure forced Sri Lanka to ban DDT, leading to a resurgence of malaria:

Roger Bate in Politicizing Science: The Alchemy of Policymaking writes:

Some developing countries imposed a complete ban on the pesticide, as Sri Lanka did in 1964, when officials believed the malaria problem was solved. By 1969 the number of cases had risen from the low of seventeen (when DDT was used) to over a half million.

Walter Williams in in Capitalism Magazine writes

In Sri Lanka, in 1948, there were 2.8 million malaria cases and 7,300 malaria deaths. With widespread DDT use, malaria cases fell to 17 and no deaths in 1963. After DDT use was discontinued, Sri Lankan malaria cases rose to 2.5 million in the years 1968 and 1969, and the disease remains a killer in Sri Lanka today.

Ted Lapkin in Quadrant writes:

When Sri Lankan authorities agreed to ban DDT during the mid-1960s, rates of malaria infection exploded from twenty-nine cases in 1964 to over 500,000 a mere five years later.

In his book The Epidemiologists John Brignell writes:

1948 Annual malaria rate in Sri Lanka reaches 2.8million
1962 Publication of Silent Spring by Rachel Carson
1963 DDT reduces annual malaria rate in Sri Lanka to 17
1964 DDT banned in Sri Lanka
1969 Annual malaria rate in Sri Lanka reaches 2.5million.

Jim Norton lists even more examples.

Now when you think about it, the story that they tell just isn’t credible. If DDT spraying had almost eliminated malaria, and they got a new outbreak, then no environmentalists would be able to stop them from resuming spraying. So I went to the library to find out what really happened. And it wasn’t hard to find out. The definitive history of malaria is Gordon Harrison’s Mosquitoes, Malaria and Man and it turns out that, yes of course they went back to spraying. Harrison writes:

Sri Lanka went back to the spray guns, reducing malaria once more to 150,000 cases in 1972; but there the attack stalled. Anopheles culicifacies, completely susceptible to DDT when the spray stopped in 1964, was now found resistant presumably because of the use of DDT for crop protection in the interim. Within a couple of years, so many culicifacies survived that despite the spraying malaria spread in 1975 to more than 400,000 people.

So in 1977 they switched to the more expensive malathion and were able to reduce the number of cases to about 50,000 by 1980. In 2004, the number was down to 3,000, without using DDT.

And the reason why they stopped spraying in 1964? It wasn’t environmentalist pressure. With only 17 cases in 1963, they didn’t think it was needed any more. And this wasn’t an unreasonable belief. In the countries where malaria had been eradicated, once the number was this low, treating the remaining cases with drugs to kill the malaria parasite was sufficient to completely eradicate it.

Just to prove that there is no question about any of this, I have extracts from Harrison and two other supporting sources here.

The anti-environmentalist version of what happened is a hoax. That doesn’t mean that all the writers above were being deliberately misleading: they might be just repeating what another anti-environmentalist wrote and be unaware of the true story. AEI scholar Roger Bate, however, coauthored an entire book on DDT and Malaria which relies very heavily on Harrison’s history, citing him over twenty times. They conspicuously fail to mention that Sri Lanka resumed DDT spraying and that it failed because of resistance, instead claiming that

pressure not to use DDT may have been applied by western donors using resistance as a convenient argument. Recent evidence shows that even where resistance to DDT has emerged, the excito-repellency of DDT causes mosquitoes not to enter buildings that have been sprayed (Roberts et al., 2000). Under test conditions (see Grieco et al., 2000), for at least one type of malarial mosquito in Belize (the only country in which these tests have so far been conducted),DDT is far more successful than the most favoured vector control pesticide Deltamethrin. Hence it is unlikely that malaria rates would have increased (significantly) even if resistance were found.

But malaria rates did increase even though DDT was extensively used. Harrison has an entire chapter on this. How could Bate possibly not have noticed this? (And tests on a different continent on a different species of mosquito aren’t even close to relevant).

Comments

  1. #1 tc
    February 17, 2005

    Sri Lanka isn’t the only country in the world with malaria. There are many other countries where DDT would be effective, but who have been prevented from using it by environmental concerns – as your previous DDT post stated:

    When interviewed, I explained that we sometimes had to give up trying to convince a specific donor to financially support indoor spraying with DDT, if they flatly refused because of its perceived toxicity and ecological hazard. This has occasionally occurred in countries where the government wished to use DDT, and there was evidence that it was the best option for malaria-vector control.

  2. #2 Tim Lambert
    February 17, 2005

    OK, tc, tell me the names of these countries. And how much money have you donated to help fight malaria?

  3. #3 tc
    February 18, 2005

    The Economist, “DDT: A useful poison”, Dec 14th 2000 http://www.malaria.org/DDTEconomist14_XII_00.html

    In the early 1990s, for example, the United States Agency for International Development stopped the governments of Bolivia and Belize from using DDT. In Madagascar, the United Nations Development Programme tried to persuade the government to replace DDT with Propoxur, a less effective pesticide. To its credit, Madagascar refused. In Mozambique, both NORAD, the Norwegian development agency, and SIDA, its Swedish counterpart, said that they could not support the use of DDT, as it was banned in their own countries.

    EMBO reports 5, 847-851 (2004) http://dx.doi.org/10.1038/sj.embor.7400244

    DDT has a long history in Europe and North America; it was widely used in agriculture as a pesticide and was instrumental in wiping out malaria in these continents and in large parts of Asia and Latin America. Now, several African countries are seriously reconsidering the use of DDT to control malaria in their most afflicted territories. What makes DDT so attractive is that it is much cheaper than the commonly used pyrethroid insecticides and it is very effective. Moreover, mosquito resistance to DDT has not yet been reported, whereas it is rapidly spreading for pyrethroids. But the problem with DDT – now banned almost worldwide – rests with its persistence in the ecosystem, where it accumulates along food chains and causes widespread environmental damage.

    Building on past experience, this time DDT will be used more wisely, and only in small quantities for spraying homes to kill mosquitoes that rest on the walls and bite at night. This method has proved to be both remarkably safe for people – as it probably is for the environment – and effective in controlling the spread of infection. South Africa is leading the small patrol of nations that use DDT for routine malaria control, and the results speak for themselves. Malaria cases soared in the KwaZulu Natal province of South Africa after it stopped using DDT in 1996, and its reintroduction in 2000 brought the disease back under control. That is enough for other countries, such as Uganda and Kenya, to examine whether DDT could also work for them. The Ugandan Minister of Health, Jim Muhwezi, recently defended the plan to use DDT for indoor spraying in his country, emphasizing the need for a proactive rather than reactive strategy against malaria (Wendo, 2004).

    So why then is DDT not the weapon of choice to eradicate malaria? The answer is: simply because of its bad reputation in the USA and Europe. For this reason, major donors, such as the Global Fund and the US Agency for International Development, do not finance its use and the WHO dissuades poor countries from adopting it.

    Curtis, CF. “Should the use of DDT be revived for malaria vector control?” Biomdica 2002 22: 455-61. http://www.ins.gov.co/publicaciones/2002_biomedica_224.pdf

    In 1995, South Africa’s active environmentalist movement persuaded the government to ban DDT and to switch to pyrethroid spraying which, in short term trials, had appeared at least as effective as DDT. However, over the next four years, malaria case incidence increased at least fourfold. Considerable numbers of malaria deaths occurred, partly due to a very high level of resistance to sulfadoxine-pyrimethanine, a drug which was then the first line anti-malaria drug. Careful entomological studies showed that A. funestus had re-appeared, presumably by immigration from Mozambique, and was captured exiting alive from pyrethroid sprayed houses (15). Tests showed that these mosquitoes were resistant to pyrethroids, but not to DDT. In 2000, consultations led to agreement to switch back to DDT, which currently is purchased from China. Renewal of the use of DDT has been associated with a 60% reduction in cases during 2001 and disappearance of the problem of escape of A. funestus from sprayed houses.

    BMJ 2000;320:669 ( 11 March )
    http://bmj.bmjjournals.com/cgi/external_ref?access_num=10710569&link_type=PUBMED

    Its use there was stopped several decades ago, because 80% of the country’s health budget came from donor funds, and donors refused to allow the use of DDT. Mozambique’s earlier attempts to tackle the mosquito problem were hampered by South Africa’s aggressive policy to the country during the apartheid era, when troops were flown in to fight the Mozambique government and it carried out air raids to destabilise the regime.

    Curtis CF. Am. J. Trop. Med. Hyg., 66(1), 2002, p. 1
    http://www.ajtmh.org/cgi/external_ref?access_num=12135257&link_type=PUBMED

    It is rumored that international organizations tried unsuccessfully to pressure the Madagascan government into using a far more expensive insecticide than DDT for the house spraying program. However, the Madagascan government approved the use of DDT.

    And this is from the book by Spielman that you quoted earlier:

    p.165-166

    No chemical compares to DDT as a weapon against the resting mosquito. First, it is potent. Just two grams of DDT per square meter of wall surface is more than enough to kill a mosquito within its usual one-hour resting period. Second, it is inexpensive. It is also easily stored and transported, and relatively safe for the person doing the spraying. Best of all, it remains effective for many, many months.

    The total ban on DDT’s use in the United States deprived American public health officials of a weapon that could have been safely used. Even today, when there are many chemicals available to kill mosquitoes, DDT retains many advantages. It is the ideal insecticide of first use. This is becacuse the resistance that mosquitoes develop after being exposed to DDT does little to protect them against the other, more expensive insecticides that wait on the sidelines. However, mosquitoes hit first with one of those other compounds – such as malathion, sevin, or permethrin – develop a broader resistance that partially protects them from DDT as well. A spray program based on the use of chemicals in any of these alternatives also tends to be about three times as expensive as one based on DDT. When used correctly and with restraint, DDT appears to be irreplaceable in antimalarial programs.

    In the year 2000, DDT was nearly outlawed worldwide under the terms of a United Nations Environmental Program treaty. It was to be classified as one of the unsafe “dirty dozen” of the Persistent Organic Pesticides, known as POPs. In December 2000, however, a treaty conference held in South Africa agreed to a “dirty eleven”. DDT was excluded from proscription. The chemical is now manufactured only in China and India, and it is to remain available solely for use in antimalaria programs. This most recent battle over DDT’s status was intense and the outcome crucial for helping to protect human health around the world.

    p. 204

    The second cause is our mishandling of the medicines and insecticides that now are available. Indiscriminate and haphazard use of these chemicals has spurred the evolution of resistant strains of disease agents and vector insects. This woeful proess continues worldwide. Our best antimalarial drug, chloroquine, is losing efficacy. And the most powerful arrow in our antimalarial quiver, DDT, is being outlawed.

    A worldwide ban on DDT would be a mistake. When properly used, DDT can be uniquely helpful, especially in less developed countries where public health funding is exceeingly restricted. But the ban imposed by the United States and fierce advocacy by organizations devoted to environmental improvement have severely restricted its use. DDT is a prisoner of politics and may never escape. If it is banned worldwide, human lives would be placed at risk while this tool, which is safe when used properly, could save them.

  4. #4 Tim Lambert
    February 18, 2005

    tc, some of your sources completely downplay the problem of DDT resistance (for example, the Economist article). I think Spielman gives a really good account. (Except that DDT is not banned.) As far as I have been able to tell, Belize still uses DDT. Bolivia doesn’t, but that may be because of resistance.

    I think DDT should be used where appropriate and I don’t agree with aid agancies refusal to fund it, but folks like Bate have greatly exaggerated its effectiveness. What is really needed in the fight against malaria is not DDT but money.

  5. #5 Aaron Swartz
    March 8, 2005

    Michael Crichton: The ban on DDT was “arguably the greatest tragedy of the twentieth century….Since the ban, two million people a year have died unnecessarily from malaria, mostly children.” (State of Fear, qtd. in Harvard Magazine)

  6. #6 Philip Cassini
    March 19, 2005

    Well, I didn’t know much about this topic before, but judging from the evidence presented by Tim and TC, I’d say TC has me convinced. Tim, your reply to him is evasive but mostly acknowledges his argument. Do you have equally convincing sources and quotes?

  7. #7 Patrick
    March 21, 2005

    The “USAID does not finance its use” (from EMBO, the final bolded section) seems to be misleading. See:

    USAID website

    The essence seems to be that they think that insecticide treated nets are a better/cheaper method than spraying, but further that they do fund indoor spraying when they think it’s appropriate. They do appear to co-fund anti-malaria programs which involve DDT spraying.

    From the article:

    There are a few situations in which IRS with DDT is generally found to be appropriate. For example, in South Africa when certain mosquitoes developed resistance to the major alternative class of insecticides, the synthetic pyrethroids, DDT was used. Such situations are relatively rare, however, and demonstrate the value of the provisions of the POPs Treaty, which restrict and document use of DDT, but provide for its use when appropriate.

    Further the statement “Mosquito resitance to DDT has not yet been reported” (EMBO, first bold section) is simply false, unless the report is referring to some specific geographic context?

  8. #8 Singkong
    June 30, 2005

    Patrick:

    The essence seems to be that they think that insecticide treated nets are a better/cheaper method than spraying, but further that they do fund indoor spraying when they think it’s appropriate. They do appear to co-fund anti-malaria programs which involve DDT spraying.

    I wonder how easy it is to get people to use nets? I gather that they make it hot and stuffy, so people generally avoid using them. Indonesians generally don’t use them.

  9. #9 eric
    October 6, 2005

    DDT was banned because of a book from the 70’s that used lies and false science to discredit it.

  10. #10 Mark Schaffer
    October 6, 2005

    Eric,

    How do you know Rachel Carson’s book is full of lies and false science? Why should I believe your statement?

The site is currently under maintenance and will be back shortly. New comments have been disabled during this time, please check back soon.