Rachel Carson, DDT and Another Urban Myth

Another Cafe Scientifique meeting, another urban myth. Strange, since the level of discourse at these talks is very good. The audience is made up of engineers, doctors, technicians, IT techies of various persuasions and other “skeptical” types in the best sense of the word, all of a certain age. Being Henley-on-Thames, that age is at the upper end, but none the worse for that; having been around the block a few times gives you a certain perspective on the issues of the day, especially if you have a questioning mind.

The talk itself was excellent, delivered by Dr. David Hughes from Syngenta and titled “Organic Food and Farming : Global Saviour or a Case of the Emperor’s New Clothes”. His thesis deserves a blog post of itself, but for today I will take a minor detour and respond in detail to a statement from one of the audience. And the proposition in question? The banning of DDT, championed by Rachel Carson in “Silent Spring”, has killed 5 to 6 million people through allowing the spread of malaria.

A few questions later I had the chance to stand up and refute the claim. But replying on the fly to an off-topic issue requires an ability to recall sources that I don’t have. But I did remember that Oreskes and Conway in their superb book “Merchants of Doubt” had debunked this meme based on the fact that resistance to DTT led to the decline in its use not—not an eco-campaign by Carson and her followers. And then Hughes countered that DTT was still being used today. Well, yes. Alas I was not fast enough to point out the contradiction: the ban of DDT had led to millions of death, but it wasn’t actually banned?

Actually, I doubt whether Hughes at the time had a well-formed view of Rachel Carson and DTT at all. But the questioner had fashioned Carson as anti-science. A case of the enemy of my enemy is my friend. But sometimes this just isn’t true.

Back at home, I re-read Oreskes and Conway’s Chapter 7 entitled “Denial Rides Again: The Revisionist Attack on Rachel Carson”. Here we learn that President Kennedy turned to the President’s Science Advisory Committee (PSAC) to guide him on DDT in 1962. The PSAC’s advise was to restrain the use of DDT. Ten years on it was under a Republican president, Richard Nixon, that DDT was actually banned in the U.S.

But Oreskes and Conway’s critical point is this:

…. the most important reason that eradication was that mosquitos were developing resistance. In the United States, DDT use peaked in 1959—thirteen years before the ban—because it was already starting to fail.

And this pattern was repeated abroad. Between 1948 and 1963, the application of DTT worked like a charm in Sri Lanka. However, malarial cases then ticked up again and by 1968 DDT was becoming ineffective. Nonetheless, the country’s health authorities persevered, but no improvement was seen even with larger applications. Eventually they gave up. But this was years after the United States ban, and not because of the U.S. lead: they gave up because DDT stopped working.

Nonetheless, a number of right-wing foundations such as the Competitive Enterprise Institute and the Heartland Institute have continued with shrill claims that the EPA’s banning of DDT has killed millions of Africans, Asians and Latin Americans, and Rachel Carson has blood on her hands. It just isn’t true.

12 responses to “Rachel Carson, DDT and Another Urban Myth

  1. Thanks for another interesting post Justin. I’d be interested to know what proportion of the audience were knowledgeable about biological systems, rather than non-biological (IT, engineering etc). From my personal experience I am not surprised that some in the audience may seem unbalanced/uneducated, even for such an educated group! As a physicist, engineer myself, who (as is common in the UK) specialised early in my education, I had very little appreciation for the complexity (and wonder) of life – biologically, socially and philosophically speaking. It coloured my ability to rationally analyse such complex topics in a balanced way. I then pursued training in business administration and worked in business and engineering for over 20 years….which sealed my typical western fate to view things from a predominantly competitive or slightly gun-ho perspective coupled with an assumption that ‘technology is wonderful and can save us from all our woes’.
    Luckily, as a mother of 2 young children, I crawled out from under my rock a few years ago and realised I needed to get a more balanced education. On that journey I read Rachel Carson’s book, I read about her critics and the current policies and law on DDT use, got some training from a biotoxicologist about biotoxicity, bioaccumulation, endocrine disruption etc etc. I’m still not an expert obviously, but feel a lot more able to comment on the topic. Whilst Ms Carson may not have been perfect with all her suggestions (who is, especially when a forerunner in the field) she stuck her neck out and had some very insightful conclusions:
    (a) DDT, as just one pesticide example, does harm a wide range of wildlife even when applied according to dosage instructions (see http://npic.orst.edu/factsheets/ddtgen.pdf for confirmation of that), with the potential to cause a collapse of biodiversity and ecosystems. This is not just a problem for the wildlife itself, it is a problem for life as we know it – the role of biodiversity in maintaining our planet is rather overshadowed by the climate change/carbon debate unfortunately.
    (b) if applied without strictly following the application instructions (for example through excessive blanket spraying) it can be toxic to humans too. And it was/is not uncommon for those applying insecticides to make mistakes or be sloppy in their application.
    (c) DDT is persistent in the environment (150yrs in water!), so frequent repeat applications can create excessive dosage and exacerbate effects from long term exposure. It also bioaccumulates as you go through the food web, those of us at the ‘top’ of the food web get the strongest concentrations. Oops.
    (d) as with any pesticide, the long term effectiveness will depend on the target’s ability to adapt and how the pesticide is used/misused. DDT has been observed to have a limited duration of usefulness, as you highlight.

    The banning of DDT was originally against agricultural use in many developed nations, starting in the late 1960s (UK only banned it in 1984!). Maybe these were due to the observed long term ineffectiveness of DDT, rather than any fear of toxicity. But the worldwide ban came into force with the Stockholm Convention on Persistent Organic Pollutants (POPs) in 2004. It’s aim was to address the problem of POPs in general – chemical substances that persist in the environment, bio-accumulate through the food web, and pose a risk of causing adverse effects to human health and the environment, i.e. the eco-warrior angle finally or just good old common sense?! Likewise that ban was/is ONLY for agricultural use. There is always a ‘cost’:’benefit’ trade-off to be made with these laws. Whilst they may not be made totally without the influence of vested interests it seems that this one has been heralded as a good compromise. Therefore DDT is still allowed for vector control and is used therefore in a more targeted way through WHO programmes in Africa, Asia etc. In the developed nations like the US it can also be used for public health emergencies. So as you suggest, I agree that the questioner was talking rubbish and it’s a myth that is conveniently propagated. However I was surprised that even James Lovelock (who I greatly admire for his persistence in raising the profile of climate change and for being largely ‘independent’) used this mantra of a DDT ban killing millions in his book ‘The Vanishing Face of Gaia’.
    Even considering that DDT can be used for malaria vector control, technology is still not a magic quick fix, I doubt it ever will be. The whole approach includes insecticide use in conjunction with biological methods (e.g. fish to eat the larvae), habitat control (e.g. remove stagnant water) and reducing contact.
    As for the original topic of the talk at the Café Scientifique, I’d love to hear about it! I admit that at face value I can’t believe that an employee of Syngenta (which sells seeds and pesticides) can give an unbiased view on the topic of organic farming! I’m trying to keep an open mind….

    • Julia. Thanks for this: it is a really useful amplification. I could have done with you in the audience last night! There were certainly medical doctors in the audience, but I sense no specialists in the field of toxicity.

      To be fair, David Hughes from Syngenta didn’t himself actively support the questioner’s claim that the banning of DDT had killed millions due to malaria. But then again, he didn’t knock it down (although I am sure he has the same background knowledge as you, and thus could have clarified the link between the banning of DDT and malaria-related deaths). He did, however, point out DDT problem of persistence in the environment and also the fact that it tends to be stored in fatty tissues within the body, so promoting its accumulation.

      I think he was more guilty of a sin of omission. A major point he was trying to get across was that, at best, the organic movement can be disingenuous with its claims and, at worst, it can be blatantly anti-science. The questioner’s statement on DDT and malarial deaths gave credence to the idea that the broader environmental movement, encompassing organic farming, is alarmist and anti-science. Hughes’ sin of omission was to let this statement hang in the air un-challenged.

      I find this highly irritating since the “blood on her hands” characterisation of Rachel Carson pops up all over the place, especially in the writings of climate “skeptics” and other critics of sustainability. It is in Bjorn Lomborg’s “The Skeptical Environmentalist”, the bible of eco-critics. And listen to this in Matt Ridley’s “The Rational Optimist” (beloved of the usually sensible The Economist Magazine and all climate “skeptics”):

      “DDT’s miraculous ability to halt epidemics of malaria and typhus, saving perhaps 500 million lives in the 1950s and 1960s (according to the US National Academy of Sciences), far out-weighed any negative effect it had on human health. Ceasing to use DDT caused a resurgence of malaria in Sr Lanka, Madagascar and many other countries.”

      For Sri Lanka, this is blatantly wrong, As Oreskes and Conway point out, DDT worked like a dream in Sri Lanka up until 1963, but then resistance started to build up and by 1968 malaria was a major problem again. Nonetheless, Sri Lanka kept on using DDT through the 1970s but its efficacy due to resistance continued to decline as highlighted by the WHO in 1976 (when it was deemed completely ineffective). As a result, the Sri Lankan health authorities switched to malathion. Ridley’s claim that a DDT ban in Sri Lanka took countless lives is a complete lie. But this meme now appears to be out there with a life of its own.

      At for Hughes’ main points regarding organic food, I am awaiting a paper from him and his slides, then I will write it up.

      • Thanks Justin, I fear that it is easier to write a rational and hopefully well argued response to such blatantly (in our view at least ;oP) biased statements after the fact. Not sure I would have been any better at dredging out all the facts from my brain, if posed with such a question in such a situation unfortunately.

        Anyway, I share your frustration, and as we’ve said before just have to keep plugging away at it. One mind at a time is better than none.

        Looking forward to the organic food write up. Without wishing to pre-empt that, it’s easy to brandish all ‘environmentalists’ with the deception/anti-science mantel. I’d like to think that there are very many rational scientists out there who can weigh up the pros and cons of both approaches, although I’d think that those into organic farming (including those that could be classified as scientists) would tend to fall on the side of ‘if in doubt use the precautionary principle’, which could be perceived as being anti-innovation/anti-real-science – another load of rubbish, that gets me annoyed.

      • Still haven’t got his slides yet, but have the article he authored. We have also been having a feisty exchange over how many people were killed by environmentalists due to the ban on DDT. I am trying to get hold of a decent time series of malaria deaths for India and South Africa. There are bits and pieces scattered around that I have found. Do you know anyone at the UN library who could help? In particular, I need deaths in South Africa from the early 1990s to date. DDT was banned for 3 years before being reinstated and there was an uptick in deaths but this coincided with drug resistance, two extreme flooding episodes and an explosion of AIDS. I think the uptick was a few hundred but don’t have the exact figures. And given that the DDT ban was one of only four factors behind the rise in deaths, it seems absurd to me that that the ban could be blamed for a huge number of deaths. Any help finding the numbers for South Africa, and for India, would be helpful. I will end up writing a post about this as well, because the refrain that environmentalists killed millions due to DDT bans is everywhere – and against my original assumption, David Hughes of Syngenta seems to believe this as well. This is rather disappointing, as I thought he wasn’t that ideologically driven when I heard his talk. But given that there is a direct and documented link between libertarian right wing think tanks in the US and the Rachel Carson killed millions meme, every time someone repeats it I am immediately suspect of everything else they write.

  2. p.s. your spell checker has been merrily substituting DTT for DDT!

  3. There are few major, and insurmountable flaws in the claim that “the DDT ban caused millions to die from malaria.”

    First, malaria has been significantly decreased, and the decline in malaria infections and death continues. At peak DDT use, in 1959-1960, half a billion people got malaria each year, and 4 million died. In 2012, WHO’s estimates are 250 million infections, and fewer than 800,000 dead. Most of the decrease comes without DDT. See links to WHO reports here: http://timpanogos.wordpress.com/2013/01/04/world-malaria-report-2012-malaria-still-declining-but-more-resources-needed-fast/

    Second, the “ban” on DDT in the U.S. applies ONLY to the U.S. — and in fact, EPA wrote the ban to allow DDT manufacturers to export DDT so they wouldn’t lose money. The U.S ban on DDT use on crops multiplied the amount of DDT available to fight malaria in Africa and Asia. If DDT were a panacea, that should have been a huge boon to malaria fighters. It wasn’t.

    Third, the calendar made that cause-effect impossible. WHO discovered DDT overuse had bred DDT-resistant and DDT-immune mosquitoes in Africa by 1965, and suspended its ambitious program to eradicate malaria because that made the program impossible. The U.S. didn’t ban DDT on crops until 1972, seven years later. EPA does not have a time machine.

    Fourth, mosquitoes move very little in a lifetime, perhaps an average of 50 yards. So stopping spraying in the U.S. doesn’t increase mosquitoes in Africa — the insects do not migrate far, and certainly not thousands of miles (except for a few cases of accidental transport).

    Incidentally, if you want the text of the 1963 report of the President’s Science Advisory Council, the full text is here: http://timpanogos.wordpress.com/2012/12/10/use-of-pesticides-report-of-the-presidents-science-advisory-committee-may-15-1963/

  4. Ed. Thanks very much for this. I agree with all these points and will look at the links. I am actually working on a follow-up post to this “environmentalists killed millions” claim. The more I have dug into it, the more it stinks!

    Incidentally, there is a superb literature review on the causes of Malaria resurgence by Cohen et al. in the Malaria Journal. Very useful ammunition if you (like me) get incredibly annoyed by the Rachel Carson killed millions myth.


  5. Oh, yeah: Quiggin’s book, Zombie Economics, has some discussion of the DDT-ban-as-killer meme: http://www.blackincbooks.com/books/zombie-economics

    • I had Zombie Economics on my shelf but had not got around to reading it. Seeing your post, I picked it up and ended up reading it in one sitting. It is superb (even if it doesn’t touch on topics like slowing growth, climate change and resource constraints, which preoccupy me most). Thanks for the prod to get around to reading it.

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