ASSOCIATION OF 210Po CONTENT IN URINE WITH CONCENTRATION OF 222Rn IN DWELLINGS.

Effect of indoor radon concentrations higher than 500 Bq m-3 in dwellings on excretion of 210Po was studied in 28 volunteers. The study was further augmented by following eight individuals from the group for 5 months at 1-month intervals. Association between 222Rn concentration in homes and 210Po excretion was found when the dataset containing values of the studied 27 subjects was combined with data on 40 Prague inhabitants from the previous study. Sources of uncertainties involved in the analysis are discussed.

Natural levels of polonium-210 in urine.

This paper presents a review and analysis of available data on background levels of polonium-210 in urine. It was established that 819 measurements could be considered to correspond to natural background levels, excluding a large number of values identified by the original investigators as potentially due to an artificial source or due to recognised enhancement of dietary intake. Almost 550 measurements were extracted from studies reported in the literature; additional measurements were contributions of previously unpublished data by authors of more recent papers. The majority of the measurements (462) were single samples from individuals but 357 values were repeat measurements provided by 81 subjects and for these the mean value for each subject was used. The final dataset consisted of measurements from 543 individuals. Analysis of the measurements confirmed the data was log normally distributed with mean and median values of 15.5 mBq d-1 and 11 mBq d-1 in urine samples, respectively. While the overall range was from 0.3-111 mBq d-1, almost 90% of the measurements were less than 30 mBq d-1, 95% were less than 45 mBq d-1, and 99% less than 70 mBq d-1. Separate analysis of data for smokers and non-smokers suggested a modest increase in smokers of up to 5 mBq d-1. Perhaps reflecting the importance of dietary differences such as seafood consumption, a marked difference between countries was observed in the range of results. While for most countries, 95% or more of results were below 30 mBq d-1, China and Italy were notable exceptions, with greater than 20% of values above this level.

Variation of ²¹°Po daily urinary excretion for male subjects at environmental level.

(210)Po was determined in 24-h urine of seven healthy males from Prague, Czech Republic, for ten consecutive days. The results show that for each volunteer, the urinary excretion of (210)Po changed only little from day to day in the studied time period. For two volunteers, the difference in the daily excreted (210)Po activity for two consecutive days was not significant, given the 95% confidence interval (two sigma) of the activity measurements. The same is valid for the excretion data of the other volunteers, except for some days where the differences were slightly higher. The range of daily urinary excretion of (210)Po of each volunteer in the studied time period was quite narrow. Among the volunteers, the maximum daily urinary excretion value of (210)Po was at most about a factor of 2.5 higher than the lowest excretion value. An attempt to explain the observed small inter-individual variability of (210)Po excretion in daily urine is made.

Determination of (210)Po in drinking water and urine samples using copper sulfide microprecipitation.

Polonium-210 ((210)Po) can be rapidly determined in drinking water and urine samples by alpha spectrometry using copper sulfide (CuS) microprecipitation. For drinking water, Po in 10 mL samples was directly coprecipitated onto the filter for alpha counting without any purification. For urine, 10 mL of sample was heated, oxidized with KBrO3 for a short time (∼5 min), and subsequently centrifuged to remove the suspended organic matter. The CuS microprecipitation was then applied to the supernatant. Large batches of samples can be prepared using this technique with high recoveries (∼85%). The figures of merit of the methods were determined, and the developed methods fulfill the requirements for emergency and routine radioassays. The efficiency and reliability of the procedures were confirmed using spiked samples.

Excretion rates of 210Po and 210Pb in Prague inhabitants.

Excretion rates of (210)Po and (210)Pb in the urine were investigated in 40 healthy inhabitants of Prague (22 males, 18 females, age: 23-70 y, non-smokers). In 20 inhabitants the excretion rates of (210)Po and (210)Pb in faeces were also studied. The mean urinary excretion rates of (210)Po and (210)Pb were 4.1 and 6.0 mBq d(-1), respectively. It was demonstrated, statistically, that the urinary excretion rates of (210)Po and (210)Pb are higher in men than those in women. The highest excretion rates of (210)Po and (210)Pb found in the participants were 10.8 and 16.6 mBq d(-1), respectively. The mean activity ratio of (210)Po/(210)Pb in the urine was 0.73. The mean excretion rates of (210)Po and (210)Pb in faeces were 56.5 and 54.6 mBq d(-1). The mean activity ratio of (210)Po/(210)Pb in faeces was 1.0.

Epidemiology of internal contamination with polonium-210 in the London incident, 2006.

BACKGROUND: More than 700 UK residents were tested for possible contamination with polonium-210 ((210)Po) following the alleged poisoning of Mr Alexander Litvinenko in London in November 2006. This paper describes the epidemiology of internal contamination with the radionuclide in this group. METHODS: 11 locations in London had been identified as sufficiently environmentally contaminated with (210)Po to present a health risk to people associated with them. Public health consultant teams identified individuals at risk and offered 24-h urine testing for (210)Po excretion. Prevalence of internal contamination was estimated, and a retrospective cohort analysis was completed for each location. RESULTS: Overall 139 individuals (prevalence 0.19 (95% CI 0.13 to 0.27)) showed evidence of internal contamination with (210)Po, although none with uptakes likely to cause adverse health effects. Substantial prevalence was seen among specific hotel service staff, customers, staff and other users of a hotel bar, office and hospital staff, staff of one restaurant and residents of and visitors to the family home. Increased risks of contamination were seen for a hotel bar in association with occupational, behavioural and temporal factors. Occupational and guest exposure to contaminated areas of hotels were also associated with increased contamination risk. Nurses were more likely to become contaminated than other staff involved in direct patient care. CONCLUSIONS: Uptake of trace amounts of radionuclide in this incident was frequent. Occupational, behavioural and temporal gradients in contamination risk were mostly consistent with a priori site risk assessments. Utility of the investigation methods and findings for future accidental or deliberate environmental contamination incidents are discussed.

Natural variation in 210Po and 210Pb activity concentrations in the urine of Finnish population groups.

A study to determine activity concentrations of (210)Pb and (210)Po in the urine of certain Finnish population groups was conducted, to investigate the variation in natural background level of urinary excretion. The study participants were divided into three groups mainly based on their diet. The first group comprised recreational fishermen and the second group represented people consuming more reindeer meat than an average Finn, while people using drinking water with very high activity concentrations of (210)Po were selected for the third group. The fourth group was a control group. The mean urinary excretion of (210)Po in groups 1 and 2 was 73 and 100 mBq d(-1), respectively. These values were higher than the value of the control group (20 mBq d(-1)) and the mean values reported in the literature. The mean daily urinary excretion of (210)Pb in groups 1 and 2, 70 and 52 mBq d(-1), was also slightly higher than that in the control group (32 mBq d(-1)). In contrast, the excretion rates of both (210)Po and (210)Pb for the members of group 3 were one to two orders of magnitude higher than those reported in the literature. This was clearly due to the elevated levels of natural radionuclides in their drinking water. The present study demonstrates the importance of possessing good knowledge of the background levels, in order to allow the determination of the additional exposure due, for example, to the malevolent use of radiation.

Prevalence of and risks for internal contamination among hospital staff caring for a patient contaminated with a fatal dose of polonium-210.

BACKGROUND: Alexander Litvinenko died on November 23, 2006, from acute radiation sickness syndrome caused by ingestion of polonium-210 (²¹°Po). OBJECTIVE: The objective was to assess the prevalence of and risk factors for internal contamination with ²¹°Po in healthcare workers (HCWs) caring for the contaminated patient. SETTING: Hospital. PARTICIPANTS: HCWs who had direct contact with the patient. METHODS: We interviewed 43 HCWs and enquired about their activities and use of personal protective equipment (PPE). Internal contamination was defined as urinary ²¹°Po excretion above 20 mBq within 24 hours. We obtained risk ratios (RRs) for internal contamination using Poisson regression. RESULTS: Thirty-seven HCWs (86%) responded, and 8 (22%) showed evidence of internal contamination, all at very low levels that were unlikely to cause adverse health outcomes. Daily care of the patient (washing and toileting the patient) was the main risk factor (RR, 3.6 [95% confidence interval (CI), 1.1-11.6]). In contrast, planned invasive procedures were not associated with a higher risk. There was some evidence of a higher risk associated with handling blood samples (RR, 3.5 [95% CI, 0.8-15.6]) and changing urine bags and/or collecting urine samples (RR, 2.7 [95% CI, 0.8-9.5]). There was also some evidence that those who reported not always using standard PPE were at higher risk than were others (RR, 2.5 [95% CI, 0.8-8.1]). CONCLUSIONS: The sensitive quantitative measurement enabled us to identify factors associated with contamination, which by analogy to other conditions with similar transmission mechanisms may help improve protection and preparedness in staff dealing with an ill patient who experiences an unknown illness.

Rapid methods for the isolation of actinides Sr, Tc and Po from raw urine.

Rapid methods for the isolation and analysis of individual actinides (Th, U, Pu, Am/Cm) and Sr, Tc and Po from small volumes of raw urine have been developed. The methods involve acidification of the sample and the addition of aluminum nitrate or aluminum chloride salting-out agent prior to isolation of the desired analyte using a tandem combination of prefilter material and extraction chromatographic resin. The method has been applied to the separation of individual analytes from spiked urine samples. Analytes were recovered in high yield and radionuclide purity with separation times as low as 30 min. The chemistry employed is compatible with automation on the ARSIIe instrument.

Is alpha spectrometry reliable for ²¹°Po urine bioassay?

Typically the bioassay method for (210)Po in urine by alpha spectrometry (AS) involves wet decomposition of the sample, which may cause a loss of (210)Po if volatile species are present. To test this hypothesis, urine samples collected from two rats that were i.v. administered with polonium citrate were measured by both AS and liquid scintillation counting, where urine samples were mixed with a scintillation cocktail without any treatment. A split-plot design method was used to compare results from the two measurement methods, showing no evidence of a difference between the two methods. This suggests that the AS method is reliable for (210)Po urine bioassay.

Assessing public health risk in the London polonium-210 incident, 2006.

OBJECTIVES: Mr Alexander Litvinenko died in a London hospital on 23 November 2006, allegedly from poisoning with the radionuclide polonium-210 ((210)Po). Associated circumstances required an integrated response to investigate the potential risk of internal contamination for individuals exposed to contaminated environments. STUDY DESIGN: Descriptive study. METHODS: Contaminated locations presenting a potential risk to health were identified through environmental assessment by radiation protection specialists. Individuals connected with these locations were identified and assessed for internal contamination with (210)Po. RESULTS: In total, 1029 UK residents were identified, associated with the 11 most contaminated locations. Of these, 974 were personally interviewed and 787 were offered urine tests for (210)Po excretion. Overall, 139 individuals (18%) showed evidence of probable internal contamination with (210)Po arising from the incident, but only 53 (7%) had assessed radiation doses of 1mSv or more. The highest assessed radiation dose was approximately 100mSv. CONCLUSIONS: Although internal contamination with (210)Po was relatively frequent and was most extensive among individuals associated with locations judged a priori to pose the greatest risk, a high degree of assurance could be given to UK and international communities that the level of health risk from exposure to the radionuclide in this incident was low.

The international follow-up of individuals potentially exposed to polonium-210 in London 2006.

OBJECTIVES: Following a death from polonium-210 ((210)Po), contamination was found at several sites in London. This paper describes the UK Health Protection Agency's follow-up and assessment of individuals resident overseas who were potentially exposed to (210)Po. STUDY DESIGN: Descriptive follow-up study. METHODS: Individuals were classified into three exposure groups (higher, lower and unknown). Presence and degree of internal contamination were measured by 24-h urinary (210)Po activity (mBq/day). Results over 30mBq/day were taken to indicate probable contact with (210)Po in this incident. Dose assessments were conducted to determine degree of exposure and to identify individuals requiring further follow-up. RESULTS: Overall, 664 potentially exposed persons from 52 countries and territories were identified. Of these, 157 (24%) were in the higher exposure category, and urinary measurements were reported for 31% (48/157). Results for 19% (9/48) of those at higher exposure were more than 30mBq/day. For those at lower exposure, the percentage was 4% (3/68). Results above 30mBq/day were significantly more likely to be reported for the higher exposure category than the lower exposure category (Fisher's exact test P=0.010). Reported dose assessments suggested that identified individuals were not at increased health risk in the long term. Challenges and practical lessons were identified during the investigation. CONCLUSION: The results suggest that it is unlikely that any overseas resident had significant internal contamination with (210)Po. However, this incident clearly demonstrated the scale of international involvement likely to be necessary in other public health emergencies in large cities. The lessons identified have implications for the international health community, particularly with regard to the follow-up of individuals exposed to radiation in one country who then travel to another.

Selectivity of 90Sr urine bioassay technique over 241Am, 238/239PU, 210PO, 137CS and 60CO.

The selectivity of a rapid (90)Sr bioassay technique over (241)Am, (238/239)Pu, (210)Po, (137)Cs and (60)Co has been investigated. Similar to (90)Sr, these radionuclides are likely to be used in radiological dispersive devices. The purpose of this study was to demonstrate the degree to which the (90)Sr bioassay technique is free from interference by these radionuclides if present in a urine matrix. The interfering radionuclides were removed (from (90)Sr) by their retention on an anion exchange column. While, recovery of the target radionuclide ((90)Sr) was found to be >or= 90 %, contributions from (241)Am, (242)Pu and (208)Po were found to be

210Po Log-normal distribution in human urines: survey from central Italy people.

The death in London of the former secret service agent Alexander Livtinenko on 23 November 2006 generally attracted the attention of the public to the rather unknown radionuclide (210)Po. This paper presents the results of a monitoring programme of (210)Po background levels in the urines of noncontaminated people living in Central Italy (near the Republic of S. Marino). The relationship between age, sex, years of smoking, number of cigarettes per day, and (210)Po concentration was also studied. The results indicated that the urinary (210)Po concentration follows a surprisingly perfect Log-normal distribution. Log (210)Po concentrations were positively correlated to age (p < 0.0001), number of daily smoked cigarettes (p = 0.006), and years of smoking (p = 0.021), and associated to sex (p = 0.019). Consequently, this study provides upper reference limits for each sub-group identified by significantly predictive variables.

210Po determination in urines of people living in Central Italy.

This paper presents the results of the monitoring programme on the urines of people living in an area of Central Italy (near the Republic of S. Marino) to evaluate the background level of the 210Po excretion rate (mBq day(-1)) in this region. The volunteers were subdivided in five age classes and in every age class groups of males and females, cigarette smokers and non-smokers were taken into account. The results indicated that the 210Po excretion rate was widely distributed within each group of volunteers. The 210Po excretion rate was <30 mBq day(-1) for 93.2% of people. The obtained results are discussed and some conclusion, based upon the average values, was drawn.

Population monitoring for acute exposure to 210Po.

OBJECTIVE: To investigate the feasibility of using single void urine samples to monitor internal radiation exposure of first responders and large populations int he event of a radiological incident involving the intentional dispersal of 210Po. METHODS: Urinary excretion of 210Po was evaluated and organ absorbed and effective doses were calculated subsequent to an acute unit intake of 210Po. RESULTS: 210Po can be detected in single void urine samples at levels sufficient to detect effective dose below recommended limits. Minimum intakes of 210Po that would result in clinically significant effects were estimated. CONCLUSIONS: Collection and analysis of single void urine samples is adequate to identify persons who may be exposed in the event of a radiological emergency involving 210Po. Also, the first responder limit appears to be sufficiently protective to prevent clinically significant deterministic effects.

Internal dose assessment of 210Po using biokinetic modeling and urinary excretion measurement.

The mysterious death of Mr. Alexander Litvinenko who was most possibly poisoned by Polonium-210 ((210)Po) in November 2006 in London attracted the attention of the public to the kinetics, dosimetry and the risk of this high radiotoxic isotope in the human body. In the present paper, the urinary excretion of seven persons who were possibly exposed to traces of (210)Po was monitored. The values measured in the GSF Radioanalytical Laboratory are in the range of natural background concentration. To assess the effective dose received by those persons, the time-dependence of the organ equivalent dose and the effective dose after acute ingestion and inhalation of (210)Po were calculated using the biokinetic model for polonium (Po) recommended by the International Commission on Radiological Protection (ICRP) and the one recently published by Leggett and Eckerman (L&E). The daily urinary excretion to effective dose conversion factors for ingestion and inhalation were evaluated based on the ICRP and L&E models for members of the public. The ingestion (inhalation) effective dose per unit intake integrated over one day is 1.7 x 10(-8) (1.4 x 10(-7)) Sv Bq(-1), 2.0 x 10(-7) (9.6 x 10(-7)) Sv Bq(-1) over 10 days, 5.2 x 10(-7) (2.0 x 10(-6)) Sv Bq(-1) over 30 days and 1.0 x 10(-6) (3.0 x 10(-6)) Sv Bq(-1) over 100 days. The daily urinary excretions after acute ingestion (inhalation) of 1 Bq of (210)Po are 1.1 x 10(-3) (1.0 x 10(-4)) on day 1, 2.0 x 10(-3) (1.9 x 10(-4)) on day 10, 1.3 x 10(-3) (1.7 x 10(-4)) on day 30 and 3.6 x 10(-4) (8.3 x 10(-5)) Bq d(-1) on day 100, respectively. The resulting committed effective doses range from 2.1 x 10(-3) to 1.7 x 10(-2) mSv by an assumption of ingestion and from 5.5 x 10(-2) to 4.5 x 10(-1) mSv by inhalation. For the case of Mr. Litvinenko, the mean organ absorbed dose as a function of time was calculated using both the above stated models. The red bone marrow, the kidneys and the liver were considered as the critical organs. Assuming a value of lethal absorbed dose of 5 Gy to the bone marrow, 6 Gy to the kidneys and 8 Gy to the liver, the amount of (210)Po which Mr. Litvinenko might have ingested is therefore estimated to range from 27 to 1,408 MBq, i.e 0.2-8.5 microg, depending on the modality of intake and on different assumptions about blood absorption.

Influence of heavy metals upon the retention and mobilization of polonium-210 in rats.

PURPOSE: To provide information about the tissue retention and mobilization of the alpha-emitting radionuclide, polonium-210 (210Po), in rats under combined exposure to heavy metal ions and the chelating agent, 2, 3-dimercaptopropane-1-sulfonate (DMPS). MATERIALS AND METHODS: Rats were pre-exposed intraperitoneally to either CdCl2 or Pb(CH3COO)2. 9 or 15 h later they received 210Po nitrate intravenously. The retention and excretion of 210Po via the urine and faeces of pre-exposed rats, as well as in pre-exposed rats treated with DMPS, were followed. The radioactivity due to 210Po in a broad spectrum of body tissues and excreta was measured by the liquid scintillation counting after sample digestion in a mixture of perchloric acid and hydrogen peroxide. The immunohistochemical localization of metallothioneins (MT) was studied using a mixture of murine monoclonal antibodies directed against MT I+II. RESULTS: The present study revealed different tissue distributions of polonium-210 in the rats pre-exposed to lead or cadmium ions when compared with that in 210Po only controls. Under combined exposure to Pb or Cd, the spontaneous excretion of 210Po was enhanced and could be further enhanced by treatment with DMPS. Treatment with this chelator was efficient even when its start was postponed until 24h after internal contamination of the body with 210Po. CONCLUSIONS: Polonium-210 is bound in vivo to binding sites on various biomolecules, among them erythrocytic enzymes and MT. This phenomenon explains the different affinity and overall distribution of 210Po in control body tissues. When the appropriate binding sites are occupied by lead or cadmium, enhanced natural excretion of polonium-210 occurs.

A systemic biokinetic model for polonium.

Although the biokinetics of polonium has been studied extensively, interpretation of the data is complicated by potential differences with species and route of exposure and the questionable reliability of much of the reported excretion data for man. A study was undertaken to identify the data that are most likely to represent the typical behavior of polonium and apply those data to construct an improved, physiologically realistic systemic biokinetic model for polonium in man. Such a model is needed for interpretation of urinary excretion data for workers exposed to 210Po and reconstruction of the radiation doses received by those workers. This paper reviews the database on the biokinetics of polonium and describes a new systemic biokinetic model for polonium in man.

Human occupational radioactive contamination from the use of phosphated fertilizers.

210Po and 210Pb concentrations in urine, hair and skin smear samples from individuals using phosphated fertilizers have been compared with a control group of occupationally unexposed individuals. Urine and hair samples of the test group showed slightly higher concentrations of 210Po and 210Pb than those observed for the control group. These concentrations remained, however, lower than those for uranium mine workers. Skin smear values indicated contamination by direct contact with dust from fertilizers and this may contribute to skin cancer induction in this risk population.