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Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=uoeh20 Journal of Occupational and Environmental Hygiene ISSN: 1545-9624 (Print) 1545-9632 (Online) Journal homepage: http://www.tandfonline.com/loi/uoeh20 Airborne contaminants during controlled residential fires Kenneth W. Fent, Douglas E. Evans, Kelsey Babik, Cynthia Striley, Stephen Bertke, Steve Kerber, Denise Smith & Gavin P. Horn To cite this article: Kenneth W. Fent, Douglas E. Evans, Kelsey Babik, Cynthia Striley, Stephen Bertke, Steve Kerber, Denise Smith & Gavin P. Horn (2018) Airborne contaminants during controlled residential fires, Journal of Occupational and Environmental Hygiene, 15:5, 399-412, DOI: 10.1080/15459624.2018.1445260 To link to this article: https://doi.org/10.1080/15459624.2018.1445260 © 2018 JOEH, LLC View supplementary material Accepted author version posted online: 01 Mar 2018. Published online: 01 Mar 2018. Submit your article to this journal Article views: 1245 View related articles View Crossmark data

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Page 1: Airborne contaminants during controlled residential fires · 400 K.W.FENTETAL. particulate and chemical asphyxiants. The mechanistic rolethatairpollutantsplayintriggeringacardiovascular

Full Terms & Conditions of access and use can be found athttp://www.tandfonline.com/action/journalInformation?journalCode=uoeh20

Journal of Occupational and Environmental Hygiene

ISSN: 1545-9624 (Print) 1545-9632 (Online) Journal homepage: http://www.tandfonline.com/loi/uoeh20

Airborne contaminants during controlledresidential fires

Kenneth W. Fent, Douglas E. Evans, Kelsey Babik, Cynthia Striley, StephenBertke, Steve Kerber, Denise Smith & Gavin P. Horn

To cite this article: Kenneth W. Fent, Douglas E. Evans, Kelsey Babik, Cynthia Striley, StephenBertke, Steve Kerber, Denise Smith & Gavin P. Horn (2018) Airborne contaminants duringcontrolled residential fires, Journal of Occupational and Environmental Hygiene, 15:5, 399-412,DOI: 10.1080/15459624.2018.1445260

To link to this article: https://doi.org/10.1080/15459624.2018.1445260

© 2018 JOEH, LLC

View supplementary material

Accepted author version posted online: 01Mar 2018.Published online: 01 Mar 2018.

Submit your article to this journal

Article views: 1245

View related articles

View Crossmark data

Page 2: Airborne contaminants during controlled residential fires · 400 K.W.FENTETAL. particulate and chemical asphyxiants. The mechanistic rolethatairpollutantsplayintriggeringacardiovascular

JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE, VOL. , NO. , –https://doi.org/./..

Airborne contaminants during controlled residential fires

Kenneth W. Fenta, Douglas E. Evansb, Kelsey Babika, Cynthia Strileyb, Stephen Bertkea, Steve Kerberc,Denise Smithd,e, and Gavin P. Horne

aDivision of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health (NIOSH), Cincinnati, Ohio;bDivision of Applied Research and Technology, NIOSH, Cincinnati, Ohio; cFirefighter Safety Research Institute, Underwriters Laboratories,Columbia, Maryland; dHealth and Exercise Sciences Department, Skidmore College, Saratoga Springs, New York; eIllinois Fire Service Institute,University of Illinois at Urbana-Champaign, Urbana-Champaign, Illinois

KEYWORDSFirefighters; HCN; overhaul;PAHs; particulate; VOCs

ABSTRACT

In this study, we characterize the area and personal air concentrations of combustion byproductsproduced during controlled residential fires with furnishings common in 21st century single familystructures. Area air measurements were collected from the structure during active fire and over-haul (post suppression) and on the fireground where personnel were operating without any respi-ratory protection. Personal air measurements were collected from firefighters assigned to fire attack,victim search, overhaul, outside ventilation, and command/pump operator positions. Two differentfire attack tactics were conducted for the fires (6 interior and 6 transitional) and exposures werecompared between the tactics. For each of the 12 fires, firefighters were paired up to conduct eachjob assignment, except for overhaul that was conducted by 4 firefighters. Sampled compoundsincluded polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs, e.g., benzene),hydrogen cyanide (HCN), and particulate (area air sampling only). Median personal air concentrationsfor the attack and search firefighters were generally well above applicable short-term occupationalexposure limits, with the exception of HCNmeasured from search firefighters. Area air concentrationsof all measured compounds decreased after suppression. Personal air concentrations of total PAHsand benzene measured from some overhaul firefighters exceeded exposure limits. Median personalair concentrations of HCN (16,300 ppb) exceeded the exposure limit for outside vent firefighters, withmaximum levels (72,900 ppb) higher than the immediately dangerous to life and health (IDLH) level.Median air concentrations on the fireground (including particle count) were above background levelsand highest when collected downwind of the structure and when ground-level smoke was the heav-iest. No statistically significant differences in personal air concentrations were found between the 2attack tactics. The results underscore the importance of wearing self-contained breathing apparatuswhen conducting overhaul or outside ventilation activities. Firefighters should also try to establishcommand upwind of the structure fire, and if this cannot be done, respiratory protection should beconsidered.

Introduction

Two of the most pressing health concerns in the fireservice are sudden cardiac events and cancer. Suddencardiac events are the leading cause of on-duty deathsin the fire service, accounting for 42% of such fatalitiesin the last 10 years.[1] For every on-duty sudden cardiacdeath, almost 17 non-fatal cardiac events occur during orimmediately after firefighting work.[2] The risk of suddencardiac death is 10–100 times higher during fire suppres-sion responses than non-emergency events, and this risk

CONTACT Kenneth W. Fent [email protected] Division of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety andHealth, Tusculum Ave., MS R- Cincinnati, OH .Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/uoeh.

Supplemental data for this article can be accessed on the publisher’s website. AIHA and ACGIH members may also access supplementary material athttp://oeh.tandfonline.com/.

remains elevated (2- to 10-fold) during the recovery timeafter a response.[3,4]

A combination of factors increases the risk of a suddencardiac event during fire suppression activities, includingphysical exertion, strenuous work, heat stress, dehydra-tion, and emotional stress. These stressors when coupledwith underlying morbidity, could result in pathologicalchanges increasing the risk of thrombosis, plaque rupture,or arrhythmia.[2] This risk may be further compoundedby exposure to pollutants on the fireground, such as

© JOEH, LLC

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400 K.W. FENT ET AL.

particulate and chemical asphyxiants. The mechanisticrole that air pollutants play in triggering a cardiovascularevent is not well understood,[5] but numerous epidemio-logic studies have consistently shown strong associationsbetween elevations in ambient fine particulate concen-trations and increases in hospital admissions (morbidity)and mortality rates in the general population.[6–8]

A number of epidemiologic studies have foundan increased risk for specific types of cancer infirefighters.[9–12] Daniels et al.[13] found a dose-responserelationship between fire-runs and leukemia mortalityand between fire-hours and lung cancer mortality andincidence. In 2010, the International Agency for Researchon Cancer (IARC) classified occupational exposure as afirefighter as possibly carcinogenic to humans (Group2B),[14] and this determination was made before manyof the aforementioned epidemiology studies.[9–13] Likecardiovascular disease, numerous risk factors exist fordifferent types of cancer. The plethora of chemical expo-sures encountered during fire responses is certainly onefactor that may increase firefighters’ risk of cancer.

The primary goal of this study was to gain a betterunderstanding of the time-course in the evolution, trans-port, and dissipation of airborne contaminants duringrealistic residential fire responses. Fire smoke is a complexmixture of substances and varies depending on the fuelbeing burned, combustion temperature, and ventilationconditions.[15,16] Toxic substances identified in fire smokein theUnited States include polycyclic aromatic hydrocar-bons (PAHs), volatile organic compounds (VOCs), poly-chlorinated biphenyls (PCBs), dioxins, plasticizers, flameretardants, carbon monoxide (CO), hydrogen cyanide(HCN), hydrogen chloride, hydrogen fluoride, nitrogenoxides, sulfur dioxide, heavy metals, asbestos, and otherrespirable particulates.[16–26] Many of these compoundsare known or potential human carcinogens and/or haveimportant cardiovascular implications. Some compounds(e.g., CO, formaldehyde, acrolein, benzene, nitrogendiox-ide, sulfur dioxide) have been measured during overhaulof structure fires at concentrations exceeding short-termexposure limits (STELs) or ceiling limits.[27] Overhaul isthe period of the response after fire suppression whenfirefighters search for any residual flames or smolderingitems. Historically, firefighters might remove their SCBAduring overhaul because of the weight and increased heatstress associated with wearing this respiratory protection.In recent years, many departments have begun to requireSCBA use during overhaul. Still, many departments areseeking guidance on when conditions are such that res-piratory protection may no longer be necessary in anattempt to balance firefighter’s risk for chemical exposureand heat stress.[30]

More work is needed to fully characterize the haz-ardous atmospheres encountered by firefighters. Thematerials found in 21st century buildings and furnishingsare increasingly synthetic and can generate many toxiccombustion byproducts when they burn.[15,16,28] We arenot aware of any study that has investigated themagnitudeof airborne contaminants over each phase of the response,the effects that firefighting tactics have on potential expo-sures, or airborne exposures by job assignment. In addi-tion, the literature is void of information on the potentialairborne exposures to personnel on the fireground whoare not directly engaged with the fire building (e.g., pumpoperator, incident commander, and paramedics). Thesepersonnel rarely, if ever, wear respiratory protection, eventhough it is certainly possible that they could be exposedto smoke from the fire or diesel exhaust (IARC Group 1carcinogen)[29] from the apparatus.

The purpose of this study was to measure the air con-centrations of combustion byproducts (i.e., PAHs, VOCs,HCN, and acid gases) and particulate produced duringresidential fires involving modern furnishings and sup-pressed with two different firefighting tactics in a con-trolled setting (at a firefighting training ground). Mea-surements were collected from the structure during activefire and overhaul, as well as on the fireground (near theapparatus). Personal air samples were also collected fromoperating firefighters in each job assignment and thoseresults are provided to compare among jobs, tactics used,and to put the area air measurements into perspective.Data on environmental conditions (e.g., wind directionand ground level smoke) were also collected to exploretheir effect on the air concentrations on the fireground.

Methods

Study population and controlled burns

This study was performed at the University ofIllinois Fire Service Institute (IFSI) with collabora-tion from the National Institute for Occupational Safetyand Health (NIOSH) and Underwriters Laboratories(UL) Firefighter Safety Research Institute (FSRI). Thestudy design is described in detail elsewhere.[25,30,31]

Briefly, using a repeated-measures design, study partic-ipants were grouped into 6 crews of 12 firefighters andeach crew was deployed to a pair of fire scenarios using2 different fire attack tactics (order of introduction wasbalanced). Six fire scenarios were suppressed using aninterior attack from the “unburned side” (advancementthrough the front door to extinguish the fire) and 6 fireswere suppressed with transitional attack (water appliedinto the bedroom fires through an exterior window prior

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JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 401

to advancing through the front door to extinguish thefire).

The 12 firefighters were paired up to complete 6 fire-ground job assignments including inside operations (fireattack, and search and rescue), outside operations (com-mand, pump operator, and outside ventilation), and over-haul operations. “Inside” and “outside” operations wereconducted during active fire suppression. After the firewas fully suppressed (as determined by the incidentcommander), the “overhaul” firefighters then entered thestructure to search for smoldering items and remove dry-wall and other items from the structure. Drywall and fur-niture was replaced with identical items (from a singlesource) after each fire.

The fire scenarios took place inside a 111 m2 residen-tial structure (Figure 1).[30] The 2 bedrooms where thefires were ignited were furnished with a double bed (cov-ered with a foam mattress topper, comforter and pillow),stuffed chair, side table, lamp, dresser, and flat screen tele-vision. The floors were covered with polyurethane foampadding andpolyester carpet. After ignition, the fireswereallowed to grow until the rooms flashed over and becameventilation limited (typically 4–5 min) and then the fire-fighters were dispatched.

Area air sampling

Table 1 provides a summary of our substrate-basedand whole-gas area air sample collection and analysismethods. An insulated cooler was modified for use insampling the air during the fire period (Figure 2). Holeswere drilled through the cooler so that Tygon tubingcould be inserted at various locations in the cooler.Sampling media was placed into the cooler and separatesections of tubing were used to connect the inlet of the

media to the interior of the structure (through pre-drilledhole in the wall) and outlet of the media to samplingpumps. Use of tubing to collect air from the structure wasdone to protect the sampling media from hot gases andwater. After each fire scenario, all sampling media werecapped and stored in a −20°C freezer prior to shipment(on ice) to the analytical laboratory.

For the live-fire portion of data collection, sampleswere collected 0.9 m above the floor in the living room toapproximate firefighters’ crawling/crouching height. Thetubing was wrapped in insulation to minimize aerosolcondensation. The sampling pumps were started justbefore ignition. Initially, ice packs were included in thecooler, but this practice was stopped after water conden-satewas found to accumulate in the samplingmedia. Sam-ple tubing was rinsed with water and dish soap mixtureafter each fire and then dried by running compressed airthrough the tubing. If this did not appear to effectivelyremove soot deposits, the sample tubing was replacedprior to the next fire. As the study progressed, we becameconcerned about sample loss within the sample tubing.Hence, for the last three fires, PAH sampling media waspositioned directly in the structure (next to the sampletubing from the tubing method) to compare the two sam-ple methods.

Evacuated glass bottles (1 L Bottle-Vacs, Entech) wereused to sample the air inside the structure for VOCs.Prior to sampling, a 15-min regulator (containing afritted pre-filter) was attached to the bottle. Tygon tubing(1.3 m in length) was attached to the inlet of the regulatorand the other end of the tubing was inserted into thestructure through the hole that was 0.9 m above the floor.Once the fire was ignited, the regulator was opened topermit air to be collected over a ∼15 min period. Afterthis duration, the remaining pressure was recorded andthe regulator removed (bottle closed).

Figure . Floor plan of the structure. Fires were set in bedrooms and or bedrooms and .

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402 K.W. FENT ET AL.

Table . Summary of substrate-based and whole-gas area air sampling methods.

Sampling performed Collection periods n

Periodduration(min)

Sampling timeduring eachperiod (min) Method

HCN FireOverhaul

A

– –

– –

Soda lime sorbent tube (SKC – ), mL/min, analyzed by UV/VIS

Acid gases: hydrogen bromide,hydrogen fluoride, hydrogenchloride, phosphoric acid

FireOverhaul

B

– –

– –

Silica gel tube (Supelco ORBO ), mL/min, analyzed by ionchromatography (NIOSH method)

PAHs: acenaphthene, anthracene,benzo[a]anthracene,benzo[a]pryrene,benzo[b]fluoranthene,benze[g,h,i]perylene,benzo[k]fluoranthene, chrysene,dibenzo[a,h]anthracene,fluoranthene, fluorene, indcon[,,cd]pyrene, naphthalene,phenanthrene, pyrene

BackgroundFireOverhaulFireground (during fire

and overhaul)

A

B

> – – –

– – – –

XAD- OVS tube (SKC – ), L/min,analyzed by HPLC/UV/FL (NIOSHmethod )

VOCs: benzene, toluene, ethylbenzene, xylenes

BackgroundFireOverhaulFireground (during

fire)

A

> – – –

∼∼∼∼

L evacuated bottle (EntechBottle-Vac) with -min regulatorand fritted pre-filter, analyzed by

GC/MSC

GC/MS = gas chromatography/mass spectrometry; HCN = hydrogen cyanide; HPLC/UV/FL = high performance liquid chromatography with ultraviolet andfluorescence detection; PAHs= polycyclic aromatic hydrocarbons; UV/VIS= ultraviolet-visible spectroscopy; VOCs= volatile organic compounds

A sample excluded due to sampling errorB samples excluded due to sampling errorCPre-concentrator with cryofocussing, GC column DB- M x . mm, µm, with time-of-flight MS system.

Figure . Overhead schematic of the air sampling set up usedto measure air concentrations inside the structure during the fireperiod.

After the fire had been suppressed and overhaulfirefighters began entering the structure, another set ofsampling trains were attached to the exterior wall of thestructure and the sampling media was inserted througha pre-drilled hole in the wall of the bedroom where thefire was ignited. This hole was 1.8 m above the floor toapproximate standing height. The pumps were promptlystarted and ran until a few minutes after the overhaulfirefighters exited the structure. An evacuated glass bottlewith Tygon tubing (2m in length) was also used to samplefor VOCs (over ∼15 min) through the same hole.

Area air samples were also collected in the fireground.An effort was made to place these samples downwindof the structure and in a location where fire personnelnot directly involved in firefighting (e.g., pump operatorand command) commonly operate. These samples werelocated either near the engine apparatus (northeast of thestructure) or truck apparatus (southeast of the structure),depending on the wind direction. Additionally, PAH andVOC samples were collected 12 hr before eight of the sce-narios to provide an estimate of background levels.

Table 2 provides a summary of the direct-reading par-ticle measurements. Particles were sampled through thefront wall of the burn structure using insulated stainlesssteel sample lines attached to a mobile particle samplingplatform previously described in detail.[32] The platform,adapted from similar work[21–23] but custom configuredfor this application, utilized a two-stage dilution withbypass for different phases of the fire response. Particle

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JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 403

Table . Summary of direct reading particle measurements.

Sampling performed Collection periodsNo. of eventssampledA

Samplingtime (min)

Dilutionfactor Measurement

Particle count using TSI CondensationParticle Counter (CPC)

BackgroundFireOverhaulFireground

– – – –

NA:NANA

Concentration of particles in the sizerange of – nanometers (nm)in diameter with a data output oftotal number of particles per cubiccentimeter (#/cm) of air

Respirable and thoracic massconcentration using TSI DRX AerosolMonitor

BackgroundFireOverhaulFireground

– – – –

NA:NANA

Mass concentrations of airborneparticles with % penetration at at um (respirable) and um(thoracic) aerodynamic diameters

Active particle surface area usingEcoChem Diffusion Charger DCCE

BackgroundFireOverhaulFireground

– – – –

NA:NANA

Active surface area of particles ( µm indiameter or less) that interacts withair or carrier gas

ALess than events were sampled for some exposure metrics due to sampling error or problems with the instrument(s).

concentration metrics reported here include the number,respirable and thoracic mass, and active surface area.

Personal air sampling

Personal air samples were collected for PAHs and HCNusing the same analytical methods and flow ratesdescribed in Table 1. Personal air samples for VOCs(benzene, toluene, ethyl benzene, and xylenes) were col-lected using charcoal tubes (SKC 226-01) at 200 mL/min,analyzed by NIOSH method 1501.[33] The samplingpumps were stored in pockets or straps on the outershell of the turnout jackets, and sampling media werepositioned near the collar of the jackets. Unlike the areaair samples, collected air did not travel through tubingbefore entering the personal sampling media. For all 12fires, firefighters assigned to fire attack (2 per fire), search(2 per fire), overhaul (4 per fire), outside ventilation (2per fire), and command/pump (2 per fire) were sampled.

Data analysis

Descriptive statistics and other data analyses were carriedout using SAS 9.4 software. For the personal air samples,which were started several minutes before each scenario,the time the pumps ran from dispatch until the firefight-ers were released from their assignments were used tocalculate the volume of air collected. For the area air sam-ples, the pumps were started and stopped at the begin-ning and end of each response period (i.e., fire and over-haul periods). Pump faults due to overloading of samplingmedia with particulate were common for the area air sam-ples (PAHs, HCN, and acid gases) collected during thefire period and for the personal air samples (PAHs, HCN,and VOCs) collected from the attack and search firefight-ers. For samples with pump faults, sample durations were

adjusted accordingly. Time of dispatch for attack firefight-ers was a median of 4.5 min after ignition, and water wasapplied to the fire a median of 6.5 and 7.3 min after igni-tion for transitional and interior attack, respectively.[30]

Hence, personal air samples that did not run for at least3min of the responsewere excluded because theymay notrepresent the average concentrations during themost crit-ical phase of the response (including suppression). Thisresulted in the exclusion of 6 HCN, 3 VOC, and 2 PAHpersonal air samples (data provided in Supplemental File).All area air samples ran for 4 min or longer (near the timeof dispatch), which we deemed to be sufficient for charac-terizing the fire atmosphere.

Total PAHs were calculated by summing the 15quantified PAHs. Zero was used for non-detectable con-centrations in this summation. The analytical limit ofdetection for naphthalene (0.5 µg) was used in calcu-lating the minimum detectable concentration for totalPAHs. A Kruskal-Wallis test was used to test whetherpersonal air concentrations varied by tactic (interior vs.transitional attack) for the attack and search firefighters.Spearman correlation analysis was used to assess theeffect of sampling time on area air concentrations duringthe fire period and personal air concentrations for theattack and search firefighters.

Because the direct-reading particle instruments tookmeasurements every 10 sec or less, summary statis-tics (i.e., median and range) for particle number, res-pirable mass, thoracic mass, and active surface area wereconducted on the arithmetic means calculated for eachresponse phase. To assess the influence of environmen-tal conditions on the fireground air concentrations, thepresence of ground level smoke was determined each dayof the study by a single investigator using visual evidence(i.e., smoke hanging near the ground vs. rising into theair) and wind direction was determined with a portableweather station (Omega WMS-23).

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404 K.W. FENT ET AL.

Results

Table 3 provides the personal air concentrations of HCN,PAHs, and benzene by job assignment. The most protec-tive short-term occupational exposure limits are also pro-vided for comparison. The median personal air concen-trations for attack firefighters exceeded the NIOSH STELforHCNof 4,700 ppb, the ACGIH excursion limit for coaltar pitch volatiles of 1,000 µg/m3, and the NIOSH STELfor benzene of 1,000 ppb.[34,35] Results were similar forsearch firefighters, except that median HCN concentra-tions were below the NIOSH STEL. Maximum personalair concentrations of HCN were well above IDLH levels(50,000 ppb)[33] for the attack, search, and—somewhatsurprisingly—outside vent firefighters. The maximumpersonal air concentrations of total PAHs and benzene forthe overhaul firefighters were above theACGIH excursionlimit for coal tar pitch volatiles (1,000 µg/m3)[34] and theNIOSH STEL for benzene (1,000 ppb), respectively.[34]

Statistically significant correlations were foundbetween sample time and personal air concentrationsof benzene (r = −0.71; P < 0.001) and HCN (r = −0.83;P < 0.001) for search firefighters and between sampletime and personal air concentrations of HCN (r= −0.61;P = 0.026) for attack firefighters, whereby increasingsample time was related to decreasing personal air con-centrations. No statistically significant correlations werefound between sample time and area air concentrationsfor any of the sampled compounds (P > 0.15 for allcomparisons). The personal air concentrations of totalPAHs, HCN, and benzene for the attack and searchfirefighters were compared by fire attack tactic (interiorvs. transitional). No statistically significant differences

were observed by this stratification (P > 0.10 for allcomparisons).

Table 4 provides a summary of the area air con-centrations measured from the living room during thefire period. As expected, median concentrations for sev-eral compounds exceeded their ceiling limits or STELs,including HCN, hydrogen bromide, hydrogen chloride,and benzene.[34,35] Occupational exposure limits do notexist for particulate in general; although ACGIH recom-mends that even biologically inert particulate should bekept below 3,000 µg/m3 as a respirable fraction and below10,000 µg/m3 as an inhalable fraction (as a time-weightedaverage over an 8-hr workday).[35] While the particulateproduced in these fires should not be considered bio-logically inert, inhalation exposure lasting <3 min couldresult in an 8-hr time-weighted average concentration ofrespirable particulate above the limit. However, as is typ-ically the case, the firefighters wore SCBA while insidethe structure during fire attack and were protected frominhaling these substances.

Figure 3 presents the individual PAH concentra-tionsmeasured using the direct-samplingmethod (mediainside the structure) and the tubing method (media incooler outside structure). These samples were collectedside-by-side during active fire for the last 3 scenarios.On average, the tubing method resulted in lower con-centrations of total PAHs (13% of the direct-samplingmethod), but the differences varied by PAH species withthe largest differences observed for acenaphthene (0.7%),fluorene (5%), naphthalene (0.6%), phenanthrene (23%),and anthracene (24%), which are all composed of 3 ringsor fewer (greater volatility). All other PAH concentrationsmeasured by the direct-sampling method were � 34%

Table . Summary of personal air concentrations by position.

Personal air concentrations

Analyte Assignment nA ND (%) Median Range Most protective short-term occupational exposure limitsB

HCN (ppb) Attack , , – , NIOSH STEL: , ppbSearch < – , NIOSH IDLH: , ppbOverhaul . < – ,Outside vent , – ,Command/Pump – ,

Total PAHs (µg/m) Attack , , – , ACGIH excursion limit (coal tar pitch volatiles): , µg/m

Search , , – ,Overhaul – ,Outside vent – Command/Pump < < –

Benzene (ppb) Attack , , – , NIOSH STEL: , ppbSearch , , – ,Overhaul . < – ,Outside vent < – Command/Pump < < –

AOver the fire scenarios, we sampled attack, search, outside vent, and command/pump firefighters, and overhaul firefighters. However, sample losses (earlypump faults, lost media) occurred due to extreme conditions. Also, samples that did not run for at least min of the response were excluded.

BBased on review of short-term exposure limits (STELs) or ceiling limits (C) as listed with NIOSH Recommended Exposure Limits, Occupational Safety and HealthAdministration (OSHA) Permissible Exposure Limits, and/or ACGIH R© Threshold Limit Values (TLVs). If no STEL or C exists, ACGIH excursion limits (x the TLV) areprovided.

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JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 405

Table . Area air concentrations measured from the living room during the fire period.

nAPercentage ofnon-detects Median Range

Most protective short-termoccupational exposure limitB

Acid gasesHCN (ppb) % , < – , NIOSH STEL: ,

NIOSH IDLH: ,Hydrogen bromide (µg/m) % , < – , ACGIH C: ,Hydrogen fluoride (µg/m) % < < – , ACGIH C: ,Hydrogen chloride (µg/m) % , , – , ACGIH C: ,Phosphoric acid (µg/m) % < < ACGIH C: ,

NIOSH STEL: ,Total PAHs (µg/m) % , – , ACGIH excursion limit: ,VOCsBenzene (ppb) % , . – , NIOSH STEL: ,Toluene (ppb) % . . – NIOSH STEL: ,Ethyl benzene (ppb) % . <. – . NIOSH STEL: ,Xylenes (ppb) % . <. – . NIOSH STEL: ,

ACGIH STEL: ,Direct-reading particle instrumentsParticle count (#/cm) NA ,, , – ,, NARespirable mass (µg/m) NA , , – , NAThoracic mass (µg/m) NA , , – , NAParticle surface area (µg/m) NA , , – , NA

ASampling errors (e.g., early pump faults, lost media, power failures) led to fewer than samples being collected for some metrics.BBased on review of short-term exposure limits (STELs) or ceiling limits (C) as listed with NIOSH Recommended Exposure Limits, Occupational Safety and HealthAdministration (OSHA) Permissible Exposure Limits, and/or ACGIH R© Threshold Limit Values (TLVs). If no STEL or C exists, ACGIH excursion limits (x the TLV) areprovided.

of the concentrations measured by the tubing method.It is important to note that the tubing method samplesran ∼5 min past suppression, while the direct-samplingmethod samples ran a few minutes shy of suppression.Because PAH concentrations are expected to decreaserapidly after suppression, the tubingmethod samplesmayhave become diluted compared to the direct-sampling

method. However, even if we adjust the sample volumesof the tubing method downward to essentially match thedirect-sampling method (see Supplemental File), we stillfind that the tubingmethod underestimates the total PAHconcentrations (20% of the direct-sampling method).

Figure 3 also provides the IARC classifications for eachPAH. Benzo[a]pyrene is the only PAH species that is a

1

10

100

1,000

10,000

100,000

PAH

conc

entr

a�on

s (μg

/m3 )

Tubing method Direct sampling method

Figure . Average total PAH concentrations measured from the living room during three fires using the tubing method (where air fromthe structure was drawn through tubing into the sampling media) and the direct-sampling method (where air from the structure wasdrawn directly into the samplingmedia). Also provided are the IARC classifications for each PAH species. Class = carcinogenic to humans;A= probably carcinogenic to humans, B= possibly carcinogenic to humans, and = not classifiable.

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406 K.W. FENT ET AL.

known human carcinogen (1) and it accounted for 2% ofthe total PAHs according to the direct-sampling method.PAHs classified as probably (2A) or possibly (2B) car-cinogenic accounted for 57% of the total PAHs accord-ing to the direct-sampling method. Note that naphtha-lene (2B) was the predominant species in this group ofprobably or possibly carcinogenic PAHsmeasured via the

direct-samplingmethod (accounting for 50%of the total),but only accounted for 2% of the total measured via thetubing method.

Figures 4A and 4B compare the fire period, over-haul period, and fireground air concentrations of totalPAHs and benzene. The maximum PAH concentra-tion measured during overhaul exceeded the ACGIH

Figure. (A) Total PAHand (B) benzene concentrationsmeasured fromthe living roomduring thefire, fromthe initial burn room(bedroom)during overhaul, and in the fireground during the response. The box and whiskers provide the minimum, th percentile, median, th

percentile, and maximum values. The shaded horizontal bar provides the interquartile range of the background levels (measured beforeignition) for benzene. Background concentrations of PAHs were non-detectable (<. µg/m) as represented by the dotted line. Dashedlines are provided for applicable exposure limits.

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excursion limit for coal tar pitch volatiles of1,000 µg/m3.[35] Fireground concentrations of PAHswere well below the levels measured during overhaul;both were above background levels. Median concentra-tions of benzene measured during overhaul and in thefireground were above background levels, but well belowapplicable STELs.[34,35] HCN concentrations duringoverhaul (median = 906 ppb, see Supplemental File)were also below the NIOSH STEL (4,700 ppb).[34]

Figures 5A and 5B present the sub-micrometer parti-cle number concentrations and respirable particle mass

concentrations, respectively, at different locations andtimes during each scenario. Median particle con-centrations followed the pattern: Fire >> Overhaul> Fireground during fire � Fireground during over-haul. While median fireground particle number andrespirable mass concentrations were at or near back-ground levels, the fireground levels were, on occa-sion, substantially higher than background as evi-denced by the 75th percentiles, which were nearlyan order of magnitude higher than background esti-mates. These upper levels likely occurred when the

Figure . (A) Particle number and (B) respirable mass concentrations measured from the living room during the fire, from the initial burnroom (bedroom) during overhaul, and in the fireground during the response. The box and whiskers provide theminimum, th percentile,median, th percentile, and maximum values. The shaded horizontal bar provides the interquartile range of the background levels.

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408 K.W. FENT ET AL.

wind carried smoke from the fires across the particleinstruments.

We evaluated the effect of environmental conditions,like wind direction, on fireground concentrations oftotal PAHs and benzene (Figures 6A and 6B). Medianconcentrations followed the pattern: Downwind of thestructure with heavy ground-level smoke > Downwindof the structure with minimal ground-level smoke > Notdownwind of the structure with minimal ground level

smoke. Active particle surface area also appeared tofollow this pattern (see Supplemental File). Of note,diesel exhaust from the nearby apparatus may havealso contributed particulate, gases, and vapors to oursamples. There was evidence for this in that, during4 scenarios, the transient particle number concentra-tions were elevated (6 to >10 fold) above ambient back-ground (in some cases>100,000 particles/cc) prior to fireignition.

Figure . (A) Benzene and (B) total PAH concentrations measured in the fireground stratified by environmental conditions. The box andwhiskers provide theminimum, th percentile,median, th percentile, andmaximumvalues. The interquartile range of background levelsis also provided for benzene. Background levels of PAHs were non-detectable (<. µg/m).

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Discussion

This study provides a thorough characterization of air-borne exposures during structural firefighting. We eval-uated firefighters’ airborne exposures by job assignmentand attack tactics used during realistic residential fireresponses.We also performed area air sampling for a vari-ety of compounds during active fire, overhaul, and on thefireground. Important determinants (environmental fac-tors) of the fireground concentrationswere also identified.Although this study has a number of limitations, includ-ing potential sample losses from the use of tubing to drawair from the structure, the findings are useful to the fireservice in identifying exposure risks and ways to mini-mize those exposures.

The personal air sampling results indicate that expo-sures will vary greatly by job assignment. The attack andsearch firefighters had the highest airborne exposures butwere also wearing SCBA during the response. While fire-fighters’ lungs may be protected by SCBA, some airbornechemicals could penetrate or permeate the turnout gearand be absorbed through skin.[31,36] These results, as wellas the area air concentrations measured inside the struc-ture during the fire, are also important for understand-ing the potential risks to trapped occupants or firefighterswho run out of air or otherwise remove SCBA.

The personal air concentrations of PAHs (attackmedian 23,800 µg/m3; search median 17,800 µg/m3)measured during the fires were comparable or higherthan those measured in other studies (ranging from<5–22,000 µg/m3).[26, 37–40] During a limited ventilationliving room fire, investigators at Underwriters Laborato-ries measured 624 µg/m3 of total PAHs, and naphthaleneand phenanthrene constituted the majority of the mix-ture (77% and 10%, respectively). Naphthalene (median50%) and phenanthrene (median 13%) were also themost abundant PAH species during the fires in our studyaccording to the direct-sampling method, which shouldprovide a more reliable estimate of the PAH compositionthan the tubingmethod. According to thismethod,>50%of the PAHs that were producedwere known (1), probable(2A), or possible (2B) human carcinogens as classified byIARC.

The personal air concentrations of benzene (attackmedian 40,300 ppb; search median 37,900 ppb) dur-ing the fires appear to be higher than the levels mea-sured in a study of structural firefighters’ exposuresby Jankovic et al.[26] (ranging up to 22,000 ppb). Thisstudy also reported HCN concentrations ranging upto 23,000 ppb.[26] Much higher maximum concentra-tions of HCN were measured from attack firefighters(100,400 ppb) and search firefighters (106,000 ppb) in ourstudy. It is important to note that the Jankovic study was

performed in the 1980s and may not represent currentconditions or fuel loads for today’s residential fires. Com-bustion of polyurethane foams, plastics, resins, and gluesused in the modern furnishings may have contributed tothe higher levels found in our study.

Because HCN is lighter than air (vapor density = 0.9),it likely partitioned more heavily into the upper smokelayer. As is normal practice, the interior firefighters triedto remain below the upper smoke layer. However, theattack firefighterswere often closer to the fires and inmoreupright positions duringwater application than the searchfirefighters. This could explain why attack firefighters hadhigher median HCN concentrations (33,500 ppb) thansearch firefighters (85 ppb).

The partitioning of HCN into the upper smoke layermay also explain why the outside vent firefighters hadthe second highest personal air concentrations of HCN ofall positions. Opening windows and ventilating the roofwhile standing near the openings and/or in elevated posi-tions likely exposed these firefighters to rising gases. Themedian personal air concentration of HCN (16,300 ppb)for the outside vent firefighters was well above the NIOSHshort-term exposure limit of 4,700 ppb. Because medianarea air concentrations inside the structure were greaterthan 160,000 ppb, transient concentrations in excess of theIDLH level of 50,000 ppb[34] are possible for firefighterswho encounter heavy smoke even when they are immedi-ately outside the structure conducting assignments suchas outside vent. In fact, themaximum time weighted aver-age personal air concentration (over 9 min) for outsidevent firefighters was 72,900 ppb. These results providestrong justification that SCBA should be used when con-ducting ventilation of a structure during the firefight.

As with outside ventilation activities, firefighters maynot always wear respiratory protection during overhauland rarely wear respiratory protection during exteriorsupport/command activities. Three of the 43 personaltotal PAH air concentrations measured during overhaul(1,230 µg/m3 for one fire and 1,330 and 2,220 µg/m3 foranother fire) exceeded theACGIHexcursion limit for coaltar pitch volatiles (1,000 µg/m3).[35] In a study of fire-fighters’ exposures during the overhaul phase of actualfire responses, Bolstad-Johnson et al.[27] found that thissame limit was exceeded in 2 of 25 structure fires. Twenty-three of 47 personal air concentrations of benzene mea-sured during overhaul in our study (ranging from 1,040–2,970 ppb, collected during 9 separate fires) exceeded theNIOSH STEL (1,000 ppb).[34] This is within the rangeof benzene concentrations measured by Bolstad-Johnsonet al.[27] (ranging from <70–2,000 ppb).

The maximum area and personal air concentrations ofHCNduring overhaul (906 and 1,380 ppb, respectively) inour study were below the NIOSH STEL (4,700 ppb).[34]

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410 K.W. FENT ET AL.

In 2 separate studies, Jankovic et al.[26] measured lowerlevels of HCN (ranging up to 400 ppb) and Bolstad-Johnson et al.[27] did not detect HCN (<900 ppb) dur-ing overhaul. Ventilation conditions in the structure arelikely to significantly impact how quickly residual gasesare removed from the structure. In these scenarios, the firebedroom where samples were collected had 2 relativelylarge windows and an open front door. Visible smokewithin the structure generally dissipated within the firstminute or two of overhaul. If less ventilation were avail-able or if the attack crews had not completed suppressionas thoroughly as done here, these concentrations couldhave been even higher during overhaul.

Using tubing to draw air from the structure during thefires appeared to result in underestimation of the actualconcentrations as evidenced by the comparison of PAHconcentrations measured with media inside the structure(direct-sampling method) vs. those measured using thetubing method (Figure 3). Estimates of potential parti-cle losses due to impaction, settling, and diffusion in thetubing based on particle size, tube velocity, tube bends,and area of tube inlet were calculated. Particle losses werelikely negligible from 1–10 µm. As a worst case, diffusionlosses of 10% were possible for particles 10 nm in diame-ter; however, these particles would compose only a smallfraction of the total count and an insignificant fraction ofthe total mass. Hence, we believe the particle losses in thesample tubes were negligible for both the substrate-basedsamples and direct-reading particle measurements.

The length of tubing used for the area air samplescould have essentially diluted the samples because “cleanair” in the tubing would have been collected during theinitial sampling period. However, based on calculatedair velocities within the tubing, no samples would havebeen diluted more than 15:16. Also, because tubing wascleaned and then reused for some of the scenarios, it ispossible that the tubing was not completely free of con-taminants. This could have contributed to the air mea-surements; although, we would expect any off-gassingcontaminant concentrations in the tubing to be muchlower than the air concentrations inside the structure dur-ing fire and overhaul.

Most likely, losses in the tubing were due to conden-sation of vapors to the tubing walls. Tubing was usedfor area air sampling during the fire period for all com-pounds and during the overhaul period for VOCs. Insu-lation was used around the tubing to minimize condensa-tion losses, but the temperature gradient was probably toogreat to fully prevent condensation. Temperatures insidethe structure were measured using strategically placedthermocouples.[30] The maximum temperatures near theinlet of the tubing during the fires were 114–198°C,

while temperatures at the location of the sampling media(outdoors) ranged from 13–20°C. Condensation ofvapors to the tubing walls would explain why apparentlosseswere greater for themore volatile PAHs (those likelyto be in gas-phase during collection) than the non-volatilePAHs (those likely to be in solid-phase). Condensationlosses would also be expected for the VOCs (i.e., benzene,toluene, ethyl benzene, and xylenes). With the exceptionof phosphoric acid (boiling point∼158°C), condensationlosses should be negligible for the acid gases (most withboiling points <20°C) and HCN (boiling point ∼26°C)as they should have remained in gas-phase until theyadsorbed to the sampling media.

Although no exposure limits exist for general particu-late, the median sub-micrometer particle count and res-pirable mass concentrations during overhaul were wellabove background levels. Particulate in this size rangeare capable of penetrating and depositing into the gas-exchange regions of the respiratory system where clear-ancemechanisms are less effective and lung inflammationcould occur.[41] The exact composition of this particulateis unknown, though it would likely be composed of largehydrocarbon molecules and a variety of adsorbed toxi-cants. Hence, inhalation exposures should be minimizedas much as possible.

While fireground concentrations were below anyapplicable occupational exposure limits, median particlecount, respirable mass, total PAH, and benzene concen-trations were above background levels and could con-tribute to a firefighter’s dose. Numerous other chemicalswill also be produced (e.g., aldehydes),[26] but were notmeasured in this study. Exposure to multiple chemicals(as is likely during fire responses) could have additiveor even synergistic health effects, especially if the chem-icals affect the same target organs. The toxicity of mix-tures is an area of active research and is not well under-stood. According to our findings, the magnitude of thefireground exposures will depend on the firefighters’ posi-tion relative to the wind direction and atmospheric con-ditions affecting the mixing/dilution of the smoke (e.g.,superadiabatic atmosphere resulting in fumigation). Dur-ing fire responses where ground level smoke is evident, itis prudent for firefighters to establish command upwindof the structure if possible and/or to wear respiratoryprotection.

In addition to the condensation losses of vapors inthe sample tubing, another limitation of this study wassampling pump faults due to the extreme conditionsand particulate loading onto the media. Several area andpersonal air samples only ran for a portion of the fireresponse (�4 min or �3 min, respectively). Thus, resultswith shorter sampling times likely better represent the

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growth phase of the fire and initial attack, which would beinfluenced more by peak smoke production levels, whileresults with longer sampling times would better representthe entire response (including post-suppression). Corre-lation analysis between the sample times and personal airconcentrations indicated—at least for some compoundsand positions—that air concentrations were highest dur-ing the first few minutes of the response. Also, many ofthe samples that were excluded (due to inadequate sampledurations)measured higher concentrations than themax-imum levels reported here. This is an important consid-eration, especially for acutely toxic compounds that haveIDLH levels or ceiling limits (e.g., HCN).

Conclusions

Personal and area air concentrations collected within thestructure during the fire period were well above short-term occupational exposure limits for most of the mea-sured compounds and exceeded the IDLH level for HCN.Firefighters performing outside ventilation were exposedto HCN concentrations near or above the IDLH level.Air concentrations of all measured compounds decreasedafter suppression; however, some personal air concentra-tions of PAHs and benzene measured from overhaul fire-fighters exceeded applicable exposure limits. Median fire-ground concentrations of benzene, total PAHs, and activeparticle surface area were above background levels andhighest when collected downwind of the structure withheavy ground-level smoke. Firefighters can protect them-selves from these inhalation exposures by wearing SCBAthroughout the entire response, including during over-haul and outside ventilation activities, as well as by estab-lishing command upwind of the structure. If the lattercannot be accomplished and ground level smoke is evi-dent, command/support personnel should wear respira-tory protection.

Acknowledgments

This was a collaborative project that could not have been com-pleted without the help from several people.We thank JonathanSlone, Kendra Broadwater, and Catherine Beaucham for theirhelp in collecting the area air samples, Matthew Dahm andDonald Booher for performing the personal airmonitoring, andKenneth Sparks for preparing and maintaining our samplingequipment. Most of all, we thank the firefighters for participat-ing in this study. Participants were compensated up to $599 toparticipate in this study. This study was approved by the Insti-tutional Review Boards at NIOSH and the University of Illinois.

Funding

This study was funded through a U.S. Department ofHomeland Security, Assistance to Firefighters Grant (EMW

-2013-FP-00766). This project was also made possible througha partnership with the CDC Foundation. The findings andconclusions in this paper are those of the authors and donot necessarily represent the views of NIOSH. Mention ofany company or product does not constitute endorsement byNIOSH.

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