Environ. Sci. Technol. 2004, 38, 4950-4955
Enantiomeric Specificity of Methylsulfonyl-PCBs and Distribution of Bis(4-chlorophenyl) Sulfone, PCB, and DDE Methyl Sulfones in Grey Seal Tissues CHRISTINA LARSSON,† KARIN NORSTRO ¨ M,† IOANNIS ATHANANSIADIS,† ANDERS BIGNERT,‡ WILFRIED A. KO ¨ NIG,§ AND Å K E B E R G M A N * ,† Department of Environmental Chemistry, Stockholm University, SE-106 91 Stockholm, Sweden, Contaminant Research Group, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden, and Institute for Organic Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg, Germany
PCB methyl sulfones (MeSO2-PCBs) are lipophilic PCB metabolites of which five of the environmentally relevant meta/ para pairs are chiral (i.e., exist as atropisomeric pairs). Methylsulfonyl-DDE (MeSO2-DDE) is a DDE metabolite, while bis(4-chlorophenyl) sulfone (BCPS) is a commercial monomer used for thermoplastic production. All these sulfones are well-known environmental contaminants. In this study, liver, lung, and adipose tissue in grey seals (Halichoerus grypus) from the Baltic Sea, naturally exposed to organochlorines via their food, were analyzed for the compounds mentioned. MeSO2-PCBs, 3-MeSO2-DDE, and BCPS were all found in significantly higher concentrations in the liver than in lung and blubber. Their strong liver retention, represented by a median of 42 µg/g l.w. of ΣMeSO2PCBs, has previously been mainly neglected in assessments of exposure. The highest concentrations of PCBs and DDE were still found in the grey seal blubber. The atropisomeric composition of MeSO2-PCB congeners was determined, and their enantiomeric fractions were calculated and compared in blubber, liver, and lung tissues. The enantiomeric specificity was equal in all tissues. A notably high abundance (>94%) was observed for one atropisomer in each chiral MeSO2-PCB pair. The first eluting atropisomer (A1) was dominating for all para-substituted MeSO2PCBs studied, while the second eluting atropisomers (A2) were as dominant in all meta-substituted MeSO2-PCBs in all samples analyzed. In the liver, as much as 50% of ΣMeSO2-PCBs consisted of the second eluting atropisomer (A2) of 5-MeSO2-CB149. The results imply that the sulfone group is crucial for the specific liver retention of MeSO2-PCBs, 3-MeSO2-DDE, and BCPS.
* Corresponding author phone: +46-8-163997; fax: +46-8-163979; e-mail:
[email protected]. † Stockholm University. ‡ Swedish Museum of Natural History. § University of Hamburg. 4950
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ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 38, NO. 19, 2004
Introduction Aryl methyl sulfones, such as methylsulfonyl-PCBs (MeSO2PCB) and -DDE (3-MeSO2-DDE), were first reported as metabolites of polychlorinated biphenyls (PCBs) and 2,2bis(4-chlorophenyl)-1,1-dichloroethane (DDE) in the mid 1970s and have thereafter been of environmental interest (1). MeSO2-PCBs are formed via the mercapturic acid pathway (MAP) (2) followed by C-S bond cleavage. The aryl thiol formed is subsequently methylated, and the sulfide is oxidized (1). Both meta- and para-MeSO2-PCB metabolites are found in biota, formed from about 15 different PCB congeners. These sulfones are neutral, bioaccumulating metabolites retained in lipid-rich tissues in humans and in wildlife in a tissue specific manner. The para-MeSO2-PCB congeners dominate over the meta-substituted congener in lung tissue (3, 4), whereas meta-MeSO2-PCBs seem to be more abundant in mammalian liver tissues, as reported in humans and several mammalian species (5-8). The high tissue selectivity of some MeSO2-PCB congeners are due to protein binding (4, 9). MeSO2-PCBs are among the most abundant anthropogenic organohalogen substances (OHS) in mammals but in general with lower concentrations than of PCBs and DDE (1). Some MeSO2-PCBs, as well as the parent PCB congeners, are chiral due to the energy barrier to free rotation of the carbon-carbon bond between the two phenyl rings. This leads to the formation of several atropisomeric MeSO2-PCBs. Five pairs of MeSO2-PCB atropisomers have hitherto been discussed as environmentally relevant (6, 10) and calculated to include 17% of the total MeSO2-PCBs found in the high Canadian arctic (10). A strong dominance for one atropisomer of each chiral MeSO2-PCB has been shown in arctic ringed seal blubber, in polar bear fat (10), in human livers (6), in harbor porpoise livers (11), and in rats given technical PCB (12). The present study on atropisomers of MeSO2-PCBs is, in perspective, motivated from a toxicological viewpoint since MeSO2-PCBs have a range of effects both in vitro and in vivo as summarized by Letcher et al. (1). MeSO2-PCBs have been indicated to have endocrine related effects (13-15), and some of the congeners are strong inducers of cytochrome P-450 dependent enzymes (16). Also, there is an indication that MeSO2-PCBs may be involved in the manifestation of the respiratory distress observed in Yoshu victims (17). The toxicological relevance of the enantioselective dominance of MeSO2-PCBs is as yet unknown, but effects on disposition and toxicity cannot be excluded (18). Hence, it is of interest to study atropisomeric MeSO2-PCBs in the strongly effected grey seals from the Baltic. Diaryl sulfones, such as bis(4-chlorophenyl) sulfone (BCPS), are a commercially produced chemical, mainly to be applied as a starting material for the production of thermostable polymers, such as polysulfones and polyether sulfones (19, 20). BCPS is also applied in dental plastics (21) and has been used as a pesticide together with DDT (22). The U.S. EPA has classified BCPS as a high production volume chemical with an annual production in the U.S. of 10 000 metric tons (23). BCPS was first reported as an environmental contaminant in 1995, in perch from Latvian coastal areas (24), and has since been reported in several species in Sweden from different steps in the food chain with particularly high levels (low ppm range) in guillemot eggs (24,25). The log Kow of BCPS is 4.1, high enough to be a potentially bioaccumulating compound. The present study has two major objectives: first, to determine the enantioselective retention and distribution of 10.1021/es049361v CCC: $27.50
2004 American Chemical Society Published on Web 09/02/2004
TABLE 1. Median Concentrations (ng/g l.w.) and Range of 14 MeSO2-PCB Congeners, ∑MeSO2-PCB, MeSO2-DDE, BCPS, CB-153, and DDE in 10 Grey Seals Blubber, Liver, and Lung blubber
liver
lung
congener
median (ng/g l.w.)
range
median (ng/g l.w.)
range
median (ng/g l.w.)
range
5-MeSO2-CB64a 4-MeSO2-CB64b 3′-MeSO2-CB87a 4′-MeSO2-CB87b 5-MeSO2-CB91a 4-MeSO2-CB91b
8.6 38 130 150 15 17 400 210 44 68 210 300 39 22 1700 41 60 18000 11000
4.2-28 18-150 54-390 62-450 10-46 9.8-47 120-1500 95-830 24-160 34-190 64-530 110-840 17-120 12-69 640-5200 19-180 41-240 4900-43000 5400-36000
15 7700 7100 190 400
