Exposure to Flame Retardants in Commercial Aircraft 1

Technical Report - 2012

Exposure to Flame Retardants in 

Commercial Aircraft

National Air Transportation Center of Excellence for 

Research in the Intermodal Transport Environment (RITE) 

Airliner Cabin Environmental Research (ACER) Program

Prepared by: 

John D. Spengler

Joseph G. Allen

Eileen McNeely

Harvard School of Public Health

Boston, MA 02215

In cooperation with: 

Clifford Weisel, University of Medicine and Dentistry of New Jersey

Ann Louise Sumner, Battelle Memorial Institute

Technical Report

2012

Report No. RITE-ACER-CoE-2012-3
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Table of Contents

1.0 STUDY TEAM .................................................................................................................................3

2.0 COLLABORATORS ..........................................................................................................................3

3.0 BACKGROUND AND SIGNIFICANCE...............................................................................................4

4.0 METHODS AND RESULTS - 2011....................................................................................................8

5.0 FUTURE RESEARCH......................................................................................................................26

6.0 ACKNOWLEDGEMENTS...............................................................................................................28

7.0 REFERENCES................................................................................................................................29
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1.0 STUDY TEAM

John D. Spengler, PhD, Harvard School of Public Health (Principal Investigator)

Joseph G. Allen, DSc, MPH, Harvard School of Public Health (Co-Principal Investigator)

Eileen McNeely, RNP, PhD, MS, Harvard School of Public Health (Co-Principal Investigator)

2.0 COLLABORATORS/CONTRIBUTORS*

ACER/RITE

Clifford Weisel, PhD, University of Medicine and Dentistry of New Jersey 

Byron Jones, PhD, Kansas State University

Academic/Government/Industry

Ann Louise Sumner, PhD, Battelle Memorial Institute

Richard E. Lyon, PhD, Federal Aviation Administration Technical Center

Jose Vallarino, Harvard School of Public Health

Michael D. McClean, ScD, Boston University School of Public Health

Erin Collins, Boston University School of Public Health

Ashley Miller, Boston University School of Public Health

*Listing of collaborators and contributors is not intended to imply co-authorship of this report or 

their endorsement of the findings in this report. The collaborators and contributors were involved 

with various aspects of this research but did not contribute to the writing of this report or review the 

final report. 
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3.0 BACKGROUND AND SIGNIFICANCE

Flame retardant chemicals represent a broad range of compounds used in a wide variety of 

consumer and commercial products, including those used on commercial aircraft, to slow the 

propagation of fire. Polybrominated diphenyl ethers (PBDEs) are one class of brominated flame 

retardants that have garnered increased attention from the health community over the past ten years. 

There are 209 congeners of PBDEs with groups of congeners associated with the three commercial 

products: pentaBDE, octaBDE and decaBDE. PBDEs are found in a wide range of consumer products at 

up to 20% by weight, from plastics in television set housings to foam cushions in chairs and carpet 

backing (Allen et al. 2008b). Their widespread use, combined with their lipophilic nature and 

persistence in the environment, led to their ubiquitous presence in food, on surfaces, and in the air of 

both outdoor and indoor environments (e.g., offices, homes, cars, aircraft). Further, unlike many 

familiar persistent organic compounds where diet is the primary route of exposure, the indoor 

environment has been implicated as a critical route of exposure (Allen et al. 2007; Jones-Otazo et al. 

2005; Webster et al. 2005). Results of animal and in vitro studies suggest developmental reproductive 

and neurotoxic effects as well as endocrine disruption associated with exposure to these compounds 

(Birnbaum and Staskal 2004; Darnerud et al. 2001; McDonald 2002; Schreiber et al. 2009). Recent 

epidemiologic evidence suggests evidence of disruption of thyroid and sex hormone homeostasis (Chao 

et al. 2007; Hardell et al. 2006; Herbstman et al. 2010; Meeker et al. 2009; Meeker and Stapleton 2009). 

The use of PBDE in commercial products is in the process of being discontinued, with the EU banning 

commercial products containing penta-, octa- and decaBDE. In the US, penta- and octaBDE were 

voluntarily phased out by the manufacturers in 2004, with a similar voluntary phaseout for decaBDE 

planned for 2012. Even with these phaseouts and bans, vast reservoirs of PBDEs exist in products that 

are intended to be used for decades (Harrad and Diamond 2006; USEPA 2006).

To protect the flying public and flight crew it is essential that materials within aircraft have flame 

retardant properties. Several newer and commercially important flame retardant chemicals are now 

being incorporated into products to replace PBDEs (Stapleton et al. 2008; Stapleton et al. 2009). These 

include brominated flame retardants (tetrabromobisphenol A [TBBPA] and hexabromocyclododecane 

[HBCD]), chlorinated phosphates (Tris(diCl-isopropyl)phosphate [TCDPP]), and brominated phthalates (2-
Exposure to Flame Retardants in Commercial Aircraft 5

Technical Report - 2012

ethylhexyl-tetraBr-phthalate and Bis-(2-ethylhexyl)-tetraBr-phthalate [TBPH]). Toxicologic evidence 

suggests that these compounds may have important human health implications. For example, the 

chlorinated phosphate flame retardant being used today is similar to the brominated phosphate flame 

retardant used in children’s pajamas in the late 1970s which was found to be mutagenic (Gold et al. 

1978). 

Limited information is currently available regarding exposure to flame retardants on commercial 

aircraft. However, assessing exposure in this environment is gaining increased attention from 

researchers in this field. A poster presented at a conference on brominated flame retardants reported 

the single highest concentration of total PBDEs in dust anywhere in the world at that time was measured 

in lint collected from an airplane seat pocket (160,000 ng/g; n=1; (Gerecke 2007). The only peerreviewed paper specific to commercial aircraft also reported concentrations of PBDEs in dust from 

aircraft that can exceed the highest dust concentrations found in homes (Figure 1) (Christiansson et al. 

2008b).

Figure 1. Concentrations of BDE47 and BDE209 in dust (ng/g) from 20 individual aircraft as reported by 

Christiannson et al. (2008), and the median and maximum concentrations from home studies 

conducted in 11 cities in North America (Allen et al. 2008a; Harrad et al. 2008; Ibarra et al. 

2007; Rudel et al. 2003; Sjödin et al. 2008; Stapleton et al. 2005; Wilford et al. 2005; Wu et al. 

2007; Zota et al. 2008).

PBDEs in Dust (ng/g)

BDE 47 Dust Concentration (ng/g)

1e+0

1e+1

1e+2

1e+3

1e+4

1e+5

1e+6

Individual aircraft

Homes (studies)

BDE 209 Dust Concentration (ng/g)

1e+0

1e+1

1e+2

1e+3

1e+4

1e+5

1e+6

Individual aircraft

Homes (studies)
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Similar to the findings of elevated concentrations in dust from aircraft, flame retardant 

concentrations in air samples from aircraft can also be significantly higher than homes and worksites. In 

preliminary work associated with ACER, air samples previously collected (n=22) from Airline B were 

analyzed for two congeners of polybrominated diphenyl ethers (PBDEs). The highest PBDE 

concentrations from this analysis were found to be up to several orders of magnitude greater than air 

concentrations measured for occupationally-exposed workers and typical levels found in U.S. homes.

(Figure 2; median and maximum concentrations). 

BDE 47 BDE 209

Concentration (pg/m

3

)

1e+0

1e+1

1e+2

1e+3

1e+4

1e+5

1e+6

1e+7

1e+8

1e+9

Aircraft (n=22)

Plastic Recycling Plant

Homes (US)

Figure 2. Comparison median and maximum PBDE concentrations (pg/m3) in air samples collected from 

ACER aircraft, a plastics recycling plant (Sjödin et al. 2001), and homes in the U.S (Allen et al. 

2007).

Additionally, Christiansson et al. found that while body burdens of PBDEs in air travelers were 

similar to levels measured in the general population, the post-flight body burdens were higher than preflight body burdens suggesting travel-related exposure (Christiansson et al. 2008b). Recent evidence 

suggests an increased prevalence of thyroid disease in flight attendants. Increased levels of brominated 

flame retardants in women’s blood were recently associated with longer time to pregnancy (Harley et al. 
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2010). Flight crew’s potential for prolonged elevated exposures to these compounds which have thyroid 

hormone effects makes understanding flight crew body burdens a critical research need. 

The limited exposure data currently available suggest that aircraft may be a potentially relevant 

exposure environment for flame retardant chemicals. Additional research is needed to identify 

exposure-relevant flame retardants and fully elucidate the source-environment-receptor exposure 

pathways specific to commercial aircraft. In addition, finding elevated concentrations of flame 

retardants in aircraft air and dust indicates that these chemicals are migrating from their source 

products. It is not known if the loss of the flame retardant chemicals in the source products presents a 

safety issue due to loss of flammability protection. This study aims to address these knowledge gaps 

using a three-phased approach and drawing on the expertise of several ACER members and FAA 

technical experts.

The research described in this report, conducted in 2010-2011, aims to determine if flame retardant 

chemicals on aircraft pose a health risk to passengers and/or flight crew by addressing the knowledge 

gaps related to assessing potential exposure to flame retardants in commercial aircraft. The objectives 

of this study have been designed to specifically address the critical research needs related to assessing 

exposure to flame retardants in aircraft:

1) To identify flame retardants in commercial aircraft, conduct preliminary inhalation exposure 

estimates using previously collected samples, and develop ACER/RITE analytical capabilities

2) To assess source and exposure concentrations in relevant media in representative commercial 

aircraft.

3) To explore the potential associations between exposure (as measured by body burden) and early 

markers of thyroid function in flight crew. 
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4.0 METHODS AND RESULTS - 2011

To address knowledge gaps regarding exposures to PBDEs on aircraft, the FAA initiated a two-year 

research project designed to enhance our understanding of exposures to flame retardants (FRs) on 

aircraft. During that phase of the research, we collected in-flight air samples onboard aircraft, dust 

samples on aircraft and initiated a study of PBDE concentrations in the serum from flight attendants. 

4.1 Inhalation Exposure Assessment

4.1.1 Methods

Air Sampling

A total of 59 air samples were collected from 2009 to 2010, each from a different aircraft. 

Integrated samples were collected for the period of 10,000 feet ascending to 10,000 feet descending on 

all flights. A sampling manifold split the flows from the pumps to obtain the target flow for each sample 

type (additional air samples were collected for other analytes; results for those analytes are not 

reported here). Flows rates ranged from 1.5 to 8.6 liters per minute depending on flow requirements of 

other sample types collected concurrently. Flows for each sample were measured using a TSI model 

4146 volumetric flow meter (Shoreview, MN) and recorded at sample set up and take down and 

periodically checked during the flight. Samples were collected on two types of sorbent samplers, both 

of which consisted of two sections of polyurethane foam (PUF) and XAD-2 sorbent: commerciallyavailable tubes for low-volume sampling (SKC 226-143) and samplers prepared in-house using 5 g of precleaned XAD-2 (Supelco) sandwiched between two sections of pre-cleaned PUF (Supelco, one half PUF 

plug per sampler), packed in a freshly-muffled glass cartridge (URG). The sorbent tubes were shipped 

and maintained chilled after field spiking with deuterated surrogates until sample extraction. 

Samplers were spiked with surrogate recovery standards (SRSs) before transferring to either a 

Soxhlet extractor or Accelerated Solvent Extractor (ASE, Dionex) cell. Samplers were extracted in 

dichloromethane (DCM) or 1:1 hexane:DCM for Sohxlet and ASE extraction, respectively. Extracts were 

solvent-exchanged into methyl-t-butyl ether (MTBE) and concentrated to 100 μL. The QC samples 
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included solvent method blanks, matrix blanks and matrix spikes (10 ng each analyte). BDE 126 and 13C12

BDE 209 were added to the matrix as surrogate recovery standards (SRSs; 15 to 40 ng each, depending 

on analyte and sample set) just prior to extraction to assess method performance on a sample-bysample basis, and to provide correction for analytical losses, with BDE 126 as SRS for the PentaBDE and 

OctaBDE congeners, and 13C12 BDE 209 for BDE 209. Dibromobiphenyl was added to the extract just prior 

to analysis as the internal standard (IS). Samples were analyzed using GC/MS in the multiple ion 

detection mode using negative chemical ionization with methane reagent gas. The GC column (DB-5, 15 

m, 0.25 mm id, 0.10 um film thickness) was programmed from 100-300 °C at 30 °C/min. Quantification 

was performed using the internal standard method, against a 5 point calibration curve, covering 2 to 150 

ng/mL (plus a zero level standard; range for BDE 209 was 4 to 300 ng/mL), that was analyzed with each 

set. Calibration curves were generated using a linear least squares method. Analyte concentrations in 

samples (including blanks and spikes) were corrected by the corresponding SRS recovery value; then, 

analyte concentrations in field samples and spiked samples were corrected by average SRS-corrected 

blank values.

Quality Assurance/Quality Control

QA/QC samples included field blanks, matrix blanks and field duplicates. SRS recoveries for BDE 126 

were higher for Soxhlet and longer-duration ASE extraction method (average of 89%) compared to a 

shorter-duration ASE method (average of 24%). For 13C12BDE 209, recoveries were higher with Soxhlet 

extraction (76% on average) compared to either ASE extraction duration (37% and 16% for long and 

short-duration ASE, respectively). Blanks for commercially-prepared samplers were consistently higher 

than for laboratory-prepared samples by approximately a factor of 10, with average values of 2 and 0.3 

ng/sampler, respectively. It is likely that PDBEs were present in the polyurethane foam in the sampling 

media. Sample results were corrected for contamination of sampling media. Analyte recoveries in 

matrix spike samples were similar to matched SRS recoveries, confirming that SRS spike recoveries 

provide a reasonable estimate of extraction efficiency. Further research is needed to determine the joint 

effects of the amount of co-extracted material from the sampler matrix; extraction method, solvent, and 

duration/time; and source/lot of sampler material on analyte recoveries. Variability in the matrix spike 

recoveries demonstrate that it is critical to include 13C12BDE 209 SRSs since it appears that BDE 209 

recovery is impacted by the variables listed above and possibly others. Instrument limits of detection are 

low, approximately 0.2 ng/mL, so method detection limits (MDLs) are driven by background 
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contamination of the samplers, which is best characterized from field blanks. MDLs were defined as 

three times the standard deviation of field blanks. On average, MDLs for PentaBDE, OctaBDE, and 

DecaBDE congeners were 1.0 (n = 5 sample batches), 3.6 (n = 3), and 1.1 (n = 5) ng/sampler, 

respectively. Note that MDLs were determined for each sampler batch/extraction method. Analysis of 

duplicate pairs indicated good detect v. non-detect agreement (90%) and precision (median coefficient 

of variation = 13%). 

Daily Dose Calculations

Average daily dose (ADD) was calculated using a similar methodology employed by the U.S. 

Environmental Protection Agency (EPA) to derive ‘Public Health Levels’ for PCBs in schools (USEPA 1997, 

2010). ADDs for aircraft and non-aircraft exposures were calculated using the formulas and assumptions 

presented in Table 1, weighted by the time spent in each environment. Aircraft exposures totaled 1000 

hours per year to simulate a typical flight attendant duty schedule (Schecter et al. 2011). PBDE 

exposure concentrations were obtained from data from this study and the peer-reviewed literature 

(Allen et al. 2007; Allen et al. 2008a; CARB. California Air Resources Board 2005; Christiansson et al. 

2008a; Lorber 2008). ADDs were calculated using 95th percentile estimates of inhalation rate, dust 

ingestion and median exposure concentrations for non-aircraft and aircraft exposures. A high estimate 

of ADDs was then calculated by substituting median aircraft exposure concentrations with 95th

percentile values. 

Derived Inhalation Exposure Limits 

Inhalation exposure limits were derived for congeners measured in this study with published RfDs 

(BDEs 47, 99, 209) ((USEPA 2008a, b, c). To derive the inhalation exposure limits, ADDs were calculated 

in the same manner described above for all exposure pathways excluding inhalation aboard aircraft 

using the high estimate of ADD. This ADD was then subtracted from the RfD for each congener. The 

difference represents the average daily dose that a worker could receive from inhalation of PBDEs 

aboard aircraft, accounting for all other exposure pathways, without the total dose exceeding the RfDs. 

To derive an inhalation exposure limit from this maximum inhalation ADD, we back-calculated the 

maximum exposure concentration using the same assumptions for inhalation exposure presented in 

Table 1. 
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Statistical Methods

Summary statistics and Spearman correlations were calculated using SAS Statistical Software, 

version 9.0 (Cary, NC), and graphs were produced using SigmaPlot graphing software (Systat Software 

Inc., San Jose, CA). Data less than the MDL were substituted with 1⁄2 MDL for calculating summary 

statistics. Bayesian Decision Analysis (BDA) was conducted using a method described by Hewett et al. 

and the American Industrial Hygiene Association (AIHA) (AIHA 2009; Hewett et al. 2006) and performed 

using IH Data Analyst Software (Exposure Assessment Solutions, Inc., Morgantown, WV). We assumed a 

non-informative prior and data satisfied log-normal distribution assumptions for BDA. The 95th

percentile exposure values were calculated using log-probit regression to account for left censored data. 

Exposure categories were classified based on guidance on control banding from the American Industrial 

Hygiene Association (AIHA) (AIHA 2006, 2009). 

4.1.2 Results

PBDEs in Aircraft Air

In-flight concentrations of PBDEs in air are presented in Table 1. BDE 47 was detected in 63% of 

samples with a median concentration of 1.3 ng/m3(range: <0.04 – 20 ng/m3) and BDE 209 was detected 

in 42% of samples with a median concentration of <1.2 ng/m3(range: ND – 2,100 ng/m3). BDE 99 and 

BDE 100 were detected in fewer than 30% of samples due to higher limits of detection as a result of 

background levels in the sampling media, with maximum concentrations of 41 and 9.4 ng/m3, 

respectively. BDE 183 was detected in 11 of 34 samples (median concentration = <1.3 ng/m3; maximum 

concentration = 98 ng/m3). In an analysis of detected values only, the concentrations of the congeners 

associated with the PentaBDE commercial product (BDEs 47, 99, 100) were moderately to strongly 

correlated (Spearman R: 0.72-0.93, p<0.01). There was suggestive evidence of a moderate correlation 

between BDE 47, BDE 99 and BDE 209 (Spearman R: 0.43, p=0.11; 0.65, p=0.06). BDE 183 and BDE 209 

were also correlated (Spearman R: 0.76, p=0.01). A sufficient number of detected samples were not 

available for correlation analysis of the PentaBDE congeners and BDE 183. 
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 Table 1. In-flight PBDE concentrations (ng/m3) in air

Congener n Pct Detect Median 75th Pctile 95th Pctile Max

BDE 47 59 63% 1.3 2.8 5.1 20

BDE 99 59 22% <1.3 <11 27 41

BDE 100 59 29% <0.4 0.8 6.3 9.4

BDE 183 34 32% <1.3 25 82 98

BDE 209 59 42% <1.2 5.3 39 2100

Daily Dose Estimates for Flight Crew

Total average daily dose (ADD) for non-aircraft exposures was calculated as 5.2 ng/kg-day for the 

five congeners. The non-aircraft exposure was dominated by dietary and dust ingestion, which 

accounted for over 95% of the non-aircraft dose. Average daily dose in aircraft, using median values for 

dust concentrations in aircraft (Christiansson et al. 2008a), median air concentrations from this study 

but high estimates of dust ingestion and inhalation rates (USEPA 1997), were calculated as 3.4 ng/kgday. High estimates of average daily dose in aircraft, calculated using 95th percentile concentrations in 

aircraft from the same studies, was 61 ng/kg-day. 

Derived Inhalation Exposure Limits

The calculated ADDs for BDEs 47, 99 and 209 do not exceed each congener’s individual reference 

dose (Rfd) (EPA does not have a published RfD for BDE 100 or BDE 183). On a congener by congener 

basis, the calculated total ADDs from all non-aircraft and aircraft exposures, excluding the fraction from 

inhalation exposures onboard aircraft, were subtracted from EPAs RfDs for each congener. For the most 

health-protective scenario (i.e., highest estimates of background exposure), the remaining dose was 84 

ng/kg-day, 73 ng/kg-day and 6981 ng/kg-day for BDE 47, 99, and 209, respectively. This translates into a 
Exposure to Flame Retardants in Commercial Aircraft 13

Technical Report - 2012

derived maximum inhalation exposure limit on aircraft of 2500 ng/m3, 2200 ng/m3and 206,000 ng/m3, 

respectively, that a flight crew member could be exposed to without exceeding EPAs RfDs. 

Likelihood Estimates for Exceeding Derived Inhalation Exposure Limits

The derived inhalation exposure limits are several orders of magnitude higher than the measured air 

concentrations in this study (Figure 3). The 95th percentile air concentrations in this study (Table 2) are 

less than 1% of the calculated maximum inhalation exposure limit. Based on guidance from the 

American Industrial Hygiene Association (AIHA), 95th percentile exposure concentrations that represent 

less than 10% of an OEL may be characterized as “Highly Controlled” (AIHA 2009). Results from Bayesian 

Decision Analysis indicate that the probability of 95th percentile air concentrations exceeding 1% of the 

exposure limit is zero for all congeners evaluated. 
Exposure to Flame Retardants in Commercial Aircraft 14

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Figure 3. Distribution of measured BDE 47 and BDE 209 concentrations (ng/m3) 

in this study in relation to the derived inhalation exposure limit for flight crew

4.1.3 Development of ACER/RITE Analytical Capabilities

Overview

Two methods for analyzing BPDE flame retardants from dust, wipe and air samples to be collected 

from aircraft were evaluate using a Gas Chromatograph/Ion Trap Mass Spectrometer (GC/ITMS) in the 

Selective Ion Storage (SIS) mode. The first was to use Solid Phase Ion Extraction as the injection method 

and the second was to use Automated Pressure Sealed Vessel Solvent Extractions method. These were 

evaluated as they minimize the amount of material required and the amount of time require for 

extraction by trained chemists. 

Instrumentation Sensitivity

Mass spectral considerations were used to improve sensitivities of the method using GC/ITMS in 

Selected Ion Storage (SIS) mode. A Saturn 2200 GC/MS ion trap mass spectrometer (Walnut Creek, CA) 

was used for analysis. The SIS mode has performed in these conditions: Target RIC of 21400 counts, 

Maximum ionization time of 65000usec, prescan ionization time of 100 usec, Background mass of 45 

m/z, RF dump value of 650 m/z. and emission current of 30 uamps were used. Saturn GC/MS 

workstation version 6.6 software was used for data acquisition, integration, and quantification. The 

method detection limits for extraction of Sandy soils are presented below (Table 2).

Table 2. Method Detection Limits (ng/g of dust) with SPME

Analyte MDL Analyte MDL

PBDE 17 0.012 PBDE 154 0.077

PBDE 28 0.011 PBDE 153 0.055

PBDE 71 0.009 PBDE 138 0.238

PBDE 47 0.043 PBDE 183 0.228

PBDE 66 0.124 PBDE 190 0.570

PBDE 100 0.036 HBCD 0.524

PBDE 99 0.039 TBBPA 10.8

PBDE 85 0.151
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SPME Method

The automated Solid Phase Ion Extraction (SPME) method for PBDE analysis was evaluated for filter 

paper and dirt/dust using GC/ITMS in the SIS mode for the compounds listed in Table 3. The samples 

were prepared using two extraction methods. A headspace (HS)-SPME method was used for filter paper, 

house dust and soil samples. A SPME fiber holder was used in conjunction with a LEAP Combi PAL 

autosampler (Figure 4) to perform the extraction and injection into the GC/MS. In the initial 

experiments, analytes were spiked onto filter paper to simulate dust wipes and on to a sandy soil as a 

dust surrogate.

Table 3. Compounds evaluated for SPME analysis

Haloethers MW Log Kow MDLs (PPB)

4-bromophenyl phenyl ether 249.1 4.94 0.5

4-chlorophenyl phenyl ether 204.7 4.69 0.5

bis (2-chloroisopropyl) ether 171.1 2.39 1.0

bis(2-chloroethyl) ether 143.0 1.56 0.5
Exposure to Flame Retardants in Commercial Aircraft 16

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Figure 4. LEAP Combi PAL autosampler

SPME Method from Filter Paper

Two SPME methods were evaluated to optimize both extraction efficiency and maximize sensitivity. 

The methods were segregated for the smaller, lower boiling PBDEs and the larger PBDEs. PBDE 17 to 99 

were done with method A while BDE 85 through TBBPA were analyzed with method B. The conditions 

for the SPME_Method A were: 65uM polydimetylsiloxane-divinylbenzene (PDMS/DVB)-coated SPME 

fiber, 0.3 to 0.5 g of filter, or soil in 20 mL vials, extraction time of 50 min, desorption time of 10 min, 

preinjection time of 2.58 min, incubation temperature of 135 °C, agitation speed of 350 rpm, agitation 

on time of 5 seconds, agitation off time of 2 seconds, vial penetration 25.0 mm, and injection 

penetration of 54.0 mm. 

The conditions for SPME_Method B were: Green-7uM polydimetylsiloxane(PDMS)-coated SPME 

fiber, 0.3 to 0.5 g of filter, dust or soil in 20 mL vials, extraction time of 70 min, desorption time of 10 

min, preinjection time of 2.58 min, incubation temperature of 185 °C, agitation speed of 350-500 rpm, 

agitation on time of 5 seconds, agitation off time of 2 seconds, vial penetration 25.0 mm, and injection 

penetration of 54.0 mm.

While the recoveries for the mid-weight compounds were acceptable they were poorer for the 

lightest and heaviest PBDEs and for HBCD and TBBPA (Figure 5). However, since a number of the 
Exposure to Flame Retardants in Commercial Aircraft 17

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recoveries from filter paper were acceptable the approach was considered promising enough to 

continue to see if the conditions could be optimized and could be used for dust samples.

Figure 5. Recovery of flame retardants from filter paper

SPME Method from Soil/Dust

The recovery from soil/dust was more difficult to improve. The equilibrium that defines the 

partition between fiber and sample matrix was not significantly driven to the fiber within normal 

operating parameters. Very high temperatures > 250 oC and long deposition times > 200 min provided 

little improvement in recovery. The soil/dust recoveries did not reach a high enough level to continue 

with SPME methods (Figure 6). It was judged that at least a 40% minimum recovery would be required 

to use stable isotopic internal standards to compensate for sub 100% recoveries. Thus, the SPME 

method was deemed not likely to provide adequate analytical results for use so another extraction and 

analysis protocol was evaluated.
Exposure to Flame Retardants in Commercial Aircraft 18

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Figure 6. Recovery of flame retardants from soil/dust

Automated Liquid Extraction

An Automated Pressure Sealed Vessel Solvent Extraction (PVSE) method for PBDE analysis in house 

dust using programmable temperature vaporization large volume injection and GC/ITMSMSMS was 

evaluated.

Pressure Sealed Vessel Solvent Extraction

The conditions for the PVSE methode were: 0.3 to 0.5 g of house dust in pressurized 20 mL vials, 4 

mL of methylene chloride as a extraction solvent, extraction time of 20 min, incubation temperature of 

100 °C, agitation speed of 600 rpm, agitation on time of 5 seconds, agitation off time of 2 seconds.

GC/ITMSMSMS Conditions

The Saturn 2200 GC/MS system described for the SPME evaluation was also used this analysis. The 

injector temperature program started at 100°C and held in a splitless mode for 1.5 min, the temperature 

was rated from 100°C–280°C at 100 °C/min and held for 15min. Other GC/MS parameters and 

conditions were maintained as described above. The two principal differences between the SPME and 
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PVSE GC/MS protocols were the use of a shorter column (quicker elution without loss of complete 

separation) and an MS/MS/MS mode to increase the signal to noise ratio.

A triple stage Mass Spectrometry (MS/MS/MS) method was performed as a detection tool. The 

primary procedure for MS3is the same as MS/MS, only an MS3experiment allows repeated isolation and 

CID using either resonant or non-resonant excitation. The optimized MS2and MS3parameters for each 

PBDE are summarized in Table 4a and 4b. 

Table 4a. Optimized MS/MS parameters for the analysis of PBDE standard.

Segment Time

(min.)

Precursor 

1

st Product Mass (m/z)

Excitation

Storage Levels (m/z)

Excitation 

Amplitude (Volts)

8.00 –13.00 247.0 109.0 0.20

13.00 –16.60 327.0 144.0 0.40

16.60 – 20.22 407.0 180.0 0.30

20.22 – 24.60 487.0 215.0 0.30

24.60 – 35.58 564.0 250.0 1.40

* The isolation window in m/z is 5.0 for all and their waveform type is resonant.

* Target RIC of 21400 counts, Maximum ionization time of 65000usec. Prescan ionization time of 

1500 usec, Background mass of 45 m/z, RF dump value of 650 m/z. and emission current of 30 

uamps

Table 4b. Optimized MS/MS/MS parameters for the analysis of PBDE standard.

Segment Time

(min)

Precursor 

1

st Product Mass (m/z)

Excitation

Storage Levels (m/z)

Excitation 

Amplitude (Volts)

8.00 –13.00 247.0

139.0

109.0

61.1

0.80

0.40

13.00 –16.50 327.0

220.0

144.0

96.9

1.00

0.40

16.50 – 20.22 407.0

298.0

180.0

131.0

0.90

0.40

20.22 – 24.60 487.0

376.0

215.0

165.9

3.40

0.40

24.60 – 36.00 564.0

456.0

250.0

201.3

4.00

0.40

* Target RIC of 21400 counts, Maximum ionization time of 65000usec. Prescan ionization time of 

1500 usec, Background mass of 45 m/z, RF dump value of 650 m/z. and emission current of 30 

uamps
Exposure to Flame Retardants in Commercial Aircraft 20

Technical Report - 2012

PBDE Recoveries from Dust for the PVSE Method

The overall recoveries and detection limits of the PVSE method were acceptable for use with 

labeled isotopes to correct for individual compounds (Table 5). Further optimization and comparison to 

a standard extraction method is on-going.

Table 5. Recoveries and Method Detection Limits (ng/g of dust) with PVSE

Analyte % Recovery MDL (ng/g) Analyte % 

Recovery

MDL (ng/g)

PBDE 17 72.9 0.20 PBDE 85 62.4 0.30

PBDE 28 38.9 0.26 PBDE 154 39.4 0.03

PBDE 71 15.9 1.32 PBDE 153 67.0 0.06

PBDE 47 67.6 0.20 PBDE 138 66.9 0.22

PBDE 66 23.9 0.66 PBDE 183 86.5 0.03

PBDE 100 116 0.17 PBDE 190 97.1 0.06

PBDE 99 300* 0.22

*PBDE 99 was present in the dust but the recovery has not been corrected

 for the background level yet, so it exceeds 100%.
Exposure to Flame Retardants in Commercial Aircraft 21

Technical Report - 2012

4.2 Aircraft Characterization and Exposure Assessment

4.2.1 Methods

Dust Sampling

Dust samples (n=40) were collected on aircraft using a standardized collection protocol based on 

previously published methods (Allen et al. 2008a; Rudel et al. 2003). Briefly, a cellulose extraction 

thimble is fit into a vacuum crevice tool made of Teflon and secured using a rubber O-ring. The sampling 

tool is then connected to a canister vacuum and researchers collect dust from a pre-defined surface area 

by drawing the crevice tool across the top of all surfaces. After dust collection, the thimbles are 

wrapped in aluminum foil, sealed in polyethylene zip bags and stored at −4 °C. Equipment is cleaned in a 

1% solution of detergent and hot water between sample collection to prevent cross contamination. 

Analytic Methods

Dust samples were sieved to less than 500 m to remove large debris. Sieving was performed using 

an ASTM certified metal sieve. Samples were analyzed for the broad range of flame retardants listed in 

Table 6 according to previously published methods (Stapleton et al. 2005; Stapleton et al. 2009)

Table 6. List of Target Analytes 

Category Analyte

Polybrominated diphenyl ethers (PBDEs)

BDE 47

BDE 99

BDE 100

BDE 209

Tris Halogenated Phosphates

Tris(1,3-diCl-isopropyl)phosphate (TCDPP)

Tris(2-Cl-ethyl)phosphate

Tris(2,3-diBr-propyl) phosphate

High-use brominated flame retardants (BFRs) tetraBromo bisphenol A (TBBPA)

Hexabromocyclododecane (HBCD)

Firemaster 550 compounds 2-ethylhexyl-tetraBr-benzoate (EHTBB)

Bis-(2-ethylhexyl)-tetraBr-phthalate (BEHTBP)
Exposure to Flame Retardants in Commercial Aircraft 22

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Source Identification by XRF

Bromine concentration in products, as determined by x-ray fluorescence, have been previously 

shown to be a useful indicator of PBDE concentration (Allen et al. 2008b). To identify materials on 

aircraft that were likely to contain PBDEs, we used a portable XRF analyzer (Innov-X, Woburn, MA) to 

quantify bromine concentrations in materials aboard 20 aircraft. Over 200 measurements were 

recorded (between 5 and 23 samples were collected per aircraft).

HEPA Filters

Onboard HEPA filters were collected from numerous aircraft (~100) in segments approximately 

10cm by 10cm. A relatively small portion of the filter was previously extracted for analysis for TCPS and 

metals; the portions that remain are archived at Kansas State University and the University of Medicine 

and Dentistry of New Jersey (UMDNJ). These samples represent different aircraft models and loading 

factors. An initial screening of all filters for bromine levels was done using XRF to determine which 

filters contain the highest bromine levels and therefore most likely to contain the highest quantities of 

brominated flame retardants and to ensure that the used filters have higher bromine levels than the 

filter material prior to conducting the detailed chemical analyses. 

Filter punches were received at room temperature and stored in a freezer until analysis. Keddeg 

(5418) and Donaldson (5229) filters were used in an initial evaluation of the planned extraction method 

(used previously on dust samples). For each filter type, 2 punches (duplicates) and one matrix spike 

(spikes ranged from 10-25 ng) were extracted by sonication in hexane:dichloromethane (DCM). 

Precipitates formed when the samples were concentrated, more so for the Keddeg filter samples. Some 

extracts were milky even after centrifuging. Due to the precipitates, a sample clean-up step using acid 

silica was used. The high-use brominated flame retardants and Firemaster 550 compounds are acid 

labile and not expected to withstand the clean-up step, but were included in the analyte list. 

Filters were extracted by sonicating in 12 mL of 1:1 hexane:DCM for 15 minutes. A 10-mL aliquot 

was removed and fresh hexane:DCM was added to the filter vial and sonicated for another 15 minutes. 

The two extract volumes were combined in a flask containing 1 g acid silica and were shaken for one 

hour at 75 RPM. The extract was decanted through a small plug of muffled glass wool, and the silica was 
Exposure to Flame Retardants in Commercial Aircraft 23

Technical Report - 2012

rinsed three times, with shaking for 10min each, with 10-mL of hexane:DCM. The final extract was 

concentrated under nitrogen with mild heating (45°C and 55°C) to concentrate the initial extract and 

solvent exchange into hexane for a final volume of 1 mL. Table 3 presents the surrogate recovery spike 

compounds and approximate amounts. 

The final extract was spiked with internal standard and transferred to a GC vial insert. This extract 

was analyzed using negative chemical ionization (NCI) GC/MS in multiple ion detection (MID) mode for 

BDEs using a DB-5 GC column (15m, 0.25 mm inner diameter (id), 0.10 μm film thickness, Agilent), with 

the GC oven temperature programmed from 100 to 200°C at 10°C/minute (min) and then 200 to 300°C 

at 30°C/min. 

The GC-MS was calibrated by analyzing calibration standards interspersed with the samples in each 

sample analysis set. Calibration curves for each analyte and SRS were generated; the correlation 

coefficient (r2) was ≥0.98 for each curve. Most of the calibration curves were linear and forced through 

the origin. The calibration standards were 0, 2, 10, 50, 100, and 250 ng/mL for all compounds except for 

BDE 183, which had the following calibration standards: 0, 4, 20, 100, 200, and 500 ng/mL. The 

calibration curve for 13C12 BDE 209 included standards at 0, 54, 95, 200, 325, and 650 ng/mL . 

Analyte concentrations were calculated based on relative response (analyte area/IS area) and applied to 

the appropriate calibration curve. It was discovered after the filter samples had been analyzed that the 

stock mix of native BDEs for the calibration curve contained 13C12 BDE 209 rather than unlabelled BDE 

209. As a result, the instrument response to 13C12 BDE 209 was applied for quantification of native BDE 

209. This is an entirely appropriate way to handle this situation, as the ionization efficiencies are not 

affected by the addition of the labeled carbon. 

4.2.2 Results

Dust, Filters and Source Identification by XRF

Only preliminary results for dust, filters and source concentrations aboard aircraft have been 

received from the laboratory and/or analyzed as of the date of this report. Final results are expected in 

mid-2012, and will be described in the Technical Report for 2013.
Exposure to Flame Retardants in Commercial Aircraft 24

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4.3 Flight Crew Body Burden and Relationship to Early Markers of Thyroid Effect

4.3.1 Methods

Overview

In the pilot phase of this project, we recruited 10 flight attendants through contact information 

supplied by the American Flight Attendant’s union (AFA). Inclusion criteria were flight attendants 

working a non-stop flight route from Boston within the next two months that is no less than 3 hours. 

These criteria allowed us to track exposures before and after flight duty (arrival city) that are connected 

to a specific aircraft and includes moderate exposure times. We collected samples from the flight 

attendant at the airport hub location before report to duty and at the hotel in the arrival city. 

Serum

Venous blood samples were collected and analyzed for several PBDEs (BDE 47, BDE 99, BDE 100, 

BDE 209) and represent an estimate of total absorbed dose. Briefly, two 10-ml Vacutainer red-top vials 

of blood were drawn from each participant by trained phlebotomists. The blood was drawn into 

evacuated plain tubes. The tubes were centrifuged and serum transferred to pre-washed glass bottles 

and kept at -20oC until analysis. From one vial, a 5-ml aliquot of serum was analyzed for PBDEs. Briefly, 

the serum samples will be extracted using a solid phase extraction cartridge (SPE), followed by an 

additional SPE cleanup step, methylation, and analysis using NCI GC/MS in the MID mode. The second 5-

ml aliquot was used for analysis of thyroid hormones.

Hand-wipes

Hand wipes were collected at the end of the flight according to the method described and validated 

by Stapleton et al (2008). Technicians collect samples using a sterile gauze immersed in 3.0mL of 

isopropyl alcohol and wiped the entire surface of the hand (1 sample per hand, 2 samples per person, 

one field blank). Samples were stored in pre-cleaned 50 mL glass centrifuge tubes for sample extraction 

and analysis of PBDE congeners at the lab. 
Exposure to Flame Retardants in Commercial Aircraft 25

Technical Report - 2012

Human Subjects

The study protocol involved the testing of human subjects and therefore research protocols are 

subject to review by an Institutional Review Board. All protocols were approved by the Harvard IRB 

before research is initiated.

4.3.2 Results

Laboratory results for serum samples, hand-wipe samples and thyroid hormone were received in late 

2011. The data are currently undergoing quality assurance reviews. Data analysis will be conducted in 

2012 and results will be reported in the Technical Report for 2013.
Exposure to Flame Retardants in Commercial Aircraft 26

Technical Report - 2012

5.0 FUTURE RESEARCH

5.1 Inhalation Exposure

The inhalation exposure concentrations described in this report were measured at cruising 

altitude, a time when aircraft ventilation rates are maximal and can exceed 15 air changes per hour. 

Ventilation rates while aircraft are on the ground are lower and therefore exposure concentrations in 

the aircraft could be higher during this part of travel. Future work should evaluate maintenance crew 

exposures because of the expected higher exposure concentrations while aircraft are on the ground and 

potential for longer exposure durations. 

5.2 Characterizing Dust Exposure

Preliminary analysis of dust concentrations aboard aircraft indicate that dust is an important route of 

exposure. Increasing the sample size beyond the 20 aircraft in this study and including dust from 

additional aircraft manufacturers is warranted. Further characterization of this exposure route is also 

necessary, including evaluating dust from different locations in the aircraft that are relevant to exposure 

(e.g., seats v. floors v. galley) and the form of the PBDE compounds in dust (e.g., attached to abraded 

plastic or fine particles) which can be determined using scanning electron microscopy. 

5.3 Understanding the Impact of Flame Retardant Migration from Source Products on Material 

Flammability

PBDEs are additive flame retardants (ie, not bound to the materials they are used in) and therefore 

migrate from the source materials into the environment. Evidence of this is the high concentrations of 

PBDEs in aircraft dust. What is not known is if the migration of flame retardant chemicals from the 

source materials causes a reduced flammability protection of that source material. Flammability testing, 

evaluating flame retardant emission rates, and characterizing the degree of loss of flame retardants in 

source material over time is warranted. 
Exposure to Flame Retardants in Commercial Aircraft 27

Technical Report - 2012

5.4 Alternate Flame Retardants

The PentaBDE and OctaBDE commercial products have been phased out, and DecaBDE is scheduled to 

be phased out in the coming year. Despite these phaseouts, aircraft will continue to be a source of 

PBDE exposure for many years due to the long usage life of the materials that flame retardants are 

incorporated into. As PBDEs are being replaced, however, exposure to a new class of compounds has 

already begun. Toxicological evidence suggests that many of these compounds, for example Tris(1,3-

diCl-isopropyl)phosphate (TCDPP), could have potentially important health impacts. Examining 

exposure to these “new” flame retardants, and characterizing their changing use and exposure patterns 

over time on aircraft, is therefore a critical research need.
Exposure to Flame Retardants in Commercial Aircraft 28

Technical Report - 2012

6.0 ACKNOWLEDGEMENTS

This study was funded by the US Federal Aviation Administration (FAA) Aviation Safety Office of 

Aerospace Medicine through the National Air Transportation Center of Excellence for Airliner Cabin 

Environment Research (ACER)/Research in the Intermodal Transport Environment (RITE), Cooperative 

Agreements 07-C-RITE-HU and 04-C-ACE-HU. Although the FAA has sponsored this project, it neither 

endorses nor rejects the findings of this research. Results of Cooperative Research between the 

American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., and Battelle Memorial 

Institute. The researchers thank the participating airlines for their invaluable support.
Exposure to Flame Retardants in Commercial Aircraft 29

Technical Report - 2012

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