Environ. Sci. Technol. 2001, 35, 448-454
Flame Retardants in Indoor Air at an Electronics Recycling Plant and at Other Work Environments ANDREAS SJO ¨ D I N , † H A° K A N C A R L S S O N , ‡ KAJ THURESSON,† SVERKER SJO ¨ LIN,§ A° K E B E R G M A N , * , † A N D C O N N Y O ¨ STMAN‡ Departments of Environmental Chemistry and Analytical Chemistry, Stockholm University, SE-106 91 Stockholm, Sweden, and Stena-Technoworld AB, Box 80, SE-370 10 Bra¨kne-Hoby, Sweden
Air samples from a plant engaged in recycling electronics goods, a factory assembling printed circuit boards, a computer repair facility, offices equipped with computers, and outdoor air have been analyzed with respect to their content of brominated hydrocarbon and phosphate ester flame retardants. Polybrominated diphenyl ethers, polybrominated biphenyls, 1,2-bis(2,4,6-tribromophenoxy)ethane, tetrabromobisphenol A, and organophosphate esters were all detected in the indoor air samples, with the highest concentrations being detected in air from the recycling plant. In air from the dismantling hall at the recycling plant the average concentrations of decabromodiphenyl ether, tetrabromobisphenol A, and triphenyl phosphate were 38, 55, and 58 pmol/m3, respectively. Significantly higher levels of all of these additives were present in air in the vicinity of the shredder at the dismantling plant. This is the first time that 1,2-bis(2,4,6-tribromophenoxy)ethane and several arylated phosphate esters are reported to be contaminants of air in occupational settings. At all of the other sites investigated, low levels of flame retardants were detected in the indoor air. Flame retardants associated with airborne particles, present at elevated levels, pose a potential health hazard to the exposed workers.
Introduction Flame retardants are used in, e.g., plastics, rubbers, and textiles to prevent or retard the initial phase of a developing fire (1-3). Thus, these chemicals are present in numerous products, including construction materials, upholstery, carpets, and electronic goods such as computers and TV sets. The quantity and type of flame retardants employed depends on the application and fire protection requirements. For example, 5-30% of the weight of polymeric material may consist of flame retardant additives (1). In 1992 the worldwide usage of flame retardant chemicals was estimated to be 600 000 metric tones (4). According to this same report, 25% of these compounds contained bromine, while 17% were organophosphorus additives. Flame retardants are used either as additives (i.e., they are mixed with the polymer) or coreactants (in which case the reactive flame retardant is covalently bound to the * Corresponding author phone: (+46) 8-16 39 97; fax: (+46) 8-15 25 61; e-mail:
[email protected]. † Department of Environmental Chemistry, Stockholm University. ‡ Department of Analytical Chemistry, Stockholm University. § Stena-Technoworld AB. 448
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polymer). Polybrominated diphenyl ethers (PBDEs) and organophosphate esters are examples of flame retardants additives. The latter substances also possess plasticizing properties. Tetrabromobisphenol A (TBBPA) can be used either as an additive or a reactive flame retardant (2). Additives that are not chemically bound to the polymer matrix may leak out into the environment at any time during the production, lifetime, or destruction of the product. Organophosphate esters have been detected in the air and floor dust of offices (5-8). Recently, nine different organophosphate esters were identified in air samples from a number of common indoor work environments (9). These compounds were found to be strongly associated with the particulate phase. Furthermore, the plastic material in the outer cover of computer VDUs (video display units) has been shown to be a source of emission of triphenyl phosphate into indoor environments (10). Organophosphate esters have also been detected in outdoor environments, including sediment, the aquatic environment, and soil (11, 12). In Sweden, PBDEs and TBBPA have been identified in airborne particles in offices containing computers (13) and in sediment and sewage sludge (14). Neutral and lipophilic compounds, including PBDEs, have been shown to accumulate in birds, fish, and mammals (15) including humans (16, 17). Recently, the levels of eight tri- to hexabrominated PBDE congeners in breast milk from Swedish mothers have been shown to have increased dramatically during the last few decades (16). According to this later report, PBDE levels in breast milk have, on the average, doubled every 5 years from 1972 to 1997. The knowledge concerning toxicity of most flame retardants is still limited, although reviews dealing with PBDEs (1), TBBPA (2), and certain of the organophosphorus compounds (18, 19) indicate that these compounds may pose a threat to human health. Additional toxicological studies are now in progress. Recycling of electronic goods is a growing industry. In connection with recycling electronic products are dismantled into several categories of material, such as printed circuit boards, electric components, plastics, metals, and hazardous waste. Our hypothesis was that flame retardants are released during this dismantling process, thus posing a potential occupational health hazard. The aim of the present study was to test this hypothesis by determining the concentrations of flame retardants in the air at a plant for recycling electronic goods and comparing these levels to those present in other indoor work environments where electronic products are manufactured, repaired or used. For these analyses polybrominated hydrocarbons and organophosphate esters were employed as representative flame retardants.
Experimental Section Chemicals. All reference substances used in the present study are listed in Table 1. Methyl diphenyl phosphate (MDPP), 2,2′,3,3′,4,4′-hexabromodiphenyl ether (BDE-128), and 3,3′,5′tribromo-5-chlorobisphenol A (TrBCBPA) were used as internal surrogate standards for the quantification of organophosphate esters, PBDEs and TBBPA, respectively. TrBCBPA was prepared from 3,3′,5-tribromobisphenol A and chlorine as described elsewhere (20). The commercial octa-BDE products, Bromkal 79-8DE and Great Lakes DE79, were from Chemische Fabrik Kalk (Ko¨ln, Germany) and Great Lakes Chemical Corporation (West Lafayette, U.S.A.), respectively. Diazomethane, used for the derivatization of phenolic compounds, was prepared from N-methyl-Nnitroso-p-toluenesulfonamide (Diazald) (21) obtained from 10.1021/es000077n CCC: $20.00
2001 American Chemical Society Published on Web 12/22/2000
TABLE 1: Reference Standards Employed for Quantitation and Identification and Reference for Their Synthesis or Origink abbreva
compound
Polybrominated Diphenyl Ethers 2,2′,4,4′-tetrabromodiphenyl ether BDE-47 2,2′4,4′,6-pentabromodiphenyl ether BDE-100 2,2′,4,4′,6-pentabromodiphenyl ether BDE-99 2,2′,3,4,4′-pentabromodiphenyl ether BDE-85 2,2′,4,4′,5,6′-hexabromodiphenyl ether BDE-154 2,2′,4,4′,5,5′-hexabromodiphenyl ether BDE-153 2,2′,3,3′,4,4′-hexabromodiphenyl ether (IS) BDE-128 2,2′,3,4,4′,5′,6-heptabromodiphenyl ether BDE-183 octabromodiphenyl ether octa-BDE:1-4b nonabromodiphenyl ether nona-BDE:1-3b 2,2′,3,3′,4,4′,5,5′,6,6′-decabromodiphenyl ether BDE-209 1,2-bis(2,4,6-tribromophenoxy)ethane decabromobiphenyl tribromochlorobisphenol A (IS) tetrabromobisphenol A
Other Brominated Flame-Retardants BTBPE BB-209 TrBCBPA TBBPA
synthesis ref (26) (27) (26) (26) (27) (26) (26) (17) c c d
e f (20) g
triphenyl phosphate isopropylphenyl diphenyl phosphate propylphenyl diphenyl phosphate tert-butylphenyl diphenyl phosphate
Arylated Organophosphate Esters TPP IPPDPP PPDPP:1-2 TBPDPP
g h h i
methyl diphenyl phosphate tri(n-butyl) phosphate tris(2-chloroethyl) phosphate tris(chloropropyl) phosphate tris(2-butoxyethyl) phosphate
Alkylated Organophosphate Esters MDPP TBP TCEP TCPP:1-3 TBEP
g g g j g
a PBDEs and BBs have been assigned numbers according to ref 28. b Several structurally uncharacterized isomers, denoted with Arabic numbers. Technical product, Bromkal 79-8DE, Chemische Fabrik Kalk, Germany. d From Fluka Chemie, Switzerland. e Kind gift from L. Asplund. f From Cambridge Isotope Laboratories, U.S.A. g From Aldrich Chemicals, Germany. h Technical product, Phosflex 31 P, from Akzo Nobel, Sweden. i Technical product, Phosflex 71 B, from Akzo Nobel, Sweden. j Kind gift from Akzo Nobel, Sweden. k These compounds are listed in the order in which they elute from a DB-5 gas chromatography capillary column (cf. Figure 2). Abbreviations: IS, internal surrogate standard. c
Sigma-Aldrich (Steinheim, Germany). n-Hexane and dichloromethane (DCM), distol grade, were purchased from Fisher Scientific (Leicestershire, U.K.). Methyl tert-butyl ether (MTBE), HPLC grade, was supplied by Rathburn Chemicals (Walkerburn Scotland, U.K.). Methanol and acetone of analytical grade and silica gel (0.063-0.200 mm) were purchased from Merck (Darmstadt, Germany). All solvents, with the exception of methanol, were glass-distilled prior to use. Air Sampling Equipment. Stationary air sampling was performed by personal sampling equipment, as described previously (22). The sampler was made from anodized aluminum. A 25-mm, binder-free A/E borosilicate glass fiber filter (Gelman Sciences Inc., Ann Arbor, MI) and two cylindrical polyurethane foam (PUF) plugs with a diameter of 15 mm and a thickness of 15 mm (Specialplast AB, Gillinge, Sweden) were used to trap the particulate and the semivolatile associated fractions, respectively. Semivolatiles are defined as the fraction of the sample passing through the filter and being retained in the PUF adsorbent. The second PUF plug was added in order to detect possible breakthrough of more volatile compounds through the first plug. Air was pumped through the sampler by a personal battery-operated pump (224-PCXR7, SKC Inc., Eighty Four, PA) at a flow rate of 3.0 L/min. Samples were collected during a 500-min period, corresponding to a total volume of 1.5 m3 air. However, one should be aware of a problem associated with this type of air sampling, namely the risk of overestimation of the semivolatile phases. This is due to the possibility of migration of the compounds adsorbed on the particles or the filter into the PUF adsorbent. To enable the identification of unknown substances in
the air, larger samples were collected using pumps of higher capacity (KNF, Neuburger, Freiburg, Germany). In these cases, the same sample holder as that described above was used for collection, but with the addition of a cellulose AP10 support pad, placed between the glass fiber filter and the PUF adsorbent (Millipore, U.S.A.). These samples were collected at a flow rate of 9.0 L/min for 400 min, yielding a total sample volume of 3.6 m3 air. Prior to use, each sampler was rinsed with DCM. The glass fiber filters were sonicated for 20 min each in, first, methanol, then, acetone, and, finally, DCM. The PUF adsorbents were first boiled in water for 4 h in order to eliminate compounds containing nitrogen, such as isocyanates, which could interfere with gas chromatographic detection using the nitrogen phosphorus detector (NPD). Subsequently, the PUFs were washed sequentially with water, acetone, and DCM, and, finally, they were Soxhlet-extracted for 12 h in DCM. After these treatments, no organophosphorus or brominated compounds originating from the sampling equipment (background) were detectable. For storage, filters, PUFs, and samplers were wrapped in aluminum foil prerinsed with DCM. Sampling Sites. Samples were collected from six different indoor environments as well as at one outdoor site. To obtain duplicate samples, two personal samplers were deployed at each location investigated. Plant for Recycling of Electronic Products. At this plant discarded electronic equipment, such as computers, printers, TV sets, microwave ovens, and numerous other electronic goods, are dismantled in order to recover valuable metals and dispose adequately of hazardous components. The plant contains three major areas, i.e., (I) a dismantling hall including VOL. 35, NO. 3, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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a large storage area for incoming electronic equipment, (II) a shredder and picture tube dismantling room, and (III) offices and other areas. The dismantling process is performed manually using pneumatic tools. The electronic goods are separated into several types of materials, i.e., plastics, printed circuit boards, cables, metals, and hazardous waste. Plastic housings and other plastic components are shredded to reduce their volume. One employee, using a paper filter covering mouth and nose for dust protection, works at the shredder. VDUs and TV sets are handled separately. The outer cover is removed in the dismantling hall, and the picture tube is further dismantled into several components in area II. Air samples were collected during the course of 2 working days. Eight low-volume samplers, deployed in pairs at four different locations, were employed each day. Pairs of samplers were placed at three individual work stations in the dismantling hall and at the shredder. In the dismantling hall the samplers were placed on a clean shelf at each of the work stations at a height corresponding to the breathing zone of the workers and 1-1.5 m to the side of the worker not to hinder them in their work. The samplers at the shredder were placed on a clean shelf 1.8 m above the floor and approximately 2 m from the conveyor belt transporting plastics to the shredder. In addition, one high-volume sampler was placed in the vicinity of the shredder and another in the dismantling area each day of sampling. During the first day of air sampling, only plastics containing no brominated flame retardants were ground up. During the second day, only plastics which did contain brominated flame retardants were processed. Plastics were designated as containing or not containing brominated additives on the basis of X-ray fluorescence (X-Met, Metorex, Estoo, Finland). Factory for Assembling Circuit Boards. Samples were collected during the course of a single working day, at three different locations within the facility. These sites were close to an automated oven used for soldering components onto the circuit boards, 5 m away from this oven and at a working site in an adjacent room where components were soldered manually onto circuit boards. The site for manual soldering was equipped with spot ventilation. Facility for Repairing Computers. The major tasks performed at this facility are the assembly of new and repair of broken computers. Air samples were collected during the course of 1 day in a workshop housing one employee. Computer Teaching Hall and Offices. In a teaching hall containing 20 computers and two offices with two or three computers, air samplings were carried out during the course of one working day each. Outdoor Environment. To verify that the sampling equipment did not produce any artifacts, outdoor air was collected in a suburban area close to Stockholm. Sample Preparation. Extraction. To distinguish between the particulate associated and semivolatile phases, filters and PUFs were processed separately. The internal surrogate standard employed for quantitation of the organophosphate esters was added prior to the extraction of the filters and PUF plugs. In contrast, the internal surrogate standards for quantitation of brominated flame retardants were added after analysis of the organophosphate esters had been completed, to avoid interference by phosphorus-containing contaminants originating from Teflon-lined screw-caps used during the preparation of these standards. Extraction was carried out by DCM (5 mL, 20 min) using a Bransonic 220 ultrasonic bath, with an output power of 50 W and a frequency of 48 kHz. This extraction procedure was repeated once using fresh solvent. Cleanup. The volume of the pooled sample extracts (10 mL) was reduced to 100 µL by evaporation at room tem450
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perature under a gentle stream of nitrogen. For analysis of organophosphate esters, samples were injected onto a GC equipped with a nitrogen-phosphorus detector (NPD). The solvent was changed by adding hexane (4 mL) and subsequently reducing the sample volume to 100 µL, after which this procedure was repeated once more. Phenolic compounds were partitioned into potassium hydroxide (0.5 M in 50% ethanol, 2 mL), the organic phase containing neutral substances was removed, and the aqueous phase was thereafter extracted with hexane (2 mL). The pooled organic phases were designated as the neutral fraction. After acidification of the aqueous phase with hydrochloric acid, phenolic compounds were extracted into hexane/MTBE (1:1). After reducing the volume of this organic phase to 1 mL, phenolic compounds were allowed to react with diazomethane (200 µL) for 1 h in a refrigerator. Excess reagent and solvent were removed by evaporation under a gentle steam of nitrogen. The phenolic derivatives were then subjected to further cleanup on a silica gel/sulfuric acid column (2:1 weight/ weight, 0.3 g), employing DCM (8 mL) as the mobile phase. Neutral compounds were cleaned up on a silica gel/sulfuric acid column (0.5 g), using hexane (8 mL) as the mobile phase. Finally, the samples were analyzed by gas chromatography/ mass spectrometry (GC/MS). Instrumentation. GC/NPD. Quantitative GC analysis of organophosphate esters was performed utilizing a CEInstruments 8000 Top gas chromatograph equipped with a DB-5 column (30 m, 0.25 mm i.d., 0.10 µm film thickness; J&W Scientific, Folsom, CA) and a TS-2 NP-detector. Nitrogen was used as both carrier and makeup gas. The column temperature was programmed as follows: 35 °C (2 min), 10 °C/min up to 300 °C. Injections were carried out in the splitless mode, and the split then opened 2 min after the injection. The temperature of the injector and detector was maintained at 300 °C. A personal computer-based laboratory system (ELDS Win Pro, Chromatography Data System AB, Svartsjo¨, Sweden) was used to acquire and process the data obtained. GC/Electron Capture Detector (ECD). Gas chromatography with electron capture detection was performed on a Varian 3400 GC equipped with a DB5-HT capillary column (15 m, 0.25 mm i.d., 0.1 µm film thickness; J&W Scientific, Folsom, CA). Hydrogen was used as carrier gas and nitrogen as the makeup gas. The column temperature was programmed as follows: 80 °C (2 min), 15 °C/min up to 300 °C (16 min). Injections were carried out in the splitless mode, and the split then opened 2 min after injection. The temperatures of the injector and detector were maintained at 250 °C and 360 °C, respectively. The software employed in the case of GC/ NPD was also utilized here for acquisition and processing data. GC/MS. An Automass 2 system (ThermoQuest, Bremen, Germany) was utilized for GC/MS analysis of organophosphate esters. The GC was equipped with a DB-5 column, and the same temperature program as in the case of GC/NPD was employed. The split/splitless injector was maintained at 300 °C. Helium was used as the carrier gas, and the temperature of the transfer line between the GC and the mass spectrometer was maintained at 310 °C. Analyses were performed in the electron ionization mode (EI) with an applied ionization energy of 70 eV. GC/MS Electron Capture Negative Chemical Ionization (ECNI). Quantitative analysis of the brominated flame retardants was performed utilizing a Finnigan TSQ 700 instrument (ThermoQuest, Bremen, Germany) connected to a Varian 3400 gas chromatograph. On-column injections were carried out by a septum-equipped programmable injector (SPI), fitted with a high performance insert. The injector temperature was programmed as follows: 60 °C, 180 °C/min up to 320 °C. A DB5-HT capillary column (15 m, 0.25 mm i.d., 0.1 µm film thickness; J&W Scientific) was
TABLE 2: Total Concentrations (ng/m3) of Particle-Associated and Semivolatile Brominated Flame Retardants and of Particle-Associated Organophosphate Esters in Air from the Plant for Recycling Electronic Productsa dismantling hall
shredder
compound
(n ) 12) mean
BDE-47 BDE-100 BDE-99 BDE-85 BDE-154 BDE-153 BDE-183 BDE-209
1.2 0.25 2.6 0.17 0.57 3.9 19 36
Polybrominated Diphenyl Ethers 0.35-2.1 0.063-0.52 0.54-5.5 0.10-0.24 0.13-1.0 0.88-11 6.3-44 12-70
BTBPEb BB-209 TBBPAb,c
20 5.4 30
Other Brominated Flame Retardants 5.6-67 1.6-14 6.9-61
23; 32 8.8; 9.7 34; 41
140; 150 55; 57 130; 150
TPP IPPDPP PPDPP:1 PPDPP:2 TBPDPP
19 7.7 3.1 1.9 0.80
Arylated Organophosphate Esters 12-40 3.4-15 1.3-5.1 0.7-3.1 0.2-1.9
160; 160 97; 100 36; 39 26; 26 15; 16
120; 180 54; 84 20; 30 16; 22 17; 19
TBP TCEP TCPP:1 TCPP:2 TCPP:3 TBEP
14 25 14 5.7 1 29
Alkylated Organophosphate Esters 9-18 15-36 10-19 3.7-7.1 0.6-1.5 20-36
15; 19 28; 34 15; 21 7.5; 10 2.1; 2.1 17; 19
10; 24 33; 38 15; 23 8; 12 2.2; 2.9 20; 24
range
non-BFR (n ) 2) levels
BFR (n ) 2) levels
1.4; 1.6 0.32; 0.32 1.9; 2.0 0.17; 0.17 0.87; 1.8 5.0; 5.0 29; 29 57; 58
2.0; 2.1 0.56; 0.61 4.0; 4.5 0.42; 0.52 2.4; 2.4 14; 15 84; 87 150; 200
a For compound abbreviations, see Table 1. The compounds are listed in the order in which they elute from a DB-5 gas chromatography capillary column (cf. Figure 2). Abbreviations: non-BFR, during processing of plastics without brominated additives; BFR, during processing of plastics containing brominated additives. b Minimum value, due to low recovery for this compound. c Quantification on the basis of a volumetric standard.
employed, with helium as the carrier gas at a column head pressure of 3 psi. The column temperature was programmed as follows: 80 °C (1 min), 15 °C/min up to 300 °C (16 min). The ion source was maintained at 200 °C and a pressure of 6.5 Torr. Bromine containing substances were quantitated on the basis of the negative ions formed by electron-capture reactions at chemical ionization, utilizing a primary electron energy of 70 eV. Selective monitoring of ions (SIM) at m/z 79 and 81 was employed (23). Methane (quality 4.5, e 5 ppm O2, AGA, Stockholm, Sweden) was used as the reagent gas. Identification of unknown substances was achieved by GC/MS in the EI mode (70 eV), utilizing the same Finnigan TSQ 700 instrument and monitoring the mass range m/z 100-1000. The parameters for GC were the same as those employed for the ECNI quantitation described above. ICIS2 software (ThermoQuest, Bremen, Germany) was utilized for collecting and processing the GC/MS data. Identification and Quantitation. Identification of brominated flame retardants and of organophosphate esters present in the samples was based on comparison of the retention times of these components with those of authentic reference substances. The technical products Bromkal 798DE and Great Lakes DE79 were employed for the identification of octa- and nona-BDEs, due to the lack of standards. The identities of PBDE congeners containing seven or more bromine atoms, of 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), of TBBPA, and of the organophosphate esters were also verified by full scan GC/MS, utilizing the high-volume samples collected at the recycling plant (see above). The recoveries of the brominated flame retardants in connection with the extraction and cleanup procedures were determined by adding 10 ng of each compound to clean filters. These samples were extracted, cleaned up, and subsequently analyzed by GC/ECD using 2,3,3′,4,4′,5,5′-
heptachlorobiphenyl (CB-189) as a volumetric standard. The average recoveries of ten PBDE congeners containing 4-10 bromine atoms of BTBPE and of TBBPA were 97% (SD ) 4%, n ) 5), 23% (SD ) 3%, n ) 5), and 60% (SD ) 10%, n ) 5), respectively. In the case of all organophosphate esters analyzed, recoveries were >95% (9). Quantitation of all brominated flame retardants was performed by GC/MS (ECNI), using calibration curves prepared at five levels. The values reported for BTBPE and TBBPA (Tables 2 and 3) should be considered as minimum concentrations, because of the low recoveries of these compounds. The limit of quantification (LOQ) for brominated flame retardants was defined as 10 times the average background in blank samples due to small amounts of interfering peaks present in the blank samples. This limitation was of practical significance only for the sites documented in Table 3. In samples from the recycling facility the amount of BDE47 (the most volatile of the compounds studied) recovered from the second PUF plug was only 4% (SD ) 2%, n ) 15) of that recovered from the first PUF plug. Consequently, for all of the other sampling sites (Table 3), only the first PUF plug was analyzed. The organophosphate esters were quantitated using single-point calibrations.
Results Eight PBDE congeners including decabromodiphenyl ether (BDE-209), decabromobiphenyl (BB-209), BTBPE, TBBPA, and five arylated and six alkylated organophosphate esters were identified and quantitated in the air samples from the recycling plant (Table 2). The concentrations of the brominated hydrocarbon and organophosphate ester flame retardants are presented in Table 2 and Figure 1. Representative VOL. 35, NO. 3, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 3: Total Concentration (ng/m3) of the Particle-Associated and Semivolatile Brominated Flame Retardants (Corrected for the Background in Blank Samples), in Other Working Environmentsa
compound
assembly of circuit boards (n ) 6) meanb range
no quant.c
office with computers (n ) 4) meanb range
no quant.c
computer repair facility (n ) 2) levels
teaching hall (n ) 2) levels
outdoors (n ) 2) levels
0.0069 0.019 0.053 0.22
