(CNN) -- Whether a radioactive substance called polonium-210 was involved in Yasser Arafat's death is under investigation. The body of the former Palestine Liberation Organization leader was exhumed Tuesday for this purpose and reburied.
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.
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."