Polonium-210 is a naturally occurring radioactive element that emits alpha particles, a form of radiation that is harmless outside the body but devastatingly toxic once ingested or inhaled. It exists in trace amounts nearly everywhere on Earth, from soil and air to seafood and drinking water, yet it gained worldwide notoriety in 2006 when it was used to assassinate the former Russian intelligence officer Alexander Litvinenko in London. The story of polonium-210 stretches from uranium ore deep underground to volcanic plumes, tobacco leaves, Arctic food chains, and Cold War weapons labs.
Where Polonium-210 Comes From
Polonium-210 is not manufactured in some secret facility and then released into the world. It forms continuously in nature as part of the uranium-238 decay chain, a long sequence of transformations that begins with uranium in the Earth’s crust and ends, after many intermediate steps, with stable lead. Polonium-210 and its parent isotope lead-210 are the final long-lived radioactive members of this chain.1PubMed. Polonium-210 and lead-210 in the terrestrial environment: a historical review The process that delivers them to the surface starts with radon-222, a radioactive gas that seeps out of rocks and soil. Radon decays in the atmosphere into a series of short-lived products that eventually become lead-210, which then slowly transforms into polonium-210 over months and years.
Volcanoes are another surprisingly large source. Volcanic gases are extremely rich in polonium-210, and normal volcanic activity injects more than 50,000 curies of it into the lower atmosphere each year, with volcanic explosions adding over 1,000 curies annually to the stratosphere. These volcanic emissions may account for roughly half of the total polonium-210 found in both the lower and upper atmosphere.2Journal of Geophysical Research: Oceans. Modification of the atmospheric polonium 210 to lead 210 ratio by volcanic emissions So even without any human activity, polonium-210 would blanket the planet in tiny amounts, deposited by rain, dust, and volcanic fallout.
Why Alpha Radiation Makes It So Dangerous Inside the Body
Polonium-210 is an alpha emitter. Alpha particles are relatively large and heavy compared to other forms of radiation. They cannot penetrate skin or even a sheet of paper. You could hold a sealed source of polonium-210 in your palm and walk away unharmed, because the alpha particles would stop at the dead outer layer of your skin. The danger flips entirely once polonium-210 gets inside your body through ingestion, inhalation, or a wound. At that point, every alpha particle slams into living cells at close range, shredding DNA and other molecular structures with extraordinary efficiency.
Because alpha particles deposit all their energy over a very short distance, polonium-210 delivers a concentrated dose to whatever tissue it lodges in. Weight for weight, it is roughly 250,000 times more toxic than hydrogen cyanide. A lethal amount is measured in micrograms, far too small to see, taste, or smell. The isotope has a half-life of about 138 days, meaning it decays relatively quickly, delivering its radiation dose in a compressed time frame rather than spreading it over years.3PubMed. 210Po in drinking water, its potential health effects, and inadequacy of the gross alpha activity MCL
What Happens to a Person Who Is Poisoned
When someone swallows or inhales a large enough quantity of polonium-210, the result is acute radiation syndrome. The pattern follows a grim sequence: first a prodromal phase with nausea, vomiting, loss of appetite, and dropping white blood cell counts. If the absorbed dose exceeds about 0.7 gray, this initial wave of symptoms can be followed by a deceptive latent phase during which the person feels somewhat better. Then the real damage sets in.4PubMed. Diagnosis and treatment of polonium poisoning
At moderate doses, the bone marrow is the primary target. Bone marrow failure means the body can no longer produce blood cells properly, leaving the person vulnerable to infection and uncontrolled bleeding. At higher doses, the gastrointestinal tract breaks down, and at extremely high doses the cardiovascular and central nervous systems are hit. The classic triad of polonium-210 poisoning is early vomiting, followed by hair loss, followed by bone marrow failure. Death from very high intakes can occur within about a month; lower but still lethal doses can kill over a longer period, possibly up to a year.5PubMed Central. Health risk evaluations for ingestion exposure of humans to polonium-210
The kidneys, liver, spleen, and lymph nodes also take severe damage because polonium-210 distributes widely through the bloodstream and concentrates in certain organs. In men, the testes are particularly vulnerable. For anyone who survives, full recovery can take many months.
The Litvinenko Assassination
The case that put polonium-210 into the public vocabulary was the poisoning of Alexander Litvinenko, a former officer of the Russian Federal Security Service who had become a vocal critic of the Kremlin after defecting to the United Kingdom. On November 1, 2006, Litvinenko ingested polonium-210, likely dissolved in tea during a meeting at a London hotel. He died 22 days later. Post-mortem tissue samples and urine and blood analyses confirmed massive amounts of polonium-210 in his body. His estimated intake was around 4 gigabecquerels, assuming about ten percent absorption from the gut to blood, and the resulting organ doses ranged from roughly 20 gray to over 100 gray, far beyond survivable levels.6PubMed. The polonium-210 poisoning of Mr Alexander Litvinenko
Autoradiography of Litvinenko’s hair revealed two distinct bands of polonium-210 activity, providing evidence that an earlier poisoning attempt had taken place in October 2006. That first attempt delivered roughly one-hundredth the dose of the November event, not enough to kill him but enough to leave a record in his growing hair shaft. The discovery of this earlier attempt was a forensic breakthrough, reconstructed from a biological timeline locked inside his hair.
The investigation also revealed widespread collateral contamination. Trace amounts of polonium-210 were found at multiple London locations Litvinenko had visited, on aircraft seats, and on people who had been near the suspected assassins. Medical teams tried to reduce the radiation burden in Litvinenko’s body using unithiol, a chelating agent designed to bind heavy metals and accelerate their excretion. It was only moderately effective at reducing his accumulated dose.7Journal of Radiological Protection. Collateral contamination concomitant to the polonium-210 poisoning of Mr Alexander Litvinenko The limited treatment options underscore a harsh reality: once a large dose of polonium-210 is absorbed into the bloodstream, medicine has few good tools to pull it back out.
Polonium-210 in Tobacco
One of the least-known facts about polonium-210 is that smokers inhale small but meaningful quantities of it with every cigarette. The contamination traces back to the phosphate fertilizers used to grow tobacco. These fertilizers are rich in radium-226, which decays into lead-210 and then polonium-210. Tobacco leaves are especially good at accumulating these isotopes because of tiny hair-like structures on their surface called trichomes. Lead-210 deposits on and within the leaves and continues decaying into polonium-210 over time.8PubMed Central. Polonium and lung cancer
When a cigarette burns, the polonium-210 is not destroyed. It vaporizes and then condenses onto the tiny smoke particles that a smoker inhales deep into the lungs. Over years of smoking, these alpha-emitting particles accumulate at the branch points of the bronchial airways, creating persistent localized “hot spots” of radiation exposure. Researchers have been studying this pathway since the 1960s, and some have argued that polonium-210 is a meaningful contributor to the elevated lung cancer risk in smokers, operating alongside the dozens of chemical carcinogens in tobacco smoke. The tobacco industry was aware of the issue for decades but pursued no publicly visible effort to reduce polonium content in its products.
Polonium-210 in the Ocean and on Your Plate
The marine environment is where polonium-210 really accumulates. The isotope has a strong affinity for biological tissue, and marine organisms concentrate it to remarkable levels above the surrounding seawater. Research spanning nearly five decades has shown that concentration factors range from about a thousand to over a million, depending on the species and the tissue.9PubMed. 210Po in the marine environment with emphasis on its behaviour within the biosphere The ratio of polonium-210 to its parent lead-210 tends to increase as you move up the food chain, which means organisms preferentially take up and retain polonium-210 over lead-210. In some cases this accumulation can amount to genuine biomagnification.
For people who eat seafood, this matters in a practical sense. A study of Korean coastal waters found polonium-210 activity concentrations in anchovy whole bodies ranging from 59 to 392 becquerels per kilogram, while fish muscle in other species was far lower, often below 6 becquerels per kilogram. The viscera of fish and shellfish consistently contained far higher concentrations than muscle, sometimes by three orders of magnitude. The average annual effective dose for an adult eating about 43 kilograms of seafood a year was estimated at 94 microsieverts, with shellfish responsible for roughly 40 to 70 percent of that.10PubMed. 210Po in the marine biota of Korean coastal waters and the effective dose from seafood consumption For context, 94 microsieverts is a small fraction of the roughly 2,400 microsieverts an average person receives from all natural background radiation in a year. You would not stop eating fish over this. But for populations that eat very large quantities of shellfish and organ meats from marine animals, the dose contribution from polonium-210 becomes more significant relative to other natural sources.
Terrestrial food chains concentrate polonium-210 too. In northern Canada, researchers traced the isotope through the lichen-caribou-wolf food chain. Lichens, which absorb airborne particles very efficiently, pick up lead-210 and polonium-210 from atmospheric deposition. Caribou eat the lichens and accumulate both isotopes, with bone concentrations markedly higher than in wolves. Wolves, in turn, retain more polonium-210 relative to what they eat than caribou do, meaning the predator is more efficient at absorbing it from its food.11Health Physics. Transfer of 210Po and 210Pb through the lichen-caribou-wolf food chain of northern Canada Indigenous communities that depend heavily on caribou as a food source may receive higher natural doses of polonium-210 than people eating a typical Western diet, though this has been more a subject of monitoring than of health alarm.
Polonium-210 in Drinking Water
Most tap water contains negligible amounts of polonium-210 because it binds tightly to aquifer sediments. However, certain geochemical conditions can liberate it into groundwater. Research on public drinking-water supplies from principal U.S. aquifers found that high polonium-210 levels (above 0.7 picocuries per liter) occurred in about 1.5 percent of samples, and these were concentrated almost entirely in semiconsolidated sediment aquifers along the Atlantic Coastal Plain.12Environmental Science & Technology. Occurrence and Geochemistry of Lead-210 and Polonium-210 Radionuclides in Public-Drinking-Water Supplies from Principal Aquifers of the United States The conditions that promote mobilization include low oxygen, high pH, and high sodium-to-chloride ratios. A high background level of radon in the aquifer, which you might expect to predict high polonium-210, was not actually the primary driver.
When the U.S. Environmental Protection Agency set its maximum contaminant level for gross alpha activity in drinking water in 2000, very little was known about how often polonium-210 showed up or what geochemistry controlled its release from sediments. Subsequent research has suggested it may not be as rare as regulators originally assumed.13PubMed. 210Po in drinking water, its potential health effects, and inadequacy of the gross alpha activity MCL The standard gross alpha test used for routine water monitoring may not catch polonium-210 effectively, because the isotope can volatilize during sample preparation. In other words, the current regulatory framework may undercount the very thing it was designed to screen for.
Industrial and Military Uses
Despite its toxicity, polonium-210 has had practical applications. Its intense alpha emission ionizes air molecules, which makes it useful for eliminating static electricity. Industrial static eliminators containing tiny sealed sources of polonium-210 have been used in settings like semiconductor manufacturing, photographic film production, and paper mills, where even a small static discharge could ruin materials or create a fire hazard. These devices work by creating a local cloud of ionized air that neutralizes surface charges on nearby objects.
The safety record is not spotless. An investigation of six static eliminators after a contamination incident at a commercial facility found that cracked and broken polonium-210 microspheres were being produced and incorporated into new devices. Even brand-new, unused devices were potential sources of contamination. Rough handling could trigger polonium-210 leakage, and the epoxy binder used to seal the microspheres showed significant degradation under ordinary environmental conditions, with solvents, heat, moisture, or vibration accelerating the breakdown.14Materials Characterization. Evaluation of Static Eliminators Containing Polonium-210 Because of the 138-day half-life, these devices need to be replaced regularly, and old ones must be returned for disposal rather than thrown in the trash.
The most dramatic use of polonium-210 was during the Manhattan Project. Researchers synthesized it by bombarding bismuth with neutrons inside nuclear reactors. The resulting polonium was used in the neutron-generating initiators of the atomic bombs dropped on Hiroshima and Nagasaki, where it served as the trigger that kicked off the fission chain reaction at precisely the right moment.15American Journal of Physics. Rousing the dragon: Polonium production for neutron generators in the Manhattan Project This application is the reason polonium-210 production capability has remained a proliferation concern. Any nation or group with access to a nuclear reactor and bismuth targets can, in principle, produce polonium-210.
Why It Is So Hard to Detect
Part of what makes polonium-210 an effective poison is that it is nearly invisible to standard radiation-detection equipment. Alpha particles do not travel far enough to escape the body in detectable quantities, so a Geiger counter held near a poisoned person would register nothing unusual. Unlike gamma-emitting isotopes, which broadcast their presence through walls and skin, polonium-210 keeps its radiation locked inside whatever medium contains it. This is why Litvinenko’s poisoning was not identified as a radiological event for weeks: doctors initially suspected thallium, a conventional heavy-metal poison.
Detecting polonium-210 in water, food, or biological samples typically requires alpha spectrometry, a laboratory technique that involves chemically separating the polonium from the sample matrix and then plating it onto a metal disk (usually silver) for counting. Researchers have refined methods using spontaneous deposition of polonium-210 onto silver disks, assessing detection limits according to international standards for ionizing radiation measurement uncertainty.16PubMed. Evaluation of uncertainty and detection limits in 210Pb and 210Po measurement in water by alpha spectrometry using 210Po spontaneous deposition onto a silver disk The technique is reliable but slow. Sample preparation and counting can take days to weeks, which is one reason polonium-210 poisoning is so difficult to diagnose in real time. By the time the laboratory confirms the isotope’s presence, irreversible damage may already be done.
Polonium-210 also does not show up on a standard toxicology screen. Hospitals do not routinely test for radioactive poisons. The clinical presentation, particularly in the early stages, mimics many other conditions: food poisoning, a gastrointestinal infection, or a reaction to chemotherapy drugs. Hair loss and falling blood counts eventually point toward radiation exposure, but that realization often comes late. In Litvinenko’s case, the correct diagnosis was made only in the final days of his life, after a specialist suggested testing for alpha emitters.
Producing Polonium-210 Today
Naturally occurring polonium-210 is extraordinarily scarce. It exists in uranium ore at concentrations of roughly one part in ten billion by weight. No one mines it. Commercially and militarily relevant quantities are produced artificially, almost always by irradiating bismuth-209 with neutrons inside a nuclear reactor. The bismuth absorbs a neutron and becomes bismuth-210, which then beta-decays into polonium-210 with a half-life of about five days. The resulting polonium is chemically separated from the bismuth target.
Russia has been the world’s primary commercial producer, with production historically centered at the Avangard facility in Sarov. Estimates from open sources have placed Russian annual production at around 85 grams, though exact figures are not publicly verified. That may sound trivially small, but given polonium-210’s extreme specific activity, 85 grams represents an enormous amount of radioactivity. Other countries with nuclear reactors have the theoretical capability to produce it but have generally not done so at commercial scale.
The combination of reactor-only production, the short half-life requiring constant resupply, and the difficulty of handling an intensely radioactive alpha emitter means that polonium-210 is one of the most tightly controlled radioactive materials in the world. The static-eliminator industry accounts for most of the legitimate civilian demand. The fact that it was used as an assassination weapon in a major Western capital raised pointed questions about how it was obtained and transported, questions that remain politically charged years later.