MAPHUNGWANE, Swaziland -- Men in blue coveralls and white surgical masks began their annual trek into the countryside here last week. Methodically, they sprayed one home after another with a chemical most Americans probably thought long ago disappeared from use: DDT.
As villagers looked on, the workers used hand pumps to douse inside and outside walls with a fine mist. It is a yearly effort to repel and kill mosquitoes that carry malaria -- a disease that kills more than 1 million people a year, mostly children in sub-Saharan Africa.
This small kingdom near South Africa is one of just a handful of countries still using the notorious pesticide, banned in the United States in 1972 because of its toxic effect on wildlife.
But now DDT is poised for a big expansion in the developing world.
The influential World Health Organization plans to promote DDT as an inexpensive and effective tool against malaria. And the US government has boosted its budget twenty-fold for malarial insecticide spraying in Africa , to $20 million next year.
The new push for household spraying reflects a growing belief in some quarters that significant progress on malaria will require a third major front, alongside insecticide-treated bed nets and novel anti-malarial drugs.
No one proposes a return to the widespread agricultural use that decades ago severely harmed ecosystems in the United States and Europe. The results of such spraying were depicted in Rachel Carson's landmark 1962 book ``Silent Spring," which launched the modern environmental movement.
Advocates of household spraying say the comparatively minute amounts used in homes pose no known dangers. Any potential risk, they say, is far outweighed by DDT's potency against malaria, as was seen in the late 1940s and '50s when it helped eradicate the disease in the United States and other industrialized nations.
But environmental groups, while recognizing DDT's public health benefits, argue the chemical should be only a temporary measure. Greenpeace worries some inevitably will be diverted to farming uses and asserts that long term health effects on humans are still not known conclusively.
Some public health specialists, meanwhile, say DDT has a role but is no magic bullet. Mosquitoes can grow resistant to it; it might not work as well where malaria is found year-round, and effective house spraying requires organizational capacity severely lacking in places such as the Democratic Republic of Congo.
``You could have a container load of DDT in every district town in Congo and not save a single life," said Matthew Lynch, who directs the Global Program on Malaria at the Center on Communication Partnerships, a branch of the Johns Hopkins Bloomberg School of Public Health in Baltimore.
``We have to be looking at other tools we have," he said. ``What they didn't have in the '50s was insecticide-treated nets, and we have those now." Such nets are not treated with DDT.
WHO officials maintain that they are not minimizing the role of nets or treatment, just restoring proper emphasis on spraying -- a move some critics see as long overdue.