Bad Blood

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Nairobi-based physician Paul Saoke is chairman of Kenya's DDT and Malaria Expert Committee on implementation of the Stockholm Convention and head of the country's chapter of the international health advocacy group Physicians for Social Responsibility. He has his eye on another serious concern about the toxin: its effects on human health. I first met Saoke in April 2007 at the POPs conference in Dakar. The man has an impish grin and a way with a crowd. To an audience of buttoned-up delegates representing all sides of the POPs question and all corners of the globe, he introduced a presentation on the health risks of DDT with an anecdote from his childhood.

Born in 1961, Saoke grew up in an area near Mbita that used to be "fumigated," as he put it. Through the 1960s and 1970s DDT periodically rained down to control agricultural pests and to combat mosquitoes, ticks, and tsetse flies. Saoke and his boyhood pals would often peel off their clothes to swim in Lake Victoria, and as they grew older they dared one another to leap off a high, rocky ledge into the water. Some of the kids were afraid to jump. So, in a kind of rough-and-tumble, let's-see-what-you're-made-of scramble, they would reach between one another's legs to check. Lo and behold, Saoke recalled to the group of fidgeting dignitaries, by this crude measure a number of the boys were not made of much. His serious point: according to a growing body of evidence, cryptorchidism -- undescended testes -- and other genital malformations can result from in utero exposure to DDT.

Saoke now lives in Nairobi with his wife, a neonatologist, and their three children. Walking on the streets of the capital, or grabbing lunch in a restaurant, he appeared to know just about everyone he meets, from the shoeshine man to the government minister. Over the course of several conversations, Saoke recounted to me the parliamentary machinations by which Kenya very nearly changed course and resumed spraying DDT for disease-vector control. The pro-DDT lobby was powerful, and while Saoke was not alone in raising opposition, it's easy to imagine he was among the more outspoken. He's wary of the influence that global corporate interests can bring to bear on Kenyan national policy. His particular concern is that the international chemicals industry and its promoters are using the millions of African babies they claim DDT can save as a "human shield" behind which to begin rehabilitating an industry with a long history of lousy PR.

In the end, Saoke concedes, it was not concern about the health effects of DDT that carried the day; it was fears about lost trade. The European Union tests agricultural imports for traces of banned chemicals, and it refuses goods that test positive. DDT was not being considered for agricultural use, but wind and water can carry the stuff; moreover, in Kenya, as in most African countries, once the chemical is in distribution it is nearly impossible to monitor and control the manner in which it's deployed (a vexing problem for the Stockholm Convention). The Kenyan government was not about to adopt a policy that could threaten exports. This was fine with Saoke, but it is the health issues that consume him. 

 Some say that these concerns are based on purely anecdotal evidence. But the science has been accumulating for years, and policy makers are beginning to take note. At a high-level Stockholm Convention meeting in October 2007, for example, convened to discuss plans for alternatives to DDT in the fight against malaria, one agenda item read: "New information on DDT toxicity -- is it time to press the panic button?"

A growing number of peer-reviewed studies suggest links between DDT exposure and a range of ills, such as breast and liver cancer, neurological and developmental abnormalities, and a variety of hormonal effects. Some of these conditions may not manifest themselves for years, but others may take a more immediate toll.

DDT can interfere with the feedback loop in the pituitary gland, which releases the milk-producing hormone prolactin. Studies show that exposure to DDT at critical points in pregnancy or just after childbirth can reduce the output of breast milk, or even dry it up. In such instances the mother will turn to formula, which is expensive.And in Africa formula feeding often leads to another death sentence for babies: diarrhea (infants have no immunity to the microbes that abound in contaminated drinking water throughout much of the continent). Here, then, exposure to DDT may cause as swift and bleak an outcome as exposure to a mosquito.

Many of today's DDT promoters concede that the toxin cannot eliminate malaria all by itself. They endorse the idea of Integrated Vector Management (IVM), which combines indoor house spraying with bed nets, larvicides, and whatever other control measures may be applicable in a given area. But they insist that DDT can and should be part of a comprehensive, multifaceted response.

They correctly point out that the amount of DDT necessary to keep mosquitoes from biting inside a house is far less than the amount required for agricultural pest control. However, according to Gina Solomon, associate clinical professor of medicine at the University of California at San Francisco and a senior scientist with NRDC, "There's not much reassurance in that argument. These applications occur where people live and therefore involve direct human exposures, so there's still a human health concern." Moreover, she says, "Hormone concentrations are minuscule, by definition. That's the entire point." Hormones are chemical signals released by glands at varying intervals to initiate and modulate an organism's development, and there is compelling evidence that DDT and its metabolite DDE can interfere with that delicate process. Encountered at the wrong time, at a critical moment in the growth of a fetus or a baby, the smallest amount may disrupt the messages that hormones exist to convey (see "Bad Chemistry," OnEarth, Winter 2006).

In Africa, airtight longitudinal health studies of any kind are extremely difficult to execute, given the continent's ramshackle health care infrastructure, its migratory populations, and the sheer multiplicity of medical issues that challenge any long-term attempt to isolate and track the factors involved in disease. But a crowded spectrum of reports, studies, and anecdotes like Paul Saoke's link DDT exposure to low birth weight, increased miscarriages, impaired neural development in children, low sperm count in men, and a long list of other ailments.

Continued...