Health Hazard Evaluation Report 2010-0156-3196 Page 1

Evaluation of Dermal Exposure to Polycyclic 

Aromatic Hydrocarbons in Fire Fighters 

Report No. 2010-0156-3196

December 2013

Kenneth W. Fent, PhD, CIH

Judith Eisenberg, MD, MS

Doug Evans, PhD 

Deborah Sammons

Shirley Robertson

Cindy Striley, PhD

John Snawder, PhD

Charles Mueller, MS

Vance Kochenderfer

Joachim Pleil, PhD

Matthew Stiegel, PhD

Gavin P. Horn, PhD

U.S. Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health
Page 2 Health Hazard Evaluation Report 2010-0156-3196

Contents

Highlights...............................................i

Abbreviations ..................................... iv

Introduction......................................... 1

Methods ............................................... 2

Results ................................................ 14

Discussion .......................................... 37

Conclusions........................................ 45

Recommendations for Protecting Fire 

Fighters .............................................. 46

Recommendations for Additional 

Research............................................. 47

Appendix A ........................................ 48

Appendix B......................................... 52

Appendix C......................................... 54

Appendix D ........................................ 58

Appendix E......................................... 62

Appendix F......................................... 67

References.......................................... 75

The employer is required to post a copy of this report for 30 days at or near the 

workplace(s) of affected employees. The employer must take steps to ensure 

that the posted report is not altered, defaced, or covered by other material.

The cover photo is a close-up image of sorbent tubes, which are used by the HHE 

Program to measure airborne exposures. This photo is an artistic representation that may 

not be related to this Health Hazard Evaluation. Photo by NIOSH.
Health Hazard Evaluation Report 2010-0156-3196 Page i

We found that PAHs and 

benzene entered fire fighters’ 

bodies even though they wore 

full protective ensembles 

during controlled burns. The 

biological levels we measured 

were generally comparable to 

levels in occupational groups 

with low exposures to these 

compounds. Fire fighters 

should wear full protective 

ensembles during all stages 

of a fire response and wash 

hands and shower soon 

afterwards. 

Highlights of this Evaluation

The Health Hazard Evaluation Program carried out a study at a fire service training facility to 

determine if airborne polycyclic aromatic hydrocarbons (PAHs) and other aromatic hydrocarbons 

generated during live fire training contaminate and pass through the skin of fire fighters. 

What We Did

● In each of two rounds, we evaluated three controlled structure burns (one per day). Five 

fire fighters participated in each burn. 

● We sampled PAHs, volatile organic compounds (VOCs), and particulate in air.

● We collected breath and urine samples before and after each burn. We analyzed the 

breath samples for aromatic hydrocarbons and the 

urine samples for PAH breakdown products. 

● We took wipe samples on fire fighters’ skin to 

measure PAH contamination before and right after 

each burn.

● We measured VOCs released from turnout gear 

before and after each burn.

● We tested the SCBA equipment to make sure it 

worked properly. 

What We Found

● We detected possible cancer-causing PAHs and 

VOCs in air. 

● Some PAH air levels were above occupational 

exposure limits during overhaul.

● All VOC air levels were below occupational 

exposure limits during overhaul.

● Some VOCs were released from the fire fighters’ gear after the fire response. The air 

levels of these compounds were well below occupational exposure limits. 

● The PAH levels on fire fighters’ necks were higher right after the burns than before. 

PAHs were not found on other areas of fire fighters’ skin.

● Levels of benzene, an aromatic hydrocarbon, in fire fighters’ breath were higher right 

after the burns than before. However, fire fighters did not have elevated levels of 

benzene breakdown products in their urine. 

● In the first round of our study, levels of PAH breakdown products were higher in urine 

samples collected 3 hours after the burns than in samples collected before the burns.

● The levels of PAHs and benzene in fire fighters’ bodies were similar to levels in 

occupational groups with low exposures to these compounds.
Page ii Health Hazard Evaluation Report 2010-0156-3196

What We Found (continued)

● Most fire fighters wore properly working SCBA. The PAHs and benzene likely entered 

their bodies through their skin. 

What We Recommend

● Require fire fighters to wear full protective ensembles, including SCBA, during knockdown 

and overhaul for all fire responses. Provide fire fighters with long hoods that are unlikely to 

come untucked.

● Provide as much natural ventilation as possible to burned structures before starting 

investigations.

● Remove SCBA and hood last when removing gear. Take off gear before entering a 

rehab area. 

● Store gear on the outside of the apparatus when riding back to the station.

● Wash hands immediately and shower as soon as possible after a fire response. 
Health Hazard Evaluation Report 2010-0156-3196 Page iii

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Page iv Health Hazard Evaluation Report 2010-0156-3196

Abbreviations

°F Degrees Fahrenheit

μg Microgram

μg/g Micrograms per gram

μg/L Micrograms per liter

μg/m2 Micrograms per square meter

μg/m3 Micrograms per cubic meter

μm Micrometer

μm2/cm3 Square micrometer per cubic centimeter

ACGIH® American Conference of Governmental Industrial Hygienists

BEI® Biological exposure index

CFR Code of Federal Regulations

EPA Environmental Protection Agency

ELISA Enzyme-linked immunosorbent assay

IARC International Agency for Research on Cancer

LOD Limit of detection

Lpm Liters per minute

Max Maximum

MDC Minimum detectable concentration

m2 Square meter

mg/m3 Milligrams per cubic meter

Min Minimum

mL Milliliters

MQC Minimum quantifiable concentration

ND Not detectable

NFPA National Fire Protection Association

NIOSH National Institute for Occupational Safety and Health

OEL Occupational exposure limit

OSHA Occupational Safety and Health Administration

PAH Polycyclic aromatic hydrocarbons

p/cm3 Particles per cubic centimeter

PEL Permissible exposure limit

PM10 Particulate matter < 10 μm in aerodynamic diameter

psi Pounds per square inch

REL Recommended exposure limit

SCBA Self-contained breathing apparatus

s-PMA s-Phenylmercapturic acid

STEL Short-term exposure limit

TLV® Threshold limit value

VOC Volatile organic compound
Health Hazard Evaluation Report 2010-0156-3196 Page 1

Introduction 

The 330,000 career fire fighters and 770,000 volunteer fire fighters in the United States 

[NFPA 2011] are potentially exposed to chemicals during fire suppression and overhaul. 

These chemicals may exist as vapors, gases, and particles. One group of chemicals, 

polycyclic aromatic hydrocarbons (PAHs), are products of incomplete combustion that 

can exist in particle and gas phases. Of the 18 PAHs that are commonly produced during 

fires, the International Agency for Research on Cancer (IARC) classified benzo[a]pyrene 

as carcinogenic to humans; dibenz[a,h]anthracene as probably carcinogenic to humans; 

and seven others (benz[a]anthracene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]

fluoranthene, chrysene, indeno[1,2,3-c,d]pyrene, and naphthalene) as possibly carcinogenic 

to humans [IARC 2002, 2010]. For this report, these nine specific PAHs will be termed 

“potential” carcinogens. Positive-pressure self-contained breathing apparatus (SCBA), when 

properly fitted, worn, and maintained, have the highest assigned protection factor (10,000) 

of any respirator [29 CFR 1910.134], and should virtually eliminate inhalation exposures to 

PAHs and other combustion products. However, it is unknown how well turnout gear protects 

fire fighters from dermal exposure to these compounds.

To date, only a few studies have explored dermal exposure and absorption of combustion 

products in fire fighters. Investigators at the Queensland Fire and Rescue Service studied 

the penetration of PAHs and other aromatic hydrocarbons into fire fighters’ laundered or 

new turnout gear during controlled structural fires by performing air sampling outside and 

inside the turnout gear [QFRS 2011a,b]. Although turnout gear provided some protection, 

investigators found detectable levels of PAHs and other aromatic hydrocarbons, including 

benzene and toluene, in the air under the turnout gear. Investigators also detected PAHs on a 

few skin patches on the arms and legs of the fire fighters. However, the sampling pumps used 

under turnout gear in these Queensland Fire and Rescue Service studies could have pulled 

contaminants into the gear. 

Laitinen et al. [2009] measured biomarkers of PAHs and benzene in fire fighters wearing full 

ensembles during training evolutions involving wood smoke. Post-exposure urine levels of 

1-hydroxypyrene (metabolite of PAHs), 1-naphthol (metabolite of PAHs), and muconic acid 

(metabolite of benzene) were higher than pre-exposure levels, and PAHs were found on the 

fire fighters’ hands [Laitinen et al. 2009]. In a similar study involving fire fighters under field 

conditions, post-exposure urine levels of 1-hydroxypyrene were elevated but muconic acid 

was not [Caux et al. 2002]. Dermal exposure was not measured in this study. Laitenen et al. 

[2009] and Caux et al. [2002] did not have strict control over when SCBA was removed. 

Furthermore, the turnout gear, hood, and gloves had not been laundered in either study. 

Therefore, inhalation exposures to environmental smoke from premature removal of SCBA

and transfer of PAHs from contaminated gear to the skin were possible in both studies. For 

these reasons, the studies described above were not able to assess the contribution of dermal 

exposure during fire fighting to the internal dose.

We received support for this study from the National Institute for Occupational Safety 

and Health (NIOSH) as part of its National Occupational Research Agenda activities. Our 
Page 2 Health Hazard Evaluation Report 2010-0156-3196

primary goal was to understand dermal exposure to PAHs in fire fighters wearing National 

Fire Protection Association (NFPA) 1971/1981 [NFPA 2007a,b] compliant protective 

ensembles for structural fires (turnout gear, hood, SCBA, helmet, gloves, and boots) and its 

contribution to the internal dose. We tested four main hypotheses: 

1. Structural fires generate particles containing PAHs, which, due to their size and 

composition, persist through the overhaul phase of the response. 

2. Fire fighters have dermal exposure to PAHs during structural fire responses. 

3. Absorption of PAHs and aromatic hydrocarbons through fire fighters’ skin contributes 

to the internal dose of PAHs and aromatic hydrocarbons. 

4. Contamination of turnout gear contributes to fire fighters’ dermal and inhalation 

exposures to combustion products (e.g., PAHs and volatile organic compounds 

[VOCs]). 

Methods 

Study Design 

This study was conducted at the Illinois Fire Service Institute in Urbana-Champaign, Illinois. 

The study protocol was approved by the NIOSH Institutional Review Board. Inclusion 

criteria for study participation included: 

1. Non-smoking – to avoid false positives from recreational tobacco use

2. Male – because the size of our study was too small to interpret gender differences

3. 45 years of age or younger – to reduce the likelihood of adverse cardiovascular events 

in participants, the risk for which is increased in fire fighters over the age of 45 [Geibe 

et al. 2008]

4. Fire fighters who had completed instructor level training in the Chicago Fire 

Department – to ensure a highly trained group of participants 

The study was performed over two rounds, which were 1 year apart. See Table 1 for a 

summary of the two rounds. Fifteen fire fighters participated in each round (five fire fighters 

each day). Twelve fire fighters from round 1 repeated the study during round 2. Each round 

consisted of three controlled structural burns (one burn each day). 

Participating fire fighters were instructed to avoid grilled food and second-hand tobacco 

smoke for 2 days prior to the study to control for non-occupational sources of PAH exposure. 

Participants wore laundered gloves, hoods, and turnout gear. The hoods for round 2 were 

brand new and slightly longer than the hoods for round 1. We tested the turnout gear before 

each burn to ensure that the gear had minimal PAH contamination. Participants did not 

remove their SCBA until overhaul was completed, and they were at least 100′ from the burn 

structure to ensure that any increase in internal PAH levels after the burn was the result of 

dermal rather than inhalation exposure. 
Health Hazard Evaluation Report 2010-0156-3196 Page 3

Table 1. Summary of the controlled burns for each round of the study

Round/fire scenario Day/Burn Participating 

fire fighters

Exposure times by response phase

(minutes)

Fire/

Entry

Knockdown Overhaul Total

1. Timber-framed structure, 

drywall interior, fire 

fighters were mostly 

stationary

1 5 10 1 4 15

2 5 11 3 16 30

3 5 15 7 7 29

2. Metal burn can, drywall 

interior, fire fighters 

were mobile and rotated 

positions (except for 

nozzle operator and 

company officer)

1 5 10 2 8 20

2 5 10 3 5 18

3 5 10 4 4 18

Burn Structures 

Round 1 controlled burns were performed in the Illinois Fire Service Institute arson 

laboratory’s timber-framed buildings (Figure 1). Round 2 controlled burns were performed 

in the Illinois Fire Service Institute arson laboratory’s burn can (intermodal metal container) 

(Figure 2). Walls and ceilings inside the structures were covered in 0.375′′ drywall, and the 

floors were overlaid with unfinished plywood. For these scenarios, one of the rooms was 

designated as the “target room,” where fire fighters observed the fire and, at the appropriate 

time, controlled and suppressed the fire. The other room was designated as the “burn room,” 

which contained the fuel package for each scenario. Although the burn can was set up with 

two burn rooms, only one burn room was used for each burn. The dimensions of the burn 

structures, burn rooms, and target rooms are provided in Figures 1 and 2. The fuel packages 

consisted of typical family room furniture (e.g., overstuffed chair, plastic wastebasket filled 

with newspapers, small book shelf, computer monitor, folding table, carpet, and padding) as 

shown in Figure 3. Thermocouples were installed in the burn and target rooms to monitor 

conditions for the study and participant safety. Type-K (chromel-alumel) thermocouples 

with factory welded beads were used in conjunction with an Omega Engineering OMDAQPRO-4300 digital data acquisition system that collected temperature data every second. 

During round 2 only, all fire fighters except for the nozzle operator and company officer 

rotated every 2 minutes among three stations: 

● A simulated search where they crawled from the open door to the wall of the burn room 

at a secondary-search pace

● A simulated ceiling pull station where fire fighters pulled on a pike pole attached to 

a spring

● A rest station where fire fighters knelt toward the back of the structure
Page 4 Health Hazard Evaluation Report 2010-0156-3196

Figure 1. Schematic showing the interior layout of the burn 

structure used in round 1. 

Figure 2. Schematic showing the interior layout of the burn structure used in round 2. 
Health Hazard Evaluation Report 2010-0156-3196 Page 5

Figure 3. Example of fuel package used for rounds 1 and 2. Photo by 

NIOSH. 

Controlled Burn Safety Precautions

Several steps were taken to ensure participant safety. Fire fighters walked through the 

building prior to ignition to familiarize themselves with the layout, fuel package, and 

safety procedures. The Illinois Fire Service Institute director of research acted as the 

interior safety officer. A second Illinois Fire Service Institute staff member acted as the 

exterior safety officer. A backup team (with a waterline) and trained emergency medical 

technicians were stationed outside of the burn building to assist with suppression, rescue, 

and emergency medical response if necessary. Using a road flare, the interior safety officer 

ignited newspapers stuffed into the wastebaskets to start each burn. The exterior safety officer 

monitored smoke production, timed the scenario, and radioed thermocouple temperatures to 

the interior safety officer. During the burns, fire fighters were always within 10′ of a doorway 

for rapid egress. The nozzle operator was equipped with a 1.75′′ hand waterline with ample 

flow rate for suppressing the fire. The senior fire fighter in each group was assigned the 

company officer role, which involved providing backup to the nozzle operator, monitoring 

the nozzle operator’s conditions, evaluating fire conditions in the room, and ensuring the 

safety of the other crew members. The nozzle operator applied water to the burn room if 

ceiling temperatures exceeded 800°F or the 4′ height temperatures exceeded 250°F. Water 

and sports drinks were provided to the fire fighters throughout the study to maintain their 

hydration and combat the effects of heat stress.
Page 6 Health Hazard Evaluation Report 2010-0156-3196

Measuring Exposures and Biomarkers

A summary of our methods is in Table 2. Samples were collected at the following times each 

day to measure changes in exposure levels over time: 

● Pre-exposure (~1 hour before the controlled burn) 

● Exposure (during the controlled burn) 

● Post-exposure (10–40 minutes after the controlled burn) 

● Three hours after the controlled burn

● Six hours after the controlled burn

Table 2. Summary of the personal exposure monitoring and biological monitoring methods

Type of monitoring Sampling period Analyte Analytical method

Exposure monitoring

Personal air Exposure Total PAHs

(gas and particle phase)

NIOSH Method 5506 

[NIOSH 2013]

Dermal exposure 

on arm and neck 

Pre and post-exposure Total PAHs

(sum of 6 PAHs)

NIOSH Method 5506 

[NIOSH 2013]

Dermal exposure 

on hand and face

Post-exposure Total PAHs

(sum of 6 PAHs)

Dermal exposure 

on scrotum 

Pre and post-exposure Total PAHs

(sum of 6 PAHs)

Biological monitoring

Urine Pre, post, 3-hour, and 

6-hour

PAHs and their 

metabolites

ELISA 

[Smith et al. 2011]

Pre, post, 3-hour, and 

6-hour

Benzene metabolite

(s-PMA)

Liquid 

chromatography/ 

tandem mass 

spectrometry

Pre, post, 3-hour, and 

6-hour

Creatinine Vitros Autoanalyzer

Pre, post, 3-hour, and 

6-hour

Cotinine Immulite 2000

Exhaled breath Pre, post, and 6-hour Aromatic hydrocarbons NIOSH Method 2549 

[NIOSH 2013]

Exhaled breath 

(duplicate)

Pre, post, and 6-hour Aromatic hydrocarbons 

and semivolatile PAHs

Gas chromatography/ 

mass spectrometry by 

EPA lab

[Sobus et al. 2008]

ELISA = Enzyme-linked immunosorbent assay

EPA = U.S. Environmental Protection Agency

s-PMA = s-Phenylmercapturic acid
Health Hazard Evaluation Report 2010-0156-3196 Page 7

Personal Air Sampling for Polycyclic Aromatic Hydrocarbons 

We conducted personal air sampling for PAHs from ignition to completion of overhaul. The 

sample results do not represent inhalation exposures because the fire fighters wore SCBA. 

We used an SKC aluminum cyclone to sample respirable particles and an in-line SKC XAD2 sorbent tube to sample vapors. We used 

SKC Airchek 2000 pumps to draw 2.5 

liters per minute (Lpm) of air through the 

sampling media. This flow rate provides a 

4-micrometer (μm) aerodynamic diameter 

cut-point for the cyclone. To prevent fire 

damage to the sampling train, we wrapped 

it in Nomex® (DuPont) flame-resistant 

material and replaced the cyclone’s plastic 

grit pot with a fabricated aluminum grit pot 

(Figure 4).

Of the 30 personal sampling pumps used 

in this study, 25 stopped working before 

the end of the exposure period (completion 

of overhaul). Therefore, the volume of 

air that we used to calculate personal air 

concentrations was based on the amount of 

time the pumps ran during the controlled 

burn (from ignition to the time when the 

pumps stopped working). This time was 5 

minutes or more for all but three samples. In 

addition, three samples, each collected during 

a different burn, were excluded because the 

sampling media became disconnected.

NIOSH Method 5506 [NIOSH 2013] was used to analyze all air and skin samples for PAHs. 

NIOSH methods 5506 and 5528 [NIOSH 2013] differentiate among 17 PAHs, including 

all the potentially carcinogenic PAHs mentioned in the introduction except benzo[j]

fluoranthene; in this report, we mostly provide results for total PAHs. The calculation for 

total PAHs accounts for all peaks in the PAH response region of the chromatogram for both 

the particulate and gas phase.

Sampling Polycyclic Aromatic Hydrocarbons on Skin 

We used wipe sampling to measure dermal exposure to PAHs on the forearms, hands, neck, 

face, and scrotum. Four to six sprays (~0.5 milliliters [mL] per spray) of corn oil, depending 

on the surface area of the skin site, were applied evenly to the skin and then wiped off using 

Texwipe® AlphaWipes® TX1004. For the scrotal wipe samples, nitrile gloves and wipes 

saturated with 1 mL of corn oil were given to the fire fighters with instructions on how to 

collect the samples. 

Figure 4. Fire fighter wearing a PAH sampler and 

respirable dust cyclone with fabricated aluminum grit 

pot wrapped in Nomex material. Photo by NIOSH. 
Page 8 Health Hazard Evaluation Report 2010-0156-3196

During round 1, we detected PAHs on the skin of fire fighters prior to the controlled burns. 

Therefore, for round 2, we gave the fire fighters wipes soaked in deionized water to clean 

their skin before any pre-exposure data collection. 

The corn oil used for the dermal wipe samples had a complex chemical matrix. When 

chromatography was done on the analyte from the media blanks (which contained the 

wipes saturated with 2 mL of corn oil), several peaks appeared on the chromatogram in 

the same region where the PAHs would typically appear. Because the calculation for total 

PAHs accounts for all peaks in the PAH response region of the chromatogram, we could 

not use total PAHs as a metric for the dermal wipe samples. Instead, we selected six PAHs 

(anthracene, benzo[a]pyrene, chrysene, fluoranthene, phenanthrene, and pyrene) to sum as 

a surrogate of the total PAHs. The PAHs we selected had the highest rates of detection and 

mostly appeared on the chromatogram in the region outside of the interfering peaks caused 

by the corn oil. They also corresponded with the PAHs for which the urine ELISA method 

had the greatest sensitivity. 

For round 2, the lab analyzed the dermal wipe samples in two batches. One batch had a much 

higher analytical limit of detection (LOD) for pyrene than the other. This higher LOD was 

caused by a single media blank that, for unknown reasons, contained a greater amount of 

pyrene. We corrected the analytical values below this higher LOD using the pyrene levels 

on the field blanks. For most of the samples, this correction resulted in levels that were not 

detectable (ND); pyrene values were below the lower LOD for the other batch. We included 

the pyrene results in this report because the ELISA method responds very strongly to pyrene 

and its metabolites in urine.

Dermal exposure levels of PAHs were standardized by the surface area of the skin collection 

site. The surface areas of the forearms (0.15 square meters [m2

]) and hands (0.11 m2) were 

based on data for adult males [EPA 2011]. We estimated surface areas of the face (0.068 m2

) 

and scrotum (0.054 m2

) by dividing the surface areas 

of the head (for the face) and hand (for the scrotum) by 

two. The surface area of the neck (0.042 m2

) assumed 

that the neck accounts for 2% of the total body surface 

area [Lund and Browder 1944], which is 2.1 m2

 for adult 

males 30 to 39 years of age [EPA 2011].

Measuring PAHs and other Aromatic Hydrocarbons 

in Exhaled Breath

To sample fire fighters’ breath, we instructed them to 

take a deep breath in and then forcefully exhale their 

entire breath into the Markes International Bio-VOCTM 

sampler (Figure 5). We then pushed the collected air 

through Markes Carbograph 2TD/Carbograph 1TD 

thermal desorption tubes using a plunger. Elevated levels 

of combustion products in breath indicate elevated serum 

levels from recent (unmetabolized) inhalation or dermal Figure 5. Participant exhaling into the 

Bio-VOC sampler. Photo by NIOSH. 
Health Hazard Evaluation Report 2010-0156-3196 Page 9

absorption of these compounds. Duplicate samples were collected and all were stored at −4°F 

until analysis. One set of samples was analyzed by a NIOSH lab for aromatic hydrocarbons 

(benzene and toluene); the other set of samples was analyzed by an EPA lab for aromatic 

hydrocarbons (benzene, toluene, ethyl benzene, xylene, and styrene) and semivolatile PAHs 

(naphthalene, anthracene, phenanthrene, fluoranthene, and pyrene). Our collaborations with 

the EPA lab began 1 year after round 1 had been completed. Therefore, the EPA lab analyzed 

round 1 breath samples about 1 year after collection and round 2 samples within a few 

months after collection. 

Sampling Urine for PAH and Benzene Metabolites 

We assessed biological uptake of PAHs by measuring PAH metabolites in the participants’ 

urine. We also measured creatinine, a marker of kidney function and hydration, and cotinine, 

a marker of nicotine exposure. The participants were given sterile 100 mL collection cups 

for their urine specimens (pre, post, 3-hour, and 6-hour collection). In the field, samples were 

stored on dry ice; upon arrival in the laboratories, samples were stored at −4oF for PAHs and 

at −112oF for cotinine and creatinine. The urine samples were analyzed by a NIOSH lab in 

accordance with the methods described below.

Polycyclic Aromatic Hydrocarbon Metabolites 

The urinary PAH-metabolite assay used a modified version of Strategic Diagnostics 

Incorporated PAH RaPID Assay® [Smith et al. 2011]. Briefly, urine samples diluted 

25% with methanol at collection were treated with the enzyme β-glucuronidase to cleave 

glucuronide conjugates of PAH metabolites. After treatment with β-glucuronidase, samples 

were diluted by 1/20 with kit diluent to diminish urine matrix effects and assayed according 

to the instructions. The concentrations were reported as phenanthrene kit equivalents 

corrected for a dilution factor of 28.8. 

Benzene Metabolite (s-Phenylmercapturic Acid) 

We added the analysis of urine samples for s-PMA to the study after detecting elevated postexposure levels of benzene in breath compared to the pre-exposure levels. Thus, the urine 

samples were not analyzed until 1 to 2 years after collection. These samples were analyzed 

by NMS Labs using an internal high performance liquid chromatography/tandem mass 

spectrometry method. Prior to analysis, 1 drop of 12 N hydrochloric acid was added to each 

5-mL urine sample aliquot. 

Creatinine

Creatinine was measured using a Johnson & Johnson Vitros Autoanalyzer with a Vitros 

CREA slide. Reported urinary PAH metabolite levels are normalized by creatinine 

(micrograms per gram [μg/g]).

Cotinine (Nicotine-N-oxide) 

Cotinine, a metabolite of nicotine, was measured in urine using a Diagnostic Products 

Corporation Immulite® 2000 analytical platform. Although we excluded current smokers 

from the study, analysis of cotinine levels was used to determine possible exposure to 

environmental tobacco smoke [Suwan-ampai et al. 2009]. 
Page 10 Health Hazard Evaluation Report 2010-0156-3196

Sampling Air Inside the Burn Structure

Table 3 provides a summary of the methods we used to measure particles and other 

combustion products inside the burn structures during the following phases: 

a) Fire phase is the time between ignition, buildup of the fire, and knockdown.

b) Knockdown phase is the period when fire fighters reduce flame and heat using water 

to a point where progression of the fire has been abated and overhaul can begin.

c) Overhaul phase starts when fire fighters begin to search for and suppress residual 

flames or smoldering materials and ends when the fire fighters leave the structure. The 

interior safety officer reported the start time for overhaul using his radio. 

d) Investigation phase, for this study, is the 1-hour period following overhaul. This 

period was chosen to represent the time when a cause and origin investigator could 

enter a structure to start his investigation. 

We measured background levels by sampling the air for approximately 1 hour before ignition. 

Table 3. Summary of the environmental (area) air monitoring within the burn structures

Analyte Instrument or media Analytical 

method

Sampling period

Direct-reading samples

Particle number 

concentration

TSI 3007 condensation 

particle counter*

NA Continuous monitoring 

before ignition, 

and during the fire, 

knockdown, overhaul, 

and investigation 

phases

Particle mass 

concentration

TSI DustTrakTM NA

Particle active

surface area

EcoChem DC2000

Diffusion Charger†

NA

Particle bound PAH 

concentration (qualitative)

EcoChem PAS2000 

Photoelectric Aerosol Sensor

NA

Substrate-collected samples

Particle-phase PAH

mass concentration by 

size distribution

8-stage impactor NIOSH 

Method 

5506

Integrated sampling 

before ignition, 

and during the 

fire (including 

knockdown), overhaul, 

and investigation 

phases

Total PAHs XAD-2 OVS sorbent tubes 

with built-in glass fiber filter

NIOSH 

Method 

5506

VOCs Evacuated 6-liter canister EPA Method 

TO-15

Monitoring Particles with Direct-reading Instruments

All direct-reading instruments were located on an aerosol sampling platform [Evans et 

al. 2010] that allowed simultaneous sampling of contaminant conditions within the burn 

structures through the progression of fires and response phases. We modified the platform 

using a flexible metallic duct and blower [Fent 2010; NIOSH 2010a] to draw contaminants 

to the instruments without the instruments being adversely affected by high temperatures or 

water spray within the structure. This area air sampling duct was used for the round 1 burns. 

No dilution air was used for burn 1; consequently, the instruments were rapidly overwhelmed 
Health Hazard Evaluation Report 2010-0156-3196 Page 11

by high particulate concentrations. Ambient air was used for dilution in burns 2 and 3 of round 

1. Approximate dilution factors of 7:1 (burn 2) and 27:1 (burn 3) were attained. We had varying 

dilution factors for round 1 because the airborne contaminant levels were initially unknown; 

therefore, dilution ratios and sampling configurations were adjusted each day.

A two-stage ejector dilution system (using compressed, filtered air) was used for the round 2 

burn measurements within the same structure for all fires. The first dilution stage used heated 

air to prevent artificial condensation of volatiles. Each dilution stage provided an 8:1 dilution, 

resulting in an overall 64:1 dilution while particle concentrations were sufficiently high (i.e., 

during the fire and knockdown phases of the burns). The sample inlet was closer to the fuel 

load during round 1 than round 2 because of the differences in the burn structures between 

rounds (Figures 1 and 2). Figure 6 shows the aerosol sampling platform used during round 2. 

The exterior safety officer was positioned near this platform for round 2.

Figure 6. Aerosol sampling platform used during round 2. Photo by NIOSH. 
Page 12 Health Hazard Evaluation Report 2010-0156-3196

Sampling Polycyclic Aromatic Hydrocarbons

We used SKC Aircheck 2000 pumps to draw air at 1 Lpm through SKC XAD-2 OVS sorbent 

tubes (with built-in glass fiber filters) to sample the air inside the burn structure for PAHs. 

For round 1, samples were collected from the area air sampling duct. Burn 1 samples were 

not diluted, and burn 2 samples were diluted by approximately 7:1. Burn 3 fire and overhaul 

samples were diluted by approximately 27:1. The background and investigation samples 

were collected inside the structure approximately 1′ above the floor. 

For round 2, the fire and overhaul samples were collected from the air sampling line of the 

ejector dilution system. The fire samples were diluted by 8:1 and the overhaul samples were 

not diluted. The background and investigation samples were collected inside the structure 

approximately 1′ above the floor. The laboratory extracted the samples in whole for analysis 

of PAHs regardless of their physical state (i.e., particulate or vapor).

To determine the particle size distribution of the PAHs (by mass) we used an MSP® 

Corporation 130 High Flow 8-Stage Impactor. The impaction plates were prepared with 

media (75-mm and 90-mm 2 μm pore polytetrafluoroethylene filters) using sterilized forceps 

and assembled in order. Before ignition, an impactor was connected to a Thomas VTE 

vacuum pump. A Magnehelic® pressure gauge was used to set and continuously monitor 

the inlet flow rate through the impactors at 100 Lpm. For round 1, the impactor inlet was 

positioned inside the area air sampling duct (and therefore sampled air that was diluted as 

previously described). For round 2, a copper sample line (0.75′′ diameter with 90° elbow 

wrapped in insulation) connected the inlet of the impactor to the structure interior. This 

connection point on the structure was directly below the area air sampling line (~4′ above 

the interior floor). After knockdown, the impactor was replaced with a second pre-loaded 

impactor. Air was drawn through this impactor until completion of overhaul. After sampling, 

the impactors were disassembled. Using sterilized forceps, the media was placed inside 

50-mL conical tubes for shipping to the analytical laboratory. Before being used again, the 

impactors were cleaned with cleaning solution, detergent, alcohol, and water. The o-rings 

were regreased with silicone-based lubricant.

Sampling Volatile Organic Compounds

During round 2 only, we used 6-liter evacuated canisters with particulate screens to sample 

the air inside the structure for VOCs. The evacuated canisters were operated with either 

15-minute or 1-hour regulators. The 15-minute regulators were used for collecting the 

controlled burn and overhaul air, while the 1-hour regulators were used for collecting the 

background and investigation air. Evacuated canister samples were collected from the same 

locations as the corresponding PAH area air samples and therefore have the same dilution 

factors. However, for burns 1 and 2, the evacuated canisters used to sample air during the fire 

and knockdown phases were connected to a sampling port that we later learned was not under 

positive pressure. Positive pressure is necessary to ensure accurate sampling. Therefore, 

the results of these samples are not provided. The evacuated canisters were analyzed for 64 

VOCs according to EPA Method TO-15 [EPA 1999]. 
Health Hazard Evaluation Report 2010-0156-3196 Page 13

Other Measurements and Data Collection 

Sampling Polycyclic Aromatic Hydrocarbons on Turnout Gear 

We collected surface samples of the interior of the turnout gear sleeves prior to the controlled 

burns to ensure that the laundered turnout gear was free of PAHs. Similar samples were 

collected after the controlled burn to investigate the post-exposure contamination of the 

turnout gear. We wore nitrile gloves and used Allegro® 70% isopropyl alcohol wipes to wipe 

the interior of the turnout gear sleeves, placed the wipes in amber glass vials, and had them 

analyzed for PAHs using NIOSH Method 5506 [NIOSH 2013].

Sampling Volatile Organic Compounds Off-gassing from Turnout Gear

During round 2 only, we performed experiments to determine the air concentration of 

contaminants off-gassing from turnout gear following a controlled burn. Two empty 6.4 ft3

PelicanTM transportation cases were vacuumed (high-efficiency particulate air filtration), 

cleaned with Allegro isopropyl alcohol wipes, and allowed to dry for > 20 hours. After 

drying, background air samples were collected by placing 6-liter evacuated canisters with 

15-minute regulators inside the cases, closing the lids, and opening the cases’ pressure 

release valves. Approximately 25 minutes after each controlled burn, the nozzle operator’s 

and company officer’s ensembles (except for SCBA) were placed inside the cases along with 

evacuated canisters to collect off-gas samples. The inlets of the canisters were positioned 

in the middle of the cases to minimize collecting outdoor air coming through the pressure 

release valves. Using the same method, we also investigated the off-gassing of a brand-new 

article of turnout gear. The evacuated canisters were analyzed for 64 VOCs according to EPA 

Method TO-15 [EPA 1999].

Testing Performance of Self-contained Breathing Apparatus

During round 2, we tested the SCBA following each burn using a Sperian Instrumentation 

PosiChek3 system. This machine simulates the effect of a human breathing on the SCBA 

to evaluate its performance characteristics. The machine’s dummy headform and bellows 

simulate breathing through a mouth opening. The SCBA facepiece is placed on the headform 

as it would be on a user’s head. The SCBA is attached as in normal use.

The major performance requirements for fire fighting SCBA are defined in the Department of 

Health and Human Services regulations for respiratory protective devices used by NIOSH for 

granting approval [42 CFR 84] and in NFPA 1981, a voluntary consensus standard developed 

by the NFPA [2007b]. The PosiChek3 is commonly used by fire departments and SCBA 

repair and service technicians to measure SCBA performance. However, it does not duplicate 

the laboratory test method in all aspects. Detailed descriptions of each test are given in 

Appendix A.

Administering a Questionnaire

During both rounds, fire fighters completed a questionnaire that asked for medical, work, 

and smoking history; personal protective equipment use during specific activities; garment 

history and laundering; personal and equipment hygiene after fires; use of over-the-counter 
Page 14 Health Hazard Evaluation Report 2010-0156-3196

personal care products that may contain PAHs; and frequency and last ingestion of foods that 

may contain PAHs. 

Statistical Analysis

We used SAS 9.1 statistical software for all data analysis. Because of varying parameters of 

the two rounds, round 1 and round 2 data were analyzed separately. ND levels (below the 

minimum detectable concentration [MDC]) were assigned values by dividing the MDC by 

the square-root of two. MDCs are the lowest concentration of an analyte that can be detected 

with a sampling method. We used the average volume of air sampled (or average other 

denominator such as surface area for wipe samples) to calculate the MDCs. The pre-exposure 

level of PAHs on the neck of one subject was excluded from analysis because it was more 

than 8 standard deviations above the mean of the pre- and post-exposure levels. The preexposure breath concentration of benzene measured by the EPA lab from one subject was 

excluded because it was more than 30 standard deviations above the mean of all other EPA 

pre-exposure benzene concentrations; moreover, the duplicate breath sample analyzed by the 

NIOSH lab was substantially lower. Three air samples were excluded because media became 

disconnected. No other personal exposure data were excluded. The number of NDs, MDCs, 

and minimum quantifiable concentrations (MQCs) for the personal variables with more than 

one ND value are given in Tables B1 and B2 in Appendix B.

We calculated the change in dermal exposures, urine concentrations, and exhaled breath 

concentrations over different time periods. Median values were reported as estimates of central 

tendency because some of the distributions were skewed. Because the assumption of normality 

was not met for many variables, we used nonparametric sign tests to explore changes in 

exposures or biomarkers. Nonparametric Spearman tests were used to explore correlations. 

Results

Personal Exposure and Biomarker Levels 

The median personal air concentrations of total PAHs are provided in Figure 7 by round and 

physical state and in Figure 8 by round and burn. The personal air concentrations of total 

PAHs were higher during round 1 (range = 750–22,000 micrograms per cubic meter [μg/

m3]) than round 2 (range = 61–2,200 μg/m3). During round 1, burn 1 resulted in the highest 

median personal air concentration of total PAHs. The respirable particle phase was the 

main contributor to the total PAHs. Figures 9 and 10 show the proportion of the potentially 

carcinogenic PAHs measured in the personal breathing zones for rounds 1 and 2, respectively. 

The proportions were similar between the two rounds with the potentially carcinogenic PAHs 

accounting for > 30% of the total PAHs measured.
Health Hazard Evaluation Report 2010-0156-3196 Page 15

Figure 7. Median personal air concentrations of PAHs by round of study and physical state. 

Figure 8. Median personal air concentrations of total PAHs by burn. 
Page 16 Health Hazard Evaluation Report 2010-0156-3196

Figure 9. Potentially carcinogenic PAHs and other PAHs (as a proportion of the total PAHs) measured in the 

personal breathing zones during the round 1 fires (n = 14). 

Figure 10. Potentially carcinogenic PAHs and other PAHs (as a proportion of the total PAHs) measured in the 

personal breathing zones during the round 2 fires (n = 13). 
Health Hazard Evaluation Report 2010-0156-3196 Page 17

Most of the dermal PAH levels were below their MDCs. The ranking of the median 

post exposure levels by anatomical site for both rounds were: neck > face > hand ≈ arm. 

The scrotum samples were collected differently and therefore were not included in this 

comparison. For skin sites where we collected pre- and post-exposure samples (i.e., neck, 

arm, and scrotum), the post-exposure skin levels of PAHs did not vary significantly from 

the pre-exposure levels except for the levels on the neck during round 1 (sign test P = 0.02). 

Some of the hoods worn during round 1, which were shorter than the hoods worn during 

round 2, became untucked from the turnout gear jacket during exercises. Because we found 

the highest post-exposure levels on the fire fighters’ necks, and these levels were significantly 

greater than the pre-exposure levels for round 1, the levels of PAHs measured on the fire 

fighters’ necks are summarized in Figure 11. Although the round 2 levels on the fire fighters’ 

necks appear higher than the round 1 levels, these levels are not directly comparable because 

of the varying MDCs between rounds and the high percentage of ND values (> 80% of the 

post-exposure data was ND; Table B2 in Appendix B). 

Figure 11. Pre- and post-exposure median dermal exposure levels of PAHs on the neck by round of study. 
Page 18 Health Hazard Evaluation Report 2010-0156-3196

Table 4 summarizes the exhaled breath concentrations of the aromatic hydrocarbons and 

semivolatile PAHs. Statistically significant differences in breath concentrations (postexposure compared to pre-exposure levels) are indicated in the table with an asterisk. On 

average, breath concentrations of aromatic hydrocarbons were elevated post-exposure, but 

then decreased at the subsequent 6-hour collection. Other than for naphthalene, this trend was 

not observed for the semivolatile PAHs. The post-exposure breath concentrations of aromatic 

hydrocarbons were higher during round 1 than round 2. Benzene was the predominant 

aromatic hydrocarbon measured in breath. We did not perform statistical comparisons 

between the NIOSH and EPA breath data (for benzene or toluene) because 40% or more of 

the post-exposure NIOSH measurements were ND (Table B1 in Appendix B), and the method 

used by the NIOSH lab had much higher MDCs than the method used by the EPA lab. All 

the breath measurements provided by the EPA lab (except for three anthracene results) were 

above their respective MDCs.
Health Hazard Evaluation Report 2010-0156-3196 Page 19

Table 4. Median exhaled breath concentrations (μg/m3) of aromatic hydrocarbons and semivolatile 

PAHs (EPA analytical results unless otherwise noted)

Analyte Round Pre

(n = 15)

Post

(n = 15)

6-hour

(n = 15)

MDC

Aromatic hydrocarbons

Benzene 1 3.8† 35* 20* 0.28

2 4.0 11* 5.5 0.28

Benzene (NIOSH data) 1 ND 300* 100* 100

2 35 ND ND 50

Toluene 1 2.9 11 5.4* 0.061

2 3.7 5.8 4.1 0.061

Toluene (NIOSH data) 1 ND 71 ND 100

2 ND ND ND 50

Ethyl benzene 1 0.72 1.9* 0.83 0.073

2 0.58 0.58 0.68 0.073

Xylene 1 3.5 14 6.2 0.12

2 4.1 7.4 4.5 0.12

Styrene 1 0.5 3.9* 0.86 0.049

2 0.5 1.6 0.69 0.049

Semivolatile PAHs

Napthalene 1 0.44 1.2* 0.61 0.05

2 0.66 0.69 0.51 0.05

Anthracene 1 0.35 0.24 0.24 0.049

2 0.23 0.2 0.17 0.049

Phenanthrene 1 0.68 0.44 0.61 0.18

2 0.72 0.57 0.53 0.18

Fluoranthene 1 0.74 0.63 0.57 0.042

2 0.49 0.47 0.49 0.042

Pyrene 1 0.81 0.66 0.64 0.023

2 0.47 0.46 0.49 0.023

*Significant increase (sign test P < 0.05) in levels compared to the pre-exposure levels

†Excludes 30 standard deviation outlier (n = 14)

Although we found a statistically significant difference between pre-exposure and postexposure benzene concentrations in exhaled breath, all urine concentrations of s-PMA

(a metabolite of benzene) were below the LOD of 5 micrograms per liter (μg/L). After 

correcting by the average creatinine level, the MDC was 8.5 μg/g creatinine. Therefore, 

on average, the biological uptake of benzene was below the American Conference of 

Governmental Industrial Hygienists (ACGIH®) Biological Exposure Index (BEI®) of 25 μg 

s-PMA/g creatinine. Appendix C provides more information on this BEI.
Page 20 Health Hazard Evaluation Report 2010-0156-3196

Figure 12 provides the median urinary PAH metabolite levels over time. Although the highest 

median urinary PAH metabolite levels were measured during the 3-hour collection period 

for both rounds, the temporal pattern is not consistent between rounds. The PAH metabolite 

levels in the 3-hour samples were not significantly greater than the pre-exposure levels for 

either round. However, for round 1, the PAH metabolite levels in the 3-hour samples were 

significantly greater (sign test P = 0.04) than the post-exposure levels. Overall, urinary PAH 

metabolite levels were higher during round 1 than round 2.

Correlations between Exposure and Biomarker Measurements

Our hypothesis was that increasing PAH air concentrations and dermal exposures would 

correlate with increasing urine concentrations of PAH metabolites following the exposure 

period. Benzene was the predominant aromatic hydrocarbon measured in the breath with 

a statistically significant change over time. We did not, however, measure benzene in air. 

Because benzene and PAHs are products of combustion and therefore could be related 

to each other, we also hypothesized that benzene in breath could correlate with the PAH 

exposure and biomarker variables. We selected five variables to further explore relationships 

using correlation and regression analysis. These variables are summarized in Table 5. These 

variables represent changes in levels from the pre-exposure collection period (estimate 

of baseline) to another collection period (e.g., post-exposure), except for the personal air 

concentrations of PAHs. In most cases, these changes represent the greatest increase or peak 

in exposure or biomarker levels measured during the study. We included exhaled breath 

variables calculated using both the EPA and NIOSH benzene data. 

Figure 12. Median urinary PAH metabolite levels by round and collection period during the study. 
Health Hazard Evaluation Report 2010-0156-3196 Page 21

Table 5. Descriptive statistics for the five exposure and biomarker variables that we selected to 

explore further

Variables Units Round N No. of

ND 

values*

Median Min Max Sign 

test P

value†

Personal air concentration of 

PAHs

μg/m3 1 14 0 4,700 750 22,000 NA

2 13 0 1,200 61 2,200 NA

Change in PAH levels on the 

neck

(post minus pre)

μg/m2 1 15 5 12 −2.8 150 0.02

2 14 3 11 −38 61 0.07

Change in exhaled breath 

concentrations of benzene 

(post minus pre; NIOSH data)

μg/m3 1 15 6 230 0 550 < 0.01

2 15 14 0 −65 0 > 0.99

Change in exhaled breath 

concentrations of benzene 

(post minus pre; EPA data)

μg/m3 1 14 0 34 −11 340 0.01

2 15 0 7.4 −10 29 0.04

Change in urinary PAH 

metabolite levels

(3-hour minus pre)

μg/g 1 15 0 17 −61 53 0.12

2 15 1 −2.1 −100 67 > 0.99

Min = minimum

Max = maximum

μg/m2 = micrograms per square meter

*Value counted as ND if all analytical data used to calculate the value were ND (see Appendix B for 

more details).

†For all significant changes (sign test P < 0.05), the number of positive differences was greater than 

the number of negative differences.

We explored the correlations between outcome variables (biomarker levels) and explanatory 

variables (personal exposure levels) among the five variables we selected (Table 6). Although 

exhaled breath is technically a biomarker, we also assessed its utility as an explanatory 

variable because it may represent recent exposures. We found statistically significant 

correlations between several variables using the nonparametric Spearman test. Some 

variables were correlated during one round but not the other. The different data used for the 

exhaled breath variables (NIOSH versus EPA analysis) affected the correlations. However, 

the correlations involving the round 1 NIOSH breath data should be interpreted cautiously 

because 40% of the measurements were ND. Because the face was the second most exposed 

body part, we also explored the correlations between the change in PAH levels on the face 

(post minus pre) and the change in urinary PAH metabolite levels (3-hour minus pre) for each 

round, but these correlations were not statistically significant (data not shown).
Page 22 Health Hazard Evaluation Report 2010-0156-3196

Table 6. Correlations between outcome and explanatory variables

Outcome variable Explanatory variable Round No. of 

samples

Spearman

r P value

Change of benzene in 

breath (post minus pre; 

EPA data)

Personal air concentration of PAHs 1 13 0.29 0.33

2 13 0.74 < 0.01

Change of benzene in 

breath (post minus pre; 

NIOSH data)*

Personal air concentration of PAHs 1 14 0.49 0.08

Change in urinary PAH 

metabolite levels

(3-hour minus pre)

Personal air concentration of PAHs 1 14 0.70 < 0.01

2 13 0.16 0.60

Change in urinary PAH 

metabolite levels

(3-hour minus pre)

Change of PAHs on the neck

(post minus pre)

1 15 0.43 0.11

2 14 0.63 0.02

Change in urinary PAH 

metabolite levels

(3-hour minus pre)

Change of benzene in breath

(post minus pre; EPA data)

1 14 0.44 0.12

2 15 0.38 0.17

Change in urinary PAH 

metabolite levels

(3-hour minus pre)

Change of benzene in breath

(post minus pre; NIOSH data)*

1 15 0.69 < 0.01

*Most NIOSH breath data for round 2 were ND and therefore were excluded from the correlation 

analysis.

Figures D1–D4 in Appendix D show the linear regression plots for the significantly 

correlated variables in Table 6. The majority of the fire fighters (23 of 30) had urinary 

cotinine concentrations below 30 μg/L. A cotinine level above 30 μg/L has been associated 

with light tobacco smoking and passive exposure to tobacco smoke, which are both sources 

of PAH exposure (confounders) [Wall et al. 1988]. Therefore, data from subjects with 

cotinine levels > 30 μg/L are identified in these plots. 

Environmental Monitoring Inside the Structure 

The burn room and target room temperature profiles for each burn are provided in Figures 

E1–E9 of Appendix E. A greater number of thermocouples were used for the round 2 burns. 

Temperatures within 20′′ of the ceiling exceeded 1200°F in the burn room and exceeded 

400°F in the target room for all the burns. As expected, temperatures decreased with 

increasing distance from the ceiling. Temperatures within 24′′ of the floor were < 200°F for 

all the burns. All temperatures dropped below 200°F within a few minutes after the fire was 

suppressed. Figure 13 provides a thermal image of smoke exiting the structure of a round 1 

fire. This figure shows the boundary layer of smoke and heat toward the ceiling and relatively 

cooler air toward the bottom of the structure. Fire fighters spent time standing and crouching 

during both rounds; however, the round 2 fire fighters most likely spent a greater proportion 

of their time below the boundary layer from doing simulated fire fighting activities.
Health Hazard Evaluation Report 2010-0156-3196 Page 23

Figure 14 summarizes 

the concentration of total 

PAHs in area air samples 

taken in the structure 

during the different phases 

of the response. The PAH 

concentrations were higher 

during the round 1 fires than 

the round 2 fires. However, 

the sampling inlet was closer 

to the fuel package in round 

1 than round 2. Background 

levels were low, ranging 

from ND (< 11 μg/m3) to 

240 μg/m3. As expected, 

PAH concentrations were 

highest during the fire and 

knockdown phases and dropped quickly during the subsequent overhaul and investigation 

phases. The overhaul concentrations were 7–280 times higher than the background 

concentrations for all the burns. For the burns 1 and 3 of round 1, the investigation 

concentrations were 7–11 times higher than the background concentrations. The proportion 

of potentially carcinogenic PAHs in the fire atmospheres for rounds 1 and 2 are provided 

in Figures 15 and 16, respectively. The proportion of potentially carcinogenic PAHs was 

higher during the round 1 fires (56%) than the round 2 fires (17%). Naphthalene was the 

predominant potentially carcinogenic PAH measured in round 1. 

Fire fighters commonly remove SCBA during overhaul and investigation. Therefore, it 

is appropriate to compare air concentrations measured during these phases to short-term 

occupational exposure limits (OELs). The air concentrations of total PAHs during overhaul 

for burn 2 (2,600 μg/m3) and burn 3 (6,000 μg/m3) of round 1 were well above the ACGIH 

excursion limit for coal tar pitch volatiles (1,000 μg/m3) [ACGIH 2013]. However, all the 

air concentrations of total PAHs measured during the investigation phases were below this 

excursion limit. Appendix C provides more information on this excursion limit and other 

short-term OELs.

Figure 13. Thermal image of a round 1 fire showing the smoke layer 

and elevated temperatures toward the ceiling of the structure. 
Page 24 Health Hazard Evaluation Report 2010-0156-3196

Figure 14. Air concentration of total PAHs (includes gas and particle phase) inside the structure by the 

response phase. 

Figure 15. Potentially carcinogenic PAHs and other PAHs (as a proportion of the total PAHs) measured in the 

structure during the round 1 fires (n = 3). 
Health Hazard Evaluation Report 2010-0156-3196 Page 25

Figures 17 and 18 summarize the mass concentration of the PAH particles in the structure 

by their aerodynamic diameter for each of the round 1 and round 2 fires, respectively. The 

PAH particle concentrations during the fires ranged from 35 to 62,000 μg/m3 and were much 

higher during round 1 than round 2. However, the sampling inlet was closer to the fuel 

package in round 1 than round 2. On a mass basis, the majority of the particles were between 

0.77 and 2.5 μm in aerodynamic diameter for all fires. 

Figure 16. Potentially carcinogenic PAHs and other PAHs (as a proportion of the total PAHs) 

measured in the structure during the round 2 fires (n = 3). 
Page 26 Health Hazard Evaluation Report 2010-0156-3196

Figure 17. Air concentration of total particulate PAHs by aerodynamic diameter for the round 1 fires. 

Figure 18. Air concentration of total particulate PAHs by aerodynamic diameter for the round 2 fires. 
Health Hazard Evaluation Report 2010-0156-3196 Page 27

The PAH particle concentrations during overhaul for round 1 (Figure 19) and round 2 (Figure 

20) were much lower than during the fires. As with the fires, the PAH particle concentrations 

during overhaul (ranging from 34 to 1,100 μg/m3) were higher during round 1 than round 

2. However, the sampling inlet was closer to the fuel package in round 1 than round 2. The 

maximum PAH particle concentration measured during overhaul (round 1 burn 3) exceeded 

the ACGIH excursion limit of 1,000 μg/m3 for coal tar pitch volatiles [ACGIH 2013].

Figure 19. Air concentration of total particulate PAHs by aerodynamic diameter for the round 1 

overhaul. 
Page 28 Health Hazard Evaluation Report 2010-0156-3196

Figure 20. Air concentration of total particulate PAHs by aerodynamic diameter for the round 2 

overhaul. 

The proportions of potentially carcinogenic particle-phase PAHs in the fire atmospheres 

for rounds 1 and 2 are provided in Figures 21 and 22, respectively. The ratio of potentially 

carcinogenic PAHs to the total were roughly the same between the rounds (i.e., 18% to 19%).
Health Hazard Evaluation Report 2010-0156-3196 Page 29

Figure 21. Potentially carcinogenic PAHs and other PAHs (as a proportion of the total 

particulate PAHs) measured in the structure during the round 1 fires (n = 3). 

Figure 22. Potentially carcinogenic PAHs and other PAHs (as a proportion of the total particulate 

PAHs) measured in the structure during the round 2 fires (n = 3). 
Page 30 Health Hazard Evaluation Report 2010-0156-3196

Figure 23 presents the air concentrations of the ten most abundant VOCs (relative to their 

short-term OELs) in the structure during the fire and knockdown phases of burn 3 of round 2. 

The benzene concentration (95,000 μg/m3) during this fire was an order of magnitude higher 

than the concentrations of the other VOCs and nearly 30 times greater than the NIOSH 

short-term exposure limit (STEL) [NIOSH 2010b], which is the most protective exposure 

limit. Because of a sampling error, we could not determine the VOC air concentrations 

during the fire and knockdown periods of the other round 2 burns. However, we were 

able to determine the VOC concentrations during background, overhaul, and investigation 

phases for the round 2 burns (Figure 24). In general, air concentrations were higher 

during overhaul than background or investigation phases. Benzene, styrene, and toluene 

concentrations were generally higher than the air concentrations of the other VOCs. Because 

fire fighters commonly remove SCBA during overhaul and investigations, we compared these 

concentrations to their applicable STELs. All concentrations of these VOCs were well below 

their STELs. Using the ACGIH additive mixture formula [ACGIH 2013], all hazard indices 

(summation of VOC exposures) were below acceptable limits (data not shown). Appendix C 

provides more information on OELs, including a table of applicable STELs, ceiling limits, 

and excursion limits for the compounds we measured in air.

Figure 23. Air concentration of ten VOCs in the structure during the fire and knockdown phases of burn 3 

of round 2. 
Health Hazard Evaluation Report 2010-0156-3196 Page 31

Figure 24. Median air concentrations of ten VOCs in the structure during the background collection 

period and the overhaul and investigation phases for round 2 (n = 3, error bars represent the maximum 

value). 

No dilution air was used for the direct-reading particle measurements during burn 1 of round 

1. We do not present these results because the undiluted particle levels rapidly overwhelmed 

the instruments. However, ambient dilution air was used for the direct-reading particle 

measurements during burns 2 and 3 of round 1. These results were adjusted by dilution 

factors and are provided in Figures F1–F4 of Appendix F by the fire response phase. The 

ambient dilution air could have been contaminated by particulate escaping the structure and 

drawn into the ambient air sampling system. This would mainly bias the fire measurements, 

causing a possible overestimation of the particle levels during the fires. However, such 

instances would have been of short duration. The contribution of outdoor background 

particulate to indoor particle concentrations, as they approached outdoor levels, was also an 

issue with this fixed dilution arrangement. 

We used filtered compressed dilution air for the direct-reading particle measurements 

during round 2. The sampling inlet for round 2 was located further away from the fuel load 

(inside the target room) than the sampling inlet for round 1. The round 2 direct-reading 

particle measurement results were adjusted by the dilution factor (64:1) when dilution air 

was used and are provided in Figures F5–F10 of Appendix F by the response phase. Table 7 

summarizes the round 2 results. We provide a summary of the round 2 results only because 

we used a more sophisticated dilution system during this round and therefore have greater 
Page 32 Health Hazard Evaluation Report 2010-0156-3196

confidence in these measurements. We measured the highest levels of number concentrations, 

mass concentrations, active surface area, and photoelectric response during the fire phase 

of the burns. Because the particulate levels exceeded the maximum ranges for some of 

our instruments (e.g. condensation particle counter) during the fire phase of the burns, the 

average levels reported for the fires may be underestimated. In general, these levels remained 

elevated compared to background levels through the overhaul phase of each burn. Compared 

to background levels, we measured elevated number concentrations, mass concentrations, 

and active surface area during the investigation phase of burn 3. However, some materials 

were still smoldering during the investigation phase of this burn, which would have 

contributed to these particle measurements.

Table 7. Mean direct-reading particle measurements for each phase of the responses during the 

round 2 burns

Analyte Burn Background Fire Knockdown Overhaul Investigation

Number (p/cm3) 1 6,400 11,175,700 3,479,100 31,800 4,076

2 52,900 15,347,000 5,798,700 10,190 37,700

3 9,100 17,100,800 8,095,100 236,800 145,400

PM10 mass (mg/m3) 2 0.059 201 26 6 0.08

3 0.044 475 25 12 0.70

Active surface area

(μm2/cm3)

1 21 70,821 4,766 342 19

2 31 90,514 9,289 50 21

3 11 45,848 1,368 10 43

Photoelectric 

response

(arbitrary units)

1 4.7 17,301 7,827 0.5 2.5

2 52 15,128 2,918 4.2 2.6

3 63 8,048 3,742 0 3.5

μm2/cm3 = square micrometer per cubic centimeter

mg/m3 = milligrams per cubic meter

p/cm3 = particles per cubic centimeter

PM10 = particulate matter < 10 μm in aerodynamic diameter 

Polycyclic Aromatic Hydrocarbons on Turnout Gear

Table 8 summarizes the PAH levels measured on the gear. Differences between the pre- and 

post-exposure total PAH levels on the inside of turnout gear sleeves were not statistically 

significant. Although the round 1 levels appear higher than the round 2 levels, these levels 

are not directly comparable due to the varying MDCs between rounds and high percentage of 

ND values (> 50% of the post-exposure data was ND; Table B2 in Appendix B). Although we 

collected fewer samples from the exterior of the gear, we measured much higher post-exposure 

PAH levels on the exterior of the helmets, respirators, and pants as compared to the interior 

of the sleeves. We also measured much higher pre-exposure PAH levels on the exterior of the 

helmets. The helmets were not required to be cleaned before being used in the study.
Health Hazard Evaluation Report 2010-0156-3196 Page 33

Table 8. Pre- and post-exposure levels of PAHs (micrograms [μg]) on fire fighter gear

Sample location Round Exposure 

period

No. of 

samples

Median Min Max

Interior of sleeves* 1 Pre 15 2.5 ND 3.6

Post 15 1.9 ND 4.4

2 Pre 15 1.2 0.47 3.7

Post 15 0.61 ND 4.5

Exterior of helmet 1 Pre 2 100 8.2 190

2 Post 4 15 5.9 23

Exterior of pants 1 Post 1 27 NA NA

Exterior of respirator 2 Post 2 4.8 3.3 6.3

*Differences between pre- and post-exposure total PAH levels were not statistically significant.

Off-gassing of Volatile Organic Compounds from Turnout Gear 

Figure 25 summarizes the most abundant VOCs that were off-gassing from the turnout gear 

for the round 2 burns. All of these VOCs were well below applicable short-term OELs for all 

the burns. Appendix C provides more information on the applicable short-term OELs. The 

median VOC air concentrations were higher after the burn than before the burn, except for 

4-methyl-2-pentanone. The highest concentration of dichlorobenzene was found off-gassing 

from a brand-new article of turnout gear.

Figure 25. Median air concentrations of ten VOCs off-gassing from new turnout gear (n = 1) and 

turnout gear worn by fire fighters in the round 2 burns (n = 6, error bars represent the maximum 

value). 
Page 34 Health Hazard Evaluation Report 2010-0156-3196

Self-contained Breathing Apparatus Performance

The SCBA used during round 2 included backframes and cylinders owned by the Chicago 

Fire Department, and each fire fighter brought the facepiece normally assigned to him 

for work. Each backframe and cylinder was visually examined prior to the burns, and 

any exhibiting obvious problems were not used. In addition, the facepieces were visually 

inspected before each burn. We identified damage or potential problems, such as missing 

inhalation or exhalation valve components, on 5 of the 15 facepieces; these fire fighters were 

given acceptable substitutes of the appropriate size to wear for the burn.

After each burn, each SCBA was tested on the PosiChek3. The pressure gauge test, alarm 

accuracy test, and redundant alarm accuracy test were only performed after burn 1 of round 2 

because the values for these tests are independent of the facepiece being used.

The test results are presented in Tables A1–A3 in Appendix A. Of the tests performed, the 

most important to this study are the two breathing tests and the facepiece leakage test. All 

but three of the SCBA passed the facepiece leakage test and all but one of the SCBA passed 

the breathing tests. A positive-pressure SCBA is designed to operate so the pressure inside 

the facepiece is always higher than the surrounding air. The intent is that if there is poor 

facepiece fit or slippage, any resulting leakage will be of clean air outward, not contaminated 

air inward. The breathing tests indicate whether the SCBA is capable of maintaining positive 

pressure. The facepiece leakage test is an indicator of any leaks that could potentially 

allow contaminants to enter if positive pressure is not maintained. An SCBA that meets the 

requirements of these three tests should provide protection against chemical exposure via 

the inhalation route. Should an SCBA not be capable of maintaining positive pressure during 

use, it should still provide protection so long as the facepiece seal is maintained, although the 

degree of protection is reduced. 

Questionnaire Results

Table 9 summarizes the demographics of our study population. The demographics were 

similar between the two rounds. However, the time since last fire suppression was greater and 

more variable for round 2. 

Table 9. Summary of the study population demographics

Round 1

n = 15

Round 2

n = 15*

Mean Min Max Mean Min Max

Age (years) 38 36 41 39 36 42

Height (inches) 71 66 76 72 67 76

Weight (pounds) 207 150 265 211 175 245

Time as fire fighter (years) 15 8 21 15 9 21

Time as Chicago fire fighter (years) 11 4 15 12 5 15

Time since last fire suppression (days) 7 2 30 48 1 365

Age of gear worn during study (years) 3.8 1.3 4 4.9 4 5

*Includes 12 fire fighters who also participated in round 1.
Health Hazard Evaluation Report 2010-0156-3196 Page 35

Table 10 provides the percentage of fire fighters from rounds 1 and 2 who reported typically 

wearing specific types of personal protective equipment for different fire responses. Most 

participants reported wearing standard ensemble gear (i.e., turnout gear jacket and pants, 

boots, SCBA, helmet, hood, and gloves) during structural knockdown. However, use of 

SCBA was 60% or less for all the other fire responses. 

Table 10. Frequency of participating fire fighters who reported wearing specific types of personal 

protective equipment by phase of fire responses

Structural 

knockdown

Structural 

overhaul

Roof 

ventilation

Vehicle fire 

knockdown

Vehicle fire 

overhaul

Vegetation 

fires

Round 1 2 1 2 1 2 1 2 1 2 1 2

n = 15 15 15 15 15 15 15 15 15 15 12* 15

Turnout 

jacket/pants

15 15 15 15 15 15 15 15 15 15 11 11

Boots 15 15 15 15 15 15 15 15 15 15 11 12

SCBA 15 15 6 9 2 1 4 5 3 5 0 1

Helmet 15 15 14 15 14 14 15 15 13 15 6 12

Hood 14 14 9 11 11 12 9 11 8 11 3 8

Ensemble 

gloves

14 15 14 15 14 15 13 15 13 15 8 11

Work gloves 3 5 3 6 4 6 4 6 4 7 2 5

Eye or face 

protection 

other than 

SCBA

2 2 2 1 1 0 1 0 2 1 0 0

*Three fire fighters responded that they never fight vegetation fires.

Most participants reported wearing SCBA during overhaul or salvage (Table 11). The 

participants who reported wearing SCBA wore it 36%–53% of the time. More than half of the 

participants (one declined to answer) reported removing SCBA during overhaul or salvage 

because the mask was hot or uncomfortable, or the tank was heavy. However, seven of them 

wrote in the free-text field that they did not remove their SCBA until the incident commander 

said it was safe to do so.

Table 11. Summary of SCBA use during salvage and overhaul (n = 15)

Round 1 Round 2

Yes No If yes, average 

percent of time worn Yes No If yes, average percent of time worn

During salvage 10 5 36 10 5 50

During overhaul 13 2 40 11 4 53
Page 36 Health Hazard Evaluation Report 2010-0156-3196

The participants reported laundering their turnout gear, on average, 1.4 times per year 

(ranging from 1 to 3 years), and 93% of them had their gear collected by an outside vendor 

for laundering off-premises. When asked if they had ever laundered their gear outside the 

regular schedule due to contamination, 37% said yes. These findings were similar between 

the two rounds. When asked if they had ever retired their gear due to contamination, 20% 

of the round 1 participants said yes, and 40% of the round 2 participants said yes. All 

participants reported seeing soot on their skin at one time or another when removing their 

gear. The most common places to find soot were the face, neck, and hands, with > 80% of the 

participants reporting soot on each of those locations. More than half of the participants also 

reported finding soot on their arms.

Table 12 provides the percentage of fire fighters who reported storing their gear in different 

locations. The most common place to store their gear was at the fire station in the gear 

storage area. However, 33% of the participants reported storing their gear (on occasion) in 

the fire apparatus and 47% in personal vehicles.

Table 12. Frequency of participating fire fighters who store 

their gear by location

Round 1

n = 15

Round 2

n = 15

At the fire station in the gear 

storage area

14 13

At the fire station in living areas 0 0

In the fire apparatus 6 4

In my personal vehicle 8 6

In my home 0 1

In my garage 2 1

Table 13 gives the frequency of possible confounders (i.e., consumption of chargrilled foods, 

use of personal care products that may contain PAHs such as dandruff shampoos and shaving 

cream) and effect modifiers (i.e., showering after fire suppression and history of smoking) 

for PAH exposure. All participants reported typically showering after fire suppression, 

which would likely minimize dermal absorption of PAHs on skin. However, fire fighters in 

this study did not shower until nearly 6 hours after suppressing the controlled burns. Most 

participants reported using shaving cream, moisturizer or lotions, and eating chargrilled 

foods in the last 7 days prior to the study. These results suggest that the participants could 

have been exposed to PAHs by sources other than the controlled burns. However, we did 

not explore the contribution of these other sources to the biomarker measurements because 

the amount of PAHs in the products used or foods ingested may vary substantially and PAH 

exposures a few days before study participation are most critical but could not be determined 

based on the information we collected.
Health Hazard Evaluation Report 2010-0156-3196 Page 37

Table 13. Summary of possible confounders and effect modifiers reported by the participating fire 

fighters (n = 15)

Round 1 Round 2

Yes No Yes No Don’t know¶

Former smoker* 2 13 2 13 NA

Typically shower after fire suppression 15 0 15 0 NA

Used shampoos for dandruff or psoriasis

(in last 7 days)† 

4 11 2 11 2

Used shaving cream, moisturizers, or lotions

(in last 7 days)‡ 

15 0 9 2 4

Ate chargrilled foods (in last 7 days)§ 9 6 14 1 NA

*None of the participants reported being “current smokers.”

†On round 1, we specifically asked if they had used coal-tar containing hair-care items, such 

as dandruff or psoriasis shampoos. On round 2, we simply asked if they had used dandruff or 

psoriasis shampoos.

‡On round 1, we specifically asked if they had used personal-care items containing mineral 

oil, paraffin, or petroleum jelly, such as shaving cream, moisturizers, or lotions. On round 2, we 

simply asked if they had used shaving cream, moisturizers, or lotions.

§On round 1, we asked if they had eaten grilled meat, vegetables, or other grilled food. On round 

2, we specifically asked if they had eaten food that could have been burned by grilling, pan- or 

stir-frying, toasting, or smoking.

¶“Don’t know,” was not an option for the round 1 questions.

Discussion 

In this study, we evaluated body burdens of PAHs and other aromatic hydrocarbons among 

fire fighters wearing full ensembles during live-fire training. Because of the study conditions 

and requirements, we believe that our findings solely reflect dermal exposure to airborne 

combustion byproducts. As a pilot study, we had a small number of participants in each 

testing round, which resulted in limited but sufficient statistical power to test our main 

hypothesis that fire fighters’ exposure to PAHs during fire suppression results in biological 

uptake via the dermal route.

Exposures and Biomarkers 

Because the fire fighters wore SCBA during the entire fire response, the personal air 

concentrations likely represent the air concentrations of PAHs that surrounded the fire 

fighters’ head and upper torso during the exercises and not the contents of the air they were 

breathing. Most of the personal air sampling pumps faulted before completion of overhaul, 

most likely from excessive back-pressure related to the overloading of the sample filters. 

Therefore, the personal air samples collected a sample of the air during its most contaminated 

period before knockdown. The temperature of the air that was sampled exceeded the upper 

operating range (113°F) of the sampling pumps, which could have affected their suction 
Page 38 Health Hazard Evaluation Report 2010-0156-3196

efficiency. The pump faults and pump performances at higher temperatures could result in 

either underestimation or overestimation of the actual PAH concentrations. 

The personal air concentrations of total PAHs (ranging from 61 to 22,000 μg/m3) were 

lower than the area air concentrations of total PAHs (ranging from 410 to 75,000 μg/m3) 

and total particle-phase PAHs (ranging from 35 to 62,000 μg/m3) measured during the fire 

and knockdown phases of all burns. This finding is to be expected because fire fighters take 

actions to avoid heat and smoke, such as crouching below the smoke layer. However, the 

differences between the area air concentrations and the personal air concentrations were 

much more pronounced during the round 1 fires (i.e., by a factor of 32). These dramatic 

differences were most likely due to the area air sampling inlet being located closer to the burn 

room during round 1 than round 2 (Figures 1 and 2). The possibility also exists that the round 

1 fire conditions (e.g., fuel packages, fire temperatures, and ventilation conditions) were 

more optimal for producing PAHs than the round 2 fire conditions. The higher personal air 

concentrations of PAHs measured during round 1 could also be due to varying work practices 

and behaviors. 

According to the personal air sampling results, the PAHs existed primarily as respirable 

particles. Respirable particles are the mass fraction of particulate that can penetrate deeply 

into the lower respiratory system [ACGIH 2013]. The respirable fraction is characterized by a 

cumulative log-normal curve having a median aerodynamic diameter of 4 μm and a standard 

deviation of 2 μm [NLM 2007]. This finding was corroborated by the cascade impactor 

measurements showing that most of the PAH particles were between 0.77 and 2.5 μm in 

aerodynamic diameter. According to all the air sampling results, 17%–56% of the PAHs 

generated during the fires were carcinogenic, probably or possibly carcinogenic to humans on 

the basis of IARC classification [IARC 2002, 2010]. Benzo[a]pyrene, the only PAH classified 

as a known human carcinogen [IARC 2010], constituted < 6% of the total PAHs. Of the 

potentially carcinogenic PAHs, naphthalene was the most variable, ranging from 1% to 51% 

of the total composition by round. The variability in PAH composition during the fires could 

be due to differences in air sampling efficiencies, air sampling locations, fuel packages, 

generation of PAHs over time, and distribution of PAHs throughout the structure. 

The fire fighters’ personal air concentrations of PAHs we measured (ranging from 61 

to 22,000 μg/m3) are comparable to or higher than those measured in other studies. For 

example, similar levels of PAHs (ranging from 8,500 to 15,000 μg/m3) have been measured 

during confined space oil fires [Feunekes et al. 1997], while lower levels of PAHs (ranging 

from < 5 to 500 μg/m3) have been measured during structural fires at training grounds 

[QFRS 2011a,b] and in the field [Jankovic et al. 1991]. In two of these studies [Jankovic et 

al. 1991; Feunekes et al. 1997], the measured PAHs existed primarily as particulate, which is 

consistent with our findings. However, Jankovic et al. [1991] did not measure naphthalene, 

which would have likely increased the proportion of vapor-phase PAHs. These study 

differences in concentration, composition, and physical state of PAHs measured in air could 

be explained by differences in sampling methods, specific chemical composition of the fuel 

packages, fire temperatures, compartment size, and ventilation conditions.
Health Hazard Evaluation Report 2010-0156-3196 Page 39

Although the corn oil matrix interfered with the analysis of some of the PAHs on the dermal 

wipe samples, we believe that we obtained a reasonable estimate of dermal exposure by 

summing individual PAHs that were not affected by the corn oil matrix. Moreover, the urine 

analysis method was most sensitive to the PAHs that were included in the dermal exposure 

variable. The dermal exposure data suggest that the neck skin was the most exposed part of 

the fire fighters’ bodies. Unlike the other areas of the fire fighters’ bodies that were covered 

in multiple layers of protective clothing, the neck was primarily protected by a Nomex® 

hood made of a double layer of porous flame-resistant fabric. Because the hoods and turnout 

gear were not contaminated with PAHs (from laundering or being brand new), the increase 

in dermal exposure to the neck was most likely due to the penetration of PAHs around the 

turnout gear collar and through or around the Nomex hoods (Figure 26). The hoods worn in 

round 1 were shorter in length than the hoods worn in round 2, resulting in some becoming 

untucked from the turnout gear jacket during the exercises. This could have further increased 

the potential for dermal exposure to the neck and may even explain why the post-exposure 

increase of PAHs on the neck was significant for round 1 (sign test P = 0.02) but not round 

2 (sign test P = 0.07). If dermal exposure to PAHs occurred on the other skin sites, it was of 

lesser magnitude (e.g., below the MDC) or it was absorbed rapidly before the post-exposure 

collection period. 

Figure 26. (Left) Photograph of fire fighter in full ensemble showing the area of the neck that is protected 

primarily by the white Nomex hood; (Right) Hood after being worn once for a fire suppression exercise 

during round 1. Photos by NIOSH. 

Benzene, a known human carcinogen [IARC 1982], was the predominant aromatic 

hydrocarbon in the post-exposure breath samples. However, for round 1, several of the other 

aromatic hydrocarbons were elevated in the post-exposure breath samples compared to the 

pre-exposure levels, and some of these elevations were statistically significant. Because we 

did not measure aromatic hydrocarbons on the skin or in the personal breathing zones, we 

are unable to address the relationship of these findings to actual exposures during the burns. 
Page 40 Health Hazard Evaluation Report 2010-0156-3196

The aromatic hydrocarbons would exist as vapors during the burns and these vapors could 

adsorb to carbonaceous particles generated by the fires. For benzene and the other aromatic 

hydrocarbons to be elevated in the post-exposure samples, they had to be present in the air 

and absorbed through the skin and into the blood stream rapidly. Alternatively, they could 

have off-gassed from contaminated clothing and equipment and been inhaled during the 

doffing of the gear. As with PAHs, the neck was the most likely site for dermal exposure to 

benzene and the other aromatic hydrocarbons. None of the PAHs (except for naphthalene) 

were elevated in the post-exposure breath samples. This finding is not surprising because 

PAHs (except for naphthalene) are considered nonvolatile or semivolatile and therefore 

would not readily diffuse from the blood into the gas-exchange region of the lungs. 

Post-exposure breath levels of benzene reported by the NIOSH lab for round 1 (median = 

300 μg/m3, range = < 100–620 μg/m3) differ from those reported by the EPA lab for round 

1 (median = 35 μg/m3, range = 5.6–350 μg/m3). The method used by the NIOSH lab had a 

much higher LOD for benzene than the method used by the EPA lab. Therefore, our estimate 

of the median levels for the round 1 NIOSH post-exposure breath data for benzene may be 

overestimated because 40% of the measurements were ND and were assigned values that 

could be considered too high. Although the round 1 EPA post-exposure breath samples for 

benzene were not analyzed until almost 1 year after collection, we do not believe this affected 

our results significantly because studies have shown negligible degradation of benzene on 

thermal desorption tubes stored in a freezer for several months [Vandendriessche and Griepink 

1989; HSE 1993]. Both methods detected changes over time during round 1, and in fact, 

the pre minus post change in levels measured by NIOSH was significantly correlated with 

the respective change in levels measured by EPA for round 1 (P = 0.01). The post-exposure 

breath concentrations of benzene using EPA data for both rounds (median = 19 μg/m3, range 

= 3.2–350 μg/m3) were comparable to the post-exposure breath concentrations of benzene in a 

study of nonsmoking automobile mechanics after 4 hours of work (median = 19 μg/m3, range = 

3.5–500 μg/m3) [Egeghy et al. 2002]. Although dermal exposure to benzene was not assessed in 

that study, most (> 90%) of the automobile mechanics’ personal air concentrations of benzene 

(median = 68 μg/m3, range = 12–860 μg/m3) were below the NIOSH work-shift recommended 

exposure limit of 320 μg/m3 [Egeghy et al. 2002; NIOSH 2010b]. 

Although benzene was elevated in the breath of the fire fighters, urinary excretion of s-PMA

(a metabolite of benzene) was below the MDC of 8.5 μg/g for all samples. The s-PMA 

analysis of urine did not occur until as much as 2 years after collection. Because the urine 

samples were stored in a –4°F freezer, it is unlikely that the benzene metabolite would have 

degraded much (if at all). Thus, our data suggest that the overall dose of benzene in this study 

resulted in urinary s-PMA levels well below the ACGIH BEI (25 μg/g) [ACGIH 2013]. 

The 3-hour urinary PAH metabolite levels (median = 62 μg/g, range = 28–140 μg/g) were 

lower than the baseline urinary PAH metabolite levels in a study of nonsmoking asphalt 

pavers (median = 110 μg/g, range = 57–140 μg/g) [McClean et al. 2012] and comparable to 

the levels measured in a study of nonsmokers without occupational PAH exposures (median 

= 67 μg/g, range = 6–220 μg/g) [Osborn et al. 2011; Smith et al. 2011]. These studies used 

the same method for analyzing PAH metabolites as we did. 
Health Hazard Evaluation Report 2010-0156-3196 Page 41

Correlations between the Exposure and Biomarker Variables 

Despite our best efforts, the fire fighters could have been exposed to PAHs or benzene from 

sources other than the controlled burns, including PAHs consumed through food prior to the 

study, PAHs in personal care products applied to the skin prior to the study, and PAHs or 

benzene from vehicle exhaust during the drive to the study site. Depending on the timing, 

the PAH or benzene exposures from these other sources could show up in a participant’s 

biomarker measurements. However, the exposure and biomarker variables would not 

necessarily be statistically correlated if the participant’s biomarker levels only came from 

these other sources. Although the statistically significant correlations we found between the 

exposure and biomarker variables were not consistent between rounds, the exposure variables 

were related to the biomarker variables in the expected direction for both rounds. This finding 

provides additional evidence that PAHs and benzene generated by the fires were absorbed 

into the fire fighters’ bodies. 

When SCBA is worn, maintained, and functioning properly, it should virtually eliminate 

the inhalation route of exposure. According to our testing during round 2, most of the 

SCBA were functioning properly. Only one SCBA failed the breathing test, which indicates 

that all the other SCBA would have maintained positive pressure during the round 2 

exercises. Because the fire fighters did not perform especially strenuous activities such as 

carrying victims, climbing stairs, or forcible entry, it is unlikely that their respiration rates 

were higher than the maximum rate used for testing (103 Lpm). Any leakage from poor 

facepiece fit or slippage would result in the flow of clean air outward, not contaminated air 

inward. Therefore, the PAHs, which are nonvolatile or semivolatile, most likely entered 

the fire fighters’ bodies through the dermal route. Dermal absorption of benzene was also a 

possibility. Because benzene and the other aromatic hydrocarbons are volatile, they could 

have evaporated from the contaminated clothing or equipment when fire fighters were doffing 

their gear. In round 2, we found elevated levels of benzene and toluene off-gassing from 

recently used turnout gear. Because the fire fighters removed their SCBA first after each burn, 

inhalation of benzene was also a possibility. 

Our findings are similar to the findings in other studies where investigators measured 

biomarkers of PAHs and benzene in fire fighters who wore SCBA most of the time during 

controlled [Laitinen et al. 2009] and uncontrolled fires [Caux et al. 2002]. Caux et al. [2002] 

found that the largest increase in urinary excretion of 1-hydroxypyrene (a PAH metabolite) 

occurred between 4 and 8 hours after the exposure period, but were unable to identify the 

peak excretion of muconic acid (a benzene metabolite). Laitenen et al. [2009] found that the 

largest increase in 1-hydroxypyrene and 1-napthol occurred 6 hours after the exposure period 

and the largest increase in muconic acid occurred immediately after the exposure period. 

Instead of muconic acid in urine, we measured s-PMA in urine and benzene in breath. We 

found statistically significant increases of benzene in breath immediately after the exposure 

period, but urine levels of s-PMA were all ND (< 8.5 μg/g). The peak urinary excretion of 

PAH metabolites in our study occurred 3 hours after the exposure period, which is sooner 

than the time to maximum excretion reported in these other studies. 
Page 42 Health Hazard Evaluation Report 2010-0156-3196

Dermal Absorption of Polycyclic Aromatic Hydrocarbons and 

Benzene

Several studies have measured dermal absorption of PAHs [Storer et al. 1984; Kao et al. 

1985; VanRooij et al. 1993; Roy et al. 1998]. Absorption rates of PAHs depend on many 

factors, including the molecular structure of the PAH and the skin site where exposure 

occurs [VanRooij et al. 1993; Roy et al. 1998]. Researchers [VanRooij et al. 1993] found 

that 20%–56% of PAHs (as a low dose of coal tar) on the skin will be absorbed within 6 

hours depending on the anatomical site of the dose. In general, anatomical sites with thinner 

skin had faster absorption rates. Based on urinary excretion of 1-hydroxypyrene, absorption 

through neck skin was faster than absorption through several other skin sites (i.e., calf, 

forearm, trunk, and hand) [VanRooij et al. 1993]. 

Compared to other studies involving fire fighters [Caux et al. 2002; Laitinen et al. 2009, 

2012] or topical exposure of PAHs to the skin [VanRooij et al. 1993], the apparent faster 

absorption and excretion rate of PAHs in our study could be due to a variety of factors, 

including the composition of PAHs produced, extreme environmental conditions of the 

fires, and that neck skin was the most exposed site of the fire fighters’ bodies. The exposure 

time in our study was also relatively short (≤ 30 minutes). Longer exposure times, as in 

the 90 minutes of exposure in the study by Laitenen et al. [2009], could extend the time to 

maximum excretion.

Dermal absorption of benzene depends on many factors, including its physical state (liquid 

or vapor), presence and type of vehicle (neat or dissolved in a solvent), and amount of time 

on the skin, which is probably the rate determining step [Wester and Maibach 2000]. Several 

studies have found that < 1% of benzene applied as liquid to the skin is absorbed, primarily 

because of a high rate of evaporation from the skin [Maibach and Anjo 1981; Franz 1984; 

Wester et al. 1993]. In a study where investigators exposed rhesus monkey skin (in vivo) 

to benzene (dissolved in water) and then continuously monitored exhaled breath, the peak 

exhaled breath concentrations occurred almost 2 hours after topical application [Thrall et al. 

2000]. Our data and the data from Laitenen et al. [2009] suggest faster dermal absorption of 

benzene in humans than in monkeys. 

Humidity is another important factor in the dermal absorption of benzene. Franz [1984] 

found that dermal absorption of benzene vapor was 2.5 to 7.5 times greater in 100% relative 

humidity environments than 40% relative humidity environments. Benzene is soluble in 

water, which is less volatile than benzene. In high humidity environments, benzene vapor 

could dissolve in moisture that collects on the skin, thereby increasing the amount of time on 

the skin. For example, Franz [1984] reported that 5% to 6% of the applied dose was absorbed 

when benzene was dissolved in water versus < 0.20% when it was dissolved in toluene. 

In addition to humidity, ambient temperature and protective clothing can also affect dermal 

absorption of chemicals. Jones et al. [2003] found that greater ambient temperatures 

increased dermal absorption of 2-butoxyethanol vapor in human volunteers. Like benzene, 
Health Hazard Evaluation Report 2010-0156-3196 Page 43

2-butoxyethanol is water soluble. The authors postulated that this increase in dermal 

absorption was due to increased surface blood flow, increased skin hydration and perspiration 

(which could increase the effective permeability coefficient and residence time of the 

chemical on skin), and opening of skin pores. This study also showed that some types of 

protective clothing will not decrease dermal absorption and may in fact increase dermal 

absorption by creating a micro-climate next to the skin, such as a high humidity atmosphere. 

In our study, some of these factors could have increased the dermal absorption of aromatic 

hydrocarbon vapors and PAHs. 

If dermal absorption was the primary route of exposure to benzene and the other aromatic 

hydrocarbons, relatively high air concentrations of these compounds would be necessary 

for us to detect changes in the post-exposure breath samples. We only measured air 

concentrations of benzene and other VOCs during the last fire for round 2. During this 

fire, the benzene concentration (95,000 μg/m3) was 16 times greater than the toluene 

concentration (6,000 μg/m3). These levels far exceed the levels of benzene (80–360 μg/

m3) and toluene (40–300 μg/m3) measured by Queensland Fire and Rescue Service 

investigators during similar types of structural training fires [QFRS 2011a,b]. However, 

similar air concentrations of benzene (70,000 μg/m3 [Jankovic et al. 1991]) and higher air 

concentrations of toluene (20,000 μg/m3 [Austin et al. 2001b]) have been reported during 

knockdown of structure fires. Because toluene has a similar rate of dermal absorption as 

benzene [Franz 1984], we would expect the post-exposure increase in benzene concentrations 

to be around 16 times greater than the post-exposure increase in toluene concentrations for 

the exhaled breath samples collected during the last day of round 2. Compared to toluene, the 

increase in benzene concentrations were, on average, 13 times greater in these samples (data 

not shown). The differences between the post-exposure increases in breath concentrations 

of these two compounds were less pronounced for the other burns, suggesting less disparate 

benzene and toluene air concentrations for those burns.

Carcinogenicity of Polycyclic Aromatic Hydrocarbons and 

Benzene

Animal studies have shown that exposure to PAHs can cause cancer, most often at the 

site of dosage, but occasionally at more distant sites [ATSDR 1995; IARC 2002, 2010]. 

Occupational epidemiology studies have primarily found associations between exposures 

to PAHs (typically as a mixture with other chemicals) and lung, skin, or bladder cancer, 

depending on the route of exposure [ATSDR 1995; Boffetta et al. 1997; IARC 2002, 2010]. 

Occupational exposure to benzene has been consistently linked to leukemia [IARC 1982; 

ATSDR 2007]. Because PAH exposure to the scrotum has been associated with scrotal cancer 

in chimney sweeps [Hall 1998], the possibility exists that PAH exposure to the scrotum 

could also lead to testicular cancer in fire fighters. However, we did not find elevated postexposure levels of PAHs on the scrotum. The fire fighters in our study wore NFPA 1971/1981 

compliant protective ensembles for structural fires [NFPA 2007a,b]. This gear likely provides 

more protection to the genital area than the traditional long coats and 3/4 boots that were 

worn by some fire fighters in the past. 
Page 44 Health Hazard Evaluation Report 2010-0156-3196

Some studies have found elevated risk for these cancers in fire fighters while others have not. 

In a meta-analysis of cancer studies in fire fighters, LeMasters et al. [2006] found a probable 

or possible increased risk for 12 types of cancer, including leukemia, skin, and testicular 

cancer, but not lung or bladder cancer. More recently in the largest fire fighter cancer study to 

date, Daniels et al. [2013] found that fire fighters had an increased incidence of eight types of 

cancers, including lung and bladder cancer, but not leukemia, skin, or testicular cancer. More 

research is needed to quantify and better understand these risks and the role that chemical 

exposures may play. 

Protective Equipment Use and Other Potential Exposures 

Of the fire fighters in this study, 40%–60% reported typically wearing SCBA during 

overhaul. Of those who wear SCBA for overhaul or salvage, the SCBA was worn 36%–53% 

of the time. Austin et al. [2001a] conducted a study of SCBA use at a large municipal fire 

department and reported that SCBA was not worn at all during overhaul. Because fire fighters 

may not consistently wear SCBA during overhaul or investigation phases of a fire response, 

our measurements of PAHs, VOCs, and particles during these phases are meaningful as they 

represent potential inhalation exposures. 

We measured air concentrations of total PAHs and total particle-phase PAHs during overhaul 

on round 1 that exceeded the ACGIH excursion limit for coal tar pitch volatiles. This finding 

suggests that fire fighters could have been overexposed if they had not worn respiratory 

protection during overhaul on round 1. The total PAH concentrations dropped below this 

excursion limit for all the investigation phases. The air concentrations of the VOCs during 

the overhaul and investigation phases were above background levels, but were well below 

applicable STELs and ceiling limits, even when using the ACGIH additive mixture formula 

[ACGIH 2013]. Most of the direct-reading particulate levels remained above background 

levels through the overhaul phase of the burns. Our air measurements during overhaul and 

investigation could underestimate what fire fighters often encounter in the field because the 

burn structures were relatively small and well-ventilated, which allowed heat and contaminants 

to dissipate quickly. In addition, we did not measure air concentrations of a variety of chemicals 

that were also likely produced including aldehydes, acid gases, cyanides, and oxides of carbon, 

nitrogen, and sulfur [Jankovic et al. 1991; Bolstad-Johnson et al. 2000]. Overexposures to these 

compounds have been measured during overhaul [Bolstad-Johnson et al. 2000]. Therefore, the 

continual use of SCBA inside the structure after fire suppression is necessary. 

After responding to a fire, fire fighters commonly wear a portion of their contaminated 

turnout gear in the fire apparatus when riding back to the station. If windows are closed, fire 

fighters may be exposed to chemicals that off-gas from their gear. In this study, we placed 

the turnout gear in an enclosed case approximately 25 minutes after the exposure period 

and sampled for VOCs. Although the enclosed case was smaller than the typical cabin of a 

fire apparatus, the VOC concentrations measured were still well below applicable STELs or 

ceiling limits. However, we did not measure all possible off-gassing chemicals. Higher offgassing VOC air concentrations would be expected when fire fighters leave a site quickly and 

when their gear is especially contaminated.
Health Hazard Evaluation Report 2010-0156-3196 Page 45

When donning and doffing turnout gear, fire fighters may inadvertently transfer contamination 

from their gear to their skin. We found no evidence of contamination on the interior of the turnout 

gear; however, the exterior of the gear was contaminated with PAHs post-exposure (ranging 

from 3.3 to 27 μg per sample). The greatest amount of contamination was found on a helmet 

pre-exposure (192 μg). The helmets, unlike the other gear, were not required to be cleaned 

before our study. The external surface areas we sampled were not standardized, but we sampled 

approximately 500 cm2 of material each time. Adjusting by this surface area, the levels we found 

were comparable to the levels that Queensland Fire and Rescue Service investigators found 

on turnout gear following controlled residential room fires (ranging from 7.8 to 55 μg [QFRS 

2011b]), but much higher than the levels Queensland Fire and Rescue Service investigators found 

on turnout gear following controlled office room fires (ranging from 0.06 to 0.75 μg [QFRS 

2011a]). Greater deposition of PAHs onto gear can be expected when the air concentrations of 

PAHs are higher and a greater fraction of them are particulate. 

During the study, we watched the fire fighters don and doff their gear. We noticed very 

little opportunity for transfer of contamination to their skin, but the fire fighters may have 

been especially careful due to the study. Hand washing and showering are important 

ways of minimizing dermal absorption, hand to mouth ingestion, and the transfer of 

contamination to family members. Every fire fighter participating in this study reported 

normally showering after fire suppression. Showering was prohibited in this study until 

the last biomarker collection period. Storing gear in appropriate locations (e.g., locker 

storage area) is an important way of minimizing cross contamination. More than 25% of the 

participants reported occasionally storing their gear in the fire apparatus and 40% or more 

of the participants reported occasionally storing their gear in their personal vehicle. Storing 

contaminated gear in either of these locations could unnecessarily expose people through offgassing of the gear or transferring contamination from gear to other surfaces. 

Conclusions 

We found that fire fighters wearing full ensembles absorb PAHs and aromatic hydrocarbons 

into their bodies. The PAHs and aromatic hydrocarbons most likely entered the fire fighters’ 

bodies through the skin, with the neck being the primary site of exposure and absorption 

due to the lower level of skin protection afforded by hoods. Aromatic hydrocarbons could 

also have been inhaled if they off-gassed from the contaminated clothing and equipment 

when the fire fighters were doffing their gear. Although the biological levels we measured 

are similar to or lower than the levels measured in other occupational groups with low levels 

of exposure, the absorbed dose will vary with ambient air concentrations of contaminants. 

PAHs were found on the exterior of gear, which could be another source of dermal exposure 

for fire fighters. Air concentrations of PAHs, VOCs, and particulate during overhaul and 

investigation phases, along with VOCs off-gassing from contaminated turnout gear, were 

below applicable STELs or ceiling limits but represent additional exposures during a typical 

workday. Further study is needed to determine the contribution of all these sources to a fire 

fighter’s overall internal dose.
Page 46 Health Hazard Evaluation Report 2010-0156-3196

Recommendations for Protecting Fire Fighters 

On the basis of our findings, we recommend the actions listed below to better protect 

fire fighters. We encourage fire departments to use a labor-management health and safety 

committee or working group to discuss the recommendations in this report and develop an 

action plan. Those involved in the work can best set priorities and assess the feasibility of our 

recommendations for the specific situation. 

● To minimize inhalation of contaminants during a fire response:

○ Maintain and test SCBA routinely to ensure its proper function. In particular, 

the SCBA facemask should seal around the face and be able to maintain positive 

pressure.

○ Wear SCBA during knockdown, overhaul, and other fire fighting activities where 

exposure to combustion products is likely.

○ Remain upwind of fires if not directly involved in the fire response.

○ Provide as much natural ventilation as feasible to burned structures prior to 

starting investigations and during activities where responders may not wear SCBA

or other respiratory protection. 

● To minimize skin absorption of contaminants during (or after) a fire response:

○ Wear NFPA 1971/1981 compliant protective ensembles for structural fires during 

knockdown and overhaul for all fire responses.

○ Wear long hoods that are unlikely to come untucked during operations. 

○ Wash hands immediately and shower as soon as possible after fire suppression, 

overhaul, and investigation activities, particularly when exposed to a great deal of 

smoke or when soot is visible on the skin.

○ Put on laundered station uniforms or other clean clothing after showering.

○ Launder turnout gear routinely using a professional service. Do not launder this 

gear at home.

○ Clean other equipment that could contact the skin if it is visibly soiled. Clean 

SCBA facemasks after each use using cleaners approved by the manufacturer.

● To minimize the potential inhalation of contaminants off-gassing from contaminated 

gear:

○ Remove SCBA (and hood) last when doffing gear after fire suppression activities.

○ Doff gear before entering the rehab area.

○ Store gear on the outside of the apparatus during the ride back to the station.

○ Do not store gear in personal vehicles or living areas.
Health Hazard Evaluation Report 2010-0156-3196 Page 47

Recommendations for Additional Research 

Because this was a pilot study, one goal was to stimulate further research. Below, we propose 

ideas for additional research on the basis of our findings. 

● Evaluate fire fighters’ exposures to combustion products during real fire responses. This 

research should aim to determine the relative contribution of each source and route of 

exposure to a fire fighters’ overall internal dose.

● Assess inhalation exposures to combustion products for personnel at a fire scene who 

are not directly involved in the fire suppression. If these employees do not wear SCBA, 

their exposures could be greater than the responders’.

● Study the effect of turnout hood designs and materials on dermal exposure and 

absorption of combustion products. The neck was the only skin site where we measured 

elevated levels of PAHs that were statistically significant (for round 1) and was also a 

possible site for dermal absorption of aromatic hydrocarbons (e.g., benzene). Providing 

better protection to the neck could reduce dermal absorption of combustion products.

● Explore the performance of SCBA under high heat conditions. Although our testing 

demonstrated that most SCBA was functioning properly, this testing was done at 

ambient environmental conditions.

● Investigate the impact of different methods of decontaminating gear (including rinsing 

with water) on removing PAHs and other surface contaminants.

● Develop portable multi-substance direct-reading instruments and guidelines to establish 

when post-knockdown airborne contaminant levels are “safe” for fire fighters or other 

personnel (e.g., cause and origin investigators) to remove SCBA.
Page 48 Health Hazard Evaluation Report 2010-0156-3196

Appendix A: Self-contained Breathing Apparatus 

Performance Testing Protocol and Results

Maximum Work Rate Breathing Test 

This is an implementation of the airflow performance test defined in section 8.1 of NFPA 

1981 [NFPA 2007b]. The breathing machine operates at a volume work rate corresponding 

to respiration at 103±3 Lpm and 30±1 breaths per minute. This simulates a heavy workload 

as might be experienced by a fire fighter carrying an average sized adult victim. The machine 

is constructed to the requirements of the standard; however, the pressure transducer and 

data recording equipment are not exactly those specified by the standard. In addition, the 

standard requires the test to be performed using a full air cylinder, which is breathed down 

until it reaches 290 pounds per square inch (psi) or less, taking approximately 10 minutes. 

We performed an abbreviated version of the test where the SCBA is pressurized, the cylinder 

valve is closed, and the breathing machine operates until the system pressure falls to 

approximately 500 psi. This abbreviated test typically completes in less than 30 seconds. The 

pressure inside the respirator facepiece is measured while the breathing machine operates, 

and section 7.1 of NFPA 1981 [NFPA 2007b] requires that this remain between 0.0′′ water 

and 3.5′′ water.

Standard Work Rate Breathing Test

Similar to the maximum work rate breathing test, this test follows guidelines specified 

in 42 CFR 84.90. It uses a reduced volume work rate of 40±1 Lpm and 24±1 breaths per 

minute to represent moderate physical activity. The breathing machine used in this study 

is different from that specified in the NIOSH test method [NIOSH 2005]. In addition, the 

test we performed was abbreviated as it was under the maximum work rate breathing test 

by pressurizing the SCBA, closing the cylinder valve, and then operating the breathing 

machine. The pass/fail criterion used by the PosiChek3 is whether facepiece pressure remains 

between 0.0′′ water and 3.5′′ water. The NIOSH requirement for pressure-demand SCBA is 

that facepiece pressure remains at or above 0.0′′ water. This is a modification of the value 

specified in 42 CFR 84.90(b) for this class of respirators, established by policy. The results 

can be used as a rough indicator of whether the SCBA could pass the NIOSH test, but 

correlation between the two tests has not been definitively established.

Facepiece Leakage Test

This test checks whether the facepiece has a good seal to the dummy test head on the 

breathing machine. It can also detect leaks in the exhalation valve or other hardware 

components on the facepiece. It is similar to the seal check specified in section 8.1.5.3 

of NFPA 1981, but with a different pass/fail criterion. The breathing machine starts an 

inhalation stroke, lowering the facepiece pressure to −1.0′′ water, and then stops. After 5 

seconds, the pressure must remain at or below −0.1′′ water.
Health Hazard Evaluation Report 2010-0156-3196 Page 49

Exhalation Valve Opening Pressure Test 

There is no NIOSH or NFPA test closely analogous to this one. The breathing machine starts 

an exhalation stroke and measures the facepiece pressure required to open the exhalation 

valve. If this value is excessive, it can indicate a sticking or damaged exhalation valve. The 

pass/fail value is established by the SCBA manufacturer. For this study it was between 1.5′′ 

and 2.5′′ water for an MSA Ultra Elite facepiece.

Pressure Gauge Test 

The remote gauge indicating SCBA cylinder pressure is required by 42 CFR 84.82(d)(1) to 

be accurate to within ±5% full scale at five equally-spaced points. The PosiChek3 checks 

accuracy at three points.

Static Facepiece Pressure Test 

Static pressure is where zero flow occurs in the facepiece. If the static pressure is high, the 

respirator wearer will spend more effort to exhale. The maximum static pressure is limited 

by 42 CFR 84.91(d) to 1.5′′ water. The PosiChek3 additionally checks that this value is not 

below 0.6′′ water.

Alarm Accuracy Test

The MSA Audi-LarmTM is a bell that alerts the wearer when the air supply is becoming 

exhausted. The PosiChek3 senses the pressure at which the Audi-Larm activates. This is 

required to be between 23% and 27% of full cylinder pressure by 42 CFR 84.83(f), modified 

by policy under 42 CFR 84.82(g). The full cylinder pressure for the SCBA used is 4,500 psi.

Redundant Alarm Accuracy Test 

Section 6.1.4 of NFPA 1981 requires that each SCBA have at least two low-air alarms. The 

second one, in this case an electronic alarm, must meet the same accuracy requirement as the 

Audi-Larm bell.
Page 50 Health Hazard Evaluation Report 2010-0156-3196

Table A1. Results of SCBA performance testing for burn 1 of round 2

Test criterion Acceptable range SCBA by worker identification number

200* 201* 202 203 204*

Maximum work rate breathing 

(inhalation)

≥ 0.0′′ water 0.3 0.2 0.2 0.3 0.3

Maximum work rate breathing 

(exhalation)

≤ 3.5′′ water 2.5 2.4 2.3 3.1 2.5

Standard work rate breathing 

(inhalation)

≥ 0.0′′ water 0.3 0.3 0.3 0.4 0.3

Standard work rate breathing 

(exhalation)

≤ 3.5′′ water 2.1 1.9 1.8 1.9 3

Facepiece leakage ≤ −0.1′′ water −0.1 −0.1 0

FAIL

−0.3 −0.1

Exhalation valve opening pressure 1.5 to 2.5′′ water 1.8 1.7 1.6 1.4

FAIL

1.7

Pressure gauge (3000 psi) 2775 to 3225 psi 2953 3049 2963 2961 2937

Pressure gauge (2000 psi) 1775 to 2225 psi 1954 2055 1971 1969 1932

Pressure gauge (1000 psi) 775 to 1225 psi 984 1047 988 1002 942

Static facepiece pressure 0.6 to 1.5′′ water 1 1.2 0.7 1 1.1

Alarm Accuracy 1035 to 1215 psi 1050 1131 1191 1102 1090

Redundant Alarm Accuracy 1035 to 1215 psi 1124 1114 1199 1129 1069

*Used substituted facepieces because of damage or potential problems

Table A2. Results of SCBA performance testing for burn 2 of round 2

Test criterion Acceptable 

range

SCBA by worker identification number

205* 206 207 208 209

Maximum work rate breathing 

(inhalation)

≥ 0.0′′ water 0.5 0.2 0.1 0.2 0.4

Maximum work rate breathing 

(exhalation)

≤ 3.5′′ water 2.5 2.2 2.3 2.4 2.3

Standard work rate breathing 

(inhalation)

≥ 0.0′′ water 0.4 0.4 0.2 0.3 0.5

Standard work rate breathing 

(exhalation)

≤ 3.5′′ water 2 1.7 1.9 1.9 1.9

Facepiece leakage ≤ –0.1′′ water 0

FAIL

−0.2 −0.1 −0.2 −0.2

Exhalation valve opening 

pressure

1.5 to 2.5′′ 

water

1.7 1.3

FAIL

1.6 1.7 1.6

Static facepiece pressure 0.6 to 1.5′′ 

water

1.1 1 0.9 1 1.3

*Used a substituted facepiece because of damage or other potential problems
Health Hazard Evaluation Report 2010-0156-3196 Page 51

Table A3. Results of SCBA performance testing for burn 3 of round 2

Test criterion Acceptable range SCBA by worker identification number

210 211 212 213 214*

Maximum work rate 

breathing (inhalation)

0.0′′ water 0.5 0.4 0.1 0 −0.3

FAIL

Maximum work rate 

breathing (exhalation)

3.5′′ water 2.4 2.6 2.5 2 2.2

Standard work rate 

breathing (inhalation)

0.0′′ water 0.4 0.4 0.3 0 0

Standard work rate 

breathing (exhalation)

3.5′′ water 2 2 1.9 1.4 1.7

Facepiece leakage −0.1′′ water −0.1 0

FAIL

−0.1 −0.1 −0.1

Exhalation valve opening 

pressure

1.5 to 2.5′′ water 1.6 1.6 1.2

FAIL

1.2

FAIL

1.5

Static facepiece pressure 0.6 to 1.5′′ water 0.9 1.4 0.9 0.6 0.8

*Used a substituted facepiece due to damage or other potential problems
Page 52 Health Hazard Evaluation Report 2010-0156-3196

Appendix B: Number of ND Values, MDCs, and 

MQCs for Personal Exposure Variables

Table B1. Number of samples and ND values, as well as the MDCs, and MQCs for personal 

exposure variables with a single analyte

Variable Round 1 Round 2

n ND MDC MQC n ND MDC MQC

Pre-exposure urinary PAH metabolite 

levels (μg/g) 

15 3 22 66 15 5 22 66

Post-exposure urinary PAH metabolite 

levels (μg/g)

15 1 22 66 15 2 22 66

3-hour post-exposure urinary PAH 

metabolite levels (μg/g)

15 3 22 66 15 2 22 66

6-hour post-exposure urinary PAH 

metabolite levels (μg/g)

15 3 22 66 15 5 22 66

Pre-, post-, 3-hour post-, 6-hour postexposure urinary s-PMA levels (μg/g)60 60 8.5 NA 60 60 8.5 NA

Pre-exposure exhaled breath 

concentrations of benzene

(NIOSH data, μg/m3)

15 15 100 350 15 14 50 180

Post-exposure exhaled breath 

concentrations of benzene

(NIOSH data, μg/m3)

15 6 100 350 15 15 50 180

6-hour post-exposure exhaled breath 

concentrations of benzene

(NIOSH data, μg/m3)

15 6 100 350 15 15 50 180

Pre-exposure exhaled breath 

concentrations of toluene

(NIOSH data, μg/m3)

15 15 100 350 15 15 50 170

Post-exposure exhaled breath 

concentrations of toluene

(NIOSH data, μg/m3)

15 10 100 350 15 15 50 170

6-hour post-exposure exhaled breath 

concentrations of toluene

(NIOSH data, μg/m3)

15 15 100 350 15 15 50 170

Pre-exposure exhaled breath 

concentrations of anthracene (μg/m3)

15 0 0.05 0.21 15 0 0.05 0.21

Post-exposure exhaled breath 

concentrations of anthracene (μg/m3)

15 2 0.05 0.21 15 0 0.05 0.21

6-hour post-exposure exhaled breath 

concentrations of anthracene (μg/m3)

15 1 0.05 0.21 15 0 0.05 0.21
Health Hazard Evaluation Report 2010-0156-3196 Page 53

Table B2. Number of samples and ND values, as well as the MDCs and MQCs for the personal 

exposure variables that were calculated by summing more than one analytical value

Variable Components of the 

variable

Round 1 Round 2

n ND MDC MQC n ND MDC MQC

Personal air 

concentration of 

PAHs (μg/m3)

Respirable particles 

4 rings and less

14 0 1 280 13 0 2 6

Respirable particles 

5 rings and more

14 0 1 5 13 1 2 6

Vapors

4 rings and less

14 1 3 14 13 0 2 18

Vapors

5 rings and more

14 14 3 * 13 11 2 *

Pre-exposure levels 

of PAHs on the neck 

(μg/m2)

Anthracene 15 14 7 20 15 15 12 40

Benzo(a)pyrene 15 15 10 31 15 14 7 238

Chrysene 15 15 10 29 15 14 7 48

Fluoranthene 15 15 7 23 15 15 21 67

Phenanthrene 15 15 14 50 15 14 12 48

Pyrene 15 15 10 29 15 10 17 52

Post-exposure 

levels of PAHs on 

the neck (μg/m2)

Anthracene 15 11 7 20 15 15 12 40

Benzo(a)pyrene 15 15 10 31 15 13 7 238

Chrysene 15 14 10 29 15 11 7 48

Fluoranthene 15 13 7 23 15 11 21 67

Phenanthrene 15 6 14 50 15 9 12 48

Pyrene 15 14 10 29 15 13 17 52

Pre-exposure levels 

of PAHs on the 

interior of turnout 

gear sleeves (μg)

4 rings and less 15 4 0.7 2.4 15 0 0.3 2.0

5 rings and more 15 15 1.0 3.3 15 15 0.1 0.50

Post-exposure 

levels of PAHs 

on the interior 

of turnout gear 

sleeves (μg)

4 rings and less 15 3 0.7 2.4 15 3 0.3 2.0

5 rings and more 15 15 1.0 3.3 15 15 0.1 0.50

*The MQC could not be calculated using NIOSH criteria.
Page 54 Health Hazard Evaluation Report 2010-0156-3196

Appendix C: Occupational Exposure Limits and 

Health Effects

NIOSH investigators refer to mandatory (legally enforceable) and recommended OELs for 

chemical, physical, and biological agents when evaluating workplace hazards. OELs have 

been developed by federal agencies and safety and health organizations to prevent adverse 

health effects from workplace exposures. Generally, OELs suggest levels of exposure that 

most employees may be exposed to for up to 10 hours per day, 40 hours per week, for a 

working lifetime, without experiencing adverse health effects. However, not all employees 

will be protected if their exposures are maintained below these levels. Some may have 

adverse health effects because of individual susceptibility, a pre-existing medical condition, 

or a hypersensitivity (allergy). In addition, some hazardous substances act in combination 

with other exposures, with the general environment, or with medications or personal habits of 

the employee to produce adverse health effects. Most OELs address airborne exposures, but 

some substances can be absorbed directly through the skin and mucous membranes.

Most OELs are expressed as a time-weighted average exposure. A time-weighted average 

refers to the average exposure during a normal 8- to 10-hour workday. Some chemical 

substances and physical agents have recommended STEL or ceiling values. Unless otherwise 

noted, the STEL is a 15-minute time-weighted average exposure. It should not be exceeded at 

any time during a workday. The ceiling limit should not be exceeded at any time.

In the United States, OELs have been established by federal agencies, professional 

organizations, state and local governments, and other entities. Some OELs are legally 

enforceable limits; others are recommendations. 

● The U.S. Department of Labor Occupational Safety and Health Administration (OSHA) 

permissible exposure limits (PELs; 29 CFR 1910 [general industry]; 29 CFR 1926 

[construction industry]; and 29 CFR 1917 [maritime industry]) are legal limits. These 

limits are enforceable in workplaces covered under the Occupational Safety and Health 

Act of 1970. 

● NIOSH recommended exposure limits (RELs) are recommendations based on a critical 

review of the scientific and technical information and the adequacy of methods to 

identify and control the hazard. NIOSH RELs are published in the NIOSH Pocket 

Guide to Chemical Hazards [NIOSH 2010]. NIOSH also recommends risk management 

practices (e.g., engineering controls, safe work practices, employee education/training, 

personal protective equipment, and exposure and medical monitoring) to minimize the 

risk of exposure and adverse health effects.

● Other OELs commonly used and cited in the United States include the threshold limit 

values (TLVs®), which are recommended by ACGIH, a professional organization, 

and the Workplace Environmental Exposure Levels, which are recommended by the 

American Industrial Hygiene Association, another professional organization. The TLVs 

and workplace environmental exposure levels are developed by committee members 
Health Hazard Evaluation Report 2010-0156-3196 Page 55

of these associations from a review of the published, peer-reviewed literature. These 

OELs are not consensus standards. TLVs are considered voluntary exposure guidelines 

for use by industrial hygienists and others trained in this discipline “to assist in the 

control of health hazards” [ACGIH 2013]. Workplace environmental exposure levels 

have been established for some chemicals “when no other legal or authoritative limits 

exist” [AIHA 2013].

Outside the United States, OELs have been established by various agencies and organizations 

and include legal and recommended limits. The Institut für Arbeitsschutz der Deutschen 

Gesetzlichen Unfallversicherung (Institute for Occupational Safety and Health of the German 

Social Accident Insurance) maintains a database of international OELs from European Union 

member states, Canada (Québec), Japan, Switzerland, and the United States. The database, 

available at http://www.dguv.de/ifa/en/gestis/limit_values/index.jsp, contains international 

limits for more than 1,500 hazardous substances and is updated periodically. 

OSHA requires an employer to furnish employees a place of employment free from 

recognized hazards that cause or are likely to cause death or serious physical harm 

[Occupational Safety and Health Act of 1970 (Public Law 91–596, sec. 5(a)(1))]. This is 

true in the absence of a specific OEL. It also is important to keep in mind that OELs may not 

reflect current health-based information.

When multiple OELs exist for a substance or agent, NIOSH investigators generally 

encourage employers to use the lowest OEL when making risk assessment and risk 

management decisions. NIOSH investigators also encourage use of the hierarchy of controls 

approach to eliminate or minimize workplace hazards. This includes, in order of preference, 

the use of (1) substitution or elimination of the hazardous agent, (2) engineering controls 

(e.g., local exhaust ventilation, process enclosure, dilution ventilation), (3) administrative 

controls (e.g., limiting time of exposure, employee training, work practice changes, medical 

surveillance), and (4) personal protective equipment (e.g., respiratory protection, gloves, 

eye protection, hearing protection). Control banding, a qualitative risk assessment and risk 

management tool, is a complementary approach to protecting employee health. Control 

banding focuses on how broad categories of risk should be managed. Information on control 

banding is available at http://www.cdc.gov/niosh/topics/ctrlbanding/. This approach can be 

applied in situations where OELs have not been established or can be used to supplement 

existing OELs.

Short-term Occupational Exposure Limits for Chemicals in this 

Report 

Each fire suppression (exposure period) in this study was relatively short (≤ 30 minutes). 

Therefore, the air concentrations we measured are most appropriately compared to STELs 

or ceiling limits (Table B1). The ACGIH excursion limits are also provided in Table B1 for 

compounds that do not have STELs but otherwise have work-shift TLVs. These excursion 

limits are determined by multiplying the work-shift TLV by five [ACGIH 2013]. If the air 

concentration of a chemical is presented in the report but is not listed in Table B1, then 
Page 56 Health Hazard Evaluation Report 2010-0156-3196

it does not have an applicable STEL, ceiling limit, or excursion limit. For some of the 

individual PAHs that are suspected human carcinogens, ACGIH recommends controlling 

exposures by all routes to levels as low as possible as noted in Table B1 [ACGIH 2011]. 

Biological Exposure Limits

Of the biomarkers measured in this study, only s-PMA in urine (a metabolite of benzene) has 

an ACGIH BEI (25 μg s-PMA/g creatinine) [ACGIH 2013]. This BEI is based on the workshift TLV of 1,600 μg/m3

. This TLV is intended to minimize the potential for leukemogenesis 

from occupational exposure [ACGIH 2011]. In most workers, s-PMA was eliminated in 

single phase with an average urinary elimination half-life of 9 hours [van Sittert et al. 1993]. 

Urine samples should be collected at the end of a work shift for comparison to this BEI 

[ACGIH 2011].
Health Hazard Evaluation Report 2010-0156-3196 Page 57

Table C1. STELs, ceiling limits, and excursion limits (μg/m3) for chemicals measured in the air and 

presented in the report

OSHA PEL NIOSH REL ACGIH TLV

STEL Ceiling 

limit STEL* Ceiling limit STEL Excursion limit

1,3-Butadiene 11,000 22,000

2-Butanone 890,000 890,000

1,4-Dichlorobenzene Ca 300,000

1,2-Dichloroethane 40,000 7,900 200,000

Benzene 16,000 3,200 8,000

Benzo[a]anthracene As low as 

possible†,‡

Benzo[b]fluoranthene As low as 

possible‡

Benzo[a]pyrene As low as 

possible‡

Bromomethane 80,000 Ca 19,000

Carbon Disulfide 93,000 31,000 16,000

Chloromethane 410,000 Ca 200,000

Chrysene As low as 

possible†,‡

Coal tar pitch 

volatiles§ 1000

Ethyl benzene 540,000 430,000

Naphthalene 11,000 75,000 75,000

Styrene 850,000 430,000 170,000

Toluene 1,100,000 560,000 75,000

Vinyl Acetate 14,000 53,000

Vinyl Chloride 13,000 Ca 13,000

Xylene 650,000 650,000

*“Ca” means NIOSH considers the chemical to be an occupational carcinogen but has not 

assigned an exposure limit to it.

†ACGIH documentation states that exposures should be evaluated using the ACGIH work-shift 

TLV for benzene soluble fraction of coal tar pitch volatiles (200 μg/m3) [ACGIH 2011].

‡ACGIH documentation states that for any substance with no numerical TLV but designated as 

a suspected human carcinogen, worker exposure by all routes should be carefully controlled to 

levels as low as possible [ACGIH 2011].

§Extractable fraction of total particulate containing benz[a]anthracene, benzo[b]fluoranthene, 

chrysene, anthracene, benzo[a]pyrene, phenanthrene, acridine, or pyrene [ACGIH 2011].
Page 58 Health Hazard Evaluation Report 2010-0156-3196

Appendix D: Linear Regressions for the 

Significantly Correlated Variables

Figure D1. Relationship between the personal air concentrations of PAHs and the change in urinary 

PAH metabolite levels (3-hour minus pre) during round 1 (subjects with cotinine levels > 30 μg/L 

may have been exposed to tobacco smoke and are noted with red circles). 
Health Hazard Evaluation Report 2010-0156-3196 Page 59

Figure D2. Relationship between the change in exhaled breath concentrations of benzene (post 

minus pre; NIOSH data) and the change in urinary PAH metabolite levels (3-hour minus pre) during 

round 1 (subjects with cotinine levels > 30 μg/L may have been exposed to tobacco smoke and are 

noted with red circles). 
Page 60 Health Hazard Evaluation Report 2010-0156-3196

Figure D3. Relationship between the personal air concentrations of PAHs and the change in exhaled 

breath concentrations of benzene (post minus pre) during round 2 (subjects with cotinine levels 

> 30 μg/L may have been exposed to tobacco smoke and are noted with red circles).
Health Hazard Evaluation Report 2010-0156-3196 Page 61

Figure D4. Relationship between the change in PAH levels on the neck (post minus pre) and the 

change in urinary PAH metabolite levels (3-hour minus pre) during round 2 (subjects with cotinine 

levels > 30 μg/L may have been exposed to tobacco smoke and are noted with red circles).
Page 62 Health Hazard Evaluation Report 2010-0156-3196

Appendix E: Temperature Profiles for the Burns

Round 1 Burns

Figure E1. Round 1 burn 1 temperatures inside the burn room and target room. 

Figure E2. Round 1 burn 2 temperatures inside the burn room and target room. 
Health Hazard Evaluation Report 2010-0156-3196 Page 63

Figure E3. Round 1 burn 3 temperatures inside the burn room and target room. 

Round 2 Burns 

Figure E4. Round 2 burn 1 temperatures inside the burn room. 
Page 64 Health Hazard Evaluation Report 2010-0156-3196

Figure E5. Round 2 burn 1 temperatures inside the target room. 

Figure E6. Round 2 burn 2 temperatures inside the burn room. 
Health Hazard Evaluation Report 2010-0156-3196 Page 65

Figure E7. Round 2 burn 2 temperatures inside the target room. 

Figure E8. Round 2 burn 3 temperatures inside the burn room. 
Page 66 Health Hazard Evaluation Report 2010-0156-3196

Figure E9. Round 2 burn 3 temperatures inside the target room. 
Health Hazard Evaluation Report 2010-0156-3196 Page 67

Appendix F: Direct-reading Particle Sampling 

Results from Within the Burn Structure

Round 1 Burns

Figure F1. Particle number concentration during (I) fire, (II) knockdown, and (III) overhaul phases for 

burn 2 of round 1. 

Figure F2. Particle number concentration (as measured) during (I) fire, (II) knockdown, and (III) overhaul 

phases for burn 3 of round 1. 
Page 68 Health Hazard Evaluation Report 2010-0156-3196

Figure F3. Particle number concentration, respirable mass concentration, active surface area concentration, 

and photoelectric response during (I) fire, (II) knockdown, and (III) overhaul phases for burn 2 of round 1. 

Note: the photometer (respirable particle mass) malfunctioned a few minutes after fire ignition. 
Health Hazard Evaluation Report 2010-0156-3196 Page 69

Figure F4. Particle number concentration, active surface area concentration, and photoelectric response 

during (I) fire, (II) knockdown, and (III) overhaul phases for burn 3 of round 1. Note: the photometer (respirable particle mass) did not log data.
Page 70 Health Hazard Evaluation Report 2010-0156-3196

Round 2 Burns 

Figure F5. Particle number concentration during (I) fire, (II) knockdown, and (III) overhaul phases for burn 1 of 

round 2. 

Figure F6. Particle number concentration during (I) fire, (II) knockdown, and (III) overhaul phases for burn 

2 of round 2. 
Health Hazard Evaluation Report 2010-0156-3196 Page 71

Figure F7. Particle number concentration during (I) fire, (II) knockdown, and (III) overhaul phases for burn 

3 of round 2. 
Page 72 Health Hazard Evaluation Report 2010-0156-3196

Figure F8. Particle number concentration, active surface area concentration, and photoelectric response 

during (I) fire, (II) knockdown, and (III) overhaul phases for burn 1 of round 2. Note: the photometer (PM10

particle mass) did not log data.
Health Hazard Evaluation Report 2010-0156-3196 Page 73

Figure F9. Particle number concentration, particle mass concentration, respirable mass concentration, active 

surface area concentration, and photoelectric response during (I) fire, (II) knockdown, and (III) overhaul 

phases for burn 2 of round 2.
Page 74 Health Hazard Evaluation Report 2010-0156-3196

Figure F10. Particle number concentration, particle mass concentration, respirable mass concentration, 

active surface area concentration, and photoelectric response during (I) fire, (II) knockdown, and (III) overhaul phases for burn 3 of round 2.
Health Hazard Evaluation Report 2010-0156-3196 Page 75

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Keywords: North American Industry Classification System 922160 (Fire Protection), PAHs, 

aromatic hydrocarbons, benzene, dermal exposure, dermal absorption, skin, fire fighters, 

turnout gear, contamination, urine, breath, biomarker
Health Hazard Evaluation Report 2010-0156-3196 Page 83

The Health Hazard Evaluation Program investigates possible health hazards in the workplace under the 

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Evaluation Program also provides, upon request, technical assistance to federal, state, and local agencies 

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The recommendations in this report are made on the basis of the findings at the workplace 

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This report is available at http://www.cdc.gov/niosh/hhe/reports/pdfs/2010-0156-3196.pdf.

Recommended citation for this report:

NIOSH [2013]. Health hazard evaluation report: evaluation of dermal exposure to polycyclic 

aromatic hydrocarbons in fire fighters. By Fent KW, Eisenberg J, Evans D, Sammons D, 

Robertson S, Striley C, Snawder J, Mueller C, Kochenderfer V, Pleil J*, Stiegel M*, Horn G†. 

Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control 

and Prevention, National Institute for Occupational Safety and Health, NIOSH HETA Report 

No. 2010-0156-3196.

*U.S. Environmental Protection Agency, Human Exposure and Atmospheric Sciences 

Division

†University of Illinois-Urbana/Champaign, Illinois Fire Service Institute
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