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Get rid of malaria, then DDT

Brendan O'Neill questions the increased restrictions on a life-saving insecticide

As the millennium approaches, we seem to be witnessing a second coming. Malaria, an ancient disease that was effectively controlled in the second half of the twentieth century, has enjoyed a comeback in recent years. According to the World Health Organisation there were between 300 and 500 million acute cases of malaria in 1998, and approximately 2.7 million deaths. In Africa alone, 3000 people - mainly children - die of malaria every day.

The steady rise in malaria cases since the mid-1990s has led to some shock headlines. 'Malaria is back with a vengeance' warned Johannesburg's Mail & Guardian in September 1997, pointing out that 'almost half the world's population is at risk, the existing drugs are losing their impact and the number of deaths is rising'. How has this happened?

Malaria had been kept in check since 1955, when the World Health Assembly, the governing body of the World Health Organisation, launched a programme to eradicate the disease. The insecticide DDT, which proved extremely successful against malaria-carrying mosquitoes, was sprayed on towns and crops throughout Africa, Asia and Latin America. According to the World Wide Fund for Nature, the DDT programme 'eradicated or dramatically reduced malaria in 37 countries, saving millions of lives'. Between 1948 and 1963, DDT reduced annual cases of malaria in Sri Lanka from 2.8 million to just 17.

But today, DDT is no longer available to many in the South. In the name of protecting wildlife and the environment, use of the insecticide has been severely curtailed and could soon be banned.

'DDT is in the class of chemicals labelled "persistent organic pollutants"', says Ellen Hickey of the Pesticide Action Network (PAN) based in America. 'It is toxic to fish and invertebrate species, somewhat toxic to birds, and non-acutely toxic to mammals.' PAN was set up to campaign against the use of pesticides and insecticides which harm the environment, and to call for more 'ecologically sound' methods of combating disease. 'We need disease control programmes that are effective and also safer for the environment', says Hickey.

According to anti-pesticide campaigners, DDT not only damages the environment but also poses a threat to people. 'It accumulates in the fat of all living things', Hickey argues. 'It can kill sperm, or certainly lower a man's sperm count, and is associated with reduced fertility in women. In some cases DDT has been linked to premature births and absorbed fetuses.' Hickey and other environmentalists say that they want to strike a balance between protecting the environment and protecting public health: 'Of course we cannot give up the fight against malaria, but we have to have a more long-term outlook on global biodiversity and how we are impacting on the environment.'

But there is still a lack of evidence that DDT has a profoundly detrimental impact on the environment, or that it causes lethal harm to people (see 'Malaria and the DDT story' by Kelvin Kemm in Environmental Health: third world problems, first world preoccupations). According to one authoritative study by malaria experts at the University of Health Sciences in America, 'use of [DDT] should not be abandoned unless its known detrimental health effects are greater than the effects of uncontrolled malaria on human health'. Even the World Wide Fund for Nature (WWF), one of the biggest supporters of a ban on DDT, admits that while there may be 'documented evidence' of some damage to the environment, there are only 'suspicions about hazards to human health'.

Despite the lack of hard facts, far-reaching measures have been taken to restrict the use of DDT. In 1979 the World Health Organisation (WHO) ruled that the insecticide could only be sprayed in individual households and not outside where it might damage the environment. By the 1990s, environmentalists had stepped up the campaign for a total ban on DDT. WWF argues that 'indoor house spraying of DDT [still] puts the chemical into the environment', and the Pesticide Action Network is 'working to stop the production, sale and use [of DDT]'.

In 1992 WHO adopted the Global Malaria Control Strategy, which called for the scaling down of 'DDT reliance' and for more emphasis on detecting and treating individual cases of malaria, rather than trying to eradicate the disease with insecticides. Germany has used its presidency of the European Union this year to back the demands for a ban on DDT, and it looks likely that a UN treaty in the coming months will finally implement such a ban. These measures have already had tragic consequences in the South: malaria has risen by more than 500 percent in some areas in the past two years.

Many environmentalists get around what they call 'the DDT dilemma' by playing down the causal link between the restrictions on DDT and the recent rise in malaria. 'There are many reasons for the rise in cases of malaria', says Hickey, pointing out that wars, natural disasters, human migrations and local climate changes are all factors when considering the resurgence of the disease. 'The aim to scale down DDT and replace it with viable alternatives is not the main factor.'

There is no doubt that social, political and climate changes in the South do have an impact on the incidence of malaria. Yet that does not alter the fact that the drastic reduction in the use of an effective counter to the disease has allowed malaria to flourish.

'Other factors do contribute to the resurgence of malaria', says Professor Donald Roberts of the Department of Preventive Medicines at the University of Health Sciences in America. 'But none equals the influence of the decreasing use of DDT and the decreases in the house-spray programmes.' Professor Roberts has carried out extensive studies into the resurgence of malaria, particularly in Latin America, and has concluded that banning DDT would jeopardise the health of 'hundreds of millions of people in malaria-endemic countries'.

Professor Roberts' report 'DDT, global strategies and a malaria control crisis in South America' delivered a body-blow to environmentalists. The report used regression models to compare and contrast the prevalence of malaria in Latin American countries which differed in their use of DDT.

Roberts and his colleagues found that Guyana, which sprayed no DDT between 1993 and 1995, under pressure from environmentalist campaigns, suffered an increase in incidence of malaria of nearly 80 percent. Bolivia, Paraguay and Peru, all of which stopped spraying DDT after 1993, had an increase in malaria cases of more than 90 percent. Brazil, Colombia and Venezuela, which lowered their DDT spray rates in the mid-1990s, in keeping with the new WHO Global Malaria Control Strategy, all experienced a rise in malaria of nearly 40 percent. Meanwhile, Ecuador, which refused to give in to pressure and actually increased its use of DDT after 1993, enjoyed more than a 60 percent decrease in cases of malaria. 'The report shows that growth in malaria incidence corresponds with changes in the global strategies for malaria control', says Professor Roberts. 'I would argue that there is clearly a causal link between decreased spraying of homes with DDT and increased malaria.'

Roberts agrees with environmentalists that DDT has some negative impact on the environment, and even that it may cause limited, non-lethal harm to people. But even assuming that the environmentalists are right and that DDT is mildly toxic to birds and fish and that it may, possibly, cause non-lethal harm to humans, surely that is a small price to pay for combating malaria?

This disease is one of the worst in the South. It is transmitted by mosquitoes which bite humans and suck their blood. If the mosquito is infected then thousands of threadlike parasites will enter the human bloodstream and head straight for the liver. Two weeks after the bite the liver cells burst, releasing hundreds of spores into the bloodstream, and the sufferer becomes extremely ill. It is when the spores eat the haemoglobin in the red blood cells that the sufferer often dies an agonising and feverish death. How can we not prioritise eradication of this disease over protecting 'fish and invertebrate species'?

'It's not that straightforward', says Ellen Hickey. 'We cannot have such a short-term approach. If we damage the environment now then everybody will suffer in the future, in health terms as well as in environmental terms.' Professor Roberts disagrees: 'We now have a situation where we are eliminating the best chemical we have for prevention of malaria, without even having a debate. The health of millions of people in malaria-endemic countries should be given greater consideration before we proceed with the present course of action.'

Roberts' solution sounds like a sensible one. The restrictions on DDT should be lifted immediately. The resurgence of a disease that was almost eradicated 30 years ago is a case study in the danger of putting concern for nature above concern for people.

Reproduced from LM issue 119, April 1999

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