Environ. Sci. Technol. 2008, 42, 8252–8259
Concentrations, Profiles, And Estimated Human Exposures for Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans from Electronic Waste Recycling Facilities and a Chemical Industrial Complex in Eastern China J I N G M A , †,‡ K U R U N T H A C H A L A M K A N N A N , * ,‡ JINPING CHENG,† YUICHI HORII,‡ QIAN WU,‡ AND WENHUA WANG† School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China, and Wadsworth Center, New York State Department of Health, and Department of Environmental Health Sciences, School of Public Health, State University of New York at Albany, Empire State Plaza, P.O. Box 509, Albany, New York 12201-0509
Received June 26, 2008. Revised manuscript received September 9, 2008. Accepted September 10, 2008.
Environmental pollution arising from electronic waste (ewaste) disposal and recycling has received considerable attention in recent years. Treatment, at low temperatures, of e-wastes that contain polyvinylchloride and related polymers can release polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Although several studies have reported trace metals and polybrominated diphenyl ethers (PBDEs) released from e-waste recycling operations, environmental contamination and human exposure to PCDD/Fs from e-waste recycling operations are less well understood. In this study, electronic shredder waste and dust from e-waste facilities, and leaves and surface soil collected in the vicinity of a large scale e-waste recycling facility in Taizhou, Eastern China, were analyzed for total PCDD/ Fs including 2,3,7,8-substituted congeners. We also determined PCDD/Fs in surface agricultural soils from several provinces in China for comparison with soils from e-waste facilities. Concentrations of total PCDD/Fs were high in all of the matrices analyzed and ranged from 30.9 to 11400 pg/g for shredder waste, 3460 to 9820 pg/g dry weight for leaves, 2560 to 148000 pg/g dry weight for workshop-floor dust, and 854 to 10200 pg/g dry weight for soils. We also analyzed surface soils from a chemical industrial complex (a coke-oven plant, a coalfired power plant, and a chlor-alkali plant) in Shanghai. Concentrations of total PCDD/Fs in surface soil (44.5-531 pg/g dry wt) from the chemical industrial complex were lower than the concentrations found in soils from e-waste recycling plants, but higher than the concentrations found in agricultural soils. Agricultural soils from six cities in China contained low * Corresponding author phone: +518-474-0015; fax: +518-4732895; e-mail:
[email protected]. † Shanghai Jiao Tong University, ‡ Wadsworth Center and State University of New York at Albany. 8252
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levels (3.44-33.8 pg/g dry wt) of total PCDD/Fs. Profiles of dioxin toxic equivalents (TEQs) of 2,3,7,8-PCDD/Fs in soils from e-waste facilities in Taizhou differed from the profiles found in agricultural soils. The estimated daily intakes of TEQs of PCDD/ Fs via soil/dust ingestion and dermal exposure (2.3 and 0.363 pg TEQ/kg bw/day for children and adults, respectively) were 2 orders of magnitude higher in people at e-waste recycling facilities than in people at the chemical industrial site (0.021 and 0.0053 pg TEQ/kg bw/day for children and adults, respectively), implying greater health risk for humans from dioxin exposures at e-waste recycling facilities. The calculated TEQ exposures for e-waste workers from dust and soil ingestion alone were 2-3 orders of magnitude greater than the exposures from soils in reference locations.
Introduction Emission of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from the incineration of municipal solid wastes and as a byproduct of certain industrial processes has been studied for over 30 years (1). Although some sources of PCDD/Fs have been identified and global emission inventories have been estimated, contribution from electronic waste (e-waste) recycling operations is not well-known. In recent years, emission of toxic pollutants from e-waste recycling has been given considerable attention, because of the huge increase in the volume of e-waste generated annually (2-4). Approximately, 20-50 million metric tons of e-wastes are produced worldwide each year, of which 70% is exported to China for recycling (4). A recent study showed that 75% of the e-wastes produced in the United States have been exported to Southern China (5, 6). In addition, China discards about 4 million computers annually and this is expected to increase significantly (7). The techniques employed in e-waste recycling in certain countries are often primitive and hazardous, and include manual disassembly, roasting (use of dry heat), and open burning at low temperatures leading to environmental release of toxic pollutants and human exposures (8, 9). Polyvinyl chloride (PVC), the type of plastic accounting for the largest proportion by volume (26%) (10), and used in electronics as a packing material and as insulation for wires and other electronic parts, can generate PCDD/Fs during such crude recycling processes (3, 11). As a rapidly growing industry, e-waste recycling has caught the world’s attention as a new potential emission source of persistent organic pollutants (POPs). PCDD/Fs are POPs and are listed under the Stockholm Convention. Many countries, including China, have ratified the Stockholm Convention to reduce further emissions of POPs. Thus, there is a need for assessing and characterizing the sources and inventories of PCDD/Fs in China. The city of Taizhou in eastern China has one of largest e-waste recycling facilities and a nearly 30-year history in e-waste recycling. E-waste recycling employs around 40 000 people in Taizhou. Approximately 2.2 million metric tons of e-wastes are dismantled in Taizhou annually (7). The most intensive e-waste recycling is carried out in the town of Fengjiang (within Taizhou); this recycling base covers an area of 1.1 km2 and comprises more than 40 companies engaged in e-waste recycling. Two recent studies investigated PCDD/Fs contamination in human specimens from Taizhou and showed high concentrations of PCDD/Fs in human milk, placenta, and hair sampled from local residents (7). Concentrations of PCDD/Fs in surface soil collected from crop 10.1021/es8017573 CCC: $40.75
2008 American Chemical Society
Published on Web 10/22/2008
lands near e-waste recycling facilities were 13 times higher than the concentrations found in reference sites (11). Nevertheless, little is known about the sources and pathways of human exposure to PCDD/Fs in e-waste recycling sites. In this study, several environmental matrices, including obsolete electronic shredder waste, workshop-floor dust, leaves of trees and shrubs, and surface soil in the vicinity of the facilities, were analyzed, to enable the concentrations and profiles of PCDD/Fs in and around the facilities to be characterized. In addition to samples from e-waste recycling facilities, we also collected soil samples from a chemical industrial complex in Wujing Industrial area in Shanghai. Surface soil samples were collected from this industrial complex containing multiple chemical industries (notably PVC manufacture and a chlor-alkali industry), operating for 50 years. We also analyzed surface agricultural soils from seven cities in mid- and eastern- China, to gain an understanding of the sources and profiles of dioxin contamination in China. Human exposures to PCDD/Fs via dust and soil ingestion and dermal absorption from e-waste sites were estimated.
Materials and Methods Sample Collection. Three types of sampling locations were selected for this study; e-waste recycling facilities, chemical industrial complex and agricultural areas (see Supporting Information (SI) Figure S1). Multiple matrices, workshopfloor dust, electronic shredder waste, leaves from trees and shrubs, and surface soil, were collected in large scale e-waste recycling facilities at Fengjiang town in Taizhou (an urban area in Wenling was set as a reference site) in September 2007 (For details see SI Figures S1-S3). Surface soil samples were also collected from Wujing chemical industrial complex in Shanghai (a rural area was also set as a reference site) in September 2007 (For details see SI Figures S1 and S4). Surface agricultural soils (0-10 cm depth) were collected from Daqing, Chifeng, Lanzhou, Luoyang, Chengdu, Haikou, and Dexing during 2006-2007. For each location, several samples were pooled to yield a representative sample. Specially, in Dexing, four soil samples were collected around a large copper mine. All of the soil samples were collected using a clean stainless steel shovel at a depth of 0-10 cm. All collected samples were wrapped in solvent-cleaned aluminum foil and stored at -20 °C until analysis. Chemical Analysis. PCDD/F congeners were analyzed following the method described elsewhere with some modifications (12, 13). Further details are given in the Supporting Information. Extracts from the carbon column (F2) were injected into a high-resolution gas chromatograph (HRGC; Thermo Trace GC Ultra; Thermo Electron Corporation, Bellefonte, PA) coupled with a high-resolution doublefocusing mass selective detector (HRMS; Thermo DFS; Thermo Fisher Scientific, Bremen, Germany) at a resolving power of >10 000 (10% valley) for the determination of PCDD/F congeners. All of the congeners were quantified using the isotope dilution method based on the responses from the corresponding 13C12-labeled congeners. Identification of 17 2,3,7,8-substituted PCDD/F congeners was accomplished by injection of corresponding external standards of each of the congeners (Wellington Laboratories Inc., Guelph, ON). Identification of non-2,3,7,8-substituted congeners was accomplished based on the relative retention times and the chromatograms for 82 PCDF congeners and 46 PCDD congeners reported on a DB-5 fused-silica capillary column (14). Quality Assurance/Quality Control. Procedural blanks were analyzed with every 12 samples. Limits of quantification (LOQ) were estimated as 3 times mean value of blank (further details are in the Supporting Information). For TEQ calculations, values below the LOQ were assigned a value of one-
half of the LOQ, and the nondetects were set to zero. Recoveries of 13C12-labeled PCDD/Fs spiked into individual samples were 105 ( 29% for TCDD/F, 105 ( 28% for PeCDD/ F, 106 ( 30% for HxCDD/F, 101 ( 33% for HpCDD/F, and 84 ( 31% for OCDD. All of the concentrations presented are given on a dry weight (dw) basis. Statistical analyses were performed using SPSS version 15.0 software.
Results and Discussion E-Waste Facilities. Mean concentrations of 17 2,3,7,8substituted PCDD/Fs congeners, total PCDD/Fs (sum of 2,3,7,8-substituted and non-2,3,7,8-substituted congeners) and WHO-TEQs in soil, dust, leaf, and shredder-waste samples analyzed in this study are presented in Table 1 (range is given in SI Table S1). Total PCDD/F concentrations ranged from 30.9 to 11 400 pg/g for electronic shredder waste, from 3460 to 9820 pg/g for leaves, from 2560 to 148 000 pg/g for workshop-floor dust, and from 854 to 10 200 pg/g dry wt for soils. In particular, total PCDD/F concentrations in workshopfloor dust samples were approximately 11 times greater than the concentrations found in electronic shredder waste and soil samples, and 5 times higher than the concentrations in leaf samples (P < 0.05, independent t test). Mean concentrations of total PCDD/Fs in leaf samples were 2-fold higher than the concentrations found in surface soil samples. Reference soils collected from Wenling, 25 km south of e-waste recycling facilities, ranged from 72.8 to 456 pg/g dry wt, values approximately 16-fold lower (P < 0.05) than the concentrations in soils from e-waste recycling facilities. These results suggest that e-waste recycling is a potential emission source of PCDD/Fs. A recent study suggested that open burning of e-waste is a major source of PCDD/F emission in China (10). A gradient of decreasing total PCDD/F concentrations with increasing distance from e-waste facilities was found: large-scale e-waste facilities (this study) > crop lands around e-waste facilities (11) > remote reference sites (11) (3230 > 443 > 36.1 pg/g for total PCDD/Fs, respectively). This gradient indicates regional contamination due to atmospheric transport and deposition of PCDD/Fs from the e-waste recycling facilities (3). As in Taizhou, e-waste recycling facilities are located in Guiyu, a village located in southeastern China (3, 9, 15, 16). Previous studies found that soils collected from e-waste recycling facilities in Guiyu contained high concentrations of PCDD/Fs; a location close to acid leaching contained PCDD/F concentrations as high as 39 300 pg/g dry wt (3) and an open-burning area contained as high as 967 500 pg/g dry wt (17). To our knowledge, there are no chemical industries or municipal waste incineration facilities located near our sampling location in Taizhou. Thus, the elevated concentrations of PCDD/Fs in soils and other environmental matrices in our study implicate e-waste recycling as the major source of dioxin emission. E-waste recycling involves operations such as disassembly of the appliances with removal of the printed circuit board by flammable gas at certain temperatures, secondary aluminum smelting, acid baths, and burning of wires. Burning of wastes containing PVC can release PCDFs (29). Although studies have reported trace-metal, polybrominated diphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs) concentrations in dust samples collected from the floors of e-waste facilities (5, 8), PCDD/F concentrations in dust from e-waste recycling sites have not been determined previously. Our study shows that dust samples from e-waste recycling facilities are heavily contaminated with PCDD/Fs (up to 148 000 pg/g, dry wt). In terms of dioxin toxic equivalency (TEQ), the mean TEQ in dust samples was 1070 pg WHO-TEQ/g dry wt (Table 1). The congeners 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, and 2,3,4,7,8PeCDF together contributed to 40% of the total TEQ VOL. 42, NO. 22, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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leaves
1010 866 384 79.2 11.0 2350
53.1 83.8 143 172 138 589
636 513 342 1510 68.6 3070 3660 30.9-11400
total TCDF total PeCDF total HxCDF total HpCDF total OCDF total PCDFs total PCDD/Fs range
dust
10300 8850 6950 2960 450 29500 39800 2560-148000
882 18700 3050 3000 1560 10300
1740 333 681 1940 606 905 35.7 2380 581 450 9660 1070
17.9 68.0 86.0 206 263 1370 1560 3570
n)5
1210 475 229 106 32.6 2050 3230 854-10200
181 194 136 108 560 1180
96.4 22.7 35.6 56.1 21.9 21.1 0.57 95.1 10.8 32.6 393 49.3
1.46 5.22 4.05 8.32 12.2 52.9 560 645
n)5
large e-waste facilities
1200 789 436 193 57.8 2670 4250 1190-8160
160 189 402 279 553 1580
204 43.1 63.8 103 44.3 45.5 2.65 173 20.7 57.8 758 92.0
1.50 6.73 10.4 22.4 30. 8 137 553 762
n)5
household e-waste facilities (village)
soil
6.41 6.32 1.53 0.86 0.56 15.7 228 72.8-456
2.72 1.70 1.30 4.02 202 212
0.65 0.31 0.22 0.29 0.17 ND ND 0.86 ND 0.56 3.06 0.34
0.06 ND ND ND ND 1.47 203 204
n)3
reference site (Wenling)
56.0 48.5 28.0 20.0 49.8 202 290 44.5-531
15.5 10.2 10.4 13.6 38.2 87.9
9.57 13.7 2.41 8.19 2.91 1.60 0.46 17.1 2.89 49.8 109 5.35
0.19 0.47 0.41 1.18 1.08 5.59 38.2 47.1
n ) 12
industrial area
soil
21.7 9.46 6.88 3.30 3.44 44.8 203 62.0-222
7.80 8.44 7.12 14.5 121 159
2.27 0.92 0.65 1.62 0.80 0.59 0.25 2.43 0.87 3.44 13.8 1.77
0.09 0.51 0.38 0.55 0.58 5.23 121 128
n)2
reference site (rural)
chemical industrial complex
7.62 3.27 1.89 1.08 0.37 14.2 269 34.2-709
1.89 2.39 5.38 12.2 233 255
0.93 0.35 0.33 0.33 0.26 0.30 0.25 0.65 0.44 0.37 4.18 1.02
0.02 0.38 0.29 0.52 0.51 6.47 233 241
n)4
vicinity of copper mine
soil
5.09 1.49 0.67 0.58 0.24 8.06 18.7 3.44-33.8
1.44 1.68 1.08 0.69 5.71 10.6
0.78 0.15 0.11 0.15 0.09 ND 0.03 0.43 0.15 0.12 2.00 0.30
0.02 0.09 0.13 0.07 0.06 0.38 5.56 6.30
n)6
agriculture
other cities
a Mean concentration is expressed as pg/g dw and pg WHO-TEQ/g dw for PCDD/Fs and TEQs (1998 WHO-TEF were used). LOQ: TCDD/F ) 0.00-0.94, PeCDD/F ) 0.00-1.29, HxCDD/ F ) 0.00-1.17, HpCDD/F ) 0.49-1.74, OCDD/F ) 1.47-1.77. All concentrations calculated as ND ) 0, 45% of the sum of 2,3,7,8-substituted PCDD/Fs in electronic shredder waste. Formation of 1,2,3,4,6,7,8-HpCDF during pyrolysis of PVC in the presence of copper as a catalyst has been shown (29). HpCDF homologue was reported to be the major contributor to total PCDD/F concentrations in combusted residual waste and in soil from e-waste sites in Guiyu (3). Elevated composition of 1,2,3,4,6,7,8-HpCDF is characteristic of formation due to burning of PVC materials in e-waste recycling operations. The profile of 2,3,7,8-substituted PCDD/F congeners in soils from the industrial complex in our study was similar to the profile that has been reported for coal-fired power plants in Taiwan (23). It is suggested that PCDD/F contamination in the chemical industrial complex arises primarily from coal combustion although chlor-alkali processes (26) can also contribute to the formation. The major contributors to TEQs in environmental samples from e-waste recycling facilities were 1,2,3,7,8-PeCDD/F, 2,3,7,8-TCDF,and1,2,3,4,7,8-HxCDF.Nevertheless,1,2,3,4,6,7,8HpCDF contributed significantly to TEQs in electronic shredder wastes (SI Figure S6). Considerable variation in the contributions by individual PCDD/F congeners to TEQs in various sample matrices can be explained by differences in partitioning, diversity of source profiles, and the heterogeneous nature of the recycling operations. An earlier study showed (3) variations in TEQ profiles contributed by various kinds of e-wastes. VOL. 42, NO. 22, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 1. Profiles of 2,3,7,8-substituted congeners and total PCDD/F homologues in leaves (d, n ) 6), dust (a, n ) 5), surface soil (b, n ) 10) and electronic shredder waste (e, n ) 6) from Taizhou and surface soil from chemical industrial area (c, n ) 12) and agricultural soil (f, n ) 6). The data were normalized to total 2,3,7,8-substituted and total PCDD/F homologues, respectively. Exposure Assessment. Human exposures to PCDD/Fs through the ingestion and dermal absorption of dust and soils from e-waste recycling facilities were calculated based on the model proposed by Nouwen et al. (30) (see the Supporting Information for details). The rates of soil and dust exposures can vary between children and adults, due to the differences in the ingestion rate, body surface, and body weight (30, 31). The daily intake of PCDD/Fs calculated in this study can be compared with the data that have been reported previously (3, 11, 30, 31), notably from other e-waste recycling sites in China, and open landfill dumping sites in several Asian countries (Table 2 and SI Figure S7). The daily intake estimates of PCDD/Fs via soil/dust ingestion from e-waste sites were greater than the estimated intakes via dermal exposure. Daily intakes 8256
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of PCDD/Fs from all potential emission sources, including e-waste recycling facilities and open landfill sites were greater than the intakes estimated for reference sites. In addition, estimated intake rates of PCDD/Fs were higher for e-waste recycling sites and open landfill dumping sites than for the chemical industrial area, or near municipal waste incinerators. The estimated intakes of PCDD/Fs from soil/dust ingestion were greater in children than in adults, whereas dermal exposures contributed to greater PCDD/F intakes in adults than in children. Table 2 and Supporting Information Table S2 shows a comparison of estimated daily intake of PCDD/Fs from various exposure pathways (2, 3, 7, 32-35) in China. Although direct comparison of daily intake estimations from different exposure pathways reported in the literatures is confounded
TABLE 2. Estimated Daily Intakes (pg TEQ/kg bw/day) of PCDD/Fs for Children and Adults via Soil/Dust Ingestion and Dermal Exposure, and Comparison of Daily Intakes of PCDD/Fs from Various Exposure Pathways at Study Sites in China and other Asian Counties soil and dust ingestion studying areas large scale e-waste recycling base in Taizhou (this study) village dumping site in Taizhzou (this study) crop lands near large recycling plants in Taizhoua crop lands near small recycling workshop in Taizhoua acid leaching in Guiyub printer roller dump in Guiyub duck pond in Guiyub rice field in Guiyub reservoir in Guiyub Wujing chemical industrial area in Shanghai (this study) open dumping site in Philippinesc open dumping site in Cambodiac open dumping site in Indiac open dumping site in Vietnam-Hanoic open dumping site in Vietnam-Hochiminhc waste incinerators in Wilrijk, Belgiumd control site in Wenling (this study) E-waste recycling site in Guiyue (particle and gas) Guangzhou cityf (TSP inhalation) Guangzhou cityf (TSP and gas inhalation) E-waste recycling site in Taizhoug (milk) Heilongjiang, Liaoning and Hebei Provincesh (egg, aquatic foods, milk, meat) Henan, Shanxi and Ningxia Provincesh Jiangxi, Fujian Provinces and Shanghai cityh Hubei, Sichuan and Guanxi Provincesh Pearl River Delta areai (fish) Ya-Er Lake areaj (fish, meat, and aquatic plants)
children
adults
dermal exposure children
adult
air inhalation children
adult
dietary intake children
adult
4.84 × 10-2 0.141
2.25
0.222
0.306
2.69 × 10-2 5.49 × 10-2 6.39 × 10-2
3.75 × 10-2 3.30 × 10-3 0.67 × 10-2 0.78 × 10-2 5.13 × 10-2 4.50 × 10-3 0.92 × 10-2 1.07 × 10-2 1.68 1.62 ×
0.148 10-2
1.40 ×
0.302 10-3
0.29 ×
0.351 10-2
0.34 × 10-2
0.113 9.90 × 10-3 2.03 × 10-2 2.36 × 10-2 3.89 × 10-2 3.40 × 10-3 0.70 × 10-2 0.81 × 10-2 2.70 × 10-3 0.20 × 10-3 0.50 × 10-3 0.60 × 10-3 1.78 × 10-2 1.6 × 10-3
0.32 × 10-2 0.37 × 10-2
1.82
0.160
0.326
0.379
1.33
0.117
0.238
0.277
0.173
1.52 × 10-2 3.10 × 10-2 3.61×× 10-2
0.341
2.99 × 10-2 6.11 × 10-2 7.11×× 10-2
8.90 × 10-3 0.80 × 10-3 0.16 × 10-2 0.19 × 10-2 6.81 × 10-2 7.90 × 10-3 1.47 × 10-2 0.73 × 10-2 1.10 × 10-3 0.10 × 10-3 0.20 × 10-3 0.20 × 10-3 4.50
2.54
*6.38 × 10-2 *4.84 × 10-2 *8.97 × 10-2 *6.93 × 10-2 103 0.41 0.09 0.59 0.22 0.47 *9.14
a Data (mean concentration) cited from ref 11, and all the I-TEQ data were transformed into 1998 WHO-TEQ when possible. b Data (mean concentration) cited from ref 3. c Data cited from ref 31. d Data cited from ref 30. e Data cited from ref 2. f Data cited from ref 35. g Data cited from ref 7. h Data cited from ref 33. i Data cited from ref 34. j Data cited from ref 32. * The daily intake values cited are in pg I-TEQ/kg bw/day.
by the treatment of data for nondetects (0, LOD, or 1/2LOD), type of TEFs used (I-TEF or WHO-TEF), and average body weight, some generalizations can be made with regard to overall exposures at e-waste sites. First, for nondietary exposure pathways including soil/dust ingestion, dermal
exposure, and air inhalation, the estimated daily intakes of PCDD/Fs from e-waste recycling sites (both in Taizhou and Guiyu) (2, 3, 7) are 1 or 2 orders of magnitude higher than that in non-e-waste recycling regions, such as chemical industrial area in Shanghai (this study) and Guangzhou cities VOL. 42, NO. 22, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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(35). For the dietary intakes pathway, the values of PCDD/Fs daily intakes (milk) in Taizhou (7) are also greater than the intakes (egg, fish, milk) from non-e-waste recycling regions in China (31-33) (on the basis of per kg body weight). Second, the estimated daily intake of PCDD/Fs from nondietary routes of exposures including soil/dust ingestion and dermal exposure alone at e-waste recycling sites (2, 3, 7) is similar to the dietary intake values at nonwaste sites in China (31-33). The estimated daily intake of soil/dust ingestion and dermal exposure for children in Taizhou (2.3 pg TEQ/kg bw/day) is in the range of the WHO value for tolerable daily intake (TDI; 1-4 pg TEQ/kg bw/day) (36). For the overall general population, dietary intake is the major source (>70%) of PCDD/F exposures, whereas nondietary sources contribute only a small portion (
