from the April 14, 2005 edition - http://www.csmonitor.com/2005/0414/p14s02-sten.html
Old culprit hits birds - maybe people
By
Mark Clayton | Staff writer of The Christian Science
Monitor
When R. Given Harper set out to understand why North America's
migratory birds were declining, he set a unique course. While
other researchers zeroed in on habitat loss as a key problem,
he decided, on a hunch, to look at an old culprit - the
pesticide DDT - and its specific effects on songbirds.
The results were intriguing. Traces of DDT and other
related chemicals were showing up in the birds. But the real
shock came when Dr. Harper, a biology professor at Illinois
Wesleyan University in Bloomington, compared his results with
DDT levels in nonmigrating songbirds. These year-round
residents of North America - including a who's who of birds
like the northern cardinal, black-capped chickadee, and
dark-eyed junco - had more kinds of chemicals and dramatically
higher levels of them than the migrating species.
Those are surprising results. Heavily restricted in the
United States since 1972 and a declining problem for eagles,
osprey, and other predatory birds, DDT continues to show up in
alarming levels in nonmigrating songbirds. Does that spell
trouble ahead for these still-healthy species? Are humans at
risk? No one knows. But one lesson seems clear: Beware of what
you put into the environment, because it can be
extraordinarily difficult to remove.
"These [findings] are reminders that our decisions are
going to affect us for decades," says Greg Butcher, a senior
scientist with the Audubon Society and author of a recent
"State of the Birds" report that showed many North American
species in decline. "There may not be a toxic effect that
kills birds at these levels. But it very well could affect
their embryonic development."
Harper's findings are puzzling partly because of their
geographical specificity. Some 18 species that reside
year-round in North America have roughly 1 to 10 parts per
million of DDT - 2 to 10 times the levels of those that
migrate to Latin America. Also, all 17 of the organochlorine
compounds that Harper tested for - chemical cousins to DDT -
appear in each of those nonmigrating species. In contrast, one
to five of the compounds were found in migrating birds.
Those are preliminary findings from a yet-to-be published
study, although they build upon Harper's decade of
peer-reviewed research on the same topic. His findings also
parallel Canadian and US research that show organochlorines
bioaccumulating in other North American bird species, experts
say.
"These birds are the canaries in the coal mine, warning us
about what's going on in our environment," says Theo Colborn,
coauthor of "Our Stolen Future," a 1996 book that focused on
developmental problems caused by pesticides and other man-made
chemicals.
Such conclusions are premature, say spokesmen for the
chlorine industry. They note that Harper's research has not
been peer-reviewed yet. "It would be a mistake to say, not
knowing the levels, how significant his findings are compared
to others," says Kip Howlett, executive director of the
Chlorine Chemistry Council (CCC), a trade association in
Arlington, Va. Since DDT was banned, bald eagles and several
other species have been rebounding, he says.
Just why North American songbirds that do not migrate have
high levels of metabolized DDT and other organochlorines in
their bodies remains a mystery, Harper says in a phone
interview.
One hypothesis: The US used far more DDT than Latin
America, so there may be a lot still lingering in the soil, he
says. About 1.4 billion pounds were used in the US from World
War II until 1972, the Environmental Protection Agency says.
Harper's findings suggest that any reintroduction of banned
chemicals could have "a more immediate and dramatic toxic
effect than we saw the first time around," Dr. Butcher says.
At least 50 countries ban DDT use although it is still
legally used for malaria control in 20 nations, experts say.
The US and other nations have also banned several related
organochlorine pesticides, such as chlordane and dieldrin.
Others, such as lindane and endosulfan, are still registered
for use.
So far, Harper's research has focused on detecting
organochlorine levels in birds, not on their effects. "We're
not certain of the specific impacts of these compounds on
birds," he says. "We suspect the presence of these pesticides
may at least play a part in the decline of neotropical
migrants and may cause trouble for some nonmigrants, too."
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.
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."
Birds on the brink
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
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