Indoor Air Is a Significant Source of Tri-decabrominated Diphenyl

Article pubs.acs.org/est

Indoor Air Is a Significant Source of Tri-decabrominated Diphenyl Ethers to Outdoor Air via Ventilation Systems Justina Awasum Björklund,† Kaj Thuresson,‡ Anna Palm Cousins,§ Ulla Sellström,† Gunnel Emenius,∥ and Cynthia A. de Wit†,* †

Department of Applied Environmental Science (ITM), Stockholm University, SE-106 91 Stockholm, Sweden Swedish National Heritage Board, Box 1114, 621 22 Visby, Sweden § IVL Swedish Environmental Research Institute, Box 21060, SE-10031 Stockholm, Sweden ∥ Public Health Sciences, Occupational and Environmental Medicine, Karolinska Institutet, Norrbacka, fourth level, SE-17176 Stockholm, Sweden ‡

S Supporting Information *

ABSTRACT: Ventilation of indoor air has been hypothesized to be a source of PBDEs to outdoors. To study this, tri-decabrominated diphenyl ethers were analyzed in outgoing air samples collected inside ventilation systems just before exiting 33 buildings and compared to indoor air samples from microenvironments in each building collected simultaneously. Median ∑10PBDE (BDE- 28, -47, -99, -153, -183, -197, -206, -207, -208, -209) concentrations in air from apartment, office and day care center buildings were 93, 3700, and 660 pg/m3 for outgoing air, and 92, 4700, and 1200 pg/m3 for indoor air, respectively. BDE-209 was the major congener found. No statistically significant differences were seen for individual PBDE concentrations in matched indoor and outgoing air samples, indicating that outgoing air PBDE concentrations are equivalent to indoor air concentrations. PBDE concentrations in indoor and outgoing air were higher than published outdoor air values suggesting ventilation as a conduit of PBDEs, including BDE-209, from indoors to outdoors. BDE-209 and sum of BDE-28, -47, -99, and -153 emissions from indoor air to outdoors were roughly estimated to represent close to 90% of total emissions to outdoor air for Sweden, indicating that contaminated indoor air is an important source of PBDE contamination to outdoor air.

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INTRODUCTION Polybrominated diphenyl ethers (PBDEs) are additive flame retardants that are or have been used to flame retard electronic and electrical equipment, textiles, and furniture foams. PBDEs were sold as three commercial mixtures with different degrees of bromination (i.e., pentabromodiphenyl ether (pentaBDE), octabromodiphenyl ether (octaBDE), and decabromodiphenyl ether (decaBDE)).1 Because these chemicals are additives to products, they can be released from these over the lifetime of the products and enter the environment. In humans, associations have been seen between plasma concentrations of PBDE congeners found in the pentaBDE mixture and effects on neurobehavior, reproduction and thyroid hormone homeostasis.2−8 Due to their toxicity, the penta- and octaBDE technical products were banned in the EU in 20049 and globally in 2009.10 In 2008, decaBDE was banned for use in electronic and electrical equipment in the EU (European Court of Justice, 2008), and recently major producers in the U.S. have announced they will discontinue decaBDE production and use by 2013.11 Despite the bans, older flame-retarded consumer products in different indoor microenvironments still act as sources of PBDEs to the indoor environment.12 Higher concentrations of PBDEs (10−50 times), including BDE-209, have been © 2012 American Chemical Society

measured in indoor than outdoor air due to the presence of flame-retarded products.13,14 PBDE concentration gradients are seen in outdoor air from urban to rural sites, suggesting that cities are a likely source of PBDEs to rural and remote areas.15,16 These observations have led to the hypothesis that releases of contaminated air from indoor environments, for example via ventilation systems, may be an important emission source of PBDEs to the outdoor environment. This hypothesis has some support from several studies modeling or estimating emissions of primarily PBDE congeners in the pentaBDE technical product from indoors to outdoors.17−19 However, aside from these studies, little has been done to actually measure the transfer of PBDEs from indoor air to the outdoor environment to confirm the models. This study was designed to test the following two hypotheses: (1) gaseous and particle-bound PBDEs, including BDE-209, are emitted from indoors to the outdoors via ventilation systems; (2) these emissions are a significant source of these contaminants to outdoor air. This was done by Received: Revised: Accepted: Published: 5876

November 18, 2011 March 9, 2012 May 1, 2012 May 1, 2012 dx.doi.org/10.1021/es204122v | Environ. Sci. Technol. 2012, 46, 5876−5884

Environmental Science & Technology

Article

min per sampler). The sampler was suspended at least 1 m above the floor with the filter end pointing down. Both humidity and temperature were recorded continuously in each microenvironment during sampling. Indoor temperatures ranged from 16 to 25 °C and relative humidity ranged from 10 to 56%. To sample outgoing air just before leaving the building, air samples (gas and particle phase) were collected from the ventilation system in the 19 apartment buildings, five day care centers and nine office buildings. The sampling train with the pump was positioned in the ventilation duct, after the ventilation fans and filters (if any) but just before the final exit point to the outdoors. The sampler pump was started, the ventilation system was resealed and the ventilation fan restarted if it had been shut off during sampling set up. In addition, indoor air samples from the living room of four apartments from each apartment building, one room in each day care center and one office in each office building were collected simultaneously.29 The indoor air samples from offices, day care centers and 11 of the apartment buildings represent a subset of samples studied previously,29 with the addition of four apartments from each of eight more apartment buildings for the current study. Indoor and ventilation air were sampled for 8 (offices, day care centers) or 24 h (apartments) during the heating season in 2006 (March-April and October 2006February 2007). In our previous study,29 we reported some breakthrough of the higher brominated BDEs, particularly BDE-209, from the filter to the first PUF, when these were analyzed separately. Therefore, for the present study, the GFFs and PUFs from the four sampling trains of each sample were combined, extracted and analyzed as one sample, giving total (gas plus particle phase) concentrations. Chemical Analysis. The chemicals and standards (reference and surrogate) used, as well as the extraction and cleanup methods have previously been described29 and details are given in the SI. In brief, air samples (GFFs and PUFs) were spiked with surrogate standards (Dechlorane 603 and 13C-BDE-209) before the extraction with 2 × 18 mL dichloromethane (DCM) in an ultrasonic bath. Before sample cleanup on a small sulfuric acid/silica gel mix column, the DCM volume was reduced and solvent changed to n-hexane. The clean sample extract volume was further reduced and transferred to autosampler vials that were prespiked with the recovery standard (BDE-77). Before the instrumental analysis, volumes were reduced to 50 μL. Samples were analyzed for tri-decaBDEs (BDE-28, -47, -99, -153, -183, -197, -206, -207, -208, and -209) using gas chromatography−mass spectrometry (GC-MS) in electron capture ionization mode with ammonia (99.99%, AGA Stockholm, Sweden) as moderating gas. The ions monitored were the bromide ions (m/z −78.9 and −80.9) for trioctaBDEs, the phenoxide ions for nona-decaBDEs (m/z −484.2 and −486.2 for the native, and −494.3 and −496.3 for 13C-BDE-209), and m/z −236.7 and −238.7 for Dechlorane 603. The system used was a Finnigan MAT SSQ 7000 MS instrument coupled to a Hewlett-Packard 5890 II GC. The GC was equipped with a 15 m DB-5MS fused silica column (0.25 mm i.d., film thickness 0.25 μm, J&W Scientific, Folsom, CA). Helium (99.99%, Air Liquide, Stockholm, Sweden) was used as carrier gas (constant flow) and the injections were made in splitless mode, with the injector at 270 °C. The oven temperature program started at 80 °C (held for 2 min, with the split valve closed for 1.5 min), then increased by 20 °C/min to 200 °C followed by 6 °C/min to 315 °C (held for 5 min). MS conditions were electron energy 70 eV; ion source

sampling and quantifying PBDEs, including BDE-209, in outgoing air from apartment buildings, day care centers and office buildings in Stockholm, Sweden. The concentrations in the outgoing air were compared to those from matched air samples taken simultaneously from at least one room inside each building. Results for the sum of BDE-28, -47, -99, and -153 concentrations (hereafter designated ∑pentaBDE), and BDE209 concentrations in outgoing air from buildings were then used to estimate their emissions to the outdoor environment. These estimated emissions were compared to total estimated emissions to Swedish outdoor air from all sources estimated using substance flow analysis (SFA) methodology.20

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MATERIALS AND METHODS Building Selection. One typical office, containing office furniture and electronic equipment (e.g., computer, monitor, printer), from each of nine different buildings from Stockholm was sampled. The offices were comprised of a convenience sample identified via contacts of the research group and represented private companies, university buildings, as well as local and national government buildings. A representative set of Stockholm day care centers in terms of age and construction type was selected by city officials and sampling was carried out in the playroom area, which contained cushions, toys, rugs, and various pieces of furniture. Apartments from multistory buildings were from a larger field study (Healthy Sustainable Houses-3H) with the aim to identify buildings with increased frequencies of Sick Building Syndrome carried out in Stockholm. A total of 47 out of 481 representative buildings were selected for in depth study with inspections and measurements in buildings.21,22 Of these, 19 buildings were included in the current study. Four apartments in each building were selected randomly for air sampling and these contained household goods, electronic equipment, and furniture typical of Swedish households. Indoor air sampling was carried out in the living room. Air change rates in the apartments were measured using tracer gas methodology.23−25 Ventilation flows were not measured in offices or day care centers. Occupants were asked to fill in a detailed questionnaire regarding sampling location characteristics, including furnishing and equipment present and a separate sampling protocol was filled in by the research team. Some information was obtained from the building owners. Relationships between building characteristics, microenvironment contents and air concentrations of PBDEs for many of these buildings have been published previously.26 Office buildings had exhaust air ventilation systems, day care centers had exhaust and supply air ventilation with heat recovery and of the apartment buildings, 15 had exhaust air ventilation, three had exhaust and supply ventilation and one had boosted natural ventilation. Air Sampling. More details of the sampling are given in the Supporting Information (SI) but are described briefly here. Air sampling of PBDEs was performed using low volume active air samplers connected to a personal pump (Leland Legacy, SKC Inc., Eighty Four, PA) with a flow rate of 1−15 L/min27,28 as described previously.29 Each sampler train contained two polyurethane foam plugs (PUFs) (diameter 15 mm, thickness 15 mm, Specialplast AB, Gillinge, Sweden) for collecting target compounds in the vapor phase and a glass fiber filter (GFF, binder-free A/E borosilicate, 25 mm i.d., 99.98% collection efficiency at 0.3 μm, Pall Corp., MI) for collecting target compounds on particles.30 Four sampling trains were placed in parallel on one pump with a total flow rate of 12 L/min (3 L/ 5877

dx.doi.org/10.1021/es204122v | Environ. Sci. Technol. 2012, 46, 5876−5884


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Table 1. Median (Range) Concentrations of Individual PBDE Congeners in Indoor Air (pg/m3) from Stockholm Microenvironments apartments BDE-28 BDE-47 BDE-99 BDE-153 BDE-183 BDE-197 BDE-206 BDE-207 BDE-208 BDE-209 ∑pentaBDE ∑decaBDE ∑10PBDE a

offices

day care centers

(n = 19)

% detects

(n = 9)

% detects

(n = 5)

% detects

4.5 (0.086−110) 17 (4.1−1100) 5.2 (0.78−220) 0.88 (0.17−3.9) 1.2 (0.0014a −23) 0.21 (0.057a −11) 8.0 (4.1a −37) 2.7 (0.071−38) 1.0 (0.14a −20) 27 (0.70−220) 39 (8.3−1400) 42 (9.5−300) 92 (18−1400)

100 100 100 100 95 74 74 95 89 100

1.3 (0.042a-14) 240 (23−370) 320 (4.4−560) 32 (0.042a −51) 210 (0.014a −420) 100 (0.057a −180) 640 (5.7a −890) 450 (9.1−760) 270 (0.14a −530) 2400 (57−3600) 600 (29−1000) 3800 (73−5800) 4700 (140−7300)

56 100 100 67 78 78 78 100 89 100

0.042 (0.042a −10) 34 (4.2−200) 19 (3.1−33) 1.4 (0.042a −3.2) 0.31 (0.014a −27) 21 (0.057a −25) 19 (5.7−71) 29 (0.14a −130) 20 (0.14a −91) 820 (62−1400) 54 (7−240) 1100 (68−1400) 1200 (76−1500)

20 100 100 80 60 80 60 100 80 100

Denotes LOQ/√2.

Table 2. Median (Range) Concentrations of Individual PBDE Congeners in Outgoing Air (pg/m3) from Stockholm Microenvironments apartments (n = 19) BDE-28 BDE-47 BDE-99 BDE-153 BDE-183 BDE-197 BDE-206 BDE-207 BDE-208 BDE-209 ∑pentaBDE ∑decaBDE ∑10PBDE a

2.8 (0.20−10) 22 (6.0−130) 9.9 (0.71a −120) 0.85 (0.042a −6.8) 1.7 (0.0014a −6.5) 0.57 (0.057a −3.9) 5.7 (5.2a −12) 3.2 (0.071a −10) 1.1 (0.14a −6.0) 22 (0.49a −220) 43 (10−260) 30 (6.4−240) 93 (17−280)

offices % detects 100 100 95 95 89 63 37 74 63 84

(n = 9) a

7.3 (0.042 -19) 350 (41−910) 250 (52−590) 23 (4.9−56) 190 (20−390) 110 (11−210) 520 (34−1200) 450 (94−1100) 240 (46−610) 1900 (480−4000) 740 (98−1600) 3100 (650−6800) 3700 (780−8500)

day care centers % detects

(n = 5)

% detects

89 100 100 100 100 100 100 100 100 100

1.9 (0.042−6.6) 47 (37−250) 48 (42−250) 4.2 (2.9−4.9) 20 (19−27) 12 (10−19) 64 (46−78) 66 (40−68) 29 (17−38) 340 (220−400) 120 (84−300) 510 (320−570) 660 (450−8500)

80 100 100 100 100 100 100 100 100 100

Denotes LOQ/√2.

temperature 180 °C; moderating gas pressure 7000−8000 mTorr. Since there was no available authentic reference standard for BDE-208, the response factor for BDE-207 was applied with the assumption that the difference in responses was small. QA/QC. The QA/QC procedures applied have previously been described29 and details are given in the SI. These included general precautions to minimize contamination of samples, degradation of analytes, analysis of laboratory blanks, field blanks and QC samples, method validation such as establishment of analyte recoveries and limits of detection and quantification. Statistical Analyses. The goodness of fit and distribution of data for PBDEs in air samples from each microenvironment were tested using quartile − quartile plots and Shapiro-Wilk test. The data for all PBDE congeners in air were skewed, but natural logarithm (ln) transformation gave normal distributions that fulfilled criteria for parametric testing. All statistical tests were thus performed on ln-transformed data using the PASW statistical package (Version 18, SPSS Inc.). The statistical significance was set at α = 0.05 level. Values below the limit of quantitation (LOQ) were assigned the value of LOQ/√2. The sums of the PBDEs associated with each technical product

(pentaBDE: BDE-28, -47, -99, and -153; octaBDE: BDE-183 and -197; decaBDE: BDE-206, - 207, -208, and -209)31 were also ln-normally distributed. Paired comparisons t tests and Pearson correlation analyses were performed for individual PBDE congeners in matched indoor and outgoing air samples from each microenvironment. Emissions were calculated using the 10th and 90th percentiles for PBDE concentrations to reduce the influence of outliers.

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RESULTS AND DISCUSSION PBDE Concentrations in Indoor and Outgoing Air. TridecaBDEs were detected in all indoor and outgoing air samples from the three microenvironment types studied. The ∑10PBDE (the sum of BDE- 28, -47, -99, -153, -183, -197, -206, -207, -208, -209) concentrations in indoor air samples ranged from 18 pg/m3 for apartments to 7300 pg/m3 in offices (Table 1). For outgoing air, the concentrations of ∑10PBDEs ranged from 17 pg/m3 in apartments to 8500 pg/m3 in offices (Table 2). Offices had the highest median concentrations of ∑10PBDE for both indoor (4700 pg/m3) (Table 1) and outgoing air samples (3700 pg/m3) (Table 2), whereas apartments had the lowest median ∑10PBDE concentrations in both sample types. The 5878



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Figure 1. Statistically significant correlations between log-transformed concentrations (pg/m3) of individual PBDE congeners in matched samples of indoor air and outgoing air.

highest median concentrations for both ∑pentaBDE and BDE209 were also seen in offices (600 and 2400 pg/m3 respectively, in indoor air (Table 1), and 740 and 1900 pg/m3 respectively, in outgoing air (Table 2)). This was 1−2 orders of magnitude higher than what was seen in apartments and day care centers and may be related to the multitude of potential sources (e.g., computer casings, printers, scanners, fax machines etc.) of BFRs in offices. Higher ∑pentaBDE concentrations in offices compared to homes have also been seen in other studies.17,32,33 There were variations in PBDE concentrations and congener profiles in indoor air from the apartments both within the same building and between buildings (Figure S1, SI). This was probably mainly due to differences in the contents of flameretarded goods in the apartments and less due to building materials, but may also be due to differences in ventilation, filtration, cleaning habits, etc. Among PBDEs determined in both indoor and outgoing air in all microenvironments, BDE-209 was the most predominant congener (Tables 1 and 2). For indoor air, BDE-209 represented 41, 80, and 51% of the ∑10PBDEs for apartments, day care centers, and offices, respectively. This was followed by BDE-47 in apartments (24%), day care centers (6%) and offices (10%), and BDE-206 (10%) in offices. For outgoing air, BDE209 represented 33, 50, and 51% of the ∑10PBDEs for apartments, day care centers, and offices, respectively. This was followed by BDE-47 (31%) and BDE-99 (14%) for apartments, BDE-47 (12%) and BDE-206 (10%) for day care centers, and

BDE-207 (12%) and BDE-206 (11%) for offices. The predominance of BDE-209 in indoor and outgoing air is probably due to the fact that the decaBDE mixture has been used in larger quantities than the penta- and octaBDE mixtures and it is the predominant PBDE technical product still in use. The predominance of BDE-209 has also been seen in other studies of indoor air as reviewed in Frederiksen et al.34 and Harrad et al.13 The prevalence of nonaBDEs could be due to degradation of BDE-20935 or historical decaBDE usage, since older decaBDE mixtures had only 70% purity,36 indicating possible influence by releases from older flame-retarded items indoors. The concentrations of ∑pentaBDE in the indoor samples from Stockholm offices, day care centers, and apartments were similar to those found in similar building types in other European studies33,37−39 but were lower than seen in Denmark and North America.19,40−43 The geographic differences seen may be reflective of the different use patterns of the pentaBDE technical product where 95% of pentaBDE was used in North America. Less data are available for comparisons of BDE-209 concentrations in air. Concentrations of BDE-209 in Stockholm apartments were similar to those found in households from Germany37 but lower than those seen in Denmark and North America.40,43 Comparisons between Indoor and Outgoing Air. Median indoor ∑10PBDE concentrations were similar to outgoing air for all microenvironments (Tables 1 and 2). 5879



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Table 3. Variables used in Calculations, Estimated Yearly Emissions and Estimated Emission Rates of ∑PentaBDE and BDE209 for Households and Public Buildings in Sweden estimated ventilation flows (L/s/m2) estimated annual ventilation flows (m3/y/m2) total heated surface area (m2) ∑pentaBDE concentrations (pg/m3) (10th and 90th percentiles) BDE-209 concentrations (pg/m3) (10th and 90th percentiles) ∑pentaBDE emissions (kg/y) BDE-209 emissions (kg/y) ∑pentaBDE emission rates (ng/h/m2) BDE-209 emission rates (ng/h/m2)

Paired comparisons t tests for individual PBDE congener concentrations in matched indoor and outgoing air samples for the entire data set showed no statistically significant differences. When analyzing each microenvironment individually no statistically significant differences were seen except for BDE28 (p = 0.028) in apartments and BDE-183 (p = 0.040) in day care centers. Thus, the outgoing air sample from the apartment building was representative of the indoor air samples from the four separate apartments in the same building. The outgoing air samples from office buildings and day care centers were also representative of the indoor air samples from the single rooms that were sampled. Statistically significant correlations were also seen between indoor air and outgoing air concentrations in matched samples for all PBDE congeners (except BDE-28: r = 0.240, p = 0.178) (Figure 1), confirming indoor air as a source of PBDEs to the ventilation system and to the outgoing air. This indicates that it may be possible to use indoor air concentrations as a proxy for outgoing air concentrations when estimating emissions for these microenvironments. However, further studies are needed to verify this. The median concentrations of ∑pentaBDE (43−740 pg/ m3) and BDE-209 (22−1900 pg/m3) in outgoing air from the three types of microenvironments (Table 2) are up to several orders of magnitude higher than seen in background outdoor air from Sweden (∑pentaBDE 1.6−3.7 pg/m3; BDE-209 6.1− 6.5 pg/m3)44−46 or background sites in North America and across Europe (less than 10 pg/m3 for the sum of lower brominated PBDEs, usually less than 20 pg/m3 for BDE209).16,46−52 The ∑pentaBDE concentrations in outgoing air are also higher than seen in outdoor air from urban areas of North America and Europe (3−100 pg/m3).16,53−56 For BDE209, outgoing air concentrations are also higher than seen in urban areas of Turkey (26 pg/m3).51 Taken together, these results give strong support to the hypothesis that PBDEs, including BDE-209, in indoor air enter ventilation systems, are vented virtually unchanged to the outdoors and then probably undergo dilution through atmospheric mixing. This would lead to the lower PBDE concentrations found outdoors than indoors and explain the concentration gradients seen from urban to rural areas. Thus ventilation is a likely mechanism through which PBDEs migrate from indoor sources to the outdoors. BDE-209 Transport to Outdoor Air. According to Shoeib et al.,55 80% of BDE-47 and 10−40% of the airborne pentaheptaBDEs are expected to be present in the gas phase at room temperature while BDE-209 predominantly would be present in the particulate phase. Particle-bound contaminants on larger particles would be expected to be caught in ventilation system filters42 (if present), and/or to possibly deposit or be stripped

households

public buildings

0.12−0.68 3800−21 400 4.37 × 108 15−98 7−130 0.024−0.92 0.012−1.2 0.006−0.24 0.003−0.32

0.56−1.8 17 600−56 800 1.53 × 108 95−1000 310−3600 0.26−8.7 0.83−31 0.19−6.5 0.62−23

out of the air when traveling in ventilation ducts. This could lead to enrichment of the lower brominated more volatile PBDE congeners in outgoing air. However, the most predominant congener in both indoor and outgoing air, with no significant difference in concentration, was BDE-209. This indicates that particle-bound contaminants are also transported in and released from ventilation systems. Large particles will settle as dust indoors but fine particles will be suspended in air. BDE-209 bound to very fine particles found in indoor and outgoing air may thus be transported through the ventilation systems and/or it is present in the gas phase in indoor air. There is some support for these hypotheses. Batterman et al.42 found that the higher brominated PBDE congeners, including BDE-209, were associated with the fine particle fraction captured in bag filters of an office building ventilation system. Agrell et al.44 found BDE-209 to be predominantly in the gas phase in outdoor air samples in southern Sweden and Cetin and Odabasi57 concluded that when BDE-209 is emitted from its sources in the gas-phase, it may remain in that phase for several months before reaching equilibrium with atmospheric particles. It is not clear if similar relationships exist in indoor air, but Allen et al.43 and Thuresson et al.29 both reported breakthrough of a portion of airborne BDE-209 through the GFFs to the PUFs during indoor sampling. These results may not have been breakthrough, but actual capture of BDE-209 in the gas phase on the PUFs. This may have important implications for the atmospheric transport of BDE-209, as gas phase contaminants might travel much further than particle bound contaminants. Significance of PBDE Emissions from the Indoor Environment to Outdoors. The emissions from the indoor environments to outdoor air were estimated as follows. The measured air change rates in the apartments varied from 0.17 to 1.0 h−1. From the questionnaires and sampling protocols, the surface area (m2) and volume (m3) of both the living room and the entire apartment were available. The air flow (m3/h) for each living room and apartment was calculated, converted to liters/second (L/s) and divided by the surface area of the room/apartment to obtain the ventilation outflow in L/s/m2. The range of ventilation outflows were similar for each paired living room and apartment and the range for all the apartments in this study was 0.12−0.68 L/s/m2 with a median of 0.47 (Table 3). The median was similar to the Swedish building standard of 0.35 L/s/m2, and we therefore assumed that the range of ventilation outflows were reasonably representative values.58 For offices and day care centers, the building standard is 0.35 L/s/m2 plus a minimum of 7 L/s per person in the room or building.59 Since we had no measured ventilation data for these 5880



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Table 4. Estimated Emissions of PentaBDE to Outdoor Air in Sweden (See SI for Full Description of Calculations and References) source metals manufacturing municipal incineration electronics recycling e-waste fires landfill fires indoor environment households indoor environment− public buildings total percentage total contribution of indoor air

emission factor

annual emission (kg/ year)

activity (kg/year)

comment

35−716 μg/tonne product

1.7 × 10

no information

0.8−18

no information

9 × 104−5.6 × 105

8.4−50.2 μg/kg burnt material, assuming no extinguishing water 4.96 − 394 μg/kg C burned 10−260 pg/m3

1.48 × 106

not possible to estimate not possible to estimate 0.01−0.07

7 × 104−7 × 105 1.7 × 1012−9.4 × 1012 m3/year

3.5 × 10−4−0.028 0.024−0.92

concerns sum of BDEs (47,85,99,100,138,153,154). nondetected congeners were assigned a value of 0 (d.l. = 1.5 μg/kg burnt) concerns BDE-47 only concerns BDE-28, -47, -99, -153

84−1600 pg/m3

2.7 × 1012− 8.7 × 1012 m3/year

0.26−8.7

concerns BDE-28, -47, -99, -153

9

0.06−1

concerns the sum of 20 congeners (di-octaBDEs), with BDE-47 and -99 being the most predominant

0.35−11 81−82

Emissions of BDE-209 were estimated to be 0.012−1.2 kg/y for households and 0.83−31 kg/y for public buildings. These emissions are based on area estimates that do not include industrial buildings and total emissions may thus be underestimated. The maximum total estimated emissions of BDE-209 (32 kg/y) were higher than for ∑pentaBDE (9.6 kg/ y), which probably reflects the higher use of decaBDE technical products in Europe (91% of total PBDE use in 2001).61 The estimated BDE-209 emissions from households may be underestimated as Thuresson et al.29 found that median BDE-209 concentrations in indoor air were approximately 10 times higher in single detached houses than in apartments from Stockholm. There are numerous other sources of under- and overestimation. The ventilation outflows may actually be higher than the estimated values given here for office buildings and day care centers, which would lead to underestimation of emissions. However, ventilation system flows are also reduced at night in offices and day care centers when no people are in the buildings, which could indicate that the ventilation outflows for these and thus the emissions data are somewhat overestimated instead. The ranges of annual emissions are wide, spanning 1−2 orders of magnitude due to the wide variation in measured PBDE concentrations as well as the variable ventilation outflows. Because of the possible sources of under- and overestimation discussed above these values may have even wider ranges. Using the ventilation outflow range values converted to m3/ h/m2 and the concentration ranges for ∑pentaBDE and BDE209 converted to ng/m3, estimated emission rates from the different building types to outdoor air were calculated (Table 3). For ∑pentaBDE, the emission rate range for public buildings was estimated to be 0.19−6.5 ng/h/m2. This is similar to 1 and 7 ng/h/m2 found for an office in the UK, but lower than seen in US homes (20 ng/h/m2), a new office building (22 ng/h/m2) and a Canadian office (6−40 ng/h/m2).17−19,43 An even lower ∑pentaBDE emission rate range of 0.006−0.24 was estimated for households. These geographic differences in ∑pentaBDE emission rates probably reflect the higher use of technical pentaBDE products in North America. For BDE-209, our emission rate ranges for offices and households to outdoor air were estimated to be 0.83−31 ng/h/m2 and 0.012−1.2 ng/

buildings, ventilation outflows were estimated by replacing the norm of 0.35 L/s/m2 with the high and low value for measured ventilation outflows obtained from apartments. For offices, new values were then calculated by multiplying the apartment ventilation outflow values with the surface area of the sampled office and adding 7 L/s to this for each person using the office (usually one person), summing these and dividing by the surface area of the office. For day care centers, we used the total surface area of the entire center and the total number of persons usually in the building for the calculations. The ranges of estimated ventilation outflows for offices (0.56−1.4 L/s/m2) and day care centers (0.77−1.8 L/s/m2) were similar. Therefore, the highest and lowest values (0.56−1.8 L/s/m2) were used in further calculations (Table 3). The ventilation outflows for apartments only and for offices and day care centers combined were converted to annual ventilation outflows and these were 3800−21400 m3/y/m2 and 17600− 56800 m3/y/m2, respectively (Table 3). The total area of heated surfaces in Swedish residential and public buildings was recently reported to be 6.78 × 108 m2 based on tax authority information from property owners.60 This was further broken down into houses (2.77 × 108 m2), apartment buildings (1.60 × 108 m2) and public buildings (1.53 × 108 m2).60 We have assumed that apartments were also representative of houses in the following estimations and have thus combined their heated surface areas (4.37 × 108 m2). We have assumed that offices and day care centers are representative of public buildings. The 10th and 90th percentile concentration ranges in apartments (15−98 pg/m3) and offices and day care centers (95−1000 pg/m3) for ∑pentaBDE as well as BDE-209 (7−130 pg/m3 and 310−3600 pg/m3, respectively) based on levels found in outgoing air from the current study were used. Using the heated surface area, estimated range of annual ventilation outflows and concentration ranges for ∑pentaBDE and BDE-209 in each building type (households, public buildings), the range of total emissions for Sweden in kg/y were calculated (Table 3). We made the assumption that the PBDE concentrations measured in Stockholm were representative for similar building types for all of Sweden. These gave estimated ∑pentaBDE emissions of 0.024−0.92 kg/y for households and 0.26−8.7 kg/y for public buildings. 5881



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Table 5. Estimated Emissions of BDE-209 to Outdoor Air in Sweden (See SI for Full Description of Calculations and References) source

emission factor

activity (kg/year)

annual emission (kg/ year)

comment

plastics manufacturing metals manufacturing

1.6 × 10−9 − 1.4 × 10−7 g/g used

1200

2 × 10−6−1.7 × 10−4

concerns BDE-209 only

37 − 64 μg/tonne product

1.7 × 109

0.062−0.1

municipal incineration electronics recycling e-waste fires landfill fires indoor environment− households indoor environment− public buildings total percentage total contribution of indoor air

1 × 10−7−1.8 × 10−6 g/g used

2−122

2 × 10−5−2 × 10−4

concerns sum of BDE-206, -207, -208 and -209, the latter representing ca. 90% of the EF concerns BDE-209 only

8 × 10−9−5 × 10−6 g/g input

9 × 104 −5.6 × 105

7.2 × 10−4−2.8


75−1200 μg/kg burnt material 5−88 μg/kg C burned 7−220 pg/m3

1.48 × 106 7 × 104−7 × 105 1.7 × 1012−9.4 × 1012 m3/year

0.1−1.8 4 × 10−4−0.006 0.012−1.2

concerns BDE-183 and -209 concerns BDE-209 only concerns BDE-209 only

220−4000 pg/m3

2.7 × 1012−8.7 × 1012 m3/year

0.83−31


1.0−37 84−87

h/m2, respectively. There are no data for BDE-209 emission rates to outdoor air to compare with our results. As stated before, there are a number of possible sources of under- and overestimation in these estimations, indicating that the emission rates may have even wider ranges. In order to understand the possible significance of emissions from indoor air, substance flow analysis (SFA) methodology was applied to give a rough estimate of total emissions of ∑pentaBDE and BDE-209 to outdoor air for all of Sweden20 (see also SI for full description of calculations and references). The sources considered included emissions from metals and plastics manufacturing, waste incineration, electronics recycling, e-waste, and landfill fires, as well as from the indoor environments and the assumption was made that these were the major sources of PBDEs to outdoor air. For example, a possible missing source that could be important is evaporative losses to air from landfills containing waste flame-retarded with PBDEs, but currently no emissions data are available for this source. Table 4 shows the estimated total emissions of ∑pentaBDE calculated from the SFA, which are underestimated due to lack of data on emission factors from municipal incineration and electronics recycling. Table 5 shows the estimated total emissions of BDE-209 determined from the SFA. As evident from the tables, the indoor environment may contribute substantially to the total estimated emissions of ∑pentaBDE and BDE-209 to outdoor air. However, these estimates should be viewed with some caution as they may be somewhat overestimated for reasons discussed above. Thus, the results of this study suggest not only that indoor air is contaminating outdoor air but that it could be a significant source of the PBDEs, including BDE-209, found in outdoor air. Our results indicate that there is a direct chain of emissions from flame-retarded products, which outgas PBDEs to indoor air leading to high concentrations indoors. The indoor air travels via ventilation systems virtually unchanged and is released to the outdoors. Once released, indoor air is diluted in the larger volume of outdoor air with subsequent transport away from buildings and urban areas, leading to the urban to rural gradients seen in other studies. Once in the atmosphere,

PBDEs, including BDE-209, can also undergo long-range atmospheric transport. Thus, release of PBDEs from applications indoors is a source to the outdoor environment, leading to contamination of food webs and subsequently human food sources.12

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ASSOCIATED CONTENT

S Supporting Information *

Detailed description of sampling and analysis, one figure of PBDE concentrations in indoor air from individual apartments compared to outgoing air from the same building, text (including one figure) with description of calculations for estimated total emissions of PBDEs to outdoor air including references. This information is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Phone: +46 8 674 7180; fax: +46 8 674 7638; e-mail: cynthia. [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank Karin Syversen, Thorvald Staaf and Caroline Bergh (Stockholm University) for help in collecting the air samples and Rebecca Thorén and Maria Zetterstedt (Department of Occupational and Environmental Medicine, Karolinska Hospital) for organizing the sampling in the apartments. This study was supported financially by the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS), the Environmental Board of Stockholm City, and the Stockholm County Council (3H Project-Healthy Sustainable Houses). A part of this work was financed by the COHIBA project, a cofinanced Interreg project by the European Union within the Baltic Sea Region Programme 2007-2013 (www.cohiba-project.net). 5882



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