²¹⁰Po Symptoms and Diagnosis
The clinical manifestations of ²¹⁰Po poisoning are those of radiation sickness. Dose-dependent effects follow those of acute radiation syndrome (ARS). In non-lethal doses (<1 sievert), the individual is typically asymptomatic or has very mild clinical manifestations. Approximately 1–10% of individuals experience intermittent nausea and vomiting, and there may be a slight decrease in white blood cells after two to four weeks. Highly toxic doses (4.5 sieverts) cause nausea, vomiting, anorexia, and lethargy within hours, with a latent period of days to weeks before the onset of more severe symptoms. Loss of bone marrow, white blood cells, and platelets results in infection, bleeding, and bruising. Hair loss occurs in two to three weeks. If left untreated, 50% of individuals will die. At 10 sieverts, 100% of individuals will die within two weeks. At >20 sieverts, clinical manifestations occur almost instantly. Symptoms include projectile vomiting, explosive bloody diarrhea, headache, fainting, confusion, agitation, and burning sensations. Cardiovascular symptoms and neurological deficits ensue, followed by shock, seizures, coma, and death in two to three days.⁴

Ultimately, the damage caused by ²¹⁰Po alpha particles is due to total body irradiation. This results in extraction of electrons, disruption of cellular structure and activity, fragmentation of nuclei, chromosomal damage, as well as tumor induction. Some cells are more sensitive than others to these injuries, particularly bone marrow, lymphocytes, and enterocytes. Extremely high levels of ionizing radiation overwhelm the mechanisms of cell repair, and mass cell death occurs throughout the body, as seen in the case of Alexander Litvinenko.¹¹

Diagnosis of ²¹⁰Po poisoning is often delayed by the presence of non-specific gastrointestinal maladies that mimic food poisoning or the flu. Consequently, appropriate treatment is not always pursued at the onset of symptoms. Suspected exposures are confirmed through diagnostics. Fecal specimens are often used to determine exposure and, to a lesser extent, clearance rates. A more likely test for tracking the elimination rate of the isotope is a 24-hour urine assay. Quantification in urine cannot, however, predict the total systemic dose received or tissue concentrations. This is also true for fecal specimens.⁵ Analysis of blood is more useful for this purpose. A simple radiochemical and counting technique is used to measure the concentration of ²¹⁰Po in the sample, which correlates to total body burden. The concentration of the decay product (lead) is also quantifiable and aids in determination of total body concentration.¹²

Chronic low-dose exposure to ²¹⁰Po can likewise be determined from radiochemical analysis of urine. The results are then compared to previously established tolerance levels. This type of testing occurs when there is a risk of occupational exposure. Employees are tested monthly and the results used to direct modifications in usage or handling protocols.⁵

²¹⁰Po is quantifiable in hair samples. It is secreted by the sweat glands and then retained in the hair follicle. Like blood, urine, and fecal specimen analysis, alpha particles are counted radiochemically in order to determine total body burden and clearance rates. It is a practical method for chronic low-dose monitoring rather than acute poisoning. However, as is the case with urine and fecal analysis, concentrations cannot predict activity in specific tissues.⁹