November 28, 2012 -- Updated 1524 GMT (2324 HKT)
People visit the grave of Palestinian leader Yasser Arafat the day after he was buried in Ramallah, West Bank, in 2004.
STORY HIGHLIGHTS
- Low concentrations of polonium are all around the environment
- Smokers are exposed to more polonium than nonsmokers because it's in tobacco
- Expert: Radiation poisoning from polonium-210 looks like the end stage of cancer
Arafat died in 2004. A
murder inquiry into his death was opened this year after high levels of
polonium-210 were found on Arafat's toothbrush, clothing and keffiyeh, the black-and-white headscarf he often wore.
Tawfiq Tirawi, head of
the Palestinian investigation committee, said forensic experts from
France, Switzerland and Russia took their own samples for independent
analysis.
Polonium-210 is not a
radioactive substance that emits gamma particles, which can travel
through walls at extremely high energies. Instead, as polonium-210
decays, it releases alpha particles, which can't even pass through a
piece of paper.
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But alpha particles are still dangerous. They travel short distances and retain a high amount of energy.
In nature, it takes about
138 days for half of a given quantity of polonium-210 to decay. But
because biological processes also work to eliminate the substance, it
takes about 50 days for half of it to disappear while inside the body, according to the Centers for Disease Control and Prevention (PDF).
Polonium-210 is a problem to humans only when it gets into the body. The International Atomic Energy Agency says that careful hand-washing and showering can eliminate most traces of this substance.
The radioactive substance
can enter body by eating or drinking contaminated things, breathing
contaminated air, or inhaling or ingesting bodily fluids from someone
contaminated with it. A wound can also become contaminated.
"Radiation, just like
with any toxic chemical, is related to dose," said Cham Dallas, a
professor and toxicologist at the University of Georgia's Institute for
Health Management and Mass Destruction Defense. "If you get a big dose,
then you'll die sooner."
And with polonium-210, a dangerous dose can be a matter of micrograms: smaller than a single speck of pepper, he said.
If you ingest polonium-210, about 50% to 90% of the substance will exit the body through feces, according to a fact sheet from Argonne National Laboratory (PDF).
What is left will enter the bloodstream. About 45% of polonium ingested
gets into the spleen, kidneys and liver, and 10% is deposited in the
bone marrow.
Radiation poisoning from polonium-210 looks like the end stage of cancer, Dallas said.
Liver and kidney damage
ensue, along with extreme nausea and severe headaches. Victims often
experience vomiting, diarrhea and hair loss. The alpha particles emitted
from the decaying substance get absorbed in the body, which is what
causes harm. Death may come in a matter of days, sometimes weeks.
There is no cure for
severe radiation poisoning, Dallas said. A few experimental treatments
are in the works for people who are able to stay on the edge of
potential survival, but they have not been approved by the U.S. Food and
Drug Administration.
Arafat died at age 75 at
a Paris military hospital after he suffered a brain hemorrhage and
slipped into a coma. Palestinian officials said in the days before his
death that Arafat had a blood disorder -- though they ruled out leukemia
-- and that he had digestive problems.
Rumors of poisoning
circulated at the time, but Palestinian officials denied them, and
then-Foreign Minister Nabil Sha'ath said he "totally" ruled them out.
Over the course of a
year, through natural sources and medical tests, the average American
gets an effective radiation dose of 6.2 millisieverts (mSv). A
potentially lethal dose of polonium-210 is 5 sieverts (Sv), Dallas said,
which is about 1,000 times more powerful than that average year's worth
of exposure.
Low concentrations of
polonium are all around the environment. Additionally, tobacco contains
polonium, and about twice as much of the radioactive substance has been
found in the ribs of smokers than non nonsmokers, according to the
Argonne report.
As for investigating a
polonium poisoning, there are instruments that can detect low
concentrations of polonium, Dallas said. But there's also a background
level of polonium found in nature, so if an alleged poisoning happened
many years ago, the remaining quantity in the body may be close to the
background level.
Another tricky part
about investigating a situation like this years after a potential
poisoning: It would be relatively easy for someone to contaminate
evidence after the fact with a small amount of the substance, Dallas
said.
So it's possible that
someone could have planted small amounts of polonium-210 in Arafat's
belongings, Dallas said. High levels were found by a team of Swiss
researchers at the Institut de Radiophysique.
Even through exhuming
the body, it's not clear that detection would be foolproof, Dallas said.
As time goes on, there's less and less of the radioactive substance
left, so it would be more and more difficult to tell how much
polonium-210 Arafat was exposed to, if any.
"It's going to be very
hard to determine whether polonium was ever introduced there," Dallas
said. "There will be a lot of dispute, I guess, depending on who is
incriminated by this."
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