Dietary Exposure to Dioxins, Polychlorinated Biphenyls, and Heavy

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Chapter 4

Dietary Exposure to Dioxins, Polychlorinated Biphenyls, and Heavy Metals in the Tokyo Metropolitan Area from 1999 to 2014 Takeo Sasamoto,*,1 Harunori Otani,1 Izumi Hirayama,1 Masaki Hayashi,1 Itoko Baba,1 Kenji Iida,1 Yasuhiro Tamura,1 Tetsuya Shindo,1 Ayana Yagisawa,2 Atsushi Murai,2 and Noriko Osugi2 1Department

of Food Chemistry, Tokyo Metropolitan Institute of Public Health, 3-24-1 Hyakunin-cho, Shinjuku-ku, Tokyo 169-0073, Japan 2Environmental Health and Sanitation Section, Health and Safety Division, the Bureau of Social Welfare and Public Health of the Tokyo Metropolitan Government, 2-8-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-8001, Japan *E-mail: [email protected]

Continuous surveillance of the dietary intake of dioxins, polychlorinated biphenyls (PCBs) and heavy metals in foods retailed in the metropolitan Tokyo area was performed from 1999 to 2014 using the total diet-market basket method based on food classification (14 groups) and data about food consumption in the Tokyo region, which were obtained from the National Health and Nutrition Survey in Japan. The daily intake of dioxins per kg of body weight for an average 50-kg adult body was 1.92 pg toxicity equivalency quantity (TEQ)/kg/day in 1999 and it decreased to 0.51 pg TEQ/kg/day in 2014. It is now estimated as being below 1 pg TEQ/kg/day in Tokyo. The daily intake of dioxins in fish and shellfish (group 10) accounted for more than 50% of total WHO-TEQs. In addition, more than 90% of the daily intake of dioxins came from fish and shellfish (group 10), meat and eggs (group 11), and milk and dairy products (group 12). The daily intake of PCBs was estimated as 0.038 –0.051 μg/kg/day, which is 0.76%–1.02% of the Japanese provisional acceptable daily intake (ADI). The fish and shellfish group made the highest contribution to the total dietary intake

© 2016 American Chemical Society


of PCBs. During the period of this study, the dietary intake of PCBs remained at the same level, or decreased slightly. The daily intake of methylmercury and mercury remained at a low value and was less than the tolerable weekly intake (TWI) established in Japan. The major sources of methylmercury and mercury intake were fish and shellfish (group 10). The daily intake of cadmium also remained at a low value and it was less than the TWI in Japan. The major sources of cadmium intake were rice and rice products (group 1). There was no specific source of lead intake.

Introduction The development of the chemical industry has brought significant benefits as well as creating chemicals that have harmful effects on humans and causing severe pollution of the environment. Among these chemicals, particular attention has been paid to hazardous chemical substances such as dioxins, polychlorinated biphenyls (PCBs) and heavy metals. Dioxins and PCBs were classified as persistent organic pollutants at the “Stockholm Convention on Persistent Organic Pollutants” in 2001. Dioxins, such as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like PCBs (dl-PCBs) are highly toxic environmental pollutants which are distributed worldwide and are found in foods (1–10). They have high toxicity and carcinogenicity, and cause various toxicological and biological responses typified by tumorigenicity, teratogenesis and thymic atrophy according to animal studies (11–13). PCDDs and PCDFs are produced as unwanted by-products in the flue gas from municipal solid waste and industrial waste incinerators, as well as via the synthesis of chlorinated compounds such as pentachlorophenol and chloronitrofen, which were used as herbicides on paddies (14). dl-PCBs are thought to originate from industrial PCB products such as electrical insulating oil, heat exchange fluids, and additives in paints, carbonless copy paper, sealants, and plastics. After the widespread environmental contamination by commercial PCBs was confirmed in the late 1960s, the production and use of PCBs in Japan were prohibited in 1972. However, the large-scale degradation of PCBs was not conducted in Japan until some firms recently started to chemically or physically treat their PCB waste. Due to their persistence and lipophilic characteristics, dioxins last a long time after entering the body. In the environment, dioxins tend to accumulate in the food chain, where the concentration of dioxins is higher for animals higher in the food chain. Humans are at the top of food chain, so human tissues contained higher levels of dioxins. PCBs have excellent physical properties including thermostability, insulating properties, and resistance to flames, oxidation, and acids and bases, so they have been used widely as heat transfer fluids, dielectric fluids, plasticizers, organic diluents, carbonless copy paper, and surface coatings. They have been 86


produced and used worldwide under various trade names such as Alochlor (USA), Chlophen (German), and Kanechlor (Japan). The cumulative total global industrial production and commercial applications of PCBs have been estimated at more than 1 million tons. However, a mass food poisoning event called Yusho occurred in Kyushu, Japan during 1968. Yusho was caused by the ingestion of a commercial brand of rice oil, which was contaminated by PCBs (15, 16). In addition, in 1979, a similar form of mass food poisoning, called Yucheng, occurred in central Taiwan because of the ingestion of cooking oil contaminated with PCBs (17). Due to their lipophilicity, PCBs are usually distributed and accumulated in adipose tissue, and they are excreted in breast milk and transferred through the placenta (18–21). PCBs have chronic and transgenerational toxicity, with carcinogenicity of PCBs being reported in several studies (22–26). In 2013, the International Agency for Research on Cancer (IARC) determined that PCBs are carcinogenic to humans (27). Properties such as lipophilicity and persistence mean that they will persist in the environment for a long time, after their release, where they are biomagnified in the food chain at a high level, and they can undergo long-range atmospheric transport (28–33). PCBs affect human health and the environment, so the use or production of PCBs is strictly banned or restricted. Heavy metals are generally defined as metals with a density higher than iron. Some heavy metals, especially mercury, cadmium, and lead are potentially hazardous due to their intrinsic or selective toxicity, particularly in environmental contexts. Mercury is a liquid metal under normal pressure and temperature (34). The most famous form of mercury poisoning was the Minamata disease at Minamata Bay, Kumamoto, Japan in the 1960’s (35, 36), which was caused by methylmercury in wastewater from a chemical plant. The wastewater containing methylmercury polluted the fish in Minamata Bay and people living in the Minamata Bay area were then poisoned by these polluted fish. Inorganic mercury in the air or water reaches the sea and forms methylmercury. Subsequently, plankton may capture the methylmercury in the seawater and methylmercury may enter the food chain. Thus, seafood is the major source of exposure to methylmercury for many people. Methylmercury has a high affinity for the mercapto group. Thus, it can bind to amino acids such as cysteine. The complex of cysteine-methylmercury is absorbed and transported to the brain via the neutral amino acid transport system. It moves to the brain without protection from the blood-brain barrier and to unborn children in mothers through their placenta. It should be noted that there were none or only mild symptoms in the mothers who ate the polluted fish, but there were severe symptoms such as cerebral palsy in newborn babies, even though they had not consumed any seafood. Thus, methylmercury may migrate to unborn children. Cadmium is known to be a causal substance of bone and joint disease. Itai-itai disease is a well-known health problem, which was caused by cadmium in the lower reaches of the Jindu River, Toyama, Japan during the 1910’s (37). The river system and agricultural soil around this river were polluted with wastewater and sludge from a mine. Thus, the cause of this disease was polluted drinking water and farm products, such as rice, affected by the polluted water. The name of this disease, “Itai-itai disease”, was coined by locals to refer to the severe pain 87


(Japanese: itai) victims felt in their spines and joints. The most severe cases of this disease included extreme osteoporosis and osteomalacia. The severely affected patients could readily fracture their bones even when they coughed, laughed, and turned over in bed, and they experienced severe pain. The relationship between humans and lead began a long time ago. Lead can be easily processed and it is inexpensive (38). Thus, lead is used widely in solder, lead pipes, and lead-acid batteries. In addition, lead is dense and stable so it does not react to radiation; thus, lead is suitable for use as a weight and radiation protection. Lead is also included in pigments. Fortunately severe damage to human health has not been caused by lead in Japan. However, many women, such as Geisha and Kabuki actors used a traditional white face powder with lead in Japan, and some of them were poisoned. The ingestion of contaminated food is the major route for human exposure to these compounds, which accounts for >90% of the cases of exposure, whereas inhalation and dermal contact account for the rest (39, 40). Therefore, estimating the daily dietary intake of these compounds is highly significant for risk evaluations. Thus, the Tokyo Metropolitan Government has performed continuous surveillance to estimate the dietary intake of these compounds in a total diet study (TDS). The TDS method (also known as the market basket study method) was developed in the USA in 1961 and it is recognized as a classic method for measuring human exposure to various contaminants, including pesticides, industrial chemicals and radionuclides in foods (41, 42). We have employed this approach to determine the levels of dioxins, PCBs, and heavy metals in food. In this study, we report the results of monitoring in the metropolitan Tokyo area from 1999 to 2014 using the TDS method based on food classification and data regarding food consumption in the Tokyo region, which were obtained from the National Health and Nutrition Survey in Japan.

Materials and Methods Sample Preparation The planning of TDS sampling was based on the official food classification (14 groups) and the previous year’s data about food consumption in the Tokyo region, which were obtained from the National Health and Nutrition Survey in Japan by The Ministry of Health, Labor, and Welfare of Japan (1998 –2013). Table 1 shows the classification of 14 food groups and the contents of foodstuff samples in 2013. Every year, more than 20–30 individual foods were bought from supermarkets, department stores and retail stores in Tokyo, and cooked or prepared by each group in the typical manner before consumption. In particular, we prepared samples from over 50 species in group 10 (fish and shellfish). Finally, we used over 300 individual foods each year to prepare samples. All of the group samples were adequately homogenized, and then frozen at -40°C until analysis.

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89


Table 1. Classification of 14 food groups and the contents of foodstuff samples No.

Number of foodstuffsin 2014

Food group

Examples

1

Rice and rice products

9

Rice, Glutinous rice cake

2

Cereals, seeds and potatoes

31

Wheat flour, Bread, Potato

3

Sugars and confectioneries

27

Sugar, Honey, Cookie, Cake

4

Fats and oils

12

Butter, Mayonnaise, Canola oil

5

Pulses

20

Tofu (Soybean curd), Miso

6

Fruits

16

Orange, Apple, Grape, Banana

7

Green vegetables

16

Tomato, Spinach, Carrot, Pumpkin

8

Other vegetables, mushrooms and seaweeds

33

Cabbage, Onion, Japanese radish

9

Seasoning and beverages

36

Soy sauce, Beer, Coffee, Green tea

10

Fish and shellfish

52

Sardine, Tuna, Eel, Mackerel, Shrimp

11

Meat and eggs

30

Beef, Pork, Chicken, Hen’s egg

12

Milk and dairy products

17

Cow milk, Yogurt, Cheese

13

Other foods (prepared foods)

12

Curry powder

14

Drinking water

1

Tap water

Total

312

Chemical Analysis


Dioxins All of the solvents used for dioxin analysis were analytical grade (Wako Pure Chemicals Industries, Osaka, Japan). Native and 13C12-PCDDs, PCDFs, and dl-PCBs were purchased as authentic standards from Wellington Laboratories (Guelph, Ontario, Canada). The methods for extracting and cleaning up of the samples followed the tentative guidelines for the analysis of dioxins in foods in Japan (2008). All of the samples were spiked with 17 types of 13C12-PCDDs and PCDFs, four types of 13C12-non-ortho-PCBs, and eight types of 13C12-mono-ortho-PCBs before the initial extraction. Food group Nos. 1, 2, 3, 6, 7, 8, and 9 were extracted three times with acetone:n-hexane (1:1). Food group Nos. 4, 5, 10, 11, 12, and 13 were digested with 1 M aqueous KOH for 2h at room temperature. The alkaline hydrolysates were then extracted three times with n-hexane. Drinking water (food group No. 14) was extracted three times with dichloromethane. The extract was concentrated to about 10 mL and up to 100 mL with n-hexane. The hexane extract was cleaned 5–10 times with 25 mL of sulfuric acid, rinsed with distilled water, and then dehydrated with anhydrous sodium sulfate. The organic layer was concentrated to about 3 mL. Sample clean-up was performed using a multi-layer silica gel column obtained from Sigma-Aldrich (St. Louis, Missouri, USA), and a reverse column with active carbon dispersed-silica gel obtained from Kanto Chemical Co., Inc. (Tokyo, Japan). HRGC-HRMS was performed using a JEOL (Tokyo, Japan) JMS-800D coupled to an Agilent Technologies 7890A gas chromatograph (Santa Clara, CA, USA), and a Micromass (Manchester, UK) Autospec Ultima coupled to an Agilent Technologies 6890 gas chromatograph. The analysis of PCDDs and PCDFs were performed using a SGE (Melbourne, Victoria, Australia) BPX-DXN capillary column (60 m × 0.25 mm i.d.). The analysis of dl-PCBs was performed using a SGE HT-8 capillary column (50 m × 0.22 mm i.d., 0.25 μm film thickness). The temperatures of the interface and ion source were both 270°C, with an electron energy of 35 eV and trap current of 500 μA.The mass spectrometer was operated at a resolution of 10,000. Selected ion monitoring was employed using the two most intense ions from the molecular ion cluster for each homologue. Data processing was performed using DIOK and VG OPUS software for automatic peak area measurement and to calculate the mass of each compound present. The limits of detection (LOD) for PCDDs, PCDFs, and dl-PCBs in this study are given in Table 2. The non-detected outcomes were set at zero. The 2,3,7,8TCDD toxicity equivalency quantity (TEQ) of the dioxin analogues in the analyzed samples was calculated based the toxic equivalency factor (TEF) re-evaluated by the WHO in 2005 (43).

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Table 2. Limits of detection for PCDDs, PCDFs, and dl-PCBs in each food group (pg/g)


Food groups

PCDDs, PCDFs

dl-PCBs

Te, Pe, Hx, HpCDD/DF

OCDD/DF

Group No. 113

0.01

0.02

0.01

Group No. 14

0.0001

0.0002

0.0001

PCBs Kanechlor mixture solutions (KC-300, -400, -500, and -600) were purchased as PCB standards from GL Science (Tokyo, Japan). Potassium hydroxide, n-hexane, anhydrous sodium sulfate, and Florisil were obtained from Wako Pure Chemicals Industries (Osaka, Japan). Ethanol was purchased from Kanto Chemical Co., Inc. (Tokyo, Japan). The PCB samples were prepared according to the Standard Methods of Analysis for Hygienic Chemists – with Commentary – 2000 (44). First, 5 g of each homogenized sample was weighed and 1 mol / L of a potassium hydroxide solution in ethanol was added to the sample before heating at reflux for 60 min in a boiling water bath. After cooling, the mixture was extracted two times with n-hexane before the combined organic layer was washed three times with 2% sodium chloride solution or distilled water, and then dried with anhydrous sodium sulfate. The organic layer was applied to a column containing 3 g of Florisil (lower layer) and 2 g of anhydrous sodium sulfate (upper layer), and eluted with 50 mL of n-hexane. After cleaning up, the eluate was evaporated to 3 mL and injected into the GC-ECD system. GC-ECD was performed using a Shimadzu GC-2010 (Kyoto, Japan). PCBs were analyzed using a Shimadzu GLC (Tokyo, Japan) Rtx-5 capillary column (30 m × 0.32 mm i.d., 0.5 μm film thickness). The detection limit for the PCBs in this study was 1 ng/g. The non-detected outcomes were set as one-half of the quantification limit.

Heavy Metals The method used for analyzing the total mercury content was “Gold amalgam collecting, heat-vaporization, and cold-vapor atomic absorption spectroscopy” from the “Standard methods of analysis in food safety regulation 2005” (45). The standard solution (for chemical analysis grade) was obtained from Kanto Chemical Co., Inc. We used certified reference materials (CRM) for validation (CRM 7402-a: cod fish powder), which were obtained from the National Metrology Institute of Japan, AIST (Ibaraki, Japan). About 0.1 g of each sample was weighed into a boat that formed part of the direct thermal decomposition mercury analyzer, where we used an MA-3000 (2011–2014) and an SP-3D (2005–2011) from Nippon Instruments Corporation (Tokyo, Japan). In this method, the LOD for total mercury was 0.001μg/g. The method used for analyzing methylmercury 91


by GC-ECD was “Provisional regulation value for mercury in fish and shellfish,” by The Ministry of Health, Labor, and Welfare of Japan, Notification No.99 (1973) (46). The standard solution of methylmercury chloride was obtained from GL Sciences Inc. (Tokyo, Japan). About 3 g of each sample was weighed, before adding 9 mol/L of hydrochloric acid and benzene to the sample, which was then shaken for 10 min at room temperature. Cysteine-acetate liquid was added to the upper layer and shaken for 5 min. Next, the lower layer was mixed with hydrochloric acid and benzene, and shaken for 10 min. The upper layer was injected into the GC-ECD system. The GC-ECD system comprised a GC-14A (2005–2011), and a GC-2014 (2012–2014) from Shimadzu Corporation (Kyoto, Japan). Methylmercury was analyzed using a Shimadzu GLC (Tokyo, Japan) packed column (1.1 m × 3.2 mm i.d., Chromosorb W, 10% Thermon-HG). In this study, the LOD for methylmercury was 0.001μg/g. The methods used for analyzing cadmium and lead by ICP-MS came from the “Methods of Analysis in Health Science 2005” (47). The cadmium standard solution (chemical analysis grade) was obtained from Kanto Chemical Co. Inc. The lead standard solution was obtained from Wako Pure Chemical Industries, Ltd. (Osaka, Japan). We used CRM materials for validation (CRM 7501-a and 7502-a: white rice flour), which were obtained from the National Metrology Institute of Japan, AIST (Ibaraki, Japan). About 0.5 g of each sample was weighed, before adding nitric acid and hydrogen peroxide to the sample, which was thermally decomposed in a microwave (MultiWave3000, PerkinElmer, Inc., USA). The liquid from the sample was made up to 50 mL with hyper pure water and analyzed by ICP-MS using an Agilent 7700x ICP-MS system from Agilent Technologies, Inc. (USA). In this method, the LOD for cadmium and lead was 0.001μg/g.

Results and Discussion Dioxins Table 3 shows the yearly changes in the daily intake of dioxins from each food group. Analyses of dioxins were performed every year from 1999 to 2010, and then biyearly after 2010. The daily intake of dioxins per kg of body weight for an average 50-kg adult body based on the WHO-TEF (2005) was 1.92 pg TEQ/kg/day in 1999, 1.65 pg TEQ/kg/day in 2000, 1.08 pg TEQ/kg/day in 2001, 1.39 pg TEQ/ kg/day in 2002, 1.36 pg TEQ/kg/day in 2003, 1.12 pg TEQ/kg/day in 2004, 1.19 pg TEQ/kg/day in 2005, 1.11 pg TEQ/kg/day in 2006, 1.06 pg TEQ/kg/day in 2007, 1.15 pg TEQ/kg/day in 2008, 0.69 pg TEQ/kg/day in 2010, 0.75 pg TEQ/kg/day in 2012, and 0.51 pg TEQ/kg/day in 2014. The total daily intake tended to decrease during the first three years, before stabilizing for the seven years between 2001 and 2008. The daily intake of dioxins was more than 1.0 pg TEQ/kg/day until 2008, but it then decreased to less than 1.0 pg TEQ/kg/day after 2010. We estimate that the total dietary intake of dioxins in the Tokyo area is currently about 0.5 pg TEQ/kg/day. These total intake values are below the TDI of 4 pg TEQ/kg/day set by the Environmental Agency and The Ministry of Health, Labor, and Welfare of Japan. In addition, they satisfy the ultimate goal of reducing human intake 92


levels to below 1 pg TEQ/kg/day, which was set by the WHO in 2010. The values are similar to or lower than those found in previous studies in Japan and in other countries (1, 3, 5–10). Among the 14 food groups, the highest contribution to the total intake came from fish and shellfish (group 10) in each year, where the contribution from this group accounted for over 70% of the total, except in 2001. Meat and eggs (group 11), and milk and dairy products (group 12) made the next- highest contributions. The summed TEQ for these three groups accounted for 92.1%–98.4% of the total intake. By contrast, green vegetables (group 7) accounted for 1 pg TEQ/day or more during the first three years, but this declined significantly each year from 2002 to 2014. Figure 1 shows the yearly changes in the daily dietary intake of PCDDs, PCDFs, and dl-PCBs as TEF (2005). The daily intake of PCDDs and PCDFs decreased rapidly in 2001, but the intake of dl-PCBs did not decrease significantly until 2010. In Japan, the “Law Consisting of Special Measures against Dioxins” was enacted in 1999, which requires that anybody who releases gas emissions or effluents should not release gas emissions or effluents with dioxin levels that fail to comply with the emission standards. Therefore, the emission of PCDDs and PCDFs from incinerators is thought to have decreased since this law was enacted. By contrast, dl-PCBs are thought to originate from electrical insulating oil and heat exchange fluid with the exception of a few congeners. After widespread environmental contamination by commercial PCBs was confirmed in Japan during the late 1960s, the production and use of PCB were prohibited in 1972. However, the large-scale destruction of PCBs was not conducted in Japan until some firms recently started to chemically or physically treat their PCB waste after 2001 due to the “Law Concerning Special Measures against PCB Waste.” The treatment of PCBs is currently in progress, but large amounts of PCB-containing materials remain, which are stored in depositories and the environmental leakage of PCBs will persist for a long period. Therefore, the daily dietary intake of dl-PCBs decreased only after 2010, so they lag behind those in PCDDs and PCDFs. Japan is one of the world’s leading consumers of fish and shellfish. It has been reported that Japanese retail fish contain an average of 1.6 pg TEQ/g dioxins and that about 60% of the dietary intake of dioxins is likely to come from the intake of fish and shellfish (1, 2). In our study, the fish and shellfish group made an even higher contribution to the total dietary intake of dioxins than reported previously. Thus, particular importance should be attached to the levels of dlPCBs when estimating the total dietary intake of dioxins in the future, especially in nations that are major consumers of fish and shellfish. The fish catches in the seas close to Japan have decreased remarkably in recent years, so Japan has begun to import many marine products. Thus, it will be necessary to determine the residue levels of dioxins in imported fish and shellfish.

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Table 3. Daily dietary intake of dioxins (pg-TEQ/kg body weight/day)a,b

1999

2000

2001

2002

2003

2004

2005

2006

1

0.0079

0.00090

0.015

0.000040

0.000013

0.000038

0.000019

0.000031

2

0.017

0.013

0.0053

0.016

0.0063

0.0064

0.0051

0.0099

0.0058

0.00062

3

0.0098

0.021

0.015

0.0088

0.012

0.0093

0.0045

0.012

0.0077

4

0.010

0.0052

0.0094

0.014

0.017

0.0040

0.011

0.011

5

0.00025

0.000089

0.0015

0.0015

0.00019

0.00025

0.00022

0.000082

6

0.0012

0.00031

0.000037

0.0000015 0.0000015 0.0000014

0.0000048 0.000047

2007

2008

2010

2012

2014

0.000066

0.000010

0.00036

0.00025

0.0015

0.0043

0.0040

0.0021

0.0036

0.0077

0.0064

0.0042

0.0060

0.0014

0.00061

0.00010

0.000055

0.00047

0.000029

0.0000080 0.000034 0.0000052

0.0000083 0.000012 0.0000021

0.0000064 0.000066

7

0.051

0.027

0.029

0.0053

0.0043

0.0052

0.0025

0.000061

0.000072

0.00052

0.00012

0.00022

0.00037

8

0.013

0.021

0.0050

0.0014

0.0064

0.010

0.0091

0.0052

0.0053

0.0036

0.0020

0.0017

0.0012

9

0.00011

0.00065

0.00012

0.000035

0.00062

0.00029

0.00014

0.00032

0.00017

0.00019

0.000029

0

0.000014

10

1.5

1.2

0.58

1.1

1.1

0.88

0.98

0.79

0.82

0.92

0.55

0.53

0.45

11

0.15

0.22

0.34

0.17

0.12

0.15

0.15

0.24

0.20

0.19

0.091

0.18

0.043

12

0.14

0.13

0.073

0.12

0.050

0.042

0.027

0.033

0.021

0.015

0.025

0.024

0.0063

0.0055

0.0092

0.0043

0.0045

0.0083

0.012

0.0022

0.0028

0.0026

0.0053

0.0016

13 14 Total a

Year

No. of Foodgroupc

0.00000088 0.0000079 0.0000021 0.0000017 0.0000015 0.00000014 0.00036 1.92

1.65

Values calculated at ND = 0. shown in Table 1.

1.08 b

1.39

1.36

1.12

1.19

0.00000011 0.00036 1.11

0.024 0.00036

1.06

Daily intake of dioxins per kg of body weight for an average 50-kg adult body.

1.15 c

0.00000055 0.00025 0.69

0.75

0.0021 0.0000053 0.51

The classification of 14 food groups is


Figure 1. Dietary daily intakes of PCDDs, PCDFs and dl-PCBs as TEFs (2005) in the Tokyo metropolitan area from 1999 to 2014 (pg TEQ/kg body weight/day). Values calculated at 1/2 of limits of detection (LOD). Daily intake of dioxins per kg of body weight for an average 50-kg adult body.

In conclusion, the results of the current study indicate that the recent total intake value of dioxins in Tokyo has reached the ultimate goal of reducing human intake levels below 1 pg TEQ/kg/day, which was set by the WHO. The contribution of the fish and shellfish ratio to the total intake of dioxins was over 70%, but we do not have to avoid eating fish. Indeed, it is important to have a balanced diet from a nutritional standpoint. We should promote the appropriate disposal of PCBcontaining materials with continuous surveillance.

PCBs PCBs are stable compounds and they are considered a problem due to their persistence in the environment. In Japan, the production of PCBs was banned in 1972, and possession or discarding of PCBs is strictly regulated in accordance with the “Act on Special Measures concerning Promotion of Proper Treatment of PCB Wastes” enacted in 2001. The levels of PCBs in food are regulated by the provisional regulation value for PCBs. Table 4 shows the yearly changes in the daily intake of PCBs.

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Table 4. Dietary daily intake of PCBs (μg/kg body weight/day)a,b

a

Year

No. of Food groupc

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

1

0.0049

0.0051

0.0048

0.0046

0.0051

0.0049

0.0048

0.0056

0.0054

0.0054

2

0.0037

0.0039

0.0035

0.0035

0.0042

0.0039

0.0038

0.0039

0.0032

0.0034

3

0.00043

0.00045

0.00049

0.00046

0.00046

0.00050

0.00046

0.00049

0.00049

0.00056

4

0.00020

0.00020

0.00020

0.00019

0.00018

0.00018

0.00019

0.00019

0.00018

0.00018

5

0.00069

0.00071

0.00068

0.00068

0.00066

0.00060

0.00060

0.00060

0.00062

0.00071

6

0.0013

0.0013

0.0013

0.0011

0.0011

0.0012

0.0010

0.0010

0.0011

0.0012

7

0.0010

0.0010

0.0011

0.0013

0.00093

0.00088

0.00076

0.00080

0.00088

0.0010

8

0.0022

0.0025

0.0027

0.0033

0.0023

0.0028

0.0024

0.0026

0.0039

0.0030

9

0.0067

0.0067

0.0067

0.0067

0.0066

0.0069

0.0066

0.0066

0.0070

0.0077

10

0.011

0.011

0.015

0.020

0.021

0.011

0.012

0.0088

0.010

0.0059

11

0.0012

0.0012

0.0015

0.0014

0.0011

0.0013

0.0014

0.0014

0.0013

0.0014

12

0.0016

0.0016

0.0016

0.0014

0.0013

0.0013

0.0012

0.0012

0.0013

0.0014

13

0.000069

0.000078

0.000080

0.000084

0.000068

0.00012

0.00012

0.000060

0.000060

0.000088

14

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

Total

0.041

0.042

0.046

0.051

0.051

0.042

0.042

0.039

0.042

0.038

Values calculated at 1/2 of limits of detection (LOD). of 14 food groups is shown in Table 1.

b


c

The classification

97


Table 5. Daily dietary intake of total mercury (μg/kg body weight/day)a,b

a

Year

No. of Food groupc

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

1

0.0049

0.0051

0.0048

0.0046

0.0051

0.0049

0.0048

0.0056

0.0054

0.0054

2

0.0037

0.0039

0.0035

0.0035

0.0042

0.0039

0.0038

0.0039

0.0032

0.0034

3

0.00043

0.00045

0.00049

0.00046

0.00046

0.00050

0.00046

0.00049

0.00049

0.00056

4

0.00020

0.00020

0.00020

0.00019

0.00018

0.00018

0.00019

0.00019

0.00018

0.00018

5

0.0027

0.00071

0.00068

0.00068

0.00066

0.00060

0.00060

0.00060

0.00062

0.00071

6

0.0013

0.0013

0.0013

0.0011

0.0011

0.0012

0.0010

0.0010

0.0011

0.0012

7

0.00095

0.00098

0.0011

0.0013

0.00093

0.00088

0.00076

0.00080

0.00088

0.0010

8

0.0044

0.0025

0.0027

0.0033

0.0023

0.0028

0.0024

0.0026

0.0019

0.0030

9

0.013

0.0067

0.0067

0.0067

0.0066

0.0069

0.0066

0.0066

0.0070

0.0077

10

0.13

0.16

0.15

0.18

0.17

0.20

0.17

0.15

0.18

0.16

11

0.0047

0.0012

0.0015

0.0014

0.011

0.013

0.0084

0.0014

0.0013

0.0085

12

0.0031

0.0016

0.0016

0.0014

0.0013

0.0013

0.0012

0.0012

0.0013

0.0014

13

0.000069

0.000078

0.000080

0.000084

0.000068

0.000060

0.000060

0.000060

0.000060

0.000088

14

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

Total

0.18

0.20

0.18

0.21

0.21

0.24

0.20

0.18

0.21

0.20


b


c

The classification

98


Table 6. Daily dietary intake of methylmercury (μg/kg body weight/day)a,b

a

Year

No. of Food groupc

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

1

0.0049

0.0051

0.0048

0.0046

0.0051

0.0049

0.0048

0.0056

0.0054

0.0054

2

0.0037

0.0039

0.0035

0.0035

0.0042

0.0039

0.0038

0.0039

0.0032

0.0034

3

0.00043

0.00045

0.00049

0.00046

0.00046

0.00050

0.00046

0.00049

0.00049

0.00056

4

0.00020

0.00020

0.00020

0.00019

0.00018

0.00018

0.00019

0.00019

0.00018

0.00018

5

0.00069

0.00071

0.00068

0.00068

0.00066

0.00060

0.00060

0.00060

0.00062

0.00071

6

0.0013

0.0013

0.0013

0.0011

0.0011

0.0012

0.0010

0.0010

0.0011

0.0012

7

0.0010

0.0010

0.0011

0.0013

0.00093

0.00088

0.00076

0.00080

0.00088

0.0010

8

0.0022

0.0025

0.0027

0.0033

0.0023

0.0028

0.0024

0.0026

0.0019

0.0030

9

0.0067

0.0067

0.0067

0.0067

0.0066

0.0069

0.0066

0.0066

0.0070

0.0077

10

0.12

0.14

0.15

0.14

0.16

0.12

0.096

0.14

0.13

0.13

11

0.0047

0.0012

0.0015

0.0014

0.0086

0.013

0.011

0.0014

0.0013

0.0057

12

0.0016

0.0016

0.0016

0.0014

0.0013

0.0013

0.0012

0.0012

0.0013

0.0014

13

0.000069

0.000078

0.000080

0.000084

0.000068

0.000060

0.000060

0.000060

0.000060

0.000088

14

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

Total

0.15

0.17

0.18

0.17

0.19

0.16

0.14

0.17

0.16

0.16


b


c

The classification

99


Table 7. Daily dietary intake of cadmium (μg/kg body weight/day)a,b

a

Year

No. of Food groupc

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

1

0.20

0.092

0.16

0.14

0.091

0.078

0.12

0.18

0.19

0.076

2

0.073

0.063

0.078

0.070

0.084

0.070

0.053

0.055

0.052

0.047

3

0.012

0.010

0.010

0.0064

0.0074

0.0060

0.0055

0.0069

0.0059

0.011

4

0.0010

0.0016

0.00079

0.00074

0.00073

0.00037

0.00019

0.00038

0.00074

0.00035

5

0.026

0.023

0.033

0.023

0.017

0.022

0.030

0.026

0.016

0.017

6

0.0067

0.0080

0.0080

0.0011

0.0023

0.0012

0.0020

0.0020

0.0045

0.0024

7

0.025

0.020

0.025

0.020

0.030

0.028

0.011

0.014

0.018

0.023

8

0.062

0.074

0.14

0.12

0.10

0.056

0.083

0.095

0.070

0.12

9

0.033

0.027

0.040

0.013

0.027

0.014

0.013

0.026

0.028

0.031

10

0.020

0.024

0.026

0.015

0.021

0.041

0.025

0.019

0.018

0.012

11

0.0059

0.0048

0.0088

0.0086

0.0086

0.0026

0.0014

0.0014

0.0013

0.0028

12

0.0078

0.0031

0.0031

0.0028

0.0052

0.0025

0.0012

0.0012

0.0013

0.0014

13

0.0014

0.0014

0.0019

0.0012

0.0018

0.0007

0.0010

0.0012

0.00048

0.0011

14

0.030

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

Total

0.50

0.36

0.54

0.43

0.40

0.33

0.35

0.44

0.42

0.35


b


c

The classification

100


Table 8. Daily dietary intake of lead (μg/kg body weight/day)a,b

a

Year

No. of Food groupc

2006

2007

2008

2009

2010

2011

2012

2013

2014

1

0.0051

0.0048

0.019

0.020

0.0098

0.048

0.068

0.075

0.076

2

0.0039

0.0035

0.0070

0.051

0.047

0.053

0.062

0.032

0.0034

3

0.0089

0.015

0.0074

0.020

0.0091

0.019

0.010

0.019

0.012

4

0.00020

0.0043

0.00074

0.00018

0.00037

0.0023

0.00076

0.0040

0.0011

5

0.00071

0.0054

0.0041

0.0040

0.0060

0.011

0.0072

0.0074

0.0057

6

0.0013

0.0013

0.011

0.014

0.0047

0.010

0.0010

0.011

0.0048

7

0.00098

0.0045

0.0013

0.011

0.014

0.011

0.0032

0.0088

0.0062

8

0.054

0.059

0.052

0.064

0.039

0.088

0.037

0.031

0.024

9

0.093

0.013

0.013

0.053

0.042

0.079

0.026

0.014

0.031

10

0.013

0.015

0.014

0.016

0.015

0.018

0.011

0.015

0.0059

11

0.031

0.015

0.0086

0.011

0.011

0.0084

0.0014

0.011

0.0057

12

0.044

0.044

0.0084

0.010

0.0076

0.0050

0.0075

0.018

0.0028

13

0.0014

0.0046

0.0030

0.0027

0.0024

0.0019

0.0023

0.0011

0.0011

14

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

0.0060

Total

0.26

0.19

0.16

0.28

0.21

0.36

0.24

0.25

0.19


b


c

The classification


In this study, the fish and shellfish group made the highest contribution to the total dietary intake of PCBs, where the daily intake of PCBs was estimated at 0.038–0.051 μg/kg·bw/day, which is 0.76%–1.02% of the Japanese provisional acceptable daily intake (5 μg/kg·bw/day). Some previous studies have reported the dietary intake of PCBs. In the “Airborne Exposure to Semi-volatile Organic Pollutants” study in North America, the dietary exposure to 40 congeners of PCBs was 65.6–108.0 μg/year, and the main dietary sources of PCBs were meat and dairy (48). In Northern Italy, the daily intake of PCBs was 0.26 μg/person/day, and the major contributors were bread, cereals and potatoes (49). The major contributors to the intake of PCBs differed in these studies, which is due to the diverse dietary habits of various countries. Japan is a major consumer of seafood, and thus fish and shellfish make greater contributions to the intake of PCBs. The Asian area has similar dietary habits, so most of the dietary intake of PCBs is contributed by aquatic foods (50, 51). Throughout the present study, the dietary intake of PCBs remained at the same level or declined slightly. However, we cannot conclude that the PCB levels are decreasing in food or in the environment. Therefore, the monitoring of PCBs in foodstuffs should be continued. Heavy Metals Total mercury and methylmercury were measured from 2005 to 2014 (Tables 5, 6). Total mercury was detected in six groups of the food samples collected in 2005, and two groups collected from 2009–2011 and in 2014. In 2006, 2007, 2008, 2012 and 2013, it was only detected in fish and shellfish (group 10). However, methylmercury was detected in group 10 every year. In addition, it was also detected in meat and eggs (group 11) in 2005, 2009–2011 and 2014. The contribution of group 10 to the daily intake of mercury was over 80% and that for methylmercury was over 90% throughout the investigation period. The daily intake of mercury as units per body weight was in the range of 0.18–0.24 μg/kg·bw/day. The minimum value of 0.18 μg/kg·bw/day was obtained in 2005, 2007, and 2012, and the maximum value of 0.24 was obtained in 2010. The daily intake of methylmercury was in the range of 0.14 to 0.19 μg/kg·bw/day. The minimum value of 0.14 μg/kg·bw/day was obtained in 2011 and the maximum value of 0.19 μg/kg·bw/day was obtained in 2009. The non-detected outcomes were set as 1/2 of LOD. The same evaluation method was used for the other heavy metals described hereafter. The daily intakes of methylmercury and mercury remained at low values and they were less than the tolerable weekly intake (TWI) (2 μg = 0.286 μg/kg·bw/day) determined by the Ministry of Health, Labor, and Welfare of Japan (52). The major source of methylmercury and mercury intake was group 10, which is due to the consumption of high amounts of fish and shellfish in Japan, so methylmercury has accumulated in the food chain. Japan regulated methylmercury based on a provisional regulation. In addition, Japan issued “Advice for Pregnant Women on Fish Consumption and Mercury” (53) because methylmercury can affect unborn babies. However, seafood is a high-quality protein source and includes beneficial components such as DHA 101


and EPA. Therefore, seafood is recommended as part of a balanced diet, thereby avoiding the risk of exclusively eating specific foods. Cadmium was measured from 2005 to 2014 (Table 7). Cadmium was detected in all the food groups, except for drinking water. The cadmium concentrations were highest in the group comprising rice and rice products (group 1), and the group of other vegetables, mushrooms and seaweed (group 8), throughout the investigation period, except for 2010 and 2011. In 2010 and 2011, the cadmium concentrations were highest in group 10 and pulses (group 5), respectively. The contributions of groups 1, 2, and 8 to the cadmium intake ranged from 22%–48%, 13%–22% and 15%–35% respectively. In addition, the total contribution of these groups to the cadmium intake was over 60%. The daily intake of cadmium ranged between 0.33 and 0.54 μg/kg·bw/day. The minimum value of 0.33 μg/kg·bw/day was obtained in 2010 and the maximum value of 0.54 μg/kg·bw/day was obtained in 2007. Cadmium is widespread in soil and minerals, so it was detected in all of the food groups except for drinking water. The daily intake of cadmium also remained at a low level and it was less than the TWI (7 μg/kg·bw/day = 1 μg/kg·bw/ day), according to the reference value reported previously (54). The major source of cadmium was “rice and rice products” because the staple food in Japan is rice (55). The daily intake of cadmium was 46 μg/person in the 1970’s but it decreased to 22.3 μg/person in 2005 because the consumption of rice has decreased in Japan. Lead was measured from 2006 to 2014 (Table 8). Lead was detected in all of the food groups, except for drinking water. The lead concentrations were highest in sugars and confectioneries (group 3), and prepared foods (group 13) throughout the investigation period, except in 2006, when they were highest in group 11. The highest contributors to the lead intake varied among years. For example, the highest contributors were seasoning and beverages (group 9) (38%), group 8 (22%), and milk and dairy products (group 12) (18%) in 2006, but were group 1 (43%), group 9 (17%), and group 8 (14%) in 2014. The daily intake of lead ranged from 0.16 and 0.36 μg/kg·bw/day, where the minimum value of 0.16 μg/kg·bw/day and the minimum value of 0.36 μg/kg·bw/day were obtained in 2008 and 2011, respectively. There was no specific source of lead intake. The daily intake of lead was similar to that found in a previous study (56), and was less than the provisional TWI (PTWI) (25 μg/kg·bw/week = 3.57 μg/kg·bw/day) defined in 1986 (57). However, the PTWI for lead was removed in 2010 (58).

Acknowledgments This study was organized by the Bureau of Social Welfare and Public Health of the Tokyo Metropolitan Government. The authors gratefully acknowledge and thank all of the study participants.

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