By Roger E. Meiners and Andrew P. Morriss
In 1972, the U.S. government banned the pesticide DDT. The chemical had been used excessively, especially by the federal government, which refused to respect the rights of those who didn't want it on their property. The decision to prohibit DDT's use may have played a significant role in helping the bald eagle and other birds make a comeback. But it has also allowed malaria to make a comeback.
The worry of scientists three decades ago that there was no good, less toxic, cost-effective substitute for DDT to control mosquitos and other pests is as true today as it was in 1972. A disease that was on the way to being vanquished has returned with a vengeance.
The hundreds of millions of sufferers of malaria and the millions of families that lose infants to malaria are being denied an effective solution (Attaran et al. 2000, 729). The number of countries using DDT has been whittled down to 23. It is produced in only three countries and is becoming difficult to obtain. The United Nations Environment Program has put it on the hit list for extinction (Tren and Bate 2001, 22).
Besides killing a child every thirty seconds, malaria is a recurring disease for many. Children who survive malaria past infancy suffer an average of six bouts each year, making it the most common reason to miss school; adult sufferers miss an average of ten working days a year (United Nations Children's Fund [UNICEF] 1999, 4). The infection rate had fallen significantly over the decades, primarily because of DDT sprayed inside homes and on mosquito breeding sites. But as a UNICEF report describes it, "DDT was widely discredited in the 1960s because of its harmful effects on the environment" (6). So the disease is nearly back to where it was 50 years ago.
The tragedy is not being ignored. Roll Back Malaria was launched in October 1998 by UNICEF, the World Health Organization, and the World Bank to "prevent and control this centuries- old scourge" (UNICEF 1999, 1).
Since DDT is unavailable in most nations, and international agencies are shy to use it even where it is legal, the UNICEF program must rely on other measures. These include "insecticide-treated mosquito nets, mosquito coils, repellants and other materials; early detection, containment, and prevention of malaria epidemics; and strengthening of local capacity to monitor malaria in affected regions" (UNICEF 1999, 8).
The goal of Roll Back Malaria is to reduce infant mortality from malaria (not the incidence of malaria) by 50 percent by 2010. Even if that optimistic level could be reached, it is nowhere near the level of success achieved by the proper application of DDT in other countries (Goklany 2000).
In malaria prevention, the focus of Roll Back Malaria is on the use of mosquito nets. People in the tropical regions of the world all sleep under such nets. At a price of $5 to $10 each, they are expensive for people in countries where per capita personal income is measured in the hundreds of dollars per year. Moreover, the nets require continual retreatment-soaking the nets in liquid insecticide (UNICEF 1999, 3).
Substituting chemically impregnated mosquito nets for DDT has reduced exposure to DDT but increased exposure for many people to malaria, as well as to the insecticide used in treating the nets.
In regions where malaria is a scourge, people question the viability and morality of Roll Back Malaria when a proven cost-effective malaria-control product, DDT, already exists. In December 2000, the World Health Organization sponsored a meeting in Harare, Zimbabwe, entitled "Regional Consultation to Prepare African Countries Towards Reduction on Reliance on DDT for Malaria Control." Delegates to the meeting issued a statement expressing the "deep concerns of the participating member states on the possible economic and health implications of any restriction made on DDT use for malaria control" (World Health Organization 2000). In sum, the delegates noted that no cost-effective or proven alternatives that are less toxic exist to replace the job DDT does.
During the decades since the banning of DDT in the United States, research on DDT has continued. This research indicates that when DDT spraying is ended, malaria's incidence rises markedly. In the high and moderate risk regions of Columbia and Peru, for example, the risk of malaria doubled when spraying ceased in the 1990s. The disease has returned to areas in which it had been eradicated: urban areas of the Amazon Basin, Korea, Armenia, Azerbaijan, and Tajikistan. In Sri Lanka, malaria cases fell from 2.8 million and 7,300 deaths per year before DDT spraying, to 17 cases and no deaths (Roberts, Manguin, and Mouchet 2000). When the spraying stopped in 1961, malaria jumped back to 500,000 cases by 1969 (Attaran et al. 2000, 729). The spread of the disease means that it has reappeared even in the United States and Europe.
That DDT is effective has never been the main issue; the key questions concern long-term toxicity and environmental damage. Yet "claims of risks of DDT to human health and the environment have not been confirmed by replicated scientific inquiry," write Roberts, Manguin, and Mouchet (2000, 33). Evidence from more than 50 years of use indicate that, properly applied, DDT is not harmful to humans or the environment in general.
DDT appeared to be so harmful in the 1950s and 1960s because of its widespread use in heavy dosages, mostly from government spray campaigns but also from overuse by private sprayers who had not learned proper conservation. When DDT is sprayed in massive doses, birds can suffer acute effects. "The fault for this lies in the massive agricultural use of DDT. Dusting a single 100-hectare cotton field, for example, can require more than 1,200 kg of DDT over 4 weeks," write Attaran et al. (2000, 729). Unfortunately, children in developing countries are paying the cost of excessive use fifty years ago.
Attaran, Amir, Donald R. Roberts, Chris F. Curtis, and Wenceslaus L. Kilama. 2000. Balancing Risks on the Backs of the Poor. Nature Medicine 6(7): 729Ð31.
Goklany, Indur M. 2000. Applying the Precautionary Principle to DDT. December 2. Available: www.fightingmalaria.org. Cited: March 6, 2001. Roberts, D. R., S. Manguin, and J. Mouchet. 2000. DDT House Spraying and Re-emerging Malaria. Lancet 356: 330Ð32.
Tren, Richard, and Roger Bate. 2001. When Politics Kills: Malaria and the DDT Story. Available: www.fightingmalaria.org. Cited: March 5, 2001. UNICEF. 1999. Rolling Back Malaria. New York: UNICEF.
World Health Organization. 2000. Delegates' Report. February 8Ð10. Available: www.who.int/rbm/ DDT/ddt_Zimbabwe.htm. Cited: March 5, 2001.
Roger E. Meiners and Andrew P. Morriss are Senior Associates of PERC. Their paper, "Pesticides and Property Rights" (PERC Policy Series, PS-22), from which this excerpt is taken, is available from PERC and our Web site, www.perc.org. A second selection, forthcoming in the September issue of PERC Reports, will explore the reasons why DDT was overused.