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Recent survey and effects of cooking processes on levels of PCDDs, PCDFs and Co-PCBs in leafy vegetables in Japan
Chemosphere 46 (2002) 1443–1449 www.elsevier.com/locate/chemosphere
Recent survey and effects of cooking processes on levels of PCDDs, PCDFs and Co-PCBs in leafy vegetables in Japan Tomoaki Tsutsumi a,*, Takao Iida b, Tsuguhide Hori b, Reiko Nakagawa b, Kazuhiro Tobiishi b, Toshihiko Yanagi c, Yoichi Kono c, Hiroyasu Uchibe c, Rieko Matsuda a, Kumiko Sasaki a, Masatake Toyoda a a b
Division of Foods, National Institute of Health Sciences, 1-18-1, Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan Fukuoka Institute of Health and Environmental Sciences, 39, Mukaizano, Dazaifu-shi, Fukuoka 818-0135, Japan c Japan Food Research Laboratories, 52-1 Motoyoyogi-cho, Shibuya-ku, Tokyo 151-0062, Japan
Abstract We report here the latest levels of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) and coplanar polychlorinated biphenyls (Co-PCBs) in leafy vegetables in Japan as well as the effect of cooking processes on the reduction of these contaminants. Three kinds of leafy vegetables (‘‘komatsuna’’, lettuce and spinach) from seven districts in Japan in 1998 were analyzed for the 2,3,7,8-chlorine substituted PCDD/Fs and three non-ortho-PCBs (#77, 126 and 169). The mean total TEQ levels (using the WHO-TEFs) in the komatsuna, lettuce and spinach were 0.094, 0.025 and 0.196 pg/g fresh weight, respectively. The TEQ levels are dominated by 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, 2,3,4,7,8-PeCDF and 3,30 ,4,40 ,5-PeCB in many of the samples. For one of these isomers, the 2,3,4,7,8-PeCDF TEQ levels showed good correlation with the total TEQ levels in the samples (r ¼ 0:957). This suggests that 2,3,4,7,8-PeCDF may be an indicator for dioxin contamination in the analysis of the leafy vegetables. Also, the effects of two cooking processes (washing and washing followed by boiling) on the dioxin levels in two types of spinach samples were investigated. On average, in both samples, the total concentrations of the PCDDs, PCDFs and Co-PCB were reduced to about 38%, 73% and 88% of the initial concentrations by washing, and to 21%, 35% and 61% of the initial concentrations by washing followed by boiling. The total TEQ levels were reduced to about 30% of the initial TEQ levels by washing followed by boiling. Significant reductions in the TEQ levels were observed in the cooked samples. Thus, the cooking processes may reduce the risk of dioxin intake from the leafy vegetables. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Dioxins; Polychlorinated dibenzo-p-dioxins; Polychlorinated dibenzofurans; Coplanar polychlorinated biphenyls; Cooking processes; Vegetables
1. Introduction Food consumption is the main route of exposure to polychlorinated dibenzo-p-dioxins/polychlorinated di-
*
Corresponding author. Tel.: +81-3-3700-1141x334; fax: +81-3-3707-6950. E-mail address: [email protected] (T. Tsutsumi).
benzofurans (PCDD/Fs) and Co-PCBs in humans. Many surveys have determined the levels of PCDD/Fs and coplanar polychlorinated biphenyls (Co-PCBs) in foods from various countries and regions (Liem et al., 2000). However, there are very few reports concerning the levels of PCDD/Fs and Co-PCBs in leafy vegetables in Japan (Toyoda et al., 1999a). Additionally, recently in Japan, the dioxin reports by the media stirred up public anxieties with regard to the dioxin levels in leafy
0045-6535/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 0 4 5 - 6 5 3 5 ( 0 1 ) 0 0 2 7 5 - 2
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vegetables (Watts, 1999). Therefore, the latest survey of PCDD/F and Co-PCB levels in leafy vegetables is required. Also, little attention has been given to the effects of cooking processes on the levels of the PCDD/Fs and CoPCBs. Although a few reports have discussed the effects of cooking processes on their levels in meat and fish samples (Petroske et al., 1998, Schecter et al., 1998, Thorpe et al., 1999, Zabik and Zabik, 1999), we found no reports concerning leafy vegetables. A detailed knowledge of the effects of cooking processes on their levels in leafy vegetables is necessary for risk assessment. In this paper, we describe the latest survey of PCDD/ F and Co-PCB levels in popular leafy vegetables, komatsuna, lettuce and spinach in Japan as well as the effect of two cooking processes (1. washing and 2. washing followed by boiling) on the reduction of these contaminants in the spinach samples. A part of this experiment was reported as a preliminary communication (Tsutsumi et al., 2000).
2. Materials and methods Sample collections: For a survey of leafy vegetables, komatsuna, lettuce and spinach were purchased in seven districts through Japan (Hokkaido, Tohoku, Kanto, Chubu, Kansai, Chugoku-Shikoku and Kyushu districts) in 1998. In the study of the effects of cooking processes, two types of spinach samples were used. One was purchased in 1999 from a supermarket in Fukuoka, Japan, and the other was collected in 1999 from a private vegetable garden in Fukuoka, Japan. Cooking: Two cooking processes, washing and washing followed by boiling, were examined because they are very popular cooking styles for spinach in Japan. For the two types of spinach samples, the one from the private vegetable garden had slightly adhered soil, therefore, it was shaken to remove the soil before cooking, while the other from a supermarket had no observed soil adhesion. These samples had their roots cut off and were then cooked. The samples (about 150 g)
Table 1 Concentrations of PCDD/Fs and Co-PCBs in three kinds of leafy vegetables in Japan in 1998 (pg/g fresh weight)a Isomers
Komatsuna (n ¼ 7)
Lettuce (n ¼ 7)
Spinach (n ¼ 7)
Mean
Mean
Range
Mean
Range
ND –0.03 ND–0.04 ND ND–0.05 ND–0.05 0.05–0.90 0.61–17.00
0.00 0.01 0.00 0.01 0.00 0.04 0.47
(1) (1) (1) (1) (1) (4) (6)
ND–0.03 ND–0.05 ND–0.02 ND–0.04 ND–0.03 ND–0.21 ND–1.90
0.02 (6) 0.05 (6) 0.02 (4) 0.05 (6) 0.04 (6) 0.92 (7) 11.37 (7)
ND–0.04 ND–0.07 ND–0.06 ND–0.13 ND–0.12 0.08–4.70 0.54–67.00
Range b
c
PCDDs
2,3,7,8-TCDD 1,2,3,7,8-PeCDD 1,2,3,4,7,8-HxCDD 1,2,3,6,7,8-HxCDD 1,2,3,7,8,9-HxCDD 1,2,3,4,6,7,8-HpCDD OCDD
0.01 0.02 0.00 0.01 0.01 0.25 3.55
(5) (5) (0) (2) (3) (7) (7)
PCDFs
2,3,7,8-TCDF 1,2,3,7,8-PeCDF 2,3,4,7,8-PeCDF 1,2,3,4,7,8-HxCDF 1,2,3,6,7,8-HxCDF 1,2,3,7,8,9-HxCDF 2,3,4,6,7,8-HxCDF 1,2,3,4,6,7,8-HpCDF 1,2,3,4,7,8,9-HpCDF OCDF
0.03 0.06 0.04 0.04 0.04 0.00 0.04 0.16 0.01 0.20
(7) (7) (6) (6) (5) (0) (6) (7) (2) (6)
0.01–0.05 0.02–0.10 ND–0.06 ND–0.06 ND–0.07 ND ND–0.09 0.04–0.29 ND–0.04 ND–0.80
0.00 0.03 0.01 0.01 0.01 0.00 0.01 0.03 0.00 0.04
(1) (1) (1) (1) (1) (0) (1) (1) (1) (1)
ND–0.03 ND–0.18 ND–0.07 ND–0.10 ND–0.08 ND ND–0.07 ND–0.18 ND–0.03 ND–0.26
0.10 0.14 0.08 0.07 0.08 0.00 0.07 0.26 0.03 0.27
(6) (7) (6) (6) (6) (0) (6) (7) (5) (7)
ND–0.14 0.02–0.19 ND–0.11 ND–0.10 ND–0.11 ND ND–0.13 0.04–0.52 ND–0.07 0.07–1.00
Co-PCBs
3,30 ,4,40 -TCB 3,30 ,4,40 ,5-PeCB 3,30 ,4,40 ,5,50 -HxCB
0.51 (7) 0.20 (7) 0.03 (6)
0.24–0.81 0.08–0.36 ND–0.05
0.07 (7) 0.01 (1) 0.00 (1)
0.04–0.17 ND–0.06 ND–0.02
1.81 (7) 0.25 (7) 0.05 (6)
0.26–3.70 0.06–0.52 ND–0.10
Total PCDDs Total PCDFs Total Co-PCBs
3.85 (7) 0.62 (7) 0.74 (7)
0.66–18.02 0.07–1.39 0.32–1.22
0.53 (6) 0.14 (1) 0.08 (7)
0.00–2.28 0.00–1.00 0.04–0.25
12.48 (7) 1.09 (7) 2.12 (7)
0.80–72.08 0.14–1.92 0.32–4.20
Total TEQ
0.094
0.011–0.153
0.025
<0.001–0.172
0.196
0.008–0.276
a
All samples were collected from seven districts of Japan in 1998. Mean values were calculated from seven samples (calculated at ND ¼ 0). b Values in parentheses indicate the number of positives. c ND: not detected.
T. Tsutsumi et al. / Chemosphere 46 (2002) 1443–1449
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Fig. 1. Percentage contribution of the isomers to the total TEQ in the highest contaminated vegetables.
were washed with running tap water, and then boiled in 1 l of tap water for about 2 min. Uncooked samples were defined as the samples with the roots removed. Four examinations of each cooking process were carried out.
Determination of PCDD/Fs and Co-PCBs: The samples in the survey had the inedible parts removed according to the general methods of analysis of foods in Japan. All the samples in this study were chopped in a blender, and then were spiked with 17 kinds of
Fig. 2. Correlation between the total TEQ levels and TEQ levels of the dominant isomers in the leafy vegetables. The data (totally 35 samples of komatsuna, lettuce and spinach) obtained from the present and previous survey (Toyoda et al., 1999a) were analyzed.
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13 C12 -labeled PCDD/Fs and three kinds of 13 C12 -labeled non-ortho-PCBs (IUPAC no. #77, 126 and 169) (50–100 pg each isomer/sample) before extraction. The extraction, cleanup and analysis of the PCDD/Fs and CoPCBs generally followed a previously reported protocol (Hori et al., 1999). Briefly, the samples were digested in a 1 M KOH/ethanol solution at room temperature. The alkaline hydrolysates were then extracted twice with n-hexane. After treatment with concentrated sulfuric acid, the extracts were purified on a silver nitrate/silica gel column followed by an activated carbon column. On the activated carbon column, the PCDD/Fs and nonortho-PCBs were eluted with toluene. The eluate was concentrated and dissolved in n-nonane (20–25 ll). The analyses of seventeen 2,3,7,8-chlorine substituted PCDD/Fs and the three non-ortho-PCBs were performed by high resolution gas chromatography/high resolution mass spectrometry using a HP6890 plus gas chromatograph coupled to a Micromass Autospec mass
spectrometer. The samples (2 ll) were injected in the splitless mode. The detection limits were 0.01 pg/g for the TCDD/F, 0.02 pg/g for the PeCDD/Fs, HxCDD/Fs and HpCDD/Fs, 0.05 pg/g for OCDD/F and 0.01 pg/g for the non-ortho-PCBs in the survey, and 0.01 pg/g for the TCDD/F, 0.02 pg/g for the PeCDD/Fs and HxCDD/ Fs, 0.05 pg/g for the HpCDD/Fs, 0.1 pg/g for OCDD/F and 0.01 pg/g for the non-ortho-PCBs in the study of the cooking effects. The TEQs were calculated using the WHO-TEFs (Van den Berg et al., 1998).
3. Results and discussion Table 1 summarizes the concentrations of the PCDD/ Fs and Co-PCBs as well as total TEQ levels in the three kinds of vegetables from seven districts in Japan. Many isomers were detected in the komatsuna and spinach samples, while few isomers were detected in the lettuce
Table 2 Concentrations of PCDD/Fs and Co-PCBs in uncooked and cooked spinach samples from a vegetable garden (pg/g fresh weight)a Isomers
Cookedb
Uncooked Mean
Range
Washed
Washed and boiled
Mean
Range
Mean
Range
PCDDs
2,3,7,8-TCDD 1,2,3,7,8-PeCDD 1,2,3,4,7,8-HxCDD 1,2,3,6,7,8-HxCDD 1,2,3,7,8,9-HxCDD 1,2,3,4,6,7,8-HpCDD OCDD
0 0.09 0.04 0.11 0.04 1.00 12.56
ND 0.08–0.10 0.03–0.04 0.08–0.13 ND–0.08 0.80–1.25 9.97–15.80
0 0.07 0.01 0.05 0 0.46 4.27
ND 0.05–0.08 ND–0.02 0.04–0.08 ND 0.43–0.50 3.88–4.82
0 0.03 0 0.02 0 0.25 2.67
ND ND–0.05 ND ND–0.03 ND 0.20–0.30 2.07–3.48
PCDFs
2,3,7,8-TCDF 1,2,3,7,8-PeCDF 2,3,4,7,8-PeCDF 1,2,3,4,7,8-HxCDF 1,2,3,6,7,8-HxCDF 1,2,3,7,8,9-HxCDF 2,3,4,6,7,8-HxCDF 1,2,3,4,6,7,8-HpCDF 1,2,3,4,7,8,9-HpCDF OCDF
0.07 0.07 0.05 0.07 0.05 0 0.14 0.27 0 0
0.07–0.08 0.05–0.08 0.05–0.06 0.06–0.08 0.04–0.06 ND 0.12–0.16 0.22–0.32 ND ND
0.07 0.05 0.04 0.06 0.05 0 0.08 0.14 0 0
0.06–0.08 0.04–0.06 0.03–0.04 0.03–0.07 0.04–0.06 ND 0.07–0.08 0.13–0.15 ND ND
0.04 0.04 0.02 0.02 0.02 0 0.04 0.08 0 0
0.03–0.06 0.03–0.04 0.02–0.03 ND–0.04 ND–0.04 ND 0.03–0.05 0.07–0.10 ND ND
Co-PCBs
3,30 ,4,40 -TCB 3,30 ,4,40 ,5-PeCB 3,30 ,4,40 ,5,50 -HxCB
1.77 0.23 0.04
1.60–1.91 0.19–0.25 0.03–0.05
1.57 0.20 0.05
1.51–1.60 0.19–0.22 0.04–0.05
1.06 0.13 0.03
0.83–1.31 0.11–0.16 0.02–0.04
4.86
4.42–5.47 (35%) 0.43–0.51 (68%) 1.75–1.88 (89%)
2.96
2.30–3.86 (21%) 0.20–0.35 (38%) 0.96–1.51 (60%)
Total PCDDs (mean residue percent) Total PCDFs (mean residue percent) Total Co-PCBs (mean residue percent) Total TEQ a b
13.84 0.71 2.04 0.211
10.98–17.31 (100%) 0.61–0.83 (100%) 1.82–2.21 (100%) 0.189–0.226
Mean values were calculated from four examinations (calculated at ND ¼ 0). The concentrations were calculated on the basis of the original weights.
0.48 1.82 0.144
0.123–0.157
0.26 1.23 0.071
0.043–0.105
T. Tsutsumi et al. / Chemosphere 46 (2002) 1443–1449
samples except for one sample. OCDD and 3,30 ,4,40 TCB were generally found to be abundant in the samples. Also, the highly toxic isomers, 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD and 2,3,4,7,8-PeCDF, were detected in almost all the komatsuna and spinach samples. Although the samples had wide range of total TEQ levels, the vegetables can be ranked according to their mean total TEQ levels as follows: spinach > komatsuna > lettuce. The total TEQ levels in the komatsuna and spinach samples were similar to the values obtained from our previous report (Toyoda et al., 1999a). Fig. 1 shows the contribution of isomers in the total TEQ levels of the highest contaminated samples of each vegetable. The total TEQ levels are dominated by 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, 2,3,4,7,8-PeCDF and 3,30 ,4,40 ,5-PeCB (above 70% of each total TEQ level). The contribution patterns of the isomers were similar between the three kinds of vegetables, suggesting that these vegetables are contaminated by the same kind of
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pollution sources. It is well known that the PCDD/F contamination in leafy vegetables is mainly derived from environmental air (M€ uller et al., 1994, Smith and Jones, 2000). In fact, some of the dominant isomers, 1,2,3,7,8PeCDD, 2,3,4,7,8-PeCDF and 3,30 ,4,40 ,5-PeCB are also found to make an important contribution to the total TEQ in the environmental air (Lohmann and Jones, 1998, Shibayama et al., 2000). The outer leaves of lettuce are abundant in PCDD/Fs compared to the inner leaves, probably because the outer leaves are in more contact with the environmental air (H€ ulster and Marschner, 1993). However, in our study, the outer leaves were discarded from the analyzed samples before the sample preparation since they are inedible parts. Therefore, total TEQ levels of the lettuce samples are much lower than those of the komatsuna and spinach samples in most cases (Table 1). Fig. 2 shows a correlation between the total TEQ levels and TEQ levels of the dominant isomers in the
Table 3 Concentrations of PCDD/Fs and Co-PCBs in uncooked and cooked spinach samples from a supermarket (pg/g fresh weight)a Isomers
Cookedb
Uncooked Mean
Range
Washed
Washed and boiled
Mean
Range
Mean
Range
PCDDs
2,3,7,8-TCDD 1,2,3,7,8-PeCDD 1,2,3,4,7,8-HxCDD 1,2,3,6,7,8-HxCDD 1,2,3,7,8,9-HxCDD 1,2,3,4,6,7,8-HpCDD OCDD
0 0.04 0.01 0.04 0 0.46 5.44
ND 0.03–0.04 ND–0.03 0.03–0.05 ND 0.31–0.64 3.77–6.93
0 0.02 0.01 0.03 0.01 0.22 2.20
ND ND–0.03 ND–0.02 0.02–0.05 ND–0.04 0.19–0.26 1.73–2.52
0 0 0.01 0.01 0 0.11 1.12
ND ND ND–0.02 ND–0.02 ND 0.09–0.13 1.02–1.19
PCDFs
2,3,7,8-TCDF 1,2,3,7,8-PeCDF 2,3,4,7,8-PeCDF 1,2,3,4,7,8-HxCDF 1,2,3,6,7,8-HxCDF 1,2,3,7,8,9-HxCDF 2,3,4,6,7,8-HxCDF 1,2,3,4,6,7,8-HpCDF 1,2,3,4,7,8,9-HpCDF OCDF
0.07 0.07 0.04 0.05 0.05 0.01 0.04 0.16 0 0
0.06–0.08 0.05–0.10 0.03–0.05 0.04–0.06 0.03–0.06 ND–0.03 0.03–0.05 0.11–0.19 ND ND
0.07 0.06 0.03 0.04 0.04 0 0.03 0.11 0 0
0.06–0.08 0.06–0.07 0.03–0.03 0.03–0.04 0.03–0.05 ND 0.03–0.04 0.09–0.12 ND ND
0.04 0.04 0.01 0.01 0.01 0 0.01 0.04 0 0
0.03–0.05 0.03–0.06 ND–0.03 ND–0.02 ND–0.02 ND ND–0.02 ND–0.06 ND ND
Co-PCBs
3,30 ,4,40 -TCB 3,30 ,4,40 ,5-PeCB 3,30 ,4,40 ,5,50 -HxCB
0.73 0.12 0.04
0.65–0.78 0.11–0.13 0.03–0.04
0.63 0.11 0.03
0.55–0.73 0.09–0.15 0.02–0.03
0.46 0.07 0.02
0.37–0.62 0.05–0.09 ND–0.03
Total PCDDs (mean residue percent) Total PCDFs (mean residue percent) Total Co-PCBs (mean residue percent)
5.98
4.14–7.58 (100%) 0.35–0.59 (100%) 0.79–0.94 (100%)
2.48
2.01–2.83 (41%) 0.34–0.40 (77%) 0.67–0.91 (87%)
1.23
1.13–1.36 (21%) 0.12–0.24 (31%) 0.42–0.73 (61%)
Total TEQ
0.106
a b
0.48 0.89
0.082–0.122
0.37 0.77 0.070
Mean values were calculated from four examinations (calculated at ND ¼ 0). The concentrations were calculated on the basis of the original weights.
0.049–0.094
0.15 0.54 0.022
0.012–0.042
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Fig. 3. TEQ levels reduction after the cooking processes in the spinach samples. Results represent mean SD of four examinations. The significance of the difference between each sample was assessed by student’s t-test. NS, not significant (p ¼ 0:052); , p < 0:05; , p < 0:01. The values in parentheses under X -axis indicate the mean residue percent of the total TEQ levels.
vegetables. In the correlation study, the present survey data along with previous survey data (Toyoda et al., 1999a), totally 35 samples (consisting of 14 komatsuna, 7 lettuce and 14 spinach samples), were analyzed. The 1,2,3,7,8-PeCDD, 2,3,4,7,8-PeCDF or 3,30 ,4,40 ,5-PeCB TEQ levels correlated well with the total TEQ levels. Especially, we found a strong correlation (r ¼ 0:957) between the total and 2,3,4,7,8-PeCDF TEQ levels in the vegetables. This result suggests that this isomer would be applicable as an indicator for dioxin contamination in the analysis of leafy vegetables. Next, we investigated the effects of the cooking processes on the PCDD/F and Co-PCB levels in two types of spinach samples. Two cooking processes, washing and washing followed by boiling, were examined. Tables 2 and 3 show the concentrations of the PCDD/Fs and Co-PCBs in the uncooked and cooked spinach samples from a private vegetable garden and supermarket. Since the sample’s weight changes during the processing, the concentrations in the cooked samples were calculated on the basis of the original weights. In both samples, the concentrations of many of the isomers decreased by the washing and boiling processes. On average, in both samples, the total concentrations of the PCDDs, PCDFs and Co-PCBs were reduced to 38%, 73% and 88% of the initial concentrations by washing, and to 21%, 35% and 61% of the initial concentrations by washing followed by boiling, respectively. Especially, washing followed by the boiling process effectively reduced the concentrations of almost all the isomers in both samples. Fig. 3 shows the reduction of the TEQ levels by the cooking processes in the two types of spinach samples. On average, in both samples, the total TEQ levels were reduced to about 70% of the initial TEQ levels by washing, and to about 30% of the initial TEQ levels by
washing followed by boiling. Significant reductions in the total TEQ levels were observed in most of the cooked samples. Thus, the cooking processes can possibly reduce the risk of dioxin intake from the leafy vegetables. The reduction of PCDD/Fs and Co-PCBs appears to be mainly due to the exclusion of particlebound dioxins from the spinach surface by washing and boiling, although we cannot determine the reduction mechanisms in the present experiment. In this study, we focused on leafy vegetables because of the limited information regarding the PCDD/F and Co-PCB levels. But, recently in Japan, about 60% of the dietary intake of dioxins is likely to come from the intake of fish and shellfish (Toyoda et al., 1999b). Therefore, a detailed investigation of the effects of various cooking processes on their levels in fish and shellfish is strongly needed to accurately estimate the intake of dioxins through diet.
Acknowledgements A part of this work was supported by a Health Sciences Research Grants from the Ministry of Health, Labour and Welfare, Japan.
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Thorpe, S., Kelly, M., Startin, J., Harrison, N., Rose, M., 1999. The effects of cooking by various methods on concentrations of PCDDs and PCDFs in bovine meat. Organohalogen Compd. 44, 237–238. Toyoda, M., Iida, T., Hori, T., Yanagi, T., Kono, Y., Uchibe, H., 1999a. Concentrations of PCDDs, PCDFs and coplanar PCBs in Japanese retail foods. J. Food Hyg. Soc. Japan 40, 111–121 (in Japanese). Toyoda, M., Iida, T., Hori, T., Yanagi, T., Kono, Y., Uchibe, H., 1999b. Dietary daily intake of PCDDs, PCDFs and coplanar PCBs by total diet study in Japan. J. Food Hyg. Soc. Japan 40, 98–110 (in Japanese). Tsutsumi, T., Iida, T., Hori, T., Yanagi, T., Kono, Y., Uchibe, H., Toyoda, M., 2000. Levels of PCDDs, PCDFs and Co-PCBs in fresh and cooked leafy vegetables in Japan. Organohalogen Compd. 47, 296–299. Van den Berg, M., Birnbaum, L., Bosveld, A.T.C., Brunstrom, B., Cook, P., Feeley, M., et al., 1998. Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife. Environ. Health Persp. 106, 775–792. Watts, J., 1999. TV asahi and the dioxin report stir up public anxieties. Lancet 353, 1337. Zabik, M.E., Zabik, M.J., 1999. Polychlorinated biphenyls, polybrominated biphenyls, and dioxin reduction during processing/cooking food. Adv. Exprim. Med. Biol. 459, 213–231.
Recent survey and effects of cooking processes on levels of PCDDs, PCDFs and Co-PCBs in leafy vegetables in Japan Tomoaki Tsutsumi a,*, Takao Iida b, Tsuguhide Hori b, Reiko Nakagawa b, Kazuhiro Tobiishi b, Toshihiko Yanagi c, Yoichi Kono c, Hiroyasu Uchibe c, Rieko Matsuda a, Kumiko Sasaki a, Masatake Toyoda a a b
Division of Foods, National Institute of Health Sciences, 1-18-1, Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan Fukuoka Institute of Health and Environmental Sciences, 39, Mukaizano, Dazaifu-shi, Fukuoka 818-0135, Japan c Japan Food Research Laboratories, 52-1 Motoyoyogi-cho, Shibuya-ku, Tokyo 151-0062, Japan
Abstract We report here the latest levels of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) and coplanar polychlorinated biphenyls (Co-PCBs) in leafy vegetables in Japan as well as the effect of cooking processes on the reduction of these contaminants. Three kinds of leafy vegetables (‘‘komatsuna’’, lettuce and spinach) from seven districts in Japan in 1998 were analyzed for the 2,3,7,8-chlorine substituted PCDD/Fs and three non-ortho-PCBs (#77, 126 and 169). The mean total TEQ levels (using the WHO-TEFs) in the komatsuna, lettuce and spinach were 0.094, 0.025 and 0.196 pg/g fresh weight, respectively. The TEQ levels are dominated by 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, 2,3,4,7,8-PeCDF and 3,30 ,4,40 ,5-PeCB in many of the samples. For one of these isomers, the 2,3,4,7,8-PeCDF TEQ levels showed good correlation with the total TEQ levels in the samples (r ¼ 0:957). This suggests that 2,3,4,7,8-PeCDF may be an indicator for dioxin contamination in the analysis of the leafy vegetables. Also, the effects of two cooking processes (washing and washing followed by boiling) on the dioxin levels in two types of spinach samples were investigated. On average, in both samples, the total concentrations of the PCDDs, PCDFs and Co-PCB were reduced to about 38%, 73% and 88% of the initial concentrations by washing, and to 21%, 35% and 61% of the initial concentrations by washing followed by boiling. The total TEQ levels were reduced to about 30% of the initial TEQ levels by washing followed by boiling. Significant reductions in the TEQ levels were observed in the cooked samples. Thus, the cooking processes may reduce the risk of dioxin intake from the leafy vegetables. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Dioxins; Polychlorinated dibenzo-p-dioxins; Polychlorinated dibenzofurans; Coplanar polychlorinated biphenyls; Cooking processes; Vegetables
1. Introduction Food consumption is the main route of exposure to polychlorinated dibenzo-p-dioxins/polychlorinated di-
*
Corresponding author. Tel.: +81-3-3700-1141x334; fax: +81-3-3707-6950. E-mail address: [email protected] (T. Tsutsumi).
benzofurans (PCDD/Fs) and Co-PCBs in humans. Many surveys have determined the levels of PCDD/Fs and coplanar polychlorinated biphenyls (Co-PCBs) in foods from various countries and regions (Liem et al., 2000). However, there are very few reports concerning the levels of PCDD/Fs and Co-PCBs in leafy vegetables in Japan (Toyoda et al., 1999a). Additionally, recently in Japan, the dioxin reports by the media stirred up public anxieties with regard to the dioxin levels in leafy
0045-6535/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 0 4 5 - 6 5 3 5 ( 0 1 ) 0 0 2 7 5 - 2
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vegetables (Watts, 1999). Therefore, the latest survey of PCDD/F and Co-PCB levels in leafy vegetables is required. Also, little attention has been given to the effects of cooking processes on the levels of the PCDD/Fs and CoPCBs. Although a few reports have discussed the effects of cooking processes on their levels in meat and fish samples (Petroske et al., 1998, Schecter et al., 1998, Thorpe et al., 1999, Zabik and Zabik, 1999), we found no reports concerning leafy vegetables. A detailed knowledge of the effects of cooking processes on their levels in leafy vegetables is necessary for risk assessment. In this paper, we describe the latest survey of PCDD/ F and Co-PCB levels in popular leafy vegetables, komatsuna, lettuce and spinach in Japan as well as the effect of two cooking processes (1. washing and 2. washing followed by boiling) on the reduction of these contaminants in the spinach samples. A part of this experiment was reported as a preliminary communication (Tsutsumi et al., 2000).
2. Materials and methods Sample collections: For a survey of leafy vegetables, komatsuna, lettuce and spinach were purchased in seven districts through Japan (Hokkaido, Tohoku, Kanto, Chubu, Kansai, Chugoku-Shikoku and Kyushu districts) in 1998. In the study of the effects of cooking processes, two types of spinach samples were used. One was purchased in 1999 from a supermarket in Fukuoka, Japan, and the other was collected in 1999 from a private vegetable garden in Fukuoka, Japan. Cooking: Two cooking processes, washing and washing followed by boiling, were examined because they are very popular cooking styles for spinach in Japan. For the two types of spinach samples, the one from the private vegetable garden had slightly adhered soil, therefore, it was shaken to remove the soil before cooking, while the other from a supermarket had no observed soil adhesion. These samples had their roots cut off and were then cooked. The samples (about 150 g)
Table 1 Concentrations of PCDD/Fs and Co-PCBs in three kinds of leafy vegetables in Japan in 1998 (pg/g fresh weight)a Isomers
Komatsuna (n ¼ 7)
Lettuce (n ¼ 7)
Spinach (n ¼ 7)
Mean
Mean
Range
Mean
Range
ND –0.03 ND–0.04 ND ND–0.05 ND–0.05 0.05–0.90 0.61–17.00
0.00 0.01 0.00 0.01 0.00 0.04 0.47
(1) (1) (1) (1) (1) (4) (6)
ND–0.03 ND–0.05 ND–0.02 ND–0.04 ND–0.03 ND–0.21 ND–1.90
0.02 (6) 0.05 (6) 0.02 (4) 0.05 (6) 0.04 (6) 0.92 (7) 11.37 (7)
ND–0.04 ND–0.07 ND–0.06 ND–0.13 ND–0.12 0.08–4.70 0.54–67.00
Range b
c
PCDDs
2,3,7,8-TCDD 1,2,3,7,8-PeCDD 1,2,3,4,7,8-HxCDD 1,2,3,6,7,8-HxCDD 1,2,3,7,8,9-HxCDD 1,2,3,4,6,7,8-HpCDD OCDD
0.01 0.02 0.00 0.01 0.01 0.25 3.55
(5) (5) (0) (2) (3) (7) (7)
PCDFs
2,3,7,8-TCDF 1,2,3,7,8-PeCDF 2,3,4,7,8-PeCDF 1,2,3,4,7,8-HxCDF 1,2,3,6,7,8-HxCDF 1,2,3,7,8,9-HxCDF 2,3,4,6,7,8-HxCDF 1,2,3,4,6,7,8-HpCDF 1,2,3,4,7,8,9-HpCDF OCDF
0.03 0.06 0.04 0.04 0.04 0.00 0.04 0.16 0.01 0.20
(7) (7) (6) (6) (5) (0) (6) (7) (2) (6)
0.01–0.05 0.02–0.10 ND–0.06 ND–0.06 ND–0.07 ND ND–0.09 0.04–0.29 ND–0.04 ND–0.80
0.00 0.03 0.01 0.01 0.01 0.00 0.01 0.03 0.00 0.04
(1) (1) (1) (1) (1) (0) (1) (1) (1) (1)
ND–0.03 ND–0.18 ND–0.07 ND–0.10 ND–0.08 ND ND–0.07 ND–0.18 ND–0.03 ND–0.26
0.10 0.14 0.08 0.07 0.08 0.00 0.07 0.26 0.03 0.27
(6) (7) (6) (6) (6) (0) (6) (7) (5) (7)
ND–0.14 0.02–0.19 ND–0.11 ND–0.10 ND–0.11 ND ND–0.13 0.04–0.52 ND–0.07 0.07–1.00
Co-PCBs
3,30 ,4,40 -TCB 3,30 ,4,40 ,5-PeCB 3,30 ,4,40 ,5,50 -HxCB
0.51 (7) 0.20 (7) 0.03 (6)
0.24–0.81 0.08–0.36 ND–0.05
0.07 (7) 0.01 (1) 0.00 (1)
0.04–0.17 ND–0.06 ND–0.02
1.81 (7) 0.25 (7) 0.05 (6)
0.26–3.70 0.06–0.52 ND–0.10
Total PCDDs Total PCDFs Total Co-PCBs
3.85 (7) 0.62 (7) 0.74 (7)
0.66–18.02 0.07–1.39 0.32–1.22
0.53 (6) 0.14 (1) 0.08 (7)
0.00–2.28 0.00–1.00 0.04–0.25
12.48 (7) 1.09 (7) 2.12 (7)
0.80–72.08 0.14–1.92 0.32–4.20
Total TEQ
0.094
0.011–0.153
0.025
<0.001–0.172
0.196
0.008–0.276
a
All samples were collected from seven districts of Japan in 1998. Mean values were calculated from seven samples (calculated at ND ¼ 0). b Values in parentheses indicate the number of positives. c ND: not detected.
T. Tsutsumi et al. / Chemosphere 46 (2002) 1443–1449
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Fig. 1. Percentage contribution of the isomers to the total TEQ in the highest contaminated vegetables.
were washed with running tap water, and then boiled in 1 l of tap water for about 2 min. Uncooked samples were defined as the samples with the roots removed. Four examinations of each cooking process were carried out.
Determination of PCDD/Fs and Co-PCBs: The samples in the survey had the inedible parts removed according to the general methods of analysis of foods in Japan. All the samples in this study were chopped in a blender, and then were spiked with 17 kinds of
Fig. 2. Correlation between the total TEQ levels and TEQ levels of the dominant isomers in the leafy vegetables. The data (totally 35 samples of komatsuna, lettuce and spinach) obtained from the present and previous survey (Toyoda et al., 1999a) were analyzed.
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13 C12 -labeled PCDD/Fs and three kinds of 13 C12 -labeled non-ortho-PCBs (IUPAC no. #77, 126 and 169) (50–100 pg each isomer/sample) before extraction. The extraction, cleanup and analysis of the PCDD/Fs and CoPCBs generally followed a previously reported protocol (Hori et al., 1999). Briefly, the samples were digested in a 1 M KOH/ethanol solution at room temperature. The alkaline hydrolysates were then extracted twice with n-hexane. After treatment with concentrated sulfuric acid, the extracts were purified on a silver nitrate/silica gel column followed by an activated carbon column. On the activated carbon column, the PCDD/Fs and nonortho-PCBs were eluted with toluene. The eluate was concentrated and dissolved in n-nonane (20–25 ll). The analyses of seventeen 2,3,7,8-chlorine substituted PCDD/Fs and the three non-ortho-PCBs were performed by high resolution gas chromatography/high resolution mass spectrometry using a HP6890 plus gas chromatograph coupled to a Micromass Autospec mass
spectrometer. The samples (2 ll) were injected in the splitless mode. The detection limits were 0.01 pg/g for the TCDD/F, 0.02 pg/g for the PeCDD/Fs, HxCDD/Fs and HpCDD/Fs, 0.05 pg/g for OCDD/F and 0.01 pg/g for the non-ortho-PCBs in the survey, and 0.01 pg/g for the TCDD/F, 0.02 pg/g for the PeCDD/Fs and HxCDD/ Fs, 0.05 pg/g for the HpCDD/Fs, 0.1 pg/g for OCDD/F and 0.01 pg/g for the non-ortho-PCBs in the study of the cooking effects. The TEQs were calculated using the WHO-TEFs (Van den Berg et al., 1998).
3. Results and discussion Table 1 summarizes the concentrations of the PCDD/ Fs and Co-PCBs as well as total TEQ levels in the three kinds of vegetables from seven districts in Japan. Many isomers were detected in the komatsuna and spinach samples, while few isomers were detected in the lettuce
Table 2 Concentrations of PCDD/Fs and Co-PCBs in uncooked and cooked spinach samples from a vegetable garden (pg/g fresh weight)a Isomers
Cookedb
Uncooked Mean
Range
Washed
Washed and boiled
Mean
Range
Mean
Range
PCDDs
2,3,7,8-TCDD 1,2,3,7,8-PeCDD 1,2,3,4,7,8-HxCDD 1,2,3,6,7,8-HxCDD 1,2,3,7,8,9-HxCDD 1,2,3,4,6,7,8-HpCDD OCDD
0 0.09 0.04 0.11 0.04 1.00 12.56
ND 0.08–0.10 0.03–0.04 0.08–0.13 ND–0.08 0.80–1.25 9.97–15.80
0 0.07 0.01 0.05 0 0.46 4.27
ND 0.05–0.08 ND–0.02 0.04–0.08 ND 0.43–0.50 3.88–4.82
0 0.03 0 0.02 0 0.25 2.67
ND ND–0.05 ND ND–0.03 ND 0.20–0.30 2.07–3.48
PCDFs
2,3,7,8-TCDF 1,2,3,7,8-PeCDF 2,3,4,7,8-PeCDF 1,2,3,4,7,8-HxCDF 1,2,3,6,7,8-HxCDF 1,2,3,7,8,9-HxCDF 2,3,4,6,7,8-HxCDF 1,2,3,4,6,7,8-HpCDF 1,2,3,4,7,8,9-HpCDF OCDF
0.07 0.07 0.05 0.07 0.05 0 0.14 0.27 0 0
0.07–0.08 0.05–0.08 0.05–0.06 0.06–0.08 0.04–0.06 ND 0.12–0.16 0.22–0.32 ND ND
0.07 0.05 0.04 0.06 0.05 0 0.08 0.14 0 0
0.06–0.08 0.04–0.06 0.03–0.04 0.03–0.07 0.04–0.06 ND 0.07–0.08 0.13–0.15 ND ND
0.04 0.04 0.02 0.02 0.02 0 0.04 0.08 0 0
0.03–0.06 0.03–0.04 0.02–0.03 ND–0.04 ND–0.04 ND 0.03–0.05 0.07–0.10 ND ND
Co-PCBs
3,30 ,4,40 -TCB 3,30 ,4,40 ,5-PeCB 3,30 ,4,40 ,5,50 -HxCB
1.77 0.23 0.04
1.60–1.91 0.19–0.25 0.03–0.05
1.57 0.20 0.05
1.51–1.60 0.19–0.22 0.04–0.05
1.06 0.13 0.03
0.83–1.31 0.11–0.16 0.02–0.04
4.86
4.42–5.47 (35%) 0.43–0.51 (68%) 1.75–1.88 (89%)
2.96
2.30–3.86 (21%) 0.20–0.35 (38%) 0.96–1.51 (60%)
Total PCDDs (mean residue percent) Total PCDFs (mean residue percent) Total Co-PCBs (mean residue percent) Total TEQ a b
13.84 0.71 2.04 0.211
10.98–17.31 (100%) 0.61–0.83 (100%) 1.82–2.21 (100%) 0.189–0.226
Mean values were calculated from four examinations (calculated at ND ¼ 0). The concentrations were calculated on the basis of the original weights.
0.48 1.82 0.144
0.123–0.157
0.26 1.23 0.071
0.043–0.105
T. Tsutsumi et al. / Chemosphere 46 (2002) 1443–1449
samples except for one sample. OCDD and 3,30 ,4,40 TCB were generally found to be abundant in the samples. Also, the highly toxic isomers, 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD and 2,3,4,7,8-PeCDF, were detected in almost all the komatsuna and spinach samples. Although the samples had wide range of total TEQ levels, the vegetables can be ranked according to their mean total TEQ levels as follows: spinach > komatsuna > lettuce. The total TEQ levels in the komatsuna and spinach samples were similar to the values obtained from our previous report (Toyoda et al., 1999a). Fig. 1 shows the contribution of isomers in the total TEQ levels of the highest contaminated samples of each vegetable. The total TEQ levels are dominated by 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, 2,3,4,7,8-PeCDF and 3,30 ,4,40 ,5-PeCB (above 70% of each total TEQ level). The contribution patterns of the isomers were similar between the three kinds of vegetables, suggesting that these vegetables are contaminated by the same kind of
1447
pollution sources. It is well known that the PCDD/F contamination in leafy vegetables is mainly derived from environmental air (M€ uller et al., 1994, Smith and Jones, 2000). In fact, some of the dominant isomers, 1,2,3,7,8PeCDD, 2,3,4,7,8-PeCDF and 3,30 ,4,40 ,5-PeCB are also found to make an important contribution to the total TEQ in the environmental air (Lohmann and Jones, 1998, Shibayama et al., 2000). The outer leaves of lettuce are abundant in PCDD/Fs compared to the inner leaves, probably because the outer leaves are in more contact with the environmental air (H€ ulster and Marschner, 1993). However, in our study, the outer leaves were discarded from the analyzed samples before the sample preparation since they are inedible parts. Therefore, total TEQ levels of the lettuce samples are much lower than those of the komatsuna and spinach samples in most cases (Table 1). Fig. 2 shows a correlation between the total TEQ levels and TEQ levels of the dominant isomers in the
Table 3 Concentrations of PCDD/Fs and Co-PCBs in uncooked and cooked spinach samples from a supermarket (pg/g fresh weight)a Isomers
Cookedb
Uncooked Mean
Range
Washed
Washed and boiled
Mean
Range
Mean
Range
PCDDs
2,3,7,8-TCDD 1,2,3,7,8-PeCDD 1,2,3,4,7,8-HxCDD 1,2,3,6,7,8-HxCDD 1,2,3,7,8,9-HxCDD 1,2,3,4,6,7,8-HpCDD OCDD
0 0.04 0.01 0.04 0 0.46 5.44
ND 0.03–0.04 ND–0.03 0.03–0.05 ND 0.31–0.64 3.77–6.93
0 0.02 0.01 0.03 0.01 0.22 2.20
ND ND–0.03 ND–0.02 0.02–0.05 ND–0.04 0.19–0.26 1.73–2.52
0 0 0.01 0.01 0 0.11 1.12
ND ND ND–0.02 ND–0.02 ND 0.09–0.13 1.02–1.19
PCDFs
2,3,7,8-TCDF 1,2,3,7,8-PeCDF 2,3,4,7,8-PeCDF 1,2,3,4,7,8-HxCDF 1,2,3,6,7,8-HxCDF 1,2,3,7,8,9-HxCDF 2,3,4,6,7,8-HxCDF 1,2,3,4,6,7,8-HpCDF 1,2,3,4,7,8,9-HpCDF OCDF
0.07 0.07 0.04 0.05 0.05 0.01 0.04 0.16 0 0
0.06–0.08 0.05–0.10 0.03–0.05 0.04–0.06 0.03–0.06 ND–0.03 0.03–0.05 0.11–0.19 ND ND
0.07 0.06 0.03 0.04 0.04 0 0.03 0.11 0 0
0.06–0.08 0.06–0.07 0.03–0.03 0.03–0.04 0.03–0.05 ND 0.03–0.04 0.09–0.12 ND ND
0.04 0.04 0.01 0.01 0.01 0 0.01 0.04 0 0
0.03–0.05 0.03–0.06 ND–0.03 ND–0.02 ND–0.02 ND ND–0.02 ND–0.06 ND ND
Co-PCBs
3,30 ,4,40 -TCB 3,30 ,4,40 ,5-PeCB 3,30 ,4,40 ,5,50 -HxCB
0.73 0.12 0.04
0.65–0.78 0.11–0.13 0.03–0.04
0.63 0.11 0.03
0.55–0.73 0.09–0.15 0.02–0.03
0.46 0.07 0.02
0.37–0.62 0.05–0.09 ND–0.03
Total PCDDs (mean residue percent) Total PCDFs (mean residue percent) Total Co-PCBs (mean residue percent)
5.98
4.14–7.58 (100%) 0.35–0.59 (100%) 0.79–0.94 (100%)
2.48
2.01–2.83 (41%) 0.34–0.40 (77%) 0.67–0.91 (87%)
1.23
1.13–1.36 (21%) 0.12–0.24 (31%) 0.42–0.73 (61%)
Total TEQ
0.106
a b
0.48 0.89
0.082–0.122
0.37 0.77 0.070
Mean values were calculated from four examinations (calculated at ND ¼ 0). The concentrations were calculated on the basis of the original weights.
0.049–0.094
0.15 0.54 0.022
0.012–0.042
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T. Tsutsumi et al. / Chemosphere 46 (2002) 1443–1449
Fig. 3. TEQ levels reduction after the cooking processes in the spinach samples. Results represent mean SD of four examinations. The significance of the difference between each sample was assessed by student’s t-test. NS, not significant (p ¼ 0:052); , p < 0:05; , p < 0:01. The values in parentheses under X -axis indicate the mean residue percent of the total TEQ levels.
vegetables. In the correlation study, the present survey data along with previous survey data (Toyoda et al., 1999a), totally 35 samples (consisting of 14 komatsuna, 7 lettuce and 14 spinach samples), were analyzed. The 1,2,3,7,8-PeCDD, 2,3,4,7,8-PeCDF or 3,30 ,4,40 ,5-PeCB TEQ levels correlated well with the total TEQ levels. Especially, we found a strong correlation (r ¼ 0:957) between the total and 2,3,4,7,8-PeCDF TEQ levels in the vegetables. This result suggests that this isomer would be applicable as an indicator for dioxin contamination in the analysis of leafy vegetables. Next, we investigated the effects of the cooking processes on the PCDD/F and Co-PCB levels in two types of spinach samples. Two cooking processes, washing and washing followed by boiling, were examined. Tables 2 and 3 show the concentrations of the PCDD/Fs and Co-PCBs in the uncooked and cooked spinach samples from a private vegetable garden and supermarket. Since the sample’s weight changes during the processing, the concentrations in the cooked samples were calculated on the basis of the original weights. In both samples, the concentrations of many of the isomers decreased by the washing and boiling processes. On average, in both samples, the total concentrations of the PCDDs, PCDFs and Co-PCBs were reduced to 38%, 73% and 88% of the initial concentrations by washing, and to 21%, 35% and 61% of the initial concentrations by washing followed by boiling, respectively. Especially, washing followed by the boiling process effectively reduced the concentrations of almost all the isomers in both samples. Fig. 3 shows the reduction of the TEQ levels by the cooking processes in the two types of spinach samples. On average, in both samples, the total TEQ levels were reduced to about 70% of the initial TEQ levels by washing, and to about 30% of the initial TEQ levels by
washing followed by boiling. Significant reductions in the total TEQ levels were observed in most of the cooked samples. Thus, the cooking processes can possibly reduce the risk of dioxin intake from the leafy vegetables. The reduction of PCDD/Fs and Co-PCBs appears to be mainly due to the exclusion of particlebound dioxins from the spinach surface by washing and boiling, although we cannot determine the reduction mechanisms in the present experiment. In this study, we focused on leafy vegetables because of the limited information regarding the PCDD/F and Co-PCB levels. But, recently in Japan, about 60% of the dietary intake of dioxins is likely to come from the intake of fish and shellfish (Toyoda et al., 1999b). Therefore, a detailed investigation of the effects of various cooking processes on their levels in fish and shellfish is strongly needed to accurately estimate the intake of dioxins through diet.
Acknowledgements A part of this work was supported by a Health Sciences Research Grants from the Ministry of Health, Labour and Welfare, Japan.
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