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Applied Radiation and Isotopes 66 (2008) 1768– 1774

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Applied Radiation and Isotopes

0969-80

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Ingestion doses in Finland due to 90Sr, 134Cs, and 137Cs from nuclear weaponstesting and the Chernobyl accident

A. Rantavaara �

Radiation and Nuclear Safety Authority (STUK), P.O. Box 14, FIN-00881 Helsinki, Finland

a r t i c l e i n f o

Keywords:

Atmospheric deposition

Consumption of food and water

Dietary intake of radionuclides

Fallout

Food processing

Radiation dose

43/$ - see front matter & 2008 IAEA. Publish

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+358 9 7598 8589.

ail address: aino.rantavaara@stuk.fi

a b s t r a c t

90Sr and 137Cs in domestic foodstuffs and water have been analysed in Finland since the early 1960s, and134Cs since 1986. Using data on radionuclide deposition levels, agricultural production, and the

processing and consumption of foodstuffs, the average intake and radiation dose from the ingestion of

these radionuclides have been assessed. The estimated committed effective dose from the ingestion of90Sr, 137Cs, and 134Cs in food and water for the period 1960–2005 is 2.2 mSv, and for the period since the

Chernobyl accident in 1986 it is 1.3 mSv.

& 2008 IAEA. Published by Elsevier Ltd. All rights reserved.

1. Introduction

Widespread deposition of artificial radionuclides in the north-ern hemisphere occurred due to atmospheric nuclear weaponstesting during the period 1945–1980 (NRDC, 2005) and theaccident at the Chernobyl nuclear power plant on 26 April 1986.Both events led to the radioactive contamination of domesticfoodstuffs, notably by 137Cs and 90Sr; and also with 134Cs(from Chernobyl only).

The rate of radiation exposure of humans due to the intake ofcontaminated food and water has changed over time due toradioactive decay, dietary changes, and environmental processes,which reduce the bio-available fractions of the deposited radio-nuclides in the soil. The dietary intake of radionuclides can beestimated from a knowledge of the activity concentrations infoodstuffs and of the human per capita consumption of food. Theradiation dose to humans from ingestion can be derived from thedietary intake, using appropriate dose conversion coefficients. Inthe event of an accidental release of radionuclides, this informa-tion can be used to determine the need for intervention action toprevent or reduce the exposure of the population.

This study summarises the time series of average annual percapita intakes of 90Sr, 134Cs, and 137Cs in food and the associatedradiation doses in the period 1960–2005. The main dietarysources of radioactive caesium and strontium are identified, theintegrated committed effective doses through the ingestion offood are assessed, and the intakes and radiation doses due toglobal nuclear fallout and the Chernobyl accident are compared.The study provides a baseline against which future events can becompared.

ed by Elsevier Ltd. All rights reser

In this study, only the average exposure of people to radiationvia intakes of food and water has been assessed; the exposures ofthose people most at risk due to their high intakes of foodstuffsand water are not assessed.

2. Material and methods

2.1. Deposition of radionuclides

Since measurements started in Finland in 1961, the annualdeposition of radioactive material from nuclear weapons fallouthas peaked during the spring and summer months. For this globalfallout, the total ground surface contamination has been esti-mated by means of integrated decay-corrected radionuclidedeposition up to 2005. The accumulated deposition of 90Sr(T1/2 ¼ 28.79 a)1 and 137Cs (T1/2 ¼ 30.07 a) from nuclear weaponsfallout peaked in 1966. The nationwide means were then1500 Bq m�2 for 90Sr and 2500 Bq m�2 for 137Cs (Salo et al.,1984). The accumulated 90Sr and 137Cs deposition between 1961and 1985 decreased towards the end of the period. At the end of1985, the accumulated deposition was 1100 Bq m�2 for 90Sr and1800 Bq m�2 for 137Cs. Nationwide estimates were based on theanalysis of monthly samples from 16 to 24 deposition collectionstations, and they also included estimates for the years 1955–1960(Salo et al., 1984).2

The Chernobyl accident caused a single peak (actually twopeaks within a period of two weeks) in deposited radionuclide

ved.

1 Half-lives of radioactive isotopes are from Chu et al. (1999).2 Activities of 90Sr and 137Cs deposited on Finland in 1961–1985 have been

published in the reports SFL-A4, 8, 12, 17, Annual reports STL-A21, 26, 32, 34, 38, 40,

and STUK-A54. See the titles of these and other reports listed in the footnotes in:

/www.stuk.fi/S research publications.

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activity in April–May 1986. Resuspended 90Sr, 134Cs and 137Cs oflocal origin were the main components of radioactive depositionin successive years after the initial deposition (Saxen et al., 1994).A gamma radiation survey of ground contamination was carriedout in 1986 and 1987 (Arvela et al., 1990). The Chernobyl accidentcaused nationwide, highly variable activity density of artificialradionuclides in Finland. The regional distribution of groundcontamination differed between volatile and non-volatile nuclides(Arvela et al., 1990).

The medium half-life nuclide 134Cs (T1/2 ¼ 2.0648 a) was notdetected in global fallout before the Chernobyl accident. InChernobyl fallout its activity was found to follow a constant ratioto the activity of 137Cs. The value of this ratio was 0.6 on 26 April1986 (Arvela et al., 1990). Using this ratio, which decreased overtime due to radioactive decay, the content of 134Cs in environ-mental and foodstuff samples was often used to differentiatebetween the 137Cs of Chernobyl origin and that from global fallout.The regional distribution of 90Sr differed from that of 134Cs and137Cs, showing highest activities in the main fallout area of othernon-volatile nuclides (Saxen et al., 1987; Arvela et al., 1990).3

2.2. Activity concentrations of radionuclides in foodstuffs

Foodstuff data have been collected by the Finnish Radiationand Nuclear Safety Authority (STUK) by means of a systematic,mostly nationwide, sampling programme since 1960. Measure-ments of 90Sr and 137Cs in Finnish milk (since 1960), in cereals forhuman consumption (since 1962), in vegetables and fruit (since1974), and in beef and pork (since 1976) were the basis forestimates of nationwide activity concentrations in agriculturalproducts until 1986. In spring and summer 1986, the pre-Chernobyl programme4 was extended and intensified to providedata for the analysis of dynamic changes in the radionuclidecontents of various foodstuffs, including fish and wild foodproducts from forests.5 The sampling volume peaked in theperiod 1986–1988, coinciding with the highest contaminationlevel in foodstuffs. The number of planned foodstuff samples ofknown origin collected after the Chernobyl accident reached15 000 by 2005. Before 1986, some hundreds of foodstuff sampleswere taken each year.

Laboratory analyses of foodstuff samples included the gam-maspectrometric determination of 134Cs, 137Cs, short-lived radio-nuclides, and 40K (Sinkko, 1981; Klemola and Leppanen, 1997).Radiochemical determination was carried out for 90Sr (and for 89Sras needed). Methods and quality control procedures are sum-marised in Rantavaara et al. (1994). The use of reference materialsand participation in intercomparison tests and, since 1998, inproficiency tests have been the tools for verifying the quality ofthe radioanalytical determinations. Since 1999, the FinnishAccreditation Service (FINAS) has accredited the competence ofSTUK in radiochemical and gammaspectrometric determinationsfor environmental, biological, and foodstuff samples according tothe standard ISO/IEC 17025.

The uncertainty in gammaspectrometric determinations(based on one standard deviation and including uncertaintyin the calibration) was usually about 5%. A level of less than

3 Deposition data for 1986–1990 and thereafter are published in the reports

STUK-A 57, 75, and 109 and in the Annual reports on Surveillance of Environmental

Radiation in Finland, series STUK-B-TKO.4 Description of sampling and radionuclide data for foodstuffs, deposition, and

surface water in 1960–1985 are published in the following reports of STUK: SFL-

A2, -3, -4, -8, -12, -17; STL-A21, -26, -32, -34, -38, -40, -41, -47, -48, and in STUK-

A54.5 Foodstuff and surface water data since 1986 are in the reports STUK-A58,

-59, -60, -61, -62, -77, -78, -94, -129, -170. A pdf file is available for the report no.

170 and thereafter. Since 1999 data are in the reports STUK-B-TKO. 1-7.

or approximately 5% uncertainty was achieved in the determina-tions of 90Sr.

The radionuclide content of foodstuff samples was mainlydetermined for the edible fraction of foodstuffs. For radionuclidedetermination, typical household peeling, cleaning, and otherforms of preparation of foodstuffs were applied. This practice alsonecessitated the determination of the form of foodstuff used.

Time-dependent activity concentrations of Chernobyl-derived137Cs in foodstuffs were derived from 134Cs local groundcontamination. The aggregated transfer coefficient (Bq kg�1 freshweight in foodstuff divided by deposited activity in Bq m�2) wasadopted as a tool for the comparison of the uptake of radioactivecaesium by foodstuffs in different production conditions and bythe stage of growth or harvest season. Using this time-dependentand site-specific coefficient, activity concentrations of 137Cs werederived for foodstuffs produced outside the sampling area. Theprocedure was applied to agricultural products and wild food-stuffs (Rantavaara and Haukka, 1987; Rantavaara et al., 1987;Rantavaara, 1990b).

Data were not available for all foods for all years and so it wasnecessary to use site-specific modelling and extrapolation tosupplement the measured values. In the period 1960–1975, theconcentration of 137Cs in beef was related to the concentration inmilk, and 137Cs in pork with cereals, using comparative evaluationbased on Nordic data from the 1960s (Hvinden et al., 1967). Forthe estimation of data for 137Cs and 90Sr in vegetables and fruituntil 1974 and in wild food products in the period 1960–1985, thetime series of deposited long-lived radionuclides, available since1961, were also used. For the estimation of the 137Cs concentrationin wild berries in the period 1960–1985 and occasionally incereals before 1980, algorithms and parameters of the ECOSYSmodel (Muller and Prohl, 1993) were used for estimating thetranslocation of deposited Cs and Sr. For edible mushrooms, thepost-Chernobyl mushroom data and accumulated deposition inthe period 1960–1985 were used. A survey of freshwater fish in1982 (Rantavaara and Saxen, 1985), moose meat in the period1979–1980 (Rantavaara, 1982), mushrooms in 1984, and 90Sr inwild foodstuffs in 19986 were also used.

2.3. Effect of food processing on the intake of radionuclides

In order to improve the correction factors for intake estimation,studies on food processing in the dairy and milling industries and inhouseholds were carried out (Rantavaara, 1990a). Reduction in themass of foodstuffs often occurs during preparation, i.e., before actualcooking. Correction factors for mass losses were derived forreported consumption rates given as product weights, as, forinstance, in the food balance sheets. This was done in co-operationwith experts close to the originators of the annual consumptiondata. For instance, the edible fractions of game meat were derivedfrom carcass weights for various types of game animals (Rantavaaraet al., 1987). The milling yield was considered in the study ofradionuclide losses during milling (Rajama and Rantavaara, 1983;Rantavaara, 1990a). The type and source of drinking water and thefraction of processed surface water were based on information onwaterworks and the water supply in Finland in the period1970–2004, and the trends in waterworks development in theperiod 1960–1969 (Finnish Environment Institute, 2006).

2.4. Consumption of foodstuffs

Data on the consumption of foodstuffs were mostly obtainedfrom balance sheets for food commodities (Ministry of Agriculture

6 Partially unpublished data.

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and Forestry, 2006) and hunting and fishing statistics(Finnish Game and Fisheries Research Institute, 2006; Nygren,2007), which give annual catches of fish and game accord-ing to the subareas of Finland. Per capita consumption rateswere defined for each type of foodstuff, using the ediblefraction of each foodstuff, and they were used as adult foodintakes.

2.5. Calculation of dietary intake of radionuclides

Nationwide production-weighted means of activity concentra-tions were calculated for each year in the period 1960–2005 for allfoodstuffs or groups of foodstuffs in the diet and used to estimatethe per capita intake. For 137Cs in wild berries and mushrooms, thelocal origin of products picked for ‘own use’ was assumed inaccordance with the results of Markkula and Rantavaara (1997).Nationwide mean concentrations of 137Cs in freshwater fish wereevaluated according to fish species and lake type, taking 137Cscontamination of catchments and regional catches of fish intoaccount, as described in the reports of primary data7 and by Saxenand Sundell (2006). For Baltic herring and other marine fish fromthe Baltic Sea,8 activity concentrations of 90Sr and 137Cs wereaveraged for each year and the missing values in the 1960s orearly 1970s were derived through extrapolation. Samples ofcultivated salmon and rainbow trout were occasionally analysedfor 137Cs.

The human intake (I) of a radionuclide (i) from foodstuff (f)during a given time period was calculated using the equation:

Ii ¼ Sfðcf ;imf pf ;ie

� ln 2tf =Ti Þ

where cf, i is the mean activity concentration of radionuclide i

in foodstuff f in Bq kg�1 fresh weight during the period ofintake; mf is the mean consumption of foodstuff f (revisedfor inevitable mass reduction before actual cooking) by anindividual during the period of intake (kg); pf, i, (p1) is thecorrection factor for losses of radionuclide i during the process-ing of foodstuff f; tf is the delay (in days or years) in theconsumption of foodstuff f after the date of harvest or production;Ti is the half-life (in days or years) of radioactive decay ofradionuclide i.

For the estimation of the intake of 134Cs, its ratio to Chernobyl-derived 137Cs in ingested food and water was applied. The share of137Cs originating in global nuclear test fallout was first subtractedfrom the intake of total 137Cs for each type of food. In this way, theuncertainty in the 134Cs content of diet arising from themeasurements of individual samples of foodstuffs could beminimised.

In 1986, the new radionuclide contamination was averagedfor May–December, when intakes due to daily consumption ofdrinking water and foodstuffs were estimated. For wild foodstuffs,the annual harvest as a whole was considered in the assessmentof intake.

Delays in the consumption of crops, milk, and meat afterharvest or production were determined from the foodindustry and food market. Particularly for cereals, accurateknowledge of the time when the new harvest begins to bemarketed was important in assessing the content of long-livedradionuclides for the years 1986 and 1987. The relative proportionof imported fruit, fish, and occasionally cereals was alsoconsidered.

7 Data on fresh water fish are published in the reports STUK-A61, 77, 94, 129,

and 170.8 Data for Baltic fish are published in the reports STUK-A 66, 67, 79, 82, 90, 92,

102, 121, 157, 192, 205, and 218.

2.6. Calculation of radiation doses from ingestion of

radionuclides in food

Committed effective radiation doses were calculated for adultwomen and men by multiplying the annual intake of eachradionuclide by the age-dependent ingestion dose coefficientsfor adults. The applied coefficients (in Sv Bq�1) were 2.8�10�8 for90Sr, 1.9�10�8 for 134Cs, and 1.3�10�8 for 137Cs (IAEA, 1996).

2.7. Uncertainty associated with the estimation of dietary

intake and ingestion dose

Uncertainty in the estimate of the dietary intake of 137Csassociated with radionuclide analysis and sampling was com-posed of uncertainties in the fractions of intake from allsignificant foodstuffs consumed. They were based on themethodology and simulations used for the data of the first fiveyears after the Chernobyl accident (Rantavaara et al., 1996). The95% confidence intervals of the annual means for per capitaintakes and doses of this study were approximated as 10%(lower boundary) and 15% (upper boundary), at most. Thesevalues, based on post-Chernobyl data, may overestimate theuncertainties for the last 10 years of the period 1960–1985, but areconsidered appropriate for the whole pre-Chernobyl period, sincemodelled and extrapolated data were used for the years ofmaximum dietary intake of 90Sr and 137Cs in the 1960s.

A slight overestimation of intake may arise from the assumedreduction in the consumption of wild foodstuffs. Blomqvist et al.(1991) reported concern among people over the safety of localwild foodstuffs, but, in fact, only 4% of respondents had changedtheir diet. Another source of overestimation, not considered in thisstudy, may be associated with the wastage of edible food (at mosta few percent on average).

3. Results and discussion

3.1. Dietary intake of 90Sr, 134Cs, and 137Cs

Annual intakes of 90Sr and 137Cs for adults in the period1960–2005 are given in Figs. 1–3 according to the type offoodstuff, i.e., for milk products, meat and eggs, cereals, vegetables(including potatoes) and fruit, drinking water, fish, wild terrestrialfoodstuffs (berries, mushrooms, game meat), and reindeer meat.The time series of per capita intakes of 90Sr and 137Cs from varioustypes of foodstuff show the different effect on the contaminationof the human diet of the delayed stratospheric deposition ofglobal fallout as compared with the low annual deposition afterthe Chernobyl accident. The ratio of the sums of annual intakes(Bq a�1) and annual deposits (Bq m�2) shows that the dietary137Cs per unit deposition during the period of global fallout wasmore than four times higher than that in the post-Chernobylperiod, mainly because of the different deposition patternsassociated with the two contaminating events.

The intake of 90Sr and 137Cs associated with food of terrestrialorigin was significantly higher than that due to fish and water. Inthe period of global fallout, 85% of dietary 90Sr and 92% of 137Cscame from foods of agricultural or wild terrestrial origin, andreindeer meat, while after the Chernobyl accident the fractionswere 87% for 90Sr and 70% for 137Cs. The contribution of milk was51% to the intake of 90Sr and 46% for 137Cs during the period1960–1985. In this period cereals contributed 26% of the intake of90Sr. In the period 1986–2005, 42% of the intake of 90Sr and 23% of137Cs was due to milk, and 8% of 90Sr and 0.8% of 137Cs was due tocereals. The reduced consumption of these foodstuffs has alsoreduced the intake of radionuclides over the time considered.

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Bq

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Year of productionMilk products Meat and eggs Cereals Veg.& fruit, potato Water

Fig. 1. Per capita intake of 137Cs (Bq d�1) from foodstuffs of agricultural origin and water in 1960–2005.

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Fig. 2. Per capita intake of 137Cs (Bq d�1) from wild foodstuffs in 1960–2005.

A. Rantavaara / Applied Radiation and Isotopes 66 (2008) 1768–1774 1771

The availability of 90Sr for uptake by plants declined moreslowly than for 137Cs (Figs. 1 and 3) due to the poor fixation ofstrontium cations in mineral soils. The faster decline of 137Cs inagricultural products is due to the dominance of fine mineral soilsand clay, which have a capacity for the irreversible fixation ofcaesium. Drinking water was not negligible as a source of 90Sr inthe 1960s. 90Sr was transferred from runoff waters through a thicklayer of soil to the water of ring wells, which were then commonin sparsely populated areas. Strontium is known for its lowtransfer to muscle tissue and this is also true for the meat ofdomestic and wild animals.

Comparison of the dietary sources of 137Cs due to global falloutand to the Chernobyl accident (Figs. 1 and 2) also emphasises therelatively high contribution of fish to the intake of 137Cs in the

post-Chernobyl period; it amounted to almost 30%. Direct foliarcontamination of plants was not significant in the years followingthe single contaminating deposition in spring 1986 as particletransport due to local resuspension declined to an insignificantlevel within a few years (Saxen et al., 1994). The lower relativecontribution of terrestrial foodstuffs to intake after the Chernobylaccident is explained by the gradually declining transfer ofradioactive caesium from agricultural soils to plants. However,the contribution of wild berries, mushrooms, and game meatincreased from 7% during the era of global fallout to 30% in thepost-Chernobyl period. Part of the change was caused by theincreased consumption of moose meat, but more significant wasthe high root uptake of caesium by forest plants in conditions oflow annual deposition of 137Cs.

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Milk products Cereals Veg. & fruit, potatoAll fish Wild food, meat, eggs Water

Fig. 3. Per capita intake of 90Sr (Bq d�1) from foodstuffs and water in 1960–2005.

Table 1Average committed effective dose from ingestion of 90Sr, 134Cs, and 137C in food and

water in Finlanda

Radionuclide 1960–1985 1986–2005 1960–2005

90Sr 0.20 0.04 0.24134Cs 0.30 0.30137Cs

Chernobyl origin 0.90 0.90

Global fallout 0.68 0.06 0.74

Total 0.9 1.3 2.2b

a The 95% confidence intervals of the doses, given as lower and upper

boundary, are less than or equal to 10% and 15%, respectively (Cf. Section 2.7).b When the whole period of global fallout in northern hemisphere is

considered, an approximate dose of 0.3 mSv from ingestion of 90Sr and 137Cs in

1955–1959 has to be added.

A. Rantavaara / Applied Radiation and Isotopes 66 (2008) 1768–17741772

Reindeer meat (Rissanen et al., 2003; Leppanen et al.,2007) was included in the nationwide intake assessment,although it is mainly consumed in the northernmost parts ofFinland. Reindeer meat contributed 16% to the intake of137Cs in the period 1960–1985 and only 4% during theperiod 1986–2005. The reindeer herding area in Finland is in thenorth, i.e., in the least contaminated part of Finland afterthe Chernobyl accident, which explains the low contribution tointake since 1986.

The low surface density of 90Sr deposited in spring 1986produced a detectable, but low, signal in the diet in Finland(Fig. 3). Since 1986, the main part of dietary 90Sr has originatedfrom global stratospheric fallout.

Consumption trends for some foodstuffs have had a consider-able effect on the time series of intakes. Intakes of 90Sr and 137Csas a result of the consumption of these foodstuffs partially maskthe radioecological processes that also contribute to temporalchanges in intakes (Figs. 1–3). Since 1960, the decline in theconsumption of milk and rye has been considerable (about 50%),and also for wheat (about 25%). On the other hand, consumptionhas increased for pork and vegetables (both doubled), poultry, andgame meat. Consumption of game meat, mostly moose meat, hasincreased from 0.3 to almost 2 kg a�1 since 1960. In all, these non-linear changes have delayed the reduction in the dietary intake of90Sr and 137Cs since the early 1960s and after the Chernobylaccident.

3.2. Effect of environmental factors on dietary intakes

By the mid-1960s a rather clear picture of the food chainmechanisms of dietary 90Sr and 137Cs had been obtained in severalcountries as a result of the systematic analyses of milk and otherfoodstuffs and the data on deposited radionuclides (UNSCEAR,1966). The hypothesis of a constant ratio between the activitycontent of 90Sr in milk and the total diet per gram of calcium wastested and seemed to be accurate, e.g., in the United Kingdom(Bruce et al., 1977). However, due to the non-negligible fractionsof cultivated organic soils and coarse mineral soils, the 90Sr and

137Cs contents of the Finnish diet were higher than in temperatezones on average and this was also true for the ratios of diet tomilk (Castren, 1977).

3.3. Radiation doses from ingestion of radionuclides in food

The committed effective per capita dose from the ingestion of90Sr and 137Cs in food and drinking water over the period1960–1985 was 0.9 mSv, and over the period 1986–2005, it was1.3 mSv (including 134Cs) (Table 1). The temporal changes in dosesfrom ingestion (Fig. 4) do not differ much from the trends indietary intake (Figs. 1–3). The annual per capita doses from theingestion of 90Sr and 137Cs since 1960 were at their highest(0.11 mSv) in 1963 and 1964; since spring 1986 they were at theirhighest in 1987 (0.26 mSv) (including 134Cs) (Fig. 4).

Concerning the other significant radiation dose pathway, theexternal dose rate from surface deposition after the Chernobylaccident was 0.15 mSv a�1 at its peak in 1986, and had declined tothe same level as the annual committed dose from ingestion,about 0.02 mSv a�1, by 2005. In the period 1984–1985, and in a

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Fig. 4. Annual doses from ingestion (mSv a�1) of 90Sr, 134Cs, and 137Cs in food and water in 1960–2005.

A. Rantavaara / Applied Radiation and Isotopes 66 (2008) 1768–1774 1773

few preceding years, the annual effective dose from 137Csdeposition was 0.007 mSv a�1 (Blomqvist, 1987), equal to theannual committed dose from ingestion of 137Cs assessed in thisstudy for those years.

4. Conclusions

Dietary intakes and radiation doses via ingestion were assessedfor the Finnish adult population as a result of the nuclear weaponstesting of the 1950s/1960s and the Chernobyl accident in 1986that led to the contamination of foodstuffs with artificial radio-nuclides. The ingestion pathway was analysed for 90Sr and 137Csoriginating from both events and, in addition, for 134Cs from theChernobyl accident. The analysis was based on data from asystematic programme of sampling and analysis for foodstuffs anddeposition, as well as data on food production, supply, andconsumption. The estimated per capita committed effective dosefrom food intake was 0.9 mSv over the period 1960–1985 and1.3 mSv from the intake of food in the period 1986–2005.

The time series for annual intakes and doses from ingestiondemonstrate the significance of environmental processes. Thefoliar contamination of plants grown outdoors contributedsignificantly to the activity concentrations of foodstuffs ofterrestrial origin during the period 1960–1985, and terrestrialagricultural pathways dominated the dietary intake of 90Sr and137Cs until 1985. Since 1986, terrestrial wild foods and the aquaticpathway (the ingestion of fish) have dominated the human intakeof 134Cs and 137Cs.

Acknowledgement

Discussions on radionuclide deposition and aquatic pathwayswith Ritva Saxen, senior scientist of STUK, have been of great value.

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