FOOD CONSUMPTION SURVEY IN AOMORI PREFECTURE

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1 FOOD CONSUMPTION SURVEY IN AOMORI PREFECTURE T. IYOGI 1 1 Institute for Environmental Sciences, Rokkasho-mura, Aomori Japan INTRODUCTION First large-scale commercial nuclear fuel cycling facilities in Japan are under construction in Rokkasho-mura, Aomori Prefecture. A uranium enrichment plant, a low-level radioactive waste disposal center and a high-level radioactive waste storage facility are already in operation. A fuel reprocessing plant is now under construction planned for completion early next century. Probable release of radionuclides from these facilities is of large concern to people around the site. The radiation doses due to radionuclides release were assessed, prior to the construction of these facilities. Internal radionuclide doses of the population around the site are largely derived by ingestion. The intake of radionuclides through ingestion depends strongly on the eating habit of the population. Therefore, the local eating habit in the area around the site is important factor for the dose estimation of radionuclides from the facilities. Ohmomo (1974) surveyed the food consumption in the population in the coastal area of Ibaraki Prefecture where Japanese first fuel reprocessing plant is located. They found that the fishery workers were the critical group for evaluation of the internal dose, and that reported the consumption of seaweed (a critical food) among them was significantly higher than the national average. This implies that site-specific food consumption is an important sociological parameter for realistic radiation dose assessment. This study aimed to collect sociological data in relation to the estimation of radiation dose by radionuclides released from the facilities. Food consumption of individuals surveyed with questionnaire in Aomori Prefecture over a four years period ( ) is presented Rokkasho in this paper. METHOD Japan Sea Nuclear Fuel Cycle Plants (JNFL) Lake Ogawara Food consumption in individuals ( 3 5 years of age) in Aomori Prefecture was surveyed using a questionnaire over 4 years, from 1991 to 1994, a quarter of area each year (Fig. 1). Two hundred families in total were selected as the subjects of this survey, representing three types of Pacific Ocean Lake Towada South Nanbu area (1991) South Tsugaru area (1992) North Tsugaru area (1993) Shimokita Peninsula area (1994) Fig. 1 Survey areas for food consumption. the 1

2 Table 1 Number of families surveyed. Sea Fishery Farmer Other worker Lake and pond Agriculture Office Selfsupport Total South Nanbu area South Tsugaru area North Tsugaru area shimokita Peninsula area Total householders occupations: fisheries, farmer and other workers. The number of families within each occupation category is shown in Table 1. A questionnaire was delivered to the family to be completed with the answers on the status of food consumption of all family members over 3 days. The survey to one family was repeated four times a year seasonally to know seasonal variation. Completed questionnaires were compiled and analyzed according to the method previously applied to Ibaraki Prefecture by Ohmomo (1974)(1). The raw (wet) weight of the edible part of foods except for rice was used for the calculation of consumption rates. Both the water content of foods and the disposal ratio in cooking were taken from values in the literature (2) when only the dry weight was available from the questionnaire. Since rice is generally available as air-dried polished rice, the air-dried weight was used for rice. School lunches for young persons and off-home dishes were excluded from the calculations, because of insufficient information on food composition in the questionnaires. Processed foods were categorized as they were, unless further classification of the contents was available. Individual consumption rate of a foodstuff was calculated for each family member, based on the total consumption in one family divided by the number of members who actually ate the food concerned. The food consumption by the members younger than 5 years of age was not taken into account, because its contribution seemed to be insignificant. This may, therefore, cause overestimation of food consumption in adults in some extent. RESULT AND DISCUSSION Average consumption rates of food groups in Aomori Prefecture are shown in Fig. 2. Proportions of surveyed households by each occupation are different from those in Aomori Prefecture. Therefore, average consumption rates in whole Aomori Prefecture were calculated as means weighted with proportions of householder occupation in the prefecture. The weighted mean daily food consumption rate was 2,117 g d -1 p -1. The average consumption rates of marine, agricultural, livestock products and other foods were 204, 1,216, 373 and 325 g d -1 p -1, respectively. The contribution of agricultural, livestock and marine products to the total consumption was 57, 18 and 10 %, respectively. The consumption rates classified by occupation and the survey area in Aomori Prefecture are shown in Fig. 2. The highest total consumption of 2,297 g d -1 p -1 was observed in farm workers families, followed by 2,203 and 2,080 g d -1 p -1 in fishery and other workers families, respectively. Since the proportion of householders occupation for the each survey area in the prefecture was not available, results for the each area are shown as means of obtained data. The consumption rate in Northern Tsugaru area was the highest, and that in Sanpachi- Kamikita 2

3 Others Aomori Prefecture Weighted mean* By occupation Fishermen Farmer Other workers Sanpachi-Kamikita area** Southern Tsugaru area** Northern Tsugaru area** Shimokita Peninsula area** Consumption rate (g d -1 p -1 ) Fig. 2 Comparison of food consumption among families by occupation and area in Aomori Prefecture. * weighted by proportion of families by occupation in Aomori Prefecture. ** unweighted. Table 2 Results of statistical test of food products consumption in Aomori Prefecture. By types of families Products Other foods Total By area Other workers < Farmer Other workers, Farmer< Fishermen* Types of families Statistically significant Fishermen < Farmer Fishermen Farmer Other workers 1<3 1*,2<3 2<3 1<2 1>3 Other foods 1<2*,3*,4 1<2 Total 1*,2<3 1<2 Mean 1*,2,4<3 1*,2<3 1<2*,3*,4 1*,2<3 area was the lowest. Results of statistical test for the difference of food consumption in Aomori Prefecture were shown in Table 2. The consumption rate of marine products was the highest in fishery worker families among three groups by occupation, and these differences were statistically significant. Farmer families consumed larger amount of agricultural products in comparison with fisherman families. The consumption rate of marine products was higher in Northern Tsugaru area than the other area. That of agricultural products was higher in Northern Tsugaru area than that in Sanpachi-Kamikita and Southern Tsugaru area. Other foods consumption rate was lower in Sanpachi-Kamikita area than the other area. Representative foods with high consumption rates in the prefecture were a) rice, Japanese radish, apple and cucumber in agricultural products, b) squid, salmon and wakame (seaweed) in marine products c), milk, not significant (p ÅÉ0.05) 1 Sanpachi-Kamikita area 2 Southern Tsugaru area 3 Northern Tsugaru area 4 Shimokita Peninsla area Åñ p ÅÉ0.01 3

4 Table 3 Difference of calculation method between present study and national nutrition survey. This work National nutrition survey Re-calculatinon Age of subjects ÅÜ5 y-old ÅÜ1 y-old ÅÜ1 y-old Number of family menber who ate food items Number of family member who actually ate the food item Number of family member who were around table Number of family member who were around table Weight of dry food Equivalent fresh weight Dry weight Dry weight Weight of rice Air dried weight Cooked weight Cooked weight Eating out Excluded from the calculation Using typical value Mean value for meal in home School lunch Excluded from the calculation Average value of meal school lunch Mean value for meal in home Others This work weighted mean* farmer Non-farmer NNS Japan Tohoku Area farmer (Japan) Non-farmer (Japan) Consumption rate (g d -1 p -1 ) Fig.3 Re-calculation results of food consumption in Aomori Prefecture by using the calculation method based on the national nutrition survey. NNS indicates data from the national nutrition survey ( )(3-6). * weighted by proportion of householder's occupation in Aomori Prefecture. gg and pork in livestock products and d) tofu (soybean curd) in processed foods. A nation-wide food consumption survey is carried out every year by the Ministry of Health and Welfare in Japan to estimate the nutrition condition of people (national nutrition survey, NNS hereafter). The data compile method of the present study is different from that of the NNS, as summarized in Table 3. The daily consumption rate from this survey was re-calculated by using the method according to the NNS. Re-calculation results in Aomori Prefecture and data from the NNS (3-6) for comparison are shown in Fig. 3. The mean daily food consumption rate in the prefecture was 1,491 g d -1 p -1, and approximately 10% higher than the nation wide average of 1,344 g d -1 p -1. Consumption rates of rice, vegetables and fish were higher in the prefecture than the national average. According to the NNS results, the consumption rate depended on area and occupation. Aomori prefecture located in Tohoku area, and the food consumption rate in the area was 1403 g d -1 p -1. The result of this study in Aomori Prefecture is 4% higher than the value in Tohoku area. Occupation of subjects was classified into farmer and non-farmer in the 4

5 Table 4 Comparison with the values of food consumption in an application form of the reprocessing plant to the government. ( g d -1 p -1 ) This work (Shimokita Peninsula area) Safety assessment Mean Maximum in the individual family Fish (48) 255 Seaweeds (29) 141 Shellfish (10) 41 Cephalopod (34) 183 Crustacea (7) 32 Leaf vegetables (46) 216 Root vegetables (56) 310 Rice (79) 447 Milk (152) 551 Beef 6 19 (20) 106 Standard deviation in parentheses NNS, and the consumption rate of farmer was higher in comparison with non-farmer. When we also classified our data in such manner, the same trend was shown (Fig. 3). Food consumption rates that were used for safety assessment of the reprocessing plant under construction in Rokkasho are shown in Table 4. Rice, milk and beef were used as single food item in the assessment. The present data for Shimokita Peninsula area where Rokkasho is included, are also given in Table 4 for comparison with the values in the safety assessment. The present results were mostly lower than the values used in the assessment. The consumption rates of shellfish and crustacea in the assessment were a little lower than the present results. Beef consumption rate in this study was 3 times higher than that in the assessment. This may reflect the difference of survey subjects and/or a change of peopleõs eating habit. Maximum consumption rates of food or food categories in the individual family are shown in Table 4. These values can be used for estimation of the maximum dose in relatively short time period. CONCLUSION The mean daily food consumption rate weighted by the proportion of families by occupation was 2,117 g d -1 p -1 in the whole Aomori Prefecture. The highest consumption was observed in farmer families and was followed by fishery families. The consumption of marine products was the highest in fishery workers families, and that of agricultural products was higher in farming workers families than fishery workers. For comparison with a national average food consumption rate, our data was re-compiled with the method used in the nation-wide nutrition surveys undertaken by Ministry of Health and Welfare, Japan. The weighted mean food consumption rate which was re-calculated by the method in the NNS was 10% higher than the national average. Food intake rates used for safety assessment of the reprocessing plant in Rokkasyo were mostly higher than the data for Shimokita Peninsula area in this work. ACKNOWLEDGMENTS We express our gratitude to Dr. S. Hisamatsu for valuable discussion and reading the manuscripts. 5

6 REFERENCES 1. Y.Ohmomo, M.Sumiya, K.Hirano, M.Nakayama, F.Sumiya and K.Kohara. Factors used for the estimation ofradioactive nuclide intake through foodstuffs by inhabitants in coastal area of Ibaraki prefecture(i). Hoken Butsuri. 9, (1974). 2. Sciences and Technology Agency, Standard Table of Food Composition in Japan - Fourth revised edition. Tokyo, Japan (1982). 3. Ministry of Health and Welfare, The National Nutrition Survey in Daiichisyuppan. Tokyo, Japan (1993). 4. Ministry of Health and Welfare, The National Nutrition Survey in Daiichisyuppan. Tokyo, Japan (1994). 5. Ministry of Health and Welfare, The National Nutrition Survey in Daiichisyuppan. Tokyo, Japan (1995). 6. Ministry of Health and Welfare, The National Nutrition Survey in Daiichisyuppan. Tokyo, Japan (1996). 6

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