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cadmium level in food in comparison to result from food duplicate diet method
International Journal of Hygiene and Environmental Health 213 (2010) 450–457
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Dietary intake of lead and cadmium by children and adults – Result calculated from dietary recall and available lead/cadmium level in food in comparison to result from food duplicate diet method Pei Liu a,∗ , Can-Nan Wang b , Xiao-Yun Song b , Yong-Ning Wu c a
Department of Epidemiology and Biostatistics, School of Public Health, Southeast University, DingJiaqiao 87#, Hunan Road, Gulou District, Nanjing 210009, Jiangsu, China Department of Nutrition and Food Hygiene, School of Public Health, Southeast University, Nanjing 210009, China c National Institute for Nutrition and Food Safety, Chinese Center for Diseases Control and Prevention, Beijing 100050, China b
a r t i c l e
i n f o
Article history: Received 28 October 2009 Received in revised form 9 July 2010 Accepted 15 July 2010 Keywords: Lead Cadmium Dietary intake Dietary recall Duplicate diet
a b s t r a c t The dietary intakes of lead and cadmium by 30 children and 30 adults living in Jinhu area in China were determined by the duplicate method with a 3-day sampling period. Dietary recall and available lead/cadmium level in food were also used to calculate dietary intakes. Lead intakes based on duplicate method were 15.66 g (kgbw )−1 week−1 for children and 8.83 g (kgbw )−1 week−1 for adults. Cadmium intakes were 2.07 g (kgbw )−1 week−1 for children and 1.49 g (kgbw )−1 week−1 for adult. The results from the dietary record method were as follows: lead intakes were 11.84 g (kgbw )−1 week−1 for children and 7.70 g (kgbw )−1 week−1 for adult. Cadmium intakes were 2.20 g (kgbw )−1 week−1 for children and 1.44 g (kgbw )−1 week−1 for adults. Children’s dietary intakes were higher than those of adults’. The results of the dietary intakes calculated from two methods did not have significant difference. Compared to the FAO/WHO PTWIs for lead and cadmium, the average lead and cadmium dietary intakes are all below PTWIs. It was concluded that dietary record method can give comparatively accurate result for lead and cadmium dietary intakes compared with duplicate method. The average lead and cadmium dietary intakes for children and adults in Jinhu area are considered safe. However, the high level of dietary lead and cadmium intakes of children in this area deserves our attention. © 2010 Elsevier GmbH. All rights reserved.
Introduction Lead is one of the environmental contaminants with clearly identified human health hazards. Human exposure to lead and the subsequent health effects have been summarized in several reviews (WHO, 1985a,b; Chen et al., 2007; Rubio et al., 2005). Children is more sensitive to lead exposure, since many studies have shown that even low levels of lead exposure could lead to irreversible intelligence deficits, impaired neurobehavioral development, and physical growth problems to children during their developing stage (Shen et al., 2001). The main exposure path of non-occupationally exposed individuals is by consumption of food. Cadmium is also a heavy metal toxic to humans and the health effects of cadmium exposure have been reviewed recently (Järup et al., 1998). The International Agency for Research on Cancer has classified cadmium as a human carcinogen in 1993. Food is also the major source of cadmium exposure in the general non-smoking population.
∗ Corresponding author. Tel.: +86 25 83272584; fax: +86 25 83351411. E-mail addresses: [email protected], [email protected] (P. Liu). 1438-4639/$ – see front matter © 2010 Elsevier GmbH. All rights reserved. doi:10.1016/j.ijheh.2010.07.002
In light of the high prevalence of lead/cadmium exposure and the significance of the health effects related to exposure, it is essential to carry out dietary exposure assessment for human lead/cadmium. Duplicate study and intake assessment from dietary recall and contamination data are both methods used in dietary exposure assessment and each method has been applied by many researchers. However, using both methods in one study is not commonly seen, although some researchers have applied both methods in one study (Wittsiepe et al., 2009; Hilbiga et al., 2004) and the comparison is considered meaningful to demonstrate the use of the dietary record method for the determination of dietary intake, but it depend on the study design and the element, and it is not known if the assessment of dietary records is suitable to estimate lead or cadmium intake. In this study, we reviewed samples and questionnaires from our former duplicate study which were carried out in 2007 (Wang et al., 2009) to calculated dietary lead/cadmium intake for children and adults in Jinhu area of China. At the same time, we calculated dietary lead/cadmium intake from the 3-day 24-h dietary recall of duplicate study mentioned above and available lead/cadmium concentration data from the national food contamination monitoring system (2001–2006) in Jiangsu province (we call it the dietary
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Table 1 General data of the participants. Group
Gender
Number of participants
Number of diet records
Number of duplicates
Child
Boy Girl
18 12
52 36
52 36
4.1 ± 1.3 4.4 ± 1.5
Adult
Man Woman
17 13
49 39
49 39
40.9 ± 12.7 45.6 ± 14.1
record method in this study) so as to know whether the assessment from dietary record is suitable to estimate lead/cadmium intake. In order to evaluate the health risk due to dietary lead/cadmium intake, we compared our results with the provisional tolerable weekly intakes (PTWI) for lead and cadmium proposed by the WHO separately. Finally, in view of the wide usage of duplicate method in dietary intake assessment and the recognition of the accuracy of the effective intake of contaminants provided by this method, we compared our duplicate result with similar studies performed in other countries. Materials and methods Subjects and study design of duplicate study The general study design and analytical procedure of our duplicate study performed in 2007 has been described in detail previously (Wang et al., 2009). In brief: This study included 30 children (18 boys and 12 girls) aged between 1.9 and 7.0 years and 30 adults (17 men and 13 women) aged between 24.7 and 65.8 years. General data of the participants are summarized in Table 1. Our sampling period included 3 consecutive days, 2 weekdays and 1 weekend (excluding any special days and festival). All of the subjects, except 4 people whose sampling period was only 2 due to their absence, finished the 3-day sampling. A total of 176 duplicate diet samples, including the snacks, beverages and drinking water were collected from 60 subjects in November and December 2007 following the WHO guidelines (WHO, 1985a,b) from Jinhu area of China, a countryside in the southeastern part of China, with farming as its main industry. All subjects consumed a standard diet. None of them was on a special diet or was vegetarian. After each sampling day, 24-h dietary recall was done to keep a record of the type and amount of everything a subject eat during the whole day. All subjects’ weight was measured by the interviewer at the end of our sampling period. Analytical procedure of duplicate samples The food samples were collected each day, weighed, homogenized and frozen at −20 ◦ C. The analysis was carried out by Graphite Furnace Atomic Absorption Spectrometry (GF-AAS) according to national standard GB/T5009.12-2003 and GB/T5009.15-2003. The detail analytical conditions are described in our previous study (Wang et al., 2009). The method was confirmed by analyzing reference materials of Poplar Leaves (approved by General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China. GBW07604). The recoveries were 94–108.5% for lead and 92–110.5% for cadmium. The relative standard deviations (n = 8) were 1.34–7.38% for lead and 2.75–7.03% for cadmium. Calculation of dietary intake from duplicate study and statistics The dietary intake per subject related to body weight was calculated on the basis of the measured concentration of lead and cadmium and the amount of food eaten in the food duplicates. The
Age
Height
Weight
103.9 ± 9.9 105.3 ± 10.5
19.0 ± 3.6 18.7 ± 4.7
167.5 ± 5.3 159.1 ± 6.0
71.7 ± 12.5 57.7 ± 9.7
equation used in duplicate study is as follows:
yij =
cij
p
x k=1 ijk
bwi
× 1000
(1)
where yij : dietary lead/cadmium intake by consumer i in day j per kg of body weight (in g (kgbw )−1 day−1 ); xijk : consumption by consumer i of food k in day j (in kg); cij : concentration of lead/cadmium in the duplicate diet eaten by consumer i in day j (in mg kg−1 ); bwi : body weight of consumer i (in kg). Finally, p: number of foods consumed by consumer i in day j. The weekly dietary lead/cadmium intake by consumer i was calculated as follows: sum of the 3 daily intakes × 7/3 (in g (kgbw )−1 week−1 ) or sum of the 2 daily intakes × 7/2 (in g (kgbw )−1 week−1 ). Groups (child and adult) were compared by Wilcoxon rank sum test. All statistical calculations were made using the statistical software SAS 9.1 (SAS institute Inc., Cary, NC, USA).
Data analysis of dietary recall and available lead/cadmium level Food consumption data collected from 24-h dietary recall in our duplicate study together with available lead/cadmium concentrations of foodstuffs from the national food contamination monitoring system (2001–2006) in Jiangsu province were used for lead/cadmium intake calculation. Data concerning food consumption from 24-h dietary recall are described in Table 2 and lead/cadmium concentrations are described in Table 3 in detail. Before calculation, individually reported food items in the 24-h dietary recall and detected food items in the lead/cadmium concentration data were identified and classified according to food classification system in China Food Composition 2002 (Yang et al., 2002). Each recorded food item was given a food code which was used to match the consumption data with the lead/cadmium concentration data. The daily intake was calculated by multiplying the consumption amount of each individually reported food item with corresponding median lead/cadmium concentration and added up to give the estimated total daily lead/cadmium intake. The equation was given below:
p yij =
x c k=1 ijk k bwi
× 1000
(2)
where yij : the dietary lead/cadmium intake by consumer i in day j per kg of body weight (in g (kgbw )−1 day−1 ); xijk : the consumption by consumer i of food k in day j (in kg); ck : the median concentration of lead/cadmium in food k (in mg kg−1 ); bwi : body weight of consumer i (in kg); Finally, p: number of foods consumed by consumer i in day j. The weekly dietary lead/cadmium intake by consumer i was calculated as follows: sum of the 3 daily intakes × 7/3 (in g (kgbw )−1 week−1 ) or sum of the 2 daily intakes × 7/2 (in g (kgbw )−1 week−1 ). The calculations were done with statistical software SAS 9.1 (SAS institute Inc., Cary, NC, USA).
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Table 2 Food consumption from 24-h dietary recall. Food type
Food group
Adult
Child
N
Consumption (mean, g)
N
Consumption (mean, g)
142 88 4 18 3 21 8
721.1 647.4 4.8 20.8 1.3 42.0 4.9
192 86 7 29 3 26 41
300.5 230.9 2.7 21.9 0.6 22.7 21.8
Potato Sweet potato Taro Starch
29 2 16 1 10
44.6 0.8 26.9 0.7 16.2
31 7 14 2 8
22.6 1.9 13.8 0.5 6.4
Horse bean Red bean Soybean Green bean Bean products Cowpea
61 1 3 5 4 47 1
64.8 0.1 1.0 4.0 1.1 58.6 0.1
51 1 4 2 4 40 –
23.0 0.1 0.5 1.6 0.2 20.6 –
205 12 78 54 7 12 2
287.9 13.9 157.5 65.0 5.5 9.0 2.3
159 5 63 44 9 7 2
78.9 1.4 42.4 20.5 2.7 2.7 0.4
30 10
31.8 2.9
18 11
7.8 1.1
Mushroom Auricularia
15 13 2
13.5 11.0 0.7
13 8 5
3.5 2.8 0.6
Citrus fruits Assorted tropical and sub-tropical fruits Pome fruits Stone fruits Berries
16 4 2 10 – –
16.8 3.1 1.3 12.4 – –
74 27 16 27 1 3
71.1 22.7 15.2 30.6 0.1 2.5
8 6 2
2.9 2.1 0.8
15 10 5
2.7 2.4 0.4
71 43 1 18 4 6 4
74.4 43.9 1.1 17.6 3.4 7.6 0.9
70 33 1 15 10 7 4
44.2 20.7 0.8 9.3 6.5 5.5 1.4
1 1 – – –
1.7 1.7 – – –
34 26 4 3 1
72.5 57.6 14.4 2.6 0.1
Eggs
40 40
22.9 22.9
52 52
27.8 27.8
Fish Shrimp Kelp
39 37 1 1
37.8 37.8 0.1 1.7
26 23 2 1
8.9 8.5 0.4 0.1
9 2 7 –
36.0 5.1 30.9 –
24 23 – 1
61.3 56.2 – 2.8
Cereals Rice Wheat Wheat products Corn Noodles Cakes Tubers
Legumes and products
Vegetables Legume vegetables Leafy vegetable Root and tuber vegetables Fruiting vegetables, cucurbits Fruiting vegetables, other than cucurbits Brassica (cole or cabbage) vegetables, head cabbages, flowerhead cabbages Bulb vegetables Salted vegetables Fungi
Fruits
Nuts and seeds Nuts Seeds Meat Pork Goose Chicken Beef Duck Meat products Milk Milk Yoghurt Milk powder Milk tablet Eggs Sea food
Beverages Milk beverage Alcohol Non-carbonate soft-drink Note: N, number of dietary record of food type or food group.
P. Liu et al. / International Journal of Hygiene and Environmental Health 213 (2010) 450–457
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Table 3 Lead/cadmium concentrations of each food type/food group. Food type
Food group
Cereals Rice Wheat Wheat products Millet Rice flour products Noodle Cakes Corn Tubers Potato Sweat potato Taro Legumes and products Beans Bean products Vegetables Root and tuber vegetables Fruiting vegetables, other than cucurbits Fruiting vegetables, cucurbits Stalk and stem vegetables Bulb vegetables Aquatic root vegetables Leafy vegetable Brassica (cole or cabbage) vegetables, head cabbages, flowerhead cabbages Legume vegetables Wild vegetable Salted vegetables Fungi Mushroom Fruits Citrus fruits Stone fruits Berries Assorted tropical and sub-tropical fruits-inedible peel Assorted tropical and sub-tropical fruits-edible peel Pome fruits Canned fruits
Lead
Cadmium
N
Concentration (median, mg kg−1 )
N
Concentration (median, mg kg−1 )
387 205 115 10 3 1 18 6 29
0.068 0.086 0.056 0.005 0.065 0.005 0.071 0.058 0.005
358 172 118 10 4 1 18 6 29
0.012 0.013 0.016 0.000 0.013 0.000 0.007 0.005 0.005
22 10 12 –
0.098 0.051 0.012 –
22 9 12 1
0.010 0.015 0.005 0.162
191 168 23
0.018 0.019 0.005
223 204 19
0.002 0.002 –
372 26 38 70 4 21 2 98 13
0.036 0.064 0.038 0.046 0.041 0.025 0.085 0.031 0.031
305 23 37 70 4 22 2 112 15
0.005 0.004 0.006 0.003 0.002 0.005 0.004 0.013 0.002
89 2 9
0.005 0.131 0.005
10 2 9
0.003 0.007 0.003
84 84
0.027 0.027
79 79
0.022 0.022
183 40 32 15 9
0.034 0.044 0.019 0.041 0.027
179 40 32 14 7
0.001 0.001 0.002 0.002 0.003
3
0.001
3
0.13
79 –
0.033 –
76 5
0.001 0.001
8 5 3
0.023 0.064 0.012
8 5 3
0.047 0.050 0.045
Meat products Chicken Edible offal (mammalian) Beef Duck Mutton Pork
432 23 36 171 24 1 36 141
0.063 0.079 0.081 0.070 0.095 0.059 0.013 0.046
423 23 35 167 23 – 36 139
0.008 0.004 0.004 0.370 0.001 – 0.001 0.002
Milk Milk powder Yogurt
193 149 7 37
0.018 0.020 0.056 0.005
136 92 7 37
0.007 0.000 0.007 0.001
Eggs Egg products
211 51 160
0.104 0.046 0.199
124 13 111
0.002 0.002 0.002
Freshwater fish Marine fish Crustaceans Marine invertebrate
614 97 174 160 183
0.037 0.034 0.027 0.045 0.070
598 95 160 158 181
0.014 0.002 0.007 0.017 0.103
86
0.013
72
0.001
Nuts and seeds Nuts Seeds Meat
Milk
Eggs
Sea food
Beverages Note: N, number of dietary record of food type or food group.
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Table 4 Lead intakes calculated from duplicate study and from dietary recall and available lead concentration data. Lead intake
x¯ ± s
N
P50
P75
P90
P97.5
MAX
P-values c/aa
Daily lead intake (g (kgbw )−1 day−1 ) Dietary record Child 88 1.92 Adult 88 1.16 Duplicate diet Child 88 2.18 Adult 88 1.46
± 1.13 ± 0.45
1.74 1.12
2.27 1.42
2.93 1.87
5.59 2.06
7.04 2.67
Z = −6.022 P<0.0001
± 1.68 ± 1.28
1.65 1.10
2.94 1.80
4.53 2.96
6.86 5.27
7.43 7.57
Z = −3.37 P = 0.0007
9.03 3.70
11.84 7.70
17.02 9.98
19.74 12.01
45.18 23.37
45.18 23.37
Z = −3.65 P = 0.0003
5.02 4.90
15.66 8.83
19.00 13.06
21.01 18.55
24.31 21.65
24.31 21.65
Z = 3.526 P = 0.0004
Weekly lead intake (g (kgbw )−1 week−1 ) Dietary record Child 30 14.19 ± Adult 30 8.71 ± Duplicate diet Child 30 15.18 ± Adult 30 10.13 ±
d/rb For child S = 137 P = 0.5716 For adult S = 181 P = 0.4545 For child S = 82.5 P = 0.0899 For adult S = 57.5 P = 0.2434
Notes: N, number of samples; P, percentile; MAX, maximum. Z, statistic of Wilcoxon rank sum test; S, statistic of Wilcoxon sighed rank test. a Comparison of intakes between child and adult. b Comparison of results between duplicate study and dietary record method for children (For child) and for adults (For adult).
Comparison of results from duplicate diet method with data calculated from dietary record method Wilcoxon signed rank test was applied to compare results of two methods following a matched pair design. All statistical calculations were made using the statistical data analysis software SAS 9.1 (SAS institute Inc., Cary, NC, USA). Results Descriptive statistical data according to study groups on calculated dietary lead and cadmium intakes based on food duplicate method and dietary record method are given in Tables 4 and 5. For lead intakes, result of duplicate method showed that the median daily intakes were 1.65 g (kgbw )−1 day−1 for children and 1.10 g (kgbw )−1 day−1 for adults (P = 0.0007), while the median weekly lead intake were 15.66 g (kgbw )−1 week−1 for children and 8.83 g (kgbw )−1 week−1 for adults (P = 0.0004). Both the daily and weekly lead intakes for children were higher than those of adults (Table 4). The same observation – significantly higher lead intakes for children – was found for the result based on dietary record method (Table 4). The
median daily lead intake was 1.74 g (kgbw )−1 day−1 for children and 1.12 g (kgbw )−1 day−1 for adults (P < 0.0001). The median weekly lead intake was 11.84 g (kgbw )−1 week−1 for children and 7.70 g (kgbw )−1 week−1 for adults (P = 0.0003). With regard to cadmium, daily and weekly cadmium intakes based on duplicate method are given in Table 5. The median daily cadmium intake was 0.32 g (kgbw )−1 day−1 for children and 0.16 g (kgbw )−1 day−1 for adults (P = 0.0016). Median weekly cadmium intake was 2.07 g (kgbw )−1 week−1 for children and 1.49 g (kgbw )−1 week−1 for adults (P = 0.0242). Children have higher daily and weekly intakes than adults (Table 5). Result of dietary record method showed that median daily cadmium intake was 0.23 g (kgbw )−1 day−1 for children and 0.18 g (kgbw )−1 day−1 for adults (P = 0.0002). Median weekly cadmium intake was 2.20 g (kgbw )−1 week−1 for children and 1.44 g (kgbw )−1 week−1 for adults (P = 0.0058). Results of comparison of two methods showed that there were no significant difference between result calculated from duplicate method and dietary record method with respect to daily and weekly dietary lead and cadmium intakes for both children and adults (Tables 4 and 5).
Table 5 Cadmium intakes calculated from duplicate study and from dietary recall and available cadmium concentration data. Cadmium intake
N
x¯ ± s
P50
P75
P90
P97.5
MAX
P-values c/aa
Daily lead intake (g (kgbw )−1 day−1 ) Dietary record Child 88 Adult 88 Duplicate diet Child 88 Adult 88
0.38 ± 0.35 0.21 ± 0.13
0.23 0.18
0.48 0.25
0.95 0.31
1.39 0.58
1.65 0.86
Z = −3.7415 P = 0.0002
0.22 ± 0.47 0.26 ± 0.39
0.32 0.16
0.45 0.33
0.64 0.59
1.19 1.20
3.90 2.90
Z = −3.1556, P = 0.0016
± 1.98 ± 0.65
2.20 1.44
3.08 1.91
6.26 2.48
7.75 3.47
7.75 3.47
Z = −2.7573, P = 0.0058
± 2.08 ± 1.66
2.07 1.49
2.70 2.84
4.31 4.11
9.73 6.82
9.73 6.82
Z = −2.2546 P = 0.0242
Weekly lead intake (g (kgbw )−1 week−1 ) Dietary record Child 30 2.72 Adult 30 1.53 Duplicate diet Child 30 1.49 Adult 30 1.81
Notes: N, number of samples; P, percentile; MAX, maximum. Z, statistic of Wilcoxon rank sum test; S, statistic of Wilcoxon sighed rank test. a Comparison of intakes between child and adult. b Comparison of results between duplicate study and dietary record method for children (For child) and for adults (For adult).
d/rb For child S = −73 P = 0.7632 For adult S = 17 P = 0.9441 For child S = 7.5 P = 0.8805 For adult S = 19.5 P = 0.6954
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Table 6 Comparison of the dietary lead/cadmium intakes by children and adults of duplicate method and dietary record method with the FAO/WHO PTWI. Element Lead
Cadmium
P50 (%)
P75 (%)
P90 (%) −1
−1
Comparison of the weekly lead intake from dietary record method with PTWI [25 g (kgbw ) week Child 47.36 68.08 78.96 Adult 30.80 39.92 48.04 Comparison of the weekly lead intake from duplicate method with PTWI [25 g (kgbw )−1 week−1 ] Child 62.64 76.00 84.00 Adult 35.32 52.24 74.20
P97.5 (%)
MAX (%)
180.72 93.48
180.72 93.48
97.24 86.60
97.24 86.60
]
Comparison of the weekly cadmium intake from dietary record method with PTWI [7 g (kgbw )−1 week−1 ] Child 31.42 44.00 89.43 110.71 Adult 20.57 27.29 35.43 49.57 Comparison of the weekly cadmium intake from duplicate method with PTWI [7 g (kgbw )−1 week−1 ] Child 29.57 38.57 61.57 139.00 Adult 21.29 40.57 58.71 97.43
110.71 49.57 139.00 97.43
Notes: P, percentile; MAX, maximum.
Fig. 1. The cumulative distribution curves for dietary weekly lead intake of duplicate method and dietary record method.
Comparisons of lead and cadmium weekly intakes calculated from both methods with the FAO/WHO PTWIs for lead and cadmium are shown in Table 6. As for lead, median weekly lead intakes for children and adults based on duplicate method accounted for 62.6% and 35.3% of PTWI (25 g (kgbw )−1 week−1 ). No lead intakes exceeded PTWI. Median weekly lead intakes for children and adults calculated from dietary record method accounted for 47.4% and 30.8% of PTWI (25 g (kgbw )−1 week−1 ). No adults’ intake based on dietary record method exceeded PTWI, however Fig. 1 shows that P95 of children’s intake have already exceeded PTWI. As for cadmium, results of duplicate method showed that median weekly cadmium intakes for children and adults accounted for 29.6% and 21.3% of PTWI (7 g (kgbw )−1 week−1 ). No adults’ cadmium intake exceeded PTWI, however, for children’s intake, there was a sharp increase of weekly cadmium intake from P90 (4.31 g (kgbw )−1 week−1 ) to P97.5 (9.73 g (kgbw )−1 week−1 ) (Fig. 2), which reached 139.0% of PTWI (7 g (kgbw )−1 week−1 ). Median weekly cadmium intakes for children and adults from dietary record method accounted for 31.4% and 20.6% of PTWI. The maximum of children’s weekly cadmium reached 110.7% of PTWI, while for adults it was only 49.6%. Discussion In general, several successful tools are suitable for estimation of dietary intakes of substances. These include duplicate diet method (Thomas et al., 1997; Kroes et al., 2002) and evaluation from dietary records (Rockett et al., 2003). Each of these methods has their own advantages and disadvantages in expense, reliability and practicality (Wittsiepe et al., 2009). It is generally believed that duplicate diet method provides the most accurate data concerning the effective amount of contaminants ingested during a standard meal (Leblanc
Fig. 2. The cumulative distribution curves for dietary weekly cadmium intake of duplicate method and dietary record method.
et al., 2000). It is often used to evaluate the accuracy of other methods. However, a duplicate study cost a lot in expense and human resource. Comparatively, dietary intake calculation from available food consumption and concentration data seems a good alternative, but the reliability and accuracy of this method needs validation. In our study, we calculated the dietary intake of lead and cadmium for children and adults from our former duplicate diet study carried out in Jinhu area in 2007. At the same time, we calculated dietary lead and cadmium intake from dietary recall and available lead/cadmium concentration data from the national food contamination monitoring system (2001–2006) in Jiangsu province. The result of the latter was validated by that of duplicate method. Comparison of two methods showed that in our study, results from dietary record method have no significant difference compared with that of duplicate diet method. It can be concluded that dietary lead and cadmium intakes for children and adult in Jinhu area can be correctly evaluated by combining dietary recall data and available contamination data. In order to evaluate the risks due to dietary intake of lead and cadmium, we compared our results with the PTWIs of lead and cadmium recommended by WHO/FAO. The result showed that the average dietary lead and cadmium intakes for children and adults in Jinhu area can be regarded as safe. As previously mentioned, the duplicate and dietary record methods have their own general method specific characteristics. However, the duplicate method is considered to provide the most accurate data concerning the effective amount of contaminants. Compared with dietary lead intakes from other duplicate studies summarized in Table 7, our results are higher. Wilhelm et al. (2003) carried out a 3–7-day duplicate study among 35 children aged between 1 and 5 years from Ger-
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Table 7 Comparison of lead and cadmium intakes with literature data. Country
Study type
Year
Age (years)
Dietary lead intake
Lead China
Duplicate study
2007
Germany
Duplicate study
1995
Germany Germany Australia
Duplicate study Duplicate study Duplicate study
1995 1998 –
Japan Japan
Duplicate study Duplicate study
2000 2000
This study This study Wilhelm et al. (2003) Wilhelm et al. (2003) Schrey et al. (2003) Wilhelm et al. (2005) Gulson et al. (2001) Gulson et al. (2001) Aung et al. (2004) Aung et al. (2006)
Duplicate study
1995
China Poland
Duplicate study Duplicate study
1993–1997 1990–2002
1.10 g/kg day 1.65 g/kg day 0.21–0.68 g/kg day 0.26 g/kg day 0.29 g/kg day 0.75 g/kg day 0.23 g/kg day 0.12 g/kg day 0.25 g/kg day 2g/kg week 0.87 g/kg week 0.26 g/kg day 0.10 g/kg day 0.45 g/kg day 46.4–86.6 g day−1 (F)
Median Median Median Median Median GM AM AM AM AM
America
24.7–65.8 1.9–7.0 1.3–5.2 24.0–64.0 1.5–5.3 1.0–6.0 6.0–11.0 20.0–39.0 (F) 4.2–6.0 3–6 28–40 0–7.0 ≥21.0 – 20.0–55.0
Median Median GM AM
Thomas et al. (1999) Thomas et al. (1999) Zhang et al. (2007) Marzec and Schlegel-Zawadzka (2004)
52.6–105.0 g day−1 (M)
AM
1.10 g/kg day 1.65 g/kg day 0.36 g/kg day 0.21–0.44 g/kg day 0.39 g/kg day 4.92 g/kg week 2.08 g/kg week 16.4–31.4 g day−1 (F)
Median Median Median
AM
21.2–34.5 g day−1 (M)
AM
Cadmium China
Duplicate study
2007
Germany Germany America Japan
Duplicate study Duplicate study Duplicate study Duplicate study
1995 1995 1995 2000
Eastern Poland
Duplicate study
1990–1993, 1998–2002
24.7–65.8 1.9–7.0 1.5–5.3 1.3–5.2 0–7.0 3–6 28–40 20–55
many and found that the median weekly lead intake for children ranged from 1.8 to 4.0 g (kgbw )−1 week−1 , for adults was 2.5 g (kgbw )−1 week−1 , which accounted for 12% and 10% of the PTWI of 25 g (kgbw )−1 week−1 . Another duplicate study carried out by the National Human Exposure Assessment Survey (NHEXAS) (Thomas et al., 1999) found that the median dietary intakes for children aged 0–7 years and adults were 0.26 g (kgbw )−1 day−1 and 0.1 g (kgbw )−1 day−1 which accounted only 7.28% and 2.8% of PTWI. Gulson et al. (2001) did a longitudinal 6-day duplicate diet study for female and children in Australia and found the daily lead intake was 0.12 g (kgbw )−1 day−1 for non-pregnant female and 0.23 g (kgbw )−1 day−1 for migrant children. Additionally, a seven consecutive day of duplicate study of 33 children aged 5 years old in Japan showed the mean lead intake was 0.25 g (kgbw )−1 day−1 (Aung et al., 2004). Our results of 1.65 g (kgbw )−1 day−1 for children and 1.10 g (kgbw )−1 day−1 for adults are higher than those listed above. As for cadmium, the dietary cadmium intake calculated from duplicate study in our study was relatively lower than those from others. Schrey et al. (2003) calculated the cadmium dietary intake of 14 children living in a remote area of Germany using a duplicate method, the median intake of which was 2.7 g (kgbw )−1 week−1 . Another duplicate study carried out by Wilhelm et al. (2002) in Germany showed the range of median weekly cadmium intake for different child groups were 1.5–3.6 g (kgbw )−1 week−1 . Duplicate analysis in Eastern Poland found the cadmium intake in the study varied from 16.4 to 31.4 g day−1 for women and from 21.2 to 34.5 g day−1 for men (Marzec and Schlegel-Zawadzka, 2004). National Human Exposure Assessment Survey (NHEXAS) carried out by EPA (Thomas et al., 1999) found the median of dietary intake for children aged 0–7 years was 0.39 g (kgbw )−1 day−1 . Aung et al. (2004) did a 7-day duplicate study of 25 pairs of children and adults in Japan. The average weekly cadmium intakes for children and
References
Median AM
This study This study Schrey et al. (2003) Wilhelm et al. (2002) Thomas et al. (1999) Aung et al. (2004) Marzec and Schlegel-Zawadzka (2004) Marzec and Schlegel-Zawadzka (2004)
adults were 4.92 g (kgbw )−1 week−1 and 2.08 g (kgbw )−1 week−1 accounted 70% and 26.5% of PTWI respectively, which were higher than those of our study. Conclusion In respect of determination of lead and cadmium intakes for children and adults, data calculated from dietary record method can give reliable data compared to that from duplicate method, at least in Jinhu area. It can be concluded that dietary record method accompanied with strict dietary survey as well as normative concentration monitoring data could also give comparatively accurate result for lead and cadmium dietary exposure instead of food duplicate method which often needs much human and financial resources. On the other hand, result of our study show the average lead and cadmium dietary intakes are all below FAO/WHO PTWI, which can be considered safe. However, a minority of children had their dietary lead/cadmium intake exceeding PTWI, and it deserves our attention. Acknowledgements The study reported here is supported by the National Natural Science Foundation of China (30671763) and the National Science and Technology Support Program (2006BAK02A01). The authors wish to thank all the survey staffs for sampling of duplicate portions, Jinhu CDC for assistance in recruiting volunteers as well as for sample preparation, and the Supervision, Inspection and Testing Center of Agricultural Products Quality and Security of Jiangsu province for the analysis of food samples. We would also like to express our thanks to the editor and anonymous referees for insightful comments on this paper.
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International Journal of Hygiene and Environmental Health journal homepage: www.elsevier.de/ijheh
Dietary intake of lead and cadmium by children and adults – Result calculated from dietary recall and available lead/cadmium level in food in comparison to result from food duplicate diet method Pei Liu a,∗ , Can-Nan Wang b , Xiao-Yun Song b , Yong-Ning Wu c a
Department of Epidemiology and Biostatistics, School of Public Health, Southeast University, DingJiaqiao 87#, Hunan Road, Gulou District, Nanjing 210009, Jiangsu, China Department of Nutrition and Food Hygiene, School of Public Health, Southeast University, Nanjing 210009, China c National Institute for Nutrition and Food Safety, Chinese Center for Diseases Control and Prevention, Beijing 100050, China b
a r t i c l e
i n f o
Article history: Received 28 October 2009 Received in revised form 9 July 2010 Accepted 15 July 2010 Keywords: Lead Cadmium Dietary intake Dietary recall Duplicate diet
a b s t r a c t The dietary intakes of lead and cadmium by 30 children and 30 adults living in Jinhu area in China were determined by the duplicate method with a 3-day sampling period. Dietary recall and available lead/cadmium level in food were also used to calculate dietary intakes. Lead intakes based on duplicate method were 15.66 g (kgbw )−1 week−1 for children and 8.83 g (kgbw )−1 week−1 for adults. Cadmium intakes were 2.07 g (kgbw )−1 week−1 for children and 1.49 g (kgbw )−1 week−1 for adult. The results from the dietary record method were as follows: lead intakes were 11.84 g (kgbw )−1 week−1 for children and 7.70 g (kgbw )−1 week−1 for adult. Cadmium intakes were 2.20 g (kgbw )−1 week−1 for children and 1.44 g (kgbw )−1 week−1 for adults. Children’s dietary intakes were higher than those of adults’. The results of the dietary intakes calculated from two methods did not have significant difference. Compared to the FAO/WHO PTWIs for lead and cadmium, the average lead and cadmium dietary intakes are all below PTWIs. It was concluded that dietary record method can give comparatively accurate result for lead and cadmium dietary intakes compared with duplicate method. The average lead and cadmium dietary intakes for children and adults in Jinhu area are considered safe. However, the high level of dietary lead and cadmium intakes of children in this area deserves our attention. © 2010 Elsevier GmbH. All rights reserved.
Introduction Lead is one of the environmental contaminants with clearly identified human health hazards. Human exposure to lead and the subsequent health effects have been summarized in several reviews (WHO, 1985a,b; Chen et al., 2007; Rubio et al., 2005). Children is more sensitive to lead exposure, since many studies have shown that even low levels of lead exposure could lead to irreversible intelligence deficits, impaired neurobehavioral development, and physical growth problems to children during their developing stage (Shen et al., 2001). The main exposure path of non-occupationally exposed individuals is by consumption of food. Cadmium is also a heavy metal toxic to humans and the health effects of cadmium exposure have been reviewed recently (Järup et al., 1998). The International Agency for Research on Cancer has classified cadmium as a human carcinogen in 1993. Food is also the major source of cadmium exposure in the general non-smoking population.
∗ Corresponding author. Tel.: +86 25 83272584; fax: +86 25 83351411. E-mail addresses: [email protected], [email protected] (P. Liu). 1438-4639/$ – see front matter © 2010 Elsevier GmbH. All rights reserved. doi:10.1016/j.ijheh.2010.07.002
In light of the high prevalence of lead/cadmium exposure and the significance of the health effects related to exposure, it is essential to carry out dietary exposure assessment for human lead/cadmium. Duplicate study and intake assessment from dietary recall and contamination data are both methods used in dietary exposure assessment and each method has been applied by many researchers. However, using both methods in one study is not commonly seen, although some researchers have applied both methods in one study (Wittsiepe et al., 2009; Hilbiga et al., 2004) and the comparison is considered meaningful to demonstrate the use of the dietary record method for the determination of dietary intake, but it depend on the study design and the element, and it is not known if the assessment of dietary records is suitable to estimate lead or cadmium intake. In this study, we reviewed samples and questionnaires from our former duplicate study which were carried out in 2007 (Wang et al., 2009) to calculated dietary lead/cadmium intake for children and adults in Jinhu area of China. At the same time, we calculated dietary lead/cadmium intake from the 3-day 24-h dietary recall of duplicate study mentioned above and available lead/cadmium concentration data from the national food contamination monitoring system (2001–2006) in Jiangsu province (we call it the dietary
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451
Table 1 General data of the participants. Group
Gender
Number of participants
Number of diet records
Number of duplicates
Child
Boy Girl
18 12
52 36
52 36
4.1 ± 1.3 4.4 ± 1.5
Adult
Man Woman
17 13
49 39
49 39
40.9 ± 12.7 45.6 ± 14.1
record method in this study) so as to know whether the assessment from dietary record is suitable to estimate lead/cadmium intake. In order to evaluate the health risk due to dietary lead/cadmium intake, we compared our results with the provisional tolerable weekly intakes (PTWI) for lead and cadmium proposed by the WHO separately. Finally, in view of the wide usage of duplicate method in dietary intake assessment and the recognition of the accuracy of the effective intake of contaminants provided by this method, we compared our duplicate result with similar studies performed in other countries. Materials and methods Subjects and study design of duplicate study The general study design and analytical procedure of our duplicate study performed in 2007 has been described in detail previously (Wang et al., 2009). In brief: This study included 30 children (18 boys and 12 girls) aged between 1.9 and 7.0 years and 30 adults (17 men and 13 women) aged between 24.7 and 65.8 years. General data of the participants are summarized in Table 1. Our sampling period included 3 consecutive days, 2 weekdays and 1 weekend (excluding any special days and festival). All of the subjects, except 4 people whose sampling period was only 2 due to their absence, finished the 3-day sampling. A total of 176 duplicate diet samples, including the snacks, beverages and drinking water were collected from 60 subjects in November and December 2007 following the WHO guidelines (WHO, 1985a,b) from Jinhu area of China, a countryside in the southeastern part of China, with farming as its main industry. All subjects consumed a standard diet. None of them was on a special diet or was vegetarian. After each sampling day, 24-h dietary recall was done to keep a record of the type and amount of everything a subject eat during the whole day. All subjects’ weight was measured by the interviewer at the end of our sampling period. Analytical procedure of duplicate samples The food samples were collected each day, weighed, homogenized and frozen at −20 ◦ C. The analysis was carried out by Graphite Furnace Atomic Absorption Spectrometry (GF-AAS) according to national standard GB/T5009.12-2003 and GB/T5009.15-2003. The detail analytical conditions are described in our previous study (Wang et al., 2009). The method was confirmed by analyzing reference materials of Poplar Leaves (approved by General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China. GBW07604). The recoveries were 94–108.5% for lead and 92–110.5% for cadmium. The relative standard deviations (n = 8) were 1.34–7.38% for lead and 2.75–7.03% for cadmium. Calculation of dietary intake from duplicate study and statistics The dietary intake per subject related to body weight was calculated on the basis of the measured concentration of lead and cadmium and the amount of food eaten in the food duplicates. The
Age
Height
Weight
103.9 ± 9.9 105.3 ± 10.5
19.0 ± 3.6 18.7 ± 4.7
167.5 ± 5.3 159.1 ± 6.0
71.7 ± 12.5 57.7 ± 9.7
equation used in duplicate study is as follows:
yij =
cij
p
x k=1 ijk
bwi
× 1000
(1)
where yij : dietary lead/cadmium intake by consumer i in day j per kg of body weight (in g (kgbw )−1 day−1 ); xijk : consumption by consumer i of food k in day j (in kg); cij : concentration of lead/cadmium in the duplicate diet eaten by consumer i in day j (in mg kg−1 ); bwi : body weight of consumer i (in kg). Finally, p: number of foods consumed by consumer i in day j. The weekly dietary lead/cadmium intake by consumer i was calculated as follows: sum of the 3 daily intakes × 7/3 (in g (kgbw )−1 week−1 ) or sum of the 2 daily intakes × 7/2 (in g (kgbw )−1 week−1 ). Groups (child and adult) were compared by Wilcoxon rank sum test. All statistical calculations were made using the statistical software SAS 9.1 (SAS institute Inc., Cary, NC, USA).
Data analysis of dietary recall and available lead/cadmium level Food consumption data collected from 24-h dietary recall in our duplicate study together with available lead/cadmium concentrations of foodstuffs from the national food contamination monitoring system (2001–2006) in Jiangsu province were used for lead/cadmium intake calculation. Data concerning food consumption from 24-h dietary recall are described in Table 2 and lead/cadmium concentrations are described in Table 3 in detail. Before calculation, individually reported food items in the 24-h dietary recall and detected food items in the lead/cadmium concentration data were identified and classified according to food classification system in China Food Composition 2002 (Yang et al., 2002). Each recorded food item was given a food code which was used to match the consumption data with the lead/cadmium concentration data. The daily intake was calculated by multiplying the consumption amount of each individually reported food item with corresponding median lead/cadmium concentration and added up to give the estimated total daily lead/cadmium intake. The equation was given below:
p yij =
x c k=1 ijk k bwi
× 1000
(2)
where yij : the dietary lead/cadmium intake by consumer i in day j per kg of body weight (in g (kgbw )−1 day−1 ); xijk : the consumption by consumer i of food k in day j (in kg); ck : the median concentration of lead/cadmium in food k (in mg kg−1 ); bwi : body weight of consumer i (in kg); Finally, p: number of foods consumed by consumer i in day j. The weekly dietary lead/cadmium intake by consumer i was calculated as follows: sum of the 3 daily intakes × 7/3 (in g (kgbw )−1 week−1 ) or sum of the 2 daily intakes × 7/2 (in g (kgbw )−1 week−1 ). The calculations were done with statistical software SAS 9.1 (SAS institute Inc., Cary, NC, USA).
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Table 2 Food consumption from 24-h dietary recall. Food type
Food group
Adult
Child
N
Consumption (mean, g)
N
Consumption (mean, g)
142 88 4 18 3 21 8
721.1 647.4 4.8 20.8 1.3 42.0 4.9
192 86 7 29 3 26 41
300.5 230.9 2.7 21.9 0.6 22.7 21.8
Potato Sweet potato Taro Starch
29 2 16 1 10
44.6 0.8 26.9 0.7 16.2
31 7 14 2 8
22.6 1.9 13.8 0.5 6.4
Horse bean Red bean Soybean Green bean Bean products Cowpea
61 1 3 5 4 47 1
64.8 0.1 1.0 4.0 1.1 58.6 0.1
51 1 4 2 4 40 –
23.0 0.1 0.5 1.6 0.2 20.6 –
205 12 78 54 7 12 2
287.9 13.9 157.5 65.0 5.5 9.0 2.3
159 5 63 44 9 7 2
78.9 1.4 42.4 20.5 2.7 2.7 0.4
30 10
31.8 2.9
18 11
7.8 1.1
Mushroom Auricularia
15 13 2
13.5 11.0 0.7
13 8 5
3.5 2.8 0.6
Citrus fruits Assorted tropical and sub-tropical fruits Pome fruits Stone fruits Berries
16 4 2 10 – –
16.8 3.1 1.3 12.4 – –
74 27 16 27 1 3
71.1 22.7 15.2 30.6 0.1 2.5
8 6 2
2.9 2.1 0.8
15 10 5
2.7 2.4 0.4
71 43 1 18 4 6 4
74.4 43.9 1.1 17.6 3.4 7.6 0.9
70 33 1 15 10 7 4
44.2 20.7 0.8 9.3 6.5 5.5 1.4
1 1 – – –
1.7 1.7 – – –
34 26 4 3 1
72.5 57.6 14.4 2.6 0.1
Eggs
40 40
22.9 22.9
52 52
27.8 27.8
Fish Shrimp Kelp
39 37 1 1
37.8 37.8 0.1 1.7
26 23 2 1
8.9 8.5 0.4 0.1
9 2 7 –
36.0 5.1 30.9 –
24 23 – 1
61.3 56.2 – 2.8
Cereals Rice Wheat Wheat products Corn Noodles Cakes Tubers
Legumes and products
Vegetables Legume vegetables Leafy vegetable Root and tuber vegetables Fruiting vegetables, cucurbits Fruiting vegetables, other than cucurbits Brassica (cole or cabbage) vegetables, head cabbages, flowerhead cabbages Bulb vegetables Salted vegetables Fungi
Fruits
Nuts and seeds Nuts Seeds Meat Pork Goose Chicken Beef Duck Meat products Milk Milk Yoghurt Milk powder Milk tablet Eggs Sea food
Beverages Milk beverage Alcohol Non-carbonate soft-drink Note: N, number of dietary record of food type or food group.
P. Liu et al. / International Journal of Hygiene and Environmental Health 213 (2010) 450–457
453
Table 3 Lead/cadmium concentrations of each food type/food group. Food type
Food group
Cereals Rice Wheat Wheat products Millet Rice flour products Noodle Cakes Corn Tubers Potato Sweat potato Taro Legumes and products Beans Bean products Vegetables Root and tuber vegetables Fruiting vegetables, other than cucurbits Fruiting vegetables, cucurbits Stalk and stem vegetables Bulb vegetables Aquatic root vegetables Leafy vegetable Brassica (cole or cabbage) vegetables, head cabbages, flowerhead cabbages Legume vegetables Wild vegetable Salted vegetables Fungi Mushroom Fruits Citrus fruits Stone fruits Berries Assorted tropical and sub-tropical fruits-inedible peel Assorted tropical and sub-tropical fruits-edible peel Pome fruits Canned fruits
Lead
Cadmium
N
Concentration (median, mg kg−1 )
N
Concentration (median, mg kg−1 )
387 205 115 10 3 1 18 6 29
0.068 0.086 0.056 0.005 0.065 0.005 0.071 0.058 0.005
358 172 118 10 4 1 18 6 29
0.012 0.013 0.016 0.000 0.013 0.000 0.007 0.005 0.005
22 10 12 –
0.098 0.051 0.012 –
22 9 12 1
0.010 0.015 0.005 0.162
191 168 23
0.018 0.019 0.005
223 204 19
0.002 0.002 –
372 26 38 70 4 21 2 98 13
0.036 0.064 0.038 0.046 0.041 0.025 0.085 0.031 0.031
305 23 37 70 4 22 2 112 15
0.005 0.004 0.006 0.003 0.002 0.005 0.004 0.013 0.002
89 2 9
0.005 0.131 0.005
10 2 9
0.003 0.007 0.003
84 84
0.027 0.027
79 79
0.022 0.022
183 40 32 15 9
0.034 0.044 0.019 0.041 0.027
179 40 32 14 7
0.001 0.001 0.002 0.002 0.003
3
0.001
3
0.13
79 –
0.033 –
76 5
0.001 0.001
8 5 3
0.023 0.064 0.012
8 5 3
0.047 0.050 0.045
Meat products Chicken Edible offal (mammalian) Beef Duck Mutton Pork
432 23 36 171 24 1 36 141
0.063 0.079 0.081 0.070 0.095 0.059 0.013 0.046
423 23 35 167 23 – 36 139
0.008 0.004 0.004 0.370 0.001 – 0.001 0.002
Milk Milk powder Yogurt
193 149 7 37
0.018 0.020 0.056 0.005
136 92 7 37
0.007 0.000 0.007 0.001
Eggs Egg products
211 51 160
0.104 0.046 0.199
124 13 111
0.002 0.002 0.002
Freshwater fish Marine fish Crustaceans Marine invertebrate
614 97 174 160 183
0.037 0.034 0.027 0.045 0.070
598 95 160 158 181
0.014 0.002 0.007 0.017 0.103
86
0.013
72
0.001
Nuts and seeds Nuts Seeds Meat
Milk
Eggs
Sea food
Beverages Note: N, number of dietary record of food type or food group.
454
P. Liu et al. / International Journal of Hygiene and Environmental Health 213 (2010) 450–457
Table 4 Lead intakes calculated from duplicate study and from dietary recall and available lead concentration data. Lead intake
x¯ ± s
N
P50
P75
P90
P97.5
MAX
P-values c/aa
Daily lead intake (g (kgbw )−1 day−1 ) Dietary record Child 88 1.92 Adult 88 1.16 Duplicate diet Child 88 2.18 Adult 88 1.46
± 1.13 ± 0.45
1.74 1.12
2.27 1.42
2.93 1.87
5.59 2.06
7.04 2.67
Z = −6.022 P<0.0001
± 1.68 ± 1.28
1.65 1.10
2.94 1.80
4.53 2.96
6.86 5.27
7.43 7.57
Z = −3.37 P = 0.0007
9.03 3.70
11.84 7.70
17.02 9.98
19.74 12.01
45.18 23.37
45.18 23.37
Z = −3.65 P = 0.0003
5.02 4.90
15.66 8.83
19.00 13.06
21.01 18.55
24.31 21.65
24.31 21.65
Z = 3.526 P = 0.0004
Weekly lead intake (g (kgbw )−1 week−1 ) Dietary record Child 30 14.19 ± Adult 30 8.71 ± Duplicate diet Child 30 15.18 ± Adult 30 10.13 ±
d/rb For child S = 137 P = 0.5716 For adult S = 181 P = 0.4545 For child S = 82.5 P = 0.0899 For adult S = 57.5 P = 0.2434
Notes: N, number of samples; P, percentile; MAX, maximum. Z, statistic of Wilcoxon rank sum test; S, statistic of Wilcoxon sighed rank test. a Comparison of intakes between child and adult. b Comparison of results between duplicate study and dietary record method for children (For child) and for adults (For adult).
Comparison of results from duplicate diet method with data calculated from dietary record method Wilcoxon signed rank test was applied to compare results of two methods following a matched pair design. All statistical calculations were made using the statistical data analysis software SAS 9.1 (SAS institute Inc., Cary, NC, USA). Results Descriptive statistical data according to study groups on calculated dietary lead and cadmium intakes based on food duplicate method and dietary record method are given in Tables 4 and 5. For lead intakes, result of duplicate method showed that the median daily intakes were 1.65 g (kgbw )−1 day−1 for children and 1.10 g (kgbw )−1 day−1 for adults (P = 0.0007), while the median weekly lead intake were 15.66 g (kgbw )−1 week−1 for children and 8.83 g (kgbw )−1 week−1 for adults (P = 0.0004). Both the daily and weekly lead intakes for children were higher than those of adults (Table 4). The same observation – significantly higher lead intakes for children – was found for the result based on dietary record method (Table 4). The
median daily lead intake was 1.74 g (kgbw )−1 day−1 for children and 1.12 g (kgbw )−1 day−1 for adults (P < 0.0001). The median weekly lead intake was 11.84 g (kgbw )−1 week−1 for children and 7.70 g (kgbw )−1 week−1 for adults (P = 0.0003). With regard to cadmium, daily and weekly cadmium intakes based on duplicate method are given in Table 5. The median daily cadmium intake was 0.32 g (kgbw )−1 day−1 for children and 0.16 g (kgbw )−1 day−1 for adults (P = 0.0016). Median weekly cadmium intake was 2.07 g (kgbw )−1 week−1 for children and 1.49 g (kgbw )−1 week−1 for adults (P = 0.0242). Children have higher daily and weekly intakes than adults (Table 5). Result of dietary record method showed that median daily cadmium intake was 0.23 g (kgbw )−1 day−1 for children and 0.18 g (kgbw )−1 day−1 for adults (P = 0.0002). Median weekly cadmium intake was 2.20 g (kgbw )−1 week−1 for children and 1.44 g (kgbw )−1 week−1 for adults (P = 0.0058). Results of comparison of two methods showed that there were no significant difference between result calculated from duplicate method and dietary record method with respect to daily and weekly dietary lead and cadmium intakes for both children and adults (Tables 4 and 5).
Table 5 Cadmium intakes calculated from duplicate study and from dietary recall and available cadmium concentration data. Cadmium intake
N
x¯ ± s
P50
P75
P90
P97.5
MAX
P-values c/aa
Daily lead intake (g (kgbw )−1 day−1 ) Dietary record Child 88 Adult 88 Duplicate diet Child 88 Adult 88
0.38 ± 0.35 0.21 ± 0.13
0.23 0.18
0.48 0.25
0.95 0.31
1.39 0.58
1.65 0.86
Z = −3.7415 P = 0.0002
0.22 ± 0.47 0.26 ± 0.39
0.32 0.16
0.45 0.33
0.64 0.59
1.19 1.20
3.90 2.90
Z = −3.1556, P = 0.0016
± 1.98 ± 0.65
2.20 1.44
3.08 1.91
6.26 2.48
7.75 3.47
7.75 3.47
Z = −2.7573, P = 0.0058
± 2.08 ± 1.66
2.07 1.49
2.70 2.84
4.31 4.11
9.73 6.82
9.73 6.82
Z = −2.2546 P = 0.0242
Weekly lead intake (g (kgbw )−1 week−1 ) Dietary record Child 30 2.72 Adult 30 1.53 Duplicate diet Child 30 1.49 Adult 30 1.81
Notes: N, number of samples; P, percentile; MAX, maximum. Z, statistic of Wilcoxon rank sum test; S, statistic of Wilcoxon sighed rank test. a Comparison of intakes between child and adult. b Comparison of results between duplicate study and dietary record method for children (For child) and for adults (For adult).
d/rb For child S = −73 P = 0.7632 For adult S = 17 P = 0.9441 For child S = 7.5 P = 0.8805 For adult S = 19.5 P = 0.6954
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Table 6 Comparison of the dietary lead/cadmium intakes by children and adults of duplicate method and dietary record method with the FAO/WHO PTWI. Element Lead
Cadmium
P50 (%)
P75 (%)
P90 (%) −1
−1
Comparison of the weekly lead intake from dietary record method with PTWI [25 g (kgbw ) week Child 47.36 68.08 78.96 Adult 30.80 39.92 48.04 Comparison of the weekly lead intake from duplicate method with PTWI [25 g (kgbw )−1 week−1 ] Child 62.64 76.00 84.00 Adult 35.32 52.24 74.20
P97.5 (%)
MAX (%)
180.72 93.48
180.72 93.48
97.24 86.60
97.24 86.60
]
Comparison of the weekly cadmium intake from dietary record method with PTWI [7 g (kgbw )−1 week−1 ] Child 31.42 44.00 89.43 110.71 Adult 20.57 27.29 35.43 49.57 Comparison of the weekly cadmium intake from duplicate method with PTWI [7 g (kgbw )−1 week−1 ] Child 29.57 38.57 61.57 139.00 Adult 21.29 40.57 58.71 97.43
110.71 49.57 139.00 97.43
Notes: P, percentile; MAX, maximum.
Fig. 1. The cumulative distribution curves for dietary weekly lead intake of duplicate method and dietary record method.
Comparisons of lead and cadmium weekly intakes calculated from both methods with the FAO/WHO PTWIs for lead and cadmium are shown in Table 6. As for lead, median weekly lead intakes for children and adults based on duplicate method accounted for 62.6% and 35.3% of PTWI (25 g (kgbw )−1 week−1 ). No lead intakes exceeded PTWI. Median weekly lead intakes for children and adults calculated from dietary record method accounted for 47.4% and 30.8% of PTWI (25 g (kgbw )−1 week−1 ). No adults’ intake based on dietary record method exceeded PTWI, however Fig. 1 shows that P95 of children’s intake have already exceeded PTWI. As for cadmium, results of duplicate method showed that median weekly cadmium intakes for children and adults accounted for 29.6% and 21.3% of PTWI (7 g (kgbw )−1 week−1 ). No adults’ cadmium intake exceeded PTWI, however, for children’s intake, there was a sharp increase of weekly cadmium intake from P90 (4.31 g (kgbw )−1 week−1 ) to P97.5 (9.73 g (kgbw )−1 week−1 ) (Fig. 2), which reached 139.0% of PTWI (7 g (kgbw )−1 week−1 ). Median weekly cadmium intakes for children and adults from dietary record method accounted for 31.4% and 20.6% of PTWI. The maximum of children’s weekly cadmium reached 110.7% of PTWI, while for adults it was only 49.6%. Discussion In general, several successful tools are suitable for estimation of dietary intakes of substances. These include duplicate diet method (Thomas et al., 1997; Kroes et al., 2002) and evaluation from dietary records (Rockett et al., 2003). Each of these methods has their own advantages and disadvantages in expense, reliability and practicality (Wittsiepe et al., 2009). It is generally believed that duplicate diet method provides the most accurate data concerning the effective amount of contaminants ingested during a standard meal (Leblanc
Fig. 2. The cumulative distribution curves for dietary weekly cadmium intake of duplicate method and dietary record method.
et al., 2000). It is often used to evaluate the accuracy of other methods. However, a duplicate study cost a lot in expense and human resource. Comparatively, dietary intake calculation from available food consumption and concentration data seems a good alternative, but the reliability and accuracy of this method needs validation. In our study, we calculated the dietary intake of lead and cadmium for children and adults from our former duplicate diet study carried out in Jinhu area in 2007. At the same time, we calculated dietary lead and cadmium intake from dietary recall and available lead/cadmium concentration data from the national food contamination monitoring system (2001–2006) in Jiangsu province. The result of the latter was validated by that of duplicate method. Comparison of two methods showed that in our study, results from dietary record method have no significant difference compared with that of duplicate diet method. It can be concluded that dietary lead and cadmium intakes for children and adult in Jinhu area can be correctly evaluated by combining dietary recall data and available contamination data. In order to evaluate the risks due to dietary intake of lead and cadmium, we compared our results with the PTWIs of lead and cadmium recommended by WHO/FAO. The result showed that the average dietary lead and cadmium intakes for children and adults in Jinhu area can be regarded as safe. As previously mentioned, the duplicate and dietary record methods have their own general method specific characteristics. However, the duplicate method is considered to provide the most accurate data concerning the effective amount of contaminants. Compared with dietary lead intakes from other duplicate studies summarized in Table 7, our results are higher. Wilhelm et al. (2003) carried out a 3–7-day duplicate study among 35 children aged between 1 and 5 years from Ger-
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Table 7 Comparison of lead and cadmium intakes with literature data. Country
Study type
Year
Age (years)
Dietary lead intake
Lead China
Duplicate study
2007
Germany
Duplicate study
1995
Germany Germany Australia
Duplicate study Duplicate study Duplicate study
1995 1998 –
Japan Japan
Duplicate study Duplicate study
2000 2000
This study This study Wilhelm et al. (2003) Wilhelm et al. (2003) Schrey et al. (2003) Wilhelm et al. (2005) Gulson et al. (2001) Gulson et al. (2001) Aung et al. (2004) Aung et al. (2006)
Duplicate study
1995
China Poland
Duplicate study Duplicate study
1993–1997 1990–2002
1.10 g/kg day 1.65 g/kg day 0.21–0.68 g/kg day 0.26 g/kg day 0.29 g/kg day 0.75 g/kg day 0.23 g/kg day 0.12 g/kg day 0.25 g/kg day 2g/kg week 0.87 g/kg week 0.26 g/kg day 0.10 g/kg day 0.45 g/kg day 46.4–86.6 g day−1 (F)
Median Median Median Median Median GM AM AM AM AM
America
24.7–65.8 1.9–7.0 1.3–5.2 24.0–64.0 1.5–5.3 1.0–6.0 6.0–11.0 20.0–39.0 (F) 4.2–6.0 3–6 28–40 0–7.0 ≥21.0 – 20.0–55.0
Median Median GM AM
Thomas et al. (1999) Thomas et al. (1999) Zhang et al. (2007) Marzec and Schlegel-Zawadzka (2004)
52.6–105.0 g day−1 (M)
AM
1.10 g/kg day 1.65 g/kg day 0.36 g/kg day 0.21–0.44 g/kg day 0.39 g/kg day 4.92 g/kg week 2.08 g/kg week 16.4–31.4 g day−1 (F)
Median Median Median
AM
21.2–34.5 g day−1 (M)
AM
Cadmium China
Duplicate study
2007
Germany Germany America Japan
Duplicate study Duplicate study Duplicate study Duplicate study
1995 1995 1995 2000
Eastern Poland
Duplicate study
1990–1993, 1998–2002
24.7–65.8 1.9–7.0 1.5–5.3 1.3–5.2 0–7.0 3–6 28–40 20–55
many and found that the median weekly lead intake for children ranged from 1.8 to 4.0 g (kgbw )−1 week−1 , for adults was 2.5 g (kgbw )−1 week−1 , which accounted for 12% and 10% of the PTWI of 25 g (kgbw )−1 week−1 . Another duplicate study carried out by the National Human Exposure Assessment Survey (NHEXAS) (Thomas et al., 1999) found that the median dietary intakes for children aged 0–7 years and adults were 0.26 g (kgbw )−1 day−1 and 0.1 g (kgbw )−1 day−1 which accounted only 7.28% and 2.8% of PTWI. Gulson et al. (2001) did a longitudinal 6-day duplicate diet study for female and children in Australia and found the daily lead intake was 0.12 g (kgbw )−1 day−1 for non-pregnant female and 0.23 g (kgbw )−1 day−1 for migrant children. Additionally, a seven consecutive day of duplicate study of 33 children aged 5 years old in Japan showed the mean lead intake was 0.25 g (kgbw )−1 day−1 (Aung et al., 2004). Our results of 1.65 g (kgbw )−1 day−1 for children and 1.10 g (kgbw )−1 day−1 for adults are higher than those listed above. As for cadmium, the dietary cadmium intake calculated from duplicate study in our study was relatively lower than those from others. Schrey et al. (2003) calculated the cadmium dietary intake of 14 children living in a remote area of Germany using a duplicate method, the median intake of which was 2.7 g (kgbw )−1 week−1 . Another duplicate study carried out by Wilhelm et al. (2002) in Germany showed the range of median weekly cadmium intake for different child groups were 1.5–3.6 g (kgbw )−1 week−1 . Duplicate analysis in Eastern Poland found the cadmium intake in the study varied from 16.4 to 31.4 g day−1 for women and from 21.2 to 34.5 g day−1 for men (Marzec and Schlegel-Zawadzka, 2004). National Human Exposure Assessment Survey (NHEXAS) carried out by EPA (Thomas et al., 1999) found the median of dietary intake for children aged 0–7 years was 0.39 g (kgbw )−1 day−1 . Aung et al. (2004) did a 7-day duplicate study of 25 pairs of children and adults in Japan. The average weekly cadmium intakes for children and
References
Median AM
This study This study Schrey et al. (2003) Wilhelm et al. (2002) Thomas et al. (1999) Aung et al. (2004) Marzec and Schlegel-Zawadzka (2004) Marzec and Schlegel-Zawadzka (2004)
adults were 4.92 g (kgbw )−1 week−1 and 2.08 g (kgbw )−1 week−1 accounted 70% and 26.5% of PTWI respectively, which were higher than those of our study. Conclusion In respect of determination of lead and cadmium intakes for children and adults, data calculated from dietary record method can give reliable data compared to that from duplicate method, at least in Jinhu area. It can be concluded that dietary record method accompanied with strict dietary survey as well as normative concentration monitoring data could also give comparatively accurate result for lead and cadmium dietary exposure instead of food duplicate method which often needs much human and financial resources. On the other hand, result of our study show the average lead and cadmium dietary intakes are all below FAO/WHO PTWI, which can be considered safe. However, a minority of children had their dietary lead/cadmium intake exceeding PTWI, and it deserves our attention. Acknowledgements The study reported here is supported by the National Natural Science Foundation of China (30671763) and the National Science and Technology Support Program (2006BAK02A01). The authors wish to thank all the survey staffs for sampling of duplicate portions, Jinhu CDC for assistance in recruiting volunteers as well as for sample preparation, and the Supervision, Inspection and Testing Center of Agricultural Products Quality and Security of Jiangsu province for the analysis of food samples. We would also like to express our thanks to the editor and anonymous referees for insightful comments on this paper.
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