Environ. Sci. Technol. 2010, 44, 2870–2875
Current Exposure to Persistent Polychlorinated Biphenyls (PCBs) and Dichlorodiphenyldichloroethylene (p,p′-DDE) of Belgian Students from Food and Dust†
for p,p′-DDE in the studied population. Food intake contributed more than 99% of the combined PCB intake from food and dust. No significant positive correlations (p > 0.05) were observed between the serum concentrations of PCBs and p,p′-DDE and the total intake through food and dust for each participant. Instead, it is hypothesized that past and episodic higher current intakes are more important determinants of body burden than continuous background exposures at low levels.
LAURENCE ROOSENS,‡ M O H A M E D A B O U - E L W A F A A B D A L L A H , §,| STUART HARRAD,§ HUGO NEELS,‡ AND A D R I A N C O V A C I * ,‡,⊥ Toxicological Centre, Department of Pharmaceutical Sciences, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium, Division of Environmental Health and Risk Management, Public Health Building, School of Geography, Earth, and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, United Kingdom, Department of Analytical Chemistry, Faculty of Pharmacy, Assiut University, 71526 Assiut, Egypt, and Laboratory for Ecophysiology, Biochemistry and Toxicology, Department of Biology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
Introduction
Received July 17, 2009. Revised manuscript received August 16, 2009. Accepted August 21, 2009.
Human exposure to individual polychlorinated biphenyl (PCB) congeners and dichloro-diphenyldichloroethylene (p,p′DDE) through food (duplicate diets) and indoor dust ingestion was assessed for 19 Belgian students. The serum concentrations of the persistent PCB congeners in serum (PCB 118, 138, 153, 170, and 180) have been correlated with the individual intake through food and dust. Dietary intakes of ΣPCBs ranged between 40 and 204 ng/day (median 133). PCB exposure through dust ingestion ranged between 0.1 and 0.8 ng/day (median 0.3) or 0.3 and 1.7 ng/day (median 0.8), assuming average dust ingestion (20 mg/day) and high dust ingestion rates (50 mg/ day), respectively. Dietary intake of p,p′-DDE was comparable to that of PCBs with a range from 21 to 214 ng/day (median 92). The exposure to p,p′-DDE via dust ingestion ranged between 0.02 and 0.43 ng/day (median 0.17) or 0.05 and 1.09 ng/day (median 0.43), assuming average and high dust ingestion rates, respectively. Concentrations measured in blood serum were 28-153 ng/g lipid weight (lw) (median 74) and 32-264 ng/g lw (median 45) for ΣPCBs and p,p′-DDE, respectively. Serum concentrations in the studied population are slightly lower compared to other European populations. In spite of the uncertainty associated with the dust ingestion rates, food was the predominant exposure pathway for each PCB congener and * Corresponding author fax: +32 3 265 2722; e-mail:
[email protected]. † Part of the special section “Sources, Exposures, and Toxicities of PCBs in Humans and the Environment”. ‡ Toxicological Centre, Department of Pharmaceutical Sciences, University of Antwerp. § University of Birmingham. | Assiut University. ⊥ Laboratory for Ecophysiology, Biochemistry and Toxicology, Department of Biology, University of Antwerp. 2870
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 44, NO. 8, 2010
Polychlorinated biphenyls (PCBs) are heat-resistant, oily liquids, used in a variety of applications, such as insulating fluids in transformers and capacitors (1). Although production in western industrialized countries ended in the late 1970s, their considerable use during the past two decades, combined with their resistance to degradation and environmental mobility, has led to their ongoing detection in humans and wildlife (1, 2). Dichlorodiphenyldichloroethylene (p,p′-DDE) is the principal metabolite of DDT, a broad-spectrum insecticide that has been used to protect agricultural crops and control insect-borne diseases (3). Due to alarming reports concerning its reproductive effects and persistence in the environment, the use of DDT has been banned since 1972 in most developed countries (1), although its use is still permissible in some developing countries where it remains effective for malaria vector control (4). Shared characteristics such as their widespread usage, persistence in the environment, lipophilicity, and accumulation throughout the food web have made PCBs and DDE important global pollutants that can be found primarily in lipid-rich food of animal origin, such as meat, fish, and dairy products (5, 6). Successful regulatory intervention has led to decreasing human exposure to these substances over the past 30 years (7-9). Although attention has shifted toward other persistent organic compounds, such as polybrominated diphenyl ethers (PBDEs) and hexabromocyclodecanes (HBCDs), monitoring of organochlorinated contaminants remains justified due to recent indications that the initial rapid decline in environmental contamination is leveling off (10). Recent publications indicate that PCBs which remain present in buildings, in applications such as paint (11) and construction sealants (12), are still entering the environment. Such emissions lead to ongoing exposure, both directly via contamination of indoor air (13) and dust (14), and indirectly via driving outdoor air contamination (15, 16) thereby maintaining dietary exposure following incorporation into the food chain (17). This hypothesis is supported by the fact that after a 50% decline between 1982 and 1992, UK dietary exposure to nondioxin-like PCBs has shown no further decline between 1992 and 2001 (10). Furthermore, the long human half-lives (3-9 yrs) of persistent PCBs (18, 19) lead to body burdens reflecting past exposure for some time. While dietary exposure has been generally recognized as the most important source to PCBs and DDT (5, 6, 14, 17), there is still little knowledge on the influence of combined exposure sources (diet and dust) for background exposed populations. The objective of this study was to determine the current human exposure via diet and indoor dust ingestion of 19 background-exposed Belgian students to ΣPCBs and p,p′DDE, and the influence of such contemporary combined exposure on the individual serum concentrations. Furthermore, the relative contributions of exposure via dietary intake and dust ingestion were assessed on a congener specific basis for the most persistent congeners in serum (PCB 118, 138, 153, 170, and 180) (18, 19). Only these congeners were 10.1021/es9021427
2010 American Chemical Society
Published on Web 09/09/2009
monitored in order to correlate concentrations with those found in dust and food. However, we want to stress that other congeners (e.g., PCB 28, 52, and 101) might be prevalent in dust and thus might alter the relationships. Finally, the present study adds to the scant literature database on PCB exposure via ingestion of indoor dust.
Materials and Methods Participants. Nineteen students (8 males and 11 females aged between 20 and 25 years, Table SI-1) residing in university housing (student’s room, e.g., no division in living, bedroom, kitchen) were recruited. The study was approved by the Ethics Committee of the University of Antwerp. To minimize confounding due to previous exposures, participants were required to have resided in university housing for at least three years prior to the study. Each participant completed a questionnaire providing lifestyle information such as smoking and transportation habits. A detailed description of sample collection was given in Roosens et al. (20, 21) and is presented in the Supporting Information (SI). Sample Analysis. Full information and details on the procedures followed are given in the SI, however, brief summaries are provided here. The method used for the analysis of food is based on that described previously by Voorspoels et al. (6, 22). An accurately weighed aliquot (3-8 g) of the freeze-dried sample was spiked with internal standard (10 ng of PCB-143) and Soxhlet extracted. An aliquot of the extract was used for gravimetric lipid determination, while the rest was purified via acid silica cartridges. For dust, internal standard (10 ng of PCB-143) was added to an accurately weighed quantity of dust (typically 0.2 g) followed by Soxhlet extraction and purification as described previously (23). Preparation, extraction, and cleanup of serum samples are as described by Covaci and Voorspoels (24), but are summarized as follows: internal standard (10 ng of PCB-143) was added; samples were mixed with formic acid for protein denaturation and diluted. After sample loading onto OASIS HLB cartridges, PCBs and p,p′-DDE were eluted with dichloromethane and purified further on acid silica cartridges. All purified extracts were evaporated to dryness and dissolved in 100 µL of iso-octane prior to GC/ECNI-MS analysis. Quality control was achieved by regular analysis of procedural blanks and certified materials, and through regular participation in interlaboratory comparison exercises for matrices, such as serum and biological samples (see SI, Tables SI-2-4). For each analyte, the mean procedural blank value was used for subtraction. After blank subtraction, the limit of quantification (LOQ) was set at 3 times the standard deviation of the procedural blank, which ensures >99% certainty that the reported value originated from the sample. LOQs in food were 4-43 pg/g wet weight (ww) for individual PCB congeners and 17 pg/g ww for p,p′-DDE. Those in serum were 0.2-1.7 ng/g lipid weight (lw) for individual PCBs and 8 ng/g lw for p,p′-DDE, whereas those in dust were 0.2-1.1 ng/g dry weight (dw) and 2 ng/g dw for PCB congeners and p,p′-DDE, respectively. Concentrations below LOQ were reported as f*LOQ with f being the fraction of samples above LOQ. Statistical Analysis. PCB and p,p′-DDE concentrations in food, dust, and serum were checked for outliers using boxplots. Correlation analysis was performed using Graphpad Instat 3.
Results and Discussion Profiles and Concentrations of PCBs and p,p′-DDE in Food, Dust, and Serum. Food. The most abundant PCB congeners include PCB138-153 > 118 > 180 > 170 with PCB 138 and PCB 153 as the major contributing congeners to ΣPCBs in most samples after f*LOQ correction (Figure SI-1). Similar PCB profiles have been observed in Belgian food and fish,
with PCB 153 as most abundant congener and notable contributions of PCB 138 and PCB 180 (22, 25). This order is due to the lower persistence and higher volatility of lower chlorinated PCBs (tri- and tetra-PCBs) compared to their higher chlorinated counterparts (penta- to octa-PCBs). Therefore, higher chlorinated PCBs are more likely to accumulate in biotic and abiotic matrices, whereas lower chlorinated PCBs are degraded and partition more easily to air (26). Concentrations of ΣPCBs in duplicate diet samples ranged between 6 and 1110 pg/g ww with a median value of 104 pg/g ww. These concentrations are lower compared to an earlier Belgian market basket study which reported medium bound concentrations of ΣPCBs between 620 and 7100 pg/g ww in fish, meat, and dairy products (6). In another study (27), low PCB concentrations in Belgian foodstuffs (salmon, butter, and cabbage) have been reported previously, with mean ΣPCBs levels in Italian, Spanish, and Portugese food items 5 times higher compared to Belgian samples. The congener contribution to ΣPCBs was variable between food groups, as cabbage and salmon showed a high contribution of lower chlorinated congeners (27). A UK study reported higher PCB levels in food items with ΣPCBs in various food groups ranging from 110 to 4640 pg/g ww in 1982 and between 57 and 3830 pg/g ww in 2001 (10). Yet, the PCB congeners representing ΣPCBs in the various studies were not identical, thus impairing direct comparison between contamination levels. Concentrations of p,p′-DDE in food ranged between 1 and 9477 pg/g ww (median 41 pg/g ww). Median p,p′-DDE levels in most food samples were lower than ΣPCBs levels, although one meal (ham, potatoes, and broccoli) contained a p,p′-DDE peak concentration of 9477 pg/g ww. Discarding this outlying value, the resulting p,p′-DDE range of 1-2366 pg/g ww is lower compared to other European studies with levels up to 4690 pg/g ww and 5675 pg/g ww (5, 28). The lower contents of ΣPCB and p,p′-DDE in the current food items might be due to differences between duplicate diet and market basket results, as market basket studies do not always account for the potential decrease in POP content caused by food preparation techniques, such as broiling. Moreover, market-basket studies often do not include plantbased comestibles, which contain lower concentrations of PCBs and p,p′-DDE (5), but instead focus on fatty products, such as meat and fish. Table 1 summarizes the descriptive statistics for the present and related studies. Dust. Recently, dust ingestion has been receiving increasing attention as a potentially significant human exposure route to persistent organic chemicals, due to the high proportion of time spent indoors and elevated contaminant concentrations in the indoor environment. While most recent attention has focused on such exposure to brominated flame retardants (29-31), some examination has been made of its significance for PCBs (3, 14). Concentrations of ΣPCBs in dust ranged between 6.5 and 41.9 ng/g dw (median value of 17.2 ng/g dw) with no outliers detected. Levels are considerably lower compared to PCB concentrations detected in the U.S., Canada, UK, and even New Zealand (14) (Table 1). This is not surprising, as similar conclusions were made recently for PBDEs (20). The dust samples of the present study were characterized by a high detection frequency of all persistent PCB congeners, with PCB 138 and PCB 153 contributing most to the ΣPCBs content in every sample (Figure SI-2). Indoor dust from Singapore (3) showed a different profile as PCB 101 was both the most frequently detected (25/31 samples) and abundant (median, 0.5 ng/g dust) congener, followed by PCB 153. However, levels of ΣPCBs in Singapore dust were comparable to those reported in the current study (Table 1). A higher contribution of penta- and hexa-chlorinated congeners such as PCB 101, 138, and 153 points toward the past usage of Aroclor 1254, VOL. 44, NO. 8, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
2871
TABLE 1. Descriptive Statistics of ΣPCBs and p,p′-DDE Concentrations in Food (pg/g ww), Dust (ng/g dw), and Serum (ng/g lw) from the Present and Related Studies country
compounds
median
average
SD
range
104 41 -
179 191 14.4 52.3 50.0 41.5 -
184 766 7.0 16.1 13.8 16.2 -
6-1110 1-9477 620-7100 ND-4690 122-1420 71-5675
ΣPCBa pp-DDE ΣPCBsd pp-DDE ΣPCBse pp-DDE pp-DDE ΣPCBsf
17.2 8.4 38.0 7.1 5.6 3.3 5.5 200 260 46 48
19.7 8.4 116.1 7.0 9.2 5.9 220 290 67 110
9.4 5.5 171.7 5.0 11 10 -
6.5-41.9 1.0-21.7
