Session: Radiation Protection of the Public and the Environment

Investigations of excretion rates of the radionuclides 230 Th, 226 Ra, 210 Pb and 210 Po of persons of the general population and of workers in selected regions in

I. Schäfer 1, G. Seitz 2, M. Hartmann 3

1Nuclear Engineering and Analytics Rossendorf Inc. D-01328 , Germany E-mail: [email protected] 2Institution for statutory accident insurance and prevention in the precision engineering and electrical industry, D-50941 Köln, Germany 3Federal Office for Radiation Protection, D-10318 , Germany

Abstract According to ICRP 60 and European -Directive 96/29, Naturally Occurring Radioactive Materials (NORM) and Technical Enriched Naturally Occurring Radioactive Materials (TENORM) have to take the radiation protection of the general population as well as of workers into account. The German radiation protection regulations stress that particularly. In connection with these regulations, various measurement programs have been and still are performed to investigate the relevant exposure paths. One of these programs is the determination of the intake of natural occurring radionuclides of the uranium decay series in individuals of the public, in exposed regions and houses and also at NORM workplaces by excretion analysis 1. Excretion analysis surveillance is one of the common tools for internal dosimetry. Sources of primordial radionuclides could be the ingestion of foodstuff and water and the incorporation of (mostly airborne) pollution on work places. The main focus in this report is set upon the excretion rate in faeces and urine. A cohort of about 100 persons was selected in five regions in Germany. One of these regions we chose to be the reference area. It is situated in the northern part of Germany with low background radiation. The other regions are in the south-west and south-east mountain areas. Workers were selected from drinking water providers, natural gas providers, balneologic facilities and exhibition mines and museum pits. In the same region also persons of public were recruited for the study. The paper presents selected data of the above mentioned nuclides in urine and faeces samples which were collected during 2002 to 2005. The results are grouped due the parameters like regions and working fields and are discussed in detail. These are 15 mBq/d in urine and 70 mBq/d in faeces and are not as different for the different nuclides as one may expect.

1. Introduction

The geological formations in Germany contain different concentration of the nuclides of the primordial decay series . Thus, the exposure of the population and the exposure at certain workplaces are different depending on the place where one lives or works. According to the new German radiation protection regulations this exposure is to be controlled to perform measures to protect people and the environment if necessary. While the airborne concentration and the external exposure due to 222 Rn have been investigated and mapped very well, in this paper efforts are made to determine the excretion rates of the natural occurring radionuclides to complete national data basis.

1 Project supported by German Federal Ministry for the Environment, Nature Conservation and Reactor Safety (BMU)

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There is quite a large number of papers published concerning the excretion rates of uranium and thorium [ 1,2,3] but few can be found about the excretion rates of the long living uranium daughters 230 Th, 226 Ra, 210 Pb, 210 Po. These are subject of our present study about which we report here. Some of the results, concerning 226 Ra have been published elsewhere[4].

2. Study regions, Acquisition of the participants, Sample collecting

We selected four regions in the low mountain range of Germany where the airborne nuclide- concentration, due to the higher concentration of radioactive material in the soil, is elevated against the median value in Germany. One reference region in the northern part of Germany was chosen as well. The natural airborne activity is expected to be quite low there. At the working places which were investigated in this study natural occurring radioactivity is enhanced. Reasons for that can either be found due to the character of the work itself (e.g. balneologic facilities, drinking water facilities and natural gas providers) or due to the special localization of the work place (e.g. most underground sites). Of course, combinations of those reasons are possible. The working places in connection with the former uranium mining in Germany are not subject of investigations in this study. Participants from firms and plants were acquired. To investigate the influence of regional differences in the intake (caused by air, diet and drinking water) persons who were not occupationally exposed to natural radioactive materials were acquired too. Of course, the acquisition took place on a volunteering base. Due to the limited resources the investigation is rather exemplary than representative. Table 1 shows, that 104 participants are included in the several regions.

TABLE I. Participants and Regions Regions Working places Number of participants Working General Places Population

North Germany Natural gas providers 3 3 Erzgebirge/Vogtland Pits and mines 7 13 Drinking water facilities 9 Balneologic facilities 7 North-east Pits and mines 4 2 Drinking water facilities 6 Balneologic facilities 4 Harz mountains Pits and mines 10 9 Drinking water facilities 3 Balneologic facilities 1 Black forest Pits and mines 6 7 Drinking water facilities 10 Balneologic facilities 0 Total number 70 34

From 2001, July to 2005, March the specimen were collected in three cycles. In each cycle the participants had to collect urine and faeces separately once during a 24 hrs period. All together more than 300 samples of urine and faeces each had to be analyzed.

2 Session: Radiation Protection of the Public and the Environment

3. Analytical methods

Common methods for analyzing 230 Th, 226 Ra, 210 Pb, 210 Po in urine and faeces are Gamma-ray spectrometry [ 5,6,18 ], Emanometry [ 7,8], Alpha spectrometry [ 9,10,11 ] and Liquid scintillation counting [ 12,13,14,15,16,17 ]. All methods require radiochemical preparations of the specimen [ 18 ]. We decided to use high-resolution inductively coupled plasma mass spectrometry (ICP-MS) [19 ] for 226 Ra as we expected very low activity concentrations and Alpha spectrometry for 230 Th and 210 Po. 210 Pb is than evaluated from 210 Po. Faeces were ashed and urine was mineralized by coprecipitation with phosphoric acid and then also ashed. After radiochemical enrichment by ion exchange (DOWEX 50x8) 226 Ra can be analyzed in the ICP-MS (VG Elemental AXIOM). 230 Th is separated from the matrices by anion exchange, liquid-extraction with TOPO / Cyclohexan and fluoride precipitation on micro filters. The radiochemical method for 210 Pb is to be reached the radioactive equilibrium with the daughter nuclide 210 Po. 210 Po determination is carried out by hydroxide precipitation and spontaneous electro deposition.

The following table II shows the Detection Limits (DL) of the used measurement methods.

TABLE II. Methods and Detection Limits (DL) Nuclide Method DL [mBq/Sample] 230 Th Alpha-Spectrometry 0,5 226 Ra ICP-Mass-Spectrometry 1,0 210 Pb Alpha-Spectrometry ( 210 Po) 0,5 210 Po Alpha-Spectrometry 0,5

It must be taken in account that the absolute detection limits of the methods, as given with the results, lead to a specimen related detection limit due to the different volumes and masses of the daily excretions [mBq/d].

The selected methods have obviously been able to lead to results that were, in most cases, significantly above detection limits for all nuclides.

4. Results and discussion

The results are further specified in the Table III. Indicated are the mean values for the median and the relative broad ranges of the deviations. The first line shows the total mean value for all analyzed samples for urine and faeces. Grouped mean values are then shown in the following lines. When comparing the values of this study to the published values we get the next table.

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TABLE III Excretion rates (median) for all nuclides Excretion rates [mBq/d] Published General Range of Matrix Nuclides All values Workers Range of population values values 226 Ra 7,5 6,6 8,1 2,0 - 75 1,0 - 20 210 Pb 7,5 8,5 6,3 1,0 - 187 3,5 - 16 Urine 210 Po 4,3 5,1 3,5 1,0 – 248 1,0 - 15 230 Th 5,1 5,5 4,1 1,0 – 34 0,9 - 47 Faeces 226 Ra 32 37 21 2,0 – 442 38 - 120 210 Pb 34 40 30 1,0 - 395 97 - 110

As an example the complete analytical results for 210 Pb in urine and faeces are given in the next two figures (FIG. 1 and 2) The daily excretion rates in Bq/d are plotted against the code- number of the participants.

200

180

160

140

120

100

80

60 Excretion rates [mBq/d] rates Excretion 40 Quartil 20 75 %

0 0 20 40 60 80 100 120 ID#

FIG. 1: Excretion rate 210 Pb in urine (All values)

4 Session: Radiation Protection of the Public and the Environment

500

450

400

350

300

250

200

150 Excretion rates [mBq/d] rates Excretion 100 Quartil 75 % 50

0 0 20 40 60 80 100 ID#

FIG. 2: Excretion rate 210 Pb in faeces (All values)

For 210 Pb in urine (figure 1) more than 90 % of the excretion rates are lower than 20 mBq/d, while in faeces (figure 2) the range reaches up to 90 mBq/d in 90 % of the results.

40 Median (50%) 35 25%-75% Range without outliers 30 W Workers P General Population 25

20

15

10 Excretion rates [mBq/d] Excretionrates 5

0 226Ra210Pb 210Po -5 WPWPWP

FIG. 3: Boxplots- Workers and population Excretion rates 226 Ra, 210 Pb, 210 Po in urine

5 In figures 3 and 4 it can be seen that the median values of the excretion rates for urine and faeces of workers (W) are higher than those of the general public (P) with the exception of the results of 226 Ra in urine. In the figures are not shown the outliers and extreme values to simplify the plots.

180 Median (50%) 160 25%-75% Range without outliers 140 W Workers P General Population 120

100

80

60

40 Excretion rates [mBq/d] rates Excretion 20

0 230Th 226Ra 210Pb -20 WPWPWP

FIG. 4: Boxplots- Workers and population Excretion rates 230 Th, 226 Ra, 210 Pb, in faeces

FIG. 5 and 6 show the excretion rates in urine and faeces in the working fields. The figures show that the values are dominated by the high excretion rates of the workers in balneologic facilities.

6 Session: Radiation Protection of the Public and the Environment

70 Median (50 %) 25%-75% 60 Range without outlieres B Balneologic facilities 50 DW Drinking water facilities M Mines and pits 40 G Natural gas providers

30

20

Excretion rates [mBq/d] rates Excretion 10

0

226Ra 210Pb 210Po -10 BDWMGBDWMGBDWMGG

FIG. 5: Boxplots- Working fields- Excretion rates for 226 Ra, 210 Pb, 210 Po in urine

240 B Balneologic facilities Median (50 %) 220 DW Drinking water facilities 25%-75% 200 M Mines and pits Range without outliers G Natural gas providers 180

160

140

120

100

80

60 Excretion rates [mBq/d] Excretionrates 40

20

0 230Th 226Ra 210Pb -20 BDWMGBDWMGBDWMG

FIG. 6: Boxplots- Working fields- Excretion rates for 230 Th, 226 Ra, 210 Pb, in faeces

7 TABLE IV Excretion rates (median) for all nuclides in the geographical regions Excretion rates [mBq/d]

Matrix Nuclides Erzgebirge/ North-east Harz Black North Vogtland Bavaria mountains forest Germany 226 Ra 9,0 8,5 6,7 4,2 6,5

210 Pb 10 8,1 5,0 7,8 5,3 Urine 210 Po 2,6 4,0 2,6 6,0 3,1 230 Th 3,4 4,8 7,7 5,2 3,6 Faeces 226 Ra 31 42 41 35 5,3 210 Pb 38 52 32 27 32

The results in different regions do not show pronounced differences. Generally, it can be stated, however, that despite the broad ranges of the deviations, the influences of the geogenic underground in the different regions are to be seen. The lowest median values have been measured in the region North Germany and the highest were determined in the regions Erzgebirge/Vogtland and Bavaria. Some exceptions are to be observed.

5. Conclusion

The excretion rate of 226 Ra, 210 Pb, 210 Po in urine and of 230 Th, 226 Ra, 210 Pb in faeces of members of the general population and of workers who are exposed to natural occurring radioactive material at the working place was investigated A cohort of 104 participants of the study were selected from several regions in Germany where natural radioactivity is enhanced (.Erzgebirge/Vogtland, North-east Bavaria, Harz mountains, Black forest). Workers were chosen from drinking water providers, natural gas providers, balneologic facilities, exhibition mines and museum pits. Differences in excretion rates due to the different regions and due to the different working places have been shown. With the exception of the results of 226 Ra in urine, the results for the workers are somewhat higher then for the members of general population. Differentiation according to the regions shows no significant results. The medians for all investigations of 226 Ra, 210 Pb und 210 Po in urine are from 4 to 8 mBq/d, the median of 230 Th in faeces is 5 mBq/d and the medians of 226 Ra und 210 Pb in faeces are about 30 mBq/d. Further evaluation of the data and computing the uptake and dose may lead to interesting results.

Acknowledgements:

The German Federal Ministry for Environment, Nature Conservation and Nuclear Safety supported this work under contract number BfS St.Sch. 4280, the authors take the responsibility for the content. They express their acknowledgement to the VKTA laboratory crew for the sophisticated analyses, above all Barabara Liebscher, Petra Werner and Wolfgang Boden .

8 Session: Radiation Protection of the Public and the Environment

6. References

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Wallner, G.; Irlweck, K. Determination of Lead-210 and its progenies in Aerosol Fractions of Different Particle Sizes, Radiochimica Acta, 78 (1997) 173 – 176. 18 Köhler, M.; Preuße, W.; Gleisberg. B.; Schäfer, I.; Heinrich, T.; Knobus, B.; Comparison of methods for the analysis of 226 Ra in water samples, Appl. Rad. and Isotopes 56(2002) 387-392 19 Yong-Jae Kim; Chang-Kyu Kim; Cheol-Su Kim; Ju-Yong Yun; Byung-Hwan Rho Determination of 226 Ra in environmental samples using high-resolution inductively coupled plasma mass spectrometry, Journal of Radioanalytical and Nuclear Chemistry, Vol. 240, No. 2 (1999) 613-618

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