Environ. Sci. Technol. 2003, 37, 2332-2335
Polychlorinated Naphthalenes in Foods: Estimated Dietary Intake by the Population of Catalonia, Spain J O S E L . D O M I N G O , * ,† G E M M A F A L C O Ä ,‡ J U A N M . L L O B E T , †,‡ C O N R A D C A S A S , § ANGEL TEIXIDO Ä ,§ AND LUTZ MU ¨ LLER| Laboratory of Toxicology and Environmental Health, “Rovira i Virgili” University, San Lorenzo 21, 43201 Reus, Spain, Toxicology Unit, School of Pharmacy, University of Barcelona, 08028 Barcelona, Spain, Department of Health and Social Security, Generalitat de Catalunya, 08028 Barcelona, Spain, and Department of Analytical Laboratory, MPU GmbH, 10829 Berlin, Germany
Concentrations of polychlorinated naphthalenes (PCNs) were measured in foodstuffs randomly acquired in seven cities of Catalonia, Spain. A total of 108 samples, belonging to 11 food groups (vegetables, tubers, fruits, cereals, pulses, fish and shellfish, meat and meat products, eggs, milk, dairy products, and oils and fats), were analyzed by highresolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS). The levels of tetra-, penta-, hexa-, and hepta-CNs, those of octachloronaphthalene, and the mean sum concentration of tetra-octa-CN were determined. The highest concentration of total PCNs was found in oils and fats (447 pg/g), followed by cereals (71 pg/g), fish and shellfish (39 pg/g), and dairy products (36 pg/g). In general, tetra-CN was the predominant homologue in all food groups except for fruits and pulses, which had greater proportions of hexa-CNs. The dietary intake of total PCNs was subsequently determined. For calculations, recent data on consumption of the selected food items were used. Intake of PCNs was estimated for five population groups of Catalonia: children, adolescents, male and female adults, and seniors. When the dietary intake of total PCNs was expressed in nanogram per kilogram of body weight per day, it was age-dependent, with the highest and lowest values corresponding to children (1.65) and seniors (0.54), respectively. The largest contribution to the daily PCNs intake came from oils and fats and from cereals. The result of the current study is the first published report concerning human exposure to PCNs through the diet.
Introduction During the preparation of the UN-ECE POP Protocol of 1998, many of the substances suggested by the member states were not included because of a lack of adequate information (1). Although this Protocol obligues parties to reduce only the emissions of dioxins and furans (PCDD/Fs), polycyclic aromatic hydrocarbons (PAHs) and hexachlorobenzene * Corresponding author telephone: +34-977-759380; fax: +34977-759322; e-mail:
[email protected]. † “Rovira i Virgili” University. ‡ University of Barcelona. § Generalitat de Catalunya. | MPU GmbH. 2332
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(HCB) at levels below those of 1990, parties can propose amendments to add new substances to the Protocol. Recently, due to their toxicological profile and the fact that they are long-range-transported chemicals in air, polychlorinated naphthalenes (PCNs) were also selected as a candidate for the UN-ECE POP Protocol (1). PCNs are a group of compounds containing from one to eight chlorine atoms per naphthalene (two fused benzene rings) molecule, which form a total of 75 possible congeners (2). PCNs are planar substances with physical and chemical properties similar to those of polychlorinated biphenyls (PCBs) (2, 3). These compounds have been used in similar applications as PCBs: dielectric fluids, engine oil additives, cable insulation, wood preservation, etc. (2-4). Although the United States voluntarily ceased PCNs production in 1980, these substances are not prohibited in a great number of countries (5). Consequently, they are still released to the environment via technical PCBs formulations, thermal and other processes in the presence of chlorine, and landfills, which are also potentially a large source of PCNs because of the historical use pattern (1, 2). De novo syntheses mechanisms for PCN formation and emission from municipal waste incinerators were also recently reported (6). As with other polychlorinated diaromatic hydrocarbons, the major mechanism of action for the toxicity of PCNs is related to their ability to bind to and activate the aryl receptor (AhR) (7). Several of the PCNs congeners display toxicity similar to that of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) through the AhR-mediated mechanisms. These include induction of aryl hydrocarbon hydroxylase, ethoxyresorufin O-deethylase (EROD), chloracne, and hepatic damage (3, 7, 8). Recently, relative potencies (relative to TCDD) of hexachlorinated naphthalenes, the most potent PCNs congeners tested, were found to be around 10-3 followed by penta-CNs yielding relative potencies between 10-3 and 10-7 (7, 9). In general, TEQ contributions of PCNs have been found to be 3-6 orders of magnitude less potent than TCDD and similar to the relative potency of many PCBs congeners (7, 9-11). Although prior to 1975 there were very few reports on levels of PCNs in environmental samples, in recent years a number of studies have detected these chemicals in air, water, soils, sediments, and biota (4, 8-13) as well as in human blood, milk, and adipose tissue (3, 14, 15). Despite the toxicological and environmental similarities between PCNs and pollutants such as PCDD/Fs and PCBs, there is a paucity of information on human levels of PCNs. In turn, to the best of our knowledge, to date there is no any published report on the dietary intake of PCNs. As for other lipophilic persistent organochlorine compounds, it is expected that for the general population food is the main source of exposure to PCNs. The objective of the present study was to determine the concentrations of PCNs in food samples collected in various cities of Catalonia (Spain) and to estimate exposure to PCNs through the diet of the general population of this region.
Materials and Methods Sampling. From June to August 2000, food samples were randomly obtained in local markets, big supermarkets, and grocery stores from seven cities (Barcelona, Tarragona, Lleida, Girona, L’Hospitalet de Llobregat, Badalona, and Terrassa) of Catalonia, which have populations between 150 000 and 1 800 000 inhabitants. For collection of samples, two groups were made up. The first group included meat of beef (steak, hamburger), pork (loin, sausage), chicken (breast), and lamb (steak); fish (hake, sardine) and shellfish (mussel); vegetables 10.1021/es030009b CCC: $25.00
2003 American Chemical Society Published on Web 04/17/2003
TABLE 1. Mean Concentrations (pg/g wet wt) of Polychlorinated Naphthalenes (PCNs) in Food Samples from Catalonia, Spaina meat and meat products (n ) 30) fish and shellfish (n ) 16) vegetables (n ) 16) tubers (n ) 4) fruits (n ) 12) eggs (n ) 4) milk (n ) 4) dairy products (n ) 4) cereals (n ) 8) pulses (n ) 4) oils and fats (n ) 6)
∑tetra-CNs
∑penta-CNs
∑hexa-CNs
∑hepta-CNs
OCN
∑PCNs (tetra-octa)
10 15 2 1 0.1 13 0.05 29 27 0.6 377
5 16 0.9 0.9 0.2 6 0.05 5 20 0.9 58
2 7 0.6 0.6 0.2 3 0.05 1 21 1 7
0.4 0.9 0.1 0.2 0.1 0.4 0.1 0.7 2 0.2 4
0.3 0.3 0.1 0.2 0.1 0.2 0.1 0.4 0.9 0.2 1
18 39 4 3 0.7 23 0.4 36 71 3 447
a For each food group, the number of composite samples is given in parentheses. Undetectable concentrations were assumed to be equal to one-half of the respective detection levels: 1 pg/g (dry wt) for tetra-, penta-, and hexa-CNs and 2 pg/g (dry wt) for hepta-CNs and OCN.
and tubers (lettuce, tomato, potato, green beans, cauliflower); fresh fruits (apple, orange, pear); and eggs. The second group included cow milk (whole, semi-skimmed) and dairy products (yogurt, cheese); cereals (bread, pasta, rice); pulses (lentils, beans); fats (margarine) and oils (olive, sunflower); tinned fish (tuna, sardine); and meat products (ham, hot dogs, salami). Because in the first group most products are usually retailed, their origins could be very diversified in the different cities. Therefore, in that group four composite samples were analyzed for each food item. Each composite was made up of 10 individual samples. In contrast, most food items included in the second group corresponded to brands/ trademarks that could be obtained in many different places. Consequently, in this group only two composite samples were analyzed for each food item. Each composite was made up of 8 individual samples. A total of 108 samples were analyzed. The sums of the tetra-octachlorinated congeners were determined. Chemical Analysis. Food samples were homogenized and blended using a domestic mixer. Composite samples were liophilized previously to analyses of PCNs, which were performed in accordance to the U.S. EPA 1625 method (semivolatile organic compounds by isotope dilution GC/ MS). Prior to extraction, dried samples were homogenized. A total of 5-10 g of the freeze-dried solid samples was mixed with a small amount of Na2SO4 and spiked with a mixture of 13C12-marked standards. Samples were extracted for 24 h with the following organic solvents (Soxhlet extraction): toluene for vegetables, fruits, cereals, eggs, milk, and dairy products; hexane/dichloromethane (1:1) for meat, fresh fish, and mussels; and petrol ether for fish in oil. For oil and margarine, 2 g of the sample was dissolved in hexane and immediately used for the cleanup procedure. The cleanup procedure and fractionation of the sample aliquot was carried out as a multiple cleanup using adsorption chromatography, a multilayer silica column (from top to bottom: sodium sulfate, silica, silica-sulfuric acid, silica, silica-potassium hydroxide, silica), alumina columns, and gel permeation columns (BioBeads SX3). The final step involved the reduction of the PCN-containing fractions to the volume necessary for the analysis. Prior to PCN analysis, a 13C-labeled standard was added for calculation of recovery ratios. The cleaned extract was analyzed by HRGC/HRMS (a Fisons CE 800 gas chromatograph coupled with a VG Autospec Ultima system with electronic impact and a multiple ion detection mode [with a resolution of g10 000]). A DBXLB column was used. Internal standards were used for PCNs quantification. Mean recovery rates ranged from 80% (58116%) for octa-CN to 85% (55-113%) for tetra-CNs. Detection levels were 1 pg/g (dry wt) for tetra-, penta-, and hexa-CNs and 2 pg/g (dry wt) for hepta-CNs and octa-CN. Average daily consumption data were obtained from recent studies carried out in Catalonia (16, 17). PCNs intake
was estimated for each food group assuming that undetectable concentrations were equal to one-half of the limit of detection.
Results and Discussion The concentrations of PCNs in food samples acquired in various locations of Catalonia are summarized in Table 1. Results (wet wt) show the mean sum levels of tetra-, penta-, hexa-, and hepta-CNs, the levels of octachloronaphthalene, and the mean sum concentration of tetra-octa-CNs. Data are given for 11 food groups. The highest concentration of total PCNs was found in oils and fats (447 pg/g), followed at a notable distance by cereals (71 pg/g), fish and shellfish (39 pg/g), and dairy products (36 pg/g). In contrast, milk (0.4 pg/g) and fruits (0.7 pg/g) followed by tubers (3 pg/g) and vegetables (4 pg/g) were the groups showing the lowest concentrations of total PCNs. In general, tetra-CNs were the predominant homologue in all food groups except for fruits and pulses, which had greater proportions of hexa-CNs. In fish and shellfish, the proportion of tetra- and penta-CNs was similar, while in all food groups the lowest quantities of PCNs corresponded to octachloronaphthalene. Table 2 shows data on food intake and dietary intake of PCNs (11 food groups) for children, adolescents, male and female adults, and seniors living in Catalonia. Total daily intake of PCNs is given in nanograms per day (ng/d) and nanograms per kilograms of body weight per day (ng kg-1 d-1). When the dietary intake of total PCNs was expressed in nanograms per day, the decreasing ranking was the following: male adults (45.78), adolescents (43.32), children (39.68), female adults (33.98), and seniors (33.62). However, when the dietary intake of total PCNs was expressed in nanograms per kilograms of body weight per day, the decreasing ranking was then age-dependent, with the highest and lowest intake corresponding to children (1.65) and seniors (0.54), respectively (Figure 1). This divergence can be explained taking into account the differences in mean body weight of each group as well as in the dietary habits corresponding to each age group (16, 17). For example, seniors is the group consuming the lowest quantities of oils and fats, and cereals, which are also the food groups with the highest contribution to total intake of PCNs (Table 1). As it has been stated in Introduction, this is the first report on dietary intake of PCNs by a general population. Moreover, data on PCNs concentrations in food samples are very scarce, most of them exclusively referred to aquatic species. Therefore, although the estimated current daily intakes of PCNs cannot be compared with results of other surveys, it is possible to compare the current PCNs levels in fish and shellfish with data from previous investigations on PCNs levels in marine/ freshwater species. A summary of recent results is shown in Table 3. When expressed on a wet weight basis, the VOL. 37, NO. 11, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 2. Food Intake (g/d) and Estimated Intake of PCNs through the Diet of Children, Adolescents, Male and Female Adults, and Seniors in Catalonia, Spaina children (24 kg)
vegetables pulses cereals tubers fruits fish and shellfish meat and meat products eggs dairy products milk oils and fats ng/d ng kg-1 d-1 a
adolescents (54.5 kg)
male adults (70 kg)
female adults (55 kg)
g of food/d
ng/d
g of food/d
ng/d
g of food/d
ng/d
g of food/d
ng/d
g of food/d
ng/d
125 26 201 64 196 52 140 27 114 309 34
0.42 0.09 14.28 0.18 0.14 2.05 2.46 0.63 4.10 0.11 15.20
163 24 221 77 202 62 167 26 123 267 36
0.55 0.08 15.70 0.22 0.14 2.45 2.94 0.61 4.43 0.10 16.10
226 24 206 74 239 92 185 34 106 217 41
0.76 0.08 14.64 0.21 0.17 3.63 3.25 0.80 3.82 0.08 18.33
202 23 139 57 227 80 125 24 92 254 31
0.68 0.08 9.81 0.16 0.16 3.12 2.20 0.54 3.28 0.09 13.86
190 22 157 70 268 80 114 23 72 254 29
0.64 0.07 11.16 0.20 0.19 3.16 2.01 0.54 2.59 0.09 12.97
39.68 1.65
43.32 0.79
45.78 0.65
seniors (62 kg)
33.98 0.62
33.62 0.54
The average body weight of each group is given in parentheses.
TABLE 3. Polychlorinated Naphthalenes (PCNs) in Marine Species: Summary of Recent Results total PCNs (pg/g) species
wet wt
lipid wt
herring, porpoises
29 000 1700-2800 (110/320) × 103 (6.3-260) × 103 (346-20 880) × 103
mussel/crab, fish Baltic salmon porpoises (tissues) fishes herring gulls, eggs of cormorants various speciesa (Raisin River, USA) various speciesb
22-682 19-31 400 83-1300 380-2400 40.7-22 610 39
a
Largemouth and smallmouth bass, round goby, and zebra mussel were analyzed. sardine were analyzed.
673 b
ref
20 13 21 18 11 8 19 this study
Fresh hake, sardine, and mussel and tinned tuna and
fishes from the Gdansk Basin (Baltic Sea) and by Akerblom et al. (21) in juvenile Baltic salmon.
FIGURE 1. Estimated daily intake of PCNs through the diet of children, adolescents, male and female adults, and seniors in Catalonia, Spain. concentration of the total PCNs in fish and shellfish found in the present study was in the low part of the range reported by Kannan et al. (11), 19-31 400 pg/g in fishes from Michigan waters, and by Ishaq et al. (18), 22-682 pg/g in tissues of harbor porpoises from Swedish waters. However, the levels detected in the current survey were notably lower than those found by Kannan et al. (8) in eggs of cormorants (380-24 000 pg/g) and herring gulls (83-1300) from Michigan waters of the Great Lakes. The current results are very similar to the levels of total PCNs observed in smallmouth bass (40.7 pg/g) from the Raisin River (MI) (19). When expressed on a lipid weight basis, the present concentrations of total PCNs were remarkably lower than those reported in herring and porpoises from the southern part of the Baltic proper (20) and remarkably lower than the levels found by Falandysz et al. (13) in mussels, crab, and 2334
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With respect to the dominating congener profiles, tetraand penta-CNs with approximately 39% each were the most contributing groups to total PCNs in the fish and shellfish samples of the present study (Table 1). Despite the different species analyzed as well as geographically very distant and unrelated sampling sites, the current profiles are similar to those reported by Falandysz and Rappe (20), Falandysz et al. (13), Kannan et al. (11), and Hanari et al. (19). By contrast, in the studies by Akerblom et al. (21) and Ishaq et al. (18), hexa-CNs were the most contributing group to total PCNs found in juvenile Baltic salmon and tissues of porpoises, respectively. In relation to the toxic potential of PCNs intake through the diet, it should be taken into account that a number of PCNs congeners exhibit Ah-receptor-mediated cytochrome P450 induction analogous to TCDD (8, 11). Although on the basis of in vitro bioassays, toxic equivalency factors (TEFs) and/or relative potencies (REPs) have been reported for several PCNs congeners (7, 9), since TEFs or REPs are not available for all congeners, in the present study TEQs corresponding to total PCNs were not determined. With regard specifically to aquatic species, in a recent study on PCNs, PCBs, and PCDD/Fs in double-crested cormorants and herring gulls from Michigan waters of the Great Lakes, Kannan et al. (8) reported that contribution of PCNs to TEQs was 2-3% of the total TEQs, which was notably lower than those corresponding to PCBs and PCDD/Fs. Although this result suggests that the toxic impact of PCNs
might be relatively more localized than those of PCBs and PCDD/Fs, the authors concluded that fish from certain areas of contamination could be exposed to great concentrations of PCNs resulting in their contribution to TEQs overwhelming those due to PCBs or PCDD/Fs (8). In a previous study carried out by the same investigators (11), the contributions of PCBs and PCNs to the sum of TEQs were 86% (43-98%) and 14% (2-57%), respectively, in fishes from the Michigan waters. Recently, we determined the levels of PCBs in food samples and estimated exposure to PCBs through the diet of the population of Catalonia (22). The highest concentrations of PCBs were found in fish and shellfish (11 864.18 pg/g wet wt), a value that would correspond to an intake of PCBs of 82.57 pg of WHO-TEQ/d. The concentration of total PCNs in fish and shellfish found in the current study (39 pg/g wet wt) is approximately 300-fold lower than that of total PCBs (22). Taking this into account and according to the results of the studies of Kannan et al. (8, 11), the current contribution of total PCNs to the ∑TEQs should be lower than that of PCBs. As the occurrence of PCNs in foodstuffs has not been previously investigated and the contribution of PCNs to the ∑TEQs may be great enough to be of concern in industrialized countries, further studies to determine the concentrations of PCNs in food samples and the dietary intake by the general population of a number of countries are clearly necessary.
Acknowledgments We thank the Department of Health and Social Security, Generalitat de Catalunya, Spain, for funding the study and Mrs. A. Aguilar and Mrs. A. Diez for skillful technical assistance.
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Received for review January 15, 2003. Revised manuscript received March 15, 2003. Accepted March 25, 2003. ES030009B
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