Malaria fears over planned DDT ban
Sarah Boseley, Health Correspondent Monday August 30, 1999

More than 350 of the world's leading experts in malaria have signed an open letter of protest against plans for a global ban on the pesticide DDT, which they say will lead to millions more people dying in the developing world from the disease.

The 371 doctors, health economists and scientists, who include three Nobel laureates, warn of the consequences if the United Nations Environment Programme outlaws DDT along with a range of other pesticides known as persistent organic pollutants in a treaty to be negotiated next week.

Pushing for the ban are environmental groups, led by the World Wide Fund for Nature (WWF), which argues that alternatives will be found to combat malaria before the ban becomes effective in 2007. It says the deadline will concentrate minds.

But specialists in the disease say cases and deaths have already risen since DDT was outlawed in the western world in the 70s, in turn putting pressure on developing countries not to use it.

DDT, sprayed on the interior of homes, is a cheap and effective deterrent to the mosquito whose bite spreads the infection. Nothing yet developed works as well or is so easy to use, say the experts who signed the letter.

They lament the head-on clash between health experts and environmentalists, saying they too want rid of DDT but not until alternatives are in place.

The malaria experts accept DDT does environmental damage but accuse WWF of overstating the dangers to humans. While pesticide residues are found in breast milk, only one study - not two as WWF states on its website - has claimed DDT may be carcinogenic. The other six found no evidence DDT was implicated in breast cancer.

WWF says it is more concerned about the possible effects on the immune system, based on evidence of what DDT does to wildlife and lactation in women.

"While it is true that we don't know every last risk of using DDT, we know very well what the risk of malaria is - and on balance malaria is far, far more deadly than the worst that one could imagine about DDT," said Amir Attaran, director of the Malaria Project in Washington. He and the Malaria Foundation International organised the open letter.

"We are not in love with DDT. But the reality is that if you try to get rid of DDT without guaranteeing that money will be available for alternatives, you will kill people.

"If western countries like the US or UK want the environ mental benefit of a DDT ban, let them pay for it. Africa, Asia and South America have neither the technology nor money to research and implement alternatives to DDT. The rich countries do. For them to advocate a DDT ban while holding tight the purse-strings for those alternatives is obscene."

Among the eminent tropical medicine and public health specialists who have signed is Joshua Lederberg, a Nobel laureate in medicine who 30 years ago supported a ban on DDT but feels the threat of malaria today outweighs the evil of the pesticide. Two other Nobel laureates in medicine, Peter Doherty and Ferid Murad, and Wallace Peters, King Faisal International Prize laureate, a malariologist at the London School of Hygiene and Tropical Medicine, have also signed.

Other signatories include Wen Kilama, director of the African Malaria Vaccine Testing Network, a past president of the World Federation of Public Health Associations and chair of the World Health Organisation's expert group on DDT and malaria; Jeffrey Sachs, professor of development economics at Harvard; and Mary Galinski, professor of parasitology at Emory university in Atlanta, Georgia, and president of the Malaria Foundation International.

In their letter, the doctors and scientists say that although they agree DDT must one day be phased out, "we also believe that human life must not be endangered in reaching that goal. In our view, setting a deadline for the elimination of DDT - whether that deadline is in 2007 or some other date - unacceptably endangers health in countries with malaria".

They propose an immediate ban on agricultural use, which would be extended to malaria control only when western countries have put effective, affordable alternatives in place.

Prof Kilama, based in Tanzania, says that although DDT is cheap it is still not cheap enough for much of sub-Saharan Africa, where malaria is most deadly. The chances of the developed world investing more money to find other means of controlling malaria are slight, he feels.

Chris Curtis, a medical entomologist at the London School of Hygiene and Tropical Medicine, said: "DDT is the cheapest insecticide and what I feel will happen is - as has happened several times already - if they can't use DDT they won't feel they can afford to replace it, so they will simply cut down on the total area that gets vector [mosquito] control."

That has happened in India, which is reducing its use of DDT, he said, and in some Latin American countries.

WWF insists there is no risk of lives being lost if the global ban by 2007 is agreed. Clifton Curtis, director of its global toxic chemicals initiative, said: "We set an end-date as a motivational target. In our view, if you don't set a target you don't get decision-makers to focus on putting the money into the alternatives that are needed."

Green ideal clashes with third world need DDT row: Pesticide that damages the environment has saved millions of lives
Sarah Boseley, Health Correspondent Monday August 30, 1999

Malaria, a scourge of much of the developing world, kills some 2.7m people every year, most of them children under five and pregnant women, while up to 500m become ill, cannot work and need care.

A few decades ago, world health specialists talked of eradicating malaria. Now they talk only of trying to regain control. Malaria is endemic in more than half the world's countries. In the time it takes to name the disease, 10 children will contract it and begin fighting for their lives. One child in four who dies in Africa has succumbed to malaria.

DDT has a bad name. It is a pesticide that damages the environment and has been widely used in agriculture. Since Rachel Carson exposed its depredations in her book Silent Spring in 1962, environmentalists have campaigned to curb its use. In the west they have been successful.

But in the developing world it has saved millions of lives. Sprayed inside houses, it kills or more often repels the mosquitoes whose bite transmits malaria, and it is cheap. Specialists argue that it does not migrate out of doors, and if we lose it through a global ban in 2007 millions who could have been protected will die.

It is a head-on clash between first world environmentalists, who insist that DDT must go for the health of the planet and that alternatives will and must be found, and the malaria specialists, who say that until alternatives are in place that are as cheap and effective it would be catastrophic to ban it.

What will happen is clear, say the doctors. Under pressure from the west, which has no malaria, and amid worries about damage to human health from DDT, some developing nations have stopped or cut down on its use. Their sickness and death toll from malaria has risen. Effective alternatives have not been put in place, being too complex or, usually, too expensive.

The World Wide Fund for Nature, at the forefront of the campaign to ban DDT, talks about environmental management and biological control instead of pesticides, citing examples in India, Tanzania, Mexico and the Philippines.

But even these small-scale projects have run into difficulties - apart from in Tanzania, where bed nets are sprayed with synthetic pyrethroids. This sort of alternative might be acceptable to all, but pyrethroids are up to three times more expensive than DDT, although on bed nets they are used in smaller quantities, and projects to provide sprayed nets for large numbers of people are inevitably more complex than spraying house walls.

Don Roberts, professor of tropical public health at the uniformed university of health sciences in Bethesda, Maryland, cites what happened in Belize under pressure from the US to abandon DDT. "They stopped in the late 1980s to early 1990s, and malaria rates spiralled out of control, peaking in 1994. In 1995 they started using DDT again and have brought disease rates down three years in a row."

Two years ago, in the journal Emerging Infectious Diseases, he showed that Ecuador, which increased its DDT spraying while others cut down, was the only one of 11 malaria-endemic South American countries to have reduced its detection rate. With organised DDT house spraying, malaria in urban areas of the Amazon basin largely disappeared, but it is again becoming a big health problem.

Sense of balance
Professor Roberts does not like the confrontation with the environmental lobby. "We're all concerned about the environment," he said. "This is not limited to a few who want to get rid of DDT. But environmental issues have to be treated with a sense of balance." If this were the battle to eliminate DDT from agriculture, he would be applauding. Is it feasible to get alternative malarial control measures in place before 2007? "Absolutely not," he said.

Chris Curtis, a medical entomologist at the London School of Hygiene and Tropical Medicine, cited Madagascar. "The highlands eradicated malaria in the late 1950s and complacency set in. They stopped spraying. In the 1980s there was a huge epidemic which killed many thousands. They have now gone back to DDT and brought things back under control.

"In Venezuela there were 1m cases a year in the 1930s and lots of deaths. After the second world war they got into DDT immediately. In the north-central states malaria was eradicated in the 1940s and 1950s. Since the 1980s things have gone back quite a bit. There are about 24,000 cases a year in developed parts, in spite of pyrethroid spraying - much better than the 1930s and much worse than in the 1960s."

Roger Bate, director of the European Science and Environment Forum and a fellow of the Institute of Economic Affairs, pointed to areas of South Africa where malaria is once more on the rise since other pesticides were substituted for DDT. "It has gone from a couple of hundred cases a year to 15,000 in South Africa as a whole." Restricting DDT use was not the only factor, but it was part of the equation.

These numbers are tiny compared with the malaria toll in other parts of Africa. But South Africa once had it firmly under control. A paper by a consultant to the government there, Roger Tren, to be released by the IEA at the UN pesticides meeting next week, traces the virtual eradication of the disease in most parts after DDT's arrival. Measures to stop mosquitoes from breeding and then weekly spraying with pyrethroids reduced cases, but malaria was still a serious problem.

Transvaal experience
"After the introduction of DDT in the vector [mosquito] control programme in 1946, the number of cases in the then Transvaal declined to about one tenth of those reported in 1942-43," Tren writes. "In some areas DDT spraying was reduced and sometimes stopped because of the success it had in vector control."

Only two major South African provinces are now affected: Northern Province and Mpumalanga. Yet Tren's report (on http://www.iea.org.uk/env/malaria.htm) calculates that the cost of malaria to the economy in terms of people unable to work and needing hospital and home care is 4% of gross domestic product.

Bate said: "If the cost is so great to South Africa, where malaria is not endemic in 50-60% of the country, what is it like for the rest of Africa? Yet people I have spoken to involved in mosquito control in Botswana and Zimbabwe, where there are much higher levels of malaria, have no knowledge that this convention [on banning DDT] is taking place. The first they will know is when there is suddenly a ban by 2007. That is a major scandal when DDT will reduce the number of deaths significantly and save countries hundreds of millions of dollars."

Alternatives to DDT:
Synthetic pyrethroids
These pesticides are less toxic to wildlife and biodegrade far more efficiently than DDT. They are used to spray the inside of houses, like DDT, or more successfully to impregnate bed nets, which protect populations from malarial mosquito bites at night. They are three times as expensive as DDT, but less needs to be used in bed net spraying.

There are suggestions that malarial mosquitoes are becoming resistant to pyrethroids. WWF is not completely happy with them as an alternative to DDT and is calling for research on the "possible hazards" of pyrethroids to health.

Biological controls
Predators that eat mosquito larvae, such as fish like guppies or carp, are introduced to waters where mosquitoes breed. Other possibilities are parasitic wasps and natural bacteria. This method can pose a threat to biodiversity if the predator attacks indigenous wildlife, such as other fish or tadpoles.

Environmental management
The aim is to get rid of the stagnant waters where mosquitoes breed. Methods include drainage, filling in depressions and planting trees. A project cited by WWF in the Kheda district of Gujarat, India, covered water surfaces with polystyrene beads. But doubters point out that mosquitoes can breed in a muddy hoofprint.

Vaccines
There is work on several at the moment, but a vaccine is unlikely in the near future.