Cadmium and lead contents in rice and other cereal

Cd và Pb trong gạo và ngũ cốc

Cadmium and lead contents in rice and other cereal

Shinichiro Shimboa, Zuo-Wen Zhanga,b, Takao Watanabec,

Haruo Nakatsukad, Naoko Matsuda-Inoguchid, Kae Higashikawae,

Masayuki Ikedae,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

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

element of lead Pb was determined in parallel The grand geometric mean for Cd in polished raw uncooked rice was 50 ng rg, whereas it was 19 ngrg for flour The value for Pb was 2᎐3 ngrg 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 䊚 2001 Elsevier Science B.V All rights reserved.

Keywords: Cadmium; Cereal products; Flour; Japan; Lead; Rice; Wheat

UCorresponding author Tel.:q81-75-823-0533; fax: q81-75-802-0038.

0048-9697 r01r$ - see front matter 䊚 2001 Elsevier Science B.V All rights reserved.

PII: S 0 0 4 8 - 9 6 9 7 0 1 0 0 8 4 4 - 0

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

tury Environment Agency, 1972 Rice-originated

Cd intake still accounts for approximately 40% of

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

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

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

Fig 1 Location of sampling sites in Japan Each dot shows one sampling site Lines show Area A Hokkaido , B Tohoku , C

Ž Kanto , D Tokai , E Hokuriku , F Kinki , G Chugoku , H Shikoku , I Kyushu and J Okinawa Each area consists of Ž Ž Ž Ž Ž Ž Ž four ᎐seven prefectures except for Hokkaido area and Okinawa area, each of which is made of one prefecture.

Table 1

Number of samples collected, as classified by area

a

Area Number of Number of samples

sampling sites Raw rice b Boiled rice b Bread b Noodle c Flour c Total

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

polished, either from kitchens of residents or

stores , bread loaf, either from kitchens of

dents or bakeries , noodle thick spaghetti in

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

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.,

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

spectrometry ICP-MS

Ž

autosampler was a product of Seiko Instruments

ŽTokyo, Japan The system was operated under the conditions summarized in Table 2 Selection

of isotopes for Cd and Pb determination and

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%

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᎐3 h

so that it was possible to measure 100᎐150 sam-ples per day

2.3 Chemicals

Stock solutions Cd and Pb for certified

refer-Table 2

ICP-MS operation conditions

quadrupole MS analyzer

Ion sampling Diameter of sampling cone orifice 0.8 mm

Diameter of skimmer cone orifice 0.4 mm

Sampling distance torch-interface 10 mm

element analysis grades were purchased from

Wako Pure Chemicals Osaka, Japan Standard

reference materials of bovine liver NBS 1577b ,

1588 were obtained from the National Institute

Ž

USA , and that of rice flour NIES 10a, 10b and

10c from National Institute for Environmental

Sciences Tsukuba, Japan Deionized water was

prepared by filtration of city water through a

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

arithmetic standard deviations ASD were often

greater than one-third of the corresponding means

ŽAM , as observed previously Watanabe et al., Ž

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

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

analysis of variance ANOVA followed by

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

Cd concentrations in rice raw and boiled ,

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

Table 3

ICP-MS analysis conditions for cadmium and lead

Ž

Accuracy AM"ASD in ␮grg, ns5

Bovine liver NBS 1577b

Ž

Ž

Ž

Typical diet NBS 1548a

Ž

Ž

Ž

Rice flour NBS 1588

Ž

Ž

Ž

Rice flour NIES 10a

Ž

Ž

Ž

Rice flour NIES 10b

Ž

Ž

Ž

Rice flour NIES 10c

Ž

Ž

Ž

variation by ANOVA showed that there was a

significant P-0.01 variation in all cereals and

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

cant P-0.05 Further perusal showed that the

Cd contents in raw rice collected in area E

Žlocated 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

ŽP)0.10 Further comparison in area E showed

Table 4

Cadmium in rice, bread, noodle and flour

Area Cadmium GM in ng rg GSD in

d

d

d

d

c

a

Administrative area; for locations, see Fig 1.

b

All measures were above the detection limit of 0.1 ng rg fresh weight of samples.

cUUandU for P

-0.01 and 0.05, respectively NS for P)0.10.

dGMs with the same superscript letters are significantly Pw -0.05 by multiple comparison Scheffe different from each other Ž x when compared between areas.

that the value tended to be greater for

brought boiled rice 31.9 ngrg 1.76 as GM GSD

x

for 52 samples than for store-bought boiled rice

w28.3 ngrg 1.58 for 41 samples , although theŽ x

difference was statistically insignificant P)0.10

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

cant P-0.05 It should be noted that the

mea-sures were below the detection limit in

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

rice 78% and flour 67% , although lower for

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

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

nificant difference P)0.10 in eight prefectures

Žincluding Hokkaido Island out of the 11, sug- gesting that within-prefecture difference was not substantial in most cases

Table 5

Lead in rice, bread, noodle and flour

Area Lead GM in ng rg GSD : -DL

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

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

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

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

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

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

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

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

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

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

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

a

Administrative area; for locations, see Fig 1.

b

The number of measures below the detection limit -DL of 1 ngrg fresh weight of samples.

cUUandU for P

-0.01 and 0.05, respectively.

dGMs with the same superscript letters are significantly Pw -0.05 by multiple comparison Scheffe different from each other Ž x 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

of bread loaf 16 ngrg , noodle 4 ngrg and flour

Ž19.3 ngrg Table 4 with less remarkable inter- Ž

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

ŽMinistry of Agriculture, Forestry and Fishery,

2000 when the difference between the geometric

Žthe present study and arithmetic means is taken into account

Pb levels in cereals including rice and wheat

were much lower 2᎐3 ngrg and levels in many

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

in GM of raw rice over boiled rice 2.2r1.5s1.5 does not agree with the expected value of 2.1

ŽResources Council, 2000 When compared with the levels in late 1980s

Ž53 ng Cdrg rice, Watanabe et al., 1989 and.

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

1980s Watanabe et al., 1989 and in mid-1990s

ŽZhang 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

Že.g 15᎐30 ngrg or outside Asia e.g 20᎐30 Ž

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

ŽWatanabe et al., 1989, 1996; Zhang et al., 1996

With regard to Cd in flour, both high values of 43

ngrg Wolnik et al., 1983 or 8᎐77 ngrg Muller

et al., 1996 for flour in Europe and low values of

12᎐17 ngrg Watanabe et al., 1998 or 15 ngrg

ŽZhang 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

ŽLorenz 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

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

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

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 malat-terials for wheat-based products such as bread and noodle

Žincluding 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

ŽTable 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

Reference Element concentration ng rg

Rivai et al., 1990 21 ᎐99 Watanabe et al., 1992 41 Watanabe et al., 1993 46 Watanabe et al., 1996 56

a Geometric means.

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

ŽWatanabe 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

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

Cd intake Ikeda et al., 2000b and that rice

accounts for approximately 40% of total dietary

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

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

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

Žshown 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

take 1.8 times more rice 165 grday than wheat Ž91 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

in rice 50 ngrg than in wheat 19 ngrg When the daily Cd intake by Japanese women is

ŽWatanabe 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 ␮g Cdrday 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

tially in proportion of the cereal intake Table 7

It is further possible to make calculation for each administrative area The calculation on the

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

Ž

Element content ng rg

a

Cadmium

Lead

a Cited from Ministry of Health and Welfare 2000

Table 8

Cadmium intake via rice and wheat in various areas

a

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

The average value for Kanto I and Kanto II areas Ministry of Health and Welfare, 2000

d

The average value for Kinki I and Kinki II areas Ministry of Health and Welfare, 2000

e

The value for southern Kyoshu Ministry of Health and Welfare, 2000

than that via rice Table 7 , but relatively higher

Ž

in the two most urbanized areas of C in which

Žwhere 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

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.