Politically Based Medicine at the WHO

The New York Times reports:

Dr. Kochi said the most substantive change in the W.H.O.’s guidelines on the use of insecticides would extend the reach of the strategy. Until now, the agency had recommended indoor spraying of insecticides in areas of seasonal or episodic transmission of malaria, but it now also advocates it where continuous, intense transmission of the disease causes the most deaths.

Dr. Kochi’s new policies and abrasive style have stirred the small world of malaria experts. Dr. Allan Schapira, a senior member of the W.H.O. malaria team who most recently oversaw its approach to insecticide spraying, resigned last week.

Reached Thursday on his cellphone, Dr. Schapira declined to comment on his reasons, except to say that they were professional. He did not return messages left Friday.

His successor, Pierre Guillet, a medical entomologist, said Dr. Schapira quit because he was uncomfortable with the new approach on insecticide spraying.

There are fierce debates among experts over when it is best to use indoor spraying or mosquito nets impregnated with insecticides that last up to five years, though most agree that both spraying and nets are important tools.

Dr. Kochi said in an interview that half the professional staff of the W.H.O.’s malaria program has left “one way or the other” since he took over in October. He described Dr. Schapira as the “main brain” behind the past approach.

“He was professionally insulted by me,” Dr. Kochi said.

In answer to a question, Dr. Kochi acknowledged that he had indeed told members of the staff in meetings that they were stupid. “They are very inward looking, and they do not communicate outside the malaria field,” he said. “It’s ridiculous.”

Dr. Kochi earlier headed the W.H.O.’s tuberculosis campaign until he was forced out after his blunt manner alienated important partner organizations.

So Kochi, coming from outside the malaria field, reckons he knows more about it than the people in the field. Well, that’s possible, but the press release he put out does not inspire confidence:


WHO actively promoted indoor residual spraying for malaria control until the early 1980s when increased health and environmental concerns surrounding DDT caused the organization to stop promoting its use and to focus instead on other means of prevention. Extensive research and testing has since demonstrated that well-managed indoor residual spraying programmes using DDT pose no harm to wildlife or to humans.

The fact is that until 1994, DDT was the WHO’s insecticide of choice for malaria vector control. One of the reasons that it was downgraded to just be one of the recommended insecticides was the evidence of possible health risks to humans. Since then there has been more evidence of health risks. Malaria is far more damaging to the health than any risks from DDT, but this is a reason to consider other insecticides if they are as effective as DDT.

Nor did WHO stop promoting DDT. Similar claims have been made by Senator Tom Coburn, who said

The WHO and other elites have stigmatized DDT

And Richard Tren of Africa Fighting Malaria, who wrote:

The World Health Organization, World Bank and United Nations Environment Programme are all against the use of DDT

Alan Schapira rebutted such claims in November 2004:

WHO has never given up in its efforts to ensure access to DDT where it is needed.

And in 2006:

“DDT has become a fetish,” adds Allan Schapira of WHO. “You have people advocating DDT as if it’s the only insecticide that works against malaria, as if DDT would solve all problems, which is obviously absolutely unrealistic.”

And the WHO’s 2004 statement on ITNs (nets) vs IRS (spraying) clearly supports IRS in regions of unstable transmission:

For example, in some countries, especially in Southern Africa and in the Horn of Africa, proportions of the population are exposed to unstable or epidemic malaria. In these circumstances, IRS has some important advantages: it has rapid and reliable short-term impact, and it can be targeted to the communities at highest risk, on an annual basis and in response to changing transmission patterns. IRS is, on the other hand, relatively demanding in terms of the logistics, infrastructure, skills, planning systems and coverage levels that are needed for a successful and effective operation. Nevertheless, such systems have been successfully and effectively maintained for many years in some African countries, especially those that contain large populations exposed to unstable malaria. Every effort should be made to sustain these systems in the future.

Unfortunately the falsehood in the WHO press release led to this sort of inaccurate reporting: (from Australia’s ABC)

DDT, the long-banned insecticide blamed for killing birds and other wildlife, is now approved for use indoors to fight malaria, says the World Health Organization.

But it gets worse. The press release continues:

“Indoor spraying is like providing a huge mosquito net over an entire household for around-the-clock protection,” said U.S. Senator Tom Coburn, a leading advocate for global malaria control efforts. “Finally, with WHO’s unambiguous leadership on the issue, we can put to rest the junk science and myths that have provided aid and comfort to the real enemy — mosquitoes — which threaten the lives of more than 300 million children each year.”

And later even quotes Richard Tren. No wonder so many of the WHO’s malaria experts resigned. Instead of trying to knock some sense into Coburn’s head, Kochi threw his own malaria experts to the wolves.

But hey, despite all this maybe there is some science behind the new policy? Let’s check. WHO’s 2004 statement on ITN vs IRS in areas of stable transmission:

However, in most countries of Africa south of the Sahara, the vast majority of the rural population is exposed to stable malaria and the systems needed for large-scale IRS do not exist. In these countries, the critical question is not whether one intervention is slightly more powerful than the other, but which of the two offers better prospects of achieving high nationwide coverage and long-term sustainability. In these circumstances, ITNs have important advantages. As well as being less demanding than IRS in terms of infrastructure and organization, ITNs allow vector control resources to be targeted toward those most at risk in stable endemic settings, i.e. pregnant women and young children, hence best use can be made of initial resources. ITNs protect people who use them, and they also have community level benefits, giving protection to people without nets in nearby houses. These benefits are thought to increase incrementally with coverage, across all coverage levels, and will contribute to early gains in equity as programmes scale up. The minimum coverage at which ITNs might have a significant community effect at programme level is not yet established. ITNs can give protection of longer duration than IRS since a net in good condition gives reduced but still significant protection to the user even after the insecticide has worn off. This advantage will be further strengthened by the emerging development of Long Lasting Insecticidal Net (LLIN) technology, which greatly extends the effective life of the insecticide.

And the report from the WHO Study Group on malaria vector control, published earlier this year:

However, the success of IRS depends largely on the mosquitoes resting
indoors before or after feeding — not all species do this
naturally and the excito-repellency of DDT and pyrethroids may
dissuade mosquitoes from resting long on sprayed surfaces. Other
requirements include the need that human shelters have walls to be
sprayed, access to the interior of all houses, and a relatively stable
human population without a high frequency of replastering of sprayable
surfaces. The conditions for “eradication” were not met in all
malaria areas, especially in Africa, where serious efforts were never
mounted. …

Moreover, the experience of long-term use of IRS by organized antimalaria
campaigns in many parts of the world has frequently shown a progressive
development of people’s fatigue and reluctance to allow intrusion into
their homes. This phenomenon may be less likely to occur with the use
of ITNs, which are far more under the control of households. …

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, except for a number of pilot projects aimed at examining the
feasibility of interrupting malaria transmission. Therefore, few of the countries
developed the infrastructure to undertake IRS on a national scale. As a
consequence, most countries have concentrated their malaria control efforts
on the development of primary health care to make appropriate disease
management accessible to the whole population, limiting mosquito control
to urban areas and certain economic development projects.

This situation weighted heavily in favour of ITNs versus IRS as the malaria
vector control measure of choice for tropical Africa. Moreover, the personal
protection afforded by ITNs made it possible to plan its implementation
as a promotional programme aiming at a progressive increase in coverage
before reaching the level of coverage necessary for community protection.

OK, what does the new position paper say? What scientific evidence supports the change of policy?

There is no definitive conclusion on the comparative cost-effectiveness of IRS versus ITNs since it depends on the local context. Thus, countries should maintain IRS in their malaria control strategies, where indicated, until further information, including locally-generated data, is available and can be used to fine-tune national interventions and better guide resource allocation.

In other words, let’s collect the evidence to see if increased use of IRS is a good idea.

Resistance to DDT and pyrethroids in major malaria vectors has been found throughout West and Central Africa, in some areas at a high level, as well as in several parts of Eastern and Southern Africa. …
A comprehensive assessment of resistance at the local level must be carried out before planning any IRS programme, especially in West and Central Africa.

In other words, let’s collect the evidence to see if increased use of IRS is a good idea.

The choice of IRS, or any other vector control intervention, must be made by careful consideration of the factors mentioned above, and will depend on the local context and the strategic objectives, whether elimination of local transmission, transmission control, or personal protection. The role and limitations of existing malaria vector control interventions and personal protection measures
have been reviewed by a WHO Study Group and a comprehensive report recently published (15).

That’s the report above which said that ITNs were the vector control method of choice for tropical Africa.

IRS is indicated only in those settings where it can be implemented effectively, which calls for a high and sustained level of political commitment. Transmission control operations based on IRS, or any other vector control intervention, have to be maintained at high coverage levels for extended periods of time, for as long as impact is needed.

IRS requires effective leadership and management for planning, organization and implementation. Operations must be managed by skilled professional staff, based on an analysis of local epidemiological data and a sound understanding of transmission patterns, vector behaviour and insecticide resistance status. Significant strengthening of human and technical resources, accompanied by sufficient financial resources, is needed to develop or reorganize existing IRS operations.

So, the old policy was that ITNs should be used in areas of stable transmission because there wasn’t the infrastructure to support IRS. And the new policy is that IRS should be used in areas of stable transmission provided that there is sufficient infrastructure. In practice this seems to amount to almost no difference.

John Quiggin comments on this matter:

It’s far from clear that the change is backed up by a scientific analysis of the relative cost-effectiveness of the options. But, as with all the fads and fashions in areas like this, cost-effectiveness is not necessarily the most relevant criterion. The US appears willing to put in a substantial amount of extra money, and the US wants to push DDT. So, it’s probably better to please the donors, than make a stand on the science and risk losing the money.

Comments

  1. #1 Joel Shore
    September 19, 2006

    One of the weirder aspects of this story for me came from this article in USA Today where it said: “‘There is no credible evidence that DDT is harmful to human health,’ said Richard Tren, director of Africa Fighting Malaria, who attended the WHO’s press conference and was called on by WHO officials to answer technical questions.” To me it seems a bit strange that WHO officials are calling on someone who runs an astroturf pro-free-market group like AFM to answer the technical questions raised.

    On the other side of things, this article from Reuters notes:

    In Washington, the director of the Sierra Club’s environmental quality program gave muted backing to the plan.

    “Reluctantly, we do support it,” said the group’s Ed Hopkins. “Malaria kills millions of people and when there are no other alternatives to indoor use of DDT, and where that use will be well-monitored and controlled, we support it.”

    Hopkins stressed the need for safer alternatives to DDT, “because DDT is not a silver bullet to solve this problem.”

    So, I am not sure what to make of it overall…but I agree with you that there is some concern that politics may be trumping science.

  2. #2 Dano
    September 19, 2006

    Joel,

    One of the weirder aspects of this story for me came from this article in USA Today where it said: “‘There is no credible evidence that DDT is harmful to human health,’ said Richard Tren,

    This type of statement is typical of the per-type atomists and mendacicizers. Technically, DDÉ is the harmful part (the breakdown product). So, technically, DDT is not harmful. Toodle-pip!

    I certainly smell something fishy here and I’m going to forward this Tim post to one of my Env-Chem buddies and see what they have to say. Certainly we need to look at controlling malaria, but the news reports on the radio all sound like they transcribed marketing material from AFM…

    Best,

    D

  3. #3 per
    September 19, 2006

    hmmm…
    40+ years of DDT use, including real heavy use before the ’80′s, and the best evidence that Timmy can come up with is a dead link, a news report on the bbc- which acknowledges the contradictory nature of its findings, and one report from September 2006, which isn’t formally published in print yet.

    just imagine if DDT actually were toxic…

    oh yeah, and all those negative reports; they would be the great conspiracy :-)

    do let us know what your env-chem friends say, dano. I will be amused to hear chemists commenting on epidemiology.

    toodle-pip !

    per

  4. #4 Joel Shore
    September 19, 2006

    Per,

    Without taking a position on whether DDT is toxic or not (unlike you, I don’t pretend to know things I am not qualified to know), I wonder why:

    (1) You found a dead link where I found a perfectly fine one.

    (2) You object to a paper on the grounds that it “isn’t formally published in print yet”. It has been accepted by the journal and has even published there online already. You do like to nitpick much and raise completely meaningless objections, don’t you? You’ve honed your skills well from climate change denialism!

  5. #5 Dano
    September 19, 2006

    I honestly don’t know whether the per comment at 4:13 PM is someone’s idea of satire or it’s real.

    Maybe that’s a clue for me.

    Best,

    D

  6. #6 Ian Gould
    September 20, 2006

    This change in WHO policy allows us to test the claim that restrictions on DDt use have resulted in millions of unnecessary deaths.

    Obviously, if the claims are true, malaria deaths should now decline steeply.

    If they don’t, the people spreading those claims should retract them.

    In practice, they’ll probably either say nothing or claim that DDT use is still too restricted.

  7. #7 per
    September 20, 2006

    dear joel

    I will put it in simple words. If DDT has been in use for 40+ years, why does tim have to rely on a paper so fresh that it is only available as an eprint yet ?

    Papers that are only freshly published have not yet been confirmed by other groups; and as we all know, replication is a hallmark of the scientific process.

    Why isn’t timmy showing us a whole series of papers which characterise a hypothesis of ddt’s action, and then replicate those findings to have unequivocal proof that ddt is a toxin to humans? There have been 40+ years to generate this paper, and there have been many papers looking at ddt.

    there is a reason…

    yours
    per

  8. #8 per
    September 20, 2006

    I honestly don’t know whether the per comment at 4:13 PM is someone’s idea of satire…

    hmm. let’s see, Dano has the option of making a substantive comment, or sneering. Which does he do ?

    no surprise, then. At least there is no “mendacisization”.

    per

  9. #9 Pinko Punko
    September 20, 2006

    This thread has all the makings of a classic.

  10. #10 Jeff Harvey
    September 20, 2006

    Joel,

    Well said: Per continually masquerades as a ‘master of all trades’ yet he hides behind a pseudonym and refuses to tell us his qualifications in the various fields he covers with superficial zeal. Yet he somehow seems to think his views – which are different from the vast majority of researchers working in the respective fields – are correct.

    So come clean Per: what have you done in the fields of climate science? Epidemeology? Any related fields? There’s reams of empirical studies showing that DDE is bioaccumulative towards the terminal end of the food chain, and its harmful effects on reproduction in avian predator are well documented. If there are effects of the pesticide in nature, why should Homo sapiens be exempt? Do we possess some inherent physiological adaptation that precludes effects?

    Let’s be honest here: corporate lobby groups like Africa Fighting Malaria are in fact working tirelessly to reduce government impdiments on the use of pesticides to increase profit margins for the amoral pesticide manufacturers they represent. By using ‘aggressive mimicry’, these groups convey a message of concern for society that veils their real agenda. Anti-environmental organisations use this strategy all the time, creating corporate lobby groups with environmentally friendly names e.g. The National Wetlands Coalition, Greening Earth Society, Abundant Wildlife Society etc. etc.

  11. #11 per
    September 20, 2006

    well, I have now been able to look at Tim’s link for ” possible health risks to humans”, and I can see why he uses such ambiguous language, e.g.

    …elevated levels of DDT in serum or body fat, but medical follow-up showed that this did not appear to have done them any harm.

    Technically, DDÉ is the harmful part…

    it is always useful to quote Dano, and the surprising thing about the AJE in press study is that there is precious litte effect with DDE- the supposedly most harmful part. How strange…
    and the statistical association that they do have only holds good for girls, not boys. So it is intriguing to see that the authors offer in support the following gem:

    13). A recent case report suggested that a mother’s exposure to DDT could be responsible for her son’s neurobehavioral dysfunction (12).

    a classic in the making.

    per

  12. #12 per
    September 20, 2006

    Jeff:

    Per continually masquerades as a ‘master of all trades’ yet he hides behind a pseudonym

    it is worse than that; I make no case that I have special expertise and that you should listen to me on that account. All I have is my arguments, which must stand up on their own two feet !

    Speaking of which, you made an ambiguous claim about “noises” I had made about your expertise. Are you going to give an example, or is this just an example of a claim that will never be substantiated ?

    yours, per

  13. #13 Robert
    September 20, 2006

    per wrote:

    well, I have now been able to look at Tim’s link

    Muffin top:

    You mean, you objected to the material **before** you had even read it? Whoa, dude, no one can possibly doubt your objectivity.

    it is worse than that; I make no case that I have special expertise and that you should listen to me on that account.

    Wait a second. In that other thread you were saying that Ball **does** have special expertise and that his critics should be dismissed because they hadn’t “standing”. Hmmm. Well, that doesn’t seem consistent, does it? Unless, of course, by “special expertise” you meant “trouble counting past the number eight.”

    All I have is my arguments, which must stand up on their own two feet !

    And how’s that working out for you? Cuz I’m thinkin’ that maybe you’d have better luck if, you know, you stopped cutting your own legs out from under you. Just sayin’, is all.

  14. #14 Jeff Harvey
    September 20, 2006

    Per,

    I don’t want to argue with you, but you make a lot of intimations: referring to my working in the field of multitrophic interactions is not meant to give me any kind of credit, but to suggest what I know about broader science is limited because of this (at least to the lay reader this must come across). That is your prerogative, although you probably gleaned information about me from our web site or by a Google search. If you want to discuss some of the research I am involved in, which covers everything from insect-plant co-evolution to top-down and bottom-up processes in communities to factors affecting the success of invasive species in broader communities, I would be more than happy. I also give quite a few lectures on nature and society, as well as on public policy and valuing nature in an economic framework.

    The ‘noises’ I refer to are based on a reply you made a few months back where you used a simple smear, typical of the anti-environmental crowd. The strategy you employed is simple: I make a statement and you reply with a witty and snide riposte, using my own words against me. I don’t recall the thread nor will I spend the next couple of hours looking for it, but in effect you just took something I said and then twisted it to suit your own ends.

    As for being an all-purpose generalist, and presenting arguments that ‘must stand on their own two feet’, I would like to ask how many scientific conferences you attend where these issues are debated and argued. This is important, because in these venues your arguments will be much more heavily scrutinized than they are here, as admittedly most of the contributors (including myself) are not experts in these fields. I readily debated Lomborg on biodiversity loss, because its an area I am well acquainted with in terms of professional background.

    Ultimately, I stand by my assertion that one’s pedigree should matter in scientific debates, because people educated and working in specific fields should posses a stronger working knowledge than people without the same qualifications. This is the essence of peer-review, and may partly explain why most climate sceptics publish few, if any, papers in rigid journals. They just don’t stand up to severe scientific scrutiny.

  15. #15 Tim Worstall
    September 20, 2006

    From the press release:

    “Environmental Defense, which launched the anti-DDT campaign in the 1960s, now endorses the indoor use of DDT for malaria control, as does the Sierra Club and the Endangered Wildlife Trust.”

    Does that mean (as it certainly could be read to mean) that one or more of those organisations did indeed oppose the indoor spraying of DDT to combat malaria?

  16. #16 Dano
    September 20, 2006

    Shorter per:

    …um…dangit, what’s the tag for ‘hand-wave’?!?

    Best,

    D

  17. #17 Hank Roberts
    September 20, 2006

    ” …. requirements include …., access to the interior of all houses, and a relatively stable human population …. The US appears willing to put in a substantial amount of extra money, and the US wants to push ….”

    Our new monitoring program provides for access to interior of all houses, a relatively stable human population, and comprehensive and regular monitoring. This allows placement of devices that will provide a continuous detection network that will immediately allow targeting a massive response immediately upon the slightest hint of activity by any terrorist, er, mosquitoes ….

  18. #18 J Hamilton
    September 20, 2006

    There is a very small probability that a reader could be mislead by an earlier poster regarding the toxicity of DDT. For those interested, review the pesticide information profile on DDT at the Pesticide Management Education Program at Cornell University. The URL is: http://pmep.cce.cornell.edu/profiles/extoxnet/carbaryl-dicrotophos/ddt-ext.html

  19. #19 jre
    September 21, 2006

    Why isn’t timmy showing us a whole series of papers which characterise a hypothesis of ddt’s action, and then replicate those findings to have unequivocal proof that ddt is a toxin to humans?

    And J. Hamilton links to a richly factual document detailing over 27 years’ research into DDT’s toxicity to humans and animals. If per is not simply a clown and / or a troll, I’d assume he will either pronounce himself satisfied on this point, or come back with a similarly fact-based response. Per?

  20. #20 z
    September 22, 2006

    “Indoor spraying is like providing a huge mosquito net over an entire household for around-the-clock protection,” said U.S. Senator Tom Coburn, a leading advocate for global malaria control efforts.

    Coincidentally, much the same way the Star Wars Missile Defense System is like providing a huge mosquito net over an entire country for around-the-clock protection.

  21. #21 z
    September 22, 2006

    “If DDT has been in use for 40+ years, why does tim have to rely on a paper so fresh that it is only available as an eprint yet ?”

    If DDT has been in use for 40+ years, why does anyone believe in a DDT ban?

  22. #22 JB
    September 24, 2006

    “All I have is my arguments [and sock puppets], which must stand up on their own two [3? 4? 5?] feet !” — per

  23. #23 per
    September 24, 2006

    And J. Hamilton links to a richly factual document detailing over 27 years’ research into DDT’s toxicity to humans and animals. If per … come back with a similarly fact-based response. Per?

    it seems obvious that neither of you has read this derivative document. The principle source of human data is the ATSDR report- and are you seriously relying on that as evidence of harm in humans ?

    workers in a factory ate ~~1 gramme of DDT, and one out of eleven got a fast heart rate ?

    I have made a specific claim, and pointed out that the references tim gives do not provide proof of health effects on human at normal levels of exposure.

    strangely enough, when it comes to science, no-one wants to engage.

    yours

    per

  24. #24 per
    September 24, 2006

    The strategy you employed is simple: I make a statement and you reply with a witty and snide riposte, using my own words against me.

    dear jeff,

    i am very sorry you lost an argument. I understand that you now want to call me names, rather than try and argue a specific point.

    I stand by my assertion that one’s pedigree should matter in scientific debates,…

    good, because I am looking forward to you accepting that your views have absolutely no value outside the microscopic areas of the papers that you have published, and not saying anything which has not been peer-reviewed.

    I do not accept your view that I simply have to tug my forelock to any self-proclaimed scientific infallibility.

    most climate sceptics publish few, if any, papers in rigid journals. They just don’t stand up to severe scientific scrutiny.

    your faith in scientific journals is touching, if not naive. You might ask JPA Ioannidis for a comment.

    I look forward to your uncritical acceptance of Steve McIntyre’s published work, and your future castigation of MBH 98/99; after all, his papers have been published in the peer-reviewed literature, and they must be right.

    yours

    per

  25. #25 Tim Lambert
    September 24, 2006

    per, I don’t think that Jeff’s point was that complicated, but you missed it entirely.

  26. #26 J Hamilton
    September 24, 2006

    An all knowing poster writes:

    “just imagine if DDT actually were toxic…”

    which then becomes

    “ddt is a toxin to humans?”

    which becomes

    “tim gives do not provide proof of health effects on human at normal levels of exposure”

    The ground just keeps shifting. I suggest that the poster contact Cornell University, Michigan State University and the University of California and demand a full retraction of the materials on the toxicity of DDT that they have made available online. When successful please report back. I won’t hold my breath.

  27. #27 per
    September 24, 2006

    I don’t think that Jeff’s point was that complicated, but you missed it entirely.

    Tim, it is very difficult to know what point you are referring to.

    Is it the idea that when I say that I have not made adverse comment about his scientific track record, he then complains that I haven’t provided enough adulation for all other aspects of his thinking, and therefore this statement must be an implied insult ?

    Is it the idea that someone’s “pedigree” requires me to bow down in obeisance to whatever they say, especially if they cannot manage to communicate these fantastic ideas, or muster a logical argument ?

    I didn’t realise that these needed refutation, as they seem to be pretty much self-refuting to me. However, if there is a coherent idea in there that I have missed, please do bring it to my attention :-)

    yours

    per

  28. #28 per
    September 24, 2006

    The ground just keeps shifting

    tim’s original claim was “possible health risks to humans” of DDT in the context of normal anti-malarial use. The ground has not shifted.

    I suggest that the poster …demand a full retraction of the materials on the toxicity of DDT…

    I don’t think you have read this review. However, feel free to point out the paper that shows this toxicity.

    per

  29. #29 jre
    September 24, 2006

    it seems obvious that neither of you has read this derivative document. The principle [sic] source of human data is the ATSDR report- and are you seriously relying on that as evidence of harm in humans ?

    What is your point, per? Are you saying that the ATSDR report is not scientifically reliable, or that it is not relevant to human health? To review the bidding, your opening comment was

    hmmm… 40+ years of DDT use, including real heavy use before the ’80′s, and the best evidence that Timmy can come up with is a dead link, a news report on the bbc- which acknowledges the contradictory nature of its findings, and one report from September 2006, which isn’t formally published in print yet.

    just imagine if DDT actually were toxic…

    The answer to that first comment is clear: DDT is toxic to humans, although at dosage levels much higher than for birds and fish:

    People who swallowed large amounts of DDT became excitable and had tremors and seizures. They also experienced sweating, headache, nausea, vomiting, and dizziness. These effects on the nervous system went away once exposure stopped. The same type of effects would be expected by breathing DDT particles in the air or by contact of the skin with high amounts of DDT. Tests in laboratory animals confirm the effect of DDT on the nervous system.

    Faced with evidence that DDT does have acute clinical effects on humans at high dosages, you have moved the goalposts:

    the references tim gives do not provide proof of health effects on human at normal levels of exposure.

    Ah, now it’s proof of health effects at normal levels of exposure you’re after, is it? You’ve moved toward safer ground,
    but you are not yet in the clear. In the US, lower birthweight and incidence of pre-term infants has been found to be associated with blood levels of 10 ppb (high for the US, but not for areas where DDT is still in use). Retired malaria control workers in Costa Rica showed mild neurological impairment compared to a control group. In the Uruguayan work force, occupational exposure to DDT was found to be associated with increased risk of lung cancer. Long-term studies of DDT’s toxic effects in humans are hard to come by — precisely because its use has been so heavily regulated in industrialized countries — but they do exist. Animal studies are abundant, and they reinforce the conclusions of the human studies. Broadly, what the research community has concluded is this:

    DDT’s toxicity to humans is low, but not zero, at expected exposure levels. Its toxicity to other, desirable species is much higher. Accordingly, the wisest course would seem to be a balancing of risk and a search for the least destructive strategy for use of DDT and other chemicals in malaria control.

    Just to make the point excruciatingly clear, per, your statement that no studies exist showing human toxic effects of DDT at normal exposure levels was wrong. Care to move the goalposts again?

  30. #30 per
    September 24, 2006

    Dear jre

    my congratulations on attempting to address the science.

    I am quite happy to rely on the atsdr report. I am also delighted to see that you realise that all chemicals can cause toxic effects, if given at high enough dose. Humans who have eaten > 5 gramme quantities have indeed suffered severe effects.

    As you rightly point out, this is many orders of magnitude more than normal human exposure. The ATSDR report you quote says:

    There is no evidence that exposure to DDT at levels found in the environment causes birth defects in people.

    that contrasts with the unreferenced studies you provide.

    DDT’s toxicity to humans is low, but not zero, at expected exposure levels.

    The research community ? Sorry, but I don’t recall when god gave you special licence to speak for the research community, nor is this reflected in the reference material you cite. I believe that this assertion is a complete invention on your part.

    Long-term studies of DDT’s toxic effects in humans are hard to come by

    yes, there were studies of workers who were exposed to outrageously high doses for decades; so why don’t you report the findings ? From the ATSDR, for example:

    In a follow-up study to Morgan and Lin (1978) (see Section 3.2.2.2), Morgan et al. (1980) analyzed
    morbidity and mortality in an extensive cohort of male and female workers exposed (formulators, applicators, farmers) to organochlorine pesticides. The follow-up included 73% of an original cohort of 2,600 workers. The median duration of work in a pesticide-related occupation was 13 years. Disease
    incidence rates were studied in relation to job exposure categories and to serum levels of organochlorine pesticides measured in the original study. There were no significant differences in mortality patterns between pesticide-exposed workers and controls except for an excess of deaths by accidental trauma in workers engaged in structural pesticide application.

    your statement that no studies exist showing human toxic effects of DDT at normal exposure levels was wrong

    no, it is not, and you have not provided any evidence to contradict me. A half-baked statistical association cannot show causality, and is no basis for wilful disregard for studies of human exposed at much higher dose that show no adverse effects.

    yours

    per

  31. #31 jre
    September 25, 2006

    Oh, for crying out loud, per.

    As noted, long-term studies showing toxic effects of DDT in humans at normal exposure levels do exist, and are cited in the ATSDR.
    As you know well, the ATSDR report contains the cites, and I have summarized their results fairly. That you refuse to accept them is no fault of mine.

    I’ll also stand by my statement that researchers familiar with DDT’s effects believe that its use should take into account its probable toxic effects on humans and animals.

    Your insistence that DDT has no toxic effects on humans is at odds with the facts. Face it.

  32. #32 jre
    September 25, 2006

    Here’s a good recent review article:

    Although DDT is generally not toxic to human beings and was banned mainly for ecological reasons, subsequent research has shown that exposure to DDT at amounts that would be needed in malaria control might cause preterm birth and early weaning, abrogating the benefit of reducing infant mortality from malaria. Historically, DDT has had mixed success in Africa; only the countries that are able to find and devote substantial resources towards malaria control have made major advances. DDT might be useful in controlling malaria, but the evidence of its adverse effects on human health needs appropriate research on whether it achieves a favourable balance of risk versus benefit.

    See anything in there dramatically in conflict with my summary of the scientific consensus?

  33. #33 Tim Lambert
    September 25, 2006

    per, by the way, is a [Reader in Molecular Toxicology University of Nottingham](http://dmg.nott.ac.uk/groupfiles/david.htm), so I think he knows that his comments are rubbish and he’s just funning with us.

  34. #34 per
    September 25, 2006

    long-term studies showing toxic effects of DDT in humans at normal exposure levels do exist

    if there were such, you didn’t cite them. You may be confusing the term “association” with “causation”. You may be ignoring the results from large epi studies of workers in factories, who were exposed to DDT at levels thousands of times higher than normal use; all this exposure, and nothing much significant turns up from these studies.

    per, your statement that no studies exist showing human toxic effects of DDT at normal exposure levels…

    Your insistence that DDT has no toxic effects on humans is at odds with the facts

    you cannot even get your position consistent; you wouldn’t be trying to set up a straw man, would you ?

    See anything in there dramatically in conflict with my summary of the scientific consensus?

    DDT is generally not toxic to human beings

    DDT …might cause preterm…

    you seem to be unfamiliar with the distinction between a statement of fact, and speculation. After your previous comment, it is of course amusing that you choose to quote a reference that says that ddt is generally not toxic to human beings.

    yours,
    per

  35. #35 jre
    September 25, 2006

    Per, each and every one of your comments has been directed to asserting that DDT is not toxic to humans, and you know it.
    After being repeatedly directed to studies showing the contrary, you continue to quibble about irrelevancies, shift your position and complain about being misrepresented. It ain’t working. The position you object to — that the evidence for DDT’s toxic effects warrants some risk balancing — is extremely well supported by the literature, as noted by the Lancet’s review article.

    But you’re a persistent troll — I’ll give you that.

  36. #36 per
    September 25, 2006

    each and every one of your comments has been directed to…

    now you know the direction of my thinking ! Not able to take exception to the words I use, you are now castigating me for the direction of my thoughts !

    the evidence for DDT’s toxic effects warrants some risk balancing — is extremely well supported by the literature, as noted by the Lancet’s review article

    really ? Well, here are some quotes from that article in the Lancet.

    “In people, DDT use is generally safe; large populations have been exposed to the compound for 60 years with little acute toxicity apart from a few reports of poisoning.12 Doses as high as 285 mg/kg taken accidentally did not cause death, but such large doses did lead to prompt vomiting. One dose of 10 mg/kg can result in illness in some people.12 ”

    “Although extensively studied, there is no convincing evidence that DDT or its metabolite DDE increase human cancer risk. ”

    “Various reproductive and hormonal endpoints have been examined in both men and women, and although associations have been recorded, causal links have not been confirmed.”

    Sorry, but I am struggling to see anything here that is relevant to demonstration of toxicity at normal levels of use; in fact, the reference you cite specifically says that there is no demonstration that ddt causes toxicity at normal levels of use.

    you continue to quibble about irrelevancies

    i am amused that you quote text that disagrees with your position. Perhaps you may yet discover the difference between a statement of fact, and speculation; but then again, pigs might fly !

    yours

    per

  37. #37 Dano
    September 25, 2006

    Now, now folks: you know per has his marching orders ** – “quick, David! We need obfuscation and mendacity! Do your thing!”

    Best,

    D

    ** I know not from whence they come: Industry-funded sources, the media, David’s boss, Mars…

  38. #38 per
    September 25, 2006

    Dano said:

    DDÉ is the harmful part …

    We need obfuscation and mendacity

    you could have attempted to justify your words; instead you resort to thinly-veiled accusations of lying on no basis whatsoever.

    yours, per

  39. #39 jre
    September 29, 2006

    Dano is less willing to tolerate fools than most; it spares him a lot of time and trouble.

    Per — you have missed this point, as you have every other in this thread. When a survey of the existing literature reports that DDT exposure might cause adverse health effects sufficient to wipe out any advantage it confers in reducing infant mortality from malaria, it is reasonable to say that some toxicity exists at normal levels. Yes; DDT’s toxicity to humans (as contrasted to its toxicity to birds and fish) is low. You could have said that at the outset, instead of staking out an untenable position. Instead, the conversation has been this exasperating exercise of chasing you from one position to another:

    just imagine if DDT actually were toxic…

    Sure it’s toxic — look at the reports.

    No, I mean at normal levels of exposure.

    Some effects have been observed at normal levels, warranting some caution.

    What — you cite the ATSDR? Don’t make me laugh.

    There are others. Take a look at the Lancet’s review article.

    The Lancet? It supports my case! Look — no cancer!

    At some point, the discussion becomes fruitless. Just for the record — toxic effects of DDT in humans have been observed in levels of exposure to be expected among malaria control workers and the general population where it has been used for vector control. See the ATSDR, see the Lancet.

    Note: Per seems to disagree.

    Note also: Some feel that Per is more interested in scoring a political point than examining the evidence.

  40. #40 per
    September 30, 2006

    it is reasonable to say that some toxicity exists at normal levels.

    no, it is not. If it was, you would have produced a reference that supported that position. Instead, you ignore the explicit cites I give you from your own review articles that point out that DDT has no confirmed human toxicity at normal levels of exposure.

    Some effects have been observed at normal levels…

    utter nonsense; you haven’t cited a paper showing an effect. The lancet review you cite explicitly states “causal links have not been confirmed”. Let me suggest you try reading the material you cite.

    toxic effects of DDT in humans have been observed in levels of exposure to be expected among malaria control workers and the general population where it has been used for vector control. See the ATSDR, see the Lancet.

    i have quoted directly from the atsdr, and the lancet paper, in my posts of September 24, 2006 11:37, and September 25, 2006 04:38. These direct quotes contradict your unfounded assertions. In fact, the atsdr is pointing out that there was no toxicity seen when people worked at a DDT factory, when they were exposed to DDT at levels thousands of fold higher than you would be exposed under normal use.

    I see you have taken to using non-existent quotes. Let me quote directly from the lancet review you cited:

    “In people, DDT use is generally safe…”

    yours

    per

  41. #41 John Cross
    September 30, 2006

    Per: like you do in regards to climate change issues, let me offer profound statements while knowing nothing about the issue. I have not read the papers in question and probably won’t, but of course that is not really a problem. I can just quote you.

    DDT has no confirmed human toxicity at normal levels of exposure

    OK, I can buy this, but then you say

    In people, DDT use is generally safe…

    So which is it – no toxicity or generally safe.

    Toodles
    John

  42. #42 per
    October 1, 2006

    Dear John

    if you accept the ATSDR and Lancet’s various statements that there is no confirmed human toxicity at normal levels of exposure (and even for factory workers), then that would probably lead you to believe that DDT is generally safe.

    The safe quote is a direct cite from the Lancet piece. I don’t see why it is controversial.

    yours

    per

  43. #43 per
    October 1, 2006

    Tim

    I think he knows that his comments are rubbish…

    well, tim, in point of fact, you are utterly wrong.

    i also note that you have not even attempted to argue that any of these “possible health risks” even exist; doubtless because you are already fully aware how abysmal is the evidence.

    yours

    per

  44. #44 John Cross
    October 1, 2006

    Dear Per:

    would probably lead you to believe that DDT is generally safe.

    Oh, so now you have gone from not toxic to probably, generally safe? OK, that sounds very definitive. But just for clarification, would you consider Russian roulette to be probably, generally safe?

    toodles
    John

  45. #45 per
    October 1, 2006

    Dear John

    if you cannot understand simple english, i see no point in prolonging the agony.

    You might choose to consider that the quote, “In people, DDT use is generally safe…” came directly from the Lancet paper; the one which jre used as evidence that ddt was dangerous.

    or alternatively, you can use the info at tim’s deltoid post: “elevated levels of DDT in serum or body fat, but medical follow-up showed that this did not appear to have done them any harm.”

    keep on trolling. If you say anything substantive, i will let you know !

    per

  46. #46 frankis
    October 1, 2006

    Isn’t it clear that per is simply right about the meaning of the quotes and isn’t his broader point, that there must be far more important things to agitate about than DDT’s toxicity to humans, also correct? It’s the unwanted effects of pesticides on other species and on ecosystems, and also perhaps the possibility of human harm from accident or misuse of them, that accounts for the strict regulations governing pesticide use.

    I don’t see any virtue in denying the obvious and I think the meaning of those papers cited above is as plain as anyone should reasonably expect it could have been made; per’s right.

  47. #47 John Cross
    October 1, 2006

    Dear Per:

    When have you ever worried about saying anything substantive? But here is your chance to show me wrong – my offer to bet with you regarding Dr. Ball’s victory in his suit is still open. So are you going to say anything substantive about it?

    Toodles
    John

  48. #48 Eli Rabett
    October 1, 2006

    The problem with the term generally safe when refering to toxicity, is that sensitivity varies tremedously amoung humans, and can depend on prior exposure, prior exposure to other toxins and many other things.

    Thus, DDT could be perfectly safe for 99,999 people out of 100,000, but in a population of one billion that is 10,000 lives down the drain.

  49. #49 J F Beck
    October 2, 2006

    Eli Rabett wrote: “Thus, DDT could be perfectly safe for 99,999 people out of 100,000, but in a population of one billion that is 10,000 lives down the drain.”

    This ignores the DDT deaths reality: “DDT has a wide margin of safety when used judiciously, and few if any adequately documented cases of DDT poisoning in man have been fatal. It appears that the main toxicity to humans is related more to the solvent vehicle rather than the DDT itself.”

  50. #50 Pinko Punko
    October 2, 2006

    per probably is right about DDT toxicity in humans, but the bigger picture is what is the dealio? I invite per to express his entire philosophy regarding DDT so we may move on from trees and assess the health of the forest.

  51. #51 Eli Rabett
    October 2, 2006

    Well, while in principle JF Beck might be right, nothing is always used judiciously and health reporting is not what you might hope. I’ll stick with my point.

  52. #52 per
    October 2, 2006

    Thus, DDT could be perfectly safe for 99,999 people out of 100,000, but in a population of one billion that is 10,000 lives down the drain.

    in fact, the cited references give one case report of ddt induced fatality; a baby that drank an ounce of kerosene/DDT mix. It is entirely possible that the baby died as a result of the kerosene.

    After sixty years of widespread DDT use, including direct application of DDT to humans, there isn’t a single reliable report of DDT killing a human. Your “10,000 lives down the drain” is a bizarre fantasy.

    It is noteworthy than many other insecticides, such as pyrethroids, are responsible for human fatalities. That is because they are much more toxic than DDT.
    http://www.intox.org/databank/documents/chemical/deltamet/ukpid62.htm

    yours
    per

  53. #53 J Hamilton
    October 2, 2006

    Given the complete and utter lack of DDT toxicity the previous poster should volunteer for the obvious experiment. Report back when successful.