WHO Backs Use of DDT Against Malaria

WHO Backs Use of DDT Against Malaria

SEPTEMBER 15, 20063:41 PM ET JOANNE SILBERNER

The World Health Organization today announced a major policy change. It's actively backing the controversial pesticide DDT as a way to control malaria. Malaria kills about 1 million people a year, mainly children, and mainly in Africa, despite a decades-long effort to eradicate it. The WHO previously approved DDT for dealing with malaria, but didn't actively support it. While DDT repels or kills mosquitoes that carry the malaria parasite, it doesn't get much good press. In 1962, environmentalist Rachel Carson wrote a book,Silent Spring, about how it persists in the environment and affects not just insects but the whole food chain.

As activist Malvina Reynolds once sang, "It kills the bugs in the apple tree, I eat the pie and it's killing me. DDT on my brain, on my brain."

In the early 1960s, several developing countries had nearly wiped out malaria. After they stopped using DDT, malaria came raging back and other control methods have had only modest success. Which is why Arata Kochi, head of the WHO's antimalaria campaign, has made the move to bring back DDT. His major effort at a news conference Friday in Washington, D.C., was not so much to announce the change, but to deflect potential opposition from environmental groups. "We are asking these environmental groups to join the fight to save the lives of babies in Africa," Kochi said. "This is our call to them."

A number of major environmental groups support the limited use of DDT, such as spraying only inside of houses and huts once or twice a year. That type of use is supported by the Sierra Club and Environmental Defense, which was originally founded by scientists concerned about DDT. The limited application is also part of President Bush's new malaria initiative. But some environmental groups say spraying DDT will be harmful. Jay Feldman, executive director of a group called Beyond Pesticides, says using it is a war plan without an exit strategy. "WHO holds a lot of clout in the world health community and the fact that they're now changing policy and advocating use of DDT will have dramatic impact," Feldman says. "They announced today that they expect 85 percent receptivity, that is knocking on people's doors and convincing them — that's their language — to use DDT." Looking at the medical literature, he predicts harmful effects. "This is a chemical that has been studied and evaluated," Feldman says, "and over the years has been found to cause cancer, endocrine disruption, adversely affect the immune system and is very problematic from the standpoint that it is persistent." DDT collects "in fatty tissue and in the environment," he adds, and can also be passed on in breast milk.

But supporters of the new policy discount those studies and point to others showing it's safe. Richard Tren, member of a group called Africa Fighting Malaria, says that while there may be lab studies showing DDT could potentially cause cancer, no large studies show an actual increase in cancer in people. Some opponents say DDT will be diverted to more direct and more harmful agricultural use. Tren has watched indoor-spraying campaigns in Zambia.

"You're not seeing leakage into the environment," Tren says. "You're not seeing leakage into agriculture. What you are seeing are sharp dramatic reductions in malaria deaths and disease."

The field of malaria control has historically been dogged by problems with resistance. Each time scientists find a way to fight the parasite, the parasite finds a way to fight back. It has become resistant to most treatments, for example. And some mosquitoes have already adapted to tolerate DDT. The WHO's Kochi says resistance can be limited if DDT is used carefully, and only where it's likely to be effective.

Banned pesticide DDT may raise risk of Alzheimer's disease

BySarah Knapton,Science Correspondent 7:00AM GMT 28 Jan 2014

The pesticide DDT was banned in Britain nearly 30 years ago but researchers have discovered people with Alzheimer's disease have much higher levels in their bloodstream. Exposure to a pesticide banned in Britain in the 1980s may have increased the risk of developing Alzheimer’s disease decades later, scientists have warned. People who were found to have the highest levels of DDT in their system were four times more likely to have the degenerative disease. DDT (dichlorodiphenyltrichloroethane) was outlawed in Britain in 1986 and banned as a pesticide worldwide under the Stockholm Convention in 2001 after it was discovered to be dangerous to wildlife and the environment. But researchers found it is still present in bodily tissue decades later, broken down into the chemical compound DDE.

A study found that people suffering from Alzheimer’s disease had more than four times the level of DDE in their bloodstreams compared with those who did not have the disease. Report authors said the preliminary findings suggest the pesticide may contribute to the disease alongside other genetic risk factors. "This is one of the first studies identifying a strong environmental risk factor for Alzheimer's disease," says co-author Dr Allan Levey "The magnitude of the effect is strikingly large.” The team compared a group of 86 Alzheimer's patients with 79 people who did not have the disease. They found levels of DDE were four times higher in 74 of the Alzheimer's patients than those without the disease. Furthermore, patients who were carrying a gene that increases Alzheimers risk had even more severe cognitive impairment if they had been exposed to high levels of DDE. Previous studies of brain cells have shown that the compound increases levels of 'sticky' amyloid proteins which are thought to build up the damaging plaques associated with the disease.

The pesticide was developed during the Second World War and used extensively in agriculture from the 1940s onwards until it was banned. It may still be present illegally in imported fruits, vegetables and grains or in fish which have swum in contaminated rivers. Around 80 percent of Americans have traces of DDE in their system. It can take decades to work its way out of the body, having a half-life of between eight and ten years and can accumulate over time in the tissues as people age. “This observation could help explain why age is by far the largest risk factor for Alzheimer's disease,” said Levey. "The potentially huge public health impact of identifying an avoidable cause of Alzheimer's disease warrants more study - urgently."

The researchers suggest that doctors should test for DDE as an early predictor of the disease. “It is important because when it comes to diagnosing and treating this and other neurodegenerative diseases, the earlier someone is diagnosed, the more options there may be available,” said lead author Prof Jason Richardson. However experts and charities said the findings should be treated with caution until larger studies were carried out. Carol Brayne, professor of public health medicine at Cambridge University, said the research had produced a "very interesting result" but was too early to come to any conclusions about a possible link between DDT exposure and Alzheimer's. "I would be very, very cautious indeed about over-interpreting the results at this stage without confirmation from research based on stronger designs,” she said. Dr Simon Ridley, from the charity Alzheimer's Research UK, said: "It's important to note that this research relates to DDT, a pesticide that has not been used in the UK since the 1980s. "While this small study suggests a possible connection between DDT exposure and Alzheimer's, we don't know whether other factors may account for these results. “We can't conclude from these findings that pesticide exposure causes Alzheimer's, and much more research would be needed to confirm whether this particular pesticide may contribute to the disease.” Prof Alan Boobis, Professor of Biochemical Pharmacology, Imperial College London said the report should be ‘noted’ but warned that the findings were only preliminary and needed independent confirmation. “From the evidence they present we still don’t know whether DDT/DDE might be associated with Alzheimer’s disease through the much higher exposures that occurred several decades ago, or through the lower levels of exposure occurring now from residual environmental levels.” A spokesman for the Food Standards Agency said it was ‘extremely unlikely’ that DDT was still being used on food imported into Britain. “This American study does not give conclusive evidence that DDT or DDE are risk factors for Alzheimer’s disease. Further studies would be needed to explore this association further,” the spokesman added.

The study was published in JAMA Neurology