Environ. Scl. Technol. 1904, 18, 625-628
NOTES Evidence for the Long-Distance Atmospheric Transport of Polychlorinated Terphenyl Ronald J. Wlngender" and Richard M. Wllllams Environmental Effects Research Program, Environmental Research Dlvlsion, Argonne National Laboratory, Argonne, Illinois 60439
w The ubiquitous occurrence of polychlorinated biphenyls
Table I. Vapor Pressure of Selected Pollutants
in the environment is well-known. A class of chemically similar compounds, the polychlorinated terphenyls (PCTs), has also been found, but their routes into the environment and the extent of contamination me not known. Recent sampling from a site located in the middle of Lake Huron indicates that the atmosphere over the lake contains low levels (preliminary work shows levels up to 2 ng/m3) of PCTs; PCTs were also found in precipitation samples. The detection of PCTs well after their production ceased (-1970) suggests that this class of compounds may already be as ubiquitous as PCBs with respect to long-range atmospheric transport.
Introduction The ubiquitous occurrence of polychlorinated biphenyls (PCBs) is a well-documented consequence of the poorly regulated manufacture, use, and disposal of these environmentally persistent compounds (1-6). A class of chemically similar compounds, the polychlorinated terphenyls (PCTs), has not received such notoriety or study, although their manufacture also began in the 1930s (7). This may be because the total amount of PCTs produced was only a few percent of the estimated 1.25 X lo9 lb of PCBs produced (7) and the use of PCTs as plmticizers and resins in adhesive products (7) and as casting waxes in investment casting facilities (8)was not publicized to any great extent. The resulting lack of attention to them makes it difficult to realize that their distribution in the environment may be as widespread as that of PCBs. PCTs have been detected in birds [in Britain (6), Canada (9),and Sweden (411; aquatic species (IO),and human tissues (1, 3, 5, 11). They have also been found in paperboard and food packaging material (12),and because of their use in silo sealants, they have been found in cow's milk (13). At a PCT production facility in Sauget, IL, and facilities (where PCTs were used as casting waxes) in Chicago and Detroit, these compounds were found in nearby surface soil samplings and in water effluent samples (8). PCTs have also been detected in samples of soot and dust taken from various combustion sources and metropolitan soil samples (141, in precipitated dust and burned refuses (at the ppm level) from waste incineration plants (15),and in lake water samples from the Lake Huron area (16). The PCTs were postulated to arise from the combustion process (14) and from vaporization during incineration of materials containing manufactured PCTs (15). While this information tends to suggest that PCTs are ubiquitous, no data or hypotheses have been presented regarding the routes by which they have become so widely distributed in the environment. However, since the importance of atmospheric transport in distributing PCBs both on a local and global basis has been demonstrated 0013-936X/84/09 18-0625$01.50/0
compd/ mixture anthracene Aroclor 1242 pyrene Aroclor 1254 Aroclor 1260 chrysene benzo[a]pyrene Aroclor 5460
vapor pressure, mmHg, at 38 OC range"-* meann
Nisbet & Sarofim
2 x 10-3 3 x 10-4
1 x 10-3
2 x 10-3 to 4 x 10-5
8
4 x 10-3to 2 x 10" 4 x 10-5to 2 x 10-8
2 x 10-7to 8 x 10-1'
x 10-5
3X
6X
3 x 10"
2 x 10-7
3 x 10-6 2 x 10-7 4 x 10-8
Computed by extrapolating vapor pressure (22) for n-hydrocarbons vs. retention time on a nonpolar column. *The range is given by the vapor pressures of the first and last component to elute from the Aroclor mixture.
(17,18),it should certainly be considered as a main route for the global distribution of PCTs. The reason that PCBs are easily transported in the atmosphere has been attributed to the relatively high vapor pressures of the PCB congeners. However, PCTs have vapor pressures lower than those of PCBs (see Table I). Thus, they should be much leqs likely to be present in the atmosphere in the vapor state. Nevertheless, the analysis of surface soil samples taken around one manufacturing facility led Stratton and Sosebee (8) to conclude that the spatial distribution of PCTs was indicative of airborne transport. They found that the GC elution pattern showed little evidence of either selective emission or selective transport of the more volatile congeners, which indicated that the source of the airborne contamination was a t a temperature such that the entire PCT mixture must have been in the vapor state a t the point of emission. We have found preliminary evidence that PCTs do exist in the atmosphere, possibly in the vapor state, as well as in association with particulate matter, at a great distance from potential sources. Also, we present data showing the presence of PCBs and PCTs in precipitation and provide some quantitative information. Description of Collection Site and Instrumentation. The air filter and precipitation samples were collected from a 30-m tower anchored in 20 m of water near the middle of Lake Huron on the Six Fathom Bank (40°49'N, 8 2 O 29'W). Since the location is 60 km from the nearest land, it is representative of a large portion of the lake. In addition to sample collection, the tower was instrumented for the collection of meteorological information and its storage on magnetic cassette tapes. The air sampled was drawn from about 9 m above water level, while the pre-
0 1984 American Chemical Society
Environ. Sci. Technol., Vol. 18, No. 8, 1984
625
cipitation collector was located on a platform at the 6 m level. Power for the air sampler, precipitation collector, and data acquisition system was supplied by batteries whose charge was maintained by solar electric panels. The data cassettes, exposed air filters and XAD-2 cartridges, and precipitation samples were retrieved approximately monthly. Sampling was conducted from June 11 to Oct 7, 1980. Air Samples. A sequential air sampler designed and built at Argonne National Lahoratory was used to collect the air samples. The sampler contained 24 stainless steel tubes sandwiched between two platens (a description of the sampler, redesigned to use glass tubes containing Florisil, is given in ref 19). Each tube contained 12-14 g of XAD-2 resin which had been cleaned by first extracting with acetonitrile, acetone, methylene chloride, and, finally, petroleum ether. Air was drawn through a 3-pm Zeffuor Teflon Filter (no. P5Pl 01350, Ghia Corp.) to trap particulates prior to entering the resin. Each filter and resin tube was exposed for B 48-h period. A flow rate of about 3 L/min was maintained. The exposed filters and XAD-2 resin were extracted in a Soxhlet apparatus for 18 h in methylene chloride. The extract from the resin was concentrated and subjected to a micro-Florisil cleanup prior to injection on the gas chromatograph. Precipitation Samples. Four samples were taken by using a wet only sampler of the Health and Safety Laboratory design, manufactured hy Aerochem Metrics, Tnc A cover over the precipitation container was automatically retracted during the rain events. The precipitation was drained into precleaned gallon bottles containing 3 00 mL of methylene chloride, After the water was removed from the container, acetone was used to wash all surfaces followed by rinsing with methylene chloride. The washes were drained into a separate precleaned gallon bottle. The precipitation samples were extracted in the gallon bottles with the initial 100 mL of methylene chloride. After settling, the methylene chloride was drawn off, and the samples were extracted an additional 2 times with 100-mL portions of methylene chloride. The acetone methylene chloride washes were concentrated on a rotary evaporator, combined with the methylene chloride extract8, and reduced to - 5 mL volume. This 5-rn1, concentrate was subjected to the standard FDA PAM Florisil cleanup prior to GC analysis. Preliminary work has shown that, under the conditions used, a recovery of 81% Aroclor 1254 and 98% Aroclor 5460 could be expected. Experimental Section Materials. Rurdick & Jackson distilled-in-glms solvents
were used in this work. Aroclor 1242,1254,1260, and 5460 standards were obtained from Monsanto Corp. Amberlite XAD-2 resin was purchased from Scientific Products (No. EKC 11373). Florisil (60/100 mesh, Supelco No. 2-0280) activated at 130 "C for 24 h was used for cleanup Cleanup Procedure. Prior to use, all glassware was rinsed first with acetone and then with petroleum ether. A micro cleanup column was prepared by placing a small wad of glass wool (precleaned by extracting in a Soxhlet apparatus with 1:l hexane/acetone) in a disposable Pasteur pipet, followed by 0.1 g of Florisil and 1 g of granular anhydrous sodium sulfate. The sodium sulfate had been extracted wit,h 1:1 hexane/acetone in a Soxhlet apparatus, air-dried, heated overnight at 130 "C, and stored in a desiccator prior to use. Approximately 0.5 mL of the extract was quantitatively transferred to the microcolumn, which was then eluted with 6 mT, of petroleum ether. The eluate was collected in a 15-mL conical centrifuge tube and concentrated under 626
Environ. Sci. Technol., Vol. 18. No, 8, 1984
Figure 1. Electron capture gas chromatogram of Aroclor 5480 (4 ng) obtained by using 12-m fused silica capillary column coated with methylsilicone, programmed from 130 to 252 "C at 3 'Clmin with a 16-min hold at 252 OC
a gentle stream of nitrogen (purified by passage through a Matheson Model 450 gas purifier) to the appropriate volume The regular Florisil cleanup used is described in the FDA Pesticide Analytical Manual Volume 1, section 211 14 (d). The eluate was collected in a 250-mL round-bottom flask and concentrated by using a rotary evaporator. The concentrated eluate was quantitatively transferred to a 15-mL conical centrifuge tube and concentrated further under a stream of nitrogen to the appropriate volume. Gas Chromatographic System. The samples were injected into a Varian 3700 gas chromatograph equipped with a 63Nielectron capture detector. The 0.2 mm i.d. X 12-m fused silica capillary column coated with methyl silicone was obtained from Hewlett-Packard. The temperature program used was 130-250 "C at a 3 "C/min rate with a 20-min hold at 250 "C. Injector and detector temperatures were 250 and 300 O C , respectively. Quantitation was accomplished by using a Hewlett-Packard 3390A reporting integrator set to measure peak areas. GC/MS System, GC/MS confirmation was made by using a Hewlett-Packard (H-P) 5993A GC/MS equipped with an H-P lo00 E series computer. The parameters used for scanning were aq follows: run time 85 min; mass range 70-700 amu; A/D measurements per datum point 1; scan rate 362 amu/s; threshold 10. Single ion runs were made at the most abundant masses of 506,540, and 574 as determined experimentally by using Aroclor 5460 at a concentration of 60 pg/pJ-,. These masses corresponding to the Cls (parent ion = 502 amu), Cl, (parent ion = 536 m u ) , and Cll0 (parent ion = 570 amu) congeners, respectively, are consistent with those found experimentally by Putnam et al. (20) as the most intense m / e observed. The chromatographic system utilized a 50 m X 0.2 mm i d . fused silica capillary column coated with SE-54. A temperature program of 70-320 "C at a rate of 4 "C/min with a 60-min hold at 320 "C was used.
Results and Discussion Preliminary gas chromatography of the cleaned-up XAD-2 extract showed traces of componenh eluting after the Aroclor 1260 region. A t first these were thought to be contaminants from the resin itself, and the column conditions were changed to ensure complete removal of all chromatographable species, However, in so doing, a pattern emerged which compared very closely with the pattern obtained with Aroclor 5460 (Figures 1 and 2, upper trace). GC/MS confirmation was obtained which indicated that Aroclor 5460 was being collected from the air above Lake Huron. Concentrations of Aroclor 5460 found in several samples ranged from below the level of detection to 2 ng/m3. A considerable number of electron-capturing components were observed in the early part of the gas chromatogram As a result, it was impossible to identify a specific PCR pattern, although some characteristics of the Aroclor 1254 pattern were distinguishable. A distinct yellow band was always observed on the Florisil after cleanup of the
Figure 2. Electron capture gas chromatograms: (upper trace) extract of XAD-2 resin exposed July 23-24. 1980; (lower trace) extract of filters exposed Aug 13-Sept 17, 1980.
Table 11. Concentration of PCBs and PCTs in Precipitation Samples dates collected
amount collected, mL
concn, ppt,C as Aroclor 1254
concn, ppt,‘ as Aroclor 5460
6/11-7/21/80 7121-43/13/80 8113-9/17/80 9/17 -10/7/80
3160“ 2270 7000 1940
12
3.4 NDb ND 960
3.8 1300 95
“Collected in a 12 X 12 X 12 in, galvanized steel container; the other three samples were collected in a Pyrex jar with the same dimensions. bND = none detected. “ppt = parts per trillion. _I__II
~
~
exposed XAD-2 resin extract. Whether the materials contributing to this yellow band came from the sampled air or from breakdown of the resin itself is not known. It has been observed, however, that artifacts from the XAD-2 resin chromatograph in the region where Aroclors 1221 and 1242 elute, prohibiting their quantitation based on a specific Aroclor pattern. The latter part of the chromatogram, which contained the PCT pattern, was essentially similar to that of the Aroclor 5460 standard and contained very few extraneous peaks. Analysis of the filter samples revealed that very little organic material as PCBs or PCTs was associated with the particulate matter. In every case, the filters from several collection periods had to be extracted together to provide an adequate concentration of analytes for detection. This practice provided sufficient concentration for qualitative assessment of the PCB portion of the GC elution pattern but did not provide sufficient sample to achieve an Aroclor 5460 pattern. However, a few of the more prorninent components were detectable (Figure 2, lower trace). This does not necessarily indicate that PCTs are not associated with the particulate matter since desorption of the PCTs from the filtered particulates to the resin could have occurred in the air stream. This problem has been discussed elsewhere (22). The pattern obtained for the PCB portion of the chromatogram (Figure 2, lower trace) could not be identified with any one Aroclor because peak ratios were entirely different from those obtained from the Aroclor standards. Two of the four precipitation samples had Aroclor patterns almost identical with those of 1254 and 5460. Figure 3 shows how well the patterns from sample 4 match the standards. In this sample, the concentration of PC‘l’s (as Aroclor 5460) exceeded that of PCBs (as Aroclor 1254) by approximately a factor of 10. The results of the analyses of four collection periods are given in Table 11. Analysis of laboratory glassware, XAD-2 resin blanks, water blanks, and solvent rinsing of a tower section revealed that the PCTYdid not originate from laboratory
Figure 3. Electron capture gas chromatograms of a mixture of Aroclor standards and an aliquot of a precipitation sample extract: (upper trace) Aroclors 1254 and 5460; (lower trace) extract of precipitation collected between Sept 17 and Oct 7, 1980.
contamination or tower materials. There was no obvious correlation between the concentration measurements and wind direction. All four sampling periods had similarly varying wind directions, with W and SW being dominant.
Conclusions The PCB and PCT concentration differences we have observed are most likely due to changes in source strengths, which are probably quite variable. Since it is unlikely that both the precipitation collector and air sampling systems were simultaneously contaminated, we have concluded that PCTs, like PCBs, can be transported in the atmosphere. We have attempted only to identify the existence and suggest the ubiquity of yet another environmental pollutant. We recognize the need to conduct further monitoring of both air and precpitation levels to define the extent of atmospheric contamination, Future work planned not only includes monitoring but also attempts to determine the direction of the sources of this pollutant with respect to the sampling site. Registry No. Aroclor 5460, 11126-42-4. Literature Cited (1) Watanabe, 1.; Yakushiji, T.; Kunita, N. Bull. Enuiron. Contam. Toxicol. 1980, 25, 810. (2) Minagawa, K. Nippon Eiseigaku Zasshi 1979, 33, 778. ( 3 ) Wright, L. H.; Lewis, R. G . ; Christ, H. L.; Sovocool, G. W.; Simpson, J. M. J. Anal. Toxicol. 1978, 2, 76. (4) Renberg, L.; Reutergardh, L. Chemosphere 1978, 6 , 477. (5) Fukano, S.; Doguchi, M. Bull. Enuiron. Contam. Toxicol. 1977, 17, 613. (6) Hassell, K. D.; Holmes, D. C. Bull. Enuiron. Contam. l’oxicol. 1977, 17, 618. (7) Craddock, J. Monsanto Industrial Chemicals Co., St. Louis, MO, private communication, 1981. (8) Stratton, C . L.; Sosebee, J. B., Jr. Environ. Sci. Technol. 1976, 10, 1229. (9) Zitko, V.; Hutzinger, 0.;Jamieson, W. D. Bull. Enuiron. Coritarn. “oxicol. 1972, 7, 200. (10) Freudenthal, J.; Greve, P. A. Bull. Environ. Contam. ’Ibxicol. 1973, 10, 108. (11) Doguchi, M.; Fukano, S.; Ushio, F. Bull. Enuiron. Contam. Toxicol. 1974, 11, 157. (12) Thomas, G. H.; Reynolds, L. M. Bull. Enuiron. Contam. Toxicol. 1973, 10, 37. (13) Fries, G. F.; Marrow, G. S.J . Assoc. Off. Anal. Chem. 1973, 56, 1002. (14) Bumb, R. R.; Crummett, W. B.; Cutie, S. S.; Gledhill, J. R.; Hummel, R. H.; Kagel, R. 0.;Lamparski, L. L.; Louma, E. V.; Miller, D. L.; Nestrick, T. J.; Shadoff, A.; Stehl, R. H.; Woods, J. S. Science (Washington,D.C.)1980,210,385. (15) Suzuki, R.; Saito, N.; Moritani, A.; Ito, M.; Oda, H. Aichi-ken Kogai Chosa Senta Shoho 1975, 3, 37. Environ. Sci. Technol., Vol. 18, No. 8, 1984 627
Environ. Scl. Technol. 1984, 18, 628-631
Mullin, M. D. (Large Lakes Research Station, U.S.EPA) “PCBs and Other Chlorinated Hydrocarbons in Lake Water, Fish, Human Blood and Human Milk A Qualitative Comparison Utilizing High Resolution Glass Capillary Gas Chromatography”. Presented at the LABCON ’81 Conference, Rosemont, IL, Sept 15-17, 1981. Nisbet, I. C. T.; Sarofim, A. F. EHP, Environ. Health
(20) Putnam, T. B.; Gulan, M. P.; Bills, D. D.; Libbey, L. M. Bull. Enuiron. Contam. Toxicol. 1974, 1 1 , 309. (21) Giam, C. S.; Atlas, E.; Chan, H. S.; Neff, G. S. Atmos. Environ. 1980, 14, 65. (22) “Lange’s Handbook of Chemistry”,11th ed.; McGraw-Hill: New York, 1973; pp 10-31 (Table 10-10).
Perspect. 1972, I , 21. Duce, R. A.; Duursma, E. K. Mar. Chem. 1977, 5, 319. Wingender, R. J.; Williams, R. M.; White, R. V.; Ely, R. S., submitted for publication in Atmos. Environ.
Received for review December 24, 1981. Revised manuscript received February 13,1984. Accepted February 23,1984. Work performed under the auspices of the U S . Environmental Protection Agency and the U.S. Department of Energy.
Comparison of the Carcinogenic Risks from Fish vs. Groundwater Contamination by Organic Compounds Michael Stewart Connor” Interdisciplinary Programs in Health, Harvard School of Public Health, Boston, Massachusetts 02 115
EPA’s carcinogenesis risk assessment methodology is used to compare the risks from trace organic contaminants in groundwater to those in freshwater and marine fishes. Lipophilic, biologically refractory organics are most often found in fish and soluble, volatile compounds in groundwater. Nationwide, known carcinogenic risks from fish consumption are a t least as important as those from groundwater consumption, but both vary widely with location and consumption patterns. Introduction Water pollution can affect the general public’s intake of organic carcinogens through two major pathways: drinking contaminated groundwater and consuming fish from contaminated surface waters. Since people ingest about 100 times more water than fish (2 L per capita daily vs. 18.7 g), it seems sensible to focus on groundwater, which supplies about half of our drinking water (I), in controlling our exposure to hazardous organic chemicals. On the other hand, fish and shellfish are able to bioconcentrate organic compounds to levels thousands of times greater than the concentrations in the water in which they live (2-4). While our consumption of fish is small, their contamination by organic compounds can be large enough to make a sizable contribution to our intake of carcinogens. What is the relative importance of these two pathways? While the EPA considers both pathways in developing its water quality standards ( 5 ) ,the average risks of drinking groundwater have never been compared to consuming contaminated fish. Recent nationwide groundwater and fishery surveys allow us to make a rough estimate of the carcinogenic risks associated with fish and groundwater consumption. The most extensive groundwater and fisheries data are from Nassau County on Long Island, NY, and the nearby waters of the New York Bight, which allows a comparison of these risks for a specific location. Methods The National Oceanic and Atmospheric Administration (NOAA), National Marine Fisheries Service (NMFS), United States Fish and Wildlife Service (USFWS), and Food and Drug Administration (FDA) have all recently released reports summarizing their chemical monitoring of aquatic organisms. The most extensive collection of ~~~
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*Address correspondence to this author at the Water Quality Branch, EPA Region I, Boston, MA 02203. 628
Environ. Sci. Technol., Vol. 18, No. 8, 1984
contaminant data is from surveys in the late 1970s for freshwater fish from USFWS’s nationwide survey (6, 7), and N O M S survey of marine fish from Puget Sound (8) and the New York Bight (9). More extensive geographic data for a few compounds have been collected for estuarine and coastal fisheries for 1981 (10, 11). In 1979, a marketplace survey of 768 fish products was conducted by the FDA (12). The concentrations reported in these field and marketplace surveys are in general agreement (13). A national survey of volatile organic compounds in groundwater has been conducted by the EPA (14). I have used data from their random survey of groundwater systems supplying more than 10000 people. The Nassau County groundwater data are based on several hundred samples from a 1980 groundwater quality assessment (15). These limited data for fish and groundwater concentrations fit both a normal and log-normal distribution. log-normal distributions are often used in risk assessment, but since the distribution of the groundwater data was so dependent on the chemical’s detection limit, I used means from the normal distribution to be conservative. Fish concentrations were treated similarly to be consistent. I have followed the methodology of the Environmental Protection Agency’s (EPA) Carcinogen Assessment Group (CAG), estimating human carcinogenic risk by multiplying a chemical’s carcinogenic potency factor, determined from animal feeding experiments and adjusted for humans, by the expected daily dose to humans from contaminated groundwater and fish (5). In determining the total risk of all the chemicals characterized in fish and drinking water for which a carcinogenic potency factor has been calculated, I have simply added the effects of the individual chemicals, ignoring any potential for synergistic effects. Carcinogenic potency factors published by the CAG were used in the calculations ( 5 ) . The CAG calculates dose for a 70-kg man with an average daily consumption of 2 L of drinking water and 6.5 g of estuarine and freshwater fish. Average U S . per capita daily consumption is 1.63 L of drinking water (16)and 18.7 g of all fish: 6.5 g of estuarine fish and shellfish, 2.0 g of freshwater fish, and 2.8 g of marine fish with the remainder tuna and unclassified imported fish (17). These assumed consumption rates used by EPA understate fish risks compared to groundwater risks since an upper bound of drinking water consumption is used. Fish risks would be 10 times greater if consumption rates at the 95% confidence interval, about 65 glday, were used. In using animal feeding tests to predict human risks from carcinogens, two conversions must be made: from
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