Old culprit hits birds - maybe people
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The DDT and six other organochlorine compounds that Harper found in the birds are related to chemicals banned by international treaty. The treaty, the Stockholm Convention, labels them as "persistent organic pollutants," or POPs, because they remain in animals, humans, and the environment for years. They also tend to evaporate in warm climates and blow on the winds to cold, northern reaches, where they concentrate. Pesticides like DDT and lindane show up in high concentrations in Inuit populations, seals, and polar bears, Dr. Colborn notes.Skip to next paragraph
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Early next month in Uruguay, more than 50 nations will discuss rules for adding new chemicals to the POPs ban treaty, which came into force last year.
The US chemical industry and President Bush hailed the treaty, and the US signed it in 2001. Yet legislation to enact it is currently stymied in Congress. Legislators disagree whether to include tough language that would automatically ban new chemicals in the US as they are added to the treaty list.
But until the US ratifies the treaty, it will only be an observer and not permitted to vote on the new mechanism or on any chemicals that may be nominated for addition to the list, observers say.
"We support the treaty itself and its implementation into US law," says Michael Walls, managing director of the American Chemistry Council, an industry association in Arlington, Va. "We've been encouraging the Bush administration and Congress to move quickly.... The unfortunate consequences of not having ratified the treaty is that the US won't have a vote at the first meeting."
One of the first chemicals that some say could be nominated for addition to the list is lindane, which Harper found in most of his songbirds in North America. It's a pesticide used to treat seeds and also an ingredient in shampoo to combat head lice.
In California, where lindane-based shampoo is banned, a state agency reported one rinsing of lindane shampoo could contaminate 6 million gallons of water, notes Kristin Schafer, program coordinator at Pesticide Action Network, an environmental group in San Francisco. New York is also weighing a ban, she says.
A major reason scientists worry about DDT and other organochlorines is that they are powerful "endocrine disruptors," whose effects on humans and wildlife are little known. Colborn and Harper charge that such chemicals can, even in tiny amounts in the body, interfere with embryo development and harm reproduction and survival.
"Every one of these chemicals has an endocrine disruptor effect that can harm the development of the embryo by interfering with hormones," Colborn says. She says there's growing evidence of a link between organochlorines and learning disabilities and human disorders, which have multiplied since such chemicals came into common use.
But the issue is dosage, not detection, counters the American Council on Science and Health, a nonprofit group advised by scientists and others and created to counter activists' claims. "Current levels of environmental chemicals in the general population are well below those considered to be associated with adverse effects and thus do not pose a risk to public health," it concluded in a 2003 book.
And regulation of current pesticides already takes into account bioaccumulation, writes a spokesman for CropLife America, a trade group representing pesticide manufacturers, in an e-mail.
Deeper studies may be needed to settle the issue fully. Although pesticides have been thoroughly tested, the human hormone system is so complex that there are no generally accepted methods to screen chemicals for adverse health effects, the CCC website says.
Glenn Wiser, a senior attorney with the Center for International Environmental Law, disagrees: "The lesson from the songbirds is that DDT and other POPs are still used worldwide and are still a problem."
Around the world, 1 in every 8 bird species is threatened. Nearly 180 of them are critically endangered - from the California condor to the Madagascar fish-eagle. Here's a look at birds that face an extremely high risk of extinction in the wild:
• Africa (31 species critically endangered): Reports suggest that the Somali thrush is losing its habitat in mountaintop woodlands of northern Somalia.
• Asia (44 species): The sociable lapwing, which breeds in Russia and Kazakhstan and winters as far away as Sudan and India, is rapidly declining for reasons not fully understood.
• Europe (6 species): Zino's petrel breeds on just five mountain cliffs in Portugal but may be stable.
• North America (17 species): Bachman's warbler may be extinct, but patches of habitat, including South Carolina swampland, need to be searched.
Source: BirdLife International