A recent New York Times article unveiled an interesting archaeological discovery: the earliest genetic evidence of malaria infection. According to the February 20 article by John Noble Wilford, “The new findings provided strong support for the hypothesis that a widespread outbreak of an especially lethal form of malaria in the fifth century AD probably contributed to the decline of the Roman Empire.” It was not mentioned in the piece, but the first thing to come to mind for us was this: Had DDT come along just a few centuries sooner, the empire might have been spared.
Malaria continues to topple empires today, killing over one million people every year, mostly children and pregnant women. (As Dr. Wenceslaus Kilama, chairman of Malaria Foundation International, has said, the malaria epidemic “is like loading up seven Boeing 747 airliners each day, then deliberately crashing them into Mt. Kilimanjaro.”) The number of deaths is increasing, especially in developing countries. Yet while these countries ought to have every method available to control this disease, political leaders and environmental groups recently came very close to banning an important weapon in the fight against malaria: DDT.
In December 2000, international delegates and observers met in South Africa to negotiate the Convention on Persistent Organic Pollutants, a list of 12 chemicals, uncluding DDT, which will soon be banned worldwide. Fifteen countries requested exemptions for their use of DDT in public-health programs—but even they will have to comply with the treaty’s potentially onerous regulatory restrictions. In May, delegates from the United States and more than 100 other countries will meet in Stockholm, Sweden to sign the treaty, a legally binding instrument.
Many methods of protection against malaria have been devised. International public-health officials currently favor a regimen of anti-malarial drugs for foreign visitors to malarial areas, and pesticide-impregnated bed nets for local people. These methods are designed to try to prevent infection—the prophylaxis method.
But one of the most effective methods, and probably the cheapest, is to spray the inside walls of houses and buildings with insecticides to repel, irritate, and kill mosquitoes that carry the malaria parasite—the vector-control method. One of the oldest pesticides is still the best for controlling mosquitoes; this is dichloro-diphenyltrichloroethane, commonly known as DDT. Despite a surge in malaria incidence in the developing world, DDT production is decreasing, and its use is limited to those few countries that still have stockpiles or whose governments produce the chemical.
The reason for this baffling disparity is that DDT has been damned by environmentalists. Gradually, governments in industrialized nations have been persuaded to restrict DDT due to fears of damage to the reproductive process of birds of prey. The heroic malaria-eradication program of the postwar years used DDT as its primary weapon. This program succeeded in North America and southern Europe, and greatly reduced incidence in many other countries. But eradication was not possible for many developing nations. Public-health activity in these countries is wholly or partly reliant on funding from overseas aid agencies. Since donor countries frown on DDT, these agencies are extremely reluctant to countenance its use in other countries. Belize, Mozambique, and Bolivia stopped using DDT in their public-health programs because they feared the loss of aid from international agencies. It is highly likely that other countries have also succumbed to these pressures. The urge for donor nations to dictate how donations are spent is obviously compelling, but if aid is really to save lives, the recipients must be allowed to decide for themselves what is good for them. The advice and technical assistance that developed nations can give to these countries is invaluable, but policies that are right for wealthy nations may not be right for poor ones.
Spraying DDT in houses and on mosquito breeding grounds was the primary reason that rates of malaria around the world declined dramatically after the Second World War. Nearly one million Indians died from malaria in 1945, but DDT spraying reduced this to a few thousand by 1960. However, concerns about the environmental harm of DDT led to a decline in spraying and, likewise, a resurgence of malaria. Today there are once again millions of cases of malaria in India, and over 300 million cases worldwide—most in sub-Saharan Africa. Cases of malaria in South Africa have risen by over 1000 percent in the past five years. Only those countries that have continued to use DDT, such as Ecuador, have contained or reduced malaria.
Malaria is clearly a human tragedy, but it is also an economic disaster. According to Jeffrey Sachs of Harvard’s Center for International Development, lost productivity from malaria costs afflicted patients about 1 percent of Africa’s wealth every year. In many countries, malaria halves the economic growth that would otherwise occur.
While there is some evidence that DDT causes environmental harm, damage occurred only during widespread agricultural use of DDT in the 1950s and 1960s. It was alleged that DDT led to eggshell thinning and other effects in certain birds; these problems were shown to be reversible. No study in the scientific literature has adequately shown any human health problem resulting from DDT. Therefore, low-dose use of DDT indoors is unlikely to cause any significant harm to the environment or people.
Yet in 1995, the United Nations Environment Program proposed an international treaty to reduce and/or eliminate 12 Persistent Organic Pollutants (POPs), including DDT, from worldwide production and use. The result of such a process is obvious. As environmentalists have pushed to eliminate DDT over the years, the relationship between decreased DDT use and increasing malaria cases has become very clear (see graph 1).
Restrictions on DDT use have been the inevitable result of its listing on the POPs register.
Malaria is a severe health problem throughout much of the world, partly because the world’s poorest countries have few financial resources to control it. This is most striking in Africa, where very poor and malarious countries such as Benin, Ethiopia, Madagascar, Mozambique, Nigeria, Tanzania, the Gambia, and others have annual public-sector health budgets of under $8 per capita. That is not much more than the retail price of a single pill of Lariam, a leading malaria drug, and it is a negligible amount with which poor countries must somehow deal not only with malaria but also with water-borne diseases, AIDS, and other health needs.
The danger to poor countries of banning or restricting DDT must be understood in light of this poverty. Although DDT is relatively cheap, for an extremely impoverished country even DDT may be expensive to use. Costlier alternative insecticides are out of the question. The increased reporting requirements of the POPs convention will probably harm thousands—potentially millions—of people. Although DDT is produced only in two socialist countries for government monopoly use, it is not disputed that DDT is a much less expensive and often more effective insecticide than its alternatives.
In a recent study, the World Health Organization estimated that malathion, the cheapest alternative to DDT, costs more than twice as much as DDT and must be sprayed twice as often. Deltamethrin, an alternative recommended by environmental groups, is more than three times as expensive as DDT. Propoxur, which is often highly effective, costs 23 times as much as DDT.
The government of India, within its National Anti-Malaria Program (NAMP), uses a number of insecticides, including DDT, malathion, deltamethrin, and others. India has reported to the World Health Organization that malathion and the pyrethroid insecticides continue to cost at least three times as much as DDT. NAMP concluded that it cannot use these more expensive insecticides without leaving tens of millions of Indians unprotected from malaria (see graph 2).
These experiences show that DDT costs less than pyrethroid insecticides. There are also large costs in phasing out DDT house spraying and instead relying on strategies such as insecticide-treated bed nets or pharmaceutical drugs. Bed nets typically cost about $4 each to buy and must be treated with insecticide periodically. And each person in a house needs a bed net. Similarly, to ensure the lowest disease resistance to drugs, each drug should be administered by health-care workers at clinics, which is very expensive.
In sum, there is no alternative to DDT to which poor countries can switch without encountering significant new costs, costs that cannot be met out of their current health budgets. Switching to an alternative is difficult even for a fairly developed country such as South Africa, and it may verge on impossible for poorer countries. In addition to the costs already discussed, any alternative will require further costs for training, technical advice, and so on.
DDT use must be allowed to continue until technological advances derive a better, less-costly alternative. Once it becomes unnecessary, it will fall into disuse on its own. Developed nations (and their aid agencies and environmental groups) pressuring countries to abandon DDT for public-health uses will kill thousands of people and cost millions of dollars. It’s a mistake that does not need to be made.