STUDIES ON ENVIRONMENTAL RADIOACTIVITY IN IN 1986

Annual Report STUK-A55

June 1987

STUDIES ON ENVIRONMENTAL RADIOACTIVITY IN FINLAND IN 1986

Annual report

Finnish Centre for Radiation and Nuclear Safety P.O.Box 268, SF-00101 HELSINKI FINLAND ISBN 951-47-04(3-4 ISSN 0781-1705

Helsinki 1967. Vahion painatuskeskus »/«

ENVIRONMENTAL RADIOACTIVITY IN FINLAND 1986

CONTENTS

Page FOREWORD 5

Chapter 1 GROUND-LEVEL AIR 11 Karl Sinkko

Chapter 2 MILK AND OTHER FOODSTUFFS 17 Aino Rantavaara

Chapter 3 RADIOACTIVITY IN PLANTS AND FOODSTUFFS 25 IN 1979 - 1986 Kristiina Rissanen, Tua Rahola and Eero Hiukka

Chapter 4 CESIUM IN LAPPS IN WINTER 1986 57 Tua Rahola and Matti Suomela

Chapter 5 SUMMARY AND DOSE ASSESSMENT 75 Leif Bloftqvlst, Olli Paakkola and Matti Suomela 5

FOREWORD

Immediately after the fallout from Chernobyl was deposited in Finland two interim reports were published containing survey carried out by the Surveillance Department of the Finnish Centre for Radiation and Nuclear Safety (STUK) in 1986. The first, published on May 6, 1986, contained the first observations and measurements in the environment. The second, published on May 16, 1986, completed the first series of observations. Due to the busy days, those two interim reports contained several minor errors and misprints. Corrected results are given in this annual report and its 13 supplements.

In the main report references arc ade to 13 supplements which have been published earlier and con ain the results after the Chernobyl accident on April 26, 19> .

This main report contains the resu? s up to April 1986, the dose estimates for the whole ye? of 1986, and also, for comparison, dose estimates for the n-.ile first year after the Chernobyl accident (from May 1986 tc or JI ;987).

Following reports has been published:

STUK-B-VALO 44 INTERIM REPORT ON FALLOUT SITUATION IN FINLAND FROM APRIL 26 TO MAY 4

STUK-B-VALO 45 SECOND INTERIM REPORT RADIATION SITUATION IN FINLAND FROM 5 TO .( MAY 1986 6

STUK-A55 STUDIES ON ENVIRONMENTAL RADIOACTIVITY IN FINLAND IN 1986 Annual Report

Supplement 1 (STUK-A56) AIRBORNE RADIOACTIVITY IN FINLAND AFTER THE CHERNOBYL ACCIDENT IN 1986 Karl SlnkKo, Hannele Aaltonen, Tarja K. Taipale and .Juhani Juutilainen

Supplement 2 (STUK-A57) RADIOACTIVITY OF WET AND DRY DEPOSITION AND SOIL IN FINLAND AFTER THE CHERNOBYL ACCIDENT IN 1986 Ritva Saxen, Tarja K. Taipale and Hannele Aaltonen

Supplement 3 (STUK-A58) RADIOACTIVITY OF MILK, MEAT, CEREALS AND OTHER AGRICULTURAL PRODUCTS IN FINLAND AFTER THE CHERNOBYL ACCIDENT IN 1986 Aino Rantavaara and Suvi Haukka

Supplement 4 (STUK-A59) RADIOACTIVITY OF VEGETABLES AND MUSHROOMS IN FINLAND AFTER THE CHERNOBYL ACCIDENT IN 1986 Aino Rantavaara

Supplement 5 (STUK-A60) RADIOACTIVITY OF SURFACE WATER IN FINLAND AFTER THE CHERNOBYL ACCIDENT IN 1986 Ritva Saxen and Hannele Aaltonen

Supplement 6 (STUK-A61) RADIOACTIVITY OF FRESH WATER FISH IN FINLAND AFTER THE CHERNOBYL ACCIDENT IN 1986 Ritva Saxen and Aino Rantavaara 7

Supplement 7 (STUK-A62) RADIOACTIVITY OF GAME MEAT IN FINLAND AFTER THE CHERNOBYL ACCIDENT IN 1986 Aino Rantavaara, Tuire Nygren, Kaarlo Nygren and Tapani Hyvönen

Supplement 8 (STUK-A63) RADIOACTIVITY OF REINDEER, GAME AND FISH IN FINNISH LAPLAND AFTER THE CHERNOBYL ACCIDENT IN 1986 Kristiina Rissanen, Tua Rahola, Eero Hiukka and Antti Aifthan

Supplement 9 (STUK-A64) RADIOACTIVITY OF PEOPLE IN FINLAND AFTER THE CHERNOBYL ACCIDENT IN 1986 Tua Ranola, Matti Suomela, Eero Hiukka, Marketta Puhakainen and Sauli Pusa

Supplement 10 (STUK-A65) ENVIRONMENTAL GAMMA RADIATION MEASUREMENTS IN FINLAND AND THE INFLUENCE OF METEOROLOGICAL CONDITIONS AFTER THE CHERNOBYL ACCIDENT IN 1986 Hannu Arvela, Leif Blomqvist, Heikki Lemmelä, Anna Liisa Savolainen and Seppo Sarkkula

Supplement 11 (STUK-A66) FINNISH STUDIES ON RADIOACTIVITY IN THE BALTIC SEA AFTER THE CHERNOBYL ACCIDENT IN 1986 Erkki Hus, Kirsti-Liisa Sjöblom, Ritva Saxen, Hannele Aaltonen and Tarja K. Taipale

Supplement 12 (STUK-A67) MONITORING OF RADIOACTIVITY IN THE ENVIRONS OF FINNISH NUCLEAR POWER STATIONS IN 1986 Erkki Hus, Kirsti-Liisa Sjöblom, Hannele Aaltonen, Seppo Klemola and Hannu Arvala 8

Supplement 13 (STUK-A68) RADIOACTIVITY OF SLUDGE AFTER THE CHERNOBYL ACCIDENT IN 1986 Marketta Puhakainen, Tua Rahola and M&tti Suomela

Earlier results have been published in SFL reports A2, A3, A4, A8, A12, A17 and STL reports A21, A26, A32, A34, A38, A40, A47 and A48 and STUK report A54. The results of survey programmes on natural radioactivity are published separately.

The names of the scientific collaborators responsible are mentioned at the beginning of each chapter of this report.

The following persons assisted in the work of this report: gamma-spectrometric measurements: Mr. Esko Hyttinen, Mr. Timo Ylhäinen; radiochemical analyses: Ms. Eija Hämäläinen, Ms. Virpi Kymäläinen, Ms. Anja Pekkala, Mr. Teemu Pihkala, Ms. Pirkko Saira, Ms. Tuula Virtanen; whole-body counter measurements: Ms. Anne-Maaria Hyttinen, Mr. Jukka Lehtinen, Ms. Irja Putkonen, Ms. Ulla Välikangas; field measurements: Mr. Kauko Tanskanen; automatic data processing: Ms. Ritva Aalto, Ms. Jaana Luukkanen, Ms. Taina Uus and Mr. Jorma Soikkeli; maintenance of low level ^-counters: Mr. Teuvo Ahonen; editing: Ms. Maija Klapuri.

The following organizations and people participated in collecting the samples:

The Defence Forces, The Finnish Meteorological Institute and its Observatory in Nurmijärvi, The Institute of Marine Research, Joensuun Ympäristön Osuusmeijeri, Koilliskuntain Osuusmeijeri Kursu, Kuivamaito Oy, Lihakunta Kuopio, Lihakunta , Livsniedelslabcratorium Mariehamn, Lounais -Suomen Osuusteurastamo, The National Board of Waters, Osuuskunta Maitojaloste, Osuuskunta Pohjolan Malto, Osuuskunta Satamaito, Reindeer Research of Finnish Game and Fisheries Research Institute, Sata-HPmeen Osuusteurastamo, Mr. Jussi Koivusilta. 9/o The authors and the Finnish Centre for Radiation and Nuclear Safety wish to express their gratitude to those who gave their assistance in different ways.

Olli Paakkola Head of the Laboratory for Radionuclide Monitoring 11

Chapter 1

RADIONUCLIDES IN GROUND-LEVEL AIR Karl Sinkko

ABSTRACT

In the air surveillance programme the concentrations of artific­ ial radionuclides are monitored in the air close to the ground to obtain the necessary basic data for estimating the exposure of the Finnish population to fall-out radionuclides, and also to detect atmospheric traces of radioactive materials caused by their use or production.

Airborne dust is collected on filters with high-volume air samplers, and the concentrations of gamma-emitting radionuclides in the air are evaluated. In the first quarter of 1986 only long-lived cesium, caused by earlier atmospheric nuclear explosions was detected. The concentrations of cesium were very low. In January and March a small amount of short-lived, fresh fission and activation products were also observed.

1 INTRODUCTION

Contamination of the environment by radioactive fall-out is a subject of continuing Interest. Artificial radionuclides in airborne dust at ground level have been routinely monitored in the Centre's air surveillance programme since 1968 and around the nuclear power stations since 1975. The main source of the radionuclides detected is the testing cf nuclear devices in 12 the atmosphere, but measurements are also sensitive to releases from nuclear power stations, hospitals or any other use or production of radioactive materials. The aim of the programme is to monitor continuously the concentrations of global fall-out at Nurmijärvi as well as radionuclides in the air In the vicinity of the nuclear power stations at Loviisa and Olkiluoto. This chapter presents the weekly radionuclide concentrations in the air at Nurmijärvi between 30 December 1985 and 24 April 1986. Results of the substantial raise in airborne -adioactivity in Finland after the Chernobyl accident and around the Finnish nuclear power plants are published in detail in the supplements 1 (STUK-A56) and 12 (STUK-A67).

2 RESULTS AND DISCUSSION

At Nurmijärvi, 40 km north of Helsinki, airborne dust is col­ lected on a glass fibre filter, which is changed every Monday and Thursday. These two filters are combined to form a week sample. Air is blown through the filter at a rate of about 18,000 m3/day, corresponding to a linear flow rate of 1.0 m/s. After sampling, filters are compressed to provide suitable count­ ing geometry for radionuclide analysis by gammaepectrometry. The minimur detectable activity varies from one tenth to ten microbecquerels in a cubic meter depending on the nuclide and the amount of air.

The weekly radionuclide concentrations at Nurmijärvi are given in Table I with an accuracy of one standard deviation. 7Be, which is a "natural fall-out" nuclide produced by spallation, is also included in the table because its concentration shows a pattern similar to that of bomb debris nuclides. Only the long-lived 137Cs was observed regularly in ground level air. Before the Chernobyl accident in April the concentrations were below one /iBq/m3. The source of 137Cs is the atmospheric nuclear test explosions made in I960's and 1970's. 13

95 137 The concentration variations of Zr (T1/2 = 65 days) and Cs

(T1/2 = 30 years), which represent relatively short-lived and long-lived fall-out nuclides, respectively, are shown in Figures 1 and 2 (1968-86).

Besides long-lived 137Cs also 131l was detected during a 3-week period in January and during a 2-week period in March together with 134Cs. In March iodine and cesium were also observed in 3 and iodine in 4 in the same time span id the same concentrations. The amount of the release in both cases is estimated to be in the range of giga- to terabecquerei. 134Cs indicates nuclear power industry as the source of release. In a reactor, a significant amount of 134Cs is present whereas the fission yield of 134 Cs in a nuclear explosion is very low.

REFERENCES

1 Sinkko K, Aaltonen H, Mustonen R, Taipale TK, Juutilainen J. Airborne radioactivity in Finland after the Chernobyl accident in 1986. Report STUK-A56. Supple­ ment 1 to Annual Report STUK-A 55. Helsinki: Finnish Centre for Radiation and Nuclear Safety, 1987.

2 Uus E, Sjöblom K-L, Aaltonen H, Klemola S, Arvela H. Monitoring of radioactivity in the environs of the Finnish nuclear power stations in 1986. Report STUK- A67. Supplement 12 to Annual Report STUK-A55. Helsinki: Finnish Centre for Radiation and Nuclear Safety, 1987.

3 Vintersved, I. Personal communication, National Defence Research Institute, Sweden.

4 Ugletveit, F. Fersonal communication, National Institute of Radiation Hygiene, Norway. 14

1368 1910 1912 131i 1916 1918 1980 1982 198* 1S."S

Fig. 1. The monthly weighted mean variation in zirconium-95 concentration at Nurmijärvi in 1968 - 1986.

10

10

10

10

10 J I L -L_J I I I I L 1 I I I I L I960 1910 1912 1914 1916 1918 1980 1982 1984 1986

Fig. 2. The monthly weighted mean variation in cesium-137 concentration at Nurmijärvi in 1968 - 1986. Vtlc

Table I. Weekly radionuclide concentrations (/xBq/m3 ) in ground-level air at Nurmijärvi from December 30, 1985, to April 24, 1986.

Sampling period 7Be 131I 134Cs 137Cs

30.12. - 6.1. 1510 1.1 0" 0.45 6.1. - 13.1. 1270 1.0 0 0.66 13.1. - 20.1. 1260 0.75 0 0.84 20.1. - 27.1. 1230 0 0 0.21 27.1. - 3.2. 1860 0 0 0.48 3.2. - 10.2. 2810 0.71 0 1.25 10.2. - 17.2. 1880 0 0 0.41 17.2. - 24.2. 2100 0 0 0.55 24.2. - 3.3. 1790 0 0 0.47 3.3. - 10.3. 1490 0 0 0.32 10.3. - 17.3. 2510 4.3 0.25 0.77 17.3. - 24.3. 4200 2.0 0.10 0.77 24.3. - 31.3. 1750 0 0 0.20 31.3. - 7.4. 1080 0 0 0.28 7.4. - 14.4. 2150 0 0 0.36 14.4. - 21.4- 2470 0 0 0.38 21.4. - 24.4. 1930 _ b - -

• below the detection limit b the sample contaminated by the Chernobyl fallout 17

Chapter 2

MILK AND OTHER F0ODSTU7FS Aino Rantavaara

ABSTRACT

In January-April 1986 the nationwide survey of man-made radionuclides in milk and other foodstuffs covered milk, beef and pork samples. The nationwide, production-weighted mean contents of both 90Sr and 137Cs in these foodstuffs were slightly lower than in 1985:

90 Sr 137Cs Milk (Bq I'1 ) 0.10 0.23 Beef (Bq kg-1 ) - 0.9 Pork (Bq kg*1 ) - 0.2 18

1 INTRODUCTION

In the beginning of 1986 the nationwide survey of the man-made fallout radionuclides in milk was only slightly modified. The programme for beef and pork continued as in 1985. As the period of observance was only January-April, the results for foodstuffs harvested in summer or autumn 1986 were not included in this report.

2 MATERIAL AND METHODS

Since the beginning of 1986, samples for the nationwide milk survey were supplied monthly by five dried-milk factories (areas I, II, III, VI and VII) and weekly by four dairies (areas IC, IV, IX and X, Fig. 1). The new area IC replaced a previous, also relatively small sampling area la.

Beef and pork were sampled once in spring 1986, using the same methods and sampling areas as earlier (Fig. 2).

90Sr and 137Cs were determined monthly on all milk samples. Meat samples were analysed only gammaspectrometricaily. The methods of analysis were those used previously.2

The nationwide, production-weighted mean contents of radionuclides in milk, beef and pork were based on areal production statistics for 1985.

3 RESULTS AND DISCUSSION

The nationwide mean contents of 90Sr and 137Cs in milk detected in January-April 1986 were 0.10 Bq l"1 and 0.23 Bq l-1 , respectively. The contents were slightly lower than in 1985 (Tables I - III, Figs. 20, 21 in the Report STUK-A583). 19

The nationwide mean contents of 137Cs in beef and pork were somewhat lower tt .. in 1985. In northern Finland the contents were slightly higher than in southern Finland, especially in the case of beef.1

The dietary intake of 90Sr and 137Cs in January-April 1986 was estimated using the data of this study for milk and meat, and the results of 1985 for other foodstuffs.1 Via the average adult diet the following daily intakes were obtained for the period January-April 1986: 0.17 Bq ,0Sr d"1 and 0.51 Bq 137Cs d'1 . The Intakes were, on average, about 10 per cent lower than in 1985. The effects of the fallout from Chernobyl in milk and other foodstuffs have been discussed in reports STUK-A58 and STUK-A59.

The effects of the fallout from Chernobyl on mi]k and other foodstuffs have been discussed in reports STUK-A58, STUK-A59, STUK-A61 and STUK-A62 (see list on page 5).

REPERENCES

1 Studies on environmental radioactivity in Finland in 1984-1985. Annual Report STUK-A54. Helsinki: Finnish Centre for Radiation and Nuclear Safety, 1987.

2 Rantavaara A. Radioactivity in milk and other foodstuffs. In: Studies on environmental radioactivity in Finland 1979. Annual Report STL-A 34. Helsinki: Institute of Radiation Protection, 1980.

3. Rantavaara A., Haukka S. Radioactivity of milk, meat, cereals and other agricultural products in Finland after the Chernobyl accident in 1986. Report STUK-A58. Supplement 3 to Annual Report STUK-A55. Helsinki: Finnish Centre for Radiation and Nuclear Safety, 1987. v.o

Fig. 1. Sources of milk samples for Fig. 2. Collection areas for meat the nationwide survey. During sanples. the suimer the two subareas defined by broken lines (II and III) were included in the main areas, to which the numbers refer. 21

Table I. Monthly ,0Sr concentrations (Bq (gCa)"1 ) In milk from different sampling areas in January-April 1986.

IC II III IV VI VII IX

Jan 0.071 0.057 0.084 0.10 0.076 0.078 0.090 0.079 0.098 Feb

Mar 0.093 0.061 0.073 0.081 0.065 -• 0.091 0.064 O.0M Apr

Mean 0.082 0.059 0.079 0.091 0.071 0.078 0.086 0.072 O.0B6

Mean" 0.098 0.071 0.095 0.11 0.085 0.094 0.10 0.087 0.11 (Bg l-i )

• Not analysed. b The average concentration of calcium in Finnish milk, 1.2 g 1,'1 was used. 22

Table II. Monthly 137Cs concentrations (Bq (gK)"1 ) in milk from different sampling areas in January-April 1986.

I IC II III IV VI VII IX X

Jan 0.07 0.03 0.09 0.14 0.36 0.12 0.22 0.09 0.15 Feb 0.09 0.03 0.09 0.13 0.33 _• 0.21 O.OS C.15 Mar 0.08 0.03 0.11 0.12 .a 0.10 0.18 0.09 0.17 Apr 0.09 _b 0.08 0.13 0.39 _b 0.18 _b -

Mean 0.08 0.03 0.09 0.13 0.36 0.11 0.20 0.09 0.16 Mean* 0.13 0.05 0.15 0.20 0.57 0.17 0.32 0.14 0.25 (Bq 1 -1 )

• Not analysed. b The result was excluded because sample contamination was possible. c The average concentration of potassium in Finnish milk, 1.58 g l,'1 was used. 23

Table III. Nationwide, production-weighted monthly means of *°Sr and 137Cs in Finnish milk in January- April 1986.

*> Sr «7 Cs

Bq (gCa)*1 Bq l*1 Bq (gK?1 Bq 1"1

Jan 0.14 0.22 0.088 0-11 Feb 0.14 0.22

Mar 0.13 0.21 0.079 0.C94 Apr 0.17 0.27

Mean 0.084 0.10 0.15 0.23 24

Table IV. 137Cs in meat sampled for the nationwide survey in spring 1986. The potassium contents are also given.

137Cs K Bq kg-1 g kg*1 fresh wt. fresh wt.

Beef

Area I 0.3 3.2 Area II 0.4 2.9 Area IV 0.5 3.3 Area VII 2.8 2.7

Mean" 0.9

Pork

Area II 0.2 2.5 Area VII 0.7 3.0

Mean" 0.2

•Weighted for production. 25

Chapter 3

RADIOACTIVITY IN PLANTS AND FOODSTUFFS IN LAPLAND 1979-1986 Kristina Rissanen, Tua Aahola and Eero Hiukka

ABSTRACT

Radionuclides originating from nuclear weapons tests in the 1950s and'60s were enriched acre efficiently in the foodchains of L.apland than in the foodchains of southern Finland. The special foodchains of Lapland were studied by measuring samples of ground and arboreal lichens and of other plants, of reindeer «eat, gaae, fish and berries sporadically from 1979 to 1986. Of artificial radionuclides only 137Cs activity was detected in these samples, the 137 Cs concentration showing a decreasing trend until April, 1986.

In 1983 when 91 lichen samples of Cladonia sp. were collected the * *7 Cs concentration was on the average 230 Bq kgr -1 dry weight, the variation being 74-450 Bq kg'1 . In other fodder plants the 137Cs concentration varied from 5 to 970 Bq kg-1 dry weight.

The material of most importance in the intake of l *7 Cs for Lapps was reindeer meat. This meat contained ,37 Cs on average 300 Bq kg-1 fresh weight in February to April, 1986. The l37Cs concentration in fish varied from 9 to 87 Bq kg-1 fresh weight during the whole Investigation period 1979-1986, the concentration in berries being about half the concentration In fish. These results must be taken into account when analysing the situation after the accident at Chernobyl. 26

1 INTRODUCTION

In nuclear weapons tests carried out in the 1950s and '60s large amounts of radionuclides were released through the fission and activation of minerals and metallic iarts of nucisar devices exploded in the atmosphere. In the '70s and *30s small amounts were released from the Chinese atmospheric bomb tests further increasing the total amount of deposition. The fallout originating from nuclear weapons tests was fairly evenly distributed, the accumulated deposited amount of 137Cs at the end of 1985 being 1.8 kBq nr2 .•

Since 1970 the Finnish Centre for Radiation and Nuclear Safety (STUK) has operated a laboratory ^t , on the Arctic Circle. This laboratory follows changes in radioactivity levels in the special foodchains of Lapland by collecting and analysing different kinds of foodstuffs and plant samples from this area. Many of the samples for which results are presented in this paper were collected for determination of natural radioactivity levels and not for detecting fallout nuclides. The aim of the sampling was to get a general picture of the fallout situation and the collection of samples was of a somewhat sporadical nature until April 1986.

After the Chernobyl accident the sampling and measurement activity was greatly intensified as presented in Supplement 85 to this report. 27

2 MATERIAL AND METHODS

2.1 Saaples

2.1.1. Reindeer lichen and arboreal lichens

The most important ground lichen species used as winter fodder by the reindeer are Cladonia, Cetraria and Stereocaulon sp. In 1979 only one reindeer lichen sample (Cladonia sp.) was collected from Pulju, Kittilä. More lichen (Cladonia sp.) samples were collected in 1980 from the Pahtavuoma area, Kittilä, where possibilities of uranium mining was studied. This environment was investigated in order to obtain background data on radionuclide concentrations before the possible start of uranium mining.4 In 1982 samples were collected from three reference areas, -, Mel taus and Apukka at Rovaniemi, all distant from Pahtavuoma. In the following year, 1983, the reindeer research section of the Finnish Game and Fisheries Research Institute (RKTL) collected lichen samples from 46 different places covering1 the reindeer herding area in Finland, Fig. 1. This sampling was done as a part of continuing projects for the investigation of plants used for fodder by reindeer. The lichen samples were carefully sorted according to species. In 1985 a further eight lichen samples were collected from the Kemijärvi area by the RKTL.

In 1980 and 1982 a total of 13 arboreal lichen samples (Alectoria, Usnea and Bryorla sp.) were collecxed from the Pahtavuoma area and from the reference locations. More specific identification of species was not carried out. In 1982 and 1985 some Parmella sp. growing on branches of trees and some Peltlgera sp. growing on the ground were collected from the above mentioned reference areas and Kemijärvi. 28

2.1.2 Other plants

Plants eaten by the reindeer during suminer were collected by the Rovaniemi laboratory in 1979 from Pulju, Kittilä, in 1980 from Pahtavuoma, Kittilä and in 1982 from chs reference areas. Samples from three different bog areas In Kemijärvi and were collected in 1984 by RKTL. The collection locations are marked in Fig. 2 with numbers 1-8. Only those parts of the plants preferred by the reindeer were collected. Plants sampled were herbs, grasses, leaves of trees etc, a total of 165 samples representing 33 species.

2.1.3 Reindeer (Rangifer taranäus)

The Rovaniemi laboratory collected 28 reindeer meat samples from 1980 to 1985. In February, 1986 8 reindeer meat samples were collected. In April, three weeks before the Chernobyl accident, 11 samples of reindeer meat were brought by Lapps attending a whole-body measurement at Inari (Chapter 4 in this report). From reindeer, slaughtered on April 24, two days before the accident, a further seven samples were obtained by the RKTL.

The muscle tissue samples were taken from the leg, the joint or the nock. Both adult reindeer and calves, were sampled.

2.1.4 Game

Different kinds of game samples w*»re collected from various locations in Lapland from 1980 to March 1986. Samples from twenty mooses (Alces alces) and seven bears (Ursus arctos) were received as were two hares (Lepus timidus) five white ptarmigans (Lagopus lagopus) and one capercaillie (Tetrao urogallus). Most mooses sampled were killed in collisions with automobiles. All other samples were obtained by hunting. 29

2.1.5 Fish

Fish wer-j sampled from 1980 to 1985. The most frequent fish sample was pike (Esox luclus); 21 specimens. Other fish sporadi­ cally sampled were whitefish iCoregonus lavaretus), perch (Perca fluvlatilis), roach (Rutilus rutllus), salmon (,salmo salar), bream {Abramis brama) and vendace (Coregonus albula). The sampling locations are shown in Fig. 3.

2.1.6 Berries

A great many wild berries of economical significance to the Lapps grow in the forests and moors of Lapland. Cloudberry (Rubus chamaemorus), bilberry {Vacclnlum myrtlllus) and cowberry {Vacclnlum vltls idaea) samples were collected from 1980 to 1985.

2.2 Sample treatment

Litter and substratum were removed from the lichen and other plant samples. The lichen samples end ell other plant samples were dried at 105°C, homogenized and packed into cylindrical containers of 35 ml volume. After drying the berries were ashed at a temperature lower than 450°C. All bone, fat, sinew and membranes were removed from the muscle tissue samples of reindeer, game and fish. Then the samples were ground, dried at 105 °C and homogenized before being packed into the cylindrical measuring containers, apart from the moose and the fish samples which were further ashed and only then packed into the cylindrical containers. 30

2.3 Gammaspectrometric analyses

All samples were measured at the laboratory of STUK in Helsinki in the same cylindrical geometry from 200 to 1400 minutes. The measurements were performed with i lithium drifted germanium detector (efficiency 32 %, energy resolution 2.00 keV for 1.33 60Co) and a multichannel pulse-height analyser. The measurement results were analysed usir/ computer programs of STUK. The minimum detectable activity (MDA) of 137Cs for a measurement time of 200 minutes or longer was less than 0.1 Bq. The potassium results wers calculated from *°K. Natural potassium contains 0.012 per cent of *° K.

3 RESULTS

3.1 Ground and arboreal lichens and other plants

All 137Cs results for plants are presented in Bq kg-1 dry weight and all potassium results in g kg*1 dry weight. Of the artificial radionuclides only 137Cs could be detected in the plant samples. Table I presents the 13 7 Cs concentration in reindeer lichen (Cladonia ranglferlna, Cladonta stellar is and Cladonla mitis) samples from 1979-1982. The lowest concentration 41 Bq kt,-1 dry weight was found in 1982 at Kalkkimaa, Tornio and the highest 630 Bq kg-1 in 1979 at Puljutunturi, Kittilä. The results of the extensive sampling of lichen in 1983 are presented in Table II. The mean 137 Cs-concuntration in all Cladonia and Cetraria species was about 230 Bq kg"1 dry weight, the minimum being 74 and the maximum 460 Bq kg-1 . The mean concentration for the Stereocaulon sp. was found to be 330 Bq kg-1 and the variation 110 to 930 Bq kg-1 . Fig. 4 shows the concentrations of 137Cs in Cladonia species from different locations in Lapland in 1933. In Cladonia sp. collected in 1985 from Kemijärvi the 137Cs concentrations varied from 170 to 230 Bq kg-1 , the concentration in one Stereocaulon sample being 300 Bq kg-1 . In a Cladonia 31 vnclalis sample from the same area, however, the concentration was only 25 Bq kg-1 . The mean potassium concentration in the ground lichen samples was 1.5 g kg'1 and the range from 0 to 5.3 g kg-1 .

Table III presents the 137Cs-concentrations in arboreal lichens (Alectorla, Usnea or Byronia species) collected in 1980 and 1982. These concentrations, with mean values at Pahtavuoma, Kittilä 170 Bq kg-1 in 1980 and at the reference areas 69 Bq kg'1 in 1982 are lower than the corresponding concentrations in reindeer lichen. The mean potassium concentration was 3 g kg-1 . The 137 Cs-concentration in Parmela sp. growing on branc­ hes of trees and in Peltlgera growing on the ground was found to vary from 130 to 710 Bq kg-1 .

The 13 7 Cs concentrations varying from 5 to 970 Bq kg-1 dry weight in herbaceous plants and leaves of trees are presented in Table IV. It can be seen that the result may vary with by a factor of almost 50 for different samples of the same species. The potassium concentrations also varied greatly, from 0 to 45 g kg-1 .

3.2 Reindeer

The results of the reindeer muscle tissue measurements are given in Tables V and VI. The l37Cs concentration in 1980-85 was found to vary from 120 to 580 Bq kg-1 , the variation in 1986 before April 26 being 160-590 Bq kg-1 and the mean 300 Bq kg-1 fresh weight. Fig. 5 illustrates the differences of the 137 Cs- concentration in 11 reindeer muscle tissue samples collected in 1986 before April 26.

3.3 Game

The results of the measurements of the 20 moose samples are given in Table VII. The 137Cs concentrations vary from 8.5 to 160 Bq kg-1 the mean value being 43 Bq kg-1 fresh weight. The 137Cs 32 concentrations of the seven bear samples are given in Table VIII. The mean concentration was found to be 100 Bq kg-1 and the range 20 to 180 Bq kg1 fresh weight. The J; 7 Cs concentration in hare in October, 1985 was 65 Bq kg-1 fresh weight. The grouse willow samples collected at in March, 1986 contained on average 11 Bq kg-1 fresh weight. The capercaillie (Tetrao urogalius) contained 12 Bq kg-1 fresh weight.

3.4 Fish

The 13 7Cs concentrations in fish from various lakes are given in Table IX. In Table X the results are grouped separately for each fish species. The lowest concentrations, below 10 Bq kg*1 fresh weight, were found in salmon and vendace and the highest about 40 Bq kg-1 in pike and whitefish. The 137Cs concentration in pike caught in June-July 1985 from the Apukka lake is given as a function of the weight of the fish in Fig. 6. The concentration seems to increase with the weight of the fish.

3.5 Berries

The 1,? Cs concentrations in berries are presented in Table XI. The highest concentrations, about 40 Bq kg-1 fresh weight, were found in cloudberry growing on bogs and moors. In bilberry and cowberry growing on drier land and in forests the concent­ rations were lower, below 20 Bq kg-1 fresh weight. 33

4 DISCUSSION

The foodchains in Lapland were studied intensively in the 1960s and*70s.2 It was shown that as late as 1977 "Zr-« Nb and 10SRu from fresh fallout could be detected, but the * 37Cs concentration showed no increase from the years before.7 Of radionuclides created in nuclear weapons tests, only 137 Cs cculd be detected gammaspectrometrically in samples collected in the 1980s before the accident at Chernobyl. Since samples were not collected systematically each year from the same locations, no reliable conclusions regarding effective half-lives can be drawn based on the material in the present study. The study shows, however, that the 137Cs concentration in lichen decreased until the Chernobyl accident compared with results from the beginning of the 1970s. It can also be seen that in spite of rather evenly distributed deposition the ,37Cs concentrations in reindeer, lichen from different locations varied.

The 13 7 Cs concentration in ground lichens depends on the qua] ity of the soil, the amount of precipitation and, in the reindeer herding area, on the amount of grazing. In arboreal lichens the 13 7 Cs concentrations seemed to depend on the amount of absorbing surface area and the quality of the surface. Dark species contained more 137 Cs than light species. The low 137 Cs concentrations found in lichen from the industrialised Kemi- Tornio area may result from the clay and lime in the soil as well as from other than radioactive environmental pollution. The arboreal lichens collected from this area were poor. Also other plants from this area show low 137 Cs concentrations.

There are great differences In the feeding habits of reindeer during the different seasons of the year.1 During the bare ground season about 160 days, they eat various grasses, herbs, leaves of trees and bushes, shrubs e':c. In winter the basic types of fodder are ground-lichens and some winter-green plants (Des- 34 champia flexuosa, Eriopherua, Equlsetum and Carex species) and also some shrubs and dry leaves, which all the reindeer have to dig from under the snow. In the central and southern parts of the reindeer hearding area in Finland the arboreal lichens are also important. There were great differences in 137Cs concentrations in the 1980s between different fodder plants eaten by the reindeer. The I}7Cs concentrations in herbaceous plants varied 200 - fold, the mean concentration in lichen being about 25 per cent of the maximum value found in herbaceous plants. The highest 137Cs concentrations were found in plants growing in wet surroundings or on bogs and moors with low pF and deficiency of potassium.

The decreasing trend of 137Cs content until the Chernobyl accident was found also in the reindeer muscle tissue samples. A value of 630 Bq kg*1 fresh weight in muscle tissue is reported for 1978 7 and of 490 Bq kg-1 for 1979.3 The 137Cs content varies with the time of the year and the age of the reindeer. Some variation can also be found between muscle tissue samples from different parts of the same reindeer. In Fig. 5 the variation in a sample material, mean 300 Bq kg'1 fresh weight, collected within a few months at the beginning of 1966 from a restricted area is illustrated. The 137Cs content in muscle tissue from moose is about 10 per cent of that in reindeer muscle tissue. The same ratio has been reported earlier also by other Investigators. -

The conclusion which can be drawn is that before the Chernobyl accident reindeer meat still contained about 300 Bq kg-1 fresh weight 137Cs originating from nuclear weapons tests. This must be remembered, when analysing the situation after the accident. 35/3

1. Nieminen M, Heiskari U. Diets for freely grazing and captive reindeer during summer and winter. In press,. 1988.

2. Rahola T, Miettinen J K. Fallout levels of "7 Cs and seen shortlife nuclides in Finnish Lapland during 1966- 1976 in the foodchain lichen - reindeer - »an. Radioactive foodchains in the subarctic environment. Progress Report Aug. 15, 1976 - Nov. 14, 1977, Helsinki, 1977.

3. Rantavaara A. Hirvenlihan cesium-137 pitoisuus Suomes­ sa. Cesiue-137 in aoose seat in Finland (Summary in English}. Suomen Riista 1982; 29, 5 - 13.

4. Rissanen K. Natural radioactivity around a prospected uranium mining area in Finnish Lapland. Comparison of risks resulting from major human activities. Xth Regional Congress of IRPA. Avignon. 1982; 557 "63.

5. Rissanen K, Rahola T, Hiukka E, Alfthan A. Radioactivity of reindeer, game and fish in Finnish Lapland after the Chernobyl accident in 1986. Report STUK-A63. Supplement 8 to annual report STUK-A55. Helsinki: Finnish Centre for Radiation and Nuclear Safety, 1987.

6. Studies on environmental radioactivity in Finland 1984- 1985. Annual Report STUK-A54. Helsinki: Finnish Centre for Radiation and Nuclear Safety, 1987.

7. Tillander M, Jaakkola T, Miettinen J K. Cesium 137 In the foodchain lichen - reindeer - man during 1976- 1978. Radioactive foodchains in the subarctic environ­ ment. Progress Report Nov. 15, 1977 - Nov. 14, 1978, Helsinki, 1978. 37

©

® ®\ © © © 0/ © © $

>-*-. © '© '.-

( ~v. 1 *. ^,---

Fig. 1. Sampling locations of lichen in the reindeer herding district in Finland, 1983- 38

2. Kittilä - , Pahtavuoma 1980 surroudings with 10 km radius 3. Rovaniemen mlk, Apukka - Perunka 1982 4. Rovaniemen mlk, Keltaus RKTL 1982 5. Kemi, Tornio, , Simo 1982 6. Utsjoki, Kevo 1982 7. Inari, Kaamanen, Kutuharju 1982 8. Kemijärvi, Tynnyriaapa, Latva-aapa 1984 Pelkosfsnni omi, Raato-iapa

Iin. 7.. .'tripling locations of pi.int.-; from Lap] and. 39

Fig. 3. Sampling location of fish In northern Finland divided into three drainage basins. 40

i'irj. 4. r:^;m ooncontrationr. of ,37 Cs in Hq kg"1 dry woiqht in Olndonia spocinn from different: Joo-ifcion.'; in tho Finnish r'lind'i'jr hordinq nro.) in ioni. 41

JZ o> --4 i I O 2 £. a c 14 ni n

X XT n c o

* b ±> •C O c o u u

S3J3t7a9 10 1! Sample number

Fig. 5. Variation of *37Cs-concentration in 11 reindeer muscle tissue samples collected from the Inari-Utsjoki area in 1986 before April 26.

*J SO-) C 1 OT • -t i o : S i £ J r. i CI So - b "M 1 _ i w 1 •* i C *o •• £3 ; C 1 o ; -* I *> i * ) t *>< 0c i 0 c ! 0 1 0 J <3 "V-r —, r 0 0 fcf<»ifjh{, kg Fig. 6. Concentration of * 37Cs in pike samples from lake Apukka, Rovaniemi, in June-July 1985 as a function of the weight of the f^sh. 42

Table I. The mean concentrations of "7 Cs (Bq kg-1 dry weight) and potassium (g kg'1 dry weight) in lichen {Cladonia sp) from Lapland 1979 to 1982. Ranges are given in parenthesis.

Municipality Year Number of of sampling samples 137Cs K

Kittilä 1979 1 630 1.8 1980 360 1.6 (270 - 440) (0- - 1.9)

Inari 1982 260 1.3

Kemi 1982 69 1.3 ( 66 71) (1.1 1.6)

Keminmaa 1982 220 1.5

Rovaniemen mlk 1982 210 1.6 (170 - 280) (0.8 - 2.5)

Simo 1982 85 4.8

Sotkamo* 1982 190 0.3

Tornio 1982 110 0.8 ( 41 - 170) (0.7 - 0.8)

Utsjoki 1982 340 0.2

1 > below detection limit b > in province Oulu 43

Table II. Tha mean concentration of 137Cs (Bq kg-1 dry weight) and potassiunr (g kg-1 dry weight) in reindeer lichen species collected In 1983. Ranges are given in parenthesis.

Species Number of samples 13'Cs

Cladonla rangiferlna 33 230 1.4 ( 79 •- 430) to­ - 3.1) Cladonla stellarls 26 250 1.1 (140 -• 440) to - 3.5) Cladonla mitts 32 230 1.2 ( 74 -- 460) (0. 2 - 2.4) Cetraria nivalis 220 1.9 (150 •- 380) (0. 3 - 3.7) Stereocaulon sp. 24 330 2.2 (110 •- 930) (0 - 5.2)

•below detection limit. 44

Table 111. The nean concentration of 137Cs (Bo. kg-1 dry weight) and K (g kg-1 dry weight) in Alec tor la, Usnea and Bryonia species in 1980 and 1982. Rönges are given in parenthesis.

Municipality Year Number of of sampling samples 137Cs

Kittilä 1980 6 170 1.8 (150 - 200) to­ - 7.3)

Rovaniemen mlk 1982 5 73 2.4 ( 47 - 96) to - 6.2) Tornio 1982 1 60 5.4

Simo 1982 1 56 8.7

'below detection limit 45

Table IV. Concentrations of 137Cs (Bq kg-1 dry weight) and potassium (g kg-1 dry weight) in plant samples collected in 1979 to 1984. The numbered samp- Xing xocarion s are pressnte a inraj . z. Ranges are gLveni n parentnesis.

Number of Sampling Species sanities 137Cs K locations

Horsetail 14 270 33 3, 4, 5, 8 Equlsetua sp (44 - 970) (21 - 45)

Scirpus 2 690 4.4 8 Scirpus sp (600 - 770) (2.9 - 5.9) QutU-it-grasfl 6 11C 7.6 8 Eriqptanra sp (77 - 170) (2.6 - 13)

Sedge 7 260 16 1, 2, 4, 8 Carex sp (41 - 560) (10 - 27)

i o Forest wiregrass 4 110 18 5, 8 Deschampsla flexuosa (71 - 150) (14 - 21)

Birch 26 47 8.7 1, 2, 3, 4, Betula pubescens (6.4 - 290) (2.0 - 14.8) 5, 6, 7, 8

Dwarf birch 4 35 3.7 8 Betula nana (26 - 59) (2.1 - 6.2)

Willow 15 96 12 1, 2, 3, 4, 5, 1 Salix sp (5.4 - 570) (0- - 21)

Aspen 1 61 12 7 PppuZus trenula

Starwort 1 310 6.5 8 Steilaris sp

Violet I 220 24 8 Viola sp

Marsh cinquefoil 3 290 12 8 Potentllla palustris (210 - 430) (7.6 - 16) 46

Table IV Continued

Cloudberry 2 230 12 Rubus chamaanarus (150 - 310)

Rowen 5 29 16 3, 4, 5 Sarbus ainiparia (11 - 47) (14 - 17)

Willow-herb 6 82 15 3, 5, 8 Epilcbiim sp (16 - 370) (6.8 - 20)

Cowbane 1 130 23 Cicuta virosa

Milk parsley 1 73 20 Peucedanura palustre

Cowberry 3 81 3.9 8 Vaccimium vltis-idaea (51 - 120) (3.3 - 4.9)

Bilberry 11 88 6.6 3, 4, 5, 8 Vacclrdim nyrtilZus (18 - 190) (5.0 - 9.4)

Bog bilUberry 3 70 5.1 8 Vaccinlim uligrinosun (54 - 83) (4.0 - 6.8)

Cranberry 3 110 4.8 8 Vacciniun oxycoccus (70 - 140) (4.3 - 5.4)

Black bearberry 1 39 8.3 Arctostaphylos alpina

Bog rosemary 3 71 3.9 8 flndrcmeda pollfolia (51 - 94) (2.3 -• 5.1)

IIBUH'^AJI XG/& 2 130 4.1 8 Ledum palustre (110 - 140) (3.9 -- 4.3)

Crowberry 11 51 4.9 3, 4, 5, 8 Bnperturo nigrum (28 - 100) (2.2 -- 6.3)

Bogbean 10 280 25 2, 3, 4, 5 Menyanthes trlfollata (56 - 880) (17 -- 36) 47

Table IV Continued

Mars lousewort 2 140 5.3 8 Pedlcularis palustris (120 - 160) (3.3 - 7.3)

Pine 1 52 4.3 Pinus silvestris

Spruce 2 37 2.6 3, 8 Picea excelsa (36 - 39)

Juniper 1 19 6.6 Junlperus communis

Bog moss 8 210 4.1 8 Sphagnum sp (130 - 380) (O- - 6.0)

Halrtnoss 4 270 3.5 8 Polytricftum sp (200 - 380) (0.4 - 5.0)

Nbss 1 232 0.7 8 Brepanocladus • below detection limit 48

Table V. The mean concentrations of 137Cs (Bq kg*1 fresh weight) in reindeer meat in Northern Finland 1980 to 1985. Ranges are given in pa­ renthesis.

Sampling Date Number location of of sampling samples 137 Cs

Kittilä 8-9/80* 3b 170 (150 - 180)

9/80 lb 250 12/80 2" 560 (530 - 580) 11/84 lc 150

Ylitornio 10/84 3C 200 (160 - 220) 10/85 2" 230 (190 - 270)

Inari-Utsjoki 10/85 4d 150 (120 - 200) 10/85 2« 290 (250 - 330) Province Lapland 10-11/85 7" 340 (210 - 530) Province Oulu 10/85 3" 420 (350 - 550)

• month/year bmeat from different parts of the reindeer eneck dleg 49

Table VI. The mean concentration 13 7 Cs (Bq kg-1 fresh weight) in reindeer «eat in Lapland 1986 before the Chernobyl accident. Ranges are given in parenthesis.

Sampling Date Age Number location of of sampling samples 13 7 Cs

Kemi - Sompio 2/86* calf 4b 370 (320 - 580) 2/86 adult 4b 380 (240 - 590) Inari 3/86 adult 10c 280 (190 - 400) 3/86 calf lc 360

4/86 calf 6b 210 (160 - 330) 4/86 adulf lb 26

• month/year bleg cjoint dKaamanen reindeer research yard, lichen feeding •Kaamanen reindeer research yard, hay feeding 50

Table VII. Mean concentration of 137 Cs (Bq kg-1 fresh weight) in moose (Alces alces) from 1980 to April, 1986. Ranges are given in parenthesis.

Municipality Date Number of of sampling samples 137Cs

Inari 11/1981* 54

Keminmaa 11/1981 4 23 (20 - 25) Kittilä 12/1980 1 65 10/1981 2 52 (39 - 64)

Kolari 10/1981 2 120 (90 - 150)

Ranua 10/1981 3 38 (23 - 55)

Rovaniemi mlk 12/1981 3 13 (11 - 14) 2/1982 2 10 ( 8,5 - ID

Salla 10/1981 1 45

Sodankylä 10/1981 1 160

• month/year 51

Table VIII. Concentration of l37C» (Bq kg"1 fresh weight) In bear (Ursus arctos) in 1984 and 1985.

Municipality Dato Number of of eempl; ng samples 137 Cs

Suomussalmi 9/1984* 1 110

Kittilä 5/1985 1 180

Pudasjärvi 5/1985 1 55

Salla 9/1984 1 20b 5/1985 1 100

Savukoski 5/1995 2 110 (84 - 130) * month/year bliving at a dumping placa 52

labia IX. it» neon oumsiUaliana of l"Ca (ttj kg-» ttmmh wight) In fish fxoa diff­ erent lakes in Ispland In 1980 to 1985. Range» ax» given in parenthesis.

Munf crtnwl Ity Fish of lake spurts» of of ssspllnii sasples >"Cs

Ksfldjazvl Kemijflrvi

- l£htosalmi Vendaos Oaraganm attula 1985 1» 4.6 - AimanseUca Pike EK» ludxts 1985 1 21 Kittilä JerisjSrvi Pike Esc* ludus 1980 2 45 (43 -47) Miiteflsh Cdrsoona lancetxm 1980 2 42 (30 - 53) Lfiustnjarvi Hhlteflsh Oregon* lararstus 1980 lk 21

Xkasjaxvi Piks EPQgr ItdtlS 1980 2 75 (68 - 82) Wiltsflsh Cbrvgonuv lmrarttm I960 2 78 (69 - 87) Roach Rutllis rutllus 1980 2 75 (67 - 82) Rovaniemen mlk Apukkajärvi Perch Fares flwlatilis 1985 1 13

Pike En ludus 1962 2 50 (46 - 51) Pike EKK lUCiXM 1984 2 22 (20 - 23) Pike EaoK hcim 1985 9 38 (23 - 51) thitefieh 1982 2 18 (14 - 22) Roach Putilm rutllup 1982 1 19 Roach Rutilm rutllus 1985 5 20 (9-40) KoLnikanta- jarvi (Meltaus) Hiitsfish Cbregcn* lavaraeut 1985 1 26 •the sample consists of many fishes ————————_— kths sanpie consists of many ens year old fishes grinded as such 53

Table BCOntinjed

Saarijärvi (MeltÄB) Fike Esat luclus 1965 3 49 (40 - 61) UUaijarvi (Meltaus) ItaKti Rutilus rutilus 1962 1 24

Sodankylä Porttipahta Miitefish Oaregans peled 1965 1 9.9 Utsjoki Tteno Salmon Salao salar 1965 1 2.1 Vanalohijärvi ftsrch Pena flurtaNTfs 1985 2 32 (28 - 35) 1985 1 12 54

Table X. Mean concetrations of 1J7Cs (Bq kg-1 fresh weight) in fish in Lapland froa 1980 to 1985. Ranges are given in parenthesis.

Fish species Year Number of of saapling samples lJ7Cs

Perch Perca fluviatilis 1985 24 (13 - 35)

Pike Esox lucius 1980-1985 21 42 (21 - 82)

Vendace Coregonus albula 1985

Hhitefish Coregonus lavaretus 1980-1985 8 40 (14 - 87)

Hhitefish Coregonus peled 1985 10

Salmon Salmo salar 1985 1 2

Roach Rut Hus rut Hus 1980-1985 9 32 ( 9 - 82)

Bream Abramis brama 1985 12 % Sfe

Table XI. Mean concentration of "T Cs (Bq kg -l fresh «eight) in berries froe Lapland 1980 to 1985. Ranges are given in parenthesis.

Tear Number of of sampling samples 137 Cs

Cloudberry

Kittilä 1980 38 (25 - 45)

Kemijärvi 1985 42

Blueberry

Kittilä 1980 3 16 (13 - 19) 1981 1 11

Cowberry

Kittilä 1980 6 12 (6 - 22) 1981 2 9 (7 - 12)

Pello 1982 11

Rovaniemen mlk 1982 2 6 (6,1 - 6,3) 57

Chapter 4

CESIUM 137 IN LAPPS IN WINTER 1986 Tua Rahola and Matti Suomela

ABSTRACT

From 1962 to 1977 total body cesium 137 measurements were made of a group of Finnish Lapps, by the Department of Radiochemistry at the using whole-body counting once or twice annually. At the beginning of 1986 it was decided that the Finnish Centre for Radiation and Nuclear Safety together with the Department of Radiochemistry would make measurements for the same Lapp group after an interval of almost ten years. The measurements were performed on April 5-8, three weeks before the Chernobyl accident, with a total of 88 Lapps participating. The aim was to re-estimate the internal do^>e from cesium-137 calculated in 1976 for one generation (1955-85) using the actual measured cesium 137 values from 1986,

The mean cesium 137 body burden for male reindeer herders from Inari was found to be 5200 Bq and for female reindeer herders 2800 Bq. The body burdens for Lapps from other areas were lower, the mean for all men being 3800 Bq and for all women 2000 Bq. On average the cesium 137 body burden in 1986 was 70 per cent of the corresponding body burden in 1976.

The inclusion of the results of these measurements in dose calculation did not alter the estimated internal effective dose equivalent of 13 mSv for one generation (1955 -1985) of reindeer herding Lapps. 58

1 INTRODUCTION

After the atmospheric nuclear bomb tests in the 1950s, '60s and '70s radioactive fallout was spread over the northern hemisphere. As a consequence 137Cs was transported via different foodchains to man. The cesium 137 body burdens detected in Finnish Lapps were higher than in the population in the south of Finland.2-4'5-6 This was due to the special foodchains in Lapland and not to differences in the amounts of fallout. Lapland is a cold, nutrient-deficient region lacking humus in the soil. Artificial radionuclides are efficiently enriched and the most efficiently cesium-enriching foodchain is that of lichen- reindeer - man.

The 137Cs body burdens of Finnish Lapps have been studied since 1961. The same group of Lapps was measured by whole-body counting once or twice every year from 1961 to 1976 and a somewhat smaller subgroup in 1977 by the Department of Radiochemistry at the University of Helsinki {HYRL). Using the results of these measurements the internal dose of cesium 137 for the Lapps was estimated in 1976 to be 12.5 mSv for one generation of Lapps or for the period 1955-1985.6 in 1985 plans were begun to measure the same Lapp group again after an almost ten year interval. At the beginning of 1986 it was -^ added that the Finnish Centre for Radiarion and Nuclear Safety (STUK) and the Department of Radiochemistry would cooperate in measuring the above Lapp group during the first week of April. Thus the measurements were fortunately done three weeks before the Chernobyl accident, which caused some radioactive fallout also in Lapland.1 The results are of great importance when evaluating the effects of the Chernobyl accident. The shadow shield whole-body counter 2 used by HYRL in earlier years could be installed in a new truck making it possible to use the same measuring geometry as before and to compare it with the geometry of the whole-body counter of STUK.7 59

The aim was to re-estimate the internal dose using the measurement results from 1936 instead of the values predicted in 1976. This paper presents the whole-body counting results of the Finnish Centre for Radiation and Nuclear Safety for 1986. The results of the Department of Radiochemistry, Tillander and Jaakkola, 1986 are presented elsewhere.10 Joint reports including results from 1987 were presented at the 7th international congress on circuit polar health at Umea, Sweden* and at the meeting of the Nordic Society for Radiation Protection at Mariehamn.11

2 MATERIAL AND METHODS

The composition of the Lapp group was described in several earlier publications.3-4 In 1986 all 103 persons belonging to this group were invited for measurements at Inari, northern Lapland, Fig. 1. They were asked to invite members of their families also to the measurements. Altogether 88 persons were measured, 66 of whom had belonged to the original group.

Two whole-body counters were used: the one, HYRL, used for earlier measurements now temporarily installed in a truck at the measuring location, and the other a whole-body counter of modified chair t;;•>*. IRMA 2, STUK, permanently installed in a truck end until fciien used mainly for measuring Internal contamination of vorkers at the Finnish nuclear power plants.7 The whole-body counter of HYRL as equipped with a Nai (Tl) detector of the acn-.a dimensions {12.5 cm x 7.5 cm) as in earlier measurements and IRMA 2, STUK, with its standard Nal (Tl) detector (20.2 cm x 10 cm) or with a high purity germanium detector (efficiency 27 %, energy resolution 1.95 keV for 60 Co 1.33 MeV). Before measurements were made each person changed into clean pyjamas without taking a shower. The measuring time was 1000 s. The minimum detectable 137Cs activity was for the smaller Nal (Tl) detector 100 Bq, for the larger one 40 Bq and for the semiconductor detector 50 Bq. 60

3 RESULTS

3.1 Body burdens of 137Cs

The *3 7 Cs body burdens are given for each individual in Table I. Subjects marked b were measured with the germanium detector and all others with a Nal (Tl) detector. Two subjects marked c were measured only in the HYRL counter. The highest mean 137 Cs body content, 5200 Bq, was found in male reindeer herders from Inari.. The women from Inari belonging to the same occupational group had on average 2800 Bq 137Cs or a little more than half the content of the men. The difference in activity content between males and females was smallest for occupational groups other than reindeer herders. In Table II the mean body burdens for each group are given. This table also presents the mean 1 ' 7 Cs body burdens for the same groups measured in 1976. It can be seen that the mean body burden in i.966 was still 70 per cent of that found ten years earlier. Fig. 2 shows the mean 137Cs amounts in male reindeer herders from Inari between 1962 and 1986. The mean 13T Cs body burden of this group in 1986 was 10 per cent of the corresponding burden, 55000 Bq, in 1965.

3.2 Internal dose from I37Cs

The whole-body counting results were used for estimating internal

137 cs clOSes (effective dose equivalents). The doses 1955 - 1976 were calculated using the method and data of Miettinen et ai.4-6 The activity time integral for the period 1977 - 1985, when no whole-body counting measurements were made, was calculated using the effective half-time obtained from the measurement results in 1976 and 1986. The total 137 Cs body dose for this period was estimated to be 1,4 mSv as a mean for male and female reindeer herders using the dose factor 4.9 x 10-3 mSv per (Bq 61 a (gK)-1 ) given by UNSCEAR 12 . Using the do3e estimate of Rahola and Miettinen 6 for the period 1955 - 1976 the total body dose for one generation of reindeer-herding Lapps (1955-1985) was estimated as 13 mSv. The total body dose was 0.12 mSv for this group in 1985 and 0.08 mSv for the whole group of Lapps for whom measurements were made.

4 DISCUSSION

The changes in 137 Cs body burdens from 1976 to April 1986 vary most for the Lapps in other occupation groups as can be seen from Table II giving the ratio of mean 137Cs body burdens in April 1986 and 1976. The living habits of these Lapps are more similar to those of other Finns and their reindeer meat consumption is not as regular as that of the reindeer herders. According to an investigation in Lapland in 1960-1964 a male reindeer herder might consume as much as 200 kg of reindeer meat per year.3 The same investigation showed that 70-90 per cent of the 13 7 Cs intake comes from reindeer meat consumed mostly during winter time. The mean consumption for Finns excluding Lapps is less than 0.5 kg per year.

The re-estimation of the internal dose from 137 Cs to the Lapps for the period 1955 - 1985 showed good agreement with the value 12.5 mSv estimated in 1976.

The total 13 7 Cs body dose for people in southern Finland calculated using whole-body counting results of the Helsinki reference group was estimated as 0.004 mSv in 1985.' The estimate for the period 1955 - 1985 was below 0.30 mSv or about 2 per cent of the total body dose of the reindeer herders.

From Norway a *37 Cs body burden of 3500 Bq was reported for a group of reindeer-breeding Lapps in 1983.n The corresponding body burden for a group of non-reindeer breeders was 2300 Bq in the same year. For the Norwegian reindeer breeders a total 62

average committed dose equivalent H,0 of 13 mSv until the year 2000 was estimated. This is in good agreement with the Finnish results.

The first slaughtering period of reindeer after the Chernobyl accident began at Inari in October 1986 until which time the 117 Cs in the reindeer meat consumed originated in fallout from the nuclear bomb tests. Thus the effects of the Chernobyl fallout on the 1J 7 Cs intake could only start appearing at the end of the year 1986. The first measurement series of the Lapps after the accident were performed in April, 1987.

REFERENCES

Arvela H, Blomqvist L, Lemmela H, Savolainen AL, Sarkkula S. Environmental gamma radiation measurements in Finland and the influence of the meteorological conditions after the Chernobyl accident in 1986. Report STUK-A65. Supplement 10 to Annual Report 1986 STUK- A55. Helsinki: Finnish Centre for Radiation and Nuclear Safety, 1987.

Hasanen E. The occurence of 1,7Cs in the biosphere evaluated with environmental and metabolic studies. Report Series in Radiochemistry 2. Helsinki: University of Helsinki, Department of Radiochemistry, 1972.

Jokelainen A. Diet of Finnish Lappa and its Caeslum- 137 and Potassium contents. Acta Agralia Fennica 1965; 103.

Miettinen J K, Jokelainen A, Roine P, Liden K, Naversten Y, Bengtsson G, Hasanen E, McCall RC. 137Cs and Potassium in people and diet - a study of Finnish Lapps. Annales Acadiae Scientiarum Fennicae. Series A II Chemica. 1963. 63

Rahola T, Tillander M, Jaakkola T, Miettinen JK. Body burden of l37Cs in Finnish Lapps in April 1976. Radioactive foodchains in the subarctic environment. Progress Report Aug. 15, 1975- Aug. 14, 1976.

Rahola T, Miettinen J K. Fallout levels of 137 Cs and some short-life nuclides in Finnish Lapland during 1966- 1976 in the foodchain lichen - reindeer - man. Radioactive foodchains in the subarctic environment. Progress Report Aug. 15, 1976 -Nov. 14, 1977.

Rahola, T, Suomela M. A mobile whole-body counter for measuring internal contamination at nuclear power plants. Proceedings of Third Internatiomal Symposium of SPR. Inverness, Scotland, 1982; 305-310.

Rahola T, Jaakkola T, Miettinen JK, Tillander M, Suomela M. Radiation dose to Finnish Lapps - Comparison of effects of fallout from atmospheric nuclear weapons tests and from the Chernobyl accident. 7th International Congress on Circumpolar Health, Umeä, Sweden, 1987. To be published in Arctic Medical Research.

Studies on environmental radioactivity in Finland 1984- 1985. Annual Report STUK-A54. Helsinki: Finnish Centre for Radiation and Nuclear Safety, 1987.

Tillander M, Jaakkola T, Activity measurements of Lapps in April 1986. Report to the Ministry of Trade and Industry. University of Helsinki, Department of Radiochemistry, 1987.

Tillander M, Rahola T, Suomela M, Jaakkola T, Rissanen K, Miettinen JK. Radioactivity in Finnish Lapps 1986 and 1987. Nordic Society for Radiation Protection, Mariehamn, Finland, 1987. 64

12 United Nations Scientific Committee on the Effects of Atomic Radiation. Ionizing Radiation: Sources and Biological Effects. New York: United Nations, 1982.

13 Westerlund E A, Bertelsen T, Berteig L. Cesium 137 Body Burdens in Norwegian Lapps, 1965 - 1983. Health Physics 1987; 52:2 : 171-177. 65

Fig. 1. Location of Lapps belonging to the whole-body counted group. The measurements were made at Inari. 66

1965 1970 1975 1980 1985

Fig. 2. Mean 137Cs body burdens (Bq) in male reindeer herders from Inari 1962 to 1986. 67

Table I. Oesium 137 and potassiun body contents of Lapps measured at Inari, April 5-8, 1986

Group/ Age Height Height 13,CS K HSHL* Subject No. 1976 1 1 a cm kg Bq Bq kg- Bq g- g g ng-i aj

INARI

U.1 inn '-f n In *m. *T_ [JUT.1 _n_ „ Mal Ae reindeer iwwia, ^* subjects/

3 66 157 61 2890 47.4 35.7 81 1.3 7810 18 43 164 61 2960 48.5 35.2 84 1.4 3330 19 38 171 80 6730 84.1 46.7 144 1.8 8660 124*» 39 171 72 2040 28.3 17.0 120 1.7 4440 38 37 167 82 3030 37.0 22.0 138 1.7 3370 120 46 170 80 10900 136.3 79.0 138 1.7 ~£ 119 34 168 64 7100 110.9 50.4 141 2.2 - 52 56 160 68 9620 141.5 69.2 139 2.0 11600 44 55 170 82 5180 63.2 36.2 143 1.7 10100 123 44 165 60 4550 75.8 33.0 138 2.3 - 53 47 164 72 5110 71.0 56.8 90 1.3 - 54* 51 164 80 11000 137.5 63.6 173 2.2 16200 56 56 169 72 3290 45.7 24.4 135 1.9 7510 68* 42 165 75 7030 93.7 40.6 173 2.3 12700 67" 52 157 73 7330 100,4 49.2 149 2.0 12100 69»» 49 165 63 7360 116.8 48.4 152 2.4 15200 65 61 168 67 4220 63.0 30.6 138 2.1 6590 66 55 165 75 5920 78.9 43.2 137 1.8 7840 108* 37 170 63 4550 72.2 35.0 130 2.1 - 84b 53 163 69 3400 49.3 45.9 74 1.1 6330 112" 38 177 77 3000 39.0 19.2 156 2.0 - 116 57 170 81 3030 37.4 24.8 122 1.5 3660 97" 74 161 52 1550 29.8 12.5 124 2.4 2740 98 72 172 57 2700 47.4 20.1 134 2.4 -

Mean 50 166 70 5190 73.1 39.1 131 1.9 8250 Minimum 34 157 52 1550 28.3 12.5 74 1.1 2740 Maximum 74 177 82 11000 141.5 79.0 173 2.4 16200

a Rahola et al, 1977 e not measured 1976 h measured with the germanium detector 4 measured only by HYRL 68

Table I Cöntirued

Group/ Age Height Weight K HYRL Subject No. 1976 a cm kg Bq Bqkgr1 Bqgr1 g g kg-1 Bq

INARI Male reindeer-herding fishermen, 10 subjects/

11 64 170 67 1590 23.7 17.9 89 1.3 2260 12 70 161 65 5220 80.3 62.1 84 1.3 5770 14 48 161 106 2660 25.1 18.3 145 1.4 2260 20 72 170 83 2070 24.9 24.4 85 1.0 _* 22* 67 170 81 2150 26.5 15.7 137 1.7 3630 43 74 166 64 4180 65.3 39.1 107 1.7 5700 Tjb 61 171 72 3150 43.8 19.6 161 2.2 2070 115 37 173 73 1550 21.2 14.6 106 1.5 - 126 36 173 82 3590 43.8 33.2 108 1.3 - 79 68 166 59 2040 34.6 26.8 76 1.3 1920

Mean 60 168 75 2820 38.9 27.2 110 1.5 3370 Minimum 36 161 59 1550 21.2 14.6 76 1.0 1920 74 173 106 5220 80.3 62.1 161 2.2 5770

INARI Male Lapps with other occupations, 4 subjects/

37* 60 158 65 2330 35.8 16.0 146 2.2 890 49» 47 166 71 480 6.8 5.3 90 1.3 2780 46* 67 165 57 1850 32.5 12.3 150 2.6 - 113 4* 166 70 4220 60.3 30.6 138 2.0 -

Mean 56 164 66 2220 33.8 16.1 131 2.0 1830 Minimum 47 158 57 480 6.8 5.3 90 1.3 890 Maximum 67 166 71 4220 60.3 30.6 150 2.6 2780

b measured with the germanium detector c not measured 1976 69

Table I Continued

Group/ Age Height Height «7 Cs K HYRL Subject Ho. 1976 1 1 1 a CM kg Bq Bq kg" Bq gr g g kg* Bq

INARI

Fenale reindeer herders, 4 subjects/

13 64 150 82 2410 29.4 28.4 85 1.0 6220 10*» 48 153 77 5110 66.3 85.2 60 0.8 8400 114 55 149 49 1550 31.7 15.3 101 2.1 _£ 103 34 156 50 2070 40.7 18.3 113 2.3 2520

Mean 50 152 65 2790 42.0 36.8 90 1.5 5710 Minimui 34 149 49 1550 29.4 15.3 60 0.8 2520 Maxima 64 156 82 5110 66.3 85.2 113 2.3 8400

INARI

Fenale reindeer-herding f isherwomen, 5 subjects/

1 64 150 75 1150 15.3 13.7 84 1.1 2740 2* 50 153 67 850 12.7 12.9 66 1.0 1220 9 64 156 79 2590 32.8 28.5 91 1.2 4550 57 58 150 66 740 11.2 8.8 84 1.3 1440 77 61 154 79 1180 14.9 14.9 79 1.0 2850

Mean 59 153 73 1300 17.4 15.8 81 1.1 2560 Minimum 50 150 66 740 11.2 8.8 66 1.0 1220 Maximum 64 156 79 2590 32.8 28.5 91 1.3 4550

h measured with the germanium detector ' not measurer? 1076 70

Table I Continued

137 Group/ Age Height Height Cs K HYRL Subject No. 1976 1 a cm kg Bq Bqkg-i Bggr 9 gkg-i Bq

INHU

c *- Feaale Lapps WITH crcner opcupatxma , 5 subjects/

36* 54 148 48 740 15.4 5.8 128 2.7 590 42 30 158 58 2960 51-0 36.5 81 1.4 590 76" 49 163 64 962 15.0 8.5 113 1.8 2520 83*> 73 152 46 1480 32.2 13.0 114 2.5 2400 93 54 148 75 1850 24.7 13.7 135 1.8 _C

Mean 52 154 58 1600 27.7 15.5 114 2.0 1530 Minijnum 30 148 46 740 15.0 5.8 81 1.4 590 Maximum 73 163 75 2960 51.0 36.5 135 2.5 2520

UTSJOKI Male reindeer herders, 12 subjects/

17*» 63 171 101 4070 40.3 23.3 175 1.7 4300 23" 37 165 83 1670 20.1 11.1 150 1.8 740 110* 25 170 60 1700 28.3 15.3 111 1.9 - 122 26 178 81 3140 42.5 24.9 138 1.7 - 117 36 173 78 4030 51.7 25.7 157 2.0 - 61 68 165 61 2150 35.2 25.6 84 1.4 5290 63 47 158 60 1780 29.7 16.3 109 1.8 - 121 20 178 76 2550 33.6 18.6 137 1.8 - 109»» 18 180 95 2850 30.0 31.7 90 0.9 - 72 50 166 76 6480 85.3 47.3 137 1.8 - 116 24 178 72 3700 51.4 24.5 151 2.1 - 91 38 163 73 3920 53.7 34.4 114 1.6 4660

Mean 38 170 76 3200 41.8 24.9 129 1.7 3750 Minimum 18 158 60 1670 20.1 11.1 84 0.9 740 Maximum 68 180 101 6480 85.3 47.3 175 2.1 5290

b measured with the gexmanium detector c not measured 1976 71

Table I Continued

Group/ Age Height Height 137CS K HYRL Subject No. 1976 a cm kg Bq Bqkg-i Bqg-i 9 g fcgr1 flq

UTSJOKI

Male Lapps with other occupations, 7 subjects/

4" 56 158 70 1070 15.3 8.4 127 1.8 1260 30* 59 157 64 810 12.7 7.3 111 1.7 1780 3* 49 167 64 1370 21.4 9.9 139 2.2 1000 40 50 170 66 2290 34.7 25.7 89 1.3 2440 49 68 169 67 1370 20.4 12.1 113 1.7 780 59»» 56 159 70 4140 59.1 34.8 119 1.7 ~c 107»» 48 170 78 1220 15.6 11.0 111 1.4 -

Mean 55 164 68 1750 25.6 15.6 116 1.7 1450 Miniflun 48 157 64 810 12.7 7.3 89 1.3 780 Maximcm 68 170 78 4140 59.1 34.8 139 2.2 2440

UTSJOKI

Female Lapps with other occupations, 8 subjects/

32?» 54 154 74 1700 23.0 14.8 115 1.6 1070 39 45 157 64 1670 26.1 18.8 89 1.4 1520 58* 39 152 70 1220 17.4 4.7 262 3.7 1040 60 61 150 63 2150 34.1 25.6 84 1.3 3590 106" 65 158 64 1330 20.8 15.8 84 1.3 - 78* 74 149 80 1260 15.8 12.4 102 1.3 3000 85 65 143 53 520 9.8 7.9 66 1.2 1370 101* 60 155 53 1740 32.8 45.8 38 0.7 -

Mean 58 152 65 1450 22.5 18.2 105 1.6 1930 Minimum 39 143 53 520 9.8 4.7 38 0.7 1040 Maximum 74 158 80 2150 34.1 45.8 262 3.7 3590

b measured with the germaniun detector '; not measured 1976 72

Table I Continued

Group/ Age Height Weight 137CB K HYRL Subject No. 1976 a cm kg Bq Bqkgr1 Bqg-1 g g kgr1 Bq

SEVETTIJÄRVI

Male Skolt Lapps, 3 subjects/

35" 43 172 64 5220 81.6 40.8 128 2.0 _c 28 79 158 66 3450 52.3 32.9 105 1.6 - 111 46 166 76 4440 58.4 24.1 184 2.4 -

Mean 56 165 69 4370 64.1 32.6 139 2.0 — Minimum 43 158 64 3450 52.3 24.1 105 1.6 - Maximum 79 172 76 5220 81.6 40.8 184 2.4 —

SEVETTIJÄRVI

Female Skolt Lapps, 6 subjects/

24 72 147 58 4110 70.9 54.8 75 1.3 3400 25 68 141 62 2110 34.0 15.6 135 2.2 2780 26 72 142 64 3770 58.9 49.6 76 1.2 2370 27 57 150 73 2410 33.0 17.5 138 1.9 - 41 73 148 41 2220 54.1 30.4 73 1.8 - 89 68 147 50 2630 52.6 19.9 132 2.6 2520

Mean 68 146 58 2880 50.6 31.3 105 1.8 2770

Minimum 57 141 41 2110 33.0 15.6 73 1.2 2370 Maximum 73 150 73 4110 70.9 54.8 138 2.6 3400

c not measured 1976 d measured only by HYRL "fa

Table II. Mean body burden of 137 Cs in Finnish Lapps in April 1986 and April 1976

Group Number STUK-86 HXRL-76 STUK-86 of HVRL-76 subjects

1986 Bq Bq BQ

INARI Men

Reindeer herders 24 5190 8400 0.62 Reindeer herding fishers 10 2820 3660 0.77 Lapps of other occupation 4 2220 780 2.85

Women

Reindeer herders 4 2/90 4030 0.69 Reindeer herding fishers 5 1300 2850 0.46 Lapps of other occupation 5 1600 2040 0.78

UTSJOKI Men

Reindeer herders 12 3200 5070 0.63 Lapps of other occupation 7 1750 2290 0.76

Women

Lapps of other occupation 1450 1330 1.09

SEVETTIJÄRVI, Skolt Lapps Men

Lapps of other occupation 4370 _ b

Women

Lapps of other occupation 6 2880 2740 1.05

All men 60 3750 5770 0.65 All women 28 1950 2440 0.80

Mean of men and women 88 2850 4100 0.70

a Rahola et al 1977 b not measured 75

Chapter 5

DOSE ASSESSMENT Leif Blomqvist, Olli Paakkola and Matti Suomela

1 INTRODUCTION

In the beginning of 1986, the fallout from nuclear weapons tests carried out in the past was decreasing, almost approaching the detectir n Iin., c. The total dose delivered in 1986 could be estimated to be less than 10 /iSv.

The accident in the nuclear power plant at Chernobyl on April 26 led to an extensive fallout in southern Finland during the first two wee^s of May- The external dose rate due to the fallout reached 5 ^Sv h'1 in some locations - an increase over normal background by a factor of 30-40. At the time the growing season was only beginning, and in the main fallout areas the ground was still frozen and partly covered with snow.

Comparison of this fallout with the world wide fallout from nuclear weapons t'ssts during 1945-1985 revealed that the amounts of radionuclides released in nuclear explosions were substantially higher than those from Chernobyl. However, the fallout of cesium 137 in Finland was nearly four times higher than that from nuclear tests (Table I). 76

Table I. The amounts released and average fallout of *°Sr and 13 7 Cs from nuclear weapons tests and from Chernobyl according to Supplement STUK-A57 and references 4 and 5.

Released radio- Average fallout nuclides in PBq in Finland (10ls Bq) kBq/nr2 137 9oSr "7 Cs »°Sr Cs

Chernobyl 1986 8 38- 0.2 10.7 Nuclear tests 1945-85 600 960 1.9 3.0

• According to measurements made in Europe, this figure is too low. The total release maj have been higher by a factor of 2 to 3.

The radionuclides released in nuclear tests were lifted up to the stratosphere, and were then deposited relatively evenly over the earth's surface. The radionuclides from Chernobyl were transported to Finland at a height of one to two kilometers and deposited by local showers very unevenly. Short-lived radionuclides, e.g. iodine 131, were found in Finland 100 to 1000 times more than after nuclear tests in early I960's. The short transport time, about 3-4 days, led to the high amounts of iodine 131 deposition In Finland from the Chernobyl accident.

Fig. 1 gives the distribution of cesium 137 in different in 1986. The amounts of cesium 134 in 1986 were about 50% of the amounts of cesium 137.

Because it was early in the growing season, food was only slightly contaminated by the short-lived radionuclides. Cesium 134 end 137 were the only radionuclides of concern in internal contamination. The concentrations of cesium 134 and 137 in agricultural products were substantially lower than could be estimated using the models developed during the period of fallout from the nuclear weapons tests. On the other hand, lakes were 77 contaminated quickly and the concentrations in fish, especially front small and nutrient-deficient lakes, were high.

The supplements of this Annual Report give the deposition and distribution of various radionuclides in our environment.

2 EXTERNAL RADIATION DOSE

According to calculated trajectories, the air masses containing th.3 radioactive material emitted during the first phase of the accident reached Finland on April 27, 19861 . This long-range transport occurred in the layer of 700-2000 m. In the absence of rain the radioactive material stayed in this layer, and no large indication of elevated dose rates at ground level was received at the beginning. The map of precipitation for the 24-hour period from April 27, 1986 at 08.00 am local time is presented in Supplement 10 to this report (STUK-A65, figure 5).. It shows two small areas where rainfall exceeding 3 mm, near the town of Kajaani in eastern central Finland. In fact, the observation that led to the first detection of the contamination later attributed to Chernobyl was made at the radiation monitoring station in Kajaani. A small but persistent increase in the dose-rate level was observed there in the evening of April 27, following a rain shower.

Subsequently, a rather extensive fallout situation was created in southern and central Finland, with external dose rates up to 5 /xSv h'1 . Analysis shows that the dose rates correlate quite well with the pattern of accumulated precipitation during the period April 27 - May 2, 1986 (cf. Supplement 10). 78

2.1. Dose from immersion in air

Due to the prevailing circumstances, external exposure through immersion in ground-level c." was of no significance, unlike the dose from radioactivity deposited on the ground.

Although the measurement of concentrations of radioactive noble gases in the environment is not carried out on a routine basis by STUK, it is obvious that, because of the height of the release cloud in this case, these gases had no significant effect on either external or internal doses.

2.2. Dose from deposition on the ground

Supplement 10 to this report presents a map of the external dose rate caused by the Chernobyl accident in the whole of Finland on October 1, 1986, when the population-weighted mean dose rate, regardless of shielding, was 0.051 fjSv.

Supplement 10 also presents daily dose rate recordings at a number of stations, froi.i which we may calculate the excess external dose in 1986. By performing the integration and dividing by the corresponding dose rate observed on October 1, 1986, a 1 mean ratio of 9800 (JJSV)/(/JSV h* ) was obtained, using the data from figures 3 a-d in Supplement 10.

This allows us to estimate the average external radiation dose from the Chernobyl fallout to the Finnish population in 1986. Using the UNSCEAR shielding factor of 0.3, we obtain

9800 x 0.051 x 0.3 - 150 juSv

Correspondingly, the external dose in the first year following the accident (May 1986-April 1987) was estimated at 165 /uSv. Figure 2 gives external radiation dose estimates for 1986 in different provinces of Finland. 79

3 INTERNAL RADIATION DOSE

3.1 Dose froa inhaled radionuclides

As indicated above, the radioactive material did not remain for long IT the ground-level air. This is confirmed by the records of the stations of the Finnish Meterorological Institute, which continuously measure the radioactivity of ground-level aerosols.2 The conclusion to be drawn from the results of their measurements is that, at most stations, there was hardly any occurrence of increased artifical radioactivity in ground-level air. The clearly highest activity levels were recorded at Nurmijärvi, 40 km north of Helsinki, in an area where the deposited activity was at an order of magnitude lower than the average for central Finland. An explanation would be that the station at Nurmijärvi is situated at 105 m above sea level, and thus strong vertical mixing can occur in the lower atmosphere, when air masses coming from the coast encounter a change in surface roughness.

.At Nurmijärvi there is a station of the Finnish Meteorological Institute and a high-volume air sampling station of STUK at the same location. The concentrations of various radionuclides in surface air at the STUK high-volume air sampling station following the Chernobyl accident are presented in Supplement 1 to this report (STUK-A56). By integrating the nuclide concentrations, and multiplying by the approplate inhalation dose factors, we estimated the effective dose equivalent through inhalation for Nurmijärvi to be 40 fjSv, of which 90% was due to iodine 131. The remainder was caused by other gamma-emit ting and beta-emitting nuclides, wbereas the inhalation dose from alpha-emitting transuranium nuclides was negligible.

Dy comparing the artificial total beta activity concentration at all eight Finnish Meterological Institute measuring stations from which records were available, we estimated that the ratio 80 of the population weighted mean inhalation dose to the dose at Nurmijärvi was 1:4. Thus the vaan effective dose equivalent from inhaled radionuclides s about 10 /zSv. This takes no account of the filtration effects of buildings.

3.2. Dose from food and water

As mentioned above, the fallout came to Finland at a time when the growing season had not yet begun. The soil was still frozen, and the country was partly covered with snow. Cows and other domestic animals were still indoors. All early vegetables in Finland were grown in greenhouses. Thus contamination of food by short-lived radionuclides was of minor importance.

Detailed data on the contamination of different foodstuffs are presented in supplements 3, 4, 5, 6, 11 and 12 (STUK-A58, A59, A60, A61, A66 and A67). The results for contamination of game meat and reindeer are given in supplements 7 and 8 (STUK-A62 and A63).

Several short-lived radionuclides were found occasionally in some wild leafy vegetables and mushrooms. Their contribution to the total intake is, however, minor. In milk, isotopes of radioactive iodine were found continuosly, during the first month. Although cows were kept indoors until May 26, the highest concentrations of iodine 131 were found during the first week of May. This is because cows were contaminated by inhaling air contaminated by radioactive iodine. Additionally, stored fodder also was partly contaminated with fresh fallout. The mean intake of 131 I via milk was estimated to be 230 Bq. The corresponding dose equivalent to the thyroid was estimated to be 0.1 mSv. The respective committed effective doser equivalent is 0.003 mSv.

In 1986 the mean annual intake of "Sr in milk was approximately 70 Bq. In other foods, its contribution was insignificant. The contribution of Chernobyl fallout to the amounts of »°Sr was also very small, representing roughly a 2C per cent increase 81 to the level remaining from the nuclear weapons tests. The dietary intake of 90 Sr as a whole was about 60 Bq in 1986. The committed effective dose equivalent from the strontium isotopes was calculated to be about 5 /JSV during the first year after the accident.

The radioactive isotopes l -: Cs and 137Cs were the main food contaminants. The amount of cesium 134 in 1986 was approximately 50 per cent of the amount of cesium 137.

The concentrations of radioactive cesium in various foodstuffs and water have been measured extensively after the Chernobyl accident. The surveillance programmes started at the beginning of the I9 60's were expanded considerably, both areally and temporally. An estimate of the intake of 137Cs with food and water is given in Table II.

Table II. The average annual intake of cesium 137 via food and water in Finland during 1986 arA May 1986-April 1987 according to the country-wide survey.

1986 May 1986 - April 1987 Bq Bq

Milk and milk products 3400 5600 Meat 1500 2700 Cereals 100 280 Fish 1400 2200 Water 70 110 Vegetables, fruits and berries 800 1200 Other 230 350 82

3.3. Dose based on the whole-body counter aeasureaents of people

The Internal radiation dose caused by gamma-emitting radionuclides was also calculated from the results of whole-body counter measurements. Of the nuclides from the fallout from nuclear weapons tests only I37 Cs could be detected in January- April 1986. The corresponding effective dose equivalent was approximately 1 fjSv.

The results of whole-body counter measurements performed after April 30 in 1986, together with dose estimates, are presented in supplement 9 (STUK-A64).

In May small amounts of 131 I were detected in the measurements of people living in Finland. The mean 131I amount in the thyroid was only about 100 Bq during the period April 30 - May 16; the highest value found was 500 Bq. The effective dose equivalents varied from 0 to 0.02 mSv but the small number of measured persons from the different fallout regions do not allow estimation of the mean 131 I dose for the whole population.

Curing May-December the subsequent measurements of the reference group indicated that the 134Cs and the 137Cs burdens were continuously increasing. The mean body burden of women and n;en in this group was 730 Bq for l34Cs and 1500 Bq for 137Cs at the end of 1986. The increase in cesium burdens continued curing tha first half of 1987.

In November a study was begun in which the people to be measured were selected using a stratified random sampling method. The purpose of the study was to find out the variation in the 134Cs and ll7C& levels In people living in different fallout regions. The mean body content of people living in the five fallout regions (see Fig. 1, Supplement 9) was calculated separately for children, women and men. The annual mean body content for 83 the whole population was 370 Bq for 134Cs and 820 Bq for l37Cs- The means were obtained by weighting the regional mean values by the number of population in the region and then by the proportion of children, women and men in the whole population.

The effective dose equivalent for I37Cs was estimated using the conversion factor of 4.9 x 10~* Sv per (Bq a (gK)'1 ) given by UNSCEAR and that for "4Cs by multiplying the dose factor for 137 Cs by the ratio of the ingestion dose factors for 134 Cs and "7 Cs given in the ICRP 30.

The mean effective dose equivalents for the whole population were 0.022 mSv for 134Cs and 0.036 mSv for 137Cs in 1986. The mean total dose delivered in 1986 was thus 0.06 mSv. As shown in the supplement 9 the mean doses varied from 0.03 mSv in regions 1 and 2, representing the lowest fallout, to 0.12 mSv in the region 5, representing the highest fallout.

For the calculation of the mean committed effective dose equivalents it was assumed that the daily intake of the cesium isotopes was constant from May 1986 to April 1987 and that the cesium body burdens increased continuously as a function of the constant intake rate. The annual mean body burden (Cs/K ratio) for the first year after the accident was calculated by multiplying the annual mean Cs/K ratio for the year 1986 by the ratio of the time integral of the activity in the body in 1986 to the total time integral of the activity in the body during the first year after the accident. The time integrals were calculated using the retention function given in ICRP 30 applying effective half-lives instead of the biological half- lives. The calculations were done separately for both cesium isotopes using the mean body burden (Cs/K) values weighted in the same way as in calculating the mean body content of cesium. Using the whole-body counting results from 1986, the mean committed effective dose equivalent from the cesium Isotopes in the body during the period May 1*86 to April 1987 was estimated at 0.15 mSv (0.06 mSv for 134Cs and 0.09 mSv for 137Cs). Of this dose 0.10 mSv was delivered during the first year after the accident. 84

The amounts of l111 in the thyroids of Finns returning froa Kiev at the end of April and at the beginning of May varied froa 0 to 20 kBq, and the corresponding effective dose equivalents froa 0 to 0.5 aSv. The aaounts of 1 Sl 1 «ere auch lower in Finns returning froa other parts of Eastern Europe. About 100 people belonged to this group (STUK-B-VALO 45).

4. RADIATION DOSE IN THE HIGH AND LOW FALLOUT AREAS

There are some special groups in Finland which are known -to be exposed to a higher degree than Finnish people in average.

As a result of the atmospheric testing of nuclear weapons the fallout level in Finnish Lapland was in the same level as in the rest of the country. After the Chernobyl accident Lapland was contaminated only slightly (cf. Supplement 8, STUK A-63). The contamination of food and people in Lapland is described in Chapters 3 and 4 of this report. The average internal effective dose equivalent of reindeer-herding Lapps in 1986 was calculated as 0.2 mSv on the basis of whole-body counter measurements.

The highest contamination was found in the province of Häme. The external dose is about double that of the mean annual dose of the country. People, especially fishermen, consuming fish almost daily can also be expected to have higher internal contamination. In 1986 the total dose in that province can be estimated as 0.6 - 0.7 mSv and in the first year, May 1986-April 1987, as 0.7 - 0.8 mSv.

Vegetarians' diet differs from the average Finnish diet. The contamination of vegetables, fruits and berries is, however, not highei than that of average food. The doses of vegetarians can thus be expected to be of the same level as the average doses of the whole population. 85

In the least contaminated parts of Finland, it can be estimated that the total dose will be below 0.1 mSv during 1986, and also during the first year. May 1986 to April 1987.

In Finland the regional differences in food contamination tend to lie equalized by our food processing and delivery system. Foods such as dairy products, meat products, grain etc. are processed in a few dairies, sausage factories, mills etc., and then transported through wholesale trade, all over Finland. It is thus mainly local fish, liquid milk and some wild products which cause uneven contamination through food.

5 EFFECTIVE DOSE EQUIVALENT COMMITMENT

In the second and subsequent years, the external and internal dose will be essentially due to the isotopes cesium 134 and cesium 137. The external radiation dose rate will decline as a result of weathering combined with radioactive decay. The effect of weathering of cesium 137 in soil was studied experimentally for soil types normally found in Britain by Gale, Humphreys and Fisher3. They derived the following reduction factor for an Infinite area source:

D(t) - 0.63 e - V + O-37 «" V

Here Xx and \z are the effective decay constants. The

corresponding "half lives" T1 and T2 are:

Cs-137 Cs-134 Tj 0.60 a 0.49 a

T2 21.7 a 2.0 a

The predicted external dose rate resulting fiom the Chernobyl fallout (a mixture of cesium 137 and cerium 134) for future years is shown in Figure 3. 86

The integral of the predicted external dose rate from the second year to infinity is 4.5 mSv, which multiplied by the shielding factor (0.3) gives 1.35 mSv. Adding to this the external dose in the first year (0.17 mSv), we estimate the total mean dose commitment from external radiation to be 1.5 mSv.

The prediction of the internal exposure in the second and subsequent years is subject to great uncertainty. However, based on experience from the long-term internal dose caused by nuclear weapons test fallout, and judging from the short term ratio of internal to external dose after the Chernobyl accident, the mean total external plus internal dose equivalent ccnunitment can be roughly estimated as 2 mSv.

6. DISCUSSION

Some factors reduce the total intake of radioactive substances through food and water.

The effect of food processing, e.g. meat, fish, vegetables and berries, is not taken into account in Table II. Also the import of fruits with a low content of radioactive cesium has a reducing effect.

In the consumption statistics, losses occurring when people are having meals are not normally taken into account. Thus in countries where food is available in abundance, losses in the form of uneaten meals may be significant.

The contamination of fresh-water fish with cesium 134 and 137 varied markedly. During autumn 1986 several recommendations were given to reduce the intake of large amounts of fresh-water fish in some areas. Information from these areas seems to support the view that reduction in the intake of cesium 134 and 137 through restriction on fish consumption did occur. A voluntary reduction in the intake of other contaminated foodstuffs also has decreasing effect on the ingesticr. dose. 87

During the summer and autumn of 1986 contamination of the population with radioactive cesium occurred more slowly than contamination of food products. One factor affecting on this was that food eaten by the population was partly from previous months, e.g. conserved meat.

Table III gives a summary of the Intake and internal doses via food and water of radionuclides during 1986 and May 1986-April 1987 after above discussed reducing effects have been taken into account. For cesium 137 a dose factor of 1.4 x 10~a Sv/Bq and for cesium 134 2.0 x 10~a Sv/Bq was used.

Table III. The average estimated annual ingestion of radionuclides via food and water during 1986 and May 1986-April 1987 in Finland and corresponding internal committed effective dose equivalent.

1986 May 86-April 87 intake dose intake dose Bq mSv Bq mSv

Cesium 137 4800 0.067 7900 0.110 Cesium 134 2400 0.048 3950 0.080 Others 0.005 0.010

Total internal dose 0.12 0.20 from food and water

The doses calculated using intake statistics of food and contamination data of different foodstuffs by radionuclides tend to be higher when compared to the whole body measurements (see Table IV). In 1986 doses recorded by whole-body counting are approximately half of those estimated on the basis of food measurements. 88

For the radiation protection of the population the information from foodstuff measurements is particularly important in a sudden fallout situation, because critical foodstuffs, such as milk, can be measured lepresentatively and very quickly. Even if the predicted doses are overestimates the knowledge of the activity levels and, correspondingly, the doses are important for immediate measures.

Whole-body measurements are more accurate than food survey for those individuals which can be measured. However, organization and completion of a comprehensive whole-body measurement survey is very time-consuming. The two methods thus are complementary to each other. In Table IV the lower estimates for ingestion dose are based on whole-body measurements and the higher on food survey.

6.1. Summary of doses

Table IV presents a summary of the estimated mean committed effective dose equivalents for 1986 and for the first year after the accident. Two estimates are given for the dose via ingestion, one based on measured radionuclide concentrations in dietary intake and the other based on whole-body counter measurements. 89

Table IV.A summary of estimates of the mean committed effective dose equivalent caused by the Chernobyl accident in Finland

Dose»» (mSv) in 1986 May 1986- April 1987

External radiation 0.15 0.17 Internal radiation - Via inhalation 0.01 0.01 - Via ingestion a) based on whole body measurements 0.10- 0.15- b) based on dietary 0.12 0.20 intake

Total 0.3 0.4

*' The dose refers to the external dose equivalent during the given period of time plus the committed effective dose equivalent from inhaled and Ingested radionuclides during the same period of time. 90

7 REFERENCES

The STUK- reports referred to are listed in the Foreword of this report

1 Savolainen A. L. et al. Dispersion of radioactive releases following the Chernobyl nuclear power plant accident. Report no. 1986:2. Helsinki: Finnish Meteorological Institute, 1986.

2 Kulmala A. and Mattsson R. Ilmatieteen laitoksen radioaktiivisuuden seurantajärjestelmä. Tshernobylin onnettomuuden alkuvaiheen havainnot. (Airborne Radioactivity Control System: Early Observations Following the Chernobyl Accident). Helsinki: Finnish Meteorological Institute, Air Quality Department, 1986. (in Finnish)

3 Gale H. J., Humphreys D. L. 0., Fisher E. M. R. Weathering of cesium- 137 in soil. Nature 1964; no. 4916: 257-261.

4 IAEA. Summary report on the Post-Accident Review Meeting on the Chernobyl Accident. Safety series No. 75-INSAG- 1. Vienna: International Atomic Energy Agency, 1986.

5 United Nations Scientific Committee on the Effects of Atomic Radiation. Sources and effects of ionizing radiation. New York: United Nations, 1977; UNSCEAR 1977 REPORT. 91

Figure l.The distribution of cesium 137 (kBq nr2 ) in different provinces of Finland in 1986. 92

Figure 2,The estimated external effective dose equivalent from the Chernobyl accident in different provinces of Finland in 1986. 93M

Dose rate

1 * Time (a)

Figure 3. The predicted population-weighted mean external dose rate in Finland after the Chernobyl accident. FINNISH CENTRE FOR RADIATION AND NUCLEAR SAFETY P.O.Box 268, SF-00101 HELSINKI, FINLAND Institute of Radiation Physics (SFL) 1958 - 1975 Institute of Radiation Protection (STL) 1975 - 1984 Finnish Centre for Radiation and Nuclear Safety (STUK) since 1st March 1984 Report code prefix letters (representing the acronym of the Finnish name of the institution) have been changed with the names of the institution. Report numbers continue in the original progressive series. SFL-A reports: SFL-A2 Castren, O. Gammaspectrometric determinations of caesium-137 and potassium in Finnish milk. Helsinki, 1966. SFL-A3 Paakkola, 0. Kadiostrontium in milk, grass and some other biological samples in Finland. Helsinki, 1966. SFL-A4 Salo, A. Strontium-90 and caesium-137 in water in Finland. Helsinki, 1966. SFL-A5 Castren, O. An Algol programme for the detection efficiences around a cylindrical scintillation cristal. Helsinki, 1966. SFL-A6 Suomela, M. The construction and calibration of the whole- body counter in the Institute of Radiation Physics. Helsinki, 1967. SFL-A7 Toivonen, M. On routine personnel dosimetry with fluoroglasses. Helsinki, 1967. SFL-A8 Studies on environmental radioactivity in Finland. Annual report. Helsinki, 1967. SFL-A9 Bagge, P. and Salo, A. Biological detectors of ra­ dioactive contamination in the Baltic. Helsinki, 1967. SFL-A10 Isola, A. A portable survey meter for low-level radia­ tion measurements. Helsinki, 1967. SFL-All Toivonen, M. and Isola, A. On the exposure of radiolo­ gical employees in Finland during 1965-1967. Helsinki, 1968. SFL-A12 Studies on environmental radioactivity in Finland 1967. Annual report. Helsinki, 1968. SFL-A13 Toivonen, M. An arrangement fcr read-out of luminescent dosimeters. Helsinki, 1969. SFL-A14 Kahlos, H. Radon-222 concentration of some water samples determine with gammaspectrometric measurements. Helsinki, 1969. SFL-A15 Asikainen, M. and Blomqvist, L. Measurements of airborne radionuclide in Finland with a hlghvolume air sampler and Ge(Li)-spectroscopy. Helsinki, 1970. 2

SFL-A16 Kahlos, H. and Suomela, M. Studies on the elimination rate and the radiation exposure following ingestion of radon-222 rich water. Helsinki, 1970. SFL-A17 Studies on environmental radioactivity in Finland 1968- 1970. Annual report. Helsinki, 1971. SFL-A18 Rannikko, S., Uotila, I. and Kiviniitty, K. Measure­ ments of radiation output of telecobalt units in Finland. Helsinki, 1971. SFL-A19 Kahlos, H. and Asikainen, M. Natural radioactivity of ground water in the Helsinki area. Helsinki, 1973. SFL-A20 Salo, A. and Saxen, R. On the role of humic substan­ ces in the transport of radionuclides. Helsinki, 1974. STL-A reports: STL-A21 Studies on environmental radioactivity in Finland 1971- 1975. Annual report. Helsinki, 1977. STL-A22 Bjarland, B. The Hytype printer as versatile output device in small NOVA configurations. Helsinki, 1976. STL-A23 Uotila, I. CAMAC extension for BASIC on the NOVA 1200 minicomputer. Helsinki, 1976. STL-A24 Asikainen, M. and Kahlos, H. Natural radioactivity of ground and surface water in Finland - Pohja- ja pinta- vesien luonnollinen radioaktiivisuus Suomessa. Helsinki, 1977. STL-A25 Rannikko, S. J. and Sinitsin, R. V. (ed.). Clinical dosimetry: proceedings of the Soviet-Finnish Cooperati­ ve Meeting on Clinical Dosimetry, 6-10 December 1976, Leningrad USSR. Helsinki, 1979. STL-A26 Studies on environmental radioactivity in Finland 1976- 1977. Annual report. Helsinki, 1979. STL-A27 Toivonen, M. Individual TL detector characteristics in automated processing of personnel dosemeters: correction factors as extension to identify codes of dosemeter cards. Helsinki, 1979. STL-A28 Bjarland, B. Microcomputer control of automated TL reader. Helsinki, 1979. STL-A29 Stenstrand, K., Toivonen, H., Rytömaa, T. Radiation- induced chromosome aberrations in human lymphocytes: dose-response relationships after Irradiation in vitro with 200 kV X-rays and 60-Co gamma rays. Helsinki, 1979. STL-A30 Toivonen, H. A flexible multipurpose model for normal and transient cell kinetics. Helsinki, 1980. 3 STL-A31 Toivonen, H. Transient cell kinetics. Applications of tracer techniques to cancer research and radiobiology. Helsinki, 1980. STL-A32 Studies on environmental radioactivity in Finland 1978. Helsinki, 1980. STL-A33 Rantanen, E. Calibration of neutron rem counters: discussion on different results obtained in two labora­ tories. Helsinki, 1980. STL-A34 Studies on environmental radioactivity in Finland 1979. Helsinki, 1981. STL-A35 Rannikko, S. Concept of the population mean malignancy dose. Helsinki, 1981. STL-A36 Rannikko, S., Heinämaa, R. Number of medical X-ray examinations, their distribution and doses to bone marrow in 1978. Helsinki, 1981. STL-A37 Rannikko, S. Problems concerning the assessment of the radiation dose to population as a result of X-ray examinations. Helsinki, 1981, STL-A38 Studies on environmental radioactivity in Finland 1980. Helsinki, 1961. STL-A39 Asikainen, M. Natural radioactivity of ground water and drinking water in Finland, Helsinki, 1982. STL-A40 Studies on environmental radioactivity In Finland 1981. Helsinki, 1983. STL-A41 Rajama, J., Rantavaara, A. Radioactivity in Finnish cereals from 1962 to 1980. Helsinki, 1982. STL-A42 Turai, I. and Toivonen, H. Radiohygiene of fission isotopes of iodine: experiments in rats and model studies in man. Helsinki, 1983. STL-A43 Servomaa, h., Toivonen, M, and Kiuru, A. Mailed TL. dosimeters for monitoring the output from diagnostic x-ray equipment. Helsinki, 1983. STL-A44 Servomaa, A. Significance of x-ray diagnostic quality assurance in terms of radiation impact to patients. Helsinki, 1983. STL-A45 Suomela, M. Whole-body counter studies in radiation protection and clinical research. Helsinki, 1983. STL-A46 Arvela, H. A Nordic intercomparison and evaluation of the detector responses to natural environmental gamma radiation. Helsinki, 1983. STL-A47 Studies on environmental radioactivity in Finland 1982. Helsinki, 1984. STL-A48 Studies on environmental radioactivity in Finland 1983. Helsinki, 1984. 4 STUK-A reports: STUK-A49 Tarvainen, M. and Riihonen.. M. Spent fuel measure­ ments at Loviisa nuclear power station. May, 1982. Helsinki, 1984. STUK-A50 Järvinen, H., Rannikko, S. and Servomaa, A. Report on the Nordic-Soviet meeting on standard and applied dosimetry. Helsinki 9-11 November 1983. Helsinki, 1984. STUK-A51 Arvela, H. and Winqvist, K. Influence of source type and air exchange on variations of indoor radon concentration. Helsinki, 1986. STUK-A52 Ekenstam, 6. af and Tarvainen, M. Independent burnup verification of BWR-type nuclear fuel by means of the !37Cs activity. Helsinki, 1987. STUK-A53 Järvinen, H., Rantanen, E. and Jokela, K. Testing of radiotherapy dosimeters in accordance with IEC specification. Helsinki, 1986. STUK-A54 Studies on environmental radioactivity in Finland 1984-1985. Annual report. Helsinki, 1987. STUK-A55 Studies on environmental radioactivity in Finland in 1986. Annual report. Helsinki, 1987. STUK-A56 Sinkko, K., Aaltcnen, H., Taipale, T. K. and Juuti­ lainen, J. Airborne radioactivity in Finland after the Chernobyl accident in 1986. Supplement l to annual report STUK-A55. Helsinki, 1987. STUK-A57 Saxen, R., Taipale, T. K. and Aaltonen, H. Radioactivi­ ty of wet and dry deposition and soil in Finland after the Chernobyl accident in 1986. Supplement 2 to annual report STUK-A55. Helsinki, 1987. STUK-A58 Rantavaara, A. and Haukka, S. Radioactivity of milk, meat, cereals and other agricultural products in Finland after the Chernobyl accident in 1986. Supplement 3 to annual report STUK-A55. He. sinki, 1987. STUK-A59 Rantavaara, A. Radioactivity of vegetables and mush­ rooms in Finland after the Chernobyl accident in 1986. Supplement 4 to annual report STUK-A55. Helsinki, 1987. STUK-A60 Saxen, R. and Aaltonen, H. Radioactivity of surface water in Finland after the Chernobyl accident in 1986. Supplement 5 to annual report STUK-A55. Helsinki, 1987. STUK-A61 Saxen, R. and Rantavaara, A. Radioactivity of fresh water fish in Finland after the Chernobyl accident in 1986. Supplement 6 to annual report STUK-A55. Helsin­ ki, 1987. 5 STUK-A62 Rantavaara, A., Nygren, T., Nygren, K. and Hyvönen, T. Radioactivity of game meat in Finland after the Chernobyl accident in 1986. Supplement 7 to annual report STUK-A55. Helsinki, 1987. STUK-A63 Rissanen, K., Rahola, T., Hiukka, E. and Alf than, A. Radioactivity of reindeer, game and fish in Finnish Lapland after the Chernobyl accident in 1986. Supple­ ment 8 to annual report STUK-A55- Helsinki, 1987. STUK-A64 Rahola, T., Suomela, M., Hiukka, E., Puhakainen, M. and Pusa, S. Radioactivity of people in Finland after the Chernobyl accident in 1986. Supplement 9 to annual report STUK-A55. Helsinki, 1987. STUK-A65 Arvela, H., Blomqvist, L., Lemm^lä, H., Savolainen, A-L. and Sarkkula, S. Environmental gamma radiation measurements in Finland and the influence of the meteo­ rological conditions after the Chernobyl accident in 1986. Supplement 10 to annual report STUK-A55. Helsin­ ki, 1987. STUK-A66 Hus, E., Sjöblom, K-L., Saxen, R., Aaltonen, H. and Taipale, T. K. Finnish studies on radioactivity in the Baltic sea after the Chernobyl accident in 1986. Supplement 11 to annual report STUK-A55. Helsinki, 1987. STUK-A67 Hus, E., Sjöblom, K-L., Aaltonen, H., Klemola, S. and Arvela, H. Monitoring of radioactivity in the environs of Finnish nuclear power stations in 1986. Supplement 12 to annual report STUK-A55. Helsinki, 1987, STUK-A68 Puhakainen, M., Rahola, T. and Suomela, M. Radioacti­ vity of sludge after the Chernobyl accident in 1986. Supplement 13 to annual report STUK-A55. Helsinki, 1987.