DDT as a repellent

by John Q on August 9, 2007

I got an email today from Phillip Coticelli at Africa Fighting Malaria pointing to a study by Donald Roberts (PDF), showing that DDT has a repellent effect in addition to its toxicity. The key finding is that that three out of five DDT-resistant Aedes aegypti mosquitoes avoid huts sprayed with DDT. Roberts argues that this is a reason for preferring DDT to alternative pesticides such as dieldrin. A few points about this are worth making
* First, it’s good to see AFM acknowledging the fact of pesticide resistance, which primarily accounts for the abandonment of large-scale attempts to eradicate malaria-carrying mosquitoes with pesticides. The libel put out by people like Steven Milloy and AFM founder Roger Bate[1], in which it is suggested that the failure of the eradication program was due to a mythical ban on DDT imposed at the behest of environmentalists, who callously caused millions of deaths, depends critically on ignoring resistance.
* Second, although the study is new, the claim is not. Roberts has been arguing the importance of repellent and irritant effects for a long time. And while the reporting of this study suggests that these benefits are unique to DDT, other work by Roberts has found that permethrin and deltamethrin are just as effective in this respect.

How does this relate to the general debate over the use of hut spraying as a strategy to fight malaria?

First, it’s important to observe that, while DDT was never banned, it fell out of favor in the from the 1970s onwards as a result of the failure of the WHO’s attempt to eradicate malaria through spraying and of the adverse consequences of widespread use as an all-purpose pesticide, mainly in agriculture. The concerns which led to the abandonment of large-scale spraying weren’t as directly relevant to the alternative of indoor spraying, but past failures and the generally bad reputation of DDT didn’t help those advocating this strategy, notably including Roberts. In addition, the economic crises of this period made it difficult to organise the systematic programs required. International aid donors and organizations concerned with malaria focused mainly on the use of bednets impregnated with insecticides, and on the development of improved treatments.

If indoor spraying with DDT had an undeservedly bad reputation in the late 20th century, the reverse is the case now. Thanks to the campaigns of AFM and others, it is taken for granted in conservative circles that DDT is a panacea, banned by evil environmentalists. As a result, whereas donors were once chary of funding DDT-based approaches, now poor countries are being pushed to use DDT whether or not it is appropriate.

It is, in some sense inevitable, that aid will come with strings attached, and that these strings will be pulled by domestic political forces in the donor countries. If the result is more money to fight malaria, it’s better to accept the associated constraints and take the money. Still, it would be good if we could move to policy driven by evidence, rather than by rich-country politics.

fn1. Acting on behalf of the tobacco industry which was fighting WHO attempts to restrict the spread of smoking, and needed to hit them on another front.

{ 3 trackbacks }

HS Debate ‘08 | After Corbu
08.09.07 at 10:51 pm
Science Blog » Blog Archive » Study finds that DDT not the most effective for IRS
08.20.07 at 6:03 pm
Science Blog » Blog Archive » Birds in The News, Postponed
08.21.07 at 3:13 am



Matt Kuzma 08.09.07 at 3:06 pm

You may want to fix this:

it fell out of favor in the from the 1970s onwards

There are a great many ridiculous statements about the ability of environmentalists to affect world-wide bans on the use of anything. I think I speak for a lot of environmentalists when I say I only wish we had as much clout as conservatives claim we do. Sadly, otherwise avid free-market advocates tend to downplay the power of the consumer to make informed decisions and to avoid buying products with terrible side-effects. Especially when they can vilify environmentalists.


Rich Puchalsky 08.09.07 at 8:58 pm

Why bother with anything from Africa Fighting Malaria? As your footnote mentions, they were formed by Big Tobacco in order to harm publlic health efforts in general. Who cares what they think, other than to assume that it must automatically be wrong?


swampcracker 08.09.07 at 9:47 pm

“Follow the money.” One would think their former affiliations would tell you everything about them.

Not one of them is qualified toxicologist. It amazes me how a JD degree still trumps a PhD in science.

These AFM folks are belicose nut cases. Why pay them any more attention?


swampcracker 08.09.07 at 10:00 pm

P.S. DDT is not a repellent; it’s a repugnant.


James 08.09.07 at 11:19 pm


SG 08.10.07 at 9:01 am

I think this issue of repellence was discussed a while ago on a blog by called Bug Girl, who is an entymologist (maybe you can get to it through Deltoid). From memory she concluded that the repellence aspect (which is well known) has been overstated, particularly in regards to the development of resistance. But I know nothing about this stuff, I just read it in passing.


jet 08.10.07 at 2:00 pm

It is, in some sense inevitable, that aid will come with strings attached, and that these strings will be pulled by domestic political forces in the donor countries.

And “the ban” that never existed was implemented by donor countries pulling strings the other way. For instance, the EU will not accept agro imports from countries with detectable levels of DDT. While not de jure ban, this is a de facto ban on agro imports, prohibiting DDT usage, in the same spirit of 40 years of donor countries manipulating who can use DDT.

And to claim that the environmental movement didn’t have a strong say in the change of DDT usage in the 60’s onward is … misinformed at best. But since these arguments continue to be ignored or just shouted down here and at Deltoid, I know that the “at best” is too kind.


bi 08.10.07 at 5:29 pm

Wow great. So there’s no outright ban on DDT, but there’s a de facto ban.

In other words, Milloy’s wrong, but he’s still right…?

Goo goo g’joob.


qtn 08.10.07 at 6:08 pm

this topic always reminds me of the flying cats of borneo: http://www.cdra.org.za/creativity/Parachuting%20cats%20into%20Borneo.htm


Barry 08.11.07 at 2:03 pm

Problems using your words, bi?

Go to Deltoid (in Scienceblogs – see ‘Tim Lambert’ in the blogroll here) and search for ‘DDT’. There will be links to many academic articles about DDT.

Not as entertaining as propaganda mill BS, but that’s one of the things about being an adult.


J F Beck 08.11.07 at 4:22 pm

Tim Lambert (Deltoid) is not an accurate source of information on DDT: his DDT posts are riddled with errors and misrepresentations. Steve Milloy is a paragon of honesty by comparison.


bi 08.11.07 at 6:47 pm

I’m wrong, but I’m still right! I’m wrong, but I’m still right! I’m wrong, but I’m still right! …


bi 08.11.07 at 6:56 pm


Hah. Well, my hands are already quite full with all those debunkings of the “there’s no anthropogenic global warming and even if there is it’s all China’s fault, or maybe Al Gore’s fault” thingies…

But of course, knowledge is good, unless it’s negative knowledge.


Pinko Punko 08.12.07 at 7:10 am

What j f beck said is certainly not true. Making Milloy look virtuous is like walking out of a black hole.

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