Environ. Sci. Technol. 2000, 34, 1615-1619
Levels of C10-C13 Polychloro-n-Alkanes in Marine Mammals from the Arctic and the St. Lawrence River Estuary G R E G G T . T O M Y , * ,† D E R E K C . G . M U I R , ‡ GARY A. STERN,† AND JOHN B. WESTMORE§ Department of Fisheries and Oceans, Freshwater Institute, Winnipeg, Manitoba R3T 2N6 Canada, National Water Research Institute, Environment Canada, Burlington, Ontario L7R 4A6, Canada, and Department of Chemistry, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
Marine mammals from various regions of the Arctic and the St. Lawrence River estuary were examined for the first time for levels of C10-C13 polychloro-n-alkanes (sPCAs). Respective mean total sPCA concentrations in the blubber of beluga whales (Delphinapterus leucas) from Saqqaq and Nuussuaq, western Greenland, were 0.23 ( 0.02 (n ) 2) and 0.164 ( 0.06 µg/g (n ) 2), similar to that in beluga from the Mackenzie Delta in the western Canadian Arctic 0.21 ( 0.08 µg/g (n ) 3). sPCAs levels were higher in beluga blubber from the St. Lawrence River (0.37 to 1.4 µg/g). Mean sPCA concentrations in the blubber samples from walruses (Odobenus rosmarus) (Thule, northwest Greenland) and ringed seal (Phoca hispida) (Eureka, southwest Ellesmere Island) were 0.43 ( 0.06 (n ) 2) and 0.53 ( 0.2 µg/g (n ) 6), respectively. Relative to commercial sPCA formulations, samples from the Arctic marine mammals showed a predominance of the shorter chain length lower percent chlorinated PCA congeners, the more volatile components of industrial formulations. This observation is consistent with long-range atmospheric transport of sPCAs to this region. The profiles of the belugas from the St. Lawrence River estuary, however, had higher proportions of the less volatile sPCA congeners, implying that contamination to this region is probably from local sources.
Introduction Polychloro-n-alkanes (PCAs), or chlorinated paraffins, are primarily industrial chemicals consisting of C10-C30 and chlorine content from 30 to 70% by mass. Their high thermal stability and chemical inertness favor their use in a wide variety of consumer products and industrial processes that demand chemical stability (1). Some common uses of PCAs, which first began during World War I where they were used in the preparation of an antiseptic solution (2), include use as high-temperature lubricants in metal-working machinery and in flame retardant plasticizers; more limited applications include use in adhesives, paints, rubber, and sealants (3-6). * Corresponding author phone: (204)984-2532; fax: (204)984-2403; e-mail:
[email protected]. † Freshwater Institute. ‡ National Water Research Institute. § University of Manitoba. 10.1021/es990976f CCC: $19.00 Published on Web 03/17/2000
2000 American Chemical Society
Industrially, PCAs are synthesized by direct chlorination, with molecular chlorine, of n-alkanes in the presence of UVlight (4). Because the principal n-alkane feedstocks used are mixtures, their chlorinated analogues are complex formulations consisting of optical isomers and congeners (2). Commercial PCA formulations fall into three categories: C10C13 (short), C14-C17 (medium), and C20-C30 (long). Depending on the extent of chlorination, mixtures are further subcategorized into their weight content of chlorine: 40-50%, 5060% and 60-70% (3). The C10-C13 PCAs (sPCAs) are of particular interest because they have the highest propensity for environmental release (3) and the highest toxicity of all the PCA products (2, 7, 8). Because sPCAs have similar chemical and physical properties (Kow, WS, and VPs) to many other persistent organic pollutants (POPs) (e.g., PCBs, DDT, and toxaphene) (9), it is not surprising, based on dietary studies on juvenile rainbow trout, that the highly chlorinated sPCAs have the greatest potential for bioaccumulation and biomagnification (10). Although global production of sPCAs has declined since the early 1980s (9), products containing their formulations are still present in the environment. In addition, because of their widespread and unrestricted use in open systems, sPCAs are now present in a range of environmental compartments (5, 9). Because of these concerns, sPCAs have been placed on the United States Environmental Protection Agency (EPA) Toxic Release Inventory and in Canada are under consideration as Track 1 Priority Toxic Substances under Canada’s Environmental Protection Act. In Europe, voluntary restrictions for sPCAs use have been implemented by industry. To date, there is still limited information regarding the environmental levels of sPCAs in aquatic biota. Even less is known about their levels in the Canadian Arctic and surrounding regions. In aquatic organisms in Sweden, however, Jansson et al. (11) reported sPCA concentrations (C10-C13, 60% Cl) ranging from 0.13 µg/g in ringed seal (Phoca hispida) blubber from Kongsfjorden to 1.6 µg/g in herring (Clupea harengus) from Skagerrak. sPCA concentrations (C10C13, 60% Cl) in whitefish (Coregonus sp.) (Lake Storvindeln), Arctic char (Salvelinus alpinus) (Lake Va¨ttern), and gray seal (Halichoerus grypus) blubber (Baltic Sea) were 1, 0.57, and 0.28 µg/g, respectively (11). Herring from the Bothnian Sea and Baltic Proper were found to contain similar sPCA concentrations (C10-C13, 60% Cl) of 1.4 and 1.5 µg/g, respectively (11). Tomy et al. (12) found respective sPCA concentrations (C10-C13, 60-70% Cl) of 1.1, 0.3, and 1.2 µg/g in yellow perch (Perca flavescens), catfish (Ictalurus punctatus), and zebra mussels (Dreissena polymorpha) from the Detroit River, MI. In the present study, we report on the first analysis of marine mammals from various regions of the Canadian Arctic and beluga whales (Delphinapterus leucas) from the St. Lawrence River estuary for sPCAs by high-resolution gas chromatography electron capture negative ion high-resolution mass spectrometry (HRGC-ECNI/HRMS). The formula group abundance profiles of mammals were also examined as they provided insight into the source, and mode of environmental transport, of these compounds. sPCA levels relative to those of other POPs are also reported.
Methods and Materials Chemicals. The commercial formulation, C10-C13, 60% chlorine by mass (sPCA-60) was supplied by Dover Chemicals Corp. (Dover, OH) and was used as the analytical standard VOL. 34, NO. 9, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 1. Sampling sites for marine mammals examined in this study.
FIGURE 2. ECNI selected ion chromatograms of the hexachloroundecanes in a few of the marine mammals under investigation and the sPCA-60 standard. for this study. Isotopically labeled 13C8 mirex (99% 13C) was purchased from Cambridge Isotope Laboratories Inc. (CIL) (Burlington, ON, Canada). Sample Locations and Storage. Mammals examined in this study, collected over the period 1978-1995, were extracted and analyzed in previous studies for PCBs, DDT, and toxaphene (CHBs) (13-15). Extracts were stored in Teflon capped glass vials inscribed with a volume marker. The samples collected during the 1970s and 1980s were archived at 7 °C, while the more recent extracts (1990s) were stored at ambient temperature. Figure 1 shows the sampling regions where the marine mammals had been collected. Blubber from three beluga whales (Mackenzie Delta, Northwest Terrorities) and six ringed seal (southwest Ellesmere Island, Eureka) were obtained from animals taken by Inuit hunters at these locations in the Canadian Arctic in 1995 and 1994, respectively. From northwest Greenland, blubber from four beluga whales (two from Saqqaq and two from Nuussuaq, see Figure 1) and two walruses (Odobenus rosmarus) (both from Thule), collected in 1989 and 1978, respectively, were also obtained from animals taken by Inuit hunters. Blubber samples from carcasses of five stranded beluga whales in the St. Lawrence estuary (two each from Baie-des Sables and Ste Flavie and 1616
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one from Ste Felicits) were collected in 1988. The age, sex, length, and maximum girth were available for almost all of the animals as previously reported. Extraction. Procedures for the extraction and clean up of blubber tissues were described in previous studies (13, 14). In brief, samples of blubber (2.2 g) were mixed with anhydrous sodium sulfate (pretreated by heating at 600 °C for 6 h), spiked with internal standards of aldrin and octachloronaphthalene (OCN) and extracted by ball-milling (30 min) with hexane. The extract was allowed to stand for 4 h and then centrifuged (1000 rpm). Extractable lipid was determined gravimetrically using one-eleventh of the extract. A portion of the extract equivalent to about 100 mg of lipid was then chromatographed on a column (300 mm × 10.5 mm i.d.) of reagent grade Florisil (8 g, 1.2% deactivated with H2O, 60-100 mesh size) using the following solvent sequence: 38 mL of hexane (F1), 42 mL of 15:85 dichloromethane (DCM):hexane (F2), and 52 mL of 1:1 DCM:hexane (F3). Fraction F1 contained all the PCBs, chlorinated benzenes, DDT and its metabolites, most of the toxaphene (CHBs) components, and other chlorinated aromatics but no sPCAs. Fractions F2 and F3 contained sPCAs, while F3 contained more polar organochlorines such as heptachlor epoxide and dieldrin. For sPCA analysis, F2 and F3 were combined and diluted with
FIGURE 3. Formula group abuandance profiles for (A) St. Lawrence River beluga, (B) Mackenzie Delta beluga, (C) Ellesmere Island ringed seal, (D) Greenland walrus, and (E) Greenland beluga. hexane, and the solvent volume was reduced to 0.5 mL with a gentle stream of nitrogen prior to GC/MS analysis. A known amount of 13C8-mirex, used as an internal standard for selected ion monitoring (SIM), was added to the residual solution at this stage. GC-Analysis. The analysis of PCBs, DDT, and CHB, done previously (13, 16-18), was carried out on a DB-5 fused silica column (60 m × 0.25 mm i.d, 0.25 µm film thickness), with (63Ni) electron capture detection. In brief, for PCBs a total of 74 PCB congeners was quantified using a series of congener mixtures. A few congeners, for which standards were not available, were quantified with response factors estimated from other congeners of the same chlorine number and similar GC retention times. Total PCB (∑PCB) was the sum of all congeners. Total DDT (∑DDT) was the sum of p,p′DDE, DDD, DDT, and o,p′-DDT. Total CHB (∑CHB) was determined by relating the response of 20 peaks in the sample to those in a toxaphene standard. Analyses of sPCAs were performed on a HP 5890 Series II GC, fitted with a high-
resolution DB-5ms fused silica column (30 m × 0.25 mm i.d., 0.25 µm film thickness), connected to a Kratos Concept highresolution mass spectrometer by a heated transfer line maintained at 280 °C. ECNI/HRMS operating procedures can be found elsewhere (12). All sample injections were made by a CTC A200SE autosampler. The injector port temperature was 220 °C, and an electronic pressure program maintained a helium carrier gas flow rate of 0.75 mL/min. The column temperature program was as follows: initial 150 °C; hold for 1 min; ramp to 260 °C at 7 °C min-1; hold for 8:18 min; ramp to 280 °C at 10 °C min-1; hold for 13 min. Quality Assurance and Control (QA/QC). Precautions used in the analysis included use of glass-distilled solvents, high-temperature heating of glassware, sodium sulfate, and Florisil. Marine mammals from each sampling site were extracted separately to avoid cross contamination during the workup procedure. For each species, a hexane procedural blank was extracted and analyzed in the same manner as the samples to check for impurities in the reagents and possible VOL. 34, NO. 9, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Concentrations (ng/g) of sPCAs and Other POPs in Blubber of Marine Mammals from the Arctic and the St. Lawrence River Estuarya species
location
year
sex
ageb
% lipid
∑DDT
∑PCB
∑CHB
∑PCA
ringed seal
SW Ellesmere Is., Eureka
beluga
NW Greenland
beluga
Mackenzie Delta, NWT St. Lawrence River
walrus
NW Greenland
F F F F F M M F F F M M M F M F M M M M
18 16 nd nd 33 nd 12 6 7.5 1.5 nd nd nd 23+ 20+ 31+ 27+ 20+ 19 17
93 92 91 88 88 90 85 93 90 85 95 94 93 78 75 94 86 83 84 83
810 510 400 490 700 1040 2440 2530 2570 1350 4490 3100 3090 11760 95390 54790 88070 148900 26 39
1410 1100 760 880 1260 1600 4120 3710 4310 2430 5750 4850 3830 22400 74700 65920 72800 121500 115 200
610 440 380 450 570 440 2590 2850 3420 3330 2580 4550 1920
beluga
1994 1994 1994 1994 1994 1994 1989 1989 1989 1989 1995 1995 1995 1988 1988 1988 1988 1988 1978 1978
380 400 540 770 700 370 250 215 220 110 300 180 140 770 370 650 1360 760 360 490
a References for concentrations of ∑DDT, ∑PCB, and ∑CHB can be found in the text. to read and the animal may be older. Some animals are yet to be aged.
contamination during the workup. Background signals from the procedural blanks were negligible, and no corrections were made to the samples. Previously reported recoveries of the internal standards (aldrin and OCN) were generally >90% (13-15). Formula Group Abundance Profiles. The generation of SIM ion chromatograms has been described previously (12). In brief, the MS operating in the SIM mode was tuned to monitor the two biggest peaks in the [M - Cl]- group of isotopic peaks, one for quantitation and the other for confirmation, for the following formula groups: C10 (Cl5 to Cl10), C11 (Cl5 to Cl10), C12 (Cl6 to Cl10), and C13 (Cl7 to Cl9). Profiles were generated by correcting the electronically integrated ion signals for each formula group for isotopic and response factors and then plotting them in a bar graph format. Method of Quantitation and Analysis. Quantitation was achieved by selecting the biggest peak corresponding to [M - Cl]- ion of the most abundant formula group present in the sample and correcting for variations in the formula group abundances between the standard and sample (12). Profiles were determined, for a few marine mammal species, and it was assumed that the profiles of the other mammals sampled from the same region and belonging to the same species were similar. The appearance of the formula group abundance profile of the sPCA-60 external standard used in this study can be found elsewhere (5, 12).
Results and Discussion Figure 2 shows the ECNI selected ion chromatograms of the C11H18Cl6 formula group, based on the response of the [M Cl]- ion, present in a few of the Arctic marine mammals under investigation and in the sPCA-60 standard. The broad elution envelope is typical of these mixtures and results from the large number of positional and stereoisomers that are present (5). 1. Variation in Formula Group Abundance Profile with Sampling Site. Figure 3 (a-e) shows the formula group abundance profiles for the marine mammals that were examined in this study. Except for the beluga from the St. Lawrence River estuary, the profiles for the Arctic marine mammals show a predominance of the shorter carbon chain 1618
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b
330 220
Ages with + sign indicate dentine layers were difficult
length congeners, i.e., the C10 and C11 formula groups, (C10H16Cl6 in all cases being the most abundant congener); in some cases, congeners from the C13 homologue group are not observed. For the ringed seals from Ellesmere Island, walruses and belugas from Greenland, the C10 and C11 formula groups account for 82, 85, and 88% of the total ion abundance, respectively; for belugas from the St. Lawrence River estuary the C10 and C11 abundance is only 55%. For belugas from the Mackenzie Delta, this abundance is 91%. Conversely, the abundances of the C12 and C13 formula groups is highest for the belugas from the St. Lawrence River estuary (45%), while for the other species, the range is 9-18%. The enrichment of the lower carbon chain length congeners of mammals from the Arctic is significant because Drouillard et al. (19) have shown that these congeners are, not surprisingly, the more volatile components of PCA mixtures. Based on their measurements, the authors noted a trend of decreasing VPs with increasing carbon chain length and degree of chlorination. These results suggest that contamination of these compounds to this region is by longrange atmospheric transport. The formula group abundance profile for the belugas from the St. Lawrence River estuary, which are influenced by urbanized and industrialized activities, showed a shift toward the less volatile components, i.e., higher carbon chain length, inherent to commercial formulations. Even though the appearance of the profile for the St. Lawrence beluga is slightly different to that of the sPCA-60 mixture used in this study, it should be noted that there could be numerous other formulations that might be in use in this region. Higher proportions of the less volatile components in the profile suggests that local sources of sPCAs, possibly from the Great Lakes and/or the industrialized regions of the lower St. Lawrence River, may be more important inputs of sPCAs into the St. Lawrence estuary and outweighs inputs through the atmosphere. 2. Concentration of sPCAs Relative to Other POPs. Table 1 shows the concentration of sPCAs, relative to ∑PCB, ∑DDT, and ∑CHB. Concentrations of sPCAs in the St. Lawrence beluga were higher than in any of the Arctic mammals. Mean wet weight sPCAs levels in St. Lawrence belugas were four times higher than in Greenland and Mackenzie Delta belugas, but only 1.5 times higher than in ringed seals from Ellesmere
Island. Walruses from northwest Greenland also had lower levels, ca. two times, of sPCAs than for St. Lawrence belugas. The elevated levels of sPCAs in belugas from the St. Lawrence River are consistent with the findings of elevated levels of other organochlorines by Muir et al. (13). These authors suggested that elevated organochlorine levels in belugas from this region are a consequence of high levels of organochlorines present in the wide variety of species, viz., smelt and tomcod, that are lower down in the food chain; local source contamination, undoubtedly, can be attributed to this effect. Belugas. Muir et al. (13) reported ∑PCB concentrations ranging from 22.4 to 121.5 µg/g (wet wt) and for ∑DDT from 11.8 to 148.9 µg/g for belugas from the St. Lawrence River. Corresponding sPCAs concentrations were lower by almost an order of magnitude, with the highest concentration being for the oldest male (1.4 µg/g). sPCA concentrations in beluga from Greenland and the Mackenzie Delta were significantly lower than those of ∑PCBs, ∑DDTs, and ∑CHBs. Stern et al. (14) reported respective mean wet weight concentrations of ∑DDTs, ∑PCBs, and ∑CHBs to be 2.2 ( 0.6, 3.6 ( 0.8, and 3.0 ( 0.4 µg/g in Greenland beluga, while sPCAs concentrations in this study were 0.19 ( 0.06 µg/g (n ) 4). Similar differences were observed for Mackenzie Delta beluga. Mean wet weight concentrations of ∑DDTs, ∑PCBs, and ∑CHBs in these mammals were 3.6 ( 0.8, 4.8 ( 0.9, and 3.0 ( 1.3 µg/g (15), respectively, while sPCAs concentrations were 0.20 ( 0.08 µg/g. Ringed Seals. Concentration ranges for ∑PCBs, ∑DDTs, and ∑CHBs are 0.760 to 1.6 µg/g (wet wt), 0.400 to 1.0 µg/g, and 0.38 to 0.61 µg/g, respectively, for ringed seals from southwest Ellesmere Island, Eureka (15). sPCA concentrations ranged from 0.38 to 0.77 µg/g. Mean wet weight concentrations for sPCAs (0.52 ( 0.17 µg/g) (n ) 6), however, exceeded those of ∑CHBs (0.48 ( 0.89 µg/g) and were only slightly lower than that of ∑DDT (0.66 ( 0.24 µg/g). Mean wet weight concentrations of ∑PCBs (1.2 ( 0.3 µg/g), however, were higher than sPCAs by 2-fold. Walruses. Mean wet weight concentrations of sPCAs in walruses from northwest Greenland were 0.43 ( 0.06 µg/g (n ) 2). Mean wet weight concentrations of ∑PCBs (0.16 ( 0.04 µg/g) and ∑DDTs (0.032 ( 0.006 µg/g) (20) were significantly lower than those of sPCAs; however, ∑CHB concentrations (0.27 ( 0.05 µg/g) (20) were only 1.5 times lower. The higher levels of sPCAs in walruses from Greenland compared to belugas (ca. two times) may be a result of the varying metabolic capabilities between the two species. Although only a few samples have been analyzed in this study, it is clear that sPCAs are present in Arctic food webs and are being transported to these remote regions either in the atmosphere or ocean currents. sPCA concentrations in Arctic biota were found to be generally lower than those of other persistent organochlorines implying that sPCAs might be less bioaccumulative than other POPs. The shift toward the less volatile sPCA congeners in belugas from the industrialized regions of the St. Lawrence River suggests that inputs to this region are predominantly from local sources. Future studies would involve the analysis of larger data sets for mammals from a wider geographic area to further assess the spatial and temporal distribution of these compounds. Additional information on sPCA levels in water and lower food web organisms is also needed to determine the extent of their biomagnification.
Canadian Chlorine Coordinating Committee for their financial support to D.C.G.M. and J.B.W. We thank Dover Chemicals (Dover, OH) for providing us with their commercial mixture. We also thank Pierre Be´land (St. Lawrence National Institute of Ecotoxicology, Que`bec) for providing the St. Lawrence River beluga samples, Rune Dietz (National Environmental Research Institute (NERI), Copenhagen) for the Greenland beluga samples, Erik Born (NERI) for the walrus samples from NW Greenland, and Don Metner (Department of Fisheries and Oceans, Winnipeg) for the Mackenzie Delta beluga samples.
Acknowledgments
Received for review August 18, 1999. Revised manuscript received January 26, 2000. Accepted January 28, 2000.
The authors would like to thank the Natural Sciences and Engineering Research Council of Canada (NSERC) and the
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