Polonium has a physical half-life of days. It emits alpha particles during its radioactive decay to lead The emitted alpha particles are highly energetic but they only have a very short range. In air, the range of an alpha particle is less than 4 centimetres, in human tissue e. Radioactive polonium poses a health hazard only if the radionuclide is taken up by the body incorporation.
This can occur. Owing to its natural occurrence, the annual average human intake via the pathways mentioned amounts to 58 Bq of polonium For smokers, the amount is increased by the natural polonium content in tobacco taken up by the lungs. Intermediate products of the uranium -radium decay series can be deposited on tobacco leaves or taken up by the roots of the tobacco plant.
Polonium results from the radioactive decay of these intermediate products. Therefore one cigarette contains about 9 to 15 mBq of polonium As polonium emits very energetic alpha radiation , it has a high radiotoxicity ; its chemical toxicity is orders of magnitude lower and is therefore not relevant for health assessment.
The remaining part is taken up by the blood in the gastrointestinal tract and is distributed - just like the polonium taken up by the lungs - throughout the body. In the process, the biological half-life of polonium in the body is 50 days.
The remainder is gradually eliminated in urine and faeces. Basically, the health effects of polonium depend on the amount taken up. The above-mentioned amounts of polonium taken up naturally are so small that they virtually do not have any health effects. And because the radiation has a very short range, it harms only nearby tissue. It cannot pass through skin, paper or clothes, for example. However, there was a theoretical risk that anyone who came into contact with the urine, faeces, sweat and tears of Mr Litvinenko could have ingested a small amount of the polonium.
It is used to eliminate static electricity in some industrial processes and as a power supply in nuclear weapons production, and in the oil industry. Russian lunar landers used it to keep the craft's instruments warm at night. But is not available in these industries in a form that makes it easy to use as a poison. Experts say that to poison someone, much larger amounts would be required and this would have to be man-made, perhaps from a particle accelerator or a nuclear reactor.
Although it occurs naturally in the environment, acquiring enough of it to kill would require individuals with expertise and connections. It would also need sophisticated lab facilities - and access to a nuclear reactor.
Only around g of polonium is made in nuclear reactors each year around the world. Alternatively, it could have been obtained from a commercial supplier but this would be near impossible without arousing suspicion.
Polonium can either be extracted from rocks containing radioactive uranium or separated chemically from the substance radium Production of polonium from radium would need sophisticated lab facilities because the latter substance produces dangerous levels of penetrating radiation. Because the alpha particles emitted by polonium cannot travel through skin or paper, it would be easy to smuggle a tiny amount into the country in a glass vial.
The substance is also very difficult to detect - in hospital tests and airport scanners - because it emits hardly any gamma radiation, which is what Geiger counters look for. Po is a radiation hazard only if it is taken into the body through breathing or eating or by entering a wound.
Much of Po is passed through feces, although the remaining amounts that enter the bloodstream can concentrate in organs such as the spleen, kidneys, and liver. If the exposure is significant but not extremely high, and if it occurs over a period of time, there is a long-term risk of cancer.
Exposure through inhaling Po, such as in cigarette smoking, can increase risk of lung cancer. Po is not a hazard to the outside of the body—neither polonium nor its radiation will go through unbroken skin or membranes.
Careful washing will remove most external traces of Po If you have specific concerns about your health related to Po exposure, you should contact your state health department for additional information on assessing your Po exposure or contamination. Some laboratories in the United States can conduct Po testing on urine, and your state health department can help you assess whether this is appropriate for you.
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