Occupational exposure to radon in treatment facilities of the radon-spa Badgastein, Austria

Environment

Pergamon

International, Vol. 22, Suppl. 1, pp. S399-S407, 1996 Copyright 01996 Elsevier Science Ltd Printed in the USA. All rights reserved 0160-4120/96$15.00+.00

PI1 SO160-4120(96)00138-9

OCCUPATIONAL EXPOSURE TO RADON IN TREATMENT FACILITIES OF THE RADON-SPA BADGASTEIN, AUSTRIA H. Lettner, A.K. Hubmer, R. Rolle, and F. Steinhausler Institute of Physics and Biophysics, Hellbrunner Str. 34, University of Salzburg, Austria

El 9509-279

M (Received 20 September

1995; accepted II December

1995)

In the spa Badgastein, Austria, radon is used for therapeutic purposes for various diseases. Radon inhalation is applied in a thermal gallery with atmospheric radon concentrations up to 100 kBq/m3, elevated temperature up to 41°C, and humidity close to 100%, or in the form of radon baths where Rn is emanated from water with high natural Rn activity. Frequently, a combination of both treatment procedures is applied. The high environmental radon concentration levels in the thermal gallery, and in the various radon baths, can result in elevated radiation exposure levels, subject to significant local and temporal changes. Particularly in Rn-baths, the treatment procedures can result in high Rn levels or peaks during the use and replacement of Rn-water. For the assessment of the occupational exposure, a combination of long- and intermediate-term integrating Rn-measurements and continuous Rn and Rn-progeny measurements was used to investigate six different treatment facilities. Long-term integrating Rn-measurements, over a period of 1- 13 months, provide reliable average Rn-concentration. However, these values cannot be used directly for the dose calculation of individuals due to the short-term fluctuation of the radiation exposure. Parallel integrating and continuous Rn-measurements and continuous Rn-daughter measurements were made to calculate personal occupancy weighting factors and Rn-equilibrium factors to determine potential alpha energy concentration exposure of daytime personnel. Copyrigh,

QlYY6 L’l.weier Science Ltd

INTRODUCTION Badgastein is one of the most famous spa resorts with hydrothermal radioactive springs and a ‘Thermal Gallery’, creating high 222Rn activities, temperature, and humidity (up to 4 1 OCand 99% relative humidity). The radioactive springs have been used for centuries for various medical cures. After World War II, the Thermal Gallery, a former gold exploration mine, was found to have very high radon concentrations and served thereon as a Rn-inhalation facility, known now as the “Badgasteiner Heilstollen” for the treatment of various diseases. Thirteen thermal springs are used, delivering 4.5 million L/d of water between 35 and 48 “C, varying only 1% over the year (Pohl-Ruling and Scheminzky 1972).

The question of the origin and dating of the Gastein thermal water was solved by using isotope techniques (Job and Ziitl 1969; Florkowsky and Job 1969). With 13C, 14C, and 3H, the waters were proved to be of meteoric origin of 3600 to 3 800 y of age. According to the results of 2H and I80 measurements (Zimmermann and Zotl 1971), the altitude of the rain falls is about 1800 m. The rainwater is supposed to have seeped down to 3000 m into the rocks to be warmed up to 50 ‘C, welling up again in large fissures and mixing with cold surface water. The infiltration velocity was calculated to be 2 mm/d, within its catchment area, lying in the geological unit of the porphyritic granite-gneiss (Exner 1950). s399

H. Lettner et al.

s400

While the mean value of 222Rn in the Gastein thermal waters (1500 Bq/L, range from 20 to 4400 Bq/L) are unusually high, the 226Ra content is relatively low (mean: 0.70 Bq/L; range: 0.04 - 4.8 Bq/L). The origin ofthis unusually high 222Rncontent in the thermal water has been a subject of debate since its discovery. According to the most reliable hypothesis, the 226Ra dissolved in the water is mainly absorbed and enriched in a special kind of insoluble iron and manganese mud, called ‘Reissacherit’, which is formed from the dissolved salts by the oxygen of the oxygen-rich cold surface water mixing with the oxygen-poor thermal water, and by micro-organisms (Scheminsky and Mtiller 1959). The mud precipitates into the fissures near the surface containing the absorbed 226Ra, delivering the gaseous daughter 222Rn to the passing water (Job and Zijtl 1969). Today, treatment with radon and thermal radonwater is of major economical importance for the villages Badgastein and Badhofgastein in the Gastein Valley. The number of patients consuming the healing effects of these special treatments has grown from 6000 per year in the eighteenth century up to 30 000 in 1940, and more than one million thermal baths nowadays. In the present situation, recommendations given in ICRP-60, referring to occupational exposure to natural radiation at workplaces, have not been implemented in the national law. The problem of occupational exposure to natural radiation is considered in regulations based on knowledge prior to 1972 (&terreichisches Strahlenschutzgesetz 1969; Strahlenschutzverordnung 1972). Exposure to natural radiation in Rn-spas and costbenefit considerations have been addressed already in papers published between 1980 and 1990 (Steger and Grosskopf 1986; Pohl-Ruling et al. 1982; Steinhausler 1986, 1988). In the special case of Badgastein, the only treatment facility, that is controlled with regards to occupational exposure to natural radiation, is the Thermal Gallery (Heilstollen Bockstein, controlled by the National Occupational Health and Safety Authority). All other treatment facilities, using Rn in any form, are excluded from radiation protection control procedures. The anticipated implementation of the ICRP recommendations into national law, in combination with the well-known high Rn-concentrations in the spa waters, were the reasons for this survey Badgastein/ supported by the “Forschungsinstitut Tauernregion”. The objectives of this survey have been defined as follows:

1) Assessment of the occupational exposure of the personnel employed in the different Rn-treatment procedures and facilities; 2) Define a cost-efficient method for further assessment of occupational exposure where it is needed. METHODS

For the survey, eight different sites in the spa Badgastein and Bad Hofgastein were selected in order to cover the whole spectrum of Rn-related occupational activities. (In the text, coding is used referring to the different exposure situations: TFI, TF2, TF3, TF4 treatment facility 1 to 4, WI 1, WI2 - ‘Rn-water infrastructure’, AD - administration, RS - research station). The Rn treatment facilities (TFI-TF4) are the largest treatment facilities. Two sites belong to the water supplying infrastructure (WI1 , WI2), and one site is used for administration and recreation for the spa guests (AD) with water outlets for drinking. One site is a local research station (RS) that is dedicated to the scientific research on the Radon Therapy and only used part-time by researchers from various institutions. For the measurement ofthe Rn-activity concentration, integrating electret detectors (E-Perm, short-term, and long-term electret-detectors) were exposed at the measurement sites in different rooms that were assumed to be representative for the whole building (reception, therapy rooms, physicians’ practice rooms, etc.). The first integrating measurements and personal dosimetry were carried out at TFI from January to April 1993. All other facilities were surveyed during a continuous exposure period covering 15 months from August 1993 until November 1994. One of the objectives was to get information about the seasonal variation of the occupational exposure. The results of the integrating measurements were recorded six times during the exposure period, five times during the first seven months, and once after the spring-summer period. The treatment facilities, 2 - 4, as the most important sites, considering the number of employees, were measured over the whole measurement period, while the other sites of minor importance in this respect, were surveyed less than 17 months. Personal dosimeters were distributed among a selected group of employees in TFl and TF3, partly with time-parallel exposure of Rn-detectors at the corresponding work-places and staff-rooms. In addition to the integrating Rn-measurements, continuous Rn and Rn-daughter measurements, ranging from 2 d up to 2 w, were carried out at Rn-water supply-

Occupational exposure to radon in a radon-spa in Austria

ing treatment facilities: TF2, TF3, and TF4. For the continuous determination of the Rn-daughter activity concentrations, a gross-alpha counting instrument (Pylon ABS), available commercially, was used, using the procedures for continuous measurements recommended by the manufacturer. RESULTS

and DISCUSSION

The results of the integrating Rn measurements are summarized in Table 1. The integrated Rn-activity concentration values (lo-3300 Bq/m3) cover a wide range, depending on the different occupationally-defined sites. Though the highest values were expectedly found in Rn-therapy rooms, very high Rn-activities were also detected at the infrastructure sites, WI 1 and W12, directly related to continuous Rn-emanation from spa water during periods of low ventilation rate. The research station, RS, is another example demonstrating the potential build-up of high Rn-activities not related to any use of Rn-bearing water. The high Rn-levels in the research station are most probably due to Rn-diffusion from the water system and the low ventilation rate in that building, resulting from infrequent use. Two detectors were exposed at an administration building (AD) that offers Rn-water pouring out continuously from a small opening for public consumption. As this building is quite large and wellventilated, the Rn-activity concentration values in the drinking hall, where the detectors were exposed, are low (30-220 Bq/m3). Average Rn-levels, ranging from 850 Bq/m3 to 3300 Bq/m3, were recorded at TFl, where Rn is only used for inhalation in the Thermal Gallery. Similar average levels were recorded in all rooms of the therapy building, with the only exception of the entrance hall, which has an unusual high air exchange rate. The Rnactivities are evenly distributed without any marked height dependency in the 3-story building. Earlier continuous measurement demonstrated that there is a marked daytime variation, dependent on working activities yielding very high nighttime levels due to constant influx of Rn from the Thermal Gallery into the adjacent therapy building. The effect on Rn-distribution within a building, by the physical processes of diffusion and air circulation, are presented in detail: Treatment facilities, TF2, TF3, and TF4, where Rn-water is applied in different therapy procedures, have been surveyed with detectors exposed in different rooms ofthe building. Results of integrating measurements in TF3 are given in Table 2. Rn-activities

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in therapy rooms @n-inhalation room, underwater therapy and tub bathroom treatment) range from 60 to 800 Bq/m3. Efficient ventilation in Rn-inhalation rooms ensures low Rn-activity levels that cannot be considered to be significantly elevated, even above national indoor Rn-levels (Friedmann et al. 1994). Rn-activities in tubbaths ranged between 110 Bq/m3 and 400 Bq/m 3 . In underwatertherapyrooms, Rn-activitiesareconsistently higher than in tub-bathrooms by a factor of 2, ranging from 450 to 810 Bq/m3. Though seasonal variation is small, the differences between summer period (nonheating period) and winter period (heating period) are significant and consistent for all rooms investigated. The average ratio of the results obtained in the period with maximum values (December 1993,28 until March 1994, 17) to the results in the period with minimum levels (11 Aug 1993 to 2 September 1993) is 1.85. While results obtained in TF2 and TF3, in terms of absolute activities and seasonal variation, are similar, Rn-levels in TF4, in general, are relatively low (not exceeding 400 Bq/m3) and with average values in therapy stations below 300 Bq/m3 without any significant seasonal variation. In general, occupational exposure to Rn in therapy rooms is subject to the different treatment procedures controlling temporal variation of Rn and Rn-daughter levels. This is not important in Rn-inhalation therapy rooms, where appropriate ventilation can be applied to keep the levels high for the patients, but unobjectionably low for therapists. In underwater therapy rooms and tub-bath rooms, forced ventilation would result in low Rn-levels, thereby reducing the desired and postulated therapeutic effects of Rn on the patients. In water therapy rooms of any kind, temporal variation of the Rnlevels is significant, showing extreme dynamics due to water changing procedures. For comparison, continuous Rn-measurements recordings from TF2 and TF3 are shown in Fig. 1, both data-sets collected in similar underwater therapy rooms. Periodical temporal variation is mostly exhibited in TF2, where the Rn-water bath is emptied at the end ofthe day and refilled in the morning, while during the daytime, water is continuously renewed, theamountdependingontheconsumptionforunderwater massage patients. In TF3, water is continuously renewed during the daytime, but only partly emptied after working hours and filled up to the daytime level in the morning, resulting in far less periodical temporal variation and maximum /minimum ratios. Continuous Rn-daughter measurements revealed a periodical pattern that is different from the Rn-activity variation (Fig. 2). High Rn-activities do not necessarily imply high levels of Rn-daughters, as there is a marked

70 100 210 230

2

AD

20 240

2

1080

14

35 230

WI2

910 1290

150

8

90 570

610 1000

6

60 410

14

250

11

n

4

810

95 580

10

390

M

WI1

610 1150

6

RS

180

90 1370

11

n

Nov 4Dee 28 min max

470 650

IO 270

i4

TF4

220

390

M

Sep 2Nov 4 min max

220

90

760

560

100

90

227

M

2

1

14

7

10

n

20 75

50

1130

110

10 300

1130

180

375

M

60 290

32 921

Dee 28Mar 24 min max

mean value of all detectors).

4

60 490

9

TF3

1915

70 1800

850 3300 11

9

TFI

n

Sep 2 min max

Apr 2 min max

M

Aug ll-

Jan 18-

TF2

n

Facility

Treat _

M=arithmetic

2

2

14

7

13

n

20 40

570 590

30 220

110 270

20 1220

Apr 28 min max

Mar 24-

30

580

2

1

2

14

7

170

80

6

n

530

M

120 140

380

330 460

36 235

90 290

40 450

Apr 28Nov 14 min max

130

380

395

130

160

180

M

Table 1. Results of integrating Rn-measurements in all facilities investigated during the exposure periods, August 11, 1993 until November 1994 (n number of detectors exposed;

Occupational exposure to radon in a radon-spa in Austria

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Table 2. Results of integrating Rn-measurements Treatment

Facility 3

in TF3 in different rooms of the building. Values in Bq/m3.

Aug, 1 l-

Sep, 2-

Ott, 27 -

Dee, 28 -

Mar, 17-

Mar, 24 -

Sep, 2

Ott, 24

Dee, 28

Mar, 17

Mar, 24

7.5 90 470 490 160 270 300 60 70

140 95 100 550 580 190 290 280 160 140

190 60 30 450 440 110 230 190

200 230 810 810 350 380 400

200 6 130

Apr, 28 150 120 110

170 240 290

160 270 240

80

220

200

120

Reception Rn-Inhalation room 1 Rn-Inhalation room 2 Undenvater therapy 1 Underwater therapy 1 Tub-bath 2 Tub-bath 3 Tub-bath 4 Staff-room Physician practice room

Treatment

AM

170 100 120 570 580 190 280 280 110 140

facility 2

Continuous Rn measurements: April 1994, 6 - 14

2500 1 2000 E 3

1500

E l+

1000 500 0 24

48

72

98

120

144

168

192

Treatment facility 3 Continuous Rn measurements: March 1994, 17 - 23

2500 _11 Weekend

0

24

48

72

96

120

144

168

Time [hours] Fig. 1. Comparison of the continuous Rn-measurement at treatment facilities, TF2 and TF3, in underwater therapy baths, showing the different time-dependent Rn-pattern resulting from different re-filling procedures.

tendency that, when the water is filled into the Rn-bath, the F&daughter activity remains low. This is consistent with the high humidity that appears after filling, and the effect of ventilation and air circulation that remove the

short-lived Rn-progeny from the atmosphere. These efequilibrium factor, which is phase-shifted to the Rn-activities, reaching its maximum values when the Rn-levels are lowest.

fects are pronounced in the time-dependent

H. Lettner et al.

s404

TF2: Rn and Rnd April 1994,6-14

0

48

24

72

96

144

120

Time [hours]

Fig. 2. Temporal variation for Rn, Rn-daughters (Rnd, PAEC), and F-factor at treatment facility, TF2 / underwater therapy bath.

TF3: Rn and Rnd; March 1994,24 - April 1994,6

0,o

‘/ 0

I

, 48

I

,

96

I

,

144

I

‘/

192

I

,

240

I

,

I

288

Time [hours]

Fig. 3. Temporal variation for Rn, Rn-daughters (Rnd, PAEC), and F-factor at treatment facility, TF3/tub-bath room.

As these measurements were carried out by the use of continuous gross-a counting, there are shortcomings and uncertainties due to the method of calculation, but the general trend of phase-shifting seems to be established.

A much less pronounced phase-shifting effect could be observed in tub-baths, where a different form of Rn-water therapy is applied. Figure 3 shows the temporal variation in tub-baths, where baths are

Occupational exposure to radon in a radon-spa in Austria

Table 3. Continuous

s405

Rn- and Rn-daughter measurements, time-averaged for whole-day exposure (12 h, 6 a.m.-6 p.m.), relevant for occupational

exposure (24 h) and averaged for daytime dosimetry.

Facility

Treatment

3

Aug, ll-

Sep, 2-

Ott, 27-

Dee, 28-

Mar, 17-

Mar, 24

Sep, 2

Ott, 24

Dee, 28

Mar, 17

Mar, 24

Apr, 28

140

190

95

60

Reception Rn-Inhalation Rn-Inhalation

room 1

75

room 2

AM

200

150

170

200

6

120

100

130

110

90

100

30

230

Underwater

therapy

1

47.0

550

450

810

570

120

Underwater

therapy

1

490

580

440

810

580

Tub-bath

2

160

190

110

350

170

160

190

Tub-bath

3

270

290

230

380

240

270

280

Tub-bath

4

300

280

190

400

290

240

280

60

160

70

140

80

220

200

120

140

Staff-room Physician

practice

room

110

Table 4a. Results ofpersonal dosimeter survey of occupational exposure to Rn for physicians (Pl-P4, r = room, p = personal detector), conducted in 1993 at TFl, total exposure: ten w. &i-activities in Bq/m’. Jan, 25 -Feb, 2 1410

Feb, 9-12 1140

Feb, 12-17 950

Employee code (physicians) Pllr

Jan, l-25 2250

Pllp

3360

P2fr

2570

1630

1330

900

P2lp

940

3950

610

3090

1660

Feb,l7Mar,15 570

480

Mar, 15-22 3120

Mar,22 -Apr, 2 1390

1550

2700

1210

1550

8860

2160

3270

870 510

P3lr

1980

P3lp

2280

940

730

3610

2180

3430

P4lr

4490

4750

2360

1600

3430

P4lp

5330

5220

2470

5520

5410

AM

AM. Room I AM. Personel 0.98

1570

1270

1670

3660

2930 3330

8550

0.47 0.56 0.61

5420

Table 4b. Results ofpersonal dosimeter surveys of occupational exposure to Rn, conducted in 1994 at TF3, total exposure: two w. El = employee code, UW = underwater therapy, TB - Tub-bath therapy, OT = other therapy. Employee

code,

occupational

task

E 1 I Reception

April 6-14, 1994

April 14-19, 1994

April 19-28, 1994

(Bqlm’)

(Bq/m3)

(Bq/m3)

290

480

E2 / UWT

250

E3 / UWT

330

E4 I UWT

240

180

E5 I UWT

170

220

E6 I UWT

475

650

E7lTB

280

200

applied lasting not longer than 20 min. Afier each bath, the tub is emptied, and the water refilled for the next patient. During the continuous measurement period, encompassing 13 d, a periodical Rn-activity pattern could be observed. This pattern consists of continuous buildup of Rn during the application period, between 6

a.m. and 12 noon, followed by a fast decrease when ventilation was intensified in the non-application period, in the afternoon and another increase during nighttime. The daytime increase of Rn is governed by the continuous addition of Rn from water refilling, reaching maximum levels close to 1000 Bq/m3. Daytime increase

H. Lettner et al.

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Table 5. Dose estimate for occupational exposure to Rn and Rn-daughter in treatment facilities of the Rn spas, Badgastein and Bad Hofgastein. Facility

Exposure situation

TFl

Rn and Rn-daughter inhalation Thermal Gallery Underwater therapy Tub-bath therapy Rn-inhalation rooms Underwater therapy Tub-bath therapy Rn-inhalation rooms Underwater therapy Tub-bath therapy Rn-inhalation rooms

TF2

TF3

TF4

without the influence of Rn-water application, can be observed on weekends when the facility is not in operation. The average Rn-concentration, determined by continuous measurements in underwater therapy stations, increased during working time (6 a.m.-6 p.m.) between 20% (TF3) and 40% (TF2, Table 3), compared to the total average for the measurement period. For TF4, no difference between working time and overall Rn-levels could be observed in the underwater therapy room. The corresponding differences for tubbaths were less pronounced. For underwater therapy rooms, the differences in Working Levels between total and working time are slightly smaller (TF2: 37%, TF3 : 17%), due to the lower F-factors during working time, caused by increased plateout under high humidity conditions. The results of personal dosimetry of employees in underwater therapy rooms (Table 4a), on average, are lower than integrating Rn-measurements or results obtained from continuous measurements. The data show a considerably large scatter between 170 and 650 Bq/m3 (mean = 280 Bq/m3) within the same period of investigation. This scattering can be partly explained by the engagement of the employees with other occupational activities at their treatment stations, where Rn-levels are different, but the high personal monitoring results might also reflect exceptionally high levels of Rn-concentration in dwellings in the high background area of Badgastein. The mean Rn-level, calculated from continuous measurements at the same site (measurement period two weeks prior to personal dosimetry survey, but with comparable meteorological conditions), was 540 Bq/m3 during working time (6 a.m.- 6 p.m.), in good agreement with the results obtained from the detectors ex-

Effective annual dose mSv/y mSv/v 9.4 - 32 1.8 - 2.4

1.3 - 1.7

0.2 - 0.3

posed in the underwater therapy room, while this is almost twice the average Rn-level obtained from personal dosimetry. A rather different situation could be observed in TF 1, where, during the first dosimetric survey carried out between January and April 1993 (Table 4b), personal detectors showed consistently larger Rn-levels than detectors exposed in the corresponding physicians’ practices (ratio: 0.66). For the calculation of the occupational dose (Table 5) for the Thermal Gallery (TFl), an equilibrium factor of 0.6 was used (Pohl 1979). This factor is a rather conservative assumption compared to the other treatment facilities, where the F-value ranges from 0.210.45, with a significant tendency to be low in humid conditions. The dose calculation for TF2, TF3, and TF4 is based on the PAEC given in Table 3. For TFl, the effective annual dose ranges between 14-48 mSv, exceeding the action level recommended for workplaces in ICRP 65 (3-l OmSv). For TFl, the finding of this study has to be verified by a further detailed survey with emphasis on the determination of F-values and evaluation of potential effects of increased ventilation in the treatment facility at physicians’ practices, where high Rn-concentrations are desired neither from a therapeutical, nor from an occupational point of view. Estimated annual effective doses for the other facilities, TF2, TF3, and TF4, ranging from 0.2 mSv to 2.4 mSv, are below the ICRP recommended (ICRP 65) values. As these data are based on measurement periods during the heating period, where Rn and Rn-daughter levels generally tend to be high, the annual effective doses calculated for these treatment facilities are likely to represent upper limits.

Occupational exposure to radon in a radon-spa in Austria

CONCLUSIONS

The results of the pilot study show that the annual effected dose limits for action levels recommended in ICRP 65 are partly exceeded in the treatment facilities investigated. More detailed analysis is recommended, with special emphasis on precise determination of the time-dependent equilibrium factor. Rn-detectors, exposed in rooms, can be used for occupational dosimetry. For dose calculation, a weighting factor, considering the difference between the average total Rn-activity and the average Rn-activity during working hours, has to be applied. Seasonal variation of Rn-activity levels as an effect of different ventilation rates is well-established and has to be considered in dose calculation. F-values in treatment facilities, applying Rn-water therapies determined from continuous measurements, range between 0.21 and 0.45, which are consistently lower than the average F-value of 0.5, commonly used. At the current stage, no data are available about aerosol-size distribution in the treatment facilities. For accurate dose assessment, it is advisable to make aerosol-size distribution measurements in combination with spectrometric analysis of Rn-daughter. Acknowleu’gment-The authors are grateful to the Forschungskuratorium of the Research Institute Gastein-Tauernregion for the financial support of this study.

REFERENCES Exner, Ch. Die geologische Position des Radhausberg-unterbaustollens bei Badgastein (The geological position of the Radhausberg sub-level stope at Bad Gastein). Berg- und Htittenm. Monatsh. 95: I-21; 1950. Friedmann, H.; Atzmtiller, C.; Beck, C.; Breitenhuber, L.; Exler, M.; Gehringer, P.; Hamernik, E.; Hofmann, W.; Hubmer, A.; Kaineder, H.; Karg, V.; Kind], P.; Korner, M.; Le Bail, P.; Lettner, H.; Maringer, F.-J.; Mossbauer, L.; Nadschlager, E.; Oberlercher, G.; Pock; K.; Schonhofer, F.; Seiberl, W.; Sperker, S.; Stadtmann, H.; Steger, F.; Steinhausler, F.; Tschurlovits, M.; Zimprich, P. Ermittlung der Strahlenbelastung der osterreichischen Bevolkerung durch Radonexposition und Abschatzung des damit verbundenen Lungenkrebsrisikos - Pilotprojekt (Assessment of the radon radiation exposure of Austria and estimation of the lung cancer risk - pilot project). Final report Radon in osterreich 1993; Forschungsberichte des Bundes-

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ministeriums fur Gesundheit, Sport und Konsumentenschutz, Sektion III, 3/94; 1994. Florkowsky, T.; Job, C. Origin and underground flow time of thermal waters in crystalline basement complexes. Steir. Beitr. z. Hydrologie. Graz. 21: 37-49; 1969. ICRP (International Commission on Radiation Protection). Protection against 222Rn at home and at work. ICRP publication 65. Annals of the ICRP; 1993. Job, C.; Ziitl, J. Zur Frage der Herkunfi des Gasteiner Thertnalwassers (On the origin of the thermal waters in Gastein). Steirische Beitr. Hydrol. Graz 21: l-1 15; 1969. Osterreichisches Strahlenschutzgesetz. Bundesgesetzbl. Republ. &ten. 8 July 1969. Pohl-Ruling, J.; Scheminsky, F. The natural radiation environment of BadgasteiniAustria and its biological effect. In: Proc. 2nd symp. natural radiation environment, Houston, TX; 1972; 393420. Springfield, VA: NTIS (CONF-720805-Pl). Pohl-Ruling, J.; Pohl, E.; Steinhausler, F.; Daschil, F. Radiation risk in radon spas. Int. congress on the environment and geocancerology, Brussels, Belgium, 1982. Med. Biol. Environ. lO(3): l-4; 1982. Pohl, E. Physikalische Grundlagen der Radontherapie: Organ und Gewebedosen und ihre Bedeutung fur Patient und Personal (Physical basis for radon therapy: Organ and tissue doses and its implication for patients and personel). Int radon-symposium Bad Mtlnster am Stein-Ebemburg 25-27 Mai 1979. Z. angew. BaderKlimaheilk. 26(4): 370-379; 1979. Scheminsky, F.; Miiller, E. Uran und andere radioaktive Stoffe als Spurenelemente im Austrittsgebiet der Gasteiner Therme und die Quellabslze aus dem Gasteiner Thermalwasser (Uranium and other radionuclides as traces in the source region of the Gastein thermal waters in the sediments). Sitzber. &terr. Akad. Wiss. Wien, Math.-naturwiss. Klasse, Abt. II 168: 1; 1959. Steger, F.; Grosskopf, A.K. Aspekte des praktischen Strahlenschutzes bei beruflicher und nicht beruflicher Exposition in Radonkurorten (Radiation protection practice of occupational and non-occupational exposure in radon spas). In: Proc. Italienisch-&terr. Workshop Strahlenschutzaspekte der Radontherapie, Meran 1986. ENEA-AIRP-VS, Kurverwaltung Meran, Italien; 1986: 117-129. Steinhausler, F. Risiko-Nutzen-Kosteniiberlegungen fur verschiedene Formen der Radontherapie (Thoughts on cost-benefit of different forms of radon therapy). In: Proc. Italienisch-Osterr. Workshop Strahlenschutzaspekte der Radontherapie, Meran 1986. ENEA-AIR&VS, Kurverwaltung Meran, Italien; 1986: 131-147. Steinhlusler, F. Radon spas: Source term, doses and risk assessment. Proc. 4th intemat. symp. on the natural radiation environment, Lisboa. Radiat. Prot. Dosim. 24: 257- 259; 1988. Strahlenschutzverordnung. Bundesgesetzbl. Republ. osterreich, February 18, 1972. Zimmermann, U.; Z&l, J. Deuterium und Sauerstoff- 18 Gehalt von Gasteiner Thermal- und Kaltwbsem (Deuterium and oxygen- 18 in thermal and cold springs of Gastein). Steirische Beitr. Hydrol. 23: 127-132; 1971.