Exposure to
polybrominated diphenyl ethers and tetrabromobisphenol A
among computer technicians
Chemosphere 46 (2002) 709-716 v.46, i.5, Feb02
Mindfully.org note: This issue of Chemosphere has many more articles on PBDEs
Kristina Jakobsson a,*, Kaj Thuresson b, Lars Rylander a, Andreas Sjödin b,l, Lars Hagmar a, Ake Bergman b
a Department of Occupational and Environmental Medicine, Lund University Hospital, S-221 85 Lund, Sweden
b Department of Environmental Chemistry, Stockholm University, S-106 91 Stockholm, Sweden
*Corresponding author. Fax: +46-46-173180.
E-mail address: kristina.jakobsson@ymed.lu.se (K. Jakobsson).
1 Present address: Toxicology Branch, Laboratory Sciences Division, National Center for Environmental Health, Center for Disease Control and Prevention (CDC), 4770 Buford Hwy NE, Atlanta, GA 30341-3724, USA.
Abstract
This study investigates exposure to polybrominated diphenyl ethers (PBDEs) and tetrabromobisphenol A (TBBPA), which are used as flame retardants in electronic equipment, in a group of technicians with intense computer work.
Thirteen PBDE congeners and TBBPA were quantified in serum from 19 computer technicians. Previously investigated groups of hospital cleaners with no computer experience, and clerks working full-time at computer screens were used for comparison. The computer technicians had serum concentrations of BDE-153, BDE-183 and BDE-209 that were five times higher than those reported among hospital cleaners and computer clerks. The median levels observed among the computer technicians were 4.1, 1.3, and 1.6 pmol/g lipid weight, respectively. In contrast, for BDE-47 there was no difference between the computer technicians and the others.
BDE-100, BDE-203, and three structurally unidentified octa-BDEs and three nona-BDEs, were present in almost all samples from the computer technicians. Further, TBBPA was detected in 8 out of 10 samples. The levels of BDE-153, BDE-183, and one of the octa-BDEs were positively correlated with duration of computer work among technicians.
On a group level an exposure gradient was observed, from the least exposed cleaners to the clerks, and to the highest exposed group of computer technicians. A dose (duration of computer work)-response relationship among computer technicians was demonstrated for some higher brominated PBDE congeners. Thus, it is evident that PBDEs used in computers and electronics, including the fully brominated BDE-209, contaminate the work environment and accumulate in the workers tissues.
Keywords: Brominated flame retardants; Computer work; Occupational exposure; PBDEs; TBBPA; VDU
1. Introduction
Polybrominated diphenyl ethers (PBDEs) and tetrabromobisphenol A (TBBPA) are brominated aromatic hydrocarbons, which have been extensively used as flame retardants over the last few decades (IPCS, 1994; IPCS, 1995; BSEF, 2000). PBDEs are blended with polymers which are used in electrical and electronic equipment, and in other plastic goods, coatings, cables, construction materials, and textiles. Thus, they are found in many common goods, including computers. TBBPA is mainly applied as a reactive flame retardant in printed circuit boards but may also be used as an additive, as the chemical itself, or as derivatives of TBBPA (IPaCS, 1995).
There are theoretically 209 congeners of PBDE that can be numbered using the numbering system of
polychlorinated biphenyls (PCBs) (Ballschmiter et al., 1993). However, technical PBDE products, manufactured as mixtures of penta-, octa-, and decabromodiphenyl ethers, consist of a much more limited number of PBDE congeners than technical PCBs (Schultz et al., 1989; Sjödin et al., 1998; Sjödin, 2000). Basically all PBDE congeners in commercial products with up to seven bromine atoms have been structurally identified (Sjödin et al., 1998; Sjödin, 2000). Globally, around 67,000 and 120,000 metric ton/yr of PBDEs and TBBPA, respectively, were produced in 1999 (BSEF, 2000).
PBDEs are persistent, lipophilic, and bioaccumulating chemicals of anthropogenic origin, thus presenting a potential threat to wildlife and humans. Human PBDE concentrations are still significantly lower than those of PCBs and 1,1-dichlor-2,2-bis(p-chlorophenyl)-ethene (DDE) in mothers' milk, but a dramatic increase in PBDE concentration in milk has been reported from Sweden, corresponding to a redoubling every 5 years (Meironyté et al., 1999). During the same observation period the PCB and DDE levels have declined (Norén and Meironyté, 2000). Still, the levels of PBDEs are much lower than for PCBs and DDE. Food, particularly fish, is an important source of human exposure to PBDEs, especially of the lower brominated congeners (Sjödin et al., 1999). In some occupational settings workers may be exposed to particle bound PBDEs via inhalation (Sjödin et al., 1999, 2001). We have recently reported that workers at an electronics dismantling plant had elevated serum levels of several PBDE congeners used in technical PBDE mixtures (Sjödin et al., 1999). We also observed that clerks working full time at computer screens had marginally elevated PBDE levels, compared to a reference group of hospital cleaners. It was of particular interest to see that deca-BDE (BDE209) was present in almost all blood samples, however with significantly higher concentrations in the group of electronics dismantlers than in the reference group (Sjödin et al., 1999). Thus BDE-209, with a molecular mass of 959 Dalton, is bioavailable, in contrast to previous assumptions (IPCS, 1994).
The acute toxicity of PBDEs seems to be low (IPCS, 1994), but recent data indicate that they may be more harmful than previously considered. Some PBDE congeners have dioxin-like effects, interfering with the aryl hydrocarbon (Ah)-receptor (Meerts et al., 1998). BDE-99 has been shown to induce learning disabilities in mice (Eriksson et al., 1998). Other PBDE congeners have hepatotoxic and mutagen effects (IPCS, 1994). Still others may act as estrogen receptor agonists in vitro (Meerts et al., 2001). Hydroxylated metabolites of PBDEs have been shown to compete for binding sites on transthyretin in vivo (Meerts et al., 2000). There has, to our knowledge, been no report of toxic effects to humans attributed to these compounds (IPCS, 1994).
TBBPA has been reported as a contaminant in sediments and mussels (Watanabe et al., 1983; Sellström and Jansson, 1995). It was recently shown in serum from electronics dismantlers, having a short half-life in the exposed personnel (Hagmar et al., 2000). A clear relation between air concentrations of TBBPA at the plant and human serum levels were observed (Sjödin et al., 2001). The acute toxicity of TBBPA is low (IPCS, 1995). It has, however, been shown to be a strong competitor for thyroxine binding to transthyretin (Meerts et al., 2000).
The aim of the present study was to further investigate PBDE and TBBPA exposures in relation to computer work, focusing on more intense exposure situations than ordinary clerical work. A group of specialised computer technicians were thus investigated. The study protocol was approved by the Ethic's Committee of Lund University.
2. Materials and methods
2.1. Subjects
Computer technicians from an information technology unit at a hospital, working full time with client software and hardware support, were investigated. Yearly, system installation and testing of around 700 new personal computers were performed at the department, and some hundreds of computers were repaired or partially dismantled. Usually, between 2 and 10 (median four) computers were switched on in each office room at the department. Also, some of the technicians spent part of their work-day in a room with 30 servers.
Nineteen of the 21 technicians at the department volunteered to participate. Blood was drawn from the cubital vein into evacuated plain tubes (Vacutainer, Rutherford NJ). The serum was centrifuged, transferred to acetone-washed glass bottles, frozen and kept at -20 °C until chemical analysis. The blood sampling took place in 1999.
Present and previous work and leisure activities as well as dietary and smoking habits were assessed using a questionnaire, supplemented with an interview at the time of the blood sampling. A crude index of cumulated life-time computer use at work was calculated, based on the estimated number of hours with computers per work day multiplied with the number of years with such work ("computer-time").
For comparisons, we used already published data from 20 clerks working full-time in front of computer screens, and from 20 hospital cleaners with virtually no computer experience (Sjödin et al., 1999). The blood samplings in these groups took place in 1997. The same investigation protocol was used for the comparison groups and the computer technicians. The computer technicians were somewhat younger than the clerks and cleaners (Table 1). All cleaners and clerks were female, whereas there was a male preponderance among the computer technicians. The body burden of persistent organohalogen compounds is presumably reduced through breast-feeding (Grimvall et al., 1997). Hence, we also compared the computer technicians to the I1 cleaners and clerks, who had never been breast-feeding.
Table 1. Characteristics for computer technicians
Comparison groups . Computer Hospital Computer Never breast-feeding technicians cleaners clerks cleaners and clerks Men 15 0 0 0 Women 4 20 20 11 Ages 35(27-45) 48(30-60) 54(25-61) 40(25-61) Fish meals per montha 2(0-10) 4(0-8) 4(0-10) 4(0-8) Fatty fish from 0(0-2) 0(0-3) 0(0-0) 0(0-3) the Baltic Seaa Data for the comparison groups, as presented by Sjödin et al. (1999), are also given. a Median (range).
2.2. Chemicals
The following authentic reference substances were used in the analysis (abbreviation and origin are given): 2,2',4,4'-tetrabromodiphenyl ether (BDE-47; Orn et al., 1996), 2,2',4,4',5-pentabromodiphenyl ether (BDE-99; Orn et al., 1996), 2,2',4,4',6-pentabromodiphenyl ether (BDE-100; Marsh et al., 1999), 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE-153; Orn et al., 1996), 2,2',3,4,4',5'6-heptabromodiphenyl ether (BDE-183; Marsh et al., 1999), 2,2',3,4,4',5,5',6-octa-bromodiphenyl ether (BDE-203; Marsh, G., unpublished), 2,2',3,3',4,4',5,5',6,6'-decabromodiphenyl ether (BDE-209; Fluka Chemie, Switzerland), TBBPA (Aldrich Chemicals, Germany) and 2,2',4, 4',5,5'-hexachlorobiphenyl (CB-153; Sundström, 1973). The internal surrogate standards (IS) used were 2,3,3',4, 4',5,5'-heptachlorobiphenyl (CB-189; Sundström, 1973) for quantitation of CB-153; 2,2',3,4,4',5'- hexabromodiphenyl ether (BDE-138; Orn et al., 1994) for quantitation of PBDEs and 3,3',5'-tribromo-5-chlorobisphenol A (TrBCBPA; Hagmar et al., 2000) for quantification of TBBPA. The commercial octa-BDE products Bromkal 79-8DE (Chemische Fabrik Kalk, Köln, Germany) and Great Lakes DE79 (Great Lakes Chemical Corporation, West Lafayette, IL, USA), were employed as qualitative standards for identification of structurally unknown octa- and nona-BDEs.
Solvents and other chemicals used in the analysis of serum samples were n-hexane (distol grade; Fisher Scientific, Leicestershire, UK), methyl tert-butyl ether (MTBE) (HPLC grade; Rathburn, Walkerburn, Scotland, UK),
2-propanol (p.a. grade; Prolabo, Cedex, France), silica gel (63-200 µm), sulfuric acid and hydrochloric acid (p. a. grade; Merck, Darmstadt, Germany) and potassium hydroxide (p.a. grade; Eka Nobel, Bohus, Sweden). 2-Propanol and MTBE were glass-distilled prior to use.
2.3. Instruments
Gas chromatography with electron capture detection (GC/ECD) was performed on a Varian 3400 GC. A DB5 capillary column (30 m x 0.25 mm i.d., 0.25 gm film thickness; J & W Scientific, Folsom, CA, USA) was employed for the chromatographic separations. Hydrogen and nitrogen was employed as carrier and make-up gas, respectively. Split-less injections were used and the split was opened 2 min after injection. The column oven temperature was programmed as follows: 80 °C (2 min), 10 °C/min up to 300 °C (6 min). The injector and detector temperatures were 250 and 360 °C, respectively.
A Finnigan TSQ 700 instrument (TermoQuest, Bremen, Germany) connected to a Varian 3400 GC was employed for the GC/mass spectrometry (GC/MS) analyses. The MS was operated in the electron capture negative ionisation (ECNI) mode, using methane (AGA, Stockholm, Sweden) of >_ 99.995% purity with < 5 ppm 02 as the electron thermalization buffer gas at a pressure of 6.5 Torr. Selected ion monitoring (SIM) was performed on both bromine isotopes, m/z 79 and 81 (Blum et al., 1978). Splitless injection was employed for quantification of PBDE congeners with five or less bromine substituents and for TBBPA, using the same GC capillary column and oven temperature program as for the GC/ECD, for the chromatographic separations. Helium was used as carrier gas (head pressure 10 psi). On-column injections were performed for analysis of PBDE congeners with six or more bromine substituents, employing a septum-equipped programmable injector fitted with a high performance insert. A DB-5HT capillary column (15 m x 0.25 mm i.d., 0.10 µm film thickness; J & W Scientific, Folsom, CA, USA) was used for the chromatographic separations, with helium as the carrier gas (head pressure 3 psi). The oven temperature was programmed as follows: 80 °C (1 min), 15 °C /min up to 300 °C (13 min). The injector temperature was programmed from 60 °C with a temperature increase of 180 °C/min up to 300 °C and kept there for the duration of the GC run.
2.4. Sample clean-up and analysis
The serum samples were divided into two equally sized groups prior to sample preparation. Within each of these groups four blank samples were included to detect any interferences. The methods used for extraction and gravimetric lipid weight determination have been described in detail elsewhere (Hovander et al., 2000) and are only briefly indicated here. Internal surrogate standards (IS) were added to the serum samples (5 g) in a sample tube. Hydrochloric acid and isopropanol were added to the sample with rigorous blending between the additions. The samples were subsequently extracted with a mixture of hexane/MTBE (1:1), twice. The combined organic phases were washed with a potassium chloride water solution, followed by evaporation to dryness for gravimetric determination of the amount of extracted lipids. The amount of serum lipids was used to express concentration data on a lipid weight (l.w.) basis. The extracted serum samples were partitioned with a potassium hydroxide solution in 50% ethanol to obtain a neutral fraction (containing PBDEs and PCBs), and a phenolic fraction (containing TBBPA). Halogenated phenols were recovered by acidification and subsequent extraction by hexane/MTBE (1:1). For clean-up of the neutral fraction a pre-washed (hexane; 8 ml) silica/sulfuric acid column (silica/sulfuric acid 2:1 by weight; 1 g) was employed. The analytes were eluted from this column employing hexane (8 ml) as the mobile phase. The phenolic fraction was first treated with diazomethane to obtain the TBBPA dimethyl ether derivative, followed by clean-up in a silica/sulfuric acid column (0.5 g), two fractions were collected from this latter column, i.e., hexane/DCM (1:1; 5 ml) and DCM (15 ml). The second fraction collected contains TBBPA.
2.5. Identification and quantification
The analytes were identified by comparison of their relative retention times (RRTs) to that of authentic reference compounds and by spiking of one sample to approximately twice the original concentration. The spiked samples were then analysed by GC/MS(ECNI) and the chromatographic peaks were examined for any deformities that would indicate an inaccurate identification. These methods were used since the GC/ MS(ECNI) system is sensitive for brominated aromatics but does not give any structural information since only the prevalent bromine ions may be monitored at analysis of low concentration samples.
Quantification of the PBDEs and TBBPA, using the GC/MS(ECNI) instrument, was made in relation to authentic reference standards, except for structurally unidentified octa- and nona-BDEs (see below), prepared at multiple concentration levels. CB-153 was quantified by comparison to the authentic reference standard, employing single point calibration, on the GC(ECD) instrument used (see instruments for further details). The presence of structurally unidentified octa- and nona-BDEs were shown in the serum samples by comparison to standards of technical octa-BDE products. In order to estimate their concentration the response factor for the only octa-BDE available (i.e. BDE-203) was employed.
The concentration data reported have been corrected for blank interferences. The limit of detection (LOD) was set to a signal to noise ratio (S/N) of three while limit of quantification (LOQ) on a S/N basis was set to 10. In case of blank interference the LOQ was set to five times the blank level. Concentration data on BDE-209 and TBBPA is only available from half of the samples analysed (cf. Tables 2 and 3). This since the interference level was higher in some of the blank samples analysed giving a higher LOQ for these samples. There were no differences between the subjects for which concentration data on BDE-209 and TBBPA were obtained and the remaining subjects with respect to age, sex, dietary habits, cumulated computer work time, or the number of personal computers in the room where the subjects spent most of the work day. Thus, the samples analysed for BDE-209 (n = 9) and TBBPA (n = 10) are considered to be representative for the total study group.
2.6. Statistics
For testing of group differences, the Mann-Whitney U-test was used. Associations were assessed with the Spearman rank order correlation test (r5). Statistical significance was defined as a p-value less than 0.05.
3. Results
PBDEs were found in all analysed samples. The concentrations, and patterns of BDE- 153, -154, -183 and -209 differed between the study groups (Table 2). The findings were similar, except for BDE-154, when the computer technicians were compared to women in the referent groups who never had been breast-feeding. The computer technicians had serum concentrations of BDE-153, BDE-183 and BDE-209 that were around five times higher than those previously reported among hospital cleaners and computer clerks.
In contrast, for BDE-47 there was no difference between the computer technicians and the other study groups. BDE-100, BDE-203 and the other three octaBDEs, and two nona-BDEs were present in almost all samples (Table 3).
Table 2. Serum concentrations (pmol/g lipid weight) of five PBDE-congeners and CB-153 in computer technicians
Comparison groups . Never breast-feeding Hospital cleaners Computer clerks cleaners and clerks Computer technicians (n=19) (n=20) (n=20) (n=11) . Median Range p-valuea p-valueb Median Range Median Range Median Range BDE-47 2.7 <2c-28 >0.5 >0.5 3.2 <lc-34 3.0 <1c-10 4.3 1.3-34 BDE-153 4.1 <2e-9.0 <0.001 0.003 0.89 0.54-7.6 1.3 0.80-5.1 1.2 0.90-7.6 BDE-154 0.93 0.35-1.9 0.001 >0.5 0.59 0.25-1.4 0.79 0.43-1.5 1.80 0.60-1.4 BDE-183 1.3 0.24-6.4 <0.001 <0.001 0.16 0.025-0.39 0.24 <0.02e-1.4 0.22 0.12-0.40 BDE-209 1.6d <e-7.1 0.003 0.026 <0.7e <0.3f-3.9 <0.7e <0.3f-8.0 <0.7 <O.3f-3.9 CB-153 290 110-820 >0.5 >0.5 330 120-1000 480 130-1300 450 120-1000 Data for the comparison groups, as presented by Sjödin et al. (1999), are also given. a Mann-Whitney U-test; hospital cleaners as comparison group. b Mann-Whitney U-test; never breast-feeding hospital cleaners and computer clerks as comparison group. c Limit of quantification is defined as five times the level in the blank sample. d Nine subjects only. e Limit of quantification is defined as a signal to noise ratio of 10. f Limit of detection is defined as a signal to noise ratio of 3.
Table 3. Serum concentrations of BDE-100, some octa-, and nona-BDEs and TBBPA in computer technicians (n = 19)
Median Quantified (pmol/g Compounds <LODa n <LOQb n n lipid weight) Range . BDE-100 0e,d 3e 16 0.91 <0.le-3.6 octa-BDE:1 3e 12f 4 <0.1f <0.03e-0.23 octa-BDE:2 Oe Of 19 1.0 0.28-5.7 BDE-203 0f 9f 10 0.10 <O.lf-1.1 octa-BDE:4 0c 10f 9 <0.1f <O.lf-0.70 nona-BDE:1 5c 13f 1 <0.1f <O.06e-0.15 nona-BDE:2 Oc 4f 15 0.40 <0.2f-1.4 nona-BDE:3 le 14f 4 <0.2f <0.04e-0.40 TBBPAg 2d 4e 4 <1e <ld-3.4 a Limit of detection (LOD). b Limit of quantification (LOQ). c Limit of detection is defined as a signal-to-noise ratio of 3. d Limit of detection is defined as a three times the level in the blank sample. e Limit of quantification is defined as five times the level in the blank sample. f Limit of quantification is defined as a signal to noise ratio of 10. g Ten subjects only.
TBBPA was detected in 8 out of 10 samples from the computer technicians, but quantified only in four (Table 3). It should be noted that the levels of CB-153 were approximately two orders of magnitude higher than those of the PBDEs in all occupational groups (Table 2).
No correlations between age and the different BDEs were observed in any of the occupational groups.
Among the computer technicians we observed positive correlations between fish consumption and BDE-47 (rs = 0.46, p = 0.05), BDE-100 (rs = 0.42, p = 0.08), BDE-153 (rs = 0.58, p = 0.008), BDE-183 (r, = 0.49, p = 0.03), and octa-BDE:2 (rs = 0.49, p = 0.04), but not for CB-153. The findings were similar, but not reaching statistical significance, when only consumption of fatty fish from the Baltic Sea was considered.
"Computer-time" was correlated with BDE-153 (rs = 0.52; p = 0.02), BDE-183 (r, = 0.53, p = 0.02; Fig. 1), and octa-BDE:2 (r, = 0.62, p = 0.005), but not with BDE-154. There was no significant correlation between fish consumption and "computer time".
Fig. 1. Serum concentrations of BDE-183 (pmol/g lipid weight) in relation to estimated duration of work with computers ("computer-time", h) in 19 computer technicians.
4. Discussion
Computer work was associated with elevated serum levels of BDE-153, BDE-183 and BDE-209. The levels observed were in accordance with our presumption of an exposure gradient between cleaners, clerks and computer technicians. The computer technicians, who were mostly men, were compared with women. The differences in serum levels between the study groups were, however, not explained by a reduced body burden of PBDEs due to breast-feeding.
The estimated half-life of BDE-183 is relatively long, 86 (95% CI 43-128) days (Hagmar et al., 2000). The blood samples from the computer technicians and clerks were taken 6 and 11 months, respectively, after the summer vacation; thus we can assume that the workers had reached a steady state. The estimated half-life for BDE-209 seems to be shorter, 6.8 (95% CI 3-16) days, but not so short that random sampling in relation to time of exposure should be a great concern. Further, all blood samples were drawn on the same day within the groups of computer technicians and computer clerks, respectively.
Among computer technicians there was a clear correlation between BDE-153, BDE-183, and octa-BDE:2 and the duration of computer-work. For BDE-209 there were too few quantified samples to make such a correlation analysis meaningful. Thus, it is reasonable to assume that intense work with computers leads to PBDE exposure. A possible source is contaminated airborne dust particles. In air samples from a computer hall and from office rooms with computers, PBDEs, strongly bound to particulate matter have been detected (Sjödin et al., 2000). However, the PBDE-levels observed among computer technicians and clerks were considerably lower than those previously observed among workers from an electronics dismantling plant (Sjödin et al., 1999). In contrast, the TBBPA levels were comparable between the computer technicians and a selected group of workers dismantling electronics, a finding that is in accordance with the short half-life of TBBPA (approximately 2 days) limiting any bioaccumulation (Hagmar et al., 2000).
In contrast to the findings for the higher brominated PBDEs, the levels of BDE-47 showed less variation between the study groups. Among computer users, the levels were similar to those found among Swedish blood donors (Klasson-Wehler et al., 1997) and slightly lower than the levels in mother's milk (Meironyté et al., 1999). Similarly, CB-153 levels observed were in accordance with previous observations from the general Swedish population (Sjödin et al., 1999, 2000; Norén and Meironyté, 2000). Contaminated food, particularly fish, is the main exposure route for both the lower brominated PBDEs and CB-153 (Sjödin et al., 1999; de Boer et al., 2000; de Wit, 2000). Among men with high intake of fatty fish from the Baltic Sea, there was a strong correlation between fish intake and BDE-47 (Sjödin et al., 2000). A positive correlation between fish consumption and BDE-47 in serum among computer technicians was observed. Moreover, such correlations were also seen for some higher brominated PBDE congeners. However, correlations between fish consumption and BDEs were not observed among cleaners and clerks. Thus, the observations among computer technicians could well be chance findings. The lack of association between their stated fish consumption and CB-153 supports this assumption. It should also be kept in mind that the fish consumption, especially of fatty fish from the Baltic Sea, was rather low in our study groups.
The PBDE levels were far lower than the PCB levels in all occupational groups studied. As there is no reason to suspect that PBDEs are more toxic than PCBs (Ahlborg et al., 1992; IPCS, 1994), there is at present no reason to believe that computer work conveys a health risk from PBDE exposure. However, our results clearly show that PBDEs used in computers and electronics contaminate the work environment and accumulate in workers. This is true also for the decabrominated diphenyl ether. There has been a shift towards using BDE-209 instead of lower brominated diphenyl ethers, as it has been assumed that BDE-209 has a low bioavailability (IPCS, 1994). This shift may be reflected in our finding that among the computer technicians, handling brand new or relatively new computers, the BDE209/BDE-183 ratio in serum, 1.2:1, was higher than among workers dismantling older computers and other older electronic equipment, 0.5:1 (Sjödin et al., 1999). Similarly, it was observed that the BDE-209/BDE-183 ratio in air was higher in office rooms with computers than in the air at the dismantling plant (Sjödin et al., 2000).
We have now demonstrated that computer work in quite common occupational settings leads to human exposure to PBDEs including deca-PBDE, which indeed is bioavailable. There is yet no indication that this exposure entails any health risks, but our findings support actions to both control and limit entry of the persistent and bioaccumulating PBDEs into the environment.
Acknowledgements
Invaluable assistance was provided by Länshälsan i Blekinge 1än AB, Karlskrona. We are grateful to RN Kerstin Kronholm-Diab, RN Marie Nordin, and RN Gudrun Karlsson for valuable assistance with the in terviews and the blood sampling, and Ioannis Athanasiadis for the mass spectrometry analyses. Financial support was provided by the Swedish Work Life Council and the Faculty of Medicine, Lund University.
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