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Working Report no. 11, 2006 Radioactive isotopes in Danish drinking waterContents3 Description of Investigation 4 Radioactivity in Drinking Water 11 APPENDIX - Analytical Results PrefaceThis project for investigation of radioactivity in drinking water shall be seen as a documentation of the content of radioactivity in Danish drinking water. During revision of the Drinking Water Directive of the Council of the European Union (98/83/EU) radioactivity was included as a new parameter. Most of the Danish drinking water (about 99%) is obtained from groundwater for what reason radioactivity in Danish drinking water is due mainly to naturally occurring radionuclides. As the risk for high levels of radioactivity in the Danish Underground was assessed to be very low due to the information on the geological underground, the Danish Environmental Protection Agency (EPA) decided to do a national study on selected drinking waters. Selection criteria were:
The plan for the investigation was discussed and decided in co-operation between the Danish EPA, the National Institute of Radiation Hygiene (SIS) and Risø National Laboratory. The Geological Survey of Denmark and Greenland (GEUS) were consulted to help by selection of useful sampling point in areas with possibly increased levels of radioactivity. All the water works selected to take part in this investigation have responded very positively and have been a great help for collecting the many samples. The Danish EPA will hereby thank the water works for their willingness and great help. The project was carried out by Risø National Laboratory and followed by a Steering Committee with the following members: Janne Forslund, Danish EPA (chairman) Sammenfatning og konklusionerEn screeningsundersøgelse af radioaktivitet i dansk drikkevand er gennemført i 2001-2003. Vandprøver er indsamlet fra 296 vandforsyninger, der repræsenterer over 40% af det drikkevand, der leveres fra danske vandværker. Koncentrationer af total alfa-radioaktivitet og total beta-radioaktivitet i vandprøverne er målt og sammenlignet med vejledende parameterværdier på 0.1 Bq/l alfa og 1 Bq/l beta radioaktivitet. For alle prøver var koncentrationerne af beta-radioaktivitet under parameterværdien, mens koncentrationerne af alfa-radioaktivitet for 13 prøver var over parameterværdien. Der blev foretaget supplerende undersøgelser for vandværker i Ebeltoft, Grenå og Frederikssund, hvor koncentrationerne af alfa-radioaktivitet lå over parameterværdien, med henblik på at vurdere den samlede strålingsdosis (Total Indicative Dose, TID). De forhøjede niveauer af alfa-radioaktivitet skyldes hovedsageligt uran i vand fra enkelte boringer. Den årlige strålingsdosis fra indtag af vand med de højeste indhold af uran ligger betydeligt under den samlede strålingsdosis (TID) på 0.1 millisievert, som er grænseværdi for indhold af radioaktivitet i EU's Drikkevanddirektiv. Der blev desuden indsamlet prøver af grundvand, der anvendes som drikkevand, fra områder med forskellig geologisk undergrund, så som grundfjeld og områder med mulighed for forhøjede niveauer af naturlig radioaktivitet. Også disse prøver viste indhold af radioaktivitet svarende til strålingsdoser betydeligt under grænseværdien fra Drikkevandsdirektivet. På baggrund af undersøgelsens resultater er det sandsynligt, at risikoen er meget lille for at finde drikkevand i Danmark med uacceptabelt indhold af radioaktivitet. Der er derfor ikke behov for yderligere undersøgelser af radioaktivitet i dansk drikkevand, der stammer fra grundvand. Summary and conclusionsA screening investigation of radioactivity in Danish drinking water has been carried out during 2001-2003. Samples of drinking water were collected from 296 water supplies representing more than 40% of the water delivered from water works in the country. Total alpha and total beta radioactivity was determined in the samples and compared with screening levels of 0.1 Bq/l total alpha and 1 Bq/l total beta radioactivity. The levels for total beta radioactivity were met in all the water works while total alpha radioactivity exceeded the screening levels for 13 water supplies. Further investigations were carried out for the water works with concentrations of alpha radioactivity above the screening levels in Ebeltoft, Grenå and Frederikssund to estimate the total indicative dose from the water. The elevated levels were found to be due to uranium in the water from individual boreholes. Radiation doses from consumption of water at these uranium levels are estimated to be well below the total indicative dose of 0.1 mSv/y specified in the Drinking Water Directive Groundwater used for drinking water was collected from different types of geological structures including bed rock and areas with potentially elevated levels of natural radioactivity. Also in these cases the concentrations of radioactivity were sufficiently low to meet the requirements in the Drinking Water Directive. In view of the results it seems probable that the risk of finding drinking water in Denmark with unacceptable concentrations of radioactivity is very small. Therefore there is no need for further radiological investigations of the Danish water supply based on natural groundwaters. 1 BackgroundShortly before the revision of the 1980 European Council Directive for drinking water finished in 1998, a set of parameters on radioactivity was introduced. The parameters for radioactivity included tritium and Total Indicative Dose (TID). The Directive requirements on radioactivity are that the concentration of tritium in drinking water does not exceed 100 Bq/l and that the TID does not exceed 0.1 millisievert (mSv) per year. The TID is the sum of radiation doses from radioactive isotopes present in the drinking water excluding tritium, potassium-40, radon and radon decay products. The TID cannot be measured by a single method. To overcome this problem additional parameters and measuring principles were needed. During the following years the EU Commission introduced proposals for monitoring the TID in the Article 12 Committee, elected to update the Drinking Water Directive for sampling and monitoring purposes. These changes of the Directive were used for the present investigation. Because the work on radioactivity was still under way in the Article 12 Committee when the Danish Statutory Order transferred the Drinking Water Directive into Danish regulation, the Order did not require monitoring of the TID by the water works. Instead it is stated in the Order that investigation of the TID is carried out by the Danish Environmental Protection Agency. The present investigation of radioactivity in Danish drinking waters is the result of the work the Danish Environmental Protection Agency has carried out to meet this obligation. The investigation took place during 2001-2003 and has included investigation of nearly 300 water works and single wells. 2 Scope of investigationThe scope of the investigation was to carry out a screening of radioactivity in drinking water for alpha and beta radioactivity from a representative number of the largest Danish water works all over the country. Special areas where higher levels of radioactivity could be expected were also included in the investigation It was assumed that the Total Indicative Dose (TID) was below the parametric indicator value specified in the Directive if the screening levels for total alpha and beta radioactivity were not exceeded. If the screening levels were exceeded, further investigation of specific radioactive isotopes should follow. The TID is calculated from the radionuclide concentrations in the drinking water, dose coefficients from Directive 96/29/Euratom (EC, 1996) and an annual intake of 730 litres. 3 Description of InvestigationIn Denmark there are approximately 3000 water works of which about 10% were selected for this investigation. The selected water works were primarily the major producers of drinking water across the country but included also water works from all over the country. Further locations, which for geological reasons could give rise to elevated levels of natural radioactivity in drinking water, were included. Most of the Danish drinking water (99%) is obtained from groundwater, the rest from surface water. Furthermore, 10 locations from a long-term routine monitoring programme operated by Risø National Laboratory on radioactivity in groundwater were included in the investigation. Total alpha and beta radioactivity for water samples collected in 2001 were measured on dry solids from evaporated samples while the subsequent analyses during 2002 and 2003 were based on liquid samples concentrated by evaporation. If the measured concentrations of total alpha or total beta radioactivity exceeded the screening levels of concentrations of total alpha (0.1 Bq/l) and beta (1 Bq/l) radioactivity in drinking water new samples were taken and nuclide-specific analyses carried out. These analyses included determination of uranium and radium isotopes (234U, 238U and 226Ra). In addition, analyses of radon in water were carried out on samples from water works on the island Bornholm where elevated levels could be expected and on Zealand. By investigation of the dry solids of waters, isotopes like tritium and radon evaporate and are not included in the analyses. Specific analyses of tritium in drinking water were not considered relevant due to the absence of significant anthropogenic sources of tritium in Denmark. Determination of tritium in surface water and precipitation is covered by Risø's routine monitoring programme in Denmark and shows presently typical environmental levels of a few becquerels (Bq) per litre. Earlier in the 1960's, the levels of tritium in precipitation reached 100-300 Bq/l. The groundwaters extracted today may originate from precipitation fallen in the sixties. But monitoring in 1990 - 1995 of tritium in groundwater of all the 960 borings of the Danish Groundwater Monitoring Programme at different depths showed that concentrations of tritium were far below 10 Bq/l except for one boring at 12 Bq/l. The radiation dose per becquerel by ingestion is relatively low for tritium, so even a concentration of 300 Bq/l in drinking water causes only an annual dose of 0.004 mSv. 4 Radioactivity in Drinking WaterRadioactivity in drinking-water is principally derived from two sources:
Naturally occurring radionuclides from both these sources account for almost the entire radioactivity present in Danish drinking water. Traces of man-made radioactive fallout from atmospheric nuclear weapons tests (conducted up to 1980) are detectable in the environment but their contribution to drinking water radioactivity is negligible. The naturally occurring radionuclides originate in the Earth's crust where uranium, thorium and potassium are widely distributed and detectable in all soils and rocks. Uranium and thorium are radioactive, and each decays through a series of radionuclides to stable isotopes of lead, as shown in the decay schemes below. Only a very small percentage (0.0118%) of all potassium is the radioactive isotope potassium-40. It is not considered to be of radiological significance because potassium is an essential metabolic element and its levels in the body are in a state of equilibrium, and therefore do not vary significantly with dietary potassium levels. Uranium series: 238U → 234Th → 234Pa → 234U → 230Th → 226Ra → 222Rn → 218Po → 214Pb → 214Bi → 214Po → 210Pb → 210Bi → 210Po → 206Pb Thorium series: 232Th → 228Ra → 228Ac → 228Th → 224Ra → 220Rn → 216Po → 212Pb → 212Bi → 212Po or 208Tl → 208Pb where the symbols represent elements as follows: Ac, actinium; Bi, bismuth; Pa, protactinium; Pb, lead; Po, polonium; Ra, radium; Rn, radon; Th, thorium; Tl, thallium; U, uranium. The radionuclides in these decay series display a great range of radioactive half-lives from approximately 1010 years for 232Th to 0.0001 seconds for 214Po. Every radionuclide emits either alpha or beta radiation but their radiological significance varies. The solubility of thorium, for example, is so low, that it is only found in water as a component of suspended mineral particles. The natural radionuclides primarily regarded as being of radiological interest in drinking water appear in the following table.
* Radon decay products emit both alpha and beta radiation Only water supplies from groundwater sources are likely to contain significant concentrations of these radionuclides, and the concentrations are as variable as the nature of the soils and rocks themselves. While groundwater may contain natural uranium and thorium series radionuclides, surface water may contain radioactive material deposited from the atmosphere, including both natural radionuclides and materials from man-made sources such as nuclear weapons tests and satellite debris. Because all radionuclides of interest emit alpha or beta radiation, their levels in drinking water may be assessed by measurement of the total alpha and beta activities. The table below shows reference concentrations in drinking water of the most common natural and man-made radionuclides. The reference concentrations are based on the parametric value of 0.1 mSv per year for the Total Indicative Dose, dosimetric data for adults (EC, 1998) and assumed intake of 730 litres per year.
5 SamplingDrinking water samples for total alpha and beta measurements were collected in two-litre plastic bottles. Before filling the bottles, the water was allowed to flush for some time. Once returned to the laboratory, the water samples were treated as soon as practically possible. The time between sampling and evaporation ranged from 2 to 14 days. Larger water samples of 25-50 litres were collected at selected water works and individual borings and used for analyses of uranium and radium. Samples for radon analysis (10 ml) were taken at water works before and after treatment (aeration/oxidation) and transferred directly into counting vials ready for analysis. 6 Analytical Methods6.1 Total Alpha and Beta RadioactivityFor water samples collected during 2001, aliquots of 300-500 ml water were evaporated completely in 60 mm diameter aluminium trays, which were subsequently measured in a multi sample proportional gas-flow counter for 1000 minutes. This proportional counter distinguishes events originating from alpha and beta decays by analysing the pulse height. Self-absorption of the alpha particles in the dry solids of the evaporated salt was corrected for based on measurements using a standardized uranium solution. No correction for absorption of beta particles was considered. Efficiency calibration was made using natural uranium and 90Sr (90Y) standards of known activity. Detection limits were calculated as three times the standard deviation of blank values and gave values of 0.01 Bq/l for total alpha and 0.03 Bq/l for total beta radioactivity. For water samples collected during 2002 and 2003, aliquots of 200 ml water was transferred to a glass beaker and acidified with HCl to about pH 1. The water was evaporated until 1-5 ml was remaining depending on the salt content. The samples were never allowed to run dry. The remaining sample was transferred with a pipette to a liquid scintillation cell and the beaker washed twice with weak (about 1%) HCl, which was added to the sample. Once transferred to the liquid scintillation cell, 10 ml of 'Ultima Gold LLT'-scintillator cocktail was added and mixed thoroughly with the sample. The samples were counted for 150-200 minutes using a Wallac Quantulus 1220 liquid scintillation spectrometer. This spectrometer distinguishes events originating from alpha and beta decays by analysing the pulse shape. By adjusting the pulse shape analyser (PSA), alpha and beta activities are presented separately for the same sample. Blank and background samples were made by evaporating 200 ml distilled water at the same time as the samples. Counting of the blanks was done together with the samples. Efficiency calibration was made using 239+240Pu and 90Sr (90Y) standards of known activity. Detection limits were 0.01-0.03 Bq/l for total alpha and 0.03 Bq/l for total beta radioactivity. The detection limits were determined from blank samples (distilled water) evaporated simultaneously with the water samples and calculated as three times the standard deviation of blank values. Different analytical equipment was used to determine total alpha and beta radioactivity during the project for what reason a comparison was made between results obtained from the gas-flow proportional counter and the liquid scintillation counter (LSC). Even though not ideal, samples previously measured on the gas-flow counter were dissolved and measured on the LSC. Furthermore, since water still remained from one of the stations (Feldbak) this was re-analysed and results compared with previous data. The results of the test are presented in the following table.
The variation between the results is acceptable considering the different methods used. For the Pedersker sample, the total beta results from the proportional counter and the LSC show a variation around the mean value corresponding to an 18% standard deviation. A significant difference was found between LSC and gas-flow measurements for the Feldbak total beta. This may partly be due to the delay in time between the two measurements. The two LSC measurements performed (re-dissolved salts and new evaporation) were done comparatively close in time and therefore may show less difference. One reason for the relatively small difference between the two techniques may be that the correction for self-absorption on the evaporated samples measured on the gas-flow counter was calibrated using natural uranium. Since uranium was the major contributor in samples from several water works this correction was probably unusually correct. For LSC no severe corrections for self absorption (apart from quenching) were necessary. 6.2 UraniumFor samples collected during 2001 and 2002, uranium was determined by alpha spectrometry on large (25-50 litres) samples following radiochemical separation. The 232U tracer used was calibrated gravimetrically against a uranyl sulphate salt. For samples collected during 2003, uranium was analysed directly on selected samples using isotope dilution mass spectrometry (PlasmaTrace 2 HR-ICP-MS). As yield determinant 233U was used. Due to non-significant amounts of 234U present in the 233U tracer, two separate measurements were done for each sample, one with 233U tracer in order to obtain concentrations of 238U and one without tracer in order to obtain the 234U/238U ratio. The 233U tracer was calibrated against a Merck multi-element standard as well as an Aldrich uranium standard solution. The detection limit for the procedure used for 238U is lower than 1 nBq/l. The uncertainty given only considers the counting statistics. The detection limit was set as three times the standard deviation (based on counting statistics) of the blank value measured in 1% distilled nitric acid containing the same amount of yield determinant (233U) as the samples. 6.3 RadiumFor drinking water samples collected during 2001, radium was determined on 5-l water samples by direct radon emanation into Lucas scintillation cells after allowing storage of the water in gas-tight bottles for three weeks to reach radioactive equilibrium between 222Rn and 226Ra. For samples collected during 2002 and 2003, radium was determined by liquid scintillation counting. Radium was co-precipitated onto MnO2 from 2-10 l water using 133Ba as tracer. The MnO2 was dissolved and Ra(Ba) co-precipitated onto PbSO4 which in turn was dissolved in 6-8 ml alkaline EDTA solution, transferred to a liquid scintillation cell and a mineral-based scintillator (Opti Fluor O, Packard BioScience) added in order to collect the radon. After a radon ingrowth period of three weeks, the samples were counted on a Wallac Quantulus 1220 liquid scintillation spectrometer. The detection limit for the procedure used for analysis of radium is lower than 1 mBq/l based on analysis of blank samples containing only the chemicals used for the procedure. Uncertainty is based on counting statistics only. 6.4 RadonRadon concentrations were determined using a liquid scintillation counter and methods described previously (Sundhedsstyrelsen, 1986). The detection limit is approximately 1 Bq/l and analytical uncertainties are estimated to be less than 10%. Radon concentrations were corrected for decay for the time from sampling to measurement using the 222Rn half-life of 3.8 days. 7 ResultsThe locations of water works and water supplies from which samples of drinking water were collected are shown in Fig. 1. Sampling in 2001 covered Bornholm and those water works in the country with the highest production of drinking water. In 2002 sampling focused on Jutland including locations suggested by GEUS as potential sites for elevated levels of natural radionuclides in groundwater due to geological conditions. In 2003 sampling focused on Zealand, Funen and the southern part of Jutland including those water works and single supplies where the concentrations exceeded the screening levels. The locations in Fig. 1 are marked in dark colour if the concentrations of radioactivity were at the screening levels or higher. Most of the results were at or below the screening levels.
Fig. 1. Locations for sampling of drinking water marked with circles. The groundwater locations selected on geological grounds are marked with triangles. Dark coloured marks indicate that the screening levels were exceeded. The analytical results are presented graphically in a scatterplot, Fig. 2, which shows total alpha versus total beta radioactivity concentrations in the samples analysed. The dashed lines indicate the screening levels.
Fig. 2. Scatterplot of observed total alpha and beta radioactivity levels in drinking water in different part of the country. Untreated groundwater from borings selected for geological reasons are included marked with + . The screening levels are indicated by dashed lines. Radon concentrations above the detection limit were found on Bornholm only, in agreement with a previous investigation of radon from Danish water works (National Board of Health, 1986). Radon concentrations in drinking water on Bornholm are higher in un-oxidized water at most sites compared to oxidized water. The highest radon concentrations of 87 Bq/l are found at Vang. However, oxidized waters at the same water works only show radon concentrations of 43 and 48 Bq/l. The relatively high radon concentration in drinking water at Vang is not reflected in correspondingly high alpha and beta values. Recommendations from the Nordic countries and from the European Commission suggest an exemption level for radon in drinking water of 100 Bq/l (Nordic Radiation Protection Authorities, 2000; Kommissionens henstilling, 2001). The radon values measured in samples of both oxidized and non-oxidized drinking water in this study are well below this level. The detailed numerical results are given in the Appendix. The results of total alpha and beta radioactivity are given in Tables 1-5 for Zealand, the islands south of Zealand (Lolland, Falster and Møn), Jutland, Funen and Langeland, and Bornholm. Table 6 lists water works and supplies with levels of total alpha and beta radioactivity at the screening levels or higher. Tables 7 and 8 give results of total alpha and beta radioactivity including uranium and radium isotopes for locations with concentrations at the screening levels or higher. Table 9 gives results for the Risø monitoring stations of total alpha and beta radioactivity including uranium and radium isotopes. Table 10 gives the results of radioactivity in drinking water from untreated groundwater supplies in Jutland selected for geological reasons The concentrations of total alpha and beta radioactivity in drinking water were generally found to be below the screening levels. Out of a total of 294 water supplies investigated, samples from 9 supplies (corresponding to 3%) have shown concentrations at the screening levels or higher. In all cases this was due to increased alpha radioactivity. Concentrations of total alpha and beta radioactivity in drinking water above the screening levels were found near the following locations: Skjern, Ebeltoft, Grenå, Solrød, Stege, Vordingborg, Ishøj, Gedser, Jægerspris, Frederikssund, Hvidovre and Fanø. The highest levels of total alpha radioactivity in drinking water were found at Grenå and Ebeltoft in Jutland with levels up to 0.13 Bq/l and in Frederikssund on Zealand with levels up to 0.2 Bq/l. The water works in these areas were subject to a closer investigation with repeated sampling from individual bore holes and determination of total alpha and beta radioactivity including uranium and radium in these samples. The results demonstrate that the increased alpha radioactivity is due mainly to uranium in the drinking water. The variation of uranium concentrations is large between different boreholes from the same area. At Grenå the concentrations of 234U and 238U were found in the range 0.021-0.14 Bq/l (2-10 µg/l), in Ebeltoft in the range 0.008-0.027 Bq/l (0.8-2 µg/l), and in Frederikssund the uranium concentrations were found in the range 0.00002-0.22 Bq/l (2 ng/l – 15 µg/l). Borings in the Frederikssund area showed generally the highest concentrations of 226Ra, ranging from 0.005 to 0.018 Bq/l. Other water works with somewhat elevated 226Ra concentrations were in Stege, Vordingborg, Gedser and Skjern with 0.011, 0.015, 0.014 and 0.035 Bq/l respectively. The remaining water works analysed showed 226Ra concentrations generally below 0.005 Bq/l. The elevated total alpha levels are generally explained by elevated uranium concentrations. Some exceptions were however found at Stege and Vordingborg with exceptionally low uranium concentrations. The elevated total alpha levels may in this case instead, at least partly, be explained by the elevated 226Ra. In some cases elevated total alpha concentrations may neither be explained by elevated uranium nor by 226Ra concentrations. In these cases the contribution from other alpha emitters such as 210Po and/or 228Th with daughter products could play an important role (Parsa, 1998; Parsa et al., 1999). 8 Total Indicative DoseThe Total Indicative Dose from consumption of drinking water containing radioactivity may be estimated from the analytical data. An adult consuming two litres of drinking water per day containing 0.2 Bq/l of each of the two uranium isotopes 234U and 238U (about 20 µg/l) and 0.04 Bq/l of 226Ra will receive an annual radiation dose of about 0.02 mSv. So even at the water works with the highest measured levels of alpha radioactivity, the annual doses are well below the parametric indicator value of 0.1 mSv/y specified in the EC Drinking Water Directive. 9 ConclusionsThe results of this investigation demonstrate that Denmark fulfils the obligation to meet the requirements in the Drinking Water Directive 98/83/EC for radioactivity in drinking water used in Denmark. The investigation has included samples from Danish water works that produce more than 40% of the drinking water delivered to consumers. The results show low concentrations of natural radioactivity in Danish drinking water and even the highest measured concentrations meet the required limit for the total indicative dose. Groundwater used for drinking water was collected from very different types of geological structures including bed rock and areas with potentially elevated levels of natural radioactivity. Also in these cases the concentrations of radioactivity were sufficiently low to meet the requirements in the Drinking Water Directive. In view of these results it seems probable that the risk of finding drinking water in Denmark with unacceptable concentrations of radioactivity is very small. Therefore there is no need for further radiological investigations of the Danish water supply based on natural groundwaters. 10 ReferencesEC, 1996. Council Directive 96/29/Euratom of 13 May 1996 laying down basic safety standards for the protection of the health of workers and the general public against the dangers arising from ionizing radiation. Official Journal of the European Communities, Brussels. EC, 1998. Council Directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption. Official Journal of the European Communities, Brussels. National Board of Health, 1986. Radon i drikkevand. National Institute of Radiation Hygiene, Copenhagen. Nordic Radiation Protection Authorities, 2000. Naturally Occurring Radioactivity in the Nordic countries – Recommendations. National Institute of Radiation Hygiene, Copenhagen. Parsa, B., Contribution of short-lived radionuclides to alpha-particle radioactivity in drinking water and their impact on the Safe Drinking Water Act Regulations. J. Radiact. Radiochem. 9:41-50; 1998. Parsa, B., Nemeth, W.K., Obed, R.N. The role of radon progenies in influencing gross alpha-particle dertimination in drinking water. J. Radioact. Radiochem. 11:11-22; 1999. 11 APPENDIX – Analytical ResultsThe analytical results are given in Tables 1-10. Concentrations of total alpha and beta radioactivity and of uranium and radium isotopes in drinking water are given in becquerels per litre (Bq/l). Analytical results below detection limits are indicated (<DL).
Table 1. Total alpha and beta radioactivity (Bq/l) in drinking water from water works on Zealand.
Table 2. Total alpha and beta radioactivity (Bq/l) in drinking water from water works on Lolland, Falster and Møn.
Table 3. Total alpha and beta radioactivity (Bq/l) in drinking water from water works on Jutland
Table 4. Total alpha and beta radioactivity (Bq/l) in drinking water from water works on Funen and Langeland.
Table 5. Total alpha and beta radioactivity (Bq/l) in drinking water from water works on Bornholm.
Table 6. Total alpha and beta radioactivity (Bq/l) in drinking water from water works with concentrations at screening levels or higher.
Table 7. Total alpha and beta radioactivity including uranium and radium isotopes in drinking water from locations on Zealand, Lolland, Falster and Møn with concentrations at screening levels or higher.
Table 8. Total alpha and beta radioactivity including uranium and radium isotopes in drinking water from locations in Jutland with concentrations at screening levels or higher.
Table 9. Total alpha and beta radioactivity including uranium and radium isotopes in water from Risø monitoring stations.
Table 10. Radioactivity in drinking water from single supplies in Jutland selected from geological characteristics.
Table 11. Radon concentrations (Bq/l) in drinking water from water works on Bornholm. Results from a previous study are shown for comparison (Sundhedsstyrelsen, 1986).
Table 12. Radon concentrations (Bq/l) in drinking water from waterworks on Zealand.
Footnotes [1] Value not confirmed by repeated analysis [2] Value not confirmed by repeated analysis [3] Value not confirmed from repeated analysis
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