DDT, Junk Science, Malaria, and the attack on Rachel Carson

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Some crazy claims have been made lately about Rachel Carson. How wacky are the claims?
Well, this wignut says Rachel Carson is on a level with Hitler, Stalin, and Pol Pot. Here’s another one, who also adds that “massive testing has documented that synthetic pesticides are no cancer threat to humans.”

Wow. Just…wow.
Think this is a fringe issue? You can also read this stuff in the New York Times, Washington Times, and CBS news.

I’ve been looking at this fight for a couple of weeks now; circling around the problem, and trying to figure out where to start. One of the top pages when you search on Google for either Malaria or DDT is Junk Science–a page that claims to “debunk” the DDT ban, claiming it’s “A Green Eco-Imperialist Legacy of Death.”

I’m going to examine their claims, since they seem to be the ringleaders. Their site is having intermittent server problems, so I’ll add a Fox News story written by one of the Junk Science “experts,” since it’s more likely to remain in a stable state.

What are the Claims?
The key claims I see repeated most often by JunkScience and DDT apologists are:
1. Banning DDT in the past caused the deaths of millions of people from malaria. (“environmental activists subsequently exported the ban to the rest of the world – with horrific consequences, including tens of millions killed and billions made ill by malaria over time” (Fox News)
2. DDT spraying now will save millions of people in the 3rd world from malaria (“anti-malarial use of DDT allows more healthy populations to work, generate wealth and climb out of the poverty/subsistence hole in which “caring greens” apparently wish to keep them trapped.”) (junkscience.com)
3. Mosquito resistance is not an issue.Resistance” is not an issue since this mostly takes the form of avoidance and keeping mosquitoes away from human prey is the intended object anyway” (junkscience.com)
4. DDT is safe.“There never was any scientific evidence that DDT posed a risk to humans or wildlife.” (Fox News)

I’ll leave out all the emotional nastiness of Photoshopping photos of Rachel Carson into wearing a pro-DDT t-shirt (I’m not kidding), and focus on the stuff that as an entomologist, I’m uniquely qualified to comment on. I know about bugs. I know about pesticides. I’ve taught parasitology for over 5 years. Let’s begin with the first two claims. [NOTE: this is a multipart series. Don't miss the other posts!]

Claim 1: Banning DDT in the past caused the deaths of millions of people from malaria. I’m going to break this into two pieces:

Claim 1a: Lots of people die (and have died) of malaria.
This is absolutely correct, and a tragedy. Good on them for being interested in what’s happening. However, the malaria clock on their page is blatantly bogus, and they even admit it!! In tiny tiny type at the bottom of that page:

“Note that some of these cases would have occurred irrespective of DDT use. Note also that, while enormously influential, the US ban did not immediately terminate global DDT use and that developing world malaria mortality increased over time rather than instantly leaping to the estimated value of 2,700,000 deaths per year. However, certain in the knowledge that even one human sacrificed on the altar of green misanthropy is infinitely too many, I let stand the linear extrapolation of numbers from an instant start on the 1st of the month following this murderous ban. — Ed.”

Claim 1b: DDT is/was banned worldwide:
Exotoxnet (Extension Toxicology Network) is maintained by 5 major land grant universities. Their DDT Entry:

“REGULATORY STATUS: DDT is no longer registered for use in the United States, although it is still used in other (primarily tropical) countries. It is in EPA Toxicity Class II, moderately toxic. DDT was banned from use in the United States in 1972, and remains banned barring public health emergency (e.g., outbreak of malaria).”

So, not only is DDT still allowed to be used against malaria elsewhere, if there was a problem in the USA, it could still be used. In fact, most pesticides have a “special use” clause, which allows them to be used even if they are banned.

DDT was named as one of 12 persistent organic pollutants to be banned worldwide in a 2001 Stockholm convention, but parties to the Convention can use DDT for “disease vector control” under guidelines for use set by the WHO (UNEP 2001). There was a great deal of rejoicing by Pro-DDT folks about the recent WHO announcement that they planned to re-implement DDT spraying.
Except…this comment in Lancet (Dec. 2006) from the Former Head of the WHO Global Malaria Programme says it all:

“A recent press statement from WHO about dichlorodiphenyltrichloroethane (DDT) and indoor residual spraying for malaria control caused a considerable stir, despite the fact that, in terms of policy, it merely re-iterated WHO’s endorsement of DDT as a useful insecticide for malaria control.” (Emphasis mine)

It wasn’t a change in policy–it was just a press conference. Ergo: Claim 1b is false.

Claim 1= (1a + 1b): Banning DDT in the past led to deaths of millions of people from malaria.
I’ve already shown that DDT was, and is, still being sprayed long after the 1970′s US ban. Using DDT did work to eradicate malaria in several countries—the incidence of malaria in parts of Central America and Taiwan decreased dramatically, and was completely eliminated in the US.

So, what made DDT fail as a control in Africa, since we still have malaria there? Was it the reduction of sprays in the 1970’s? If DDT spraying had continued, would malaria have been eradicated?

There were many reasons that past DDT spraying programs failed.
There isn’t only ONE kind of malarial parasite (Plasmodium).
There isn’t only ONE species of malaria vector (insect that transmits the disease).
And certainly, there is not just ONE kind of ecosystem in which birds, mammals (including people) and malaria interact.
Each system is different, and that is part of why DDT sprays worked in some places, and not others.

If you would like to read an excellent discussion of some of the immunological differences between the 3 major species of malarial parasites, I refer you to “Yellow Fever, Black Goddess” by Christopher Wills. One of the best layperson’s explanations of the amazingly complex human immune systems around, and he covers differences between the malarias thoroughly. (Learning the malarial life cycle is not for the timid; it’s not surprising it took decades to fully understand it.)

The mosquito vectors differ quite a bit, not just in their individual species, but also in behavior. You have to know a lot about a pest to know where to spray it, when it will be there, and what pesticides it’s resistant to (We’ll come back to the behavior and resistance puzzle later–it’s both interesting and complex enough for it’s own post.)

Malaria in tropical Africa is one of the most difficult to control. Two of the world’s most efficient vectors of malaria are present: An. funestus, a swamp mosquito, and An. gambiae, which breed in temporary pools wherever they occur (this includes footprints, irrigation furrows, potholes, etc.). This area of Africa has never had good malaria control—now or in the past. Why?

“Africa south of the Sahara, except for South Africa and some of the islands, was not incorporated into the global malaria eradication campaign of 1955–1969. Therefore, few of the countries developed the infrastructure to undertake IRS on a national scale.” (IRS= Indoor residual spraying; WHO 2005)

Clearly, cutbacks on DDT sprays weren’t a factor in the failure of malaria control in this large area of the continent. (And potential future sprays aren’t going to work well either.)

What other things may have gone wrong in the past?

“Context-specific factors giving rise to high malaria burdens in complex emergencies include breakdown of health services, concentration of non-immune refugees in malaria risk areas, malnourishment, siting of refugee camps on marginal land prone to flooding or vector breeding, and problems in gaining access or supplying medicine to the displaced population.”

The sad truth is, this is the story of much of Africa. Conflict, movement of refugees, and life on the margins. This is not the optimum situation for mosquito control.It isn’t terribly suprising, given the political turmoil in this area, that a major public health initiative failed. Houses with well-sealed windows and internal plumbing offer better protection against vectors than a UN-issued tent and a water bucket. Malaria is a disease the poor and displaced are especially vulnerable to.

I’ll save discussion of the failures of DDT because of insect resistance for the later discussion, but that certainly factored into the malaria control program failures.

In conclusion, other factors were at work than just the reduced spraying of DDT in the 70s and 80s. There are probably few places where it would have worked; the absolutist statements of “genocide” caused by the DDT ban are clearly way over the top.

Claim 3: DDT spraying now will save millions of people in the 3rd world from malaria.
So, let’s say DDT is approved and easy to get for malaria control. Problem solved? Not really.
In order to have a successful spray program, you need an infrastructure. Quoting again from Lancet (Dec. 2006), the Former Head of the WHO Global Malaria Programme:

“Indoor residual spraying is an effective intervention, provided a programme infrastructure can be set up and maintained to include trained sprayers, supervisors, managers, stocks, equipment, and vehicles, that roads allow access to every village at the right time at least once a year, and that insecticides are not diverted to agriculture.

The need to prevent diversion has been highlighted for DDT, but for malaria control it is equally important for other insecticides. Furthermore, especially in areas with intense and perennial transmission, it is essential to maintain the population’s long-term acceptance of spraying once or several times a year. In view of the difficulties encountered in maintaining indoor residual spraying, WHO has invested substantially in exploring other methods, especially insecticide-treated bednets.”

The problem of training and infrastructure is so huge, the FIRST conclusion and recommendation from the WHO working group was:

“IRS should only be adopted if the necessary infrastructure exists or can be created to achieve and sustain high coverage and where local vectors are susceptible to the insecticides used.”(IRS= indoor residual spraying; WHO 2005; p. 52)

Spraying isn’t just as simple as popping a cork and filling the sprayer. The applicators need to formulate the pesticide correctly, apply it with the correct method, apply it at the correct time, and in the correct place. That all takes training, and the issue of diversion of pesticides to agriculture is not a trivial one. (Especially if you are a subsistence farmer.)

It’s thought that much resistance to DDT developed initially from extensive use of pesticides in agriculture, in addition to malaria control programs. This rapidly created selection pressure for mosquitoes that not only had certain proteins (kbr) that could detoxify DDT, but that had different behaviors. Mosquitoes that didn’t rest inside houses became more important malaria vectors, for example.

Monitoring and managing insecticide resistance to all pesticides used in mosquito control is a major part of the WHO recommendations, and should be a part of all control programs. That takes even more training, organization, and resources.

Public acceptance of spraying is a major issue that I have yet to see addressed by the Pro-DDT camp. I can only imagine the outcry if a group of strangers in face masks arrived in my town and said they were going to spray a white power (the residual after a spray is quite obvious) in everyone’s house. No exceptions.

I predict it would not be a successful program (and not just because of the Michigan Militia.)

Two more points: DDT doesn’t absorb well onto western-style houses that have been painted with synthetic paints, so won’t provide much residual protection for those homes. (It does fine on traditional housing materials of mud and wood.)

Lastly, in “DDT for malaria control: the issue of trade (2007)” it was pointed out that countries choosing to use DDT may face sanctions on agricultural products from the EU. We don’t want to hurt the growing economies of Africa by clinging to an old solution.

Conclusion
I’ll stop here, since this is quite a lengthy post, and address insect resistance and DDT safety another day.

There is a lot of name calling and rhetoric being thrown around, but the real story is considerably more complex. DDT is not the major factor in the story of malaria—it is one piece of an extremely complicated disease puzzle.

I’m not denying there is data that DDT can make a difference; I’ll use one case study in Eritrea as an example of a success story (Nyarango 2006). They found that DDT, used as PART of an integrated strategy using bednets and other pesticides, effectively reduced malaria transmission by 80%. This is a country, however, that has a “well entrenched” health system in place, and has all the pieces to make the system work (and has been using DDT for the last 10 years, I’ll point out). Their conclusions from the Eritrea study?

In Eritrea, the use of ITNs contributed most to the reduction in malaria morbidity and mortality….Arguably the most cost effective tool in malaria prevention is the use of ITNs. (ITN=insecticide treated net)

It’s cheap, it works…and it’s been the main focus of the WHO for the last decade. I’m not seeing a problem here. What else worked?

In 2004, more than 80% of the breeding sites in Southern Red Sea, Northern Red Sea and Anseba were covered through active community participation . The remainder was subjected to temephos, a larvicidal chemical…The role of the community was central to the success.”

So, by physically changing the breeding environment for mosquitoes, they were able reduce adults emerging. And no DDT was involved, plus local people were able to have control over the program. An additional global review (Keiser 2005) found that environmental interventions could reduce malaria risk by up to 80%; simple changes like clearing vegetation around houses or putting screens on windows could be effective.

What about DDT in Eritrea?

“The final question to be explored was the role of each of the interventional measures in reducing morbidity or mortality. Within the limitations of the current study design it is evident that combining ITN use with IRS or other vector control measures did not confer added value to the outcome in malaria mortality or morbidity.” (ITN=insecticide treated net; IRS=indoor residual spraying)

DDT helps, but it isn’t a magic bullet. I wish that it was the panacea that the pro-DDT folks made it out to be—but it isn’t.

———-
Publications cited not available online:

Nyarango, PM, et al. A steep decline of malaria morbidity and mortality trends in Eritrea between 2000 and 2004: the effect of combination of control methods. MALARIA J 5: – APR 24 2006

DDT for malaria control: the issue of trade. Lancet 2007 Jan 27; 369(9558): 248

Keiser, J, et al. Reducing the burden of malaria in different eco-epidemiological settings with environmental management: a systematic review
LANCET INFECT DIS 5 (11): 695-708 NOV 2005

EDITED 6/17 to add link to the second in the series, DDT and insecticide resistance
EDITED 8/10/07 to add link to collection of all posts on this topic by myself and others.

51 thoughts on “DDT, Junk Science, Malaria, and the attack on Rachel Carson

  1. davidp

    Good post Bug Girl. Thanks.
    I’m looking forward to your post about mosquito resistance to DDT.

    I have read a good history of DDT resistance in Sri Lanka and its effects on malaria control (in “Mosquito”), but when someone said “it didn’t happen like that elsewhere” I didn’t have knowledge of another area’s history, so if you can talk about other regions that I’d be very interested.

    I guess Sri Lanka is used because it was a case of excellent conditions and implementation of the 1955-1969 DDT based eradication program, with minimal complicating factors, failing because of development of DDT resistance by the mosquitos. Cheating on the resistance tests was obviously not good implementation, but it happened after resistance had developed.

    I will be waiting for the resistance post.

  2. The amazing thing to me, from the perspective of 50 years out, is that they didn’t even *try* to control malaria with DDT in most of Africa in the 50′s and 60′s.
    It was written off as impractical from the start.
    There are actually multiple metabolic ways for insects to become resistant, and the behavioral resistance is fascinating (of course, I’m a behaviorist, so I would say that).

  3. davidp

    From my memories of “Mosquito”, the 1950′s and 60′s drive was a cold war tactic. I guess that since Africa was not prone to communist revolution at the time, they didn’t spend money on helping :-(.

  4. Absoloutely awesome post. I note (with dismay) many parallels between this debate and the creationism debate. The anti-science side spews out whole bunches of, at best, loosely related bad arguments. People like yourself can and do take the time to make the detailed, point by point case for why they are wrong. It’s really easy to be wrong in quick sound bites, and very difficult to be correct and accurate in the same format. I find it all quite frustrating. Also, we should fight hard to keep the other side from warping the meaning of the term ‘junk science.’ It’s a very useful concept, however they seem to like to apply it to mean “scientific studies that I don’t like the outcome on.’ Thus you see it applied in this sort of setting, as well as to a lot of studies of global climate change. Sigh.

  5. Randall

    Ahem. My second link above was to the wrong article. So…I found one of the papers you cited online. Two hisses for Elsevier.

  6. Some one asked–I once worked for BASF, also for Burroughs Wellcome (pharmaceuticals) and have also received funding for my research from agricultural foundations related to the pesticide industry.

    I’m off-green at best, so trying to call me an environmentalist shill really doesn’t fly :)
    I do, however, wear Birkenstocks.

    I also occasionally use pesticides in my garden, and will definitely be spraying next week, if those damn squash bugs don’t leave my zucchini alone. (Spraying with soap just made them clean.)

  7. Eduardo Ferreyra

    Sorry, Bug Girl, but when it comes to enthomology and DDT, I trust more late Dr. J. Gordon Edwards than you. Also, on toxicology of DDT I trust Dr. Thomas Jukes and not you, and Dr, Bruce Ames, and other really serious scientists.

    I would like to see what do you have to say about Dr. James DeWitt’s flawed study about thin eggshells, and the fraudulent study by Dr. Bitman about the same subject. Only he deliberately omitted to give chicks the normal calcium content. He was forced by a judge to remake his study and republish it.

    For sure, Nature rejected the new corrected paper, but it had published the fraudulent one. Some science backs your “debuking”!

  8. Sorry, Bug Girl, but when it comes to enthomology and DDT, I trust more late Dr. J. Gordon Edwards than you. Also, on toxicology of DDT I trust Dr. Thomas Jukes and not you, and Dr, Bruce Ames, and other really serious scientists.

    And we’re supposed to accept your personal predilection for these people as an argument for, what, exactly?

  9. I also occasionally use pesticides in my garden, and will definitely be spraying next week, if those damn squash bugs don’t leave my zucchini alone. (Spraying with soap just made them clean.)

    I’ve usually had very good luck with soap. This year, though, I got some earwigs that decided to declare a policy of scorched earth against my basil. I have a policy of mutually assured destruction, so the gloves went on and the Sevin and Diatomaceous Earth came out.

    They are now dead.

  10. First, Eduardo, it would help if you could actually spell Entomology :)
    Why would you want to take the word of a scientist from 45 years ago, and ignore all new evidence in the interim?
    Lastly, I haven’t presented ANY data about the safety of DDT *yet*, sot it seems that you are one of those folks who arrived with their mind made up.

  11. BG writes: “First, Eduardo, it would help if you could actually spell Entomology ”

    You might want to cut Eduardo some slack after you refer to Exotoxnet (it’s EXTOXNET). (The EXTOXNET page looks to be over 10 years old, by the way, so it looks like Eduardo isn’t the only one who likes old evidence.)

    BG writes: “It wasn’t a change in policy–it was just a press conference”

    The policy shift was announced by Dr Arata Kochi, Director of the World Health Organization’s Malaria Department in a press statement dated 15 September 2006. As it continues to be the first item at the top of the Global Malaria Programme’s home page, it’s obviously of some importance.

    The press statement reads, in part:

    “I asked my staff; I asked malaria experts around the world: ‘Are we using every possible weapon to fight this disease?’ It became apparent that we were not. One powerful weapon against malaria was not being deployed. In a battle to save the lives of nearly one million children ever year – most of them in Africa – the world was reluctant to spray the inside of houses and huts with insecticides; especially with a highly effective insecticide known as dichlorodiphenyltrichloroethane, or ‘DDT.’

    “Even though indoor spraying with DDT and other insecticides had been remarkably effective preventing malaria sickness and death where used, this strategy seemed to have been abandoned by most countries nearly 30 years ago. By the early 1980s, WHO was no longer actively promoting it.”

    Kochi thinks there was a de facto DDT ban but what would he know, he’s only the director of the WHO’s anti-malaria effort.

    BG writes: “Except…this comment in Lancet (Dec. 2006) from the Former Head of the WHO Global Malaria Programme says it all”

    The quote’s source, Allan Schapira, was not the head of the WHO’s Global Malaria Programme, he was (according to him) “coordinator, vector control and prevention, of the Global Malaria Programme”. He resigned due to policy disagreements with new director Kochi. As an obviously disgruntled former employee everything he says about the program is suspect.

    BG writes: “So, what made DDT fail as a control in Africa, since we still have malaria there?”

    DDT can only have failed to control malaria in Africa if an effort was made to control African malaria with DDT. This did not happen so DDT did not fail.

    BG writes: “There were many reasons that past DDT spraying programs failed.”

    Which DDT spraying programs failed? Bear in mind here that the need to rotate insecticides as mosquitoes become resistant has long been recognized.

    BG writes: “I’ll leave out all the emotional nastiness of Photoshopping photos of Rachel Carson into wearing a pro-DDT t-shirt (I’m not kidding), and focus on the stuff that as an entomologist, I’m uniquely qualified to comment on.”

    How does being an entomologist uniquely qualify you to address the malaria death toll, the DDT ban, DDT’s efficacy as a vector control measure, etc? Are you a malariologist?

  12. You sound like you’ve been getting your view of the situation from holocaust-deniers like Tim Lambert.

    We know what happened. Malaria was going down in new cases just like small-pox and polio.

    And then the ecology movement got going and with it the irrational fear of industrial society which expressed itself via neo-Malthusianism and a pathological fear of synthetic chemicals.

    Spraying policies changed after the release of Silent Spring and the cases of Malaria exploded.

    Where is your evidence that this is not a true and accurate picture of the history of this?

    This is what happened.

    You cannot hide that many dead black children under the floorboards.

    Few people are blaming Carson herself for the holocaust. This is a leftist trick.

    I for one blame leftist white guys. Who have far more tricks up thier sleeve then just a blanket ban.

  13. Beck said:

    “BG writes: “So, what made DDT fail as a control in Africa, since we still have malaria there?”
    DDT can only have failed to control malaria in Africa if an effort was made to control African malaria with DDT. This did not happen so DDT did not fail.”

    Actually, I make that point in my post EXACTLY. We agree on this point. You are correct on the spelling, although I was at least only one letter off. :)

  14. As was Eduardo.

    Okay, enough of the irrelevant trivialities. DDT’s use in the fight against malaria is an incredibly complex yet easy to understand topic. Here’s the quick summary from Gordon Harrison’s Mosquitoes, malaria, and man: A history of hostilities since 1880, inadvertently quoted by Tim Lambert (the quote relates to the faltering anti-malaria effort in Sri Lanka):

    The error came in part from the genuine difficulty of deciding just how large a defensible consolidation zone had to be, but in greater part from the manifold political and economic pressures to get off the DDT wherever it seemed even marginally possible.

    Silent Spring inspired environmentalists applied the political pressure. The pressure to “get off the DDT” was not unique to Sri Lanka; it was universal. This pressure caused the two biggest players in the anti-malaria effort, USAID and the WHO, to shun DDT. Thus a de facto DDT ban was born.

    Bug Girl I think you made a good faith effort to produce a balanced post but your conclusions are influenced both by your existing anti-DDT prejudices and by reliance on misinformation from the likes of Tim Lambert. Now whereas both sides of the DDT debate are guilty of misrepresenting the issues, it is inexcusable for academic and scientist Lambert to continue to crank out “information” he knows to be incorrect. I can only assume that Scienceblogs.com, which claims to be a reputable source of science information, continues to allow Lambert to do this because his traffic generates revenue. Thus, lies make money and the truth be damned.

    If you’d like to discuss any of this “off the record”, email me at rwdb-at-budweiser.com.

    The link for the Harrison quote:

    http://rwdb.blogspot.com/2007/06/big-tobaccos-anti-malaria-effort.html

  15. I’m really not seeing where I’m anti-DDT.
    I haven’t said it should not be sprayed at any point. I’m pointing out it isn’t the cure-all it’s portrayed to be, and that MANY of the claims made (in major media outlets) are flat out false.

    It looks to me like you have an issue with *Lambert* which is making you project all sorts of ideas onto me.

    I’d address more of your points, but I actually have a job, a family, and a life, in addition to a blog. Perhaps later this weekend.

  16. Steve Bloom

    FY all, Eduardo’s web site shows him to be an Argentine wannabe Steve Milloy. Interestingly, the Ferreyra family fortune seems to have it’s source in the cement kiln business (the worst industrial source of CO2).

  17. Dean Morrison

    Great post Bug Girl.

    Unfortunately in the UK we have a bunch of supposedly ‘ex-Marxist’ politicos who seem keen to be part of the CEI echo chamber . ‘Spiked’ magazine is just one of its outlets, and has been pushing the same Carson defamation rubbish for a couple of months now.

  18. Dean Morrison

    Sorry – meant to post an example link:

    I’ve been tryin to expose this nonsense on Ben Goldacre’s ‘Bad Science’ forum:
    Badscience

  19. George

    “I’m going to examine their [Junk Science] claims, since they seem to be the ringleaders.”

    You got that right.

    I once had an argument with a guy about the effects of DDT on falcon reproduction and he provided a link to Junk Science as ‘proof” that DDT could not have been the reason for the decline in falcon populations, since, as Junk Science says, “DDT causes no eggshell thinning.”

    When I went to junk Science, I found a bunch of references to studies performed on chickens!

    Yes indeed. As everyone knows, chickens are just raptors in chicken suits (ie, with exactly the same biochemistry).

    That was my first (and last) visit to Junk Science.

    It is aptly named.

  20. Valuethinker

    Can I make a plea for the natural environment in this?

    It seems to me that if we invent a chemical, call it DDT, which is persistent and long lived in the environment (say 40 years and counting) and we know that it concentrates in the food chain and leads to the deaths of birds, and maybe mammals (the former is certainly true)

    that we ought not to use that chemical?

    If the consequence of spraying DDT is the death and extinction of numerous bird species, isn’t that a greater cost than any benefit we could secure from it?

    Particularly in light of the fact that we know mass DDT spraying was ineffective in controlling malaria (due to the development of malaria-resistant insects)?

  21. While I do agree (to some degree) that the claims DDT would solve all the malaria problems in the world and save millions are inflated, I still cannot condone the dissemination of inaccurate information on DDT or any scientific matter, which Ms. Carson is IMHO guilty of.

    Let me take on a few of these things:

    DDT is a highly effective insectaside which has proven to be safe for humans, and numerous studies have failed to show a consistent and significant link to cancer. There have been several studies which have shown that even extremely high chronic doses in humans result in relatively small health affects. And these doses are far less than what would be expected in a general population of an area using DDT.

    DDT may have affects on the egg shells of birds, but does this mean that it should be banned, or even banned in many situations? For one thing, the degree of affect is not established and it certainly is not the sort of thing that would wipe out a bird population in a short time.

    This means that it’s use should be limited in areas with endangered bird species, that it should be monitored and that measures should be taken to prevent or limit the runoff into bodies of still water, where it’s chemical half-life and tendency to collect in organisms can cuase issues.

    And as far as resistance? DDT is not a magic bullet, but it’s been demonized far too much. The best tactic in combating evolving resistance in organisms is to be sure you have a well-stocked arsenal of control measures. Taking DDT off the table is not justified and not prudent, even if it is not a silver bullet.

    My biggest problem is that it has been demonized so badly that most people, not even knowing much about it, assume it has been proven to be very dangerous to human health. The average person upon hearing the letters DDT may say something like “Isn’t that that horrible cancer causing insectaside that they banned along with asbestos and plutonium? Only worse?”

    I realize bug-girl likes bigs and DDT kills bugs and it’s overuse can be dangerous to an ecosystem. But despite her love for insects, that does not change the fact that there are plenty of times when insects are a major health problem for humans or can cause massive damage to crops etc.

    There is one thing thats pretty hard to escape: Sometimes you gotta kill some insects

    Ps. I know there are not any citations here, but I am actually working on a posting to my own blog on this same issue which willhave much more info than i have off the top of my head now.

  22. Dr. Buzz. you clearly missed the second part of the post (where I discuss insecticide resistance) and where I reiterate that I am not calling for a ban, just cautious use.

    Which seems exactly what you are asking for.

    Sigh.

  23. Not a scientist, but I’m old enough to have witnessed the relatively fast recovery of Bald Eagles, Ospreys and Brown Pelicans from severe declines in the U.S. after DDT was banned. Without doubt, lipophillic poisons do harm people and animals wherever they are used, through bioaccumulation. Not only are the top food-chain organisms effected, but also simpler ones such as arbuscular mycorrhiza, which are very important to food crops and land flora in general. Yet absolutely no pesticide is a panacea, nor species-specific. Not to devalue human life; I’m still staking hopes in a malaria vaccine, still a few years off.

    (Since I’m not proving any points nor providing sources, it’s better that I end this post, before I really show my passion….)

  24. I agree with you Ken, but I don’t think that I’m going to convince many people that don’t *<em>already</em>* have a belief in the intrinsic value of nature by presenting that evidence.
    Most of the folks arguing for DDT are strict utilitarianists. Many of them say openly a few fish and birds is a small price to pay for preventing a terrible human disease. (It’s hard to disagree if you’ve ever seen a child struggling with malarial fever.)
    It’s an emotional argument, and asking for careful long term thinking about global consequences (as you are doing) probably isn’t going to work. Even if that’s what we <em>should</em> do :)
    I do make the point that DDT isn’t a panacea in the 2nd post in this series:
    <strong>DDT and insecticide resistance</strong>
    http://membracid.wordpress.com/2007/06/13/ddt-malaria-insecticide-resistance/
    I have been busy, but will work on the 3rd part, human health issues, this weekend.
    Personally, I think the fact that DDT bioaccumulates, and that is a bad thing, is so self evident, I don’t see value in covering it.

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