Air Date: Week of September 17, 1999
Living On Earth’s science commentator Janet Raloff speaks with host Steve Curwood about the negotiations concluded this week at the United Nations Environment Program’s third conference on persistent organic pollutants (or POPs). A particularly contentious point was the use of DDT to control malaria.
CURWOOD: On September 11, the United Nations Environment Program concluded their third conference on persistent organic pollutants, or POPs. As the name suggests, once these chemicals get into the environment, they stick around for a long time, even showing up in animal and human tissue thousands of miles from where they were first used. Conference participants attempted to develop an international treaty to eliminate the worst 12. Janet Raloff, senior editor at Science News and Living on Earth's science commentator, joins us now from Washington, D.C.Hi, Janet.
RALOFF: Hello, Steve.
CURWOOD: I understand that DDT was one of the more contentious points of the conference, as it's still being used around the world to fight malaria.
RALOFF: Right. And the major issue is that no one questions the toxicity of DDT. It's contributed to a host of wildlife problems from eggshell thinning in birds to a number of endocrine problems in wildlife, like those male alligators in Florida that appear to be females. The big fear has been that DDT might cause cancer, although the latest data suggest that it probably doesn't. But notwithstanding, DDT is certainly a threat to many forms of wildlife, and the problem is that many small countries with a raging malaria problem also find DDT to be an inexpensive and quite effective way of killing disease-carrying mosquitos.
CURWOOD: So malaria is still a big problem.
RALOFF: Oh, huge. The disease strikes people in more than 90 countries today. These are nations home to 40 percent of the world's people. Each year some 500 million people get malaria, and it kills 2.7 million people, mainly preschoolers. The problem's worse in Africa. There, up to 23 percent of infants are born with the parasite, and each day an average of 2,800 kids die from the disease in Africa, or roughly five percent of the continent's children.
CURWOOD: Where does DDT fit in?
RALOFF: Well, it's become the preferred pesticide for treating homes in many countries that suffer from diseases carried by mosquitos. And we're not just talking malaria here, but also sleeping sickness and river blindness. Typically, individuals spray the walls or floors of their homes, anyplace a mosquito might land. Now, when it's used in the home, they don't use the same kinds of concentrations that have traditionally been used in the past for agricultural applications, but it all adds up. More importantly, the DDT that's sprayed indoors doesn't stay indoors. One study's calculated that up to 80 percent of it can get out, where it begins leapfrogging around the globe. And some of the stuff that is leapfrogging continues to do so for decades. It turns out that U.S. cotton farmers, for instance, used DDT to kill boll weevils, for example. Much of it ended up in the soil, and now, 27 years after DDT was banned in our country, farm lands throughout the cotton belt are still releasing an estimated 100 tons of DDT or its breakdown products each year.
CURWOOD: So, what alternatives are there, then, to DDT?
RALOFF: Well, there are a host of other pesticides, such as the Malathion that was sprayed in New York this week to combat the encephalitis problem there. While these tend to be less toxic or less persistent than DDT, many of them are also much more expensive. The World Wildlife Fund also has been looking into a number of case studies to see what other kinds of approaches can be used, and in a report that was released at the POPs meeting last week, they showed that you could get substantial malaria control through very simple things, sometimes, like sleeping under pesticide-treated nets or eliminating breeding grounds for mosquitos. In some cases, they are considerably more costly, these alternative approaches, or more time-consuming than just spraying that old standby, DDT.
CURWOOD: Now, what about developing a vaccine?
RALOFF: Well, there's been plenty of talk about pharmaceutical options, and lots of activity. But vaccine development is very difficult. It takes an awful lot of time, often decades. And while this going on, thousands of children die from malaria each year.
CURWOOD: Wasn't there a lot of controversy about the deadline for DDT phase- out?
RALOFF: There sure was. The World Wildlife Fund spearheaded that effort to talk about a complete global phase-out by 2007. The target date was pretty arbitrary. They chose the date that Mexico had agreed to phase out its production and use of DDT. The tactic seems to have worked. What World Wildlife Fund had wanted was to get people talking about DDT and alternatives, and it did. However, it also raised the hackles of the malaria control community. In the end, the World Wildlife Fund backed down from that target date, and just got people to agree that they need an ultimate phase-out. When will be determined at some later date.
CURWOOD: So what's next?
RALOFF: Well, the parties meet again next March to iron out further details. The negotiations from that should result in a final treaty, or at least the language for that, being offered up to government officials next November.
CURWOOD: And we're going to eventually see DDT phased out, you think?
RALOFF: I think so. Right now, no one is digging in their heels about fighting POPs phase-outs for any of these compounds. It's just a matter of when.
CURWOOD: Thanks, Janet.
RALOFF: You're welcome, Steve.
CURWOOD: That was Janet Raloff, senior editor at Science News, and Living on Earth's science commentator.
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