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Rachel Carson, DDT, and Malaria

In an earlier post, I listed what I consider the eight most important writings in environmental ethics. I included Rachel Carson’s Silent Spring as one of the eight, but I noted that it was controversial. That controversy is the subject of this post.

Silent Spring, published in 1962, questioned the indiscriminate spraying of DDT, an insecticide, in the U.S. It questioned the logic of releasing large amounts of chemicals into the environment without understanding where these chemicals go and what their effect on human health and the environment is. The result was the rise of the environmental movement, and DDT was ultimately banned in 1972.

Since it was published in 1962, Silent Spring has received mixed reviews by scientists. In an editorial in the New York Times titled, “Fateful Voice of a Generation Still Drowns Out Real Science,” John Tierney expresses as clearly as anyone the view of scientists who do not agree with Rachel Carson. As he sees it, the human costs of banning DDT were horrific in poor countries when malaria increased after the ban. He believes the DDT ban brought about by Carson’s book substantially increased human deaths. In his view, banning DDT was reprehensible, and the science expressed in Silent Spring is bad science.

While I agree it was wrong to ban DDT (Rachel Carson also did not agree with the ban), I do not agree with the position articulated by John Tierney and others scientists. I will explain why.

DDT was used extensively during World War II to de-louse soldiers, and it was used to control mosquito populations, especially in malarial zones. It was cheap, effective, and considered safe. DDT is effective against the species of mosquito that carry malaria. How then could anyone object to using DDT to try to eradicate malaria or to the science that developed and tested it?

I will begin by listing the detrimental features of DDT when it is used to try to eradicate mosquitoes that carry malaria:

  • DDT is a wide-spectrum insecticide. It kills the good insects as well as the bad. For instance, it kills virtually all species of aquatic insects that are the primary food source for fish. On land, it kills virtually all insects, such as bees, that pollinate plants. In short, it can disrupt food supplies.
  • DDT and its break-down product, DDE, last for decades in soils and streams. Once applied, it can remain viable for decades.
  • DDT “bio-accumulates” as it passes up the food chain. DDT sprayed at a low concentration in water is taken up by algae and passed up through zoo-plankton to fish and then to mammals and birds. DDT that is eaten is stored in fat tissues and in the milk of mammals. Birds and mammals, including man, can have concentrations of DDT in fat tissues and milk that are ten to a hundred times higher than the initial concentration sprayed. For instance, in 2005, the Center for Disease Control reported that DDT was still found in the blood of virtually all U.S. citizens, although at a lower concentration than the previous decade, even though DDT was banned in 1972. Also, the levels of DDT in salmon in the Columbia River are high enough that pregnant women are warned not to eat more than one serving per month of Columbia River salmon.
  • DDT is classified as moderately toxic in acute toxicity (one-dose) tests for humans and the environment. To test for “safe” levels of DDT in water, varying concentrations of DDT are added to a series of aquaria with an equal number of fish in each. The experiment is aimed at determining the DDT concentration when fifty percent of the fish die. This is DDT’s “D50” concentration. A safety margin is added to the D50 concentration, and the resulting concentration is established as the safe concentration of DDT in water. This is the standard method for determining safe levels for any chemical in water. For humans, similar tests were conducted with rats in cages.
  • DDT has been linked to diabetes in chronic (continuous low doses) toxicity tests (e.g.,
  • DDT is less successful in eliminating the mosquitoes that carry malaria in the tropics, where they can breed year-round. Using DDT in the tropics thus leads to strains of mosquitoes that are resistant to DDT.

John Tierney and a number of scientists believe the benefits of DDT spraying outweigh these detrimental effects. I am not so sure. While I acknowledge that spraying DDT can lead to short-term declines in the mosquitoes carrying malaria, I am not sure that even the short-term benefits are worth it. Spraying DDT will cause increased reproductive problems, and high levels of DDT in mother’s milk will increase infant health problems. DDT can also potentially disrupt food supplies.

Furthermore, the long-term effects of continued DDT spraying will result in mosquitoes developing a resistance to DDT; it will no longer be effective. And that is a very serious problem. DDT should be saved in reserve for periodic serious outbreaks of malaria. It should not be used to try to eradicate malaria; not only will it  not be successful, but it will become ineffective against malarial mosquitoes when we do need to use it.

In the end, I believe that which side of this issue you are on depends largely on your philosophy of science. To the proponents of spraying, like John Tierney, science has made great strides in understanding nature. We have the necessary knowledge to control nature for the benefit of man. The scientific tests which isolate the levels of DDT from all other factors to determine the acute toxicity levels are viewed with objectivity and certainty. With this information, then, we can confidently move forward.

I am not so optimistic. I believe that nature is more complex than we can ever know. I am not so confident that we really understand the effects of DDT on humans or the environment. While I acknowledge that the acute (one-dose) toxicity tests are useful to get a general idea of the toxicity of a chemical, I find the chronic (long-term low-dose) toxicity tests less compelling. Over what range of concentrations should the tests be run and for how long? However, my biggest concern with chronic toxicity tests is that they don’t test the interaction between DDT and other pesticides. What is the interaction between DDT and other pesticides at low, long-term doses? Thousands of chemicals have been developed and used daily since World War II. How do they interact with each other? Also, what compounds do they break down into, and how do these chemicals interact with each other? We have little or no information about most of these interactions. Without this understanding, it seems to me that our knowledge is pretty limited with regard to pesticides and their effects. In short, as an ecologist, I do not believe that these simple reductionistic laboratory tests can deliver the knowledge necessary for us to confidently control nature for our benefit.


3 thoughts on “Rachel Carson, DDT, and Malaria

  1. Where did malaria increase after the “ban” on DDT?


    1. The ban was in the U.S. only. EPA’s order, unlike an earlier federal court order, allowed U.S. manufacturers to keep on producing for export, thereby more than doubling the amount of DDT available to fight malaria and dropping the cost overseas.

    2. However, the World Health Organization had abandoned its ambitious program to eradicate malaria from Africa in 1965, seven years before the U.S. banned crop use of the stuff. WHO acted because DDT-resistant and DDT-immune mosquitoes showed up in Africa (from overuse in agriculture), and most nations didn’t have the money or governmental discipline to mount successful campaigns using DDT.

    3. The death toll and infection numbers from malaria have been in constant decline since peak DDT use in 1959 and 1960. No increase in malaria, no increase to blame on a lack of DDT.

    4. DDT was never banned in Africa, nor Asia. Any nation there can still use the stuff today, if it chooses to. Why would a nation suffering from malaria use stuff that is increasingly ineffective, and toxic?

    You’re right about the temporary nature of DDT treatments. Considering that the fears of Tierney and others are largely imaginary, let’s forget about DDT and get about the business of beating malaria, eh?

  2. I am shocked that you believed what Tierney wrote. This Rachel Carson smear has been debunked for quite a while.

    For your own sake, please be very skeptical of wild accusations and smears. You seem very bright and capable, but you should have found the information from the first post above before you bought all of Tierney’s apparent fabrications.

  3. Dear Charley,
    Thank you so much for your post on DDT.As you may be already aware, DDT was first used for Malaria Control in the extreme area of Rwangaminyeto, Kihihi Sub County, presently, Kanungu district in South Western Uganda from 1959-1960 during the global WHO pilot project and completely banned in the 1980’s. The debate for the re-introduction of DDT began in early 2004. This attracted a lot of public debate. Between June-July 2005, the Ministry of Health commissioned an Environmental Impact Assessment (EIA) which consulted few stakeholders.

    In early 2006, a study on the impact of DDT use was done in Kanungu by some few individuals from
    the Pathology Department, Faculty of Medicine, Makerere University and Mulago Hospital, Department of Medicine. In November 2006, the National Environment Management Authority (NEMA) called for a public hearing on the use of DDT in Uganda and with due disregard of public views, NEMA went a head and authorized the use of DDT in Uganda. These conditions and many others led to the birth of the Uganda Network on Toxic Free Malaria Control (UNETMAC).

    Between April- May 2008, DDT indoor residual spraying (IRS) for Malaria control was piloted in the two districts of Oyam and Apac in Northern Uganda. During this period, UNETMAC members monitored the whole program activities and gross violations of the guidelines under the Stockholm Convention on POPs as well as those under the WHO were noted.

    By Mid 2008, UNETMAC at the time not being a legal entity mobilized seven of its members to petition the government of Uganda over the misuse of DDT. The petition was filed in the High Court through two law firms of Tumusiime and Kabega Co Advocates and Nile Law Chambers. This prompted a court injunction, which argued that several ten thousand small-scale farmers had lost their income of selling organic produce due to the spraying. This case was however later dismissed not on merit but simply because the lawyers failed to show up in court for three consecutive times.

    Upon receiving this sad news, UNETMAC with financial support from the Swedish Society for Nature Conservation (SSNC) mounted a campaign for increasing public awareness about the dangers of DDT on human health and environment in late 2008 and early 2009.

    By Mid 2009, UNETMAC at this time as a legal entity with support from members filed another petition this time in the Constitutional Court (Constitutional Petition No. 14 of 2009) through another law firm, Niwagaba and Mwebesa Co Advocates. Initially, the case progressed well up to the rescheduling phase. At this stage, the case came to a very difficult progress and has been prolonged a few times. The reason for this delay is due to the fact that the constitutional court has not been fully constituted for a long time. The court is currently composed of only three judges and yet, it is supposed to have five judges at every sitting. Due to this technical mess, many constitutional petitions have not been handled.

    At the moment however, the lawyer says that upon collaborating with the Court Registrar, the case can be fixed by hiring the two missing judges from the Court of Appeal to sit on the Constitutional Court bench. This requires a lot of lobbying for this to happen. It is at this moment that the lawyer says that with some monetary facilitation, he can privately lobby the Court Registrar. The lawyer also requires part payment of his legal fees. Initially, he was only paid a minimum fee.

    At this time also, it is technically prudent to collect new data in the areas where DDT was sprayed especially analyzing the potentially negative impacts the spraying may have caused. This calls for a scientific study in Oyam and Apac districts. The data collected will be so beneficial during the court process. This activity will also help in mobilizing local people in the sprayed areas to testify in court.

    Most importantly also is the need for UNETMAC to support a total global phase-out of DDT on the international level. As such, UNETMAC would very much wish to participate at the forthcoming COP6 in Geneva in May and also the World Health Assembly (WHA) also in Geneva in May 2013 in order to strengthen the global policy support for a reduced reliance and total phase-out of DDT by increasing pressure on the exemption rule for DDT.

    Although the government of Uganda claims that it has stopped using DDT and that, the surplus DDT has been flown back to South Africa, the use of the chemical seems to be continuing secretly mainly by farmers and traders within the country. With expected funding from the PMI through Abt Associates, Uganda intends to implement a comprehensive IRS programme using DDT as one of the pesticides, refer to the link: Although the contract does not directly mention using DDT, the information obtained from the local sources in Uganda clearly reveals that DDT will be used. The contenders argue that the chemical is cheap compared to other chemicals because of its longer residual effect. The risk of severe economic impacts from spill-over effects and from deliberate misuse of DDT in agriculture on small holder farmers will therefore be evident in Uganda.

    It is therefore important to note that the risk that DDT will be reintroduced is pertinent with potential devastating consequences for even more farmers. This trend of events is in contravention of the United Nations (UN) political goals of strengthening capacity of countries to transfer safely to reliance on sustainable alternative products, methods and strategies to DDT and to the goal of the Stockholm Convention on POPs which is to ultimately eliminate the use of DDT.

    Although malaria is one of the major global health problems with devastating impact on many populations, particularly in Africa and Uganda, there are alternatives to DDT to deal with this disease as demonstrated by examples from Kenya, Ethiopia, Mexico and Vietnam. As you also already aware, UNETMAC has been fighting this deadly tropical disease in Uganda both in the field and on the policy level. UNETMAC supports an integrated and sustainable approach to fight malaria and save lives of people. For these reasons, UNETMAC is dedicated to a worldwide phase-out of DDT.

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