Cadmium and lead contents in rice and other cereal

Cd và Pb trong gạo và ngũ cốc

Ž. The Science of the Total Environment 281 2001 165᎐175 Cadmium and lead contents in rice and other cereal products in Japan in 1998᎐2000 Shinichiro Shimbo a , Zuo-Wen Zhang a,b , Takao Watanabe c , Haruo Nakatsuka d , Naoko Matsuda-Inoguchi d , Kae Higashikawa e , Masayuki Ikeda e, U a Department of Food and Nutrition, Kyoto Women’s Uni¨ersity, Kyoto 605-8501, Japan b Institute of Occupational Medicine, Chinese Academy of Pre¨enti¨e Medicine, Beijing 100050, PR China c Miyagi Uni ¨ersity of Education, Sendai 980-0845, Japan d Miyagi Uni¨ersity, Taiwa-cho 981-3298, Japan e Kyoto Industrial Health Association, 67 Nishinokyo-Kitatsuboicho, Nakago-Ku, Kyoto 604-8472, Japan Received 10 March 2001; accepted 3 April 2001 Abstract Ž. Cereals, especially rice, are a major source of cadmium Cd intake for general Japanese populations. In Ž.Ž. Ž. Ž . 1998᎐2000, rice polished , bread loaf , noodle and wheat flour samples 4113 samples in total were collected in 63 cities all over Japan, and analyzed for Cd by inductively-coupled plasma mass spectrometry. Another pollutant Ž. Ž. element of lead Pb was determined in parallel. The grand geometric mean for Cd in polished raw uncooked rice was 50 ngrg, whereas it was 19 ngrg for flour. The value for Pb was 2᎐3ngrg in rice and flour. Calculation for daily Cd intake via rice, taking advantage of the present findings on Cd contents in rice and wheat together with administrative area-specific daily consumptions of rice and wheat showed that Cd via rice is much more than Cd via wheat and that Cd via rice is highest in an area alongside the sea of Japan among the whole country, the observation being in agreement with the results from a previous food duplicate-based field survey. ᮊ 2001 Elsevier Science B.V. All rights reserved. Keywords: Cadmium; Cereal products; Flour; Japan; Lead; Rice; Wheat U Corresponding author. Tel.: q81-75-823-0533; fax: q81-75-802-0038. 0048-9697r01r$ - see front matter ᮊ 2001 Elsevier Science B.V. All rights reserved. Ž. PII: S 0 0 4 8 - 9 6 9 7 0 1 00844-0 () S. Shimbo et al. r The Science of the Total En ¨ironment 281 2001 165᎐175166 1. Introduction Cereals, especially rice that is the staple food for general Japanese populations, were identified also as the major source of cadmium intake among the victims of Itati-itai disease endemic in the Jinzu River Basin in Japan in the mid 20th cen- Ž. tury Environment Agency, 1972 . Rice-originated Cd intake still accounts for approximately 40% of Ž. total Cd burden almost exclusively via foods of Ž people in Japan even in recent years Watanabe . et al., 2000 . Accordingly, a nation-wide survey was initiated to clarify Cd levels in rice and other cereal-based foods which citizens consume everyday and to examine if there is any difference in the Cd contents among areas within the country. Efforts were made to collect samples that were actually to be consumed by the residents of the areas. Ž. Lead Pb contents were also investigated in par- allel. The results to be presented in this paper are based on the survey of the largest scale ever published from Japan in an open literature. 2. Materials and methods 2.1. Collection of samples Samples were collected in 1998᎐2000. In prac- Ž. tice, 63 cities prefectural capitals or equivalents in total from northern-most Hokkaido Island to southern-most Okinawa Islands were selected as sampling sites. The locations are shown in Fig. 1. The locations are grouped in terms of administra- Ž tive areas for details, see lines in Fig. 1 for . borders between areas , each area consists of four᎐seven prefectures except for Hokkaido and Okinawa in which there is only one prefecture. The basic design was such that a volunteer in Ž.Ž. Fig. 1. Location of sampling sites in Japan. Each dot shows one sampling site. Lines show Area A Hokkaido , B Tohoku , C Ž.Ž.Ž .Ž.Ž .Ž .Ž . Ž . Kanto , D Tokai , E Hokuriku , F Kinki , G Chugoku , H Shikoku , I Kyushu and J Okinawa . Each area consists of four᎐seven prefectures except for Hokkaido area and Okinawa area, each of which is made of one prefecture. () S. Shimbo et al. r The Science of the Total En ¨ironment 281 2001 165᎐175 167 Table 1 Number of samples collected, as classified by area a Area Number of Number of samples sampling sites bbbcc Raw rice Boiled rice Bread Noodle Flour Total A 5 119 112 65 46 25 367 B 11 195 202 147 68 76 688 C 8 112 121 57 63 38 391 D 5 104 97 58 56 43 358 E 4 97 93 51 38 34 313 F 9 189 178 107 85 64 623 G 5 91 77 46 41 35 290 H 3 42 47 28 23 22 162 I 11 188 227 131 91 79 716 J 4 61 60 37 19 28 205 Total 65 1198 1214 727 530 444 4113 a Administrative area; for locations, see Fig. 1. b Approximate equal numbers from kitchens and stores. c From stores. charge was identified for a city to collect 10 Ž samples each of raw and boiled rice both polished, either from kitchens of residents or .Ž stores , bread loaf, either from kitchens of resi- .Ž dents or bakeries , noodle thick spaghetti in .Ž Japanese style, from stores and flour wheat flour, . from stores per site. In practice, however, this principle was followed in cases of rice and noodle, but not always so for bread and flour. Three collectors were assigned for metropolitan Tokyo. The numbers of samples collected are summa- rized in Table 1, as classified by area; approxi- mately equal numbers of raw and boiled rice and bread samples were collected from kitchens and stores. 2.2. Sample pretreatment, analytical instruments and operation conditions w Ž.x A portion e.g. 2 g fresh weight of raw rice was wet-ashed by heating in presence of mineral Ž acids as previously described Watanabe et al., .Ž. 1992 until clear residue approx. 0.3 ml was obtained. The residue was then diluted to a volume of 10 ml by addition of deionized water and the diluted wet-ash was subjected to analysis for Cd and Pb by inductively-coupled plasma mass Ž. spectrometry ICP-MS . Ž The ICP-MS apparatus connected with an . autosampler was a product of Seiko Instruments Ž. Tokyo, Japan . The system was operated under the conditions summarized in Table 2. Selection of isotopes for Cd and Pb determination and Ž. Ž. indium In and thallium Tl as internal stan- dards, preparation of calibration curves and other analytical conditions are shown in Table 3. The recovery was approximately 95 and 97% for Cd and Pb, respectively, and the accuracy when ex- amined with bovine liver, typical diet and rice Ž flour as reference materials was 96᎐118% 104% .Ž. on an average for Cd and 96᎐107% 100% for Pb. The detection limit was 0.1 ngrg for Cd and 1 Ž ngrg for Pb when a signalrnoise ratio of 2 was . taken , which was considered sufficient for Cd determination but marginally so in the case of Pb determination which is to be discussed later. In practice, the autosampler could accommo- date 50 samples in a series. The determination of Ž Cd and Pb in one series including the input of . operation conditions to the system took 2.5᎐3h so that it was possible to measure 100᎐150 sam- ples per day. 2.3. Chemicals Ž. Stock solutions Cd and Pb for certified refer- () S. Shimbo et al. r The Science of the Total En ¨ironment 281 2001 165᎐175168 Table 2 ICP-MS operation conditions Item Specification System MS analyzer Seiko SPQ 9000 plasma quadrupole MS analyzer Autosampler Seiko AT400 autosampler ICP RF power 1.5 KW Nebulizer Conventional pneumatic Plasma gas Argon Gas flow rate Coolant gas 16 lrmin Auxiliary gas 1 lrmin Carrier gas 1 lrmin Ion sampling Diameter of sampling cone orifice 0.8 mm Diameter of skimmer cone orifice 0.4 mm Ž. Sampling distance torch-interface 10 mm Mass spectrometry Scan mass range 110᎐210 mrs Total run time 20 s Integration 2 s Cone block vacuum 1.28 Eq 002 Pa Ion detector vacuum 5.69 Ey 004 Pa Sample uptake time 60 s Wash time 60 s Ž. ences 1000 ppm and mineral acids of trace element analysis grades were purchased from Ž. Wako Pure Chemicals Osaka, Japan . Standard Ž. reference materials of bovine liver NBS 1577b , Ž. Ž typical diet NBS 1548a and rice flour NBS . 1588 were obtained from the National Institute Ž of Standards and Technology Gaithersburg, .Ž USA , and that of rice flour NIES 10a, 10b and . 10c from National Institute for Environmental Ž. Sciences Tsukuba, Japan . Deionized water was prepared by filtration of city water through a Ž. Milipore-Q system Milipore, Molshim, France . 2.4. Statistical analysis Concentrations were expressed on a fresh weight basis. A preliminary analysis on the dis- tribution of the concentrations showed that Ž. arithmetic standard deviations ASD were often greater than one-third of the corresponding means Ž. Ž AM , as observed previously Watanabe et al., . 1996; Zhang et al., 1996 . Thus, a log-normal Ž distribution was considered Watanabe et al., . 1989, 1996; Zhang et al., 1996 so that geometric Ž. Ž . means GM and standard deviations GSD were taken as representative parameters of distribu- tion. In calculating GM and GSD, the value below the detection limit was assumed as if it were half the detection limit. Student’s unpaired t-test and Ž. analysis of variance ANOVA followed by multi- Ž. ple comparison Scheffe were employed to detect significant differences between or among means, with use of STAT VIEW version 5. 3. Results 3.1. Cadmium contents in rice and cereal products Ž. Cd concentrations in rice raw and boiled , Ž. bread loaf, noodle and flour wheat flour are summarized in Table 4 in terms of GM and GSD; the number of samples analyzed are given in Table 1. The grand GM concentrations are 49.7 ngrg for raw rice, 22.4 ngrg for boiled rice, 15.5 ngrg for bread, 4.31 ngrg for noodle and 19.3 ngrg for flour. Because 100 g raw rice should give Ž 212 g boiled rice when cooked Resources Coun- . cil, Science and Technology, 2000 , the ratio in GM between raw and boiled rice, 49.7r22.4 or 2.2, appeared to be reasonable. Analysis of Cd contents for possible inter-area () S. Shimbo et al. r The Science of the Total En ¨ironment 281 2001 165᎐175 169 Table 3 ICP-MS analysis conditions for cadmium and lead Item Cadmium Lead 111 208 Selected isotope Cd Pb Sensitivity High High Chamber gas None None 115 205 Ž. Internal standard 5 ␮ grlInTl Ž. Recovery rate % 94.7 96.6 Ž. Detection limit ngrg sample 0.1 1 Ž. Accuracy AM" ASD in ␮grg, ns5 Ž. Bovine liver NBS 1577b Ž. Certified value A 0.50" 0.03 0.129" 0.004 Ž. Measured value B 0.48" 0.02 0.128" 0.003 Ž. BrA % 96% 99% Ž. Typical diet NBS 1548a Ž. Certified value A 0.035" 0.0015 0.044"0.009 Ž. Measured value B 0.035" 0.004 0.047" 0.004 Ž. BrA % 100% 107% Ž. Rice flour NBS 1588 Ž. Certified value A 0.029" 0.004 0.045" 0.010 Ž. Measured value B 0.031" 0.001 0.043" 0.003 Ž. BrA % 106% 96% Ž. Rice flour NIES 10a Ž. Certified value A 0.023"0.003 ᎐ Ž. Measured value B 0.027" 0.001 ᎐ Ž. BrA % 118% ᎐ Ž. Rice flour NIES 10b Ž. Certified value A 0.32" 0.02 ᎐ Ž. Measured value B 0.31" 0.01 ᎐ Ž. BrA % 97% ᎐ Ž. Rice flour NIES 10c Ž. Certified value A 1.82" 0.06 ᎐ Ž. Measured value B 1.91" 0.11 ᎐ Ž. BrA % 105% ᎐ variation by ANOVA showed that there was a Ž. Ž significant P- 0.01 variation in all cereals and .Ž. cereal products except for flour P) 0.10 . Anal- ysis by multiple comparison disclosed that, in the case of raw rice, there were a number of pairs of areas between which the difference was signifi- Ž. cant P- 0.05 . Further perusal showed that the Cd contents in raw rice collected in area E Ž located alongside the coast of the sea of Japan; . Fig. 1 , 70.1 ngrg as GM, tended to be higher than the values for rice samples from other areas. Similar statistical comparison of Cd contents in boiled rice gave only one pair of areas in which the Cd contents were significantly different, but the value for area E was highest of all by simple comparison, being on line with the observation with Cd in raw rice. When statistical evaluation was made separately for boiled rice samples brought from kitchens and for those bought from Ž stores, inter-area difference was significant P- . 0.01 in the former samples but not in the latter Ž. P) 0.10 . Further comparison in area E showed () S. Shimbo et al. r The Science of the Total En ¨ironment 281 2001 165᎐175170 Table 4 Cadmium in rice, bread, noodle and flour ab w Ž.x Area Cadmium GM in ngrg GSD in Raw rice Boiled rice Bread Noodle Flour Ž. Ž. Ž. Ž. Ž. A 46.1 1.90 23.2 1.78 16.2 1.10 3.40 2.14 18.7 1.63 d Ž. Ž. Ž. Ž. Ž. B 46.0 2.08 21.5 1.89 15.2 1.31 4.18 1.43 18.5 1.31 Ž. Ž. Ž. Ž. Ž. C 53.8 1.99 23.1 1.77 16.2 1.17 4.06 1.46 20.9 1.48 d Ž. Ž. Ž. Ž. Ž. D 45.1 2.11 20.5 2.16 15.0 1.20 4.60 1.63 19.4 1.51 dd Ž. Ž. Ž. Ž. Ž. E 70.1 1.81 30.3 1.69 14.9 1.09 4.02 1.50 19.8 1.33 Ž. Ž. Ž. Ž. Ž. F 55.3 1.95 25.3 1.89 14.7 1.34 4.42 1.40 18.7 1.43 d Ž. Ž. Ž. Ž. Ž. G 44.8 1.99 21.9 1.82 16.1 1.12 4.14 1.47 17.0 1.31 Ž. Ž. Ž. Ž. Ž. H 56.3 1.76 21.4 2.65 16.6 1.10 5.02 1.42 18.0 1.35 dd Ž. Ž. Ž. Ž. Ž. I 44.2 2.06 19.3 2.39 15.8 1.16 4.29 1.59 21.2 2.18 d Ž. Ž. Ž. Ž. Ž. J 43.0 2.01 20.7 1.86 15.6 1.13 5.29 1.71 19.5 1.52 Ž. Ž. Ž. Ž. Ž. Total 49.7 2.01 22.4 2.03 15.5 1.22 4.31 1.58 19.3 1.58 UU UU UU UU c ANOVA NS a Administrative area; for locations, see Fig. 1. b All measures were above the detection limit of 0.1 ngrg fresh weight of samples. c UU and U for P - 0.01 and 0.05, respectively. NS for P) 0.10. d w Ž.x GMs with the same superscript letters are significantly P- 0.05 by multiple comparison Scheffe different from each other when compared between areas. that the value tended to be greater for kitchen- w Ž. Ž . brought boiled rice 31.9 ngrg 1.76 as GM GSD x for 52 samples than for store-bought boiled rice w Ž. x 28.3 ngrg 1.58 for 41 samples , although the Ž. difference was statistically insignificant P) 0.10 . Ž. In contrast, no significant difference P) 0.10 was detected when the multiple comparison test was applied to wheat products, such as bread, noodle or flour. Although ANOVA showed sig- nificant difference in GMs as discussed above, the ratio of the largest GM over the smallest was 1.13, 1.56 and 1.25 for bread, noodle and flour, respectively., whereas the ratio was 1.63 for raw rice. 3.2. Lead contents in rice and cereal products Pb contents in rice and other cereal products are summarized in Table 5. Grand GM values for the products studied are in a range from 1.5 ngrg for boiled rice to 3.2 ngrg for bread. ANOVA Ž disclosed significant differences P- 0.01 for all . cases except for noodle for which P - 0.05 among the 10 areas. The multiple comparison, however, identified only one or two pairs of areas for which the inter-area difference was statistically signifi- Ž. cant P- 0.05 . It should be noted that the mea- sures were below the detection limit in substan- Ž. tial numbers of cases Table 5 . For example, raw rice samples with measures below the limit counted as many as 946 among the total of 1198, or 79%. The ratio was similarly high for boiled Ž. Ž. rice 78% and flour 67% , although lower for Ž. Ž. bread 29% and noodle 19% . 3.3. Inter-site difference in Cd in raw rice Cereal samples, especially raw rice samples, Ž were collected in two or more sites or by two or . more collectors in several prefectures. Compar- isons were made to examine if Cd contents in raw Ž. rice varied between or among the sites even in case the sites are located rather close to each other, i.e. in the same prefecture. In practice, two sets of samples were available in seven prefec- tures, three sets in three prefectures and five sets Ž in one prefecture Hokkaido Island which is the . largest prefecture in space . Difference was ex- amined by Student’s t-test when only two sample sets were available in one prefecture and by ANOVA in case more than two sets were ex- amined. The statistical evaluation showed no sig- Ž. nificant difference P) 0.10 in eight prefectures Ž. including Hokkaido Island out of the 11, sug- gesting that within-prefecture difference was not substantial in most cases. () S. Shimbo et al. r The Science of the Total En ¨ironment 281 2001 165᎐175 171 Table 5 Lead in rice, bread, noodle and flour ab w Ž. x Area Lead GM in ngrg GSD : - DL Raw rice Boiled rice Bread Noodle Flour dd Ž. Ž. Ž. Ž. Ž. A 1.8 1.32 ;110 1.3 1.83 ; 98 4.9 2.26 ;7 2.8 2.28 ; 7 2.4 1.97 ; 19 d Ž. Ž. Ž. Ž. Ž. B 2.3 1.87 ;147 1.7 2.25 ;143 3.2 2.48 ; 44 3.2 2.58 ; 14 3.4 2.00 ;31 Ž. Ž. Ž. Ž. Ž. C 2.4 2.02 ; 82 1.6 2.11 ; 86 3.8 2.63 ; 12 2.4 3.02 ; 23 3.6 2.54 ; 17 d Ž. Ž. Ž. Ž. Ž. D 1.9 1.64 ; 89 1.5 1.98 ; 75 2.1 2.03 ;28 2.9 2.20 ; 10 2.5 1.83 ; 28 Ž. Ž. Ž. Ž. Ž. E 2.0 1.89 ; 82 1.6 2.12 ; 67 3.1 1.82 ; 9 3.9 2.25 ; 1 1.9 1.50 ; 29 Ž. Ž. Ž. Ž. Ž. F 2.3 1.90 ;144 1.5 1.95 ;141 2.8 2.47 ; 39 3.0 2.02 ; 10 3.0 2.34 ; 38 Ž. Ž. Ž. Ž. Ž. G 2.3 2.04 ; 69 1.2 1.60 ; 70 3.7 2.06 ; 7 3.2 2.02 ; 6 2.1 1.70 ; 28 d Ž. Ž. Ž. Ž. Ž. H 3.0 2.51 ; 27 1.3 1.65 ; 40 3.4 1.68 ; 3 3.7 2.09 ; 1 2.5 1.85 ; 14 Ž. Ž. Ž. Ž. Ž. I 2.5 2.25 ;144 1.6 1.95 ;166 3.5 2.94 ; 43 2.8 2.23 ; 18 2.7 2.11 ; 49 d Ž. Ž. Ž. Ž. Ž. J 2.0 1.88 ; 52 1.2 1.45 ; 56 1.8 2.15 ;22 1.7 2.38 ; 10 1.8 1.49 ;26 Ž. Ž. Ž. Ž. Ž. Total 2.2 1.93 ;946 1.5 1.96 ;941 3.2 2.47 ;214 2.9 2.34 ;100 2.7 2.06 ;279 ANOVA c UU UU UU U UU a Administrative area; for locations, see Fig. 1. b Ž. The number of measures below the detection limit -DL of 1 ngrg fresh weight of samples. c UU and U for P - 0.01 and 0.05, respectively. d w Ž.x GMs with the same superscript letters are significantly P- 0.05 by multiple comparison Scheffe different from each other when compared between areas. In a further step, Cd contents in raw rice were classified by prefecture and GM values for indi- vidual prefectures were compared among each area. Because area A and J consist of one prefec- ture each, the comparison was made for eight areas of B᎐I. The results showed that the within- Ž area difference was significant P - 0.01 by . ANOVA in six areas out of the eight, whereas it ( . was insignificant P ) 0.10 for two areas of C and H; area C embraces several large cities including Tokyo and area H has only limited rice produc- tion because the land is mountainous, so that rice is imported from other areas in Japan to these two areas. Combining this observation with the findings on the within-prefecture difference, it is apparent that detection of geographical differ- ence in Cd contents in raw rice relates to the Ž dimensions of the regions e.g. city, prefecture or . area considered for comparison. 4. Discussion The present study showed that the grand GM for Cd in rice consumed in Japan was approxi- mately 50-ngrg raw rice with significant variation Ž depending on the areas rice from area E probably . being higher than others whereas Cd contents were lower in three wheat-based food materials Ž. Ž. of bread loaf 16 ngrg , noodle 4 ngrg and flour Ž.Ž. 19.3 ngrg Table 4 with less remarkable inter- Ž area variation as shown by the absence of pairs . of areas with significant difference . The observed GM of 50 ngrg for raw rice is in general agree- ment with the results of a nation-wide mass sur- Ž. vey with ) 35 000 samples of 0.06 ␮grg Ž Ministry of Agriculture, Forestry and Fishery, . 2000 when the difference between the geometric Ž. the present study and arithmetic means is taken into account. Ž. Pb levels in cereals including rice and wheat Ž. were much lower 2᎐3ngrg and levels in many Ž. samples were below the detection limit Table 5 . Thus, the observed GM values for Pb should be taken as semi-quantitative and not strictly quanti- tative. This limitation may explain why the ratio Ž. in GM of raw rice over boiled rice 2.2r1.5s1.5 does not agree with the expected value of 2.1 Ž. Resources Council, 2000 . When compared with the levels in late 1980s () S. Shimbo et al. r The Science of the Total En ¨ironment 281 2001 165᎐175172 Ž. 53 ng Cdrg rice, Watanabe et al., 1989 and Ž. mid-1990s 53 ng Cdrg rice , the present observa- tion of 50 ng Cdrg rice suggests that there have been essentially no changes or only slight reduc- tion in Cd contents in rice in Japan during the Ž past 10 years. In contrast, Pb contents in rice 2᎐ 3 . ngrg appear to show a gradual decrease from the levels of approximately 5 ngrg both in late Ž. 1980s Watanabe et al., 1989 and in mid-1990s Ž. Zhang et al., 1996 . Cd and Pb contents in rice available in various parts of the world were previously reviewed, and it was summarized that Cd contents in rice avail- able in Japan is substantially higher than the levels in rice from surrounding Asian countries Ž. Ž e.g. 15᎐30 ngrg or outside Asia e.g. 20᎐30 ngrg for rice available in Europe; Watanabe et . al., 1989, 1996 , whereas the reverse is actually the case for Pb contents in rice from Japan when compared with rice from other parts of Asia Ž. Watanabe et al., 1989, 1996; Zhang et al., 1996 . With regard to Cd in flour, both high values of 43 Ž.Ž ngrg Wolnik et al., 1983 or 8᎐77 ngrg Muller . et al., 1996 for flour in Europe and low values of Ž. 12᎐17 ngrg Watanabe et al., 1998 or 15 ngrg Ž. Zhang et al., 1998 for flour in China were re- ported. The present observation of 19 ng Cdrg flour is not only closer to the latter levels, but further in agreement with the values for whole Ž wheat grain of 40᎐50 ngrg Cd Bruggemann and Kumpulainen, 1995; Chaudri et al., 1995; Mench . et al., 1997; Conti et al., 2000 or 20᎐100 ngrg Ž. Lorenz et al., 1986 , because Cd in wheat grain is higher in bran and lower in albumen so that Cd Ž in flour after milling is much lower e.g. approx. .Ž 40% than that in the whole grain Zhang et al., . 1997 . The inter-area difference in Cd contents in rice samples was substantial among raw samples, less so among kitchen-bought boiled rice and insig- nificant among store-bought boiled samples. This observation may deserve discussion because the findings are probably related to the marketing system of rice in Japan. In everyday life, each Ž family typically non-farming urban family in the . case of the present study will purchase rice from Ž. local stores to cook mostly by boiling in the kitchens; in the stores, both locally harvested rice as well as nation-widely marketed rice are avail- able. In contrast, store-bought boiled rice is sup- plied by food processing industries, which will predominantly utilize widely marketed rice rather than local rice because they cook rice by a great batch. Thus, kitchen-bought boiled rice samples will probably reflect local conditions better than the store-bought counterparts. A similar consideration can be applied to ex- plain rather homogeneous Cd and Pb contents in Ž. wheat-based food materials Tables 4 and 5 . Whereas, the rate of self-sufficiency is nearly Ž 100% in the case of rice production and there- . fore, supply , the rate for wheat is as low as 8% as Ž the 3-year average for 1995᎐1997 Ministry of . Agriculture, Forestry and Fishery, 1999 . The lat- ter low rate indicates that the materials for wheat-based products such as bread and noodle Ž. including flour are imported from abroad as- sumedly in large batches, and therefore, the metal level in the products will not be related to local conditions where they are consumed. When the present observation on raw rice is compared with the values reported in literature Ž. Table 6 following the flow of time, it appears likely that there has been no substantial changes in Cd contents in rice in the past 12 years, whereas Pb contents may have been decreasing gradually. The methods of analysis employed were, however, not the same, i.e. flameless atomic absorption was Table 6 Cadmium and lead contents in raw polished rice, reported in literature a Ž. Reference Element concentration ngrg Cadmium Lead Saito et al., 1988 60 14 Watanabe et al., 1989 53 5 Rivai et al., 1990 21᎐99 Watanabe et al., 1992 41 Watanabe et al., 1993 46 Watanabe et al., 1996 56 Zhang et al., 1996 5 Present study 50 2 a Geometric means. () S. Shimbo et al. r The Science of the Total En ¨ironment 281 2001 165᎐175 173 Ž used in early day studies Saito et al., 1988; Watanabe et al., 1989, 1992, 1993; Rivai et al., . 1990 , whereas it was ICP-MS in recent studies Ž. Watanabe et al., 1996; Zhang et al., 1996 as in the present study. Possible health implication of dietary Cd intake among general Japanese populations has been Ž. discussed in a separate paper Ikeda et al., 2000a . In this connection, it may be worthy to note that dietary Cd intake is almost the exclusive source of Ž. Cd intake Ikeda et al., 2000b and that rice accounts for approximately 40% of total dietary Ž. Cd intake Watanabe et al., 2000 . In a very sharp contrast, dietary Pb intake of Japanese popula- Ž tions is among the lowest of the world Zhang et . al., 2000 rice accounting for less than 20% of the total dietary intake, although Pb intake via respi- ration of general air is comparable to that via Ž. food Ikeda et al., 2000b . Taking advantage of the published data on daily consumption of various food items including Ž rice and wheat products Ministry of Health and . Welfare, 2000 , it is possible to estimate the daily intake of Cd and Pb via two staple cereals of rice and wheat. The estimation was made by multipli- cation of daily consumption with Cd and Pb con- tents in the cereals. Both data on the rice and Ž wheat consumption Ministry of Health and Wel- . fare, 2000 and that on Cd and Pb contents in rice Ž. and wheat Table 4 are available not only for the whole country of Japan but for individual admin- Ž istrative areas for geographical locations, see Fig. . 1 , the estimation was made for the whole country Ž. shown in the average column in Table 7 as well Ž as for individual areas the minimum and the maximum values among the 10 areas are shown . as a range in Table 7 . On the whole country basis, Japanese people Ž. take 1.8 times more rice 165 grday than wheat Ž 91 grday as raw material, taken as bread, noodle . etc. on a weight basis, and this difference is further expanded to 4.7 times when Cd intake is Ž compared 8.2 ␮ grday from rice vs. 1.8 ␮grday . from wheat because Cd contents are much higher Ž. Ž. in rice 50 ngrg than in wheat 19 ngrg . When the daily Cd intake by Japanese women is con- sidered to be approximately 25.5 ␮ grday Ž. Watanabe et al., 2000 ; the value for men should be somewhat higher than this level because men . take more food than women , daily intake of 8.2 and 1.8 ␮gCdrday via rice and wheat, respec- tively, accounts for 32 and 7% of the total dietary Cd intake. Pb contents are more or less similar in rice and in wheat, and contribution of the two cereals as sources of dietary Pb intake is essen- Ž. tially in proportion of the cereal intake Table 7 . It is further possible to make calculation for each administrative area. The calculation on the Ž. area basis Table 8 shows that the Cd intake via rice is the highest in area E in agreement with the Ž previous observation in a field survey Watanabe . et al., 2000 ; this high value is due to the facts that both rice intake and Cd content in rice are high in this area. Cd intake via wheat is smaller Table 7 Intake of cadmium and lead via rice and wheat Item Rice Wheat Ž. Ž. Average Range Average Range Ž. Element content ngrg a Ž. Ž . Ž . Daily cereal consumption grday 165 158᎐178 91 67᎐104 Cadmium Ž. Ž . Ž . Cd content ngrg 49.7 43.0᎐70.1 19.3 17.0᎐21.2 Ž. Ž . Ž . Daily Cd intake ngrday 8191 7409᎐12506 1754 1297᎐ 1993 Lead Ž. Ž . Ž . Pb content ngrg 2.2 1.8᎐3.0 2.7 1.8᎐3.6 Ž. Ž. Ž. Daily Pb intake ngrday 363 304᎐478 245 120᎐201 a Ž. Cited from Ministry of Health and Welfare 2000 . () S. Shimbo et al. r The Science of the Total En ¨ironment 281 2001 165᎐175174 Table 8 Cadmium intake via rice and wheat in various areas a Area Rice Wheat b b Cadmium Cadmium Intake Intake b b Ž. Ž. grday grday Content Intake Content Intake Ž. Ž . Ž. Ž . ngrgngrday ngrgngrday A 168.7 46.1 7777 83.8 18.7 1567 B 175.0 46.0 8050 74.0 18.5 1369 c c C 158.2 53.8 8511 95.4 20.9 1993 D 167.0 45.1 7532 90.4 19.4 1754 E 178.4 70.1 12 506 76.6 19.8 1517 d d F 172.6 55.3 9542 104.4 18.7 1877 G 167.4 44.8 7500 95.7 17.0 1627 H 159.2 56.3 8963 94.6 18.0 1703 I 169.7 44.2 7501 84.4 21.2 1789 e e J 172.3 43.0 7409 66.5 19.5 1297 Total 164.8 49.7 8191 90.9 19.3 1754 a For locations, see Fig. 1. b Ž. Intakes of rice and wheat are cited from Ministry of Health and Welfare 2000 , and Cd contents in rice and wheat are cited from the raw rice and flour columns in Table 4. c Ž. The average value for Kanto I and Kanto II areas Ministry of Health and Welfare, 2000 . d Ž. The average value for Kinki I and Kinki II areas Ministry of Health and Welfare, 2000 . e Ž. The value for southern Kyoshu Ministry of Health and Welfare, 2000 . Ž. than that via rice Table 7 , but relatively higher Ž in the two most urbanized areas of C in which . Tokyo, Yokohama and Kawasaki are and F Ž. where Osaka, Kobe and Kyoto are , presumably Ž with more consumption of bread and noodle Ta- . ble 8 . No area-specific data of comparison on Pb via rice and that via wheat are presented, because cereal-based Pb intake is limited with small Ž. inter-area variations Table 7 . The present analysis made it clear that varia- tion in Cd contents in raw rice is significant among prefectures even when they belong to the same administrative area. Thus, it is apparently desirable to make estimation of cereal-based Cd intake for each prefecture. The data on cereal consumption on the prefecture basis are, how- ever, not available unfortunately. Acknowledgements A part of this work was supported by research grants-in-aid from the Environment Agency, the Government of Japan to S.S. for 1998 to 2000. References Bruggemann J, Kumpulainen J. The status of trace elements in former Federal republic of Germany. Z Lebensm Unters Forsch 1995;201:1᎐6. Chaudri AM, Zhao FJ, McGrath SP, Crosland AR. The cadmium content of British wheat grain. J Environ Qual 1995;24:850᎐855. Conti ME, Cubadda F, Carcea M. Trace elements in soft and durum wheat in Italy. Food Addit Contam 2000;17:45᎐53. Environment Agency, the Government of Japan. Control of cadmium-induced environmental pollution. Tokyo: Envi- ronment Agency, 1972:166᎐168, in Japanese. Ikeda M, Zhang Z-W, Moon C-S, Shimbo S, Watanabe T, Nakatsuka H, Matsuda-Inoguchi N, Higashikawa K. Possi- ble effects of environmental cadmium exposure on kidney function in the Japanese general population. Int Arch Occup Environ Health 2000a;73:15᎐25. Ikeda M, Zhang Z-W, Shimbo S, Watanabe T, Nakatsuka H, Moon C-S, Matsuda-Inoguchi N, Higashikawa K. Exposure of women in general populations to lead via food and air in east and southeast Asia. Am J Ind Med 2000b;38:271᎐280. Lorenz H, Ocker HD, Bruggemann J, Weigert P, Sonneborn M. Cadmiumgehalte in Getreideproben der Vergangenheit ᎏ Vergleich zur Gegenwart. Lebensm Unters Forsch 1986;183:402᎐405, in German with English abstract. Mench M, Braize D, Mocquuot B. Cadmium availability to wheat in five soil series from the Yonne district, Burgundy, France. Environ Pollut 1997;95:93᎐103. [...]... Nakatsuka H, Ikeda M Cadmium and lead contents in rice available in various areas of Asia Sci Total Environ 1989;80:175᎐184 Watanabe T, Nakatsuka H, Satoh H, Yamamoto R, Ikeda M Reduced dietary cadmium intake in past 12 years in a rural area in Japan Sci Total Environ 1992;119:43᎐50 Watanabe T, Iwami O, Shimbo S, Ikeda M Reduction in lead and cadmium intake among general populations in Japan Int Arch Occup... Finance Printing Bureau, 2000 p 40, in Japanese with English translation Rivai F, Koyama H, Suzuki S Cadmium content in rice and its daily intake in various countries Bull Environ Contam Toxicol 1990;44:910᎐916 Saito I, Ohshima H, Kawamura N, Yamada M Screening method for determination of high levels of cadmium, lead and copper in foods by polarized Zeeman atomic absorption spectrometry using discrete... ironment 281 (2001) 165᎐175 Ministry of Agriculture, Forestry and Fishery, the Government of Japan 1997 Food balance tables Tokyo: Agriculture and Forestry Statistics Association, 1999;92᎐95, in Japanese Ministry of Agriculture, Forestry and Fishery, the Government of Japan A press release on pesticides and other contaminants in rice, 1999 2000, in Japanese Ministry of Health and Welfare, the Government... N, Higashikawa K, Ikeda M Cadmium exposure of women in general populations in Japan during 1991᎐1997 compared with 1977᎐1991 Int Arch Occup Environ Health 2000;73:26᎐34 Wolnik KA, Fricke FL, Capar SG, Braude GL, Meyer MW, Satzger RD, Bonnin E Elements in major raw agricultural crops in the United States 1 Cadmium and lead in lettuce, peanuts, potatoes, soy beans, sweet corn and wheat J Agri Food Chem... Lead content of rice collected from various areas in the world Sci Total Environ 1996;191:169᎐175 Zhang Z-W, Qu J-B, Xu G-F, Song L-H, Wang J-J, Shimbo S, Watanabe T, Nakatsuka H, Higashikawa K, Ikeda M Maize and foxtail millet as substantial sources of dietary lead intake Sci Total Environ 1997;208:81᎐88 Zhang Z-W, Watanabe T, Shimbo S, Higashikawa K, Ikeda M Lead and cadmium contents in cereals and. .. M Lead and cadmium contents in cereals and pulses in north-eastern China Sci Total Environ 1998;220:137᎐145 Zhang Z-W, Moon C-S, Shimbo S, Watanabe T, Nakatsuka H, Matsuda-Inoguchi N, Higashikawa K, Ikeda M Further reduction in lead exposure in women in general populations in Japan in the 1990s, and comparison with levels in east and south-east Asia Int Arch Occup Environ Health 2000;73:91᎐97 ... in Japan 1998 Tokyo: Dai-ichi Shuppan Press, 2000:73᎐75, in Japanese Muller M, Anke M, Hartmann E, Illing-Gunther H Oral cadmium exposure of adults in Germany 1 Cadmium content of food staffs and beverages Food Addit Contam 1996;13:359᎐378 Resources Council, Science and Technology Agency, the Government of Japan Standard tables of food composition in Japan, 5th revised version Tokyo: Ministry of Finance... M Cadmium contents in rice samples from various areas in the world Sci Total Environ 1996;184:191᎐196 Watanabe T, Zhang Z-W, Qu J-B, Xu G-F, Song L-H, Wang JJ, Shimbo S, Nakatsuka H, Higashikawa K, Ikeda M Urban-rural comparison on cadmium exposure among general populations in Shandong Province, China Sci Total Environ 1998;217:1᎐8 Watanabe T, Zhang Z-W, Moon C-S, Shimbo S, Nakatsuka H, Matsuda-Inoguchi . 1.63 for raw rice. 3.2. Lead contents in rice and cereal products Pb contents in rice and other cereal products are summarized in Table 5. Grand GM values. in rice and flour. Calculation for daily Cd intake via rice, taking advantage of the present findings on Cd contents in rice and wheat together with administrative