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South Africa Readers Digest, December, 2000

This insecticide is critical for controlling a dangerous upsurge in malaria 

DDT Should Not Be Banned 

By John Dyson

When Oka Priyanti Came home from school on a Wednesday morning in April, her, mother Sumiati, working outside their bamboo house in the hills of central Java, Indonesia, asked what was wrong. "I'm dizzy and my tummy's sore," the. 13-year-old girl complained. 

The village clinic gave her medicine, but by Friday, Oka was fighting a raging fever. Her father, Kholil, rented a mini-bus to take her to a hospital. But the vehicle had scarcely left the village when Oka died in her parents' arms. 

Oka had contracted malaria from a mosquito bite; she was the third of Kholil and Sumiati's six children to perish from the disease. Countless other families are suffering similar - and needless - tragedies throughout the developing world. For malaria, until recently under tight control, is staging a devastating comeback. 

According to the World Health Organisation estimates, there are 300-500 million cases of malaria each year and around one million deaths. These numbers are climbing, by up to 20 percent a year in some regions. Peru, for example, experienced a seven-fold increase between 1990 and 1996. Cases of a fatal strain of malaria jumped from 140 to 36 000 in the Loreto region of the Amazon basin. South Africa had 8 750 cases and 44 deaths in 1995, but nearly 51000 cases and 393 deaths in 1999. Just one village near Oka Priyanti's home in Indonesia had around 15 cases a year through the early 1990s, but 921 last year. 

Residents of Western countries are also at risk. Not only are travellers to the developing world being infected but occasionally disease carrying mosquitoes are being brought into Europe by aircraft from the tropics. 

According to many scientists and health experts, a number of factors are responsible for the resurgence, including the increasing resistance of the malaria parasite to treatment drugs. But one reason towers above all others. 

"For years, the rich, developed nations that no longer have malaria have pressured tropical countries which do into giving up DDT," says Don Roberts, professor of tropical public health at the Uniformed Services University of the Health Sciences in Bethesda, Maryland. "When countries stop using DDT, malaria spirals out of control." Even so, the United Nations Environmental Program is on the verge of a momentous, and controversial, decision - to phase out the use of DDT." 

Lethal to insects: DDT was long considered a wonder chemical. The story began on the eve of the Second World War, when a Swiss chemist named Paul Hermann Müller noticed something strange. No matter how thoroughly he cleaned a cage in which he'd tested the chemical dichlorodiphenyltrichloroethane, the flies he put into it died as soon as they touched the glass. 

DDT, it turned out, was long lasting and extremely toxic to insect nervous systems, but virtually harmless to humans. During the war it was sprayed on, landing sites to protect invading Allied troops, And US forces were issued DDT with which to talc themselves for lice prevention. In 1944, the entire city of Naples was dusted to snuff out an epidemic of typhus-carrying body lice. For his work developing DDT, Müller was awarded the Nobel Prize in 1948. 

After the war DDT was used throughout the world to combat yellow fever, typhus and, elephantiasis. But top on the hit list were the more than 60 species of mosquito that carry the malaria parasite. 

DDT kills mosquitoes on contact. Used with other measures, such as draining swamps, DDT spraying programmes wiped out malaria from developed countries, including the US, Europe, Japan and Australia. 

DDT was powerfully effective even where malaria was not eradicated. India's annual malaria death toll of 800 000 was cut to virtually zero by the late 1960s. In Sri Lanka, DDT reduced, 2,8 million cases a year to just 17. In parts of Indonesia, nearly a quarter of the population were infected with malaria when Oka's parents were still teenagers, but twice-yearly sprays of DDT cut infections to one in a hundred. 

"To few chemicals does man owe as great a debt as to DDT," the US National Academy of Sciences concluded in 1970. It reported that DDT had prevented many millions of deaths that would otherwise have been inevitable. 

Mosquitoes may develop resistance to DDT. Still, the chemical is a very powerful repellent when sprayed on the inside walls of human habitations; mosquitoes that fly inside soon leave: In one experiment in the Amazon region of Brazil, the human bite rate was 97 percent less in a hut sprayed with DDT than in one that wasn't. 

Today, indoor spraying is the only permitted use for DDT. "To control malaria you don't necessarily have to kill the mosquito," says US Navy medical entomologist Mike Bangs. "You only have to stop it biting humans." 

Agricultural ban: While DDT was being employed in the fight against malaria, farmers were also dusting crops with mountainous quantities of the stuff to kill insect pests. This posed a potential environmental threat, for traces of DDT were soon found in the fat tissues of every living thing from humans to polar bears and albatrosses. Concern also mounted when it appeared that DDT might be responsible for the decline of several, bird species. The United States banned the agricultural use of DDT in 1972 and most developed countries did the same. 

DDT is still used in some 26 countries for malaria control. The amounts needed are dramatically less than in agriculture. It might take a ton or more DDT to dust a small cotton field, whereas it takes only two grams per square metre to treat the inside walls of a house. The DDT put on 1000 acres of cotton during a single growing season, for instance, would have protected a whole country like Guyana from malaria for a year.

Nevertheless, American, European and Canadian aid agencies, the World Bank, the United Nations and other international agencies have urged developing countries not to use DDT for any reason. 

The results? According to Professor Don Roberts, malaria cases have jumped 90 percent in Brazil, Bolivia and Peru in the past decade, and 80 percent in Guyana. Says Roberts: "Only Ecuador temporarily increased DDT use and - surprise! - malaria dropped by 60 percent." 

The fundamental problem is the lack of available and affordable alternatives to DDT. There is no effective anti-malarial vaccine. Scientists are trying to genetically modify mosquitoes so they no longer carry the malaria parasite, but effective results are a long way off. 

Other available anti-mosquito insecticides, such as synthetic pyrethroids, are not as effective and more expensive. In Indonesia, for example, DDT spraying was stopped in 1989 after 38 years of use. The next best insecticide was five times more expensive so the whole spraying programme faltered. 

When US Navy malariologist Kevin Baird went to the Menoreh Hills in Java, where Oka lived, to start a treatment drug study in 1995, it took him a month to track down 25 cases. Earlier this year he found 70 in one day. "The critical question is whereon this island crowded with more than 100 million people the outbreak will stop," he says. "Many people will probably die - history tells me that DDT could save them." 

No one is safe: Several environmental organisations want to abolish DDT entirely, claiming it is a threat to human health. For example, Clifton Curtis of the World-Wide Fund for Nature/World Wildlife Fund asserts, "As long as DDT exists anywhere on the globe, none of us is safe." 

But DDT's record speaks for itself. For years most Americans and Europeans ingested substantial amounts of DDT in food every day; the United States alone sprayed 70000 tons on crops every year for 20 years. Kids on bikes weaved in and out of the DDT clouds blown over the streets in countless American towns to control mosquitoes. Many millions of homes in Asia, Southern Africa and Latin America have been sprayed once or twice a year with DDT. Yet no adverse health effects have been reported. "Scientists have searched exhaustively , but found nothing substantial," says Mary Galinski, a molecular biologist at Emory University in Atlanta, Georgia, and president of Malaria Foundation International. 

Says Chris Curtis of the London School of Hygiene and Tropical Medicine: "There is no convincing evidence that DDT, as used indoors against malaria mosquitoes, has caused any harm to humans." 

While DDT opponents point to scientific studies indicating a danger to human health, the evidence, says Amir Attaran, of Harvard University, is vague and contradictory. For example, one US study found that women with higher incidences of DDT in their bodies were more likely to have breast cancer. But numerous other studies failed to come up with the same result. 

Nevertheless, DDT has been lumped with 11 other, persistent organic pollutants - `the dirty dozen' - now set. for reduction or elimination by international treaty at a meeting being held in Johannesburg from December 4 to 9, under the auspices of the UN Environmental Program. More than 110 countries and at least 50 Non-Governmental Organisations, will be taking part. Once agreed; the treaty will be legally binding worldwide. 

Open Letter: More than 400 medical doctors and scientists around the world have signed an open letter insisting that even if DDT is banned from agricultural use globally, exception must be made "for the life-saving use of DDT in malaria control". The letter notes that "at worst there are small health risks, and very large health benefits to DDT house spraying. We therefore have no doubt that it would be, a terrible error to eliminate DDT, which probably saves hundreds of thousands of lives a year from malaria." 

The treaty negotiators are starting to sit up and take notice of DDT's supporters. The final document to be hammered out in Johannesburg is likely to allow countries to continue using DDT for malaria control, until suitable alternatives are found. But even if DDT gets a reprieve, dangers remain. Warns Amir Attaran, who organised the letter, "A de facto ban is inevitable unless environmentalists from rich countries immediately stop putting, pressure on poor countries to give up DDT." 

The site of this, year's DDT showdown is ironic, because South Africa this year returned to using DDT for malaria control when levels of the disease surged. "As soon as we stopped using DDT it came back across the Mozambique border with horrific results," says Korea Gumede, a local environmental health officer. 

Says entomologist Rajendra Maharaj, who is in charge of South Africa's malaria control, "When thousands of human lives are at risk you, can't throw away something that works, just. because a few. people think it's evil.


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Last revised 9/16/2000