Engineer Indur Goklany, a frequent contributor to WUWT and occasional commenter has more than a few things to say about commenter Ed Darrell’s views on Malaria posted on WUWT yesterday. There’s so much in fact, that I’ve dedicated a whole guest post to it. -Anthony
Guest Post by Indur Goklany
Ed Darrell has two sets of comments, one of which, I believe, is fundamentally flawed, and the other I would agree with, at the risk of being accused by Alexander Feht of being obsequious once again (See Alexander’s comment on September 11, 2010 at 11:28 am).
In 1972, about two million people died from malaria, worldwide.
In 2008, about 880,000 people died from malaria, worldwide. That’s fewer than half the mortality the year the U.S. stopped DDT spraying on cotton.
If it’s cause-effect you were trying to establish, I think you missed.
RESPONSE: The flaws in Ed’s analysis are aplenty.
First, although the US banned DDT in 1972, its use continued in much of the rest of the world. [If I remember correctly, the Swedes had banned it earlier.] In fact, US production of DDT for developing country use continued into the mid-1980s. Also, it took a few years for US environmentalists to ensure that the US domestic ban was — in the best traditions of cultural imperialism and bearing the white man’s burden — exported to other countries [without their (informed) consent, mind you]. [Notably, the US ban was imposed only after malaria had been wiped out in the US for practical purposes. See Figure 13, here.] In addition, countries had stockpiles which they continued to use, and not all developed countries were initially on board with eliminating DDT use worldwide. Furthermore, by 2008 some developing countries that had stopped DDT use had resumed its use. So it is not meaningful to use either 1972 or 2008 as endpoints for developing global estimates for the efficacy (or lack of it) of DDT in dealing with malaria..
Second, while DDT is in many instances the cheapest and most cost-effective method of reducing malaria (where it works, because it doesn’t always work) the death and disease rates are also sensitive to other factors, none of which have remained stationary between 1972 and 2008. These factors include general health status, adequate food and nutrition, public health services, and so on. So, it makes little sense, without adequately accounting for these factors, to compare deaths for malaria (or death rates, which would be more correct) between 1972 and 2008 to say anything about the effectiveness of DDT.
Fortunately, though, we have results of some “policy experiments” which were undertaken inadvertently — undertaken, I note, without the consent of the subjects of these experiments, something that would not be allowed in any hospital in the US, I suspect. These “experiments” allow us to evaluate the benefit of DDT (or lack thereof). As noted here (pp. 7-8) in a paper published a decade ago by Africa Fighting Malaria, it was noted that:
“Given the higher costs and, possibly, the greater efficacy of DDT, it is not surprising that despite the theoretical availability of substitutes, malaria rebounded in many poor areas where (and when) DDT usage was discontinued (WHO 1999a; Roberts 1999, Roberts et al. 1997, Sharma 1996, Whelan 1992, Guarda et al. 1999, Bate 2000). For instance, malaria incidences in Sri Lanka (Ceylon) dropped from 2.8 million in the 1940s to less than 20 in 1963 (WHO 1999a, Whelan 1992). DDT spraying was stopped in 1964, and by 1969 the number of cases had grown to 2.5 million. Similarly, malaria was nearly eradicated in India in the early 1960s, and its resurgence coincided with shortages in DDT (Sharma 1996). The population at high- to medium risk of contracting malaria in Colombia and Peru doubled between 1996 and 1997 (Roberts et al. 2000b). Malaria has also reappeared in several other areas where it had previously been suppressed, if not eradicated (e.g., Madagascar, Swaziland, the two Koreas, Armenia, Azerbaijan, Turkmenistan; Roberts et al. 2000b, and references therein). Similarly, Roberts et al. (1997) showed that Latin American countries (e.g., Ecuador, Belize, Guyana, Bolivia, Paraguay, Brazil and Venezuela) which had discontinued or decreased spraying of DDT inside homes saw malaria rates increase. Guarda et al. (1999) also note that in 1988, when DDT use was discontinued, there were no cases of Plasmodium falciparium reported in Loreto, Peru. The number of cases increased to 140 in 1991. By 1997, there were over 54,000 cases and 85 deaths (see, also, Goklany 2000c).
“But the best argument for indoor-spraying of DDT is that in many areas where malaria experienced a resurgence, reinstating DDT use once again led to declines in malaria cases. For example, Ecuador, which had previously seen its malaria rates rebound once DDT spraying had been reduced, saw those rates decline once again by 61 percent since 1993, when DDT use was increased again (Roberts et al. 1997). The same cycle occurred in Madagascar where the malaria epidemic of 1984-86, which occurred after the suspension of DDT use, killed 100,000 people. After two annual cycles of DDT spraying, malaria incidence declined 90 percent (Roberts et al. 2000b).”
Since then, we have results of the on-again and off-again policy with regard to DDT from KwaZulu-Natal Province in South Africa:
“DDT spraying in that area started in 1946. By 1974, Anopheles funestes, the mosquito species associated with year-round prevalence of malaria in that region, had been eradicated [see Figure below.]. In the 1991/1992 malaria season, the number of malaria cases was around 600 in the Province of KwaZulu-Natal (KZN). However, in 1996, DDT was replaced by synthetic pyrethroids. In 1999 members of A. funestus were found in houses in KZN that had been sprayed. In 1999/2000, there were more than 40,000 cases in KZN. In 2000, DDT was brought back. By 2002, the number of cases had dropped to 3,500.” Source: Pre-edited version of Goklany (2007), pp.79-180.
See the Figure 1.
I have also provided additional references below, if one is interested in following up.
For a broader discussion, I recommend the chapter, “Applying the Precautionary Principle to DDT,” in The Precautionary Principle: A Critical Appraisal of Environmental Risk Assessment (Cato Institute, Washington, DC, 2001). A previous version of this chapter is available free at
Figure 1: From Goklany (2007), based on R. Tren, “IRS & DDT in Africa — past and present successes,” 54th Annual Meeting, American Society of Tropical Medicine and Hygiene (ASTMH), Washington, DC, December 11-15, 2005.
RESPONSE: I agree. For a long time, malaria control was neglected. Even the World Health Organization would not recommend DDT use indoors. It was revived, and even became (almost) chic thanks to a number of very high profile individuals including George Bush and Bill Gates, as well as lesser known people such as Don Roberts, Amir Attaran, Roger Bate and Richard Tren (all associated with Africa Fighting Malaria) . I delude myself into thinking that I played a minor role in helping ensure that DDT did not get banned outright under the Stockholm Convention.
Whatever people may think of Bill Gates stance on global warming, there is little doubt that he exhibited substantial political courage in espousing malaria control with DDT. That’s essentially why I was/am disappointed by his posting that set me off on this blog.
Perhaps I should have titled my piece, “Et tu Bill Gates!”
D. R. Roberts, et al. “DDT, global strategies, and a malaria control crisis in South America,” Emerging Infectious Diseases 3 (1997): 295-301 (1997).
D.R. Roberts, et al., “A Probability Model of Vector Behavior: Effects of DDT Repellency, Irritancy, and Toxicity in Malaria Control,” Journal of Vector Control 25 (2000): 48-61.
Karen I. Barnes et al., “Effect of Artemether Lumefantrine Policy and Improved Vector Control on Malaria Burden in KwaZulu Natal, South Africa,” Public Library of Science Medicine (2005): DOI 10.1371/journal.pmed.0020330.
P. E. Duffy and T. K. Mutabingwa, “Rolling Back a Malaria Epidemic in South Africa,” Public Library of Science Medicine (2005): DOI: 10.1371/journal.pmed.0020368.
R. Tren, “IRS & DDT in Africa — past and present successes,” 54th Annual Meeting, American Society of Tropical Medicine and Hygiene (ASTMH), Washington, DC, December 11-15, 2005.
D. H. Roberts, “Policies to Stop/Prevent Indoor Residual Spraying for Malaria Control,” 54th Annual Meeting, ASTMH, Washington, DC, December 11-15, 2005.
I.M. Goklany, The Precautionary Principle: A Critical Appraisal of Environmental Risk Assessment (Cato Institute, Washington, DC, 2001). Chapter 2 deals with malaria and DDT.