When DDT was introduced more than 60 years ago, it initially scored victory after victory in the fight against malaria — nearly eliminating the deadly disease in many areas. But these wins were mostly short-lived, as mosquitoes rapidly developed resistance to the chemical. Today, its effectiveness is a fraction of what it once was; meanwhile an arsenal of better and safer anti-malaria interventions has been developed, including effective chemical-free strategies.
And so, under the auspices of the Stockholm Convention, the nations of the world have committed to phasing out DDT, while allowing it to be used in the short-term in those few places where it's still effective and other methods of malaria control are unavailable. This is an approach PAN enthusiastically supports.
Unfortunately, DDT use isn't confined to these situations. It remains the first and only line of defense against malaria in some parts of the world, even in areas where resistance to it is high among mosquito populations, as discussed in a recent report. So while experts agree that DDT can occasionally play an important role in a multi-pronged approach to malaria control, it's become clear that often its use is anything but judicious.
A mountain of evidence on health effects
Compounding the situation is the failure by many to take seriously the health effects of DDT. A mountain of research exists linking DDT exposure to various human health harms (see the The Pine River Statement for an excellent review of over 400 studies). Unfortunately, this evidence has been disregarded by public health officials in some malarial areas.
A good example is a recent paper coauthored by a Senior Medical Officer for Uganda's Malaria Control Programme. The authors measured liver enzyme levels in workers engaged in indoor residual spraying (IRS) of DDT, and finding them to be within normal ranges, leap to the conclusion that their results "confirm the safety of DDT as used in IRS operations" — a statement that ignores not only the hundreds of studies that do find connections between DDT and disease (including a similar study that did find abnormal enzyme levels in sprayers), but also the fact that many diseases don't affect liver enzyme levels.
Or consider the declaration by the Namibian Minister of Health that "DDT is safe for humans and the environment. Since the 1940s thousands of scientific studies have investigated potential harm to human health from DDT. Almost all these studies are weak, inconclusive or contradictory; in other words there is no evidence of harm."
Against this background of denial I was encouraged to see a brand new article in Environmental Health Perspectives (EHP) that unequivocally repudiates such statements. "DDT and Malaria Prevention: Addressing the Paradox," coauthored by South African DDT expert Henk Bouwman, states that
Given the current evidence, an unqualified statement that DDT as used in IRS is safe is untenable.
The authors urge a precautionary approach to using DDT, including "use and exposure reduction." The paper divides the spectrum of views on DDT into three camps: pro-, anti-, and centrist, and concludes that the centrist take on DDT is "the only logical and rational conclusion."
Interestingly, all of their examples of the pro-DDT position come from Africa Fighting Malaria, a Washington, DC-based, anti-regulation front group that promotes DDT as a virtual silver bullet for malaria control. AFM's pro-corporate, anti-environment agenda and its connections to conservative think-tanks has been the subject of several articles in the progressive media.
(In case you're wondering: While the paper doesn't mention PAN specifically, it notes only one instance of "outright anti-DDT activity" and it's not us, so presumably the authors include PAN and our allies within the logic and rationality of the centrist position.)
DDT promoters still trying
This is the second time in the past year that AFM has been called out in EHP. In July, a letter from malaria experts Hans Herren and Charles Mbogo said that AFM's habit of
...reduc[ing] the complex issue of malaria control to a single, dichotomous choice between DDT and malaria...is a dangerous oversimplification and a distraction from the critical dialog on how to effectively combat malaria around the world — particularly in African communities.
And still AFM fights on, even as their views are called "untenable" and used as examples of an unreasonable position. In a new logic-defying paper, they criticize Latin America's recent, successful, DDT-free fight against malaria. They assert that by highlighting these success stories, "UN agencies are misleading the public by claiming that malaria can be controlled without insecticides, notably DDT."
You can't make this stuff up. They argue that the decreases in malaria in the region were due to the better distribution of malaria drugs rather than the introduction of insecticide-free mosquito control techniques, as reported by the UN. But whether the success is due to better drug distribution or the new vector control measures is irrelevant: malaria incidence still went down without the use of DDT or other insecticides.
When The Pine River Statement was published in 2009, lead author Brenda Eskenazi noted in an accompanying press release that: "Clearly, more research is needed…but in the meantime, DDT should really be the last resort against malaria, rather than the first line of defense."
Slowly but surely the use of DDT is moving towards this ideal. Let's hope the concerted efforts of logic-challenged groups like AFM don't stand in the way.
UPDATE (March 8, 2011): The data in the AFM paper mentioned above (the one criticizing UN for highlighting successful DDT-free anti-malaria projects in Latin America) appears to have been manipulated by the authors. Tim Lambert has the analysis on his blog here.