Tina Rosenberg's article, What the World Needs Now Is
published in the New York Times last year contains many factual
errors about DDT. The errors combine to present a false picture of a world where DDT is a magic bullet that could end malaria if only dogmatic environmentalists would allow it. After seven weeks one (and only one) correction was made to her article:
An article on April 11 about DDT and its effectiveness in controlling
malaria in developing countries misstated the position of an
international health organization on it. The Global Fund to Fight
AIDS, Tuberculosis and Malaria indeed plans to finance some DDT
spraying, in Somalia.
Many more corrections should have been made but were not:
It costs a quarter as much as the next cheapest insecticide. It is DDT.
Correction: Deltamethrin costs the same as
But at the moment, there is only one country in the world getting
donor money to finance the use of DDT: Eritrea, which gets money for
its program from the World Bank with the understanding that it will
look for alternatives.
The move away from DDT in the 60's and 70's led to a resurgence of malaria in various countries -- Sri Lanka, Madagascar, Swaziland, South Africa and Belize, to cite a few; those countries that then returned to DDT saw their epidemics controlled.
Correction: Only one of those countries moved away from DDT in the 60s and 70s. And that country, Sri Lanka, abandoned DDT in 1977 because the mosquitoes had developed resistance to DDT and a malaria epidemic had resulted. It was only by switching to malathion that they were able to control the epidemic.
In her 297 pages, Rachel Carson never mentioned the fact that by the time she was writing, DDT was responsible for saving tens of millions of lives, perhaps hundreds of millions.
Correction: Carson did mention the the triumphs against disease, writing:
The world has heard much of the triumphant war against disease through the control of insect vectors of infection, but it has heard little of the other side of the story - the defeats, the short-lived triumphs that now strongly support the alarming view that the insect enemy has been made actually stronger by our efforts. Even worse, we may have destroyed our very means of fighting.
Yes, one of the reasons that Carson was against the overuse of pesticides was that it would destroy their usefulness against disease.
Back to Rosenberg:
DDT killed bald eagles because of its persistence in the environment. ''Silent Spring'' is now killing African children because of its persistence in the public mind.
Correction: "Silent Spring" is now saving African children. If it hadn't been for bans on the agricultural use of DDT that Carson inspired, mosquitoes in Africa would have developed resistance as they did in Sri Lanka and many other places. The African children being saved from malaria with DDT spraying can thank Rachel Carson.
Ruckelshaus made the right decision---for the United States. At the time, DDT was mainly sprayed on crops, mostly cotton, a use far riskier than indoor house spraying. There was no malaria in the United States---in part thanks to DDT---so there were no public health benefits from its use. ''But if I were a decision maker in Sri Lanka, where the benefits from use outweigh the risks, I would decide differently,'' Ruckleshaus told me recently.
Correction: Mosquitoes in Sri Lanka are resistant to DDT so there are no public health benefits to its use.
But the most pernicious falsehood in the article is the title:
What the World Needs Now Is DDT
This is contradicted by information deep in the article, but Rosenberg fails to draw the obvious conclusion:
Malaria's status can be read in the aid figures. By the 1990's, it was almost completely ignored, and Africa's malaria-control programs disintegrated. In some countries, the entire federal antimalaria program employed only two or three people. ... Both bed nets and house spraying can be effective, and studies comparing costs differ on which is cheaper.
What the world needs now is not DDT but money to combat malaria. It doesn't matter that much whether it is spent on bed nets or spraying with DDT or other insecticides---they all work and the costs don't differ that much (and DDT isn't necessarily the cheapest solution). Rosenberg makes it look like that all that is preventing malaria from being controlled is environmentalists' prejudices against malaria and that just isn't true.
Fortunately other reporters have done a better job of reporting the facts than Rosenberg. A recent LA Times article gets it right:
DDT, banned in the U.S. for harming the environment, is still used in limited circumstances as a house spray, but it is not the miracle worker some suggest it could be if only Western aid groups would get behind it.
Today's weapon of choice in the war on malaria is a net treated with a biodegradable pyrethroid insecticide. The net works not so much because it forms a foolproof barrier against mosquitoes---it doesn't---but because the insecticide kills the bugs. The most astounding results come when treated nets multiply across a village. When net use reaches a tipping point of about 60% of households, they kill enough mosquitoes that the protective benefits extend even to the households without nets.
The errors combine to present a false picture of a world where DDT is a magic bullet that could end malaria if only dogmatic environmentalists would allow it.
I am very concerned that the false claims being put about regarding DDT may influence the spending on the additional funding to combat malaria promised by the US government.
It'd be tragic if, for example, the funding were made conditional on all recipient countries resuming outdoor spraying and this led to increase in resistance.
Tim, I hope you reformat this and send it to the New York Times as a rebuttal piece.
If I read the WHO's figures correctly, deltamethrin costs over three times as much as DDT.
Those figures date from 1997. Since then the prices have changed. My link has more recent prices.
Due to technical problems at this end I've been unable, until now, to access the linked pdf with deltamethrin cost. The article - by the reviled Tren and Bate, by the way and archived at Africa Fighting Malaria - does note the following re pyrethroids:
Once the South African Department of Health decided to remove DDT from malaria control, the obvious choice as a replacement was a synthetic pyrethroid insecticide. Those insecticides are considered better for the environment because they are less persistent than DDT and degrade faster. Almost all pesticide manufacturers have developed synthetic pyrethroid products for the agricultural market. Their application in agriculture can create problems for the public health use of the same insecticide. Even on Western farms where technological competence is high, it is difficult to prevent sublethal doses of pesticide from reaching some insects. In South Africa weak dilutions definitely escape as runoff from fields. The result is resistance among A. funestus to synthetic pyrethroids and a dramatic increase in the malaria infection rate.
As shown in Figure 1, the number of cases in KwaZulu Natal began to rise rapidly after the government stopped using DDT in 1996. By 1998 the number of cases was also increasing in Mpumalanga and Northern province. Between that time and 2000 there had been an approximate 400 percent increase in malaria cases in KwaZulu Natal, traditionally the province with the highest malaria rate. By 2000 the number of deaths in the province reached more than 340, over three times the level while DDT was in use.
A. funestus had not been seen in South Africa for about 30 years, and it was thought that the malaria control programs in the past had completely eradicated it in South Africa. However, it was widespread in neighboring Mozambique and resistant to pyrethroid insecticides. Thus the mosquitoes simply crossed the border back into South Africa and became established.
So, no matter the cost, the pyrethroids are of limited use because of resistance.
J F Beck,
Unless I'm missing something, none of the weapons against malaria are perfect. Each one has limitations that are amongst other things dependent on the local conditions.
To suggest that DDT is a panacea (which I imagine is Rosenberg's purpose) is questionable.
The problems you cite for pyrethroids - insect resistance and agricultural run-off contributing to development of resistance - are also problems with DDT.
So, no matter the cost, the pyrethroids are of limited use because of resistance.
All pesticides are of limited use because of resistance.
This should be a revelation to no one with a biology class under their belt.
Tim: The WHO estimates are actually from 1990.
I'm not so sure I'm convinced with the deltamethrin costing the same as DDT yet, it seems the link assumes equal lifetimes for both.
I'll have to look into it more, but I rather doubt the cost of synthesizing deltamethrin has been reduced to being as cheap as DDT.
The ITB's being as cost effective as IRS is probably true in the case of an 'average' (for SSA) sized house with one inhabitant.
Ian: As DDT isn't being used in agriculture, how would agricultural run-off be a problem?
The problem with using pyrethrum/ synth pyrethroids in agriculture in endemic areas is
the vectors become resistant not only to pyrethroids, but also cross-resistant to DDT as well. (as well as making ITB's less effective of course)
The problem with using pyrethrum/ synth pyrethroids...is the vectors become resistant not only to pyrethroids, but also cross-resistant to DDT as well...
If I can butt in then get quickly out (as I haven't had an entomology class in a few years),
Cross-resistance has always been a problem in insect pest control. We have a huge chemical pest-control industry because the little buggers are so quick to adapt to our poisons.
Anything you throw at them will eventually stop working; this is an underlying message in the campaign that is suppressed - sure, we can use DDT for a while to kill non-resistant species. Or we can use, say, Chlorpyrifos, Malathion or the permethrins. But they'll develop resistance to all these chemicals eventually.
OK, I'll shut up now.
Dano: yes, and now spinosad and many others. I thought that what we are really discussing here though is cost effectiveness; which seems rather hard to determine considering the WHO, etc... have very limited research/information with respect to this. But cost is a very crucial factor in the countries that malaria is hitting the hardest.
My apologies for the last comment messing with the site, I should have read the how to comment page.
Let me try the link again.
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