DDT: Weapon of mass survival?

Once blamed for causing infertility, cancer and premature birth in humans, cutting down on wildlife and marine populations and polluting fresh water sources, dichlorodiphenyltrichloroethane (DDT), has lately been hailed as a “weapon of mass survival” in the fight against malaria, which has killed more people than any other disease known to mankind.

The lifting of the ban by the UN signals the end of the era in which it was generally felt that the developed world, complicit in all malaria deaths in developing countries due to the bickering over DDT, seemed to endorse the belief attributed to a USAID official that people in developing countries affected by malaria were “better dead than alive and riotously reproducing.”

Population control advocates in the 1960s are reported to have blamed DDT for increasing third world population, presumably leading to the lobby against the insecticide by groups that believed that there was no alternative to the overpopulation problem but to assure that up to 40 percent of the children in poor nations would die of malaria.

Despite WHO’s approval of the indoor use of DDT for controlling malaria-carrying mosquitoes, environmentalists and other critics still claim that exposure to the chemical at levels required for malaria control causes more pregnancy and infant deaths than it saves, even in the face of data from countries where DDT has been shown to far outweigh its alleged side effects.

DDT, described as the most intricately studied chemical in human history and the greatest public health tool of the 20th century, had been banned for 34 years after a US judge ruled, against a torrent of empirical scientific evidence, that it was not safe for humans and the environment.

WHO finally gave in to international pressure from interest groups and scientists who argued and proved that DDT had no negative side effects on humans and was a safe, affordable and reliable chemical for killing malaria carrying mosquitoes in all parts of the world.

This realisation and acceptance of the role of the insecticide, used for eradicating malaria in developed countries since it was produced in 1939, came after more than 100 million children in developing countries had died of malaria.

A top water biologist at the Zimbabwe National Water Authority, who declined to be named, said he remained cynical over the use of DDT in malaria control operations and in agriculture, saying the non-biodegradable insecticide was insolvent in water and would continue to have side effects on humans.

“Although DDT is relatively safe if used in correct quantities, it is insoluble in water and has properties that compromise the quality of semen in men, disrupt menstruation in women among other negative effects.”

Respected medical journal, The Lancet, reported in a review that although DDT is generally not toxic to human beings and was banned mainly for ecological reasons, research had shown that exposure to DDT at amounts needed in malaria control might cause premature birth and early weaning, reversing the benefits of reducing infant mortality from malaria.

“DDT might be useful in controlling malaria, but the evidence of its adverse effects on human health needs appropriate research on whether it achieves a favourable balance of risk versus benefit,” read The Lancet report.

Although recent studies have shown that children who have been exposed to DDT while in the womb have a greater chance to experience development problems, no direct links have been established between DDT and breast cancer in humans.

DDT had been banned in the United States of America and in other parts of the world in 1972, after scientific studies had established that it had long term negative effects on humans, with others claiming the non-biodegradable chemical, which is insolvent in water, killed fish and depleted bird and wildlife populations.

The Lancet published a review in which researchers blamed the World Bank for falsifying scientific information on malaria and reneging on its commitments in the fight against the disease in a review earlier this year.

After the banning of the chemical, the World Bank promised that it would spend between $200 and $300 million on the fight against malaria, but reneged on this promise and reduced its commitment to the fight, even as malaria claimed more lives with the ecological changes and floods in sub-Saharan Africa.

This feeling of betrayal by the developed world led to growing calls for the lifting of what stood out as the only hope in the battle against malaria, especially in developing countries, where the shortage of funds and resources hampers research and disease and control efforts.

Globally, malaria afflicts between 300 million and 500 million people every year, and WHO estimates that around 3 million people die of malaria and malaria-related illness every year. About 90% of these deaths occur in Africa, mostly to children under the age of 5.

Malaria’s economic impact on developing countries includes costs of health care, working days lost due to sickness, days lost in education, decreased productivity due to brain damage from cerebral malaria and loss of investment and tourism in countries with economies that are heavily dependent on tourism.

Uganda, South Africa, Zimbabwe, Kenya and other countries in sub-Saharan Africa have already endorsed DDT in their fight against malaria, and Uganda has said it will use the chemical to prevent 120,000 malaria deaths a year.

Malaria accounts for 10 per cent of the deaths caused by disease in Africa, and claims the same percentage of resources spent on controlling diseases. At least 69 per cent of the world’s malaria cases occur in Africa, India, Brazil and Mexico, and these regions have been desperately in need for a safe replacement of DDT.

The US Agency for International Development (USAID) reported in May, four months before the lifting of the ban on DDT by WHO, that it would fund the indoor spraying of DDT in Sub-Saharan Africa, where the malaria kills more than 2,8 million people annually, costing the region an estimated $12 billion in lost productivity.

DDT was first synthesized by German chemist Othmar Zeidler in 1874 and then produced as an insecticide for controlling flies, aphids, mosquitoes, walking sticks and Colorado potato beetles by Dr. Paul M’ller in 1939. M’ller went on to win the Nobel Prize in 1948 for his work on DDT.

As countries in the region adopt the insecticide, it is widely agreed that DDT could be an affordable and effective public-health intervention with long-lasting effects, but one that should be applied responsibly to minimise any negative impact it might have on the environment.

September 2006
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