In part 1 of this fact check I examined Brian Dunning’s assertions that DDT did not thin eggshells. Responses from Orac: “Dunning should know better”, Bug Girl: “Dunning clearly got his information second-hand. And it was bad information.”, and Dunning:
which is a rather odd thing to say, because in comments on his podcast Dunning responded to this comment:
Yeah, the very fact that you would consider Junk Science a source worthy of citing frankly is enough to treat the entire article with extreme skepticism. Junk Science is nothing more than an anti-science ideologically driven libertarian/industry front group.
with this, where he says that junkscience was one of his sources:
I’m not sure your political disagreement with one of my sources constitutes a valid correction to anything in the episode.
Dunning has so far made two small corrections to his podcast. Many more are needed.
On to part 2 of the fact check. Dunning:
Silent Spring’s legacy may have been good for the birds, but not so much for human populations in the third world. DDT is one of the most effective pesticides ever discovered for fighting malaria. Although DDT remains legal for insecticide use in most areas where malaria is a major killer, the money for fighting the mosquitos often comes from donors in wealthy countries like the United States. Such wealthy donors have often had little personal exposure to the issues, and can sometimes have a skewed perspective when it comes to bald eagle eggshells in the United States versus the deaths of children in Mozambique.
This is ridiculous. No donor thinks that DDT use in Mozambique will harm bald eagles in the US. Some donors have insisted that their money funds insecticides other than DDT, but that’s not because of concerns about birds — it’s because of concerns that DDT is harmful to human health.
Writing in the Nature Medicine journal, malaria advocate Prof. Amir Attaran criticized American environmental groups for opposing the public health exceptions of DDT bans:
“Environmentalists in rich, developed countries gain nothing from DDT, and thus small risks felt at home loom larger than health benefits for the poor tropics. More than 200 environmental groups, including Greenpeace, Physicians for Social Responsibility and the World Wildlife Fund, actively condemn DDT.”
Dunning has truncated the quote from Attaran. The sentence doesn’t end there, but continues.
actively condemn DDT for being “a current source of significant injury to…humans.”
The full quote makes it clear the environmentalists were concerned about the danger to human health, not birds. And if you check the document that Attaran cites, you will see that Attaran hasn’t represented it fairly. They do want to phase out the use of Persistent Organic Pollutants (POPs) (including DDT), but only when “alternatives are made available” and
Special efforts must be made to ensure that health and safety are not compromised while a POP is being phased out and eliminated (particularly in the area of infectious disease control, …
Environmentalist groups do not oppose the public health exception for DDT. For example, Greenpeace says:
We support the continued use of DDT in malaria control programmes where there are no effective alternatives.
As a result of these pressures, many donations now coming from wealthy nations are now contingent upon DDT not being used, which leaves the poor nations with fewer options, often too expensive and less effective, and children die.
Let’s check the biggest one, USAID:
USAID supports indoor residual spraying (IRS) with DDT as an effective malaria prevention strategy in tropical Africa in those specific situations where it is judged to be the best insecticide for IRS both epidemiologically and entomologically and based on host-country policy.
And if you check USAID’s plans for 2010 you’ll see that they are planning to spray DDT in Ethiopia, Mozambique, Tanzania, Uganda and Zambia, five of the fifteen countries they are operating in. In the other ten countries other insecticides are better choices for IRS.
If we shelve our most effective tools hoping that something perfect will come along that has no potential downside, we’ll wait forever, and thousands will continue dying every day. These are the cases where wealthy environmental groups appear to do their best to justify their elitist stereotype, at the expense of brown people.
DDT isn’t the most effective tool against malaria and it hasn’t been shelved. And since those environmental groups don’t oppose the use of DDT, it’s not so much a case of them living up to “their elitist stereotype” as Dunning revealing his prejudices against environmentalists.
Dunning concedes that DDT resistance is a problem but then argues:
Moreover, we’ve since learned that it is still effective against resistant mosquitos, only a little less so. Susceptibility in resistant strains goes down to 63%, as opposed to 87% in non-resistant strains.
Dunning doesn’t give a cite for this, so we don’t know what he is referring to, but it’s probably this 2007 study, which found that 73% of DDT-resistant mosquitoes were repelled or killed by DDT, but 92% were repelled or killed by dieldrin (which they were not resistant to). First, you can’t generalize this result — local conditions and the nature of resistance in the mosquito population could make a big difference,. The mosquito species studied, Aedes aegypti, doesn’t even transmit malaria. Second, even if DDT is still somewhat effective, that doesn’t mean you should use it — this experiment found that an insecticide that the mosquitoes were not resistant to was much more effective. (More comments on this paper here). Third, the repellent effect of DDT can actual hinder the effectiveness of vector control. Fourth, the disastrous experience of Sri Lanka in the 60s proves that DDT resistance can render it ineffective against malaria. DDT spraying had reduced malaria by so much in 1963 that there weren’t enough cases to justify spraying against malaria (though DDT continued to be used in agriculture). Unfortunately, malaria returned and when they resumed anti-malaria spraying DDT had lost much of its effectiveness because the mosquitoes had evolved resistance. By 1975, DDT was pretty much useless and they were only able to get malaria back under control by switching to the more expensive malathion.
Dunning’s final paragraph:
DDT does have its place, and its current usage is probably not too far off of what it should be. The exception is Africa where DDT’s upside far outweighs the down, and my opinion is that donors should relax their restrictions against it, and leave those decisions to the experts on the front lines in Africa. For much of the rest of the world, DDT has largely been supplanted by newer and better agricultural pesticides, and there’s insufficient reason to put collateral species under pressure. A scientific review nearly always produces better focused policy, and our DDT policy is definitely due for a tuneup.
Dunning’s proposed policy is, in fact, the current policy. Donors like USAID will fund DDT use and they let the experts decide where it will be used. That’s why, although it’s still used in some places, in most places other insecticides are used for IRS and the primary tool is long-lasting insecticide treated nets. These last for years, while DDT has to be resprayed every six months.
So what went wrong with Dunning’s podcast? I think the problem was that he was insufficiently skeptical and was taken in by a PR campaign designed to put environmentalists on the defensive by falsely accusing them of killing babies. My article with John Quiggin covers some of the history of this campaign, as does Oreskes and Conway’s excellent book, Merchants of Doubt.
If you do a podcast every week on a wide variety of topics, there will inevitably be errors and I don’t think that people will hold that against Dunning. But digging in and not making appropriate corrections will mean that people lose confidence in him. I think a good model is the the way Bob Carroll made corrections to his newsletter about second-hand smoke (Carrol was also taken in Milloy!).