Dr Lidia Rosiak (Central Laboratory for Radiological Protection)
210Po is natural, short-lived (T1/2 =138.3 days) alpha radiation emitter. It occurs in Earth crust in trace amounts as a product of radioactive Uranium–Radium decay series. The isotope is found in small amounts in human environment: air (<0.5 mBq/m3), drinking water (about 0.5 mBq/L), food (20-200 mBq/kg), tobacco (13.3 mBq/cigarette in Poland ) and cigarette smoke (9.62 mBq/cigarette in Poland). Polonium introduced into the body is strongly radiotoxic, damages circulatory system and lungs. In the case of 210Po igested by humans, the content of this radionuclide in the human body can be determined based on the analysis of excreta such as urine samples. 210Po is a daughter of 210Pb which is beta and gamma emitter of half-decay T1/2 =22.3 years. In small quantities, it is present in the human environment: air (<0.1 mBq/m3), drinking water (approximately 1.5 mBq/l), food (43-155 mBq/kg). 210Pb in the atmosphere, in addition to natural origin, artificial isotope of nuclear explosions origin is introduced (particularly in the years 1952 to 1962). 210Pb is toxic both as a heavy metal, accumulating in the human body and as a radioactive isotope. The aim of the study was the determination together 210Po and 210Pb in urine samples of people not occupationally exposed (smokers and non-smokers). Urine samples of adults Warsaw inhabitants were collected. There were analyzed daily samples and two days samples. The average volume of the sample was 1.73 l/24 h (range 0.9-2.3 l/24 h). The samples, after the addition of the tracer 209Po, were evaporated almost to dryness with the addition of about 50 ml of concentrated HNO3. To the thus prepared samples perchloric acid was added in order to drive off the nitric acid. Samples were evaporated and the residue was dissolved in a 0.5 M solution of hydrochloric acid with a small addition of ascorbic acid (complexing metal ions such as Fe3+). This was followed by deposition of 210Po and 210Pb on a nickel disc dimensions f = 23.8 mm, thickness 0.5 mm, coated on one side with teflon. Deposition was carried out, stirring the solution, for 6 hours at 85°C, all the while controlling the temperature and liquid level. After the deposition disc was removed, rinsed with water, ethanol and dried. Then the measurement of 210Pb beta radiation was carried (thin film covering the disc to eliminate alpha radiation). Next the measurement of 210Po alpha radiation was perforemed. Fluctuations in activity concentration of 210Po in the urine are quite substantial, from 1.01 mBq/l in urine sample of 81 year old woman tobacco smoker to 13.38 mBq/l in urine sample of 62 year old man, also a smoker of tobacco. Average 209Po yield pattern was 42%. Concentrations of radioactive 210Pb in urine are less diverse and range from 0.86 mBq/l in urine sample of 59 year old non-smoker male to 8.97 mBq/l in urine sample of 62 year old female non-smoker. On average, tobacco smokers excreted per day in urine 5.84 ± 6.23 mBq/d (range 1.84 - 21.01 mBq/d) of 210Po isotope and on average 7.37 ± 4.42 mBq/d (range 1.86 - 15.78 mBq/d) of 210Pb isotope. Non-smokers excreted in the urine per day on average 4.23 ± 2.81 mBq/d (range: 2.35 - 10.30 mBq/d) of 210Po and 6.76 ± 2.97 mBq/d (range: 1.86 - 11.14 mBq/d) of 210Pb. Daily excretion of 210Po with urine increases with age insignificantly. The highest values were observed for persons at the age of about 60 years.