Environ. Sci. Technol. 2000, 34, 2684-2689
Assessment of Levels, Distribution, and Risks of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans in the Vicinity of a Vinyl Chloride Monomer Production Plant P I R J O I S O S A A R I , * ,† T U U L A K O H O N E N , ‡ HANNU KIVIRANTA,† J O U K O T U O M I S T O , †,§ A N D T E R T T U V A R T I A I N E N †,§ National Public Health Institute, Division of Environmental Health, P.O. Box 95, FIN-70701 Kuopio, Finland, Archipelago Research Institute, University of Turku, FIN-20014 Turku, Finland, and University of Kuopio, Finland
Levels of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs) were analyzed from environmental and human samples to assess contaminant distribution and risks associated with vinyl chloride monomer (VCM) production. Extremely high concentration of PCDD/Fs, 26 µg/g dry weight, was detected in the waste sludge. As a result of improper wastewater treatment practices in the 1970s, PCDD/Fs (11.4 kg, 32.0 g of I-TEQ) leached into the Gulf of Finland in the Baltic Sea. Despite high concentrations near the plant, the polluted area was restricted (about 26 km2), and VCM production could not be a significant contributor to the PCDD/F load of the sea. Frequent consumption of local fish was considered to be the most probable source of human exposure. However, serum samples taken from local residents and former workers did not indicate exposure to elevated levels of total PCDD/Fs. Octachlorinated furan was the main congener (73% of PCDD/F sum) in the waste sludge, and it also dominated in marine sediments. Contaminated sediments also had a characteristic PCB composition, containing exceptionally high proportions of IUPAC 206 and 209 congeners.
Introduction Processes in the chemical industry which are known to produce polychlorinated dibenzo-p-dioxins and dibenzofurans, PCDD/Fs, include the chloralkali process, synthesis of chlorophenols, and synthesis of vinyl chloride monomer (VCM). Wastes formed in these processes have been reported to contain high levels of PCDD/Fs (1-4). In many cases, these wastes have become sources of environmental pollution, since common practices in the past and unawareness of the presence of highly toxic compounds in production wastes have favored their storage at industrial sites, disposal at ordinary landfill sites, and even leaching into water systems. Final products of the chemical industry have been marketed * Corresponding author phone: +358 17 201 353; fax: +358 17 201 265; e-mail:
[email protected]. † National Public Health Institute. ‡ University of Turku. § University of Kuopio. 2684
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nationally or worldwide, and the use of, e.g., chlorinated fungicides at sawmills has been a considerable secondary source of PCDD/Fs in the environment (5, 6). The environmental burden of PCDD/Fs from the chemical industry has been difficult to estimate, since the amounts of PCDD/Fs formed are largely unknown, and the routes for their distribution are complicated (7). The multitude of processes in the chemical industry with a possibility for PCDD/F byproduct formation still needs wider recognition so that all the pollution cases can be identified. To provide a proper basis for future risk assessments at industrial sites, casespecific conditions in waste treatment and disposal and environmental distribution and transport routes for pollutants need to be addressed in the context of human exposure. This paper reports an extensive survey in which PCDD/F levels in VCM production waste and in various environmental samples collected from the surroundings of the chemical plant were measured. Studies on contaminant spreading in the Gulf of Finland were strongly motivated since the gulf was known to be polluted by PCDD/Fs (8), and the chemical plant was suspected for being one of the PCDD/F sources. The aims of this study also included local risk assessment, which was based on the actual exposure data and evaluation of the existing routes for exposure.
Materials and Methods Site Description. Vinyl chloride monomer (VCM) was produced at an industrial site in Sko¨ldvik, on the southern coast of Finland, during 1973-1981. The production plant utilized oxychlorination process. Wastewater formed in the process was let to settle in two ponds at the site. The purified water was then led into the Gulf of Finland in the Baltic Sea, via a cooling water tunnel. The remaining sludge was transported to two landfill sites located in the same industrial area as the factory. After the discontinuation of VCM manufacturing in 1981, the rest of the sludge was stored in one of the former wastewater ponds. The amount of the sludge was 12 500 tons, containing 45% of solids. According to the analyses of the chemical company, the main chemical constituents of the sludge were PVC (poly(vinyl chloride)) by 1900 tons, VCM 11 tons, 1,2-dichloroethane 10 tons, and copper 11 tons. Other chlorinated compounds such as polychlorinated biphenyl ethers were present at lower levels. The sludge also contained mineral oil, and soil material mainly consisting of clay had been added to bind the waste. Sample Collection. Samples for PCDD/F analyses were collected from the waste sludge, groundwater, brook sediments, soils, mosses, marine sediments, and fish. Serum samples were collected to investigate human exposure. Surface sediment samples, which were taken with a nonfreezing Limnos-type sampler from the sampling points shown in Figure 1, were used to study horizontal distribution of pollution in the sea. Sediment cores were taken with a freezing sampler, sliced into 2.5-cm disks, and used to study vertical distribution of pollution. The dating method used was based on 137Cs radionuclides and the number of spheroidal carbonaceous particles (SCPs) in sediment material. Additional sediment samples were taken to estimate the total PCDD/F burden in the sediments, to delineate the area where accumulation of depositing material occurred, and to analyze the concentrations of polychlorinated biphenyls (PCB). Brook sediments were sampled from 7 locations near the site and the two landfills. Water samples were taken from four wells and from an aquifer below one of the landfills. Sample volumes were 2 L. 10.1021/es991311g CCC: $19.00
2000 American Chemical Society Published on Web 05/24/2000
FIGURE 1. Concentrations of octaCDF (pg/g d.w.) in surface sediment samples taken by a freeze-corer and a Limnos-corer. VCM production plant located in Sko1 ldvik. Samples of the humus layer of soil and mosses were collected from two sampling areas and from a background area. Soil samples, taken from the top 2 cm below the moss layer, were sieved to a diameter < 2 mm. In the collection of mosses (Pleurozium schreberi) a Finnish standard method was followed. The newest three shoots were dissected to separate the parts representing years 1991-1993. The fish species analyzed are listed in Table 1. Fish were caught from the sea areas outside the tunnel, and control fish were caught from a remote area with no known sources of pollution. The ages of the fish were relatively high, 9-14 years in all other species but Baltic herring, which were younger. Fish were analyzed in composite samples prepared from several individuals. Serum samples were collected from former workers of the VCM plant and from local residents. The residents were fishermen, and they were known to consume local fish in large amounts. Suitable control group data for the people from Sko¨ldvik were obtained from our previous study in which the ages of the individuals were in the same range as the ages of the people from Sko¨ldvik, 43-53 years. For each of the seven persons from Sko¨ldvik, two controls were selected with respect to their age, sex, and body weight index. The two control groups came from central Finland, Kuopio, and from southern Finland, Ka¨rko¨la¨.
Physical Analysis. Acoustic sediment profiling was used to distinguish the areas where accumulation of depositing material occurred from those of erosion or transportation. The sea bottom was echo-sounded along 23 lines in the archipelago. Sediment samples were taken for the determination of the following physical parameters: grain size distribution (9), water content (as weight loss on drying at 105 °C), and loss of ignition (as weight loss at 550 °C). Chemical Analysis. Prior to the PCDD/F and PCB analyses, samples were stored in a cold and dark place. Water samples were extracted by shaking three times with toluene. Other samples were freeze-dried, and their dry weights were determined. Samples were Soxhlet extracted for 24 h with toluene. Elemental sulfur from the sediment samples was precipitated with copper. All the extracts were purified over a silica gel column, PCDD/Fs and PCBs were fractionated from each other using an activated carbon-Celite column, and both fractions were further polished using an activated alumina column. The measurements were performed with a high-resolution mass spectrometer (HRMS) equipped with a fused silica capillary column (DB-DIOXIN). PCDD/F standards used contained 16 PCDD/F congeners, which were 13C labeled (115 pg/sample, ED-998 tetra- to octachlorodibenzo-p-dioxin standard solution and EF-999 tetra- to octachlorodibenzofuran standard solution, Cambridge IsoVOL. 34, NO. 13, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Ranges, Averages of Sum PCDD/F Toxicity Equivalents (I-TEQ), and Number of Composite Samples in Fish from Sko1 ldvik, in Fresh Weighta PCDD/F, Sko1 ldvik fish sculpin (Cottida gobio) pike (Esox lucius) pike perch (Lucioperca sandra) perch (Perca fluviatilis) viviparous blenny (Zoarces viviparus) flounder (Pleuronectes flesus) Baltic herring (Clupea harengus membras) small fish big fish a
range (I-TEQ, pg/g)
PCDD/F, background
av (I-TEQ, pg/g)
n
range (I-TEQ pg/g)
4.53
4.53
1
1.83
1.83
0.41-1.15
av (I-TEQ, pg/g)
n
0.53
0.53
1
1
0.74
0.74
1
0.71
3
0.39-0.63
0.48
3
0.92-10.7
4.69
4
1.05-1.47
1.30
3
1.54-4.10
2.82
2
2.22-5.21
3.72
2
7.79
7.79
1
2.43-3.02
2.73
2
1.31-7.74
2.73
13
3.03 8.72
3.03 8.72
1 1
A comparison with fish caught from the background area. Background data for Baltic herring is taken from ref 30.
tope Laboratories) and five PCB standards included four C-13 labeled congeners (960 pg/sample, IUPAC 30 [C-12 labeled], 80, 101, 153, and 180, Cambridge Isotope Laboratories). The standards were added to the samples before silica gel column elution. PCDD/F congeners present in the window of mass spectrometer and with the right isotope ratio of the specific congener were analyzed as “non-2,3,7,8-PCDD/Fs”. Analytical method for the determination of PCDD/Fs from serum samples is described in ref 10. The Laboratory of Chemistry, National Public Health Institute, has participated successfully in international quality control studies for the analysis of PCDD/Fs in many different matrices, organized by the European Community Bureau of Reference (EU/BCR) and WHO/EURO, and is an accredited testing laboratory (No. T77) in Finland (SFS-EN 45001 and ISO/IEC Guide 25). Concentrations in environmental samples are reported in PCDD/F and PCB sum concentrations and international toxicity equivalent, I-TEQ (11) in dry weight. Levels in fish are given as I-TEQ in fresh weight, to emphasize human exposure to PCDD/Fs via food.
Results and Discussion Waste Sludge. The analysis of a sludge sample confirmed that there were high concentrations, about 26 000 ng/g d.w., of PCDD/Fs in the production waste of the VCM plant. The most dominant congener was 1,2,3,4,6,7,8,9-octachlorodibenzofuran, octaCDF (19 000 ng/g dry weight, 73% of the total PCDD/Fs), followed by 1,2,3,4,6,7,8-heptaCDF (9.8%), non-2,3,7,8-substituted tetrachlorodibenzofurans (9.8%), and smaller amounts of non-2,3,7,8-substituted hexa- and heptachlorodibenzofurans (Table 2A,B). Thus, octaCDF turned out to be a suitable indicator of PCDD/F spreading in our study, making it easier to distinguish VCM source from other sources existing in the Baltic Sea. The most important congeners in terms of toxicity were 1,2,3,4,6,7,8-heptaCDF (31% of I-TEQ), 1,2,3,4,7,8-hexaCDF (26%), and octaCDF (23%). If WHO-TEQ (12) were applied instead of I-TEQ, the sludge containing high amounts of octaCDF would have a 26% lower toxicity. Formation of dioxins in the process had been almost negligible, since less than 1% of PCDD/Fs was dioxins. Octa- and heptachlorodibenzofurans were also dominant in the emissions of a Russian VCM plant (3), and they were detected in spent oxychlorination catalyst (13). PCDD/F levels (measured in TEQ) in ethylene dichloride (EDC), VCM, and PVC have mainly been below detection levels (3, 14, 15). 2686
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Another industrial process which produces high amounts of furans, but practically no dioxins at all, is chloralkali process. However, PCDF concentrations reported in chloralkali sludge (4) have been less than 3% of the concentrations detected in Sko¨ldvik. Landfill Sample. The sludge sample taken from one of the landfills contained 148 ng/g d.w. of PCDD/Fs, and again, almost 99% of them were furans. Differing from the sludge composition, the landfill sample contained more 1,2,3,4,6,7,8heptaCDF than octaCDF (31% and 20% of total PCDD/Fs, respectively). These findings may reflect heterogeneous composition of the sludge. However, concentration and composition of uncovered sludge may also have changed due to photochemical or other degrading process (16-18). Groundwater. PCDD/Fs had leached into the aquifer below the landfill, resulting in a groundwater concentration of 8.4 ng/L and a congener profile similar to that of the sludge. The level is elevated as compared with river water concentrations measured in the U.K., where the PCDD/F levels were below 6 ng/L (19). Considering the reported solubility of few nanograms per liter for hepta- and octachlorodibenzofurans (20), and the effects of cold temperature (21), the detected concentration also seems to be high. However, it was noticed that concentration in an unfiltrated groundwater sample was much higher than that reported above, obtained after filtration. A considerable part of PCDD/Fs in aquatic systems may actually belong to an apparently dissolved fraction, which means that they are associated with dissolved organic matter (22, 23). Enhancement in the theoretical solubility is also possible if the material disposed at the landfill contains suitable cosolvents, such as surfactants or mineral oil (2426). The two well water samples of 1-5 L did not contain measurable concentrations of PCDD/Fs. Brook Sediments. In a brook sediment sample taken close to the VCM plant PCDD/F concentrations were even higher than in the sludge disposed at the landfill (Table 2A,B). All the other samples were much cleaner (0.11-54.7 ng/g), showing that contamination was restricted to the vicinity of the sludge deposits at the industrial site (Table 3). Congener profiles were somewhat different from the waste sludge, probably due to the mixing of PCDD/Fs with different origins, and physicochemical transformations during the transport into the brooks and in the brooks (20, 22, 23, 27). Fish. In several fish species (perch, pike, sculpin, and flounder) I-TEQ was 2-9 times higher than in fish caught from the control area (Table 1). Elevated concentrations were
TABLE 2. PCDF and PCDD Congener Compositions in the Waste Sludge, the Most Polluted Brook Sediment, and at the Depth of Maximum Concentration in the Marine Sediment Core (All in Dry Weight), in Fish (Average of Four Composite Samples of Perch; in Fresh Weight), and in Human (Averages of Five VCM Plant Workers and Two Local Fishermen; in Fat)a waste sludge ng/g %
congener
brook sediment, ng/g
marine sediment, ng/g
fish: perch, ng/g f.w.
2378-Cl4DF other Cl4DFs 12378-Cl5DF 23478-Cl5DF other Cl5DFs 123478-Cl6DF 123678-Cl6DF 234789-Cl6DF 123789- Cl6DF other Cl6DFs 1234678-Cl7DF 1234789-Cl7DF other Cl7DFs OCDF PCDF sum I-TEQ sum (PCDF)
0.00 2550 13.7 16.5 189 210 48.3 2.04 0.00 585 2550 0.00 706 19000 25900 60.7
0.00 9.81 0.05 0.06 0.73 0.81 0.19 0.01 0.00 2.25 9.81 0.00 2.72 73.1 99.4 97.5
A. PCDF Congener Compositions 0.02 0.00 0.23 0.62 0.23 0.32 0.27 0.11 1.51 0.89 46.0 2.45 0.00 0.81 0.00 0.41 0.00 0.11 0.00 0.86 139 33.7 0.00 4.31 92.3 8.56 41.9 851 321 904 6.18 1.68
1.82 0.00 0.49 6.55 0.00 0.39 0.12 0.15 0.00 0.01 0.20 0.00 0.08 0.33 10.2 3.56
2378-Cl4DD other Cl4DDs 12378-Cl5DD other Cl5DDs 123478-Cl6DD 123678-Cl6DD 123789-Cl6DD other Cl6DDs 1234678-Cl7DD other Cl7DDs OCDD PCDD sum I-TEQ sum (PCDD)
0.36 0.12 0.60 2.85 0.38 0.96 0.27 4.88 13.4 6.88 116 147 1.56
0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.02 0.05 0.03 0.45 0.56 2.51
B. PCDD Congener Compositions 0.00 0.08 0.52 0.23 0.00 0.04 1.81 0.40 0.00 0.05 0.83 0.14 0.03 0.05 15.8 0.67 10.6 0.94 4.53 0.59 6.16 6.67 40.2 9.86 1.72 0.27
0.52 0.00 1.09 0.00 0.00 0.62 0.01 0.00 0.14 0.34 0.60 3.31 1.13
a
workers (fishermen), pg/g fat 5.50 (7.10) 0.64 (2.60) 38.4 (61.5) 12.9 (22.9) 12.1 (4.10) 1.40 (1.40) 0.00 (0.00) 68.3 (45.5) 0.00 (0.00) 75.8 (11.0) 215 (156) 34.9 (23.2) 2.60 (4.10) 11.6 (18.9) 0.00 (0.00) 70.1 (89.0) 5.76 (7.50) 67.5 (74.0) 394 (458) 552 (652) 17.1 (24.4)
Levels of non-2378-chlorinated congeners in human samples were negligible.
TABLE 3. Ranges and Means of PCDD/F Sum Concentrations, Sum of Toxicity Equivalents (I-TEQ), and Ranges of OctaCDF Concentrations Measured in Environmental Samplesa sludge at the site sludge at the landfill groundwater, landfill sediment core (97 cm) surface sediments brook sediments soil mosses a
PCDD/F, ng/g (mean)
I-TEQ, ng/g
octaCDF, ng/g
n
26 000 (26 000) 148 (148) 8.43 ng/L (8.43 ng/L) 4.95-914 (200) 0.10-4.46 (1.86) 0.32-361 (107) 20.6-34.9 (27.8) 2.95-17.1 (10.1)
81.1 3.57 0.02 ng/L 0.13-2.09 0.00-0.09 0.01-7.90 0.44-0.62 0.01-0.77
19 000 29.9 6.41 ng/L 2.42-851 0.00-1.47 0.10-113 11.4-19.3 0.46-3.24
1 1 1 34b 14 7 2 2
All in dry weight. Number of samples denoted by n.
b
Subsamples.
mainly due to the high amounts of hexa- to octachlorodibenzofurans, which usually are not predominant in fish samples regardless of the congener pattern in sediment (28, 29). In the average Sko¨ldvik fish PCDFs dominated by 77% of the total PCDD/Fs, whereas in the control fish the percentage of PCDFs was 53. In fish samples, 1,2,3,7,8pentaCDD contributed to the overall toxicity more than octachlorinated congeners. Therefore, WHO-TEQ was higher than I-TEQ. Differences within fish species were established, and they may result from the differing feeding habits and areas of the species. The most contaminated fish, flounder, feeds in the bottom of the sea. Compared to the background data which had revealed that Baltic herring (from the Gulf of Finland) typically accumulates 1 pg I-TEQ/g f.w. in a year (30), the levels measured in this study, 3.0 pg I-TEQ/g f.w. in small herring and 8.7 pg I-TEQ/g f.w. in bigger (older) herring, appear to be normal.
Soils and Mosses. Concentrations in the two composite samples taken close to the sludge ponds are shown in Table 3. A strong influence of the hepta- and octaCDF source was reflected in the congener profiles. Humus layer had accumulated PCDD/F deposition over a longer period of time, which is shown in levels higher than those detected in mosses. However, even lower levels in mosses might have been expected, since local source of atmospheric deposition no longer exists. Human Samples. The total PCDD/F concentrations in workers and fishermen from Sko¨ldvik did not differ from the concentrations in the two control groups (Figure 2). The workers, however, had a higher percentage of furans than the other groups, and one individual had an octaCDF concentration as high as 329 pg/g in fat. The normal octaCDF concentration range in humans is
