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Fukushima Absorbed: How Plutonium Poisons the Body

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plutonium poisoning uptake in body cellsPlutonium has a half-life of about 24,000 years. And scientists have known for decades that even in small doses, it is highly toxic, leading to radiation illness, cancer and often to death. After the March nuclear disaster at the Fukushima Daiichi nuclear power plant in Japan, people the world over worried that plutonium poisoning might affect those near the compromised plant—and beyond.

Inhaled plutonium can land in the lungs, where it can lead to cancer, but it—and any that is ingested—can also find its way into the blood stream where it is slowly absorbed into the body.

New details about this toxic process are now emerging. "Plutonium is a toxic synthetic element with no natural biological functions," Mark Jensen, of the Argonne National Laboratory, and his colleagues wrote in a new paper, published online June 26 in Nature Chemical Biology (Scientific American is part of Nature Publishing Group). Not only is it useless to the body, "it is strongly retained by humans when ingested," primarily lodging in bone and liver cells, where it can release harmful alpha radiation.

But just how the body absorbed this toxic element remained a matter of speculation.

Scientists had noticed that the most prevalent plutonium ion (Pu 4+) had some similarities to more common metal ions, including iron (Fe 3+), which has a slightly smaller atomic radius but a similar ratio of radius to charge.

Jensen and his team used small-angle x-ray scattering and synchrotron x-ray fluorescence microscopy to peer into rat adrenal gland cells that had been extracted and exposed to Pu 4+.

The researchers were able to see for the first time some of the "molecular mechanisms organisms use to distinguish between metal ions," they reported. Jensen and his team found that one of the receptors that is usually charged with bringing iron into cells(known as the transport protein serum transferrin, or Tf) was also transporting the plutonium ions. The pathway has two binding sites, and in order for it to cross into the cell, both need to be filled with an iron-like ion.

But the cellular pathway didn’t gobble up the plutonium and bring it into the cell wholesale. Only one of the two binding sites—the C lobe—would take on a plutonium ion. And in order for the transfer to take place, an iron ion needed to be locked into the protein’s other lobe, the N lobe. And "the differences between the two lobes restricted, but did not eliminate, cellular Pu uptake," the researchers noted. The transferrin even seemed to have a slight tendency to take up more iron ions than plutonium.

Given that the cellular pathways are already partly discriminating between plutonium and iron—and partially preferring the latter—the findings could help "enable new treatments for Pu poisoning," the researchers noted.

Current plutonium-exposure therapies address circulating plutonium but cannot disarm the ions that have already been taken up by the body’s cells and tissues. But future treatments could make use of the preference for iron—and the partial resistance to plutonium uptake—to develop targeted drugs for humans in case of future nuclear accidents or attacks.

Image courtesy of iStockphoto/narvikk

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  1. 1. sault 12:49 pm 06/27/2011

    This is good news. However, in a nuclear accident like Fukushima, the releases of radioactive Iodine, Ceasium, Strontium and Uranium will pose the greatest health risks as they are much more prevalent in nuclear fuel than Plutonium.

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  2. 2. jgrosay 3:36 pm 07/15/2011

    It seems that the technology exists to change long half-life radioactive elements into fast vanishing ones, just by putting them under some nuclear particles beam,that changes atoms; however the high energy and facilities costs involved in this approach make it unsuitable, and this will be good just for nuclear waste, that is controlled, not for nuclear spillings. This reminds the history of Aluminium, once a curiosity because of the high cost of electricity needed to produce it, and currently an everyday life product.

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  3. 3. Joffan 4:30 pm 07/22/2011

    While the research is interesting, the relevance to Fukusihma is spurious. There has effectively been no elevated levels of plutonium detected in the environment from the nuclear crisis at Fukushima Daiichi. The general evidence of no raised levels from extensive local samples undertaken is proof that there has been no significant plutonium release. It strikes me as a failure of good science writing to imply otherwise without closing the loop on your opening statements.

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  4. 4. Nickuru 2:45 pm 03/4/2012

    Plutonium is the most lethal element in the periodic table. Osmium, of similar chemical properties, would be next, followed by Mercury, then Beryllium and Lead. Compared to these, Arsenic, used for poisoning in the Middle Ages, is just an upset stomach.

    What is not clear is whether the reactors were using enriched Uranium technology or were Plutonium based Light Water Reactor Technology. The best appraoch to nuclear power is using the Liquid Salt Thorium Reactor technology. This is safe and cannot create a disaster like Chernobyl.

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  5. 5. Dr Mark R.StJ. Foreman 2:43 pm 03/18/2012

    While the plutonium release from the Fukushima event is thought to be very small, it is important to bear in mind that the vast majority of the plutonium in the MOX used in unit three is in the form of the very insoluble plutonium dioxide.

    If does not need to cross from the air side of the lungs into the body, instead it emits alpha particles which damage the lungs. As it is very insoluble plutonium dioxide particles can stay in the lungs for a very long time compared with the more soluble uranium dioxide.

    If swallowed then the plutonium dioxide is so inert against acid that it is unlikely to dissolve, it will be passed out in stool.

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