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Food Additives & Contaminants: Part A Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tfac20
Dietary exposure to dioxins and dioxin-like PCBs of Hong Kong adults: results of the first Hong Kong Total Diet Study a
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Waiky W.K. Wong , Yiu-chung Yip , Koon-kay Choi , Y.Y. Ho & Ying Xiao a
Food and Environmental Hygiene Department, Risk Assessment Section, Centre for Food Safety, Hong Kong, China b
Government Laboratory, Hong Kong, China Accepted author version posted online: 27 Sep 2013.Published online: 27 Nov 2013.
To cite this article: Waiky W.K. Wong, Yiu-chung Yip, Koon-kay Choi, Y.Y. Ho & Ying Xiao (2013) Dietary exposure to dioxins and dioxin-like PCBs of Hong Kong adults: results of the first Hong Kong Total Diet Study, Food Additives & Contaminants: Part A, 30:12, 2152-2158, DOI: 10.1080/19440049.2013.849388 To link to this article: http://dx.doi.org/10.1080/19440049.2013.849388
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Food Additives & Contaminants: Part A, 2013 Vol. 30, No. 12, 2152–2158, http://dx.doi.org/10.1080/19440049.2013.849388
Dietary exposure to dioxins and dioxin-like PCBs of Hong Kong adults: results of the first Hong Kong Total Diet Study Waiky W.K. Wonga, Yiu-chung Yipb, Koon-kay Choib, Y.Y. Hoa and Ying Xiaoa* a
Food and Environmental Hygiene Department, Risk Assessment Section, Centre for Food Safety, Hong Kong, China; bGovernment Laboratory, Hong Kong, China
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(Received 13 August 2013; accepted 24 September 2013) Dioxins and dioxin-like polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) covered by the Stockholm Convention on POPs. To assess the associated health risk of the Hong Kong population, the dietary exposure of the Hong Kong population and various age–gender subgroups to dioxins and dioxin-like PCBs was estimated in the first Hong Kong Total Diet Study (TDS), where food samples were collected and prepared “as consumed”. A total of 142 composite food samples, mainly foods of animal origin and their products and oily food, were analysed for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) and dioxin-like PCBs by the high-resolution gas chromatograph/ high-resolution mass spectrometer (HRGC/HRMS) system. Dietary exposures were estimated by combining the analytical results with the food consumption data of Hong Kong adults. The mean and 95th percentile exposures to dioxins and dioxin-like PCBs of the Hong Kong population were 21.9 and 59.7 pg toxic equivalent (TEQ) kg−1 body weight (bw) month−1 respectively, which amounted to 31.3% and 85.2% of the provisional tolerable monthly intake (PTMI). The main dietary source of dioxins and dioxin-like PCBs was “Fish and seafood and their products” (61.9% of the total exposure), followed by “Meat, poultry and game and their products” (20.0%) and “Mixed dishes” (6.95%). The study findings suggest that the Hong Kong population is unlikely to experience the major undesirable health effects of dioxins and dioxin-like PCBs. Keywords: dioxins; dioxin-like PCBs; total diet study
Introduction “Dioxins” refers to polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), whereas “dioxin-like PCBs” refers to polychlorinated biphenyls (PCBs) that exhibit toxicological properties similar to dioxins. They are persistent organic pollutants (POPs) covered by the Stockholm Convention on POPs (United Nations Environment Programme 2001). They are hydrophobic and lipophilic and extremely resistant to chemical and biological degradation and therefore persist in the environment and bioaccumulate in the food chain (Van den Berg et al. 2006; European Food Safety Authority 2010). Dioxins are ubiquitous in the environment, occurring naturally (e.g. volcanic eruptions and forest fires), and as by-products of combustion (e.g. waste incineration) and various industrial processes (e.g. production of chemicals, chlorine bleaching of paper pulp, and smelting). In contrast, PCBs were manufactured in the past for a variety of industrial uses such as electrical insulators or dielectric fluids and specialised hydraulic fluids. Their use has been banned by most countries since the 1970s (WHO 2002; FAO/WHO 2006). However, their release into the environment still occurs from the disposal of large-scale obsolescent electrical equipment and waste (WHO 2010). Besides, PCBs are also listed under Annex C of the Stockholm Convention as one of the unintentionally produced POPs with possible *Corresponding author. Email: [email protected] © 2013 Taylor & Francis
formation in combustion and incineration processes (United Nations Environment Programme 2001). Sources of dioxins and dioxin-like PCBs entering the food chain include the new emissions, mainly via the air route, and redistribution of deposits or reservoirs in the environment. Due to their persistence, a large part of current exposure is due to the release of dioxins and dioxin-like PCBs that occurred in the past (FAO/WHO 2006). Dioxins would concentrate in the fatty tissues of meat and poultry or seafood, and animals with a longer lifespan may have a higher potential accumulation of dioxins in their fat tissues. Foods of animal origin such as meat, dairy products, eggs and fishes tend to have higher concentrations of dioxins and dioxin-like PCBs (EC 2001; WHO 2010). Concerns about dioxins and dioxin-like PCBs are mainly due to their toxic effects on a number of systems, including endocrine, immune and developing nervous systems (WHO 2010). The International Agency for Research on Cancer (IARC) classifies three congeners, namely 2,3,7,8-tetraCDD (TCDD), 2,3,4,7,8-pentaCDF and PCB 126 in Group 1 (i.e. carcinogenic to humans) (International Agency for Research on Cancer 1997; WHO IARC Monograph Working Group 2009). In 2001, JECFA established a provisional tolerable monthly intake (PTMI) of 70 pg kg−1 body weight
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Food Additives & Contaminants: Part A (bw) month−1 for PCDDs, PCDFs and dioxin-like PCBs expressed as toxic equivalent (TEQ) (WHO 2002). The Centre for Food Safety (CFS), the food safety control authority of the Government of Hong Kong Special Administrative Region of the People’s Republic of China, started to conduct its first Hong Kong Total Diet Study (TDS) in 2010, aiming to provide the dietary exposure estimates to various contaminants and nutrients of the Hong Kong population and various age–gender subgroups. TDS has been recognised internationally as the most cost-effective way to estimate the dietary exposures to food chemicals or nutrients. It focuses on the analysis of food chemical substances in the whole diet and assesses the dietary exposures to such chemical substances actually ingested by the population. The first Hong Kong TDS determined the contents of dioxins and dioxin-like PCBs in food as consumed and estimated the dietary exposures of the Hong Kong population to assess the population’s associated health risk.
Materials and methods Food consumption data The food consumption data were taken from the Hong Kong population-based Food Consumption Survey (FCS) conducted by the CFS in 2005–2007 (FEHD 2010). In the FCS, 5008 Hong Kong adults aged 20–84 years were invited through a quota sampling by gender and age groups and completed two non-consecutive 24-h dietary intake questionnaires.
Food sampling and preparation A total of 150 commonly consumed food items were selected for the study, based on the food consumption pattern of the Hong Kong population obtained from the FCS (FEHD 2010). Three samples of each TDS food item were collected and prepared on each of the four occasions from March 2010 to February 2011. The samples were purchased from a range of retail outlets in different parts of Hong Kong, based on the buying habits of the majority of the Hong Kong population. They were then prepared as food normally consumed, in a manner consistent with local cultural habits, and were homogenised individually. The three prepared samples of the same food item were combined into a composite sample. A total of 1800 samples were collected and combined into 600 composite samples for chemical analysis. The prepared samples were kept at –18°C prior to laboratory analysis (FEHD 2011). Among the 150 TDS food items, 71 of them were selected for testing dioxins and dioxin-like PCBs with reference to their occurrence in food. They are mainly foods of animal origin and their products and oily food. Due to limited resources, only samples from two occasions (i.e. June–August 2010 and September–November
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2010, respectively) were tested. A total of 142 composite samples were used for testing. Chemical analysis of dioxins and dioxin-like PCBs The dioxin and dioxin-like PCB levels in food samples, including 29 congeners with the toxic equivalency factors (TEFs) established by WHO (Van den Berg et al. 2006), were analysed by a high-resolution gas chromatographhigh-resolution mass spectrometer (HRGC/HRMS) system (Agilent 6890 Gas Chromatograph (Agilent Technologies Inc., Santa Clara, CA, USA) coupled with a Water Micro Mass Autospec Ultima (Waters Corporation, Milford, MA, USA)). The analysis was conducted by the Government Laboratory of Hong Kong using the method described in Method 1613 by the US Environmental Protection Agency (1994). Stable isotope-labelled analogues of the fifteen 2,3,7,8-substituted PCDDs/PCDFs and 12 dioxin-like PCB congeners were spiked quantitatively into a measured amount of sample, which was then extracted by organic solvents. Various clean-up columns were used to clean-up the sample extract. The automated clean-up system (PowerPrep Workstation, Fluid Management Systems Inc., Watertown, MA, USA) was employed. After sample clean-up, the PCDDs/PCDFs and dioxin-like PCBs in the sample extract were fractionated with carbon columns. After fractionation, the sample extract was concentrated to near dryness, and prior to analysis by the HRGC/HRMS system, 1,2,3,4-13C12-TCDD and 1,2,3,7,8,9-13C12-HxCDD were added to the fraction as injection internal standards for the analysis of dioxins. 13 C12-PCB congeners 70, 111, 138 and 170 were added to the fraction as injection internal standards for the analysis of dioxin-like PCBs. The analytes were separated by HRGC and detected by HRMS set at a resolution of ≥10,000 in selected ion requisition (SIR) mode. Identification was conducted by comparing the retention time and the ion-abundance ratio of two exact m/zs of the analytes with the retention time of the corresponding isotope-labelled standard and the theoretical ion-abundance ratio of the two exact m/z’s. The concentrations of 1,2,3,7,8,9-HxCDD and OCDF were determined using the internal standard technique. Those for the other PCDDs/PCDFs and dioxinlike PCB congeners were determined using the isotope dilution technique. The concentration of dioxins and dioxin-like PCBs was expressed as TEQ and calculated by summing the contribution from each congener, which was calculated by multiplying the concentration of the specific congener with the corresponding TEF (Van den Berg et al. 2006). LODs (fresh weight) were given for the following: PCDDs, 0.003–0.009 pg g−1; PCDFs, 0.003–0.014 pg g−1; and dioxin-like PCBs, 0.001– 0.002 pg g−1.
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Analytical quality assurance The pertinent quality assurance/quality control requirements as given in USEPA Method 1613 (US Environmental Protection Agency 1994) were adopted to ensure the correct identification and quantification of the target compounds: (1) a method blank was analysed for every batch of 12 test samples to monitor the presence of environmental contamination, where the concentrations of the native compounds should not be greater than 0.05 pg µl−1 in the method blank; (2) one duplicate was performed to check the precision (relative per cent difference ≤ 40%); (3) one sample spike was performed to check the recovery (80–120%); (4) recovery of the labelled compounds was monitored by the injection internal standard (60–120%); (5) a GC-HRMS sensitivity check standard was injected at the beginning and at the end of every batch of test samples, where the signal-tonoise ratio of each of the native dioxins and the area sum of the two exact m/z ions specified for the congener 2,3,7,8-TCDD should not be less than 3 and 1000 counts, respectively; (6) a midpoint calibration standard was analysed for every 12 analytical samples, where the deviation of the expected values of the native compounds and that of the labelled compounds should be ≤15% and 30%, respectively; (7) the computed ion abundance ratio for each analyte was compared with the theoretical ion abundance ratio, where the ratio of the integrated areas of the two exact m/z ions specified for the native/labelled compounds should be within the QC limits (±15% windows around the theoretical ion abundance ratios); and (8) the certified reference material CARP-1 prepared from ground whole carp by the National Research Council Canada was examined as a control sample for method verification purposes and for assuring the quality of the results determined by the Government Laboratory, where the analytical results were found to be within the certified mass fractions for selected dioxins and PCBs in CARP-1. The Government Laboratory annually participates in the Interlaboratory Comparison on Persistent Organic Pollutants in Food organised by the Department of Analytical Chemistry, Norwegian Institute of Public Health, Oslo, Norway. The 2011 results related to the determination of selected dioxins and PCBs in the three test materials, including salmon filet, mozzarella cheese and eggs, were found to be satisfactory.
Dietary exposure estimates The FCS results revealed that over 1400 food items were being consumed by the Hong Kong population (FEHD 2010). A food mapping process was carried by mapping the TDS food items with food items captured by FCS in order to cover the whole diet of the Hong Kong population. The mean levels of the TDS food items were assigned to the mapped FCS food
items with an application of conversion factors taking reference to the differences in water content (FEHD 2011). To cite an example, scallop in TDS food was mapped to scallop and other bivalve in FCS. After food mapping for all 150 TDS food items, over 99% of the average diet of the population would be covered, but for the 71 TDS food items used for the testing of dioxins and dioxin-like PCBs about 24% of the average diet of the population was covered. Nevertheless, the remaining 76% of food was water, non-alcoholic beverages and food of plant origin which were not considered as significant sources of dioxins and dioxin-like PCBs. The dietary exposures were then estimated by combining the assigned levels of mapped FCS food items with their corresponding food consumption amounts. A weighting based on the population distribution by age and gender in the 2006 Population By-census was applied to adjust for bias arising from the age–gender quotas (FEHD 2010, 2011). The mean and 95th percentile of the exposure levels among the FCS respondents after weighting by age–gender are used to represent the dietary exposures of the average and the high consumer of the Hong Kong population, respectively. Dietary exposure estimation was performed with the aid of an in-house-developed webbased computer system, Exposure Assessment System (EASY), that takes food mapping and weighting of data into consideration. Results and discussion A total of 142 composite samples on two occasions were tested for dioxins and dioxin-like PCBs. All 142 composite samples were detected with at least one of the dioxin and dioxin-like PCB congeners, in which about two-thirds (66%) of the test results were found to be above the LODs of individual dioxin and dioxin-like PCB congeners. The non-detected results were treated according to the recommendation of the WHO on the evaluation of low-level contamination of food in the treatment for those nondetected results (WHO 1995). All non-detected results were assigned with levels at half the LOD for expressing their contents as well as estimating the dietary exposures. Table 1 shows the concentrations of dioxins and dioxin-like PCBs in different food groups. Among all the food groups, the group “Fish and seafood and their products” was found to contain the highest dioxin and dioxinlike PCB level (mean = 0.440 pg TEQ g−1), followed by the groups “Eggs and their products” (mean = 0.137 pg TEQ g−1), “Fats and oils” (mean = 0.0937 pg TEQ g−1), and “Meat, poultry and game and their products” (mean = 0.0909 pg TEQ g−1). Under the food group “Fish and seafood and their products”, the mean levels of dioxins and dioxin-like PCBs ranged from 0.0116 to 1.06 pg TEQ g−1. Mandarin fish was found to contain the highest level (mean = 1.06 pg TEQ g−1), followed by oyster
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Table 1. Dioxin and dioxin-like PCB contents (pg TEQ g−1) in food groups of the first Hong Kong Total Diet Study.
Food group Cereals and their products Meat, poultry and game and their products Eggs and their products Fish and seafood and their products Dairy products Fats and oils Beverages, non-alcoholic Mixed dishes Others
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Total
Number of composite samples
Percentage of the test results < LOD
24 24 6 38 10 4 6 22 8
45 23 16 20 57 33 58 40 53
142
34
Mean (pg TEQ g−1) [range]a 0.0211 0.0909 0.137 0.440 0.0208 0.0937 0.0110 0.0184 0.0135
[0.00701–0.0850] [0.0120–0.257] [0.0204–0.302] [0.00888–1.27] [0.00701–0.0717] [0.0109–0.282] [0.00701–0.0147] [0.00716–0.0388] [0.00771–0.0303]
a
Note: As fewer than 60% of the results are below the LODs, half of the LOD is used for all results less than the LOD when calculating the concentrations.
(mean = 0.926 pg TEQ g−1) and pomfret fish (mean = 0.885 pg TEQ g−1), in which they were also the top three items with the highest levels among all the 71 food items. The proportions of dioxins alone and dioxin-like PCBs were compared among the four food groups with the highest levels, and are shown in Table 2. Higher proportions of dioxin-like PCBs were found in two food groups, “Fish and seafood and their products” (58.9%) and “Fats and oils” (69.3%), while higher proportions of dioxin alone were found in other two groups, “Eggs and their products” (71.0%) and “Meat, poultry and game and their products” (62.3%). Although there were variations of proportions between dioxins alone and dioxin-like PCBs, it showed that both dioxins and dioxin-like PCBs would also contribute to our sources of exposure. The estimated mean dietary exposure to dioxins and dioxin-like PCBs of the Hong Kong population was 21.9 pg TEQ kg−1 bw month−1 (31.3% of the PTMI) and its 95th percentile was 59.7 pg TEQ kg−1 bw month−1 (85.2% of
the PTMI). Furthermore, 3.07% of the Hong Kong population was estimated to exceed the PTMI. For adult males and females (aged 20–84 years), the estimated mean dietary exposure values to dioxins and dioxin-like PCBs were 21.9 and 22.0 pg TEQ kg−1 bw month−1, respectively. Among the 12 age–gender groups, the estimated mean dietary exposures to dioxins and dioxin-like PCBs of the individual subgroups ranged from 17.8 pg TEQ kg−1 bw month−1 (males aged 20–29 years) to 26.3 pg TEQ kg−1 bw month−1 (males aged 60–69 years) and the 95th percentile ranged from 45.9 pg TEQ kg−1 bw month−1 (males aged 20–29 years) to 73.5 pg TEQ kg−1 bw month−1 (males aged 60–69 years) (Figure 1). Among the 12 age–gender groups, all the estimated mean dietary exposures were found below the PTMI (the highest contributed 37.5% of the PTMI), but the estimated 95th percentile dietary exposures of the following three subgroups, namely males aged 60–69 years (73.5 pg TEQ kg−1 bw month−1), females aged 60–69 years (72.7 pg TEQ kg−1 bw month−1), and females aged
Table 2. Proportions of dioxins and dioxin-like PCBs to the sum of dioxins and dioxin-like PCBs among the four food groups with the highest levels of the first Hong Kong Total Diet Study. Mean (pg TEQ g−1)a
Percentagec
Food group
Totalb
Dioxins alone
Dioxin-like PCBs
Dioxins alone
Dioxin-like PCBs
Fish and seafood and their products Eggs and their products Fats and oils Meat, poultry and game and their products
0.440 0.137 0.0937 0.0909
0.181 0.0973 0.0288 0.057
0.259 0.0398 0.0649 0.0343
41.1 71.0 30.7 62.3
58.9 29.0 69.3 37.7
Notes: aAs fewer than 60% of the results are below the LODs, half of the LOD is used for all results less than the LOD when calculating the concentrations. b Total is the sum of dioxins and dioxin-like PCBs. c Percentage is the percentage of dioxins alone or dioxin-like PCBs to the sum of dioxins and dioxin-like PCBs.
W.W.K. Wong et al. Dietary exposure (pg–1 TEQ kg–1 bw month–1)
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95th percentile
60 50 40 30 20 10
20
–
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M
al e Fe 30 m al – e 30 39 M – a le 39 F 40 em al – e 40 49 M – 49 ale F 50 em al – e 50 59 M – 59 ale F 60 em al – e 60 69 M – 69 ale F 70 em al – e 70 84 M – a le 84 F 20 em al – e 20 84 M – 84 ale Fe m al e
0
– 20
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Average
PTMI of 70 pg–1 TEQ kg–1 bw month–1
70
29
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Age-gender groups
Figure 1. Mean and 95th percentile dietary exposures to dioxin and dioxin-like PCBs of the individual age–gender groups of the Hong Kong population of the first Hong Kong Total Diet Study.
70–84 years (73.1 pg TEQ kg−1 bw month−1), were found to be slightly exceeding the PTMI (which amounted to 105%, 104% and 104% of the PTMI, respectively). In addition, the estimated 95th percentile dietary exposure (69.5 pg TEQ kg−1 bw month−1) of females aged 30–39 years, who fall into the child-bearing age range, was close to the PTMI (99.3% of the PTMI). Therefore, the Hong Kong population was unlikely to experience major undesirable health effects of dioxins and dioxin-like PCBs. Although some age–gender groups at the 95th percentile exposures were found to be close to or slightly exceeding the PTMI, an intake above the PTMI in a certain period of time does not automatically mean that health is at risk provided that the average intake over a long period is not exceeded as PTMI is emphasised by lifetime exposure. The mean dietary exposures to dioxins and dioxin-like PCBs of the Hong Kong population by the TDS food groups and contribution of the total exposure are shown in Table 3. In our findings, the main dietary source of dioxins and dioxin-like PCBs was the group “Fish and seafood and their products” (61.9% of the total exposure), followed by the groups “Meat, poultry and game and their products” (20.0%) and “Mixed dishes” (6.95%). Similar findings were also revealed in other dietary exposure studies that aquatic food and meat are the major food contributors. However, dairy products only contributed to 1.28% of the total exposure, although it has been reported to be one of the major sources of exposure in the Western diet. It may be due to the difference in the consumption pattern of dairy products. In the food group “Fish and seafood and their products”, fish and fishery products were found to be the
Table 3. Mean dietary exposures (pg TEQ kg−1 bw month−1) to dioxins and dioxin-like PCBs of the Hong Kong population in food groups of the first Hong Kong Total Diet Study and their contribution of the total exposure.
Food group Cereals and their products Meat, poultry and game and their products Eggs and their products Fish and seafood and their products Dairy products Fats and oils Beverages, non-alcoholic Mixed dishes Others Totalb
Dietary exposure (pg TEQ kg−1 bw month−1)a
Percentage contribution of total exposure
1.08
4.92
4.39
20.0
0.297 13.6
1.35 61.9
0.280 0.157 0.584
1.28 0.714 2.66
1.52 0.0308
6.95 0.141
21.9
100
a
Notes: As fewer than 60% of results are below the LOD, half of the LOD is used for all results less than the LOD when calculating the exposure estimates. b Figures may not add up to the total due to rounding.
major sources of dioxins and dioxin-like PCBs (55.6% of the total exposure). About half of the exposure from fish (i.e. 25.0% of the total exposure) was contributed by the four fish species, namely grass carp (8.14% of total exposure), golden thread (6.25%), pomfret fish (5.96%) and mandarin fish (4.70%). Mandarin fish and pomfret fish were also found to contain the highest levels of dioxins and dioxin-like PCBs. The contribution of these two fish species together was about 10% of the total
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Table 4. Comparison of dietary exposures of dioxins and dioxin-like PCBs. Dietary exposure (pg TEQ kg−1 bw month−1) Average (years)
95th or 97.5th percentile
15.6 (aged 2 years and above)a,d
40.6 (aged 2 years and above) (95th percentile)a,d
21.9c 25.2e
59.7 (95th percentile)c
27 (adult)a,d
51 (adult) (97.5th percentile)a,d
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Places USA (TDS 2001–2004) (US Food and Drug Administration 2006) Australia (2004) (Food Standards Australia New Zealand 2004) Hong Kongf Japan (2009) (Ministry of Health, Labour and Welfare 2010) UK (TDS 2001) (Food Standard Agency of the UK 2003) China (TDS 2000) (Li et al. 2007) The Netherlands (2001) (Food Standards Australia New Zealand 2004) Finland (1991–1999) (EC 2000) Sweden (1999) (EC 2000)
18.2
a,b,c
4.5–28.8 (adult male)a,d 39e 55.5 (adult)a,d 56.1a,d
Notes: aWHO TEF 1998. b PCDD/PCDFs only. c Medium bound – assumed results reported as being below the LOD are at 0.5 LOD. d Upper bound – assumed results reported as being below the LOD are at the LOD. e Lower bound – assumed results reported as being below the LOD are zero. f Data from the current study.
exposure. In the food group “Meat, poultry and game and their products”, about two-thirds of the exposure from this food group was contributed by chicken and beef products (13.3% of the total exposure). The dietary exposures to dioxins and dioxin-like PCBs of the Hong Kong population were also compared with those obtained from other places, and are summarised in Table 4. However, direct comparison of the data has to be done with caution due to different experimental factors and considerations including the time the studies were carried out, research methodologies, methods of collection of consumption data, methods of contaminant analysis, methods of treating results below detection limits, and the difference of the TEF schemes applied.
Conclusion In summary, the estimated mean dietary exposure to dioxins and dioxin-like PCBs of the Hong Kong population was 21.9 pg TEQ kg−1 bw month−1 (31.3% of the PTMI) and its 95th percentile was 59.7 pg TEQ kg−1 bw month−1 (85.2% of the PTMI). Therefore, the Hong Kong population is unlikely to experience major undesirable health effects of dioxins and dioxin-like PCBs. Food of animal origin, particularly fish, meat and poultry, is the major source of exposure to dioxins and dioxin-like PCBs. Nevertheless, having considered their carcinogenic risks, efforts should be made to reduce the dietary exposure to dioxins and dioxin-like PCBs of the Hong Kong population.
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humans. Vol. 69, p. 33. Available from: http://www.inchem. org/documents/iarc/vol69/dioxin.html Li J, Wu Y, Zhang L, Yun Z. 2007. Dietary intake of polychlorinated dioxins, furans and dioxin-like polychlorinated biphenyls from foods of animal origin in China. Food Addit Contam. 24:186–193. Ministry of Health, Labour and Welfare. 2010. The findings of survey on daily dietary exposure to dioxin in 2009. Japan: MHLW. Japanese. [cited 2013 Apr 29]. Available from: http://www.mhlw.go.jp/topics/bukyoku/iyaku/syoku-anzen/ dioxin/sessyu09/index.html United Nations Environment Programme. 2001. Stockholm Convention on Persistent Organic Pollutants (POPs). Geneva: Secretariat of the Stockholm Convention [Internet]. [cited 2013 Apr 29]. Available from: http://chm.pops.int/Convention/ ThePOPs/ListingofPOPs/tabid/2509/Default.aspx U.S. Environmental Protection Agency. 1994. Method 1613 Tetrathrough octa-chlorinated dioxins and furans by isotope dilution HRGC/HRMS [Internet]. [cited 2013 Oct 17]. Available from: http://water.epa.gov/scitech/methods/cwa/organics/dioxins/ upload/2007_07_10_methods_method_dioxins_1613.pdf U.S. Food and Drug Administration. 2006. PCDD/PCDF exposure estimates from TDS samples collected in 2001–2004 [Internet]. [cited 2013 Apr 29]. Available from: http://www.fda.gov/Food/FoodborneIllnessContaminants/ ChemicalContaminants/ucm077498.htm
Van den Berg M, Ls B, Denison M, De Vito M, Farland W, Feeley M, Fiedler H, Hakansson H, Hanberg A, Haws L, et al. 2006. The 2005 World Health Organization reevaluation of human and mammalian toxic equivalency factors for dioxins and dioxin-like compounds. Toxicol Sci. 93:223–241. WHO IARC Monograph Working Group. 2009. Special report: policy – a review of human carcinogens – Part F: chemical agents and related occupations. The Lancet Oncol. 10:1143–1144. [WHO] World Health Organization. 1995. GEMS/Food-EURO second workshop on reliable evaluation of low-level contamination of food – report of a workshop in the frame of GEMS/Food-EURO [Internet]. [cited 2013 Oct 17]. Available from: http://www.who.int/foodsafety/publications/ chem/en/lowlevel_may1995.pdf [WHO] World Health Organization. 2002. Safety evaluation on certain food additives and contaminants: polychlorinated dibenzodioxins, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls. WHO Food Additives Series: 48. Geneva: WHO. Available from: http://www.inchem.org/ documents/jecfa/jecmono/v48je20.htm [WHO] World Health Organization. 2010. Exposure to dioxins and dioxin-like substances: a major public health concern [Internet]. [cited 2013 Oct 17]. Available from: http://www. who.int/entity/ipcs/features/dioxins.pdf
Food Additives & Contaminants: Part A Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tfac20
Dietary exposure to dioxins and dioxin-like PCBs of Hong Kong adults: results of the first Hong Kong Total Diet Study a
b
b
a
a
Waiky W.K. Wong , Yiu-chung Yip , Koon-kay Choi , Y.Y. Ho & Ying Xiao a
Food and Environmental Hygiene Department, Risk Assessment Section, Centre for Food Safety, Hong Kong, China b
Government Laboratory, Hong Kong, China Accepted author version posted online: 27 Sep 2013.Published online: 27 Nov 2013.
To cite this article: Waiky W.K. Wong, Yiu-chung Yip, Koon-kay Choi, Y.Y. Ho & Ying Xiao (2013) Dietary exposure to dioxins and dioxin-like PCBs of Hong Kong adults: results of the first Hong Kong Total Diet Study, Food Additives & Contaminants: Part A, 30:12, 2152-2158, DOI: 10.1080/19440049.2013.849388 To link to this article: http://dx.doi.org/10.1080/19440049.2013.849388
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Food Additives & Contaminants: Part A, 2013 Vol. 30, No. 12, 2152–2158, http://dx.doi.org/10.1080/19440049.2013.849388
Dietary exposure to dioxins and dioxin-like PCBs of Hong Kong adults: results of the first Hong Kong Total Diet Study Waiky W.K. Wonga, Yiu-chung Yipb, Koon-kay Choib, Y.Y. Hoa and Ying Xiaoa* a
Food and Environmental Hygiene Department, Risk Assessment Section, Centre for Food Safety, Hong Kong, China; bGovernment Laboratory, Hong Kong, China
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(Received 13 August 2013; accepted 24 September 2013) Dioxins and dioxin-like polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) covered by the Stockholm Convention on POPs. To assess the associated health risk of the Hong Kong population, the dietary exposure of the Hong Kong population and various age–gender subgroups to dioxins and dioxin-like PCBs was estimated in the first Hong Kong Total Diet Study (TDS), where food samples were collected and prepared “as consumed”. A total of 142 composite food samples, mainly foods of animal origin and their products and oily food, were analysed for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) and dioxin-like PCBs by the high-resolution gas chromatograph/ high-resolution mass spectrometer (HRGC/HRMS) system. Dietary exposures were estimated by combining the analytical results with the food consumption data of Hong Kong adults. The mean and 95th percentile exposures to dioxins and dioxin-like PCBs of the Hong Kong population were 21.9 and 59.7 pg toxic equivalent (TEQ) kg−1 body weight (bw) month−1 respectively, which amounted to 31.3% and 85.2% of the provisional tolerable monthly intake (PTMI). The main dietary source of dioxins and dioxin-like PCBs was “Fish and seafood and their products” (61.9% of the total exposure), followed by “Meat, poultry and game and their products” (20.0%) and “Mixed dishes” (6.95%). The study findings suggest that the Hong Kong population is unlikely to experience the major undesirable health effects of dioxins and dioxin-like PCBs. Keywords: dioxins; dioxin-like PCBs; total diet study
Introduction “Dioxins” refers to polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), whereas “dioxin-like PCBs” refers to polychlorinated biphenyls (PCBs) that exhibit toxicological properties similar to dioxins. They are persistent organic pollutants (POPs) covered by the Stockholm Convention on POPs (United Nations Environment Programme 2001). They are hydrophobic and lipophilic and extremely resistant to chemical and biological degradation and therefore persist in the environment and bioaccumulate in the food chain (Van den Berg et al. 2006; European Food Safety Authority 2010). Dioxins are ubiquitous in the environment, occurring naturally (e.g. volcanic eruptions and forest fires), and as by-products of combustion (e.g. waste incineration) and various industrial processes (e.g. production of chemicals, chlorine bleaching of paper pulp, and smelting). In contrast, PCBs were manufactured in the past for a variety of industrial uses such as electrical insulators or dielectric fluids and specialised hydraulic fluids. Their use has been banned by most countries since the 1970s (WHO 2002; FAO/WHO 2006). However, their release into the environment still occurs from the disposal of large-scale obsolescent electrical equipment and waste (WHO 2010). Besides, PCBs are also listed under Annex C of the Stockholm Convention as one of the unintentionally produced POPs with possible *Corresponding author. Email: [email protected] © 2013 Taylor & Francis
formation in combustion and incineration processes (United Nations Environment Programme 2001). Sources of dioxins and dioxin-like PCBs entering the food chain include the new emissions, mainly via the air route, and redistribution of deposits or reservoirs in the environment. Due to their persistence, a large part of current exposure is due to the release of dioxins and dioxin-like PCBs that occurred in the past (FAO/WHO 2006). Dioxins would concentrate in the fatty tissues of meat and poultry or seafood, and animals with a longer lifespan may have a higher potential accumulation of dioxins in their fat tissues. Foods of animal origin such as meat, dairy products, eggs and fishes tend to have higher concentrations of dioxins and dioxin-like PCBs (EC 2001; WHO 2010). Concerns about dioxins and dioxin-like PCBs are mainly due to their toxic effects on a number of systems, including endocrine, immune and developing nervous systems (WHO 2010). The International Agency for Research on Cancer (IARC) classifies three congeners, namely 2,3,7,8-tetraCDD (TCDD), 2,3,4,7,8-pentaCDF and PCB 126 in Group 1 (i.e. carcinogenic to humans) (International Agency for Research on Cancer 1997; WHO IARC Monograph Working Group 2009). In 2001, JECFA established a provisional tolerable monthly intake (PTMI) of 70 pg kg−1 body weight
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Food Additives & Contaminants: Part A (bw) month−1 for PCDDs, PCDFs and dioxin-like PCBs expressed as toxic equivalent (TEQ) (WHO 2002). The Centre for Food Safety (CFS), the food safety control authority of the Government of Hong Kong Special Administrative Region of the People’s Republic of China, started to conduct its first Hong Kong Total Diet Study (TDS) in 2010, aiming to provide the dietary exposure estimates to various contaminants and nutrients of the Hong Kong population and various age–gender subgroups. TDS has been recognised internationally as the most cost-effective way to estimate the dietary exposures to food chemicals or nutrients. It focuses on the analysis of food chemical substances in the whole diet and assesses the dietary exposures to such chemical substances actually ingested by the population. The first Hong Kong TDS determined the contents of dioxins and dioxin-like PCBs in food as consumed and estimated the dietary exposures of the Hong Kong population to assess the population’s associated health risk.
Materials and methods Food consumption data The food consumption data were taken from the Hong Kong population-based Food Consumption Survey (FCS) conducted by the CFS in 2005–2007 (FEHD 2010). In the FCS, 5008 Hong Kong adults aged 20–84 years were invited through a quota sampling by gender and age groups and completed two non-consecutive 24-h dietary intake questionnaires.
Food sampling and preparation A total of 150 commonly consumed food items were selected for the study, based on the food consumption pattern of the Hong Kong population obtained from the FCS (FEHD 2010). Three samples of each TDS food item were collected and prepared on each of the four occasions from March 2010 to February 2011. The samples were purchased from a range of retail outlets in different parts of Hong Kong, based on the buying habits of the majority of the Hong Kong population. They were then prepared as food normally consumed, in a manner consistent with local cultural habits, and were homogenised individually. The three prepared samples of the same food item were combined into a composite sample. A total of 1800 samples were collected and combined into 600 composite samples for chemical analysis. The prepared samples were kept at –18°C prior to laboratory analysis (FEHD 2011). Among the 150 TDS food items, 71 of them were selected for testing dioxins and dioxin-like PCBs with reference to their occurrence in food. They are mainly foods of animal origin and their products and oily food. Due to limited resources, only samples from two occasions (i.e. June–August 2010 and September–November
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2010, respectively) were tested. A total of 142 composite samples were used for testing. Chemical analysis of dioxins and dioxin-like PCBs The dioxin and dioxin-like PCB levels in food samples, including 29 congeners with the toxic equivalency factors (TEFs) established by WHO (Van den Berg et al. 2006), were analysed by a high-resolution gas chromatographhigh-resolution mass spectrometer (HRGC/HRMS) system (Agilent 6890 Gas Chromatograph (Agilent Technologies Inc., Santa Clara, CA, USA) coupled with a Water Micro Mass Autospec Ultima (Waters Corporation, Milford, MA, USA)). The analysis was conducted by the Government Laboratory of Hong Kong using the method described in Method 1613 by the US Environmental Protection Agency (1994). Stable isotope-labelled analogues of the fifteen 2,3,7,8-substituted PCDDs/PCDFs and 12 dioxin-like PCB congeners were spiked quantitatively into a measured amount of sample, which was then extracted by organic solvents. Various clean-up columns were used to clean-up the sample extract. The automated clean-up system (PowerPrep Workstation, Fluid Management Systems Inc., Watertown, MA, USA) was employed. After sample clean-up, the PCDDs/PCDFs and dioxin-like PCBs in the sample extract were fractionated with carbon columns. After fractionation, the sample extract was concentrated to near dryness, and prior to analysis by the HRGC/HRMS system, 1,2,3,4-13C12-TCDD and 1,2,3,7,8,9-13C12-HxCDD were added to the fraction as injection internal standards for the analysis of dioxins. 13 C12-PCB congeners 70, 111, 138 and 170 were added to the fraction as injection internal standards for the analysis of dioxin-like PCBs. The analytes were separated by HRGC and detected by HRMS set at a resolution of ≥10,000 in selected ion requisition (SIR) mode. Identification was conducted by comparing the retention time and the ion-abundance ratio of two exact m/zs of the analytes with the retention time of the corresponding isotope-labelled standard and the theoretical ion-abundance ratio of the two exact m/z’s. The concentrations of 1,2,3,7,8,9-HxCDD and OCDF were determined using the internal standard technique. Those for the other PCDDs/PCDFs and dioxinlike PCB congeners were determined using the isotope dilution technique. The concentration of dioxins and dioxin-like PCBs was expressed as TEQ and calculated by summing the contribution from each congener, which was calculated by multiplying the concentration of the specific congener with the corresponding TEF (Van den Berg et al. 2006). LODs (fresh weight) were given for the following: PCDDs, 0.003–0.009 pg g−1; PCDFs, 0.003–0.014 pg g−1; and dioxin-like PCBs, 0.001– 0.002 pg g−1.
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Analytical quality assurance The pertinent quality assurance/quality control requirements as given in USEPA Method 1613 (US Environmental Protection Agency 1994) were adopted to ensure the correct identification and quantification of the target compounds: (1) a method blank was analysed for every batch of 12 test samples to monitor the presence of environmental contamination, where the concentrations of the native compounds should not be greater than 0.05 pg µl−1 in the method blank; (2) one duplicate was performed to check the precision (relative per cent difference ≤ 40%); (3) one sample spike was performed to check the recovery (80–120%); (4) recovery of the labelled compounds was monitored by the injection internal standard (60–120%); (5) a GC-HRMS sensitivity check standard was injected at the beginning and at the end of every batch of test samples, where the signal-tonoise ratio of each of the native dioxins and the area sum of the two exact m/z ions specified for the congener 2,3,7,8-TCDD should not be less than 3 and 1000 counts, respectively; (6) a midpoint calibration standard was analysed for every 12 analytical samples, where the deviation of the expected values of the native compounds and that of the labelled compounds should be ≤15% and 30%, respectively; (7) the computed ion abundance ratio for each analyte was compared with the theoretical ion abundance ratio, where the ratio of the integrated areas of the two exact m/z ions specified for the native/labelled compounds should be within the QC limits (±15% windows around the theoretical ion abundance ratios); and (8) the certified reference material CARP-1 prepared from ground whole carp by the National Research Council Canada was examined as a control sample for method verification purposes and for assuring the quality of the results determined by the Government Laboratory, where the analytical results were found to be within the certified mass fractions for selected dioxins and PCBs in CARP-1. The Government Laboratory annually participates in the Interlaboratory Comparison on Persistent Organic Pollutants in Food organised by the Department of Analytical Chemistry, Norwegian Institute of Public Health, Oslo, Norway. The 2011 results related to the determination of selected dioxins and PCBs in the three test materials, including salmon filet, mozzarella cheese and eggs, were found to be satisfactory.
Dietary exposure estimates The FCS results revealed that over 1400 food items were being consumed by the Hong Kong population (FEHD 2010). A food mapping process was carried by mapping the TDS food items with food items captured by FCS in order to cover the whole diet of the Hong Kong population. The mean levels of the TDS food items were assigned to the mapped FCS food
items with an application of conversion factors taking reference to the differences in water content (FEHD 2011). To cite an example, scallop in TDS food was mapped to scallop and other bivalve in FCS. After food mapping for all 150 TDS food items, over 99% of the average diet of the population would be covered, but for the 71 TDS food items used for the testing of dioxins and dioxin-like PCBs about 24% of the average diet of the population was covered. Nevertheless, the remaining 76% of food was water, non-alcoholic beverages and food of plant origin which were not considered as significant sources of dioxins and dioxin-like PCBs. The dietary exposures were then estimated by combining the assigned levels of mapped FCS food items with their corresponding food consumption amounts. A weighting based on the population distribution by age and gender in the 2006 Population By-census was applied to adjust for bias arising from the age–gender quotas (FEHD 2010, 2011). The mean and 95th percentile of the exposure levels among the FCS respondents after weighting by age–gender are used to represent the dietary exposures of the average and the high consumer of the Hong Kong population, respectively. Dietary exposure estimation was performed with the aid of an in-house-developed webbased computer system, Exposure Assessment System (EASY), that takes food mapping and weighting of data into consideration. Results and discussion A total of 142 composite samples on two occasions were tested for dioxins and dioxin-like PCBs. All 142 composite samples were detected with at least one of the dioxin and dioxin-like PCB congeners, in which about two-thirds (66%) of the test results were found to be above the LODs of individual dioxin and dioxin-like PCB congeners. The non-detected results were treated according to the recommendation of the WHO on the evaluation of low-level contamination of food in the treatment for those nondetected results (WHO 1995). All non-detected results were assigned with levels at half the LOD for expressing their contents as well as estimating the dietary exposures. Table 1 shows the concentrations of dioxins and dioxin-like PCBs in different food groups. Among all the food groups, the group “Fish and seafood and their products” was found to contain the highest dioxin and dioxinlike PCB level (mean = 0.440 pg TEQ g−1), followed by the groups “Eggs and their products” (mean = 0.137 pg TEQ g−1), “Fats and oils” (mean = 0.0937 pg TEQ g−1), and “Meat, poultry and game and their products” (mean = 0.0909 pg TEQ g−1). Under the food group “Fish and seafood and their products”, the mean levels of dioxins and dioxin-like PCBs ranged from 0.0116 to 1.06 pg TEQ g−1. Mandarin fish was found to contain the highest level (mean = 1.06 pg TEQ g−1), followed by oyster
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Table 1. Dioxin and dioxin-like PCB contents (pg TEQ g−1) in food groups of the first Hong Kong Total Diet Study.
Food group Cereals and their products Meat, poultry and game and their products Eggs and their products Fish and seafood and their products Dairy products Fats and oils Beverages, non-alcoholic Mixed dishes Others
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Total
Number of composite samples
Percentage of the test results < LOD
24 24 6 38 10 4 6 22 8
45 23 16 20 57 33 58 40 53
142
34
Mean (pg TEQ g−1) [range]a 0.0211 0.0909 0.137 0.440 0.0208 0.0937 0.0110 0.0184 0.0135
[0.00701–0.0850] [0.0120–0.257] [0.0204–0.302] [0.00888–1.27] [0.00701–0.0717] [0.0109–0.282] [0.00701–0.0147] [0.00716–0.0388] [0.00771–0.0303]
a
Note: As fewer than 60% of the results are below the LODs, half of the LOD is used for all results less than the LOD when calculating the concentrations.
(mean = 0.926 pg TEQ g−1) and pomfret fish (mean = 0.885 pg TEQ g−1), in which they were also the top three items with the highest levels among all the 71 food items. The proportions of dioxins alone and dioxin-like PCBs were compared among the four food groups with the highest levels, and are shown in Table 2. Higher proportions of dioxin-like PCBs were found in two food groups, “Fish and seafood and their products” (58.9%) and “Fats and oils” (69.3%), while higher proportions of dioxin alone were found in other two groups, “Eggs and their products” (71.0%) and “Meat, poultry and game and their products” (62.3%). Although there were variations of proportions between dioxins alone and dioxin-like PCBs, it showed that both dioxins and dioxin-like PCBs would also contribute to our sources of exposure. The estimated mean dietary exposure to dioxins and dioxin-like PCBs of the Hong Kong population was 21.9 pg TEQ kg−1 bw month−1 (31.3% of the PTMI) and its 95th percentile was 59.7 pg TEQ kg−1 bw month−1 (85.2% of
the PTMI). Furthermore, 3.07% of the Hong Kong population was estimated to exceed the PTMI. For adult males and females (aged 20–84 years), the estimated mean dietary exposure values to dioxins and dioxin-like PCBs were 21.9 and 22.0 pg TEQ kg−1 bw month−1, respectively. Among the 12 age–gender groups, the estimated mean dietary exposures to dioxins and dioxin-like PCBs of the individual subgroups ranged from 17.8 pg TEQ kg−1 bw month−1 (males aged 20–29 years) to 26.3 pg TEQ kg−1 bw month−1 (males aged 60–69 years) and the 95th percentile ranged from 45.9 pg TEQ kg−1 bw month−1 (males aged 20–29 years) to 73.5 pg TEQ kg−1 bw month−1 (males aged 60–69 years) (Figure 1). Among the 12 age–gender groups, all the estimated mean dietary exposures were found below the PTMI (the highest contributed 37.5% of the PTMI), but the estimated 95th percentile dietary exposures of the following three subgroups, namely males aged 60–69 years (73.5 pg TEQ kg−1 bw month−1), females aged 60–69 years (72.7 pg TEQ kg−1 bw month−1), and females aged
Table 2. Proportions of dioxins and dioxin-like PCBs to the sum of dioxins and dioxin-like PCBs among the four food groups with the highest levels of the first Hong Kong Total Diet Study. Mean (pg TEQ g−1)a
Percentagec
Food group
Totalb
Dioxins alone
Dioxin-like PCBs
Dioxins alone
Dioxin-like PCBs
Fish and seafood and their products Eggs and their products Fats and oils Meat, poultry and game and their products
0.440 0.137 0.0937 0.0909
0.181 0.0973 0.0288 0.057
0.259 0.0398 0.0649 0.0343
41.1 71.0 30.7 62.3
58.9 29.0 69.3 37.7
Notes: aAs fewer than 60% of the results are below the LODs, half of the LOD is used for all results less than the LOD when calculating the concentrations. b Total is the sum of dioxins and dioxin-like PCBs. c Percentage is the percentage of dioxins alone or dioxin-like PCBs to the sum of dioxins and dioxin-like PCBs.
W.W.K. Wong et al. Dietary exposure (pg–1 TEQ kg–1 bw month–1)
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95th percentile
60 50 40 30 20 10
20
–
29
M
al e Fe 30 m al – e 30 39 M – a le 39 F 40 em al – e 40 49 M – 49 ale F 50 em al – e 50 59 M – 59 ale F 60 em al – e 60 69 M – 69 ale F 70 em al – e 70 84 M – a le 84 F 20 em al – e 20 84 M – 84 ale Fe m al e
0
– 20
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Average
PTMI of 70 pg–1 TEQ kg–1 bw month–1
70
29
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Age-gender groups
Figure 1. Mean and 95th percentile dietary exposures to dioxin and dioxin-like PCBs of the individual age–gender groups of the Hong Kong population of the first Hong Kong Total Diet Study.
70–84 years (73.1 pg TEQ kg−1 bw month−1), were found to be slightly exceeding the PTMI (which amounted to 105%, 104% and 104% of the PTMI, respectively). In addition, the estimated 95th percentile dietary exposure (69.5 pg TEQ kg−1 bw month−1) of females aged 30–39 years, who fall into the child-bearing age range, was close to the PTMI (99.3% of the PTMI). Therefore, the Hong Kong population was unlikely to experience major undesirable health effects of dioxins and dioxin-like PCBs. Although some age–gender groups at the 95th percentile exposures were found to be close to or slightly exceeding the PTMI, an intake above the PTMI in a certain period of time does not automatically mean that health is at risk provided that the average intake over a long period is not exceeded as PTMI is emphasised by lifetime exposure. The mean dietary exposures to dioxins and dioxin-like PCBs of the Hong Kong population by the TDS food groups and contribution of the total exposure are shown in Table 3. In our findings, the main dietary source of dioxins and dioxin-like PCBs was the group “Fish and seafood and their products” (61.9% of the total exposure), followed by the groups “Meat, poultry and game and their products” (20.0%) and “Mixed dishes” (6.95%). Similar findings were also revealed in other dietary exposure studies that aquatic food and meat are the major food contributors. However, dairy products only contributed to 1.28% of the total exposure, although it has been reported to be one of the major sources of exposure in the Western diet. It may be due to the difference in the consumption pattern of dairy products. In the food group “Fish and seafood and their products”, fish and fishery products were found to be the
Table 3. Mean dietary exposures (pg TEQ kg−1 bw month−1) to dioxins and dioxin-like PCBs of the Hong Kong population in food groups of the first Hong Kong Total Diet Study and their contribution of the total exposure.
Food group Cereals and their products Meat, poultry and game and their products Eggs and their products Fish and seafood and their products Dairy products Fats and oils Beverages, non-alcoholic Mixed dishes Others Totalb
Dietary exposure (pg TEQ kg−1 bw month−1)a
Percentage contribution of total exposure
1.08
4.92
4.39
20.0
0.297 13.6
1.35 61.9
0.280 0.157 0.584
1.28 0.714 2.66
1.52 0.0308
6.95 0.141
21.9
100
a
Notes: As fewer than 60% of results are below the LOD, half of the LOD is used for all results less than the LOD when calculating the exposure estimates. b Figures may not add up to the total due to rounding.
major sources of dioxins and dioxin-like PCBs (55.6% of the total exposure). About half of the exposure from fish (i.e. 25.0% of the total exposure) was contributed by the four fish species, namely grass carp (8.14% of total exposure), golden thread (6.25%), pomfret fish (5.96%) and mandarin fish (4.70%). Mandarin fish and pomfret fish were also found to contain the highest levels of dioxins and dioxin-like PCBs. The contribution of these two fish species together was about 10% of the total
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Table 4. Comparison of dietary exposures of dioxins and dioxin-like PCBs. Dietary exposure (pg TEQ kg−1 bw month−1) Average (years)
95th or 97.5th percentile
15.6 (aged 2 years and above)a,d
40.6 (aged 2 years and above) (95th percentile)a,d
21.9c 25.2e
59.7 (95th percentile)c
27 (adult)a,d
51 (adult) (97.5th percentile)a,d
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Places USA (TDS 2001–2004) (US Food and Drug Administration 2006) Australia (2004) (Food Standards Australia New Zealand 2004) Hong Kongf Japan (2009) (Ministry of Health, Labour and Welfare 2010) UK (TDS 2001) (Food Standard Agency of the UK 2003) China (TDS 2000) (Li et al. 2007) The Netherlands (2001) (Food Standards Australia New Zealand 2004) Finland (1991–1999) (EC 2000) Sweden (1999) (EC 2000)
18.2
a,b,c
4.5–28.8 (adult male)a,d 39e 55.5 (adult)a,d 56.1a,d
Notes: aWHO TEF 1998. b PCDD/PCDFs only. c Medium bound – assumed results reported as being below the LOD are at 0.5 LOD. d Upper bound – assumed results reported as being below the LOD are at the LOD. e Lower bound – assumed results reported as being below the LOD are zero. f Data from the current study.
exposure. In the food group “Meat, poultry and game and their products”, about two-thirds of the exposure from this food group was contributed by chicken and beef products (13.3% of the total exposure). The dietary exposures to dioxins and dioxin-like PCBs of the Hong Kong population were also compared with those obtained from other places, and are summarised in Table 4. However, direct comparison of the data has to be done with caution due to different experimental factors and considerations including the time the studies were carried out, research methodologies, methods of collection of consumption data, methods of contaminant analysis, methods of treating results below detection limits, and the difference of the TEF schemes applied.
Conclusion In summary, the estimated mean dietary exposure to dioxins and dioxin-like PCBs of the Hong Kong population was 21.9 pg TEQ kg−1 bw month−1 (31.3% of the PTMI) and its 95th percentile was 59.7 pg TEQ kg−1 bw month−1 (85.2% of the PTMI). Therefore, the Hong Kong population is unlikely to experience major undesirable health effects of dioxins and dioxin-like PCBs. Food of animal origin, particularly fish, meat and poultry, is the major source of exposure to dioxins and dioxin-like PCBs. Nevertheless, having considered their carcinogenic risks, efforts should be made to reduce the dietary exposure to dioxins and dioxin-like PCBs of the Hong Kong population.
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