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Dietary intake of cadmium by children and adults from Germany using duplicate portion sampling
The Science of the Total Environment 285 (2002) 11–19
Dietary intake of cadmium by children and adults from Germany using duplicate portion sampling ¨ Michael Wilhelma,*, Jurgen Wittsiepea, Petra Schreya, Ursula Buddea, Helga Idelb a
¨ Institute of Hygiene, Social- and Environmental Medicine, Ruhr-University-Bochum, Universitatsstr. 150, 44801 Bochum, Germany b ¨ ¨ ¨ Institute of Hygiene, Heinrich-Heine-University Dusseldorf, Universitatsstr. 1, 40225 Dusseldorf, Germany Received 3 August 2001; accepted 26 November 2001
Abstract The dietary intake of cadmium was studied among children and adults from Germany. The study area comprised the highly industrialized Ruhr district as well as the North Sea island Amrum. A total of 229 duplicate samples were collected from 49 individuals between December 1994 and May 1995. The sampling period for each participant was either 3 or 7 days. Cadmium concentrations in duplicate samples were measured by atomic absorption spectrometry. The daily cadmium intakes (geometric mean) for 4 different groups of individuals distributed as follows: for small children (mean age: 1.8 years) from the Ruhr district 0.17 mgy(kgbw Øday) wrange: 0.02 – 1.62 mgy(kgbwØday)x, for children (mean age: 3.8 years) from the Ruhr district 0.49 mgy(kgbw Øday) wrange: 0.11 – 2.06 mgy(kgbwØday)x, for children (mean age: 3.9 years) living on the North Sea island Amrum 0.35 mgy(kgbwØday) wrange: 0.09 – 1.13 mgy (kgbwØday)x and for adults (mean age: 40.9 years) from the Ruhr district 0.37 mgy(kgbwØday) wrange: 0.05 – 1.32 mg y(kgbwØday)x. Compared to the provisional tolerable weekly intake (PTWI) of 7 mgy(kgbw Øweek) proposed by the WHO the dietary intake of cadmium was rather high. The geometric mean and maximum intake values for the different groups ranged between 24.3 – 55.7% and 62.7 – 120.7 respectively of the PTWI. We therefore conclude, that the cadmium exposure of the population needs to be reduced in order to minimize the risk of adverse health effects related to this metal. 䊚 2002 Elsevier Science B.V. All rights reserved. Keywords: Cadmium; Dietary intake; Duplicate study; Children; Adults; Provisional tolerable weekly intake; PTWI; Germany
1. Introduction Cadmium toxicity is well known and the health effects of cadmium exposure have been reviewed ¨ recently (Jarup et al., 1998). Among these, renal tubular damage appears to be one the critical health * Corresponding author. Fax: q49-234-3214-199. E-mail address: [email protected] (M. Wilhelm).
effects of cadmium exposure in the general population. The International Agency for Research on Cancer concluded in 1993 that there was sufficient evidence to classify cadmium as a human carcinogen. Sources of human and environmental cadmium exposure have been reviewed by the World Health Organization (WHO, 1992a,b). Food is the major source of cadmium exposure in the general non-
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M. Wilhelm et al. / The Science of the Total Environment 285 (2002) 11–19
smoking population. Natural and anthropogenic sources such as industrial emissions, applications of fertilizers and sewage sludge from farming have led to the contamination of soils. As a result, an increased cadmium uptake occurs by crops and vegetables grown for human consumption. Additionally, airborne cadmium will contribute to the cadmium content of vegetables and grain. Since cadmium particularly accumulates in liver and kidneys of animals, offal may also be an important source of cadmium in the diet. A recent study from the USA revealed that only pasta, cereal, iceberg lettuce and baked potatoes contributed to almost 50% of the dietary cadmium intake (Ryan et al., 2001). Estimates of health risks due to dietary cadmium intake are periodically carried out and compared to the provisional tolerable weekly intake (PTWI) recommended by the FAOyWHO (WHO, 1993). For this purpose the use of the duplicate method is especially suitable and has been successfully applied by our working group in several studies (Wilhelm et al., 1995a,b; Schrey et al., 1998, 2000; Wittsiepe et al., 2001; Wilhelm et al., 2002). In our study (sampling period 1988–1989) with children living in an industrial area of Germany (Duisburg, North Rhine-Westphalia), we calculated a weekly cadmium intake of 2.1 mgy (kgbwØweek), which corresponded to 30% of the PTWI (Wilhelm et al., 1995b). An even higher cadmium intake of 2.7 mgy(kgbwØweek) was found through duplicate samples collected in 1995 from German children living on a North Sea island (Schrey et al., 2000). Considering the recent cad¨ mium health risks reviewed by Jarup et al. (1998), this low margin between the actual PTWI and the dietary cadmium intake is of actual public health concern. They estimated that at an average cadmium intake of 70 mgyday (corresponding to the present PTWI), 7% of the general adult population would be expected to develop cadmium-induced kidney lesions. Consequently the authors have recommended lowering the current PTWI. In this study, we report the results on cadmium dietary intake from our German duplicate studies, from samples collected in 1994 and 1995. The study groups comprised of children at different ages as well as adults, originating from industrial
areas and from a remote area. Through this grouping, we wanted to find out if there were differences in the cadmium dietary intake between children and adults, between children at different ages as well as between a rural and an industrialized region. 2. Subjects and methods 2.1. Subjects and study design Duplicate portions (ns229) were collected from 49 individuals between December 1994 and May 1995. The study was undertaken in the Ruhr district as well as on the North Sea island Amrum. The Ruhr district is a highly industrialized area of North-Rhine-Westphalia, Germany. The North Sea island Amrum is a remote area of Germany. Participants were children aged between 1.3 and 5.2 years and adults aged between 24 and 64 years, divided into four groups. Details referring to the groups are summarized in Table 1. Results concerning trace element intakes including cadmium intake of children from the North Sea island have been published recently (Schrey et al., 2000) in detail. A short medical check-up revealed no acute or chronic illnesses, except for some infections of the upper respiratory tract. All participants consumed a mixed diet. None of the participants were on a special diet and no participant was vegetarian. The dietary cadmium intakes were measured by the duplicate method, according to the WHOGuidelines (WHO, 1985). Duplicate portions of all consumed food, beverages and snacks were collected in precleaned containers. In addition, the parents of the children and the participating adults kept a food diary in which the kind, art of preparation and amount of the food ingested was entered. All food items and beverages were recorded in household measuring units. Additionally all parents and participating adults completed a questionnaire. The questions addressed items which could potentially influence the dietary cadmium intake, such as kind of industry near the home, exposure to tobacco smoke within their environment, frequency of consuming certain foods (e.g. home grown vegetables), etc.
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Table 1 Summarized data on age, sex, place of residence, number of sampling days, and number of duplicate samples with respect to the four groups participating in the German duplicate studies (sampling period December 1994 to May 1995) Group
Number of participants
Age wyearsx (mean, range)
Number of females (f) and males (m)
Place of residence
Number of sampling days
Number of duplicates
A
7
1.8 1.3 – 3.0
4 f; 3 m
Ruhr district
7
47a
B
14
3.8 1.8 – 5.2
7 f; 7 m
Ruhr district
3
42
C
14
3.9 1.5 – 5.1
7 f; 7 m
Amrum
7
98
D
14
7 f; 7 m
Ruhr district
3
42
a
40.9 24 – 64
2 samples were excluded from the study due to incomplete sampling.
2.2. Analytical procedure The food samples were collected by us each day, weighed, homogenized, lyophilized and frozen at y20 8C. Approximately 500–600 mg of the lyophilisate were weighed in Teflon tubes (high performance microwave digestion, Microwave Laboratory Systems GmbH). After addition of 2 ml HNO3 (p.a., 65%, Merck) and 1 ml H2O2 (p.a., 30%, Merck), the samples were digested with a microwave system (high performance microwave digestion, MLS 1200 mega, Microwave Laboratory Systems GmbH). The temperature-power-program was: 2 min, 200 W; 1 min, 0 W; 2 min, 350 W; 1 min 0 W; 2 min 450 W; 1 min 0 W; 3 min 550 W. The analysis was carried out by atomic absorption spectrometry (Zeeman 3030 with HGA 600, Perkin–Elmer). Analytical conditions are already described in details elsewhere (Wilhelm et al., 1989). The detection limit was 4 mgykgdry weight (500 mg lyophilisate). Cadmium concentrations below the detection limit were only observed in the group of small children (mean age: 1.8 years). Cadmium levels lower than the detection limit was estimated by substituting one-half of the detection limits. The accuracy of the method was confirmed by analyzing reference materials (EQC Sample No. 965 B, National Food Administration, Sweden) and HDP-Reference Material (Laboratory of Food Chemistry, Food Research Institute, Agricultural
Center of Finland). The analyzed values were within the certified reference range. The laboratory participated successfully in an interlaboratory quality control study, organized by the National Food Administration, Sweden. In addition, our lab acted as reference laboratory for the establishment of certified concentrations of heavy metals in diet reference materials (Jorhem et al., 1995). 2.3. Calculation of dietary intake and statistics On the basis of the concentrations measured in the food duplicates the daily dietary intake of cadmium was calculated. The weekly intakes were obtained by adding the seven daily intakes from each individual. In cases where the sampling period was only 3 days, the weekly intake was then calculated. The intake rates were additionally related to the body weight of the participants and to their body surface area. The body surface area was calculated by using the equation of DuBois and DuBois: body surface area wcm2xs71.84 * weight wkgx 0.425 * height wcmx0.725 (Schmidt and Thews, 1990). The statistical calculations were performed with the data software system ‘Statistica’ 5.5 or 6 (StatSoft, Inc., Tulsa, OK, USA). To evaluate statistical significance the ‘Mann–Whitney U-test’ and ANOVA were used. The correlations were done using the Pearson Product–Moment Correlation. To characterize the mean location of the
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data the geometric mean was preferred since data are log-normally distributed.
Table 3 Daily dietary intake of cadmium for the four different groups A – D (details are given in Table 1)
3. Results Cadmium levels of the food duplicates with a geometric median value of 9.9 mgykgdry weight were low in the small children (group A) (P-0.001 compared with the other groups). Cadmium levels of 13 samples of group A children were below the detection limit. The highest cadmium concentrations of duplicate samples were found in adults (group D) (geometric mean: 62.0 mgykgdry weight P-0.001 compared with the other groups). Cadmium levels of duplicate samples tended to be higher for the children living in the industrialized region (group B), when compared with those from the rural area (group C) (geometric mean values: 29.4 and 22.8 mgykgdry weight. Ps0.09). In Tables 2 and 3 basic statistical data of the weekly (Table 2) and daily (Table 3) dietary intake of cadmium for the four study groups are shown. A comparison of the dietary cadmium intake of the four groups is given in Fig. 1. Cadmium intake was low for the small children (P-0.001) com-
mgyd Range Median 90. P. GMa CI of GMb mgy(kg body Range Median 90. P. GMa CI of GMb mgy(m2 body Range Median 90. P. GMa CI of GMb a b
Group A
Group B
Group C
Group D
0.3 – 14.9 2.4 9.6 2.0 1.4 – 2.8
1.8 – 38.9 7.6 26.5 8.2 6.3 – 10.7
1.6 – 13.9 6.1 10.0 2.0 1.4 – 2.8
3.7 – 67.3 27.6 54.3 26.4 21.4 – 32.7
Øday) 0.02 – 1.62 0.21 0.73 0.17 0.12 – 0.25
0.11 – 2.06 0.44 1.49 0.49 0.38 – 0.63
0.09 – 1.13 0.36 0.62 0.35 0.32 – 0.38
0.05 – 1.32 0.41 0.85 0.37 0.30 – 0.47
2.3 – 26.4 8.9 15.1 8.5 7.7 – 9.3
2.1 – 44.0 15.5 30.5 14.5 11.7 – 18.1
weight
Øday) 0.6 – 34.9 2.7 – 48.8 4.9 10.7 16.6 37.2 3.9 11.9 2.8 – 5.7 9.3 – 15.3
surface area
GMsgeometric mean. CIs95%-confidence interval.
Table 2 Weekly dietary intake of cadmium for the four different groups A – D (details are given in Table 1)
mgyweek Range Median 90. P. GMa CI of GMb mgy(kg body Range Median 90. P. GMa CI of GMb mgy(m2 body Range Median 90. P. GMa CI of GMb a b
Group A
Group B
Group C
Group D
7.4 – 50.4 17.0 50.4 19.5 10.1 – 37.5
23.6 – 177.5 55.6 170.8 65.1 43.8 – 96.7
26.6 – 69.8 45.8 57.2 42.4 35.5 – 50.6
29.4 – 583.2 216.9 336.5 205.0 138.0 – 303.0
0.5 – 5.5 1.5 5.5 1.7 0.8 – 3.4
1.6 – 8.5 3.6 8.2 3.9 2.7 – 5.6
1.7 – 4.4 2.7 3.4 2.6 2.3 – 3.0
0.4 – 7.1 3.3 6.2 2.9 1.9 – 4.5
11.8 – 118.3 32.3 118.3 38.4 19.0 – 78.0
37.7 – 229 87.1 204.4 94.8 65.9 – 136.0
41.7 – 108.0 68.0 80.4 63.8 55.0 – 74.1
16.4 – 299.1 119.6 205.9 113.0 75.3 – 168.0
Øweek)
weight
Øweek)
surface area
GMsgeometric mean. CIs95%-confidence interval.
M. Wilhelm et al. / The Science of the Total Environment 285 (2002) 11–19
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different groups is summarized in Table 5. The geometric mean and maximum values for the different groups ranged between 24.3–55.7 and 62.7–120.7% of the PTWI, respectively. The geometric mean and median percentage of PTWI for the four groups declined in the following order: children Ruhr district)adults Ruhr district)children Amrum)small children Ruhr district. Testing individual correlations for each group, we found no correlation between the dietary intake of cadmium and the age of the participants. 4. Discussion Fig. 1. Comparison of dietary cadmium intake wmgy(kgbwØd)x of the four study groups from Germany. Boxplots: (A) small children, (B) children and (D) adults from the industrialized Ruhr district and (C) children living on the North Sea island Amrum.
pared with the other groups, no matter to what anthropometric andyor temporal parameter the intake was related to. Children from the industrialized Ruhr district (group B) had a higher cadmium intake than those from the North Sea island Amrum (group C) wgeometric mean values: 0.49 and 0.35 mgy(kgbwØday), P-0.05x. As shown in Table 4 there was no uniform influence of sex on the cadmium intake. Except for the small children (group A) we found a tendency to higher values for boysymen when compared with girlsywomen. In group C the sex related difference reached the level of significance (P-0.05). The variation of the daily dietary cadmium intake within the study period for each group is shown in Fig. 2. Analysis of variance revealed that cadmium intake was not influenced by the day of sampling. Histograms of the daily dietary cadmium intake are shown in Fig. 3 and compared with the PTWI converted into daily intake. On this basis, we searched for cadmium intake values exceeding the tolerable intake. There were 3 for the small children from the Ruhr district, 10 for the children from the Ruhr district, 1 for the children from the North Sea island and 2 for adults. Comparison of the weekly cadmium intake with the PTWI for the
This study shows, that the German population has a moderate to high dietary cadmium intake, with maximum levels partly exceeding the WHO recommendations (Fig. 3, Table 5). This is especially true for children and adults living in the industrialized Ruhr district. To evaluate the health risks due to the dietary intake of cadmium, the measured data of this study were compared with the provisionable tolerable weekly intake (PTWI) of 7 mgy(kgbwØweek) proposed by the FAOy WHO. Cadmium was last assessed by the JECFA (Joint Expert Committee on Food Additives) during its 41st Meeting in 1993 (WHO, 1993). The Table 4 Comparison of the dietary intake of cadmium (geometric mean and 95%-confidence interval of mean) of male and female participants for the four different groups A – D (details are given in Table 1) Group A mgyd Male
Group B
1.9 9.7 0.1 – 3.7 6.7 – 14.0 Female 2.1 7.0 1.4 – 3.1 4.7 – 10.3 mgy(kg body weightØday) Male 0.15 0.57 0.08 – 2.89 0.40 – 0.81 Female 0.19 0.42 0.12 – 0.30 0.29 – 0.60 mgy(m2 body surface areaØday) Male 3.6 13.7 1.9 – 6.9 9.7 – 19.5 Female 4.2 10.4 2.7 – 6.6 7.2 – 15.0
Group C
Group D
6.8 6.1 – 7.7 4.7 4.0 – 5.4
28.4 23.6 – 34.1 24.6 16.5 – 36.8
0.38 0.34 – 0.43 0.32 0.27 – 0.37
0.37 0.30 – 0.47 0.37 0.24 – 0.58
9.6 8.5 – 10.8 7.5 6.5 – 8.7
14.7 12.1 – 17.9 14.3 9.5 – 21.6
16 M. Wilhelm et al. / The Science of the Total Environment 285 (2002) 11–19 Fig. 2. Variation of the daily cadmium intake wmgy(kgbw Ød)x within the study period for each group. Group (A) small children, (B) children and (D) adults from the industrialized Ruhr district and (C) children living on the North Sea island Amrum.
M. Wilhelm et al. / The Science of the Total Environment 285 (2002) 11–19 Fig. 3. Histograms of the daily dietary intake of cadmium wmgy(kgbw Ød)x by the four study groups from Germany in comparison to the FAOyWHO PTWI (Provisional Tolerable Weekly Intake) of 7 mgy(kg bw Øweek) converted into daily intake. (A) small children, (B) children and (D) adults from the industrialized Ruhr district and (C) children living on the North Sea island Amrum. 17
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Table 5 Comparison of the dietary intake of cadmium by the four different groups with the FAOyWHO PTWI (provisional tolerable weekly intake) of 7 mgy(kg bwØweek) Basis
Group A
Group B
Group C
Group D
Geometric mean Median Maximum
24.3% 21.9% 78.3%
55.7% 51.9% 120.7%
37.0% 39.0% 62.7%
41.4% 47.6% 101.6%
Committee retained the provisionable tolerable weekly intake (PTWI) of 7 mgy(kg bwØweek) as expressed by the 33rd JECFA Meeting. However, the JECFA stated that ‘there is only a relatively small safety margin between exposure in the normal diet and exposures that produce deleterious effects’. Thus, health risks due to the dietary cadmium intake for individuals in Germany cannot be excluded. Despite successful programs to lower the levels of environmental contaminants such as cadmium, a reduction in dietary cadmium intake could not be observed. In our previous study conducted on children (age 5–8 years) from the Ruhr district during winter and spring 1988–1989, the geometric mean dietary cadmium intake was 0.30 mgy (kgbwØday) and 8.5 mgy(m2 bsaØd) (Wilhelm et al., 1995b), which appears to even lower than the data obtained in the present study wTable 3, children from the Ruhr district, geometric mean: 0.49 mgy(kgbwØday) and 11.9 mgy(m2 bsaØd)x. Data from the literature on the dietary cadmium intake in various countries show great variation ¨ (summaries in Jarup et al., 1998; Schrey et al., 2000; Van Cauwenbergh et al., 2000). With respect to children, only few data are available (summary in Schrey et al., 2000). The median cadmium dietary intake of all children measured in this study of 0.35 mgy(kgbwØday) is in the range of other studies (Dabeka and McKenzie, 1995; Gunderson, 1995; Brussaard et al., 1996; Arnold et al., 1998). The summary of literature data in Van Cauwenbergh et al. (2000) mainly based upon adults gave a spectrum of cadmium dietary intake between 7 and 56 mgyday, most values ranging between 10–20 mgyday. As a comparison, dietary intake among the Swedish population ranges ¨ between 4–70 mgyday (Jarup et al., 1998). The
dietary cadmium intake of adults measured in this study are in the upper range when compared with other studies. The moderate to high cadmium dietary intake could not be explained by the analysis of the questionnaire or food diary. The place of residence, tobacco smoke in the environment, frequency of consuming foods such as homegrown vegetables or fish did not influence the cadmium intake. Food known to be rich in cadmium was only rarely consumed. No participant consumed offals or fieldmushrooms during the sampling period. Spinach, celery, iceberg lettuce and borecole were eaten on 13 out of 229 days. The intake of cereals was 136 g fresh weight yday (corresponding to 10.4% of the total dietary intake) for children from the Ruhr district, 114 g fresh weight yday (corresponding to 9.6% of total dietary intake) for children from the North Sea island and 219 g fresh weight yday (corresponding to 8.5% of the total dietary intake) for adults. These data correspond well with the estimations, made by Ryan et al. (2001). The portion of potatoes and potato products consumed was low and ranged between 2.8 and 4.0% of the total diet in the different groups. In the small children group, there were two children with a cadmium intake exceeding the PTWI, when converted into daily intake. One child had a high consumption of cocoa containing products, whereas the other had a diet mainly based on whole-meal products. The higher cadmium intake of children and adults from the industrialized Ruhr district are probably due to higher consumption of cereals. In these groups, for every day where a cadmium dietary intake exceeding 1.0 mgy(kgbwØday) was found, the food diary revealed consumption of whole-meal products. Since consumption of home grown products was low, both for children from the Ruhr district and from Amrum, the difference in cadmium intake between industrialized and rural region is probably not due to environmental factors, but to the eating habits with a higher consumption of whole-meal products in participants from the industrialized region. Additionally, the proportional intake of cereals was also higher in the latter group (P0.05). This is of importance since cereal is a major contributor to dietary cadmium intake (Ryan et al., 2001). However, some points raised in the
M. Wilhelm et al. / The Science of the Total Environment 285 (2002) 11–19
discussion cannot be underlined by the German Food Monitoring scheme since all of the mentioned food items could not be monitored (BgVV, ¨ gesundheitlichen VerbraucherBundesinstitut fur ¨ schutz und Veterinarmedizin, BgVV, 1997). Maximal permissible or guide levels for cadmium in 20 food items were mainly exceeded in samples of wheat grain (3.1%) and roasted peanuts (50%). 5. Conclusion In conclusion, with regard to the PTWI of 7 mgy(kgbwØweek), a high dietary intake of cadmium with values (geometric mean for four different groups) between 1.7 and 3.7 was found. Cadmium exposure in the general population needs to be reduced to minimize the risk of adverse health effects, due to cadmium. Acknowledgements The authors wish to thank Dr Evelyn Wins and Dipl.-Biol. Petra Mackrodt for assistance in recruiting volunteers as well as for sampling of duplicate portions. References ¨ Aufnahme von Arnold R, Kibler R, Brunner B. Die alimentare ¨ ausgewahlten Schadstoffen und Nitrat-Ergebnisse einer Duplikatstudie in bayerischen Jugend- und Seniorenheimen. Z Ernahrungswiss 1998;37:328 –335. ¨ gesundheitlichen Verbraucherschutz BgVV (Bundesinstitut fur ¨ und Veterinarmedizin). Lebensmittel-Monitoring 1997. BgVV, Berlin (www.bgvv.de). Brussaard JH, Van Dokkum W, Van der Paauw CG, De Vos RH, De Kort WL, Lowik MR. Dietary intake of food contaminants in The Netherlands (Dutch Nutrition Surveillance System). Food Addit Contam 1996;13:561 –573. Dabeka RW, McKenzie AD. Survey of lead, cadmium fluoride, nickel and cobalt in food composites and estimation of dietary intakes of these elements by Canadians in 1986 – 1988. J AOAC Int 1995;78:897 –909. Gunderson EL. FDA Total Diet Study, July 1986 – April 1991, dietary intakes of pesticides, selected elements and other chemicals. J AOAC Int 1995;78:1353 –1363. ¨ Jarup L (ed), Berglund M, Elinder CG, Nordberg G, Vahter M. Health effects of cadmium exposure — a review of the literature and a risk estimate. Scand J Environ Health 1998;24(suppl 1):152.
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¨ Jorhem L, Slorach S, Engman J, Schoder T, Johansson M. The establishment of certified concentrations of thirteen elements in six simulated diet reference materials. National Food Administration Rapport 4y1995, Uppsala, Sweden. Ryan PB, Scanlon KA, MacIntosh DL. Analysis of dietary intake of selected metals in the NHEXAS-Maryland investigation. Environ Health Perspect 2001;109:121 –128. Schmidt RF, Thews G, editors. Physiologie des Menschen, 24th edition. Berlin: Springer-Verlag, . Schrey P, Wittsiepe J, Mackrodt P, Selenka F. Human fecal PCDDyF-excretion exceeds the dietary intake. Chemosphere 1998;37:1825 –1831. Schrey P, Wittsiepe J, Budde U, Heinzow B, Idel H, Wilhelm M. Dietary intake of lead, cadmium, copper and zinc by children from the North Sea island Amrum. Int J Hyg Environ Health 2000;203:1 –9. Van Cauwenbergh V, Bosscher D, Robberecht H, Deelstr H. Daily dietary cadmium intake in Belgium using duplicate portion sampling. Eur Food Res Technol 2000;212:13 –16. WHO, (World Health Organization), GEMS: Global Environmental Monitoring System, Guidelines for the study of dietary intakes of chemical contaminants, WHO Offset Publication 1985, No. 87. WHO, (World Health Organization). Cadmium — Environmental Aspects. Environmental Health Criteria 135, WHO, Geneva, 1992a. WHO, (World Health Organization). Cadmium, Environmental Health Criteria 134, WHO, Geneva, 1992b. WHO, (World Health Organization) Evaluation of certain food additives and contaminants: forty-first report of the Joint FAOyWHO Expert Committee on Food Additives. WHO Technical Report Series, Geneva, 1993 No. 837. Wilhelm M, Lombeck I, Kouros B, Wuthe J, Ohnesorge FK. Duplicate study on the dietary intake of some metalsy metalloids by German children. Part I: Arsenic and mercury. Zbl Hyg (now: Int J Hyg Environ Health) 1995a; 197: 345– 356 (in German). Wilhelm M, Lombeck I, Kouros B, Wuthe J, Ohnesorge FK. Duplicate study on the dietary intake of some metalsy metalloids by German children. Part II: Aluminium, cadmium and lead. Zbl Hyg (now: Int J Hyg Environ Health) 1995b; 197: 357 – 369 (in German). Wilhelm M, Ohnesorge F-K, Lombeck I, Hafner D. Uptake of aluminium, cadmium, copper, lead and zinc by human scalp hair and elution of the adsorbed metals. J Anal Toxicol 1989;13:17 –21. Wilhelm M, Schrey P, Wittsiepe J, Heinzow B. Dietary intake of persistent organic pollutants (POPs) by German children using duplicate method. Int J Hyg Environ Health 2002; 205: in press. Wittsiepe J, Schrey P, Wilhelm M. Dietary intake of PCDDy F by small children with different food consumption measured by the duplicate method. Chemosphere 2001;43:881 – 887.
Dietary intake of cadmium by children and adults from Germany using duplicate portion sampling ¨ Michael Wilhelma,*, Jurgen Wittsiepea, Petra Schreya, Ursula Buddea, Helga Idelb a
¨ Institute of Hygiene, Social- and Environmental Medicine, Ruhr-University-Bochum, Universitatsstr. 150, 44801 Bochum, Germany b ¨ ¨ ¨ Institute of Hygiene, Heinrich-Heine-University Dusseldorf, Universitatsstr. 1, 40225 Dusseldorf, Germany Received 3 August 2001; accepted 26 November 2001
Abstract The dietary intake of cadmium was studied among children and adults from Germany. The study area comprised the highly industrialized Ruhr district as well as the North Sea island Amrum. A total of 229 duplicate samples were collected from 49 individuals between December 1994 and May 1995. The sampling period for each participant was either 3 or 7 days. Cadmium concentrations in duplicate samples were measured by atomic absorption spectrometry. The daily cadmium intakes (geometric mean) for 4 different groups of individuals distributed as follows: for small children (mean age: 1.8 years) from the Ruhr district 0.17 mgy(kgbw Øday) wrange: 0.02 – 1.62 mgy(kgbwØday)x, for children (mean age: 3.8 years) from the Ruhr district 0.49 mgy(kgbw Øday) wrange: 0.11 – 2.06 mgy(kgbwØday)x, for children (mean age: 3.9 years) living on the North Sea island Amrum 0.35 mgy(kgbwØday) wrange: 0.09 – 1.13 mgy (kgbwØday)x and for adults (mean age: 40.9 years) from the Ruhr district 0.37 mgy(kgbwØday) wrange: 0.05 – 1.32 mg y(kgbwØday)x. Compared to the provisional tolerable weekly intake (PTWI) of 7 mgy(kgbw Øweek) proposed by the WHO the dietary intake of cadmium was rather high. The geometric mean and maximum intake values for the different groups ranged between 24.3 – 55.7% and 62.7 – 120.7 respectively of the PTWI. We therefore conclude, that the cadmium exposure of the population needs to be reduced in order to minimize the risk of adverse health effects related to this metal. 䊚 2002 Elsevier Science B.V. All rights reserved. Keywords: Cadmium; Dietary intake; Duplicate study; Children; Adults; Provisional tolerable weekly intake; PTWI; Germany
1. Introduction Cadmium toxicity is well known and the health effects of cadmium exposure have been reviewed ¨ recently (Jarup et al., 1998). Among these, renal tubular damage appears to be one the critical health * Corresponding author. Fax: q49-234-3214-199. E-mail address: [email protected] (M. Wilhelm).
effects of cadmium exposure in the general population. The International Agency for Research on Cancer concluded in 1993 that there was sufficient evidence to classify cadmium as a human carcinogen. Sources of human and environmental cadmium exposure have been reviewed by the World Health Organization (WHO, 1992a,b). Food is the major source of cadmium exposure in the general non-
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smoking population. Natural and anthropogenic sources such as industrial emissions, applications of fertilizers and sewage sludge from farming have led to the contamination of soils. As a result, an increased cadmium uptake occurs by crops and vegetables grown for human consumption. Additionally, airborne cadmium will contribute to the cadmium content of vegetables and grain. Since cadmium particularly accumulates in liver and kidneys of animals, offal may also be an important source of cadmium in the diet. A recent study from the USA revealed that only pasta, cereal, iceberg lettuce and baked potatoes contributed to almost 50% of the dietary cadmium intake (Ryan et al., 2001). Estimates of health risks due to dietary cadmium intake are periodically carried out and compared to the provisional tolerable weekly intake (PTWI) recommended by the FAOyWHO (WHO, 1993). For this purpose the use of the duplicate method is especially suitable and has been successfully applied by our working group in several studies (Wilhelm et al., 1995a,b; Schrey et al., 1998, 2000; Wittsiepe et al., 2001; Wilhelm et al., 2002). In our study (sampling period 1988–1989) with children living in an industrial area of Germany (Duisburg, North Rhine-Westphalia), we calculated a weekly cadmium intake of 2.1 mgy (kgbwØweek), which corresponded to 30% of the PTWI (Wilhelm et al., 1995b). An even higher cadmium intake of 2.7 mgy(kgbwØweek) was found through duplicate samples collected in 1995 from German children living on a North Sea island (Schrey et al., 2000). Considering the recent cad¨ mium health risks reviewed by Jarup et al. (1998), this low margin between the actual PTWI and the dietary cadmium intake is of actual public health concern. They estimated that at an average cadmium intake of 70 mgyday (corresponding to the present PTWI), 7% of the general adult population would be expected to develop cadmium-induced kidney lesions. Consequently the authors have recommended lowering the current PTWI. In this study, we report the results on cadmium dietary intake from our German duplicate studies, from samples collected in 1994 and 1995. The study groups comprised of children at different ages as well as adults, originating from industrial
areas and from a remote area. Through this grouping, we wanted to find out if there were differences in the cadmium dietary intake between children and adults, between children at different ages as well as between a rural and an industrialized region. 2. Subjects and methods 2.1. Subjects and study design Duplicate portions (ns229) were collected from 49 individuals between December 1994 and May 1995. The study was undertaken in the Ruhr district as well as on the North Sea island Amrum. The Ruhr district is a highly industrialized area of North-Rhine-Westphalia, Germany. The North Sea island Amrum is a remote area of Germany. Participants were children aged between 1.3 and 5.2 years and adults aged between 24 and 64 years, divided into four groups. Details referring to the groups are summarized in Table 1. Results concerning trace element intakes including cadmium intake of children from the North Sea island have been published recently (Schrey et al., 2000) in detail. A short medical check-up revealed no acute or chronic illnesses, except for some infections of the upper respiratory tract. All participants consumed a mixed diet. None of the participants were on a special diet and no participant was vegetarian. The dietary cadmium intakes were measured by the duplicate method, according to the WHOGuidelines (WHO, 1985). Duplicate portions of all consumed food, beverages and snacks were collected in precleaned containers. In addition, the parents of the children and the participating adults kept a food diary in which the kind, art of preparation and amount of the food ingested was entered. All food items and beverages were recorded in household measuring units. Additionally all parents and participating adults completed a questionnaire. The questions addressed items which could potentially influence the dietary cadmium intake, such as kind of industry near the home, exposure to tobacco smoke within their environment, frequency of consuming certain foods (e.g. home grown vegetables), etc.
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Table 1 Summarized data on age, sex, place of residence, number of sampling days, and number of duplicate samples with respect to the four groups participating in the German duplicate studies (sampling period December 1994 to May 1995) Group
Number of participants
Age wyearsx (mean, range)
Number of females (f) and males (m)
Place of residence
Number of sampling days
Number of duplicates
A
7
1.8 1.3 – 3.0
4 f; 3 m
Ruhr district
7
47a
B
14
3.8 1.8 – 5.2
7 f; 7 m
Ruhr district
3
42
C
14
3.9 1.5 – 5.1
7 f; 7 m
Amrum
7
98
D
14
7 f; 7 m
Ruhr district
3
42
a
40.9 24 – 64
2 samples were excluded from the study due to incomplete sampling.
2.2. Analytical procedure The food samples were collected by us each day, weighed, homogenized, lyophilized and frozen at y20 8C. Approximately 500–600 mg of the lyophilisate were weighed in Teflon tubes (high performance microwave digestion, Microwave Laboratory Systems GmbH). After addition of 2 ml HNO3 (p.a., 65%, Merck) and 1 ml H2O2 (p.a., 30%, Merck), the samples were digested with a microwave system (high performance microwave digestion, MLS 1200 mega, Microwave Laboratory Systems GmbH). The temperature-power-program was: 2 min, 200 W; 1 min, 0 W; 2 min, 350 W; 1 min 0 W; 2 min 450 W; 1 min 0 W; 3 min 550 W. The analysis was carried out by atomic absorption spectrometry (Zeeman 3030 with HGA 600, Perkin–Elmer). Analytical conditions are already described in details elsewhere (Wilhelm et al., 1989). The detection limit was 4 mgykgdry weight (500 mg lyophilisate). Cadmium concentrations below the detection limit were only observed in the group of small children (mean age: 1.8 years). Cadmium levels lower than the detection limit was estimated by substituting one-half of the detection limits. The accuracy of the method was confirmed by analyzing reference materials (EQC Sample No. 965 B, National Food Administration, Sweden) and HDP-Reference Material (Laboratory of Food Chemistry, Food Research Institute, Agricultural
Center of Finland). The analyzed values were within the certified reference range. The laboratory participated successfully in an interlaboratory quality control study, organized by the National Food Administration, Sweden. In addition, our lab acted as reference laboratory for the establishment of certified concentrations of heavy metals in diet reference materials (Jorhem et al., 1995). 2.3. Calculation of dietary intake and statistics On the basis of the concentrations measured in the food duplicates the daily dietary intake of cadmium was calculated. The weekly intakes were obtained by adding the seven daily intakes from each individual. In cases where the sampling period was only 3 days, the weekly intake was then calculated. The intake rates were additionally related to the body weight of the participants and to their body surface area. The body surface area was calculated by using the equation of DuBois and DuBois: body surface area wcm2xs71.84 * weight wkgx 0.425 * height wcmx0.725 (Schmidt and Thews, 1990). The statistical calculations were performed with the data software system ‘Statistica’ 5.5 or 6 (StatSoft, Inc., Tulsa, OK, USA). To evaluate statistical significance the ‘Mann–Whitney U-test’ and ANOVA were used. The correlations were done using the Pearson Product–Moment Correlation. To characterize the mean location of the
M. Wilhelm et al. / The Science of the Total Environment 285 (2002) 11–19
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data the geometric mean was preferred since data are log-normally distributed.
Table 3 Daily dietary intake of cadmium for the four different groups A – D (details are given in Table 1)
3. Results Cadmium levels of the food duplicates with a geometric median value of 9.9 mgykgdry weight were low in the small children (group A) (P-0.001 compared with the other groups). Cadmium levels of 13 samples of group A children were below the detection limit. The highest cadmium concentrations of duplicate samples were found in adults (group D) (geometric mean: 62.0 mgykgdry weight P-0.001 compared with the other groups). Cadmium levels of duplicate samples tended to be higher for the children living in the industrialized region (group B), when compared with those from the rural area (group C) (geometric mean values: 29.4 and 22.8 mgykgdry weight. Ps0.09). In Tables 2 and 3 basic statistical data of the weekly (Table 2) and daily (Table 3) dietary intake of cadmium for the four study groups are shown. A comparison of the dietary cadmium intake of the four groups is given in Fig. 1. Cadmium intake was low for the small children (P-0.001) com-
mgyd Range Median 90. P. GMa CI of GMb mgy(kg body Range Median 90. P. GMa CI of GMb mgy(m2 body Range Median 90. P. GMa CI of GMb a b
Group A
Group B
Group C
Group D
0.3 – 14.9 2.4 9.6 2.0 1.4 – 2.8
1.8 – 38.9 7.6 26.5 8.2 6.3 – 10.7
1.6 – 13.9 6.1 10.0 2.0 1.4 – 2.8
3.7 – 67.3 27.6 54.3 26.4 21.4 – 32.7
Øday) 0.02 – 1.62 0.21 0.73 0.17 0.12 – 0.25
0.11 – 2.06 0.44 1.49 0.49 0.38 – 0.63
0.09 – 1.13 0.36 0.62 0.35 0.32 – 0.38
0.05 – 1.32 0.41 0.85 0.37 0.30 – 0.47
2.3 – 26.4 8.9 15.1 8.5 7.7 – 9.3
2.1 – 44.0 15.5 30.5 14.5 11.7 – 18.1
weight
Øday) 0.6 – 34.9 2.7 – 48.8 4.9 10.7 16.6 37.2 3.9 11.9 2.8 – 5.7 9.3 – 15.3
surface area
GMsgeometric mean. CIs95%-confidence interval.
Table 2 Weekly dietary intake of cadmium for the four different groups A – D (details are given in Table 1)
mgyweek Range Median 90. P. GMa CI of GMb mgy(kg body Range Median 90. P. GMa CI of GMb mgy(m2 body Range Median 90. P. GMa CI of GMb a b
Group A
Group B
Group C
Group D
7.4 – 50.4 17.0 50.4 19.5 10.1 – 37.5
23.6 – 177.5 55.6 170.8 65.1 43.8 – 96.7
26.6 – 69.8 45.8 57.2 42.4 35.5 – 50.6
29.4 – 583.2 216.9 336.5 205.0 138.0 – 303.0
0.5 – 5.5 1.5 5.5 1.7 0.8 – 3.4
1.6 – 8.5 3.6 8.2 3.9 2.7 – 5.6
1.7 – 4.4 2.7 3.4 2.6 2.3 – 3.0
0.4 – 7.1 3.3 6.2 2.9 1.9 – 4.5
11.8 – 118.3 32.3 118.3 38.4 19.0 – 78.0
37.7 – 229 87.1 204.4 94.8 65.9 – 136.0
41.7 – 108.0 68.0 80.4 63.8 55.0 – 74.1
16.4 – 299.1 119.6 205.9 113.0 75.3 – 168.0
Øweek)
weight
Øweek)
surface area
GMsgeometric mean. CIs95%-confidence interval.
M. Wilhelm et al. / The Science of the Total Environment 285 (2002) 11–19
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different groups is summarized in Table 5. The geometric mean and maximum values for the different groups ranged between 24.3–55.7 and 62.7–120.7% of the PTWI, respectively. The geometric mean and median percentage of PTWI for the four groups declined in the following order: children Ruhr district)adults Ruhr district)children Amrum)small children Ruhr district. Testing individual correlations for each group, we found no correlation between the dietary intake of cadmium and the age of the participants. 4. Discussion Fig. 1. Comparison of dietary cadmium intake wmgy(kgbwØd)x of the four study groups from Germany. Boxplots: (A) small children, (B) children and (D) adults from the industrialized Ruhr district and (C) children living on the North Sea island Amrum.
pared with the other groups, no matter to what anthropometric andyor temporal parameter the intake was related to. Children from the industrialized Ruhr district (group B) had a higher cadmium intake than those from the North Sea island Amrum (group C) wgeometric mean values: 0.49 and 0.35 mgy(kgbwØday), P-0.05x. As shown in Table 4 there was no uniform influence of sex on the cadmium intake. Except for the small children (group A) we found a tendency to higher values for boysymen when compared with girlsywomen. In group C the sex related difference reached the level of significance (P-0.05). The variation of the daily dietary cadmium intake within the study period for each group is shown in Fig. 2. Analysis of variance revealed that cadmium intake was not influenced by the day of sampling. Histograms of the daily dietary cadmium intake are shown in Fig. 3 and compared with the PTWI converted into daily intake. On this basis, we searched for cadmium intake values exceeding the tolerable intake. There were 3 for the small children from the Ruhr district, 10 for the children from the Ruhr district, 1 for the children from the North Sea island and 2 for adults. Comparison of the weekly cadmium intake with the PTWI for the
This study shows, that the German population has a moderate to high dietary cadmium intake, with maximum levels partly exceeding the WHO recommendations (Fig. 3, Table 5). This is especially true for children and adults living in the industrialized Ruhr district. To evaluate the health risks due to the dietary intake of cadmium, the measured data of this study were compared with the provisionable tolerable weekly intake (PTWI) of 7 mgy(kgbwØweek) proposed by the FAOy WHO. Cadmium was last assessed by the JECFA (Joint Expert Committee on Food Additives) during its 41st Meeting in 1993 (WHO, 1993). The Table 4 Comparison of the dietary intake of cadmium (geometric mean and 95%-confidence interval of mean) of male and female participants for the four different groups A – D (details are given in Table 1) Group A mgyd Male
Group B
1.9 9.7 0.1 – 3.7 6.7 – 14.0 Female 2.1 7.0 1.4 – 3.1 4.7 – 10.3 mgy(kg body weightØday) Male 0.15 0.57 0.08 – 2.89 0.40 – 0.81 Female 0.19 0.42 0.12 – 0.30 0.29 – 0.60 mgy(m2 body surface areaØday) Male 3.6 13.7 1.9 – 6.9 9.7 – 19.5 Female 4.2 10.4 2.7 – 6.6 7.2 – 15.0
Group C
Group D
6.8 6.1 – 7.7 4.7 4.0 – 5.4
28.4 23.6 – 34.1 24.6 16.5 – 36.8
0.38 0.34 – 0.43 0.32 0.27 – 0.37
0.37 0.30 – 0.47 0.37 0.24 – 0.58
9.6 8.5 – 10.8 7.5 6.5 – 8.7
14.7 12.1 – 17.9 14.3 9.5 – 21.6
16 M. Wilhelm et al. / The Science of the Total Environment 285 (2002) 11–19 Fig. 2. Variation of the daily cadmium intake wmgy(kgbw Ød)x within the study period for each group. Group (A) small children, (B) children and (D) adults from the industrialized Ruhr district and (C) children living on the North Sea island Amrum.
M. Wilhelm et al. / The Science of the Total Environment 285 (2002) 11–19 Fig. 3. Histograms of the daily dietary intake of cadmium wmgy(kgbw Ød)x by the four study groups from Germany in comparison to the FAOyWHO PTWI (Provisional Tolerable Weekly Intake) of 7 mgy(kg bw Øweek) converted into daily intake. (A) small children, (B) children and (D) adults from the industrialized Ruhr district and (C) children living on the North Sea island Amrum. 17
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Table 5 Comparison of the dietary intake of cadmium by the four different groups with the FAOyWHO PTWI (provisional tolerable weekly intake) of 7 mgy(kg bwØweek) Basis
Group A
Group B
Group C
Group D
Geometric mean Median Maximum
24.3% 21.9% 78.3%
55.7% 51.9% 120.7%
37.0% 39.0% 62.7%
41.4% 47.6% 101.6%
Committee retained the provisionable tolerable weekly intake (PTWI) of 7 mgy(kg bwØweek) as expressed by the 33rd JECFA Meeting. However, the JECFA stated that ‘there is only a relatively small safety margin between exposure in the normal diet and exposures that produce deleterious effects’. Thus, health risks due to the dietary cadmium intake for individuals in Germany cannot be excluded. Despite successful programs to lower the levels of environmental contaminants such as cadmium, a reduction in dietary cadmium intake could not be observed. In our previous study conducted on children (age 5–8 years) from the Ruhr district during winter and spring 1988–1989, the geometric mean dietary cadmium intake was 0.30 mgy (kgbwØday) and 8.5 mgy(m2 bsaØd) (Wilhelm et al., 1995b), which appears to even lower than the data obtained in the present study wTable 3, children from the Ruhr district, geometric mean: 0.49 mgy(kgbwØday) and 11.9 mgy(m2 bsaØd)x. Data from the literature on the dietary cadmium intake in various countries show great variation ¨ (summaries in Jarup et al., 1998; Schrey et al., 2000; Van Cauwenbergh et al., 2000). With respect to children, only few data are available (summary in Schrey et al., 2000). The median cadmium dietary intake of all children measured in this study of 0.35 mgy(kgbwØday) is in the range of other studies (Dabeka and McKenzie, 1995; Gunderson, 1995; Brussaard et al., 1996; Arnold et al., 1998). The summary of literature data in Van Cauwenbergh et al. (2000) mainly based upon adults gave a spectrum of cadmium dietary intake between 7 and 56 mgyday, most values ranging between 10–20 mgyday. As a comparison, dietary intake among the Swedish population ranges ¨ between 4–70 mgyday (Jarup et al., 1998). The
dietary cadmium intake of adults measured in this study are in the upper range when compared with other studies. The moderate to high cadmium dietary intake could not be explained by the analysis of the questionnaire or food diary. The place of residence, tobacco smoke in the environment, frequency of consuming foods such as homegrown vegetables or fish did not influence the cadmium intake. Food known to be rich in cadmium was only rarely consumed. No participant consumed offals or fieldmushrooms during the sampling period. Spinach, celery, iceberg lettuce and borecole were eaten on 13 out of 229 days. The intake of cereals was 136 g fresh weight yday (corresponding to 10.4% of the total dietary intake) for children from the Ruhr district, 114 g fresh weight yday (corresponding to 9.6% of total dietary intake) for children from the North Sea island and 219 g fresh weight yday (corresponding to 8.5% of the total dietary intake) for adults. These data correspond well with the estimations, made by Ryan et al. (2001). The portion of potatoes and potato products consumed was low and ranged between 2.8 and 4.0% of the total diet in the different groups. In the small children group, there were two children with a cadmium intake exceeding the PTWI, when converted into daily intake. One child had a high consumption of cocoa containing products, whereas the other had a diet mainly based on whole-meal products. The higher cadmium intake of children and adults from the industrialized Ruhr district are probably due to higher consumption of cereals. In these groups, for every day where a cadmium dietary intake exceeding 1.0 mgy(kgbwØday) was found, the food diary revealed consumption of whole-meal products. Since consumption of home grown products was low, both for children from the Ruhr district and from Amrum, the difference in cadmium intake between industrialized and rural region is probably not due to environmental factors, but to the eating habits with a higher consumption of whole-meal products in participants from the industrialized region. Additionally, the proportional intake of cereals was also higher in the latter group (P0.05). This is of importance since cereal is a major contributor to dietary cadmium intake (Ryan et al., 2001). However, some points raised in the
M. Wilhelm et al. / The Science of the Total Environment 285 (2002) 11–19
discussion cannot be underlined by the German Food Monitoring scheme since all of the mentioned food items could not be monitored (BgVV, ¨ gesundheitlichen VerbraucherBundesinstitut fur ¨ schutz und Veterinarmedizin, BgVV, 1997). Maximal permissible or guide levels for cadmium in 20 food items were mainly exceeded in samples of wheat grain (3.1%) and roasted peanuts (50%). 5. Conclusion In conclusion, with regard to the PTWI of 7 mgy(kgbwØweek), a high dietary intake of cadmium with values (geometric mean for four different groups) between 1.7 and 3.7 was found. Cadmium exposure in the general population needs to be reduced to minimize the risk of adverse health effects, due to cadmium. Acknowledgements The authors wish to thank Dr Evelyn Wins and Dipl.-Biol. Petra Mackrodt for assistance in recruiting volunteers as well as for sampling of duplicate portions. References ¨ Aufnahme von Arnold R, Kibler R, Brunner B. Die alimentare ¨ ausgewahlten Schadstoffen und Nitrat-Ergebnisse einer Duplikatstudie in bayerischen Jugend- und Seniorenheimen. Z Ernahrungswiss 1998;37:328 –335. ¨ gesundheitlichen Verbraucherschutz BgVV (Bundesinstitut fur ¨ und Veterinarmedizin). Lebensmittel-Monitoring 1997. BgVV, Berlin (www.bgvv.de). Brussaard JH, Van Dokkum W, Van der Paauw CG, De Vos RH, De Kort WL, Lowik MR. Dietary intake of food contaminants in The Netherlands (Dutch Nutrition Surveillance System). Food Addit Contam 1996;13:561 –573. Dabeka RW, McKenzie AD. Survey of lead, cadmium fluoride, nickel and cobalt in food composites and estimation of dietary intakes of these elements by Canadians in 1986 – 1988. J AOAC Int 1995;78:897 –909. Gunderson EL. FDA Total Diet Study, July 1986 – April 1991, dietary intakes of pesticides, selected elements and other chemicals. J AOAC Int 1995;78:1353 –1363. ¨ Jarup L (ed), Berglund M, Elinder CG, Nordberg G, Vahter M. Health effects of cadmium exposure — a review of the literature and a risk estimate. Scand J Environ Health 1998;24(suppl 1):152.
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¨ Jorhem L, Slorach S, Engman J, Schoder T, Johansson M. The establishment of certified concentrations of thirteen elements in six simulated diet reference materials. National Food Administration Rapport 4y1995, Uppsala, Sweden. Ryan PB, Scanlon KA, MacIntosh DL. Analysis of dietary intake of selected metals in the NHEXAS-Maryland investigation. Environ Health Perspect 2001;109:121 –128. Schmidt RF, Thews G, editors. Physiologie des Menschen, 24th edition. Berlin: Springer-Verlag, . Schrey P, Wittsiepe J, Mackrodt P, Selenka F. Human fecal PCDDyF-excretion exceeds the dietary intake. Chemosphere 1998;37:1825 –1831. Schrey P, Wittsiepe J, Budde U, Heinzow B, Idel H, Wilhelm M. Dietary intake of lead, cadmium, copper and zinc by children from the North Sea island Amrum. Int J Hyg Environ Health 2000;203:1 –9. Van Cauwenbergh V, Bosscher D, Robberecht H, Deelstr H. Daily dietary cadmium intake in Belgium using duplicate portion sampling. Eur Food Res Technol 2000;212:13 –16. WHO, (World Health Organization), GEMS: Global Environmental Monitoring System, Guidelines for the study of dietary intakes of chemical contaminants, WHO Offset Publication 1985, No. 87. WHO, (World Health Organization). Cadmium — Environmental Aspects. Environmental Health Criteria 135, WHO, Geneva, 1992a. WHO, (World Health Organization). Cadmium, Environmental Health Criteria 134, WHO, Geneva, 1992b. WHO, (World Health Organization) Evaluation of certain food additives and contaminants: forty-first report of the Joint FAOyWHO Expert Committee on Food Additives. WHO Technical Report Series, Geneva, 1993 No. 837. Wilhelm M, Lombeck I, Kouros B, Wuthe J, Ohnesorge FK. Duplicate study on the dietary intake of some metalsy metalloids by German children. Part I: Arsenic and mercury. Zbl Hyg (now: Int J Hyg Environ Health) 1995a; 197: 345– 356 (in German). Wilhelm M, Lombeck I, Kouros B, Wuthe J, Ohnesorge FK. Duplicate study on the dietary intake of some metalsy metalloids by German children. Part II: Aluminium, cadmium and lead. Zbl Hyg (now: Int J Hyg Environ Health) 1995b; 197: 357 – 369 (in German). Wilhelm M, Ohnesorge F-K, Lombeck I, Hafner D. Uptake of aluminium, cadmium, copper, lead and zinc by human scalp hair and elution of the adsorbed metals. J Anal Toxicol 1989;13:17 –21. Wilhelm M, Schrey P, Wittsiepe J, Heinzow B. Dietary intake of persistent organic pollutants (POPs) by German children using duplicate method. Int J Hyg Environ Health 2002; 205: in press. Wittsiepe J, Schrey P, Wilhelm M. Dietary intake of PCDDy F by small children with different food consumption measured by the duplicate method. Chemosphere 2001;43:881 – 887.