Biol Trace Elem Res (2011) 139:269 286
DOI 10.1007/s12011-010-8661-x
Estimation of Dietary Pb and Cd Intake from Pb and Cd
in Blood or Urine
Masayuki Ikeda & Shinichiro Shimbo &
Takao Watanabe & Fumiko Ohashi & Yoshinari Fukui &
Sonoko Sakuragi & Jiro Moriguchi
Received: 6 January 2010 / Accepted: 24 February 2010 /
Published online: 27 April 2010
#
Springer Science+Business Media, LLC 2010
Abstract Successful trials were made to estimate the dietary daily intake of lead (Pb) and
cadmium (Cd) via foods from the levels of the metals in blood or urine. In practice, 14 and
15 reports were available for Pb and Cd in blood (Pb-B and Cd-B), urine (Pb-U and Cd-U)
and 24-h diet duplicates (Pb-D and Cd-D), respectively, from which 68 pairs each of Pb or
Cd in blood and food duplicates [each being geometric mean (GM) values for the survey
sites] were obtained. Regression analysis revealed that there was a significant correlation
between Pb-B and Pb-D, and also between Cd-B and Cd-D, suggesting that it should be
possible to estimate both Pb-D and Cd-D from Pb-B and Cd-B, respectively. For Cd-U, the
number of available cases was limited (20 pairs), but a significant correlation was detected
between Cd-U (as Cd-Ucr, or Cd levels in urine as corrected for creatinine concentration)
and Cd-D. Care should be taken in estimating Pb-D from Pb-B, as the ratio of Pb-D over
Pb-B may decrease as a function of increasing Pb-B levels. The Pb-D (źg/day) for typical
Japanese women with Pb-B of 15 źg/l was best estimated to be 13.5 źg/day. No Cd-B- or
Cd-Ucr-dependent change was detected in case of Cd. The best estimate of Cd-D for Cd-B
at 1.5 źg/l should be about 19.4 źg/day.
. . . .
Keywords Blood Cadmium Daily diet Lead Urine
: :
M. Ikeda ( ) F. Ohashi Y. Fukui
Kyoto Industrial Health Association (Main Office), 67 Nishinokyo-Kitatsuboicho, Nakagyo-ku,
Kyoto 604-8472, Japan
e-mail: ikeda@kojohokenkai.or.jp
S. Shimbo
Kyoto Women s University, Kyoto 605-8501, Japan
T. Watanabe
Miyagi University of Education, Sendai 980-0845, Japan
:
S. Sakuragi J. Moriguchi
Kyoto Industrial Health Association (Mibu Office), Kyoto 604-8871, Japan
270 Ikeda et al.
Introduction
Dietary intake of ubiquitous heavy metals such as cadmium (Cd) and lead (Pb) are
among the foci of public concern especially as the metal levels in atmosphere has been
gradually decreasing in many countries including Japan, so that body burden via
respiratory route will be less important whereas metal intake via foods remains as the
major source [1 3]. Although it is desirable to have data on dietary metal intake, such
procedures as 24-h food duplicate collection followed by instrumental analyses for metals
to obtain reliable estimate for dietary intake are not only complex but time- and hand-
consuming [4 6].
In the present analysis, data were collected from previous publications on Cd and Pb in
blood, urine and diet (Cd-B, Pb-B, Cd-U, Pb-U, Cd-D and Pb-D, respectively) of populations
mostly in Japan and in east or south-east Asia, and correlations among the parameters were
examined for a possibility that Pb-D and Cd-D may be estimated from Pb-B and Cd-B,
respectively, or Cd-D from Cd-U.
Materials and Methods
Data from Literature
Data are all on general populations without occupational exposure to Pb or Cd, and cited
from previous publications, i.e. references [7 19, 22, 45] for Pb in blood, urine or 24-h
food duplicate samples, and references [7 16, 18, 20 23, 45] for Cd in blood, urine or 24-h
food duplicate samples (Tables 1 and 2). Regarding Cd-U, the values as corrected for
creatinine (Cd-Ucr) [24] rather than non-corrected values (CdUob) were employed simply
because the published data were more abundant for Cd-Ucr than Cd-Uob despite the
criticism that creatinine correction may induce biases especially among aged people [25].
Watanabe et al. [12] published GM values for Cd-B, Cd-D, Pb-B and Pb-D in 38 sites, i.
e. 19 sites being studied twice, 10 years apart. From the 38 data sets, those with g"10 pairs
of data on blood and food duplicates were selected so that 32 sets were taken for present
analysis.
Using the market basket method [4], Matsuda [18] reported on dietary Cd and Pb
intake for adult Japanese (assumedly at the ages of 40 59 years, men and women not
specified). In the report, Cd and Pb intakes were given by food groups, e.g. cereals,
animal meats, fish and shellfish etc. similar to the classification by Ministry of Health,
Labour and Welfare, Japan [26]. The report [26] describes per capita per day food
consumption (in weight) among Japanese populations by age groups (1 6, 7 14, 15 19
and 20 29 years, and by decade up to 69, and g"70 years of age) and for men and women
combined and also separately. It is known that adult men take more cereals (typically rice,
the leading source of dietary Cd in Japan [13]) than adult women [26]. Thus, Cd intake
for adult women for example was estimated for each food group assuming that the Cd
intake for women was proportional to the amount (in weight) of food consumed [i.e. Cd
in the food group × (food amount for women/food amount for men and women
combined)], which was followed by summation for all food groups to estimate daily
intake via foods. The same assumption of Cd (or Pb) intake proportional to the amount of
foods in the food groups was taken in cases of estimation for dietary Cd or Pb intake of
children except that boys and girls were treated as combined.
Table 1 The database for Pb internal dose and dietary intake
Reference Country/Area Location Gender, Year of Pb-B Pb-Ucr Pb-D Pb-B over Pb-Ucr over
etc. study Pb-D Pb-D
GM (źg/l) GSD N GM (źg/l) GSD N GM (źg/l) GSD N
Ref. [7] Korea Busan Childrenb 2000 38.0 1.57 38 6.92 1.59 38 8.2 2.36 38 4.63 0.843
Ibid. Korea Busan Mothersc 2000 37.3 1.70 38 5.13 2.28 38 18.4 1.78 38 2.03 0.279
Ref. [8] Korea Seoul Women 1994 46.6 1.21 24 17.5 1.68 24 2.66
Ibid. Korea Chunan Women 1994 59.9 1.34 29 21.7 1.53 29 2.76
Ibid. Korea Haman Women 1994 33.4 1.33 41 20.2 1.70 41 1.65
Ibid. Korea Pusan Women 1994 46.0 1.33 47 21.6 1.67 47 2.13
Ref. [9] Malaysia Kuala Lumpur Women 1995 45.6 1.35 49 10.1 1.88 52 4.51
Ref. [10] Taiwan Tainan Women 1994 44.5 1.28 52 22.4 1.93 52 1.99
Ref. [11] Japan All Japan Women 2003 2008 15.5i 1.51 1227 20.1i 0.77
Ibid. Japan Hirosaki city Women 2008 13.8i 1.60 100 20.1i 0.69
Ibid. Japan Fukui city Women 2008 14.2i 1.44 106 20.1i 0.71
Ref. [12] Japan Abuta Women 1980 33.6 1.33 56 38.5 1.68 17 0.87
Ibid. Japan Nankodai Women 1980 52.3 1.53 20 22.0 1.83 20 2.38
Ibid. Japan Akiu Women 1980 35.0 1.35 19 25.3 1.42 15 1.38
Ibid. Japan Shironé Women 1980 32.7 1.51 19 40.7 2.09 18 0.80
Ibid. Japan Toyama Women 1980 31.9 1.39 23 56.7 1.7 16 0.56
Ibid. Japan Fukagawa Women 1980 61.6 1.44 22 55.2 1.65 24 1.12
Ibid. Japan Kanazawa Women 1980 33.1 1.39 20 41.8 1.72 19 0.79
Ibid. Japan Hikawa Women 1980 21.6 1.47 27 31.5 1.46 20 0.69
Ibid. Japan Geisei Women 1980 21.0 1.53 16 42.5 2.01 17 0.49
Ibid. Japan Tsuyazaki Women 1980 26.2 1.40 26 31.7 1.42 26 0.83
Ibid. Japan Amami Women 1980 30.7 1.37 52 25.9 1.67 21 1.19
Ibid. Japan Fukiagé Women 1980 27.6 1.57 31 23.1 1.58 26 1.19
Ibid. Japan Aira Women 1980 42.5 1.35 25 21.7 2.32 19 1.96
Ibid. Japan Misato Women 1980 45.1 1.51 21 28.5 1.59 11 1.58
Ibid. Japan Miyako Women 1980 27.8 1.47 38 17.2 1.36 10 1.62
Estimation of Dietary Pb and Cd Intake from Blood or Urine
271
Table 1 (continued)
Reference Country/Area Location Gender, Year of Pb-B Pb-Ucr Pb-D Pb-B over Pb-Ucr over
etc. study Pb-D Pb-D
GM (źg/l) GSD N GM (źg/l) GSD N GM (źg/l) GSD N
Ibid. Japan Abuta Women 1990 21.2 1.33 37 4.0 2.85 32 5.30
Ibid. Japan Nankodai Women 1990 26.2 1.50 19 9.1 1.66 19 2.88
Ibid. Japan Kanan Women 1990 30.5 1.37 18 8.7 1.54 10 3.51
Ibid. Japan Akiu Women 1990 22.8 1.52 18 4.0 2.35 15 5.70
Ibid. Japan Kitakata Women 1990 12.2 1.92 28 14.5 2.09 29 0.84
Ibid. Japan Shironé Women 1990 24.5 1.37 24 2.2 2.68 22 11.14
Ibid. Japan Toyama Women 1990 25.2 1.48 26 6.0 3.02 25 4.20
Ibid. Japan Fukagawa Women 1990 37.8 1.47 21 6.8 3.28 23 5.56
Ibid. Japan Kanazawa Women 1990 22.0 1.51 24 7.8 2.56 24 2.82
Ibid. Japan Hikawa Women 1990 25.8 1.46 33 7.8 2.96 28 3.31
Ibid. Japan Geisei Women 1990 19.9 1.30 20 4.2 2.07 17 4.74
Ibid. Japan Tsuyazaki Women 1990 17.4 1.32 16 6.6 1.85 14 2.64
Ibid. Japan Amami Women 1990 15.2 1.91 22 11.7 2.39 23 1.30
Ibid. Japan Fukiagé Women 1990 25.0 1.60 29 10.6 2.16 28 2.36
Ibid. Japan Aira Women 1990 27.8 1.39 28 10.1 2.38 28 2.75
Ibid. Japan Misato Women 1990 32.7 1.45 29 10.2 2.23 10 3.21
Ibid. Japan Miyako Women 1990 21.3 1.37 52 7.5 3.15 22 2.84
Ref. [13] China Xian Women 1997 43.4 1.32 50 7.03 2.49 50 26.1 1.64 50 1.66 0.269
Ibid. China Gongzhang Women 1997 38.2 1.46 49 4.29 1.96 49 28.1 1.48 49 1.36 0.153
Ibid. China Baoji Women 1997 21.5 1.37 50 4.03 1.89 50 36.0 1.49 50 0.60 0.112
Ref. [14] China Beijing Women 1993 1995 53.2 1.41 50 31.8 3.12 24 1.67
Ibid. China Shanghai Women 1993 1995 79.0 1.50 50 17.0 1.72 50 4.65
Ibid. China Nannin Women 1993 1995 56.0 1.47 50 37.3 1.99 50 1.50
Ibid. China Tainan Women 1993 1995 44.5 1.28 52 22.2 1.95 48 2.00
Ibid. Japan Tokyo Women 1993 1995 30.6 1.62 39 9.3 4.39 39 3.29
272
Ikeda et al.
Table 1 (continued)
Reference Country/Area Location Gender, Year of Pb-B Pb-Ucr Pb-D Pb-B over Pb-Ucr over
etc. study Pb-D Pb-D
GM (źg/l) GSD N GM (źg/l) GSD N GM (źg/l) GSD N
Ibid. Japan Kyoto Women 1993 1995 45.6 2.05 17 14.6 3.6 17 3.12
Ibid. Japan Sendai Women 1993 1995 25.3 1.48 16 15.6 1.75 16 1.62
Ref. [15] The Philippines Manila Women 1997 37 1.36 45 11.1 1.74 45 3.33
Ref. [16] Korea Seoul etc. Adults 1999 2000 28.9 30 16.4 30 1.76
Ref. [17]a Japan Shizuoka pref. Childrend 17.1 1.11 20 13.1j 1.30
Ibid. Japan Shizuoka pref. Childrene 13.0 1.09 60 13.1j 0.99
Ibid. Japan Shizuoka pref. Childrenf 14.1 1.09 36 18.8j 0.75
Ibid. Japan Shizuoka pref. Childreng 12.1 1.08 61 18.8j 0.64
Ref. [19]a Japan Unknown Childrenh 11.8i 1.1 132 16.5j 0.72
Ref. [22] Thailand Bangkok Women 1998 30.7 1.38 36 2.00 1.51 36 14.1 1.76 36 2.18 0.142
Ref. [45] Japan Hokkaido Women 1991 1998 17.1 1.87 51 5.15 1.98 51 4.90 3.44 51 3.49 1.051
Ibid. Japan Tohoku Women 1991 1998 18.9 1.74 145 1.23 2.76 145 8.34 2.53 145 2.27 0.147
Ibid. Japan Kanto-Tokai Women 1991 1998 16.9 2.18 123 1.70 2.70 123 7.79 2.09 123 2.17 0.218
Ibid. Japan Hokuriku Women 1991 1998 20.7 1.94 75 3.55 2.48 75 8.52 2.68 75 2.43 0.417
Ibid. Japan Kinki Women 1991 1998 21.5 1.99 83 2.01 3.37 83 8.47 2.40 83 2.54 0.237
Ibid. Japan Chu-Shikoku Women 1991 1998 18.8 1.90 63 2.73 3.55 63 9.36 2.27 63 2.01 0.292
Ibid. Japan Kyushu-Okinawa Women 1991 1998 20.9 1.44 67 1.94 2.72 67 5.62 2.18 67 3.72 0.345
Pb-B, Pb-Ucr and Pb-D stand for Pb in blood, in urine as corrected for creatinine and in 24-h food duplicate, respectively, unless otherwise specified. Analyses were by graphite furnace atomic
absorption spectrometry, unless otherwise specified. GM, GSD and N stand for geometric mean, geometric standard deviation and numbers of case, respectively
a
The moment method [28] was applied to estimate GM and GSD from AM and ASD
b
4 10-year-olds, boys and girls mixed
c
28-46 yr-olds
d
1 5-yr-olds from smoking families
e
1 5 year-olds from non-smoking families
f
6 14-year-olds from smoking families
g
6 14-year-olds from non-smoking families
h
1 15-year-olds
i
By inductively-coupled plasma-mass spectrometry
j
Estimated frrom market basket-based data of Matsuda [18]; see the Materials and Methods section for details of estimation procedures
Estimation of Dietary Pb and Cd Intake from Blood or Urine
273
Table 2 The database for Cd internal dose and dietary intake
Reference Country/Area Location Gender, Year of Cd-B Cd-Ucr Cd-D Cd-B over Cd-Ucr over
etc. study Cd-D Cd-D
GM (źg/l) GSD N GM (źg/l) GSD N GM (źg/l) GSD N
Ref. [7] Korea Busan Childrena 2000 1.51 1.67 38 1.69 1.60 38 11.2 2.00 38 0.135 0.151
Ibid. Korea Busan Mothersb 2000 2.74 1.75 38 1.56 1.73 38 16.7 1.84 38 0.164 0.093
Ref. [8] Korea Seoul Women 1994 1.21 1.49 24 14.3 1.71 24 0.085
Ibid. Korea Chunan Women 1994 1.03 1.78 29 19.6 1.61 29 0.053
Ibid. Korea Haman Women 1994 1.55 1.51 41 24.2 1.82 41 0.064
Ibid. Korea Pusan Women 1994 1.25 1.77 47 24.3 1.54 47 0.051
Ref. [9] Malaysia Kuala Lumpur Women 1995 0.71 2.02 49 7.31 2.58 49 0.097
Ref. [10] Taiwan Tainan Women 1994 1.11 1.39 52 10.1 1.70 52 0.110
Ref. [11] Japan All Japan Women 2003-8 1.23c 1.70 1227 20.6d 0.060
Ibid. Japan Hirosaki city Women 2008 1.37c 1.66 100 1.01 1.88 100 20.6d 0.066 0.049
Ibid. Japan Fukui city Women 2008 1.38c 1.67 106 0.64 2.30 106 20.6d 0.067 0.031
Ref. [12] Japan Abuta Women 1980 3.89 1.33 56 35.3 1.69 17 0.110
Ibid. Japan Nankodai Women 1980 4.08 1.21 20 29.5 1.65 20 0.138
Ibid. Japan Akiu Women 1980 3.15 1.38 19 26.7 1.86 15 0.118
Ibid. Japan Shironé Women 1980 3.84 1.26 19 71.4 1.57 18 0.054
Ibid. Japan Toyama Women 1980 4.81 1.6 23 63.7 1.38 16 0.076
Ibid. Japan Fukagawa Women 1980 3.68 1.29 22 27.6 1.53 24 0.133
Ibid. Japan Kanazawa Women 1980 3.16 1.48 20 50.5 1.55 19 0.063
Ibid. Japan Hikawa Women 1980 4.84 1.29 27 86.8 1.39 20 0.056
Ibid. Japan Geisei Women 1980 3.05 1.27 16 33.3 1.59 17 0.092
Ibid. Japan Tsuyazaki Women 1980 3.94 1.47 26 92.3 1.69 26 0.043
Ibid. Japan Amami Women 1980 2.92 1.47 52 19.5 1.31 21 0.150
Ibid. Japan Fukiagé Women 1980 2.64 1.34 31 23.5 1.62 26 0.112
Ibid. Japan Aira Women 1980 2.01 1.38 25 23.2 1.25 19 0.087
Ibid. Japan Misato Women 1980 2.83 1.31 21 29.2 1.41 11 0.097
274
Ikeda et al.
Table 2 (continued)
Reference Country/Area Location Gender, Year of Cd-B Cd-Ucr Cd-D Cd-B over Cd-Ucr over
etc. study Cd-D Cd-D
GM (źg/l) GSD N GM (źg/l) GSD N GM (źg/l) GSD N
Ibid. Japan Miyako Women 1980 3.31 1.43 38 30.1 1.37 10 0.110
Ibid. Japan Abuta Women 1990 2.25 1.5 37 18.9 1.97 32 0.119
Ibid. Japan Nankodai Women 1990 2.11 1.74 19 22.8 1.87 19 0.093
Ibid. Japan Kanan Women 1990 1.99 1.32 18 29.0 1.53 10 0.069
Ibid. Japan Akiu Women 1990 2.66 1.45 18 16.9 1.48 15 0.157
Ibid. Japan Kitakata Women 1990 3.27 1.6 28 58.1 1.86 29 0.056
Ibid. Japan Shironé Women 1990 3.93 1.37 24 67.3 1.65 22 0.058
Ibid. Japan Toyama Women 1990 3.76 1.49 26 64.5 1.84 25 0.058
Ibid. Japan Fukagawa Women 1990 1.63 1.52 21 32.6 2.49 23 0.050
Ibid. Japan Kanazawa Women 1990 2.57 1.83 24 45.8 1.54 24 0.056
Ibid. Japan Hikawa Women 1990 2.41 1.5 33 41.6 1.74 28 0.058
Ibid. Japan Geisei Women 1990 1.73 1.49 20 20.1 1.55 17 0.086
Ibid. Japan Tsuyazaki Women 1990 2.50 1.54 16 32.9 1.5 14 0.076
Ibid. Japan Amami Women 1990 0.96 1.48 22 16.7 1.74 23 0.057
Ref. [13] China Xian Women 1997 0.45 1.51 50 3.00 1.72 50 5.83 1.41 50 0.077 0.515
Ibid. China Gongzhang Women 1997 0.52 1.48 49 2.46 1.51 49 6.79 1.43 49 0.077 0.362
Ibid. China Baoji Women 1997 0.42 1.72 50 3.06 1.63 50 5.64 1.49 50 0.074 0.543
Ref. [14] China Beijing Women 1993-5 0.79 1.54 50 5.8 1.87 24 0.136
Ibid. China Shanghai Women 1993-5 1.18 1.40 50 6.1 2.01 50 0.193
Ibid. China Nannin Women 1993-5 1.25 1.45 50 25.0 2.05 50 0.050
Ibid. China Tainan Women 1993-5 1.11 1.39 52 10.1 1.73 48 0.110
Ibid. Japan Tokyo Women 1993-5 1.82 1.57 39 33.4 2.08 39 0.054
Ibid. Japan Kyoto Women 1993-5 1.99 1.45 17 37.0 1.55 37 0.054
Ibid. Japan Sendai Women 1993-5 2.08 1.84 16 24.8 1.88 16 0.084
Ref. [15] The Philippines Manila Women 1997 0.47 1.87 45 14.2 2.77 45 0.033
Ref. [16] Korea Seoul etc. Adults 1999-2000 1.30 12.61 0.103
Ref. [20] Japan 3 prefectures Women 1980 3.57 1.42 141 27.7 1.75 65 0.129
Ibid. Japan 3 prefectures Women 1990 1.84 1.67 165 23.8 1.73 85 0.077
Ref. [21] China Jinan Women 1996 0.48 1.44 50 6.43 1.98 50 0.075
Estimation of Dietary Pb and Cd Intake from Blood or Urine
275
Table 2 (continued)
Reference Country/Area Location Gender, Year of Cd-B Cd-Ucr Cd-D Cd-B over Cd-Ucr over
etc. study Cd-D Cd-D
GM (źg/l) GSD N GM (źg/l) GSD N GM (źg/l) GSD N
Ibid. China Baiquan Women 1996 0.29 1.50 50 5.93 1.50 50 0.049
Ref. [22] Thailand Bangkok Women 1998 0.40 1.52 36 1.47 1.48 36 7.37 1.91 36 0.054 0.199
Ref. [23] Japan Village A Women 2000-1 2.00 1.58 202 2.63 1.74 202 6.99 2.56 202 0.286 0.376
Ibid. Japan Village B Women 2000-1 1.91 1.73 202 3.47 1.7 202 19.14 2.30 202 0.100 0.181
Ibid. Japan Village C Women 2000-1 2.56 1.52 203 3.16 1.71 203 17.65 2.88 203 0.145 0.179
Ibid. Japan Village D Women 2000-1 1.65 2.35 204 3.16 1.77 204 38.91 2.18 204 0.042 0.081
Ibid. Japan Village E Women 2000-1 3.61 1.63 569 4.08 1.74 569 51.99 2.25 569 0.069 0.078
Ref. [45] Japan Hokkaido Women 1991-1998 2.17 1.52 51 5.69 1.39 51 18.7 1.88 51 0.12 0.30
Ibid. Japan Tohoku Women 1991-1998 1.42 2.12 145 3.16 2.00 145 20.7 2.54 145 0.07 0.15
Ibid. Japan Kanto-Tokai Women 1991-1998 1.80 1.51 123 3.42 1.67 123 23.0 2.12 123 0.08 0.15
Ibid. Japan Hokuriku Women 1991-1998 3.74 1.50 75 7.78 2.18 75 53.2 1.72 75 0.07 0.15
Ibid. Japan Kinki Women 1991-1998 1.02 2.26 83 2.40 2.38 83 23.4 2.13 83 0.04 0.10
Ibid. Japan Chu-Shikoku Women 1991-1998 2.02 1.58 63 5.27 1.92 63 27.0 1.92 63 0.07 0.20
Ibid. Japan Kyushu-Okinawa Women 1991-1998 1.71 1.62 67 4.10 1.74 67 20.9 1.89 67 0.08 0.20
Analyses were by graphite furnace atomic absorption spectrometry, unless otherwise specified. Cd-B, Cd-Ucr and Cd-D stand for Cd in blood (unit, źg/l), in urine as corrected for
creatinine (unit, źg/g creatinine) and in 24-h food duplicate (unit, źg/day) unless otherwise specified
a
4 10-year-old, boys and girls mixed
b
28 46-year-old
c
By indusctively coupled plasma-mass spectrometry
d
Estimated from market basket-based data of Matsuda [18]; see the Materials and Methods section for details of estimation procedures
276
Ikeda et al.
Estimation of Dietary Pb and Cd Intake from Blood or Urine 277
Analysis for Lead in Blood
For graphite furnace atomic absorption spectrometry (GFAAS) analysis, 100 źl blood
sample was taken into an acid-washed tube and mixed with 900 źl of a 1 to 1 mixture of
10% Triton X-100 in water and 10% diammonium hydrogenphosphate in water. An aliquot,
10 źl, of the final mixture was introduced into a GFAAS system by use of an auto-sampler.
The GFAAS was Hitachi type Z-8270 (Hitachi-naka, Hitachi, Japan) equipped with a tube-
type cuvette, and the measurement was made at 283.3 nm using the standard addition
method as previously described [27]. The average of two measurements was taken as a
representative value.
Inductively coupled plasma-mass spectrometry (ICP-MS) analysis was conducted after
acid digestion of 0.1 ml of blood sample by heating by microwave in a closed container,
and the digest was taken up with ultra-pure water (final volume; 5 ml), and analyzed by the
method as previously described [11].
Statistical Analysis
Log-normal distributions were assumed for Cd and Pb in food, blood or urine so that
geometric means (GMs) and geometric standard deviations (GSDs) were taken as
representative parameters for the distributions. In case original data were given in terms
of arithmetic means (AMs) and arithmetic standard deviations (ASDs), they were converted
to GMs and GSDs by use of the moment method [28] for uniformity of data presentation.
In case only medians were given in original articles, the medians were taken as if
they had been GMs. Possible significant correlation between two parameters was
examined by simple regression analysis. Smirnov test for extreme values was applied as
necessary.
Results
Quantitative Correlation Between the Measures by GFAAS and ICP-MS
In order to compare the results by GFAAS analysis with that by ICP-MS, 20 blood samples
of various Pb concentrations (24.0 42.8 źg/l blood by ICP-MS) were analyzed for Pb by
both methods. When the results (in źg Cd/l blood) by the ICP-MS and GFAAS methods
were taken on the x- and y-axis, respectively, there was a significant correlation between the
paired results with a regression line of y=0.677+0.77x (r=0.797, p<0.01). The analysis
showed that while the correlation between the two sets of the results were close and
significant, the difference between the two values were significant (p<0.01 by paired t test).
Comparison of the AM values (29.4 and 23.3 źg Cd/l blood by the ICP-MS and GFAAS,
respectively) suggests that ICP-MS would give greater values than GFASS by 26%.
Availability of the Data
Literature survey for publications in 1990s and 2000s for a combination of Pb-B (or Pb-U)
and Pb-D, or Cd-B (or Cd-U) and Cd-D gave 14 reports on Pb and 15 reports on Cd, as
summarized in Table 1 (for Pb) and Table 2 (for Cd). The basic parameters on data
availability are presented in Table 3.
Table 3 Basic parameters of distribution
A Pb (14 reports) B Cd (15 reports)
Parameter Pb-B Pb-Ucr Pb-D Ratio Cd-B Cd-Ucr Cd-D Ratio
GM GSD Nb GM GSD Nb GM GSD Nb Pb-B Pb-Ucr Pb-D Pb-D GM GSD Nb GM GSD Nb GM GSD Nb Cb-B Cb-Ucr Cb-D Cb-D
(źg/l) (źg/g cr) (źg/day) over over over over (źg/l) (źg/g cr) (źg/day) over over over over
Pb-D Pb-D Pb-B Pb-Ucr Cb-D Cb-D Cb-B Cb-Ucr
Na 68 67 68 13 13 13 68 59 68 68 13 68 5.2 68 67 68 20 20 20 68 64 68 68 20 68 20
AM 30.3 1.5 59.7 3.7 2.4 66.8 18.3 2.1 34.7 2.3 0.3 0.7 52.9 2.13 1.56 80.1 3.16 1.79 122.7 27.6 1.81 56.4 0.09 0.20 13.4 8.2
ASD 13.8 0.2 146.3 2.0 0.6 33.4 12.1 0.6 25.0 1.7 0.3 0.5 42.8 1.15 0.22 163.0 1.69 0.26 121.3 19.2 0.36 80.5 0.04 0.14 5.2 7.2
MED 27.7 1.44 36 3.55 2.48 51 16.4 1.95 26 2.0 0.3 0.5 61.0 1.99 1.51 39 3.11 1.74 79 23.3 1.74 34 0.1 0.2 13.1 6.1
Min 11.8 1.08 16 1.23 1.51 36 2.2 1.36 10 0.5 0.1 0.1 19.7 0.29 1.21 16 0.64 1.39 36 5.64 1.25 10 0.0 0.0 3.5 1.8
Max 79.0 2.2 1227 7.0 3.6 145 56.7 4.4 145 11.1 1.1 2.0 53.9 4.84 2.35 1227 7.78 2.38 569 92.3 2.88 569 0.3 0.5 30.2 32.2
a
Number of data sets
b
Number of cases studied in each report
278
Ikeda et al.
Estimation of Dietary Pb and Cd Intake from Blood or Urine 279
In the 14 reports on Pb, 68 pairs of Pb-B and Pb-D were available, but some papers did
not give variation parameters such as GSD. The number of articles reporting Pb-U in
combination with Pb-D was limited (13 papers). The distribution of the reported values for
Pb-D was markedly skewed, but the AM was about 18 źg/day with the maximum of
56.7 źg/day. The highest GM for Pb-B was 79.0 źg/l.
In case of Cd for which 15 reports were available, 68 pairs of Cd in blood (Cd-B) and in
food duplicates (Cd-D) were found. Reflecting the fact that the populations studied were
residents in non-polluted areas, the average Cd-D was less than 30 źg/day, but the
maximum was as high as 92.3 źg/day. The number of articles reporting both Cd-U and Cd-D
was limited to 20. The average and the maximum Cd-Ucr were 3.16 and 7.78 źg/g cr,
respectively.
Relation of Pb-D with Pb-B and with Pb-U
Regression analysis was conducted (taking Pb-D as an independent variable and Pb-B or
Pb-Ucr as a dependent variable) to examine the quantitative effects of Pb-D on Pb-B as well
as Pb-Ucr. The analysis with Pb-B (Eq. 1 in Table 4, Fig. 1) showed that there was a
significant correlation between the two parameters (r=0.360, p<0.01), as expected. Only
13 cases were available for Pb-Ucr. The correlation of Pb-Ucr with Pb-D was weak and
insignificant (p>0.10; Eq. 2 in Table 4), but that with Pb-B was close and significant (p<
0.01; Eq. 3).
With Pb-B and Pb-D as an independent and a dependent variable, respectively (Eq. 4
in Table 4), the correlation was significant (p<0.01), and the slope was positive [0.317
(źg/daily diet per źg/l blood) with the 95% range of 0.115 and 0.517]. The observation as
a whole was taken to suggest that Pb-D can be estimated from Pb-B, but the variation
may be wide.
In fact, when the Pb-D over Pb-B ratio was taken as a dependent variable (with Pb-B as
an independent variable) (Eq. 5 in Table 4), the slope (the 95% range) was negative, i.e.
-0.011 (-0.018 to -0.003) suggesting that the role of Pb-D would decrease when total body
burden (Pb-B as an indicator of the total body burden) be high. In other words, the non-
dietary burden such as exposure to Pb-polluted atmospheric air may gain weight, as a
function of total body burden, as to be discussed later.
An attempt was made to estimate the Pb-D (GM) that would induce Pb-B at given levels,
such as 15 źg/l [the typical Pb-B level among current day Japanese women; the three lines
for ref. 11 in Table 1], taking advantage of the regression analysis with Pb-B (GM) as an
independent variable and Pb-D (GM) as a dependent variable as described previously
(Fig. 1). The three crosses of a hypothetical vertical line at 15 źg/l with the regression line
(and the 95% range curves in parenthesis) gave Pb-D of 14 (10 18) źg/l. Similar regression
analysis taking Pb-B (GM) on the horizontal axis and Pb-D (GSD) on the vertical axis gave
a regression line (Eq. 6 in Table 4) in which the slope was shallow but significant. The
regression equation gave about 2.3 for 15 źg/l Pb-B. The factor of 2.3 may suggest a 68%
variation range for Pb-D on an individual basis (Fig. 2).
The Pb-B over Pb-D ratios were calculated for each case with Pb-B in źg/l and Pb-D in
źg/day, and listed in the second right-most column in Table 1. A regression analysis was
conducted taking Pb-B (inźg/l) as an independent variable and the Pb-B over Pb-D ratio as
a dependent variable. A case with the Pb-B over Pb-D ratio of 11.14 was excluded as an
extreme value after application of Smirnov test. The calculation with 67 cases gave a
regression line with r=0.210 (p<0.10), a slope=0.020 (the 95% range; 0.000 to 0.044) and
an intercept=1.588 (Eq. 7 in Table 4); the correlation coefficient of 0.210 was of borderline
Table 4 Parameters of regression equations
Equation no. Indepen-dent variable Dependent variable Intercept Slope No. of cases Correlation coefficient| P
(Ä…)(²) (95% interval)
Eq. 1 Pb-D Pb-B 22.810 0.41 0.15 0.670 68 0.360 <0.01
Eq. 2 Pb-D Pb-Ucr 2.645 0.07 -0.049 0.19 13 0.37 >0.10
Eq. 3 Pb-B Pb-Ucr -0.120 0.14 0.05 0.240 13 0.7 <0.01
Eq. 4 Pb-B Pb-D 8.737 0.32 0.12 0.519 68 0.360 <0.01
Eq. 5 Pb-B Pb-D over Pb-B 0.998 -0.011 -0.018 0.003 68 0.32 <0.01
Eq. 6 Pb-B Pb-D (GSD) 2.447 -0.010 -0.022 0 59 0.21 >0.10
Eq. 7 Pb-B Pb-B over Pb-D 1.588 0.020 0.000 0.041 67a 0.210 <0.10
Eq. 8 Cd-D Cd-B 0.810 0.05 0.04 0.06 68 0.79 <0.01
Eq. 9 Cd-B Cd-D -0.343 13.16 10.47 15.66 68 0.79 <0.01
Eq. 10 Cd-D Cd-Ucr 1.7 0.070 0.020 0.12 20 0.570 <0.01
Eq. 11 Cd-Ucr Cd-D 6.22 4.62 1.32 7.916 20 0.570 <0.01
Eq. 12 Cd-B Cd-D over Cd-B 14.950 -0.711 -1.802 0.38 68 0.16 >0.10
Eq. 13 Cd-Ucr Cd-D over Cd-Ucr 14.101 -1.871 -3.777 0.03 20 0.44 <0.10
Unless otherwise specified, Pb-B, Pb-Ucr, Pb-D, Cd-B, Cd-Ucr and Cd-D are GM values in źg/l, źg/g cr or źg/day
a
One case with the Pb-B over Pb-D ratio of 11.14 was depeted as an extreme value after Smirnov test for extreme value
280
Ikeda et al.
Estimation of Dietary Pb and Cd Intake from Blood or Urine 281
Fig. 1 Relation of Pb in blood and Pb in daily diet. A regression analysis was conducted with Pb in blood
(Pb-B) as an independent variable and Pb in daily diet (Pb-D) as a dependent variable. Both Pb-B (źg/l) and
Pb-D (źg/day) are GM values for the study sites. The line in the middle is a calculated regression line (for the
equation parameters, see Table 4), and the curves on both sides are the 95% ranges of the means. Each dot
represents one study site
significance (p<0.10). Based on the equation, the best estimate of the Pb-B over Pb-D ratio
for Pb-B of 15 źg/l was 1.9 or about 2.
Dietary Burden and Internal Dose of Cd
The correlation analysis showed that Cd-B correlated significantly (p<0.01) with Cd-D,
with a significant correlation coefficient of 0.792 (Eq. 8 in Table 4). When Cd-B was taken
as an independent variable, the lower 95% limit of the slope (²) was 10.47, which was
clearly positive (i.e. >0) (Eq. 9 in Table 4, Fig. 3).
The number of studies of Cd-U paired with daily dietary intake data was limited and
only 20 pairs of Cd-Ucr and Cd-D were available. Similar analysis revealed that, taking
Cd-D and Cd-Ucr as an independent and a dependent variable, respectively, the slope was
positive (0.070) suggesting that Cd-U would increase as an increasing function of Cd-D
(Eq. 10 in Table 4). The correlation, r=0.570, was statistically significant (p<0.01) (Fig. 4).
The analysis taking Cd-B as an independent variable and the ratio of Cd-D over Cd-B as
a dependent variable (Eq. 12 in Table 4) revealed that the ratio stayed essentially unchanged
with no response to an increase in Cd-B. Although the correlation (r=0.158) was weak and
statistically insignificant (p>0.10), the 95% range for the slope was -1.802 to 0.381,
indicating that the regression line was essentially in parallel to the horizontal axis. A similar
Fig. 2 No significant changes in GSD of Pb in daily diet as a function of Pb in blood. A regression analysis
was conducted with Pb in blood (Pb-B; GMin źg/l for the study site) as an independent variable and GSD
(dimensionless) of Pb in daily diet (Pb-D) as a dependent variable. The meaning of the line in the middle and
two curves on both sides, as well as that of the dots are as in Fig. 1. For equation, see Table 4
282 Ikeda et al.
Fig. 3 Relation of Cd in blood and Cd in daily diet. A regression analysis was conducted with Cd in blood
(Cd-B) as an independent variable and Cd in daily diet (Cd-D) as a dependent variable. Both Cd-B (źg/l) and
Cd-D (źg/day) are GM values for the study sites. The meaning of the line in the middle and two curves on
both sides, as well as that of the dots are as in Fig. 1. For equation, see Table 4
analysis with Cd-Ucr and the ratio of Cd-D over Cd-Ucr (Eq. 13) also gave a regression line
with no significant increase of the ratio with increasing Cd-Ucr.
Discussion
It appears to be the case that 50 to 100 źg/l is a critical concentration when GFAAS is
employed for Pb-B analysis; for example, a coefficient of variation as large as 20% was
reported when blood samples containing 100 źg Pb/l was analyzed [29]. As the target Pb-B
concentrations in the present study were well below these levels (e.g. Table 1), it was
thought essential to make a compatibility analysis in results between conventional GFAAS
and newly developed ICP-MS. The results showed that there was a close correlation
between the GFAAS results and ICP-MS result, and that ICP-MS would give greater values
than GFAAS by 26%. In contrast, GFAAS has been well accepted for both Cd-B and Cd-U
analyses in a wide range [30], suggesting no need for compatibility tests with other
analytical methods in case of Cd analyses.
The present analyses with data in 14 reports on Pb and 15 reports on Cd in blood, urine
and 24-h diet samples suggested that it should be possible to estimate both Pb-D and Cd-D
Fig. 4 Relation of Cd in blood and Cd in daily diet. A regression analysis was conducted with Cd in urine
after correction for creatinine (Cd-Ucr) as an independent variable and Cd in daily diet (Cd-D) as a dependent
variable. Both Cd-Ucr (źg/g cr) and Cd-D (źg/day) are GM values for the study sites. The meaning of the
line in the middle and two curves on both sides, as well as that of the dots are as in Fig. 1. For equation, see
Table 4
Estimation of Dietary Pb and Cd Intake from Blood or Urine 283
from Pb-B and Cd-D. The Cd-B-based estimation for Cd-D appears to be quite possible as
the Cd-D over Cd-B ratio stayed unchanged irrespective of Cd-B. It was also the case when
Cd-Ucr was employed in place of Cd-B. In contrast, the estimation for Pb-D from Pb-B
apparently needs careful evaluation of concurrent intensity of exposure to Pb, because the
ratio of Pb-D over Pb-B may decrease as a function of increasing intensity of Pb exposure
as represented by Pb-B (Eq. 7 in Table 4).
Such difference between Cd and Pb in the relationship of dietary exposure (Cd-D and
Pb-D) with total body burden (as expressed by Cd-B or Cd-Ucr, and Pb-B) is in agreement
with previous observation on the populations environmentally exposed to Pb and Cd.
Namely, the exposure to Cd is almost exclusively via foods as Cd in the atmosphere is
generally very low and contributes little to total body burden [2], whereas contribution of
air-borne Pb may exceed 50% of total Pb burden even for general populations [2] as a
function of the extent of urban air pollution with Pb [1]. In this sense, the gap between the
1980 s studies-based estimate by Carrington et al. [31, 32] and the present estimation as to
be discussed below may be attributable to the different intensity of environmental Pb
pollution, especially that of urban air.
Based on the studies of Ryu et al. [33] and Sherlock et al. [34 36], Carrington et al. [31]
estimated 10, 10, 30 źg Pb/100 ml blood (or 100, 100 and 300 źg Pb/l blood) as Pb-B
levels of concern for children, pregnant women and adults and figured out Pb-D of 60, 250
and 750 źg Pb/day by use of conversion factors [=Pb-B (inźg/100 ml)/Pb-D (in źg/day)
[31]] of 0.16, 0.04 and 0.04 for the three groups, respectively. The Pb-D of 750 źg/day is
however apparently too high when the present day Pb-D is considered; for example, the Pb-D
level is well below 60 źg/day in Japan (Table 1). Pb-B has also been reduced to <20 źg/l (or
<2 źg/100 ml; Table 1). Thus, the conversion factor of 0.04 (or 0.40 when Pb-B is expressed
in źg/l) for adults for example, will be no longer valid.
The present analysis made it clear in addition, that the relation of Pb-B with Pb-D is not
constant but may vary as a function of Pb-B (Eq. 7 in Table 4) so that the ratio, calculated
as Pb-B (inźg/l) over Pb-D (inźg/day) e.g. for adult Japanese women with current Pb-B of
around 15 źg/l (in the three lines under ref. 11 in Table 1) should be around 1.9 (Eq. 7 in
Table 4) as described above. For those with Pd-B of about 30 źg/l, the best estimate will be
2.2 (Eq.7 in Table 4). No data are available to compare the ratio for children directly with
that for adult people in Japan. Nevertheless, the data made available by Moon et al. [7]
based on the study in Busan, Korea, suggest that the ratio for children may be twice as high
as that for their mothers (Table 1).
Possible effects of insufficient calcium (Ca) intake on Pb-B among children have been a
matter of concern in recent years. Three reports are available which unanimously suggest
that Pb-B would be higher among those who take Ca only insufficiently. In a study in
Mexico city [37] in which 200 cases of children (at the age of <13 to 50+ months) were
analyzed, those (n=50 each) with daily Ca intake of <360, 360 to <449, 449 to <624 and
624 mg/day (estimated by food intake frequency questionnaires) had Pb-B [GM estimated
from AM and ASD by the moment method [28]] at 9.75, 9.03, 8.00 and 7.64 źg/100 ml,
respectively. P-values for the differences in Pb-B from the lowest Ca intake group were
>0.10, >0.10, <0.10 and <0.05, respectively.
Elias et al. [38] reported that Pb-B [2.96 źg/100 ml as GM estimated by the moment
method [28]] of 225 primary school children (in Kuala Lumpur, Malaysia) decreased as a
reverse function of dietary Ca intake (407 mg/day as AM estimated by food frequency
questionnaire); the slope (with Ca intake and Pb-B on the horizontal and vertical axis,
respectively), was <0 (i.e., -0.011) with p=0.014. In a village in Mexico, a study [39] on
752 residents including 202<15 year-old children showed that Pb-B was lower (7.2, 6.9
284 Ikeda et al.
and 6.0 źg/100 ml as GM, respectively) among those (n=243 to 247) who took more Ca (i.e.
505, 505 706, and 706 mg/day; estimated by food frequency questionnaires).
It is known through national surveys that Ca intake is insufficient especially among young
children in Japan [26]. Thus, more than 50% of children at the ages of 1 2 and 3 5 years take
Ca less than the adequate intake (AI; 40), and the median intake is about the AI at 6 9 years
of age [26]. Thus, insufficient intake of Ca among children should be taken as a dietary factor
to increase sensitivity of Japanese children to Pb toxicity. Of interest in this connection is the
observation that Pb in Ca supplements does not affect Pb-B, possibly because Pb absorption
in the digestive tract is suppressed by co-existing abundant Ca in the pellets [41].
Different from adult cases, poor personal hygiene of using dirty hands when eating foods is
an additional factor to increase lead exposure of children. Freeman et al. [42] observed
increased Pb burden through foods such as banana and hot dog when taken with spoilt hands.
There are several limitations in the present analysis. Compared with the number of pairs
of Cd-D and Cd-B (60 in total), only 13 pairs were available for the analysis between Cd-D
and Cd-U. More data are apparently desired to examine possible association between Cd-D
and Cd-U, because urine samples are more readily available than blood samples in field
surveys. In the case of Pb, the limited number for Pb-U is not necessarily a matter of serious
concern in evaluation because poor correlation of Pb-U with Pb-B is well-known especially
when Pb exposure is low [43].
It was observed in the present study that the ICP-MS would be give values about 26%
larger than the values by GFAAS. Another factor to induce bias relates to the methods to
estimate recent metal burden for Japanese populations. The market basket method was
employed by Matsuda [18] to establish the estimates, whereas the food duplicate method
was employed in other studies. The difference might induce systematic bias in evaluation.
For example, the data by Watanabe et al. [12] on 1990 survey gave a number weighted
average of 19.1 źg/day for Pb. It was 40.8 źg/day for Cd. In contrast, Toyoda et al. [44],
using the market basket method assumedly similar to that used by Matsuda [18], reported that
daily Pb and Cd intakes by Japanese population in 1990 were 41 źg/day and 26 źg/day,
respectively. In estimating the Pb-B over Pb-D ratios based on Kaji [17], Takagi et al. [19]
Ikeda et al. [11], the estimation of dietary intake was based on Matsuda [18]. In Takagi [19]
and Ikeda et al. [11], Pb-B for example was measured by the ICP-MS method. Introduction of
factors for converting a market basket-based value to a food duplicate-based one (e.g. division
by factor 2) and a ICP-MS-based value to a GFASS-based value (-ca. 20%) would give Pb-B
(in źg/l) over Pb-D (in źg per day) ratio of 1.3 to 2.0 for Kaji [17], 1.1 for Takagi et al. [19]
and 1.1 to 1.2 for Ikeda et al. [11].
In over-all evaluation, it appears prudent to conclude that dietary intake of Pb and Cd can be
estimated from Pb and Cd in blood, as well as Cd in urine. Nevertheless, care should be taken
for the estimation of Pb-D from Pb-B as the ratio of Pb-D over Pb-B may increase as Pb-B
decreases. The best estimate for Pb-B (źg/l)/Pb-D (źg/day) will be about two for adults, and the
ratio for children may be higher possibly by a factor of about two [7]. It should be noted that in
the case of children, poor personal hygiene and possible effects of nutritional factors such as
insufficient calcium intake (typically in Japan) may need to be taken into consideration.
Acknowledgments A part of this study was supported by Grants-in Aid from Food Safety Commission,
Japan (No.0802) for fiscal years 2008 2009.
Thanks are due to the administration and staff of Kyoto Industrial Health Association, Kyoto, Japan, for
their interest in and support to this study.
Conflicts of Interest The authors declare that they have no conflicts of interest.
Estimation of Dietary Pb and Cd Intake from Blood or Urine 285
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