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MIGRATING ducks and stray tumbleweeds have been contaminated with
radioactivity after landing fleetingly in ponds of waste water at a nuclear
facility in the US. The news raises questions about the practice of leaving such
ponds open to the elements.

In the mid-1990s, staff at the Idaho National Engineering and Environmental
Laboratory (INEEL) realised that tumbleweeds were able to 鈥渂low into waste-water
ponds, and wash up on shore and blow out again鈥�, says Ronald Warren, an
independent environmental monitoring expert who is contracted to scrutinise
radioactivity at INEEL. 鈥淭he tumbleweeds blew against the [2-metre high] fence
where they built up, forming a ramp other weeds could climb over,鈥� he says.

In a two-year study, Warren and his colleagues measured how much radiation
the tumbleweeds took with them from two waste ponds near a US Navy test reactor.
The team found that the tumbleweeds, which were mostly Russian thistle (
Salsola kali), carried out a total of 66 megabecquerels of radiation and
spread it over a 32-hectare area.

鈥淭he activity from those tumbleweeds made a relatively small, around 15 per
cent, increase to the activity due to global fallout in that area,鈥� he says.
Risk to humans is slight since the nearest house is 42 kilometres away and the
tumbleweeds travelled less than a kilometre.

Nonetheless, INEEL has taken action. 鈥淭hey鈥檝e now made the fence higher and
they go out and collect tumbleweeds and bury them,鈥� Warren says. Growing shrubs
near the ponds has also hampered the tumbleweed.

But birdlife is not so easily thwarted. In research yet to be published,
Warren says he has found 21 species of migratory duck that fly over
INEEL鈥攁nd some take a rest stop in the waste ponds. Warren says the duck鈥檚
radiation levels wouldn鈥檛 harm you, even if you ate a whole one. 鈥淭he maximum
radiation dose you鈥檇 get would be less than you鈥檇 get from a dental X-ray,鈥� he
says.

This does not reassure everyone. 鈥淚 haven鈥檛 a clue why they don鈥檛 cover the
ponds with any kind of net,鈥� says Margaret Stewart of the Snake River Alliance,
an anti-nuclear pressure group based in Idaho. 鈥淚t seems like a sensible kind of
thing to do if you鈥檙e trying to keep birds out.鈥� But an INEEL spokesman
maintains that radionuclide concentrations are so low in the ponds that birds
would face more risk of death from entanglement in netting.

Britain had its own problem with birds in 1999, when researchers found that
pigeons visiting contaminated buildings at the Sellafield nuclear complex were
concentrating radioactivity in their droppings in the nearby village of
Seascale.