DDT Doesn't Just Irritate Environmentalists—It Annoys Mosquitoes Too.

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Defenders of the near global ban on DDT often hint that it actually saved the lives of millions of poor people because the pesticide was becoming ineffective due increasing resistance to it by mosquitoes.

A new study finds that one of DDT's main effects is not to kill mosquitoes, but to so irritate them so much that they do not even enter houses and huts that have been sprayed with it.

As Reuters reports:

Mosquitoes that carry malaria, dengue fever and yellow fever avoid homes that have been sprayed with DDT, researchers reported Wednesday.

The chemical not only repels the disease-carrying insects physically, but its irritant and toxic properties helps keep them away, the researchers reported in the Public Library of Science journal PLoS ONE.

They estimate that DDT spray reduced the risk of disease transmission by nearly three-quarters.

Malaria affects more 40 percent of the world's population, killing more than a million people every year, most of them young children.

DDT use has been discontinued in most countries because of fears the pesticide may cause cancer and because of its potential effects on animals such as birds.

But the World Health Organization last year recommended the use of DDT in places like Africa where malaria is still common, saying the benefits outweighed the risks.

For full study see PloS One here. For whole Reuters report go here.

Disclosure: I hate mosquitoes even if they do not carry malaria, dengue, or yellow fever. Despite my loathing for winged bloodsuckers, I am not in the pay of Big DDT nor any other pesticide company nor do I own any stocks in such companies.

NEXT: Thou Shalt Not Run Buck Naked

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  1. I don’t get how the greenies can keep repeating the lie that DDT hasn’t been banned. I can’t get any, and I’m damned tired of the ants coming into my house every summer.

    -jcr

  2. And since we know, for certain, based on decades of research and experience (such as in Sri Lanka) that mosquitoes actually do develop DDT-resistance, the conclusion we can draw from this is that mosquitoes evolve resistance toboth the irritating and toxic effects of DDT.

    In other words, there are two methods by which the elimination of the agricultural use of DDT by environmental activists has preserved its capacity to protect human life.

    Good post.

  3. 1, 2, 3, cue Tim Lambert.

    Ron Bailey is a lying pesticide monger and he’s mean to Rachel Carson too.

  4. Mr. Randolph,

    It’s been banned entirely in the United States, but not in the tropical countries where malaria is present. There, it’s been restricted to domestic use, as opposed to agricultural spraying.

  5. joe: Once again, you would actually benefit from reading the study before opining. From the PLoS One Study:

    Existing criteria for dealing with insecticide resistance have resulted in countries abandoning DDT when vectors became resistant to the insecticide’s toxic actions. The criteria include no allowance for the possibility that mosquitoes might become resistant to toxic actions and still be susceptible to a chemical’s spatial repellent or contact irritant actions. Given that spatial repellent action is the first order action of DDT residues, resistance to a toxic action may not signify that DDT will no longer exert control over malaria transmission.

  6. In your face, Flanders!!

  7. DISCLOSE!!! DISCLOSE!!!!

  8. Ron,

    You might benefit from bringing some critical thinking skills to the issue when you read something that confirms your biases.

    Once again, we know, for certain, beyond a shadow of a doubt, what happened in Sri Lanka. We know that the malaria rates rebounded once the mosquitoes became resistant to the DDT. We know that the mosquitoes developed DDT resistance, that its repellant and insecticidal properties were eliminated for that mosquitoe population.

    Nothing you’ve written remotely refutes this point. You’ve just descirbed another method by which the agricultural spraying that was eliminated contributed to reducing the effectiveness of DDT at protecting human life.

  9. If it softens the blow, Mr. Bailey, I take your word for it that the shoddy reporting you’ve done on this issue reflects your ideological biases, rather than your financial interests.

    Speaking of evolution, it’s always worthwhile to go back and read how Bailey’s anti-environmentalist spin on DDT has managed to survive by changing in an extremely hostile environment.

  10. Disclosure: I hate mosquitoes even if they do not carry malaria, dengue, or yellow fever. Despite my loathing for winged bloodsuckers, I am not in the pay of Big DDT nor any other pesticide company nor do I own any stocks in such companies.

    Me thinks he doth protest too much. No stocks, huh. How about call options?

  11. Hi Mr. Kettle, this is Pot. You two have so much in common!

  12. While the author puts a pro-DDT spin on the study, I took it as encouragement to seek DDT substitutes based on repellency instead of toxicity.

  13. ugh, even when I agree with Joe, the suffocating smugness is too much to take.

  14. joe-

    obsess much?

  15. joe: With all due respect, your immediate knee-jerk rejection of the PLoS One study indicates that you have precious little to teach anyone about critical thinking.

    Lamar: Yes, the study suggests looking for other pesticides that irritate mosquitoes. But in the meantime, the study also notes:

    To date, a truly efficacious DDT replacement has not been found and one may never be found because of the true nature in which DDT functions.

    Therefore it seems a reasonable conclusion that DDT should now be used until another substance that irritates mosquitoes is found. Again from the study:

    … the historical record of malaria control operations show that DDT is the most cost-effective chemical for malaria control. Even now DDT is still considered to be the cheapest and most effective chemical for use in house spray operations. Its long residual action when sprayed on inner walls further enhances its cost-effectiveness. These facts illustrate a remarkable paradox. The paradox is that DDT is widely considered to be the most effective chemical for malaria control and, unfortunately, is widely considered to have no important function other than killing mosquitoes. Yet, DDT does not provide quick knockdown or high mortality to mosquitoes. Observations reported here provide a new and clearer explanation of how DDT actually functions to control malaria transmission inside houses. The data obtained from both laboratory and field studies on the chemical actions of DDT confirm the probability model of Roberts et al. [18] which explains the roles of repellency and contact irritancy in disrupting malaria transmission. Success through the mechanism of spatial repellency means that DDT basically functions as a form of chemical screening, which stops mosquitoes from entering houses and transmitting malaria.

    Fortunately, the World Health Organization now endorses this view.

  16. Once again, we know, for certain, beyond a shadow of a doubt, what happened in Sri Lanka. We know that the malaria rates rebounded once the mosquitoes became resistant to the DDT. We know that the mosquitoes developed DDT resistance, that its repellant and insecticidal properties were eliminated for that mosquitoe population.

    We know for certain, beyond a shadow of a doubt that overuse of DDT in agriculture in Sri Lanka caused mosquitoes to become resistant to DDT… We know for certain, beyond a shadow of a doubt, that when DDT has been reintroduced in Sri Lanka for mosquito control in the absence of agricultural DDT use, that DDT continued to be highly effective for mosquito control and mosquitos developed no resistance!

    If you are arguing that using DDT for agriculture is bad, I agree with you. But it is a complete and total falsehood that mosquitos develop resistance to DDT when it is used to prevent disease. DDT, when used exclusively for mosquito control to prevent disease, works effectively without mosquitos developing any resistance. Period. End of story. Fact.

    And while there is no de jure DDT ban, the fact that most countries restrict DDT exports, and using DDT for mosquito control exempts those programs from international aid, means that there is a de facto ban on DDT.

  17. Rex,

    We are in agreement, then. It is the irresponsible area-spraying of DDT that brings about the resistance (and, in an all-too-rare example of interests converging, the majority of the environmental harm as well). The targetted spraying in and around homes doesn’t kill off enough mosquitoes to cause Darwinian evolution, nor does it put enough DDT into the ecosystem to cause the damage that has been observed.

    Don’t misunderstand me – like Rachel Carson, I am all for the use of DDT to protect human life, and fault only the agricultural use that caused so much environmental and human damage.

  18. For anyone interested in the “evolution” of my reporting on DDT see:

    May 23, 2007, “Celebrating Carson’s 100th
    Oct. 23, 2006 “Scientific Nuremberg Trials
    Jan. 7, 2004 “DDT, Eggshells and Me
    Jun. 12, 2002 “Silent Spring at 40
    Nov. 29, 2000 “Greens vs. the World’s Poor

    I note in passing that in my first report I wrote:

    Widely used as an agricultural pesticide, Carson accurately indicted DDT for harming various forms of wildlife. Less accurately, she and others in her wake fingered residual DDT as causing problems in human beings, including increased rates of cancer….it turns out that spraying small quantities of DDT on the interior walls and eaves of living spaces is one of the most effective ways to control malaria-carrying mosquitoes.

    I have not linked to various blog posts (too tedious to find them) on the topic, but in main you will see that my reporting has been vindicated, in part, by the fact that the World Health Organization now recognizes the importance and effectiveness of DDT house spraying.

  19. joe vs Ron Bailey > joe vs John

  20. Rachel Carson approved of the domestic use of DDT as well, and bemoaned its declining effectiveness due to its irresponsible use in agriculture. Preserving its “life-saving” (her term) features was one of her major arguments for restricting its use in Silent Spring.

    Keep this fact in mind, then read “Silent Spring at 40.”

  21. One claim made in the link is that there is no reason to believe that DDT use was reduced because of environmental concerns. Rather, DDT use was reduced because of resistance concerns. Another is that the “anti-environmentalists” (an unfortunate term) who claim otherwise are therefore guilty of a post hoc ergo prompter hoc fallacy.

    What of this?

  22. Post hoc ergo prompter hoc? After this, because quicker this? After this, because of teleprompter this? People called Romanes they go the house?

  23. The interesting thing about this debate is the heat on both sides despite the fact that everyone agrees on the basic facts…

  24. So I’m still confused about what Ron and Joe are arguing about. I read the original post, and each of the followup messages, and from them, I conclude this:

    1) Both agree that agricultural spraying is bad.
    2) Both agree that it works great when used for localized spraying of structures.

    The original post is specifically about the fact that DDT works great when used to spray structures.

    What’s the argument about? (For the record, I realize the overall vitriol is bleed-through from, well, every other post by Ron)

  25. I never used DDT on fields, and I can see how that might be an enviorenmental problem. but we sprayed the insides of barns and sheds, and the underside of all structures just once and got a decade of relief without any of it entering the ground or water supply.

    Being a greenie isn’t about doing what’s best, it’s a religion, and no more rational than any other.

  26. mith,

    Ron Bailey has spent two years accusing the people who brought about the ban on agricultural DDT of responsibility for millions of deaths, without any basis in fact. He had compared them to Stalin and Pol Pot.

    So when I see him continuing to push this bullshit, yeah, it’s annoying.

  27. “Being a greenie isn’t about doing what’s best, it’s a religion…”

    Statements like this one pop with some frequency here, and they’re as much dogmatic articles of faith as anything I’ve heard from all but the most fringe environmentalists.

  28. Ron, did you read the PLOS study? DDT was not the most effective chemical for IRS. Shouldn’t you be arguing for the use of the one they found most effective?

    And whatever the mechanism that DDT works by, mosquitoes can and do evolve resistance to it. The premise of your post seems to be that mosquitoes cannot evolve resistance to repellent effects. This is wrong.

    Read this paper for example — mosquitoes are still evolving resistance in India, despite a ban on the agricultural use of DDT.

    Carson’s grasp of the science was better than yours.

  29. Post hoc ergo prompter hoc? After this, because quicker this? After this, because of teleprompter this? People called Romanes they go the house?

    This is a really useful rule if you’re ever officiating a race and you want to make sure your guy wins even if he comes in second.

  30. Oh, and it’s “After this, therefore quicker than this.”

    Romanes eunt domus!

  31. Although it has little bearing on the dispute over whether household spraying of DDT was dramatically and wrongly reduced in recent decades, or if so what caused that recuction, I note with interest that Rachel Carson was “Widely used as an agricultural pesticide”. (Probably due to an errant copy-editor.)

  32. Ron Bailey has spent two years accusing the people who brought about the ban on agricultural DDT of responsibility for millions of deaths, without any basis in fact

    We set up a de-facto total ban on a chemical that, when properly used, probably would have prevented millions of cases of mosquito born illnesses. Many people die from mosquito born illnesses in places where a cheap, effective pesticide would be welcomed. I’m gonna put two and two together there, even without a specific scientific study to back me up. While I won’t call them little Eichmanns or anything, I’ve got to lean more in Ron’s direction.

    Perhaps we should have just banned area-spraying of the chemical, and not gone whole hog.

    Rachel Carson approved of the domestic use of DDT as well, and bemoaned its declining effectiveness due to its irresponsible use in agriculture.

    The problem, I think, comes about because those discussing and arguing for total bans on DDT typically cite Carson’s book as proof of how horrible it is. Admittedly most have probably never even read the book, and the rest probably conveniently ignore that she was arguing only against some of the uses of DDT.

  33. Post hoc ergo prompter hoc?

    Sorry about the typo–should be ‘propter’

  34. The correct spelling appears in the linked article. So anyway, now that we are all on the same page as far as the spelling, what of that charge?

  35. Sorry for the Latin humor–I couldn’t resist.

    I can’t comment on your question; however, as I eat DDT each morning with my cereal.

  36. mith,

    Why don’t you add in the millions of lives, past and future, saved by the preservation of DDT’s usefulness through the banning of agricultural spraying of DDT? The very life-saving process you mention only exists because of the activism of people like Rachel Carson. If you want to start assigning responsibility for lifes lost, honesty compels you to count lives saved as well.
    Perhaps we should have just banned area-spraying of the chemical, and not gone whole hog.

    Sure, absolutely. In hindsight, a less-strict regime would have preferable. But given the body count that we’d be looking at if there was no usefulness to DDT, people working on the issue with imperfect information erred on the side of caution. You are right, millions of lives will be saved through the responsible use of DDT. Millions, for decades to come. Thank you, Rachel Carson, for making this possible.

  37. mith, you kind of make Joe’s point and also answer your own question of why we’re still arguing about this topic (clearly the consensus is that widespread agricultural DDT use is BAD, focused use to stop the spread of malaria is GOOD). You make this point by casually adding an additional charge of abetting a holocaust to Rachel Carson, and everyone else who supported the ban. In general, “wow, it turns out we’re all in agreement…though you’re still a bunch of mass murderers” is not exactly settling a debate on terms agreeable to both sides.

    As it happens, there are many of us who are willing to defend Rachel Carson against charges of killing more people than Pol Pot, Hitler, Stalin and Mao combined (or something like that…I read someone claim that she was responsible for a billion deaths). The notion that environmentalists are a bunch of misanthropic monsters who tolerate, if not actively support, the deaths of millions of mostly brown and black people seems to have taken strong root here and elsewhere. People who argue that way should hardly be surprised by a vigorous response.

  38. The notion that environmentalists are a bunch of misanthropic monsters who tolerate, if not actively support, the deaths of millions of mostly brown and black people seems to have taken strong root here and elsewhere.

    Hmm. Speaking for myself only, most (though not all) of the serious (non-armchair) critics of Rachel Carson-on-DDT seem to think she meant well, but that she overblew concerns, leading to a virtual embargo, which in turn resulted in a lot of deaths because DDT was not available even for home use, in the places that needed it most. IF these arguments have merit, the number of unnecessary deaths could well run into the millions.

    I haven’t followed the whole controversy closely enough to weigh in on the validity of these points. But, while I’m sure you can point to raving Comment-Loons who accuse enviros of being Satan’s henchmen, isn’t it really a strawman argument to describe that attitude as widespread here?

  39. Hi Tim: I did read the paper. Did you? Overall protective factor for the 3 chemicals tested;
    DDT – 73%
    alphacypermethrin – 61%
    dieldrin – 92%

    But dieldrin was effective NOT because it was a irritant, but because it killed the suckers. And in any case the POPS treaty already bans dieldrin.

    And let’s not forget that DDT is CHEAP (as in the PLoS article which says “cheapest and most effective chemical for use in house spray operations” and is safer for humans.

    As for Rachel Carson’s science, she got some things right and some things wrong, e.g., there is no epidemic of cancer due to exposures to trace amounts of synthetic chemicals as she claimed.

  40. I see this as yet another cautionary tale about unintended consequences.

  41. Joe and Ramster:

    If you want to start assigning responsibility for lifes lost, honesty compels you to count lives saved as well.

    In hindsight, a less-strict regime would have preferable. But given the body count that we’d be looking at if there was no usefulness to DDT, people working on the issue with imperfect information erred on the side of caution.

    My issue is that the lives aren’t being saved. The US and other world governments still set up a system that prevents much of the world from producing and using DDT. A specific subset of environmentalists (certainly not all, but some) are the reason why we continue this system. To this day the mention of DDT tends to only bring total, irrevocable destruction of the environment to most peoples minds. Few people are actually aware of the fact that DDT can be safely used and it is universally the fault of that subset of environmentalists that that is true.

    You make this point by casually adding an additional charge of abetting a holocaust to Rachel Carson, and everyone else who supported the ban

    Actually, I’m not charging Rachel Carson with anything. I don’t think Rachel Carson single handedly banned DDT, nor did I say so in my above post. It was in fact whole organizations of people who took her writings (and the works of many others) and went to the complete, opposite extreme – pushing through the banning of all DDT use. Instead, people could have carefully weighed the facts and simply banned area-spray use of the chemical. These issues were specifically discussed during creation of the ban, but were generally ignored in the rush to “DO SOMETHING!”

    The notion that environmentalists are a bunch of misanthropic monsters who tolerate, if not actively support, the deaths of millions of mostly brown and black people seems to have taken strong root here and elsewhere

    I’m not going to use a broad brush like that, but you know what? There are groups within the broader category of environmentalists” who “actively support, the deaths of millions of mostly brown and black people” through the social and economic policy initiatives they push. The ban on DDT is just one of them.

  42. Ah, my apologies, I didn’t know that USAID had lifted it’s ban on using US “donations” for DDT, so actually much of the defacto ban is ended. My last understanding was that we were still against funding even after the WHO argued that we should use DDT.

    Still, you get quotes like this from people:
    Greenpeace scientists say they are still opposed to any easing of the restrictions on DDT.

    Dr David Santillo from the Greenpeace research laboratories at the University of Exeter says that USAID’s decision to fund the use of DDT is worrying.

    “That certainly raises some quite substantial concerns and if there’s substantial funding coming from the US to support that, then that does sound very much like a step in the wrong direction,” he said.

    “I think where that funding is better placed is in developing the availability of alternative strategies.”

    Source

  43. Another perspective from the academic blog Crooked Timber.

    http://crookedtimber.org/2007/08/09/ddt-as-a-repellent/#more-6118

    I don’t know enough about the issue to say who is right, but I thought you guys might like to take a look.

  44. Asish,

    Nice link.

  45. Neu Mejican,
    You speeled teh naem worng. Shuld be “Assish.”

  46. If I’ve missed this discussion somewhere among joe’s zillion posts (dude has TIME on his hands), forgive me. But I had to ask: is there any cause that could even vaguely be described as liberal that he won’t defend? And why exactly does he seem to LIVE on a libertarian website?

  47. Mith,

    How does Dr. Santillo’s support for the U.S. spending millions of dollars on efforts to fight malaria equate to him “actively supporting the deaths of millions of brown people?”

    It sounds to me like he actively supports efforts to prevent the deaths of millions of Africans.

    I used to get accused of wanting to see people fed into plastic shredders because I supported using “alternative methods” to liberate Iraq. How’d that turn out? Perhaps you should lay off accusing people of monstrosities for not buying into a partical political strategy.

  48. For the record, that’s 8 out of 47 comments from me.

    Try to pull yourself together, JustWonderin’. Some day, you will be able to go on with your life, despite the fact that these comment threads contain a diversity of political thought.

    Courage. You are not forgotten!

  49. Ron, the study found that the two insecticides with an irritant effect were LESS effective than the one without that effect. Why are you trying to spin this as DDT being better? Do you accept that mosquitoes can evolve resistance to irritants as well?

    On the subject of DDT and malaria, Carson was spot on, and subsequent events have completely vindicated her position. Overuse does hasten the development of resistance and restricting DDT to public health use does and has save lives. You have presented this study as somehow showing that resistance is not a problem and that’s just wrong.

  50. “joe: Once again, you would actually benefit from reading the study before opining. From the PLoS One Study”

    Haha, you just got deflated you pompous windbag. But, joe, I am sure you will quote something from wikipedia or a leftwing blog and then claim you know more about the issue than Mr. Bailey. I mean, what would a thread be without you claiming expertise in the subject being debated? I do seem to recall you mentioning you had a masters degree.

  51. And since we know, for certain, based on decades of research and experience (such as in Sri Lanka) that mosquitoes actually do develop DDT-resistance, the conclusion we can draw from this is that mosquitoes evolve resistance toboth the irritating and toxic effects of DDT.

    I think the point joe is that their resistance is a change in behavior…ie they are resistant because they avoid DDT.

  52. I think the point joe is that their resistance is a change in behavior…ie they are resistant because they avoid DDT.

    Joshua, as much as I would like to pile on Joe, I can’t. You are wrong. Mosquitos are resistant because they have adapted. The ones most susceptible died from DDT exposure, and the ones least susceptible survived and passed on their weak resistance to the next generation which repeated the cycle, and added a mutation that conferred a bit more resistance…

    Apprarently, DDT is annoying even to mosquitos that are resistant to it, so they take their blood sucking business elsewhere. I would expect that over time mosquitos would evolve to “not being annoyed” by DDT if other sources of blood are not easily available.

  53. joe | August 9, 2007, 10:26pm | #
    For the record, that’s 8 out of 47 comments from me.

    Ha. That is rich. joe, come on. how many postings do you average a day? How many hours do you spend away from H&R a day? Not counting sleep?

    It is amazing how many words you contribute here. Amazing.

  54. Once again, a Hit & Run comment thread becomes all about Joe.

  55. Ad homenims are a convenient fallback when you’ve been routed.

  56. I think this whole fuss has nothing to do with DDT; it’s due to human nature to pickon one person to home one loves to hate; hating so-and-so becomes a part of ones identity. It is a mental illness on both politcal sides.

  57. er ‘whom’. not ‘home’.

    anyway wrt DDT, Ron says it is cheap. But is that price the ‘let’s spray this field with an airplane’ price or the ”lets manually spray this complex home with one well paid expert guy who knows what to do.’ price? My limited undertanding in this respect is that DDT indoor spraying is more expensive than simply providing anti-malarial medicine.

  58. Joshua, as much as I would like to pile on Joe, I can’t. You are wrong. Mosquitos are resistant because they have adapted. The ones most susceptible died from DDT exposure, and the ones least susceptible survived and passed on their weak resistance to the next generation which repeated the cycle, and added a mutation that conferred a bit more resistance…

    Sigh…you are not getting it.

    The adaptation is avoidance.

    See some resistance is tolerance as you describe…ie they can survive exposure…another form of resistance is to change behavior and avoid it.

    The latter is the kind we are talking about here.

  59. You tout those numbers, but the problem is that anyone with basic stats can tell you there is a huge flaw in this study. Because of pseudoreplication, you can’t say whether that 12% difference is due to the treatments.

    Additionally, Dieldrin isn’t a commonly used pesticide, and is on the informed consent list because of it’s toxicity.

    This study doesn’t do anything to advance DDT as a chemical of choice; it just quantifies some of it’s interesting effects.

    More here:
    http://membracid.wordpress.com/2007/08/09/an-odd-email-campaign-by-africa-fighting-malaria/

    Also, there is plenty of documentation for behavioral resistance in mosquitoes.

    One of my biggest concerns is that they didn’t address the issue of cross resistance At All for chemicals commonly used in bednets.
    This paper:
    http://www.malariajournal.com/content/6/1/38
    references several articles documenting this statement:
    “Unfortunately, the knock-down resistance (kdr) gene conferring cross resistance to pyrethroids and DDT has become widespread in anopheline mosquitoes in Africa.”

    Using DDT has the potential to take away one of the best weapons for preventing malaria—insecticide treated bed nets.

  60. Also, a quick overview of insecticide resistance to DDT, including links to two studied in Tanzania and Indonesia where the repellency backfired:

    http://membracid.wordpress.com/2007/06/13/ddt-malaria-insecticide-resistance/

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