Health Hazard Evaluation Report 2015-0028-3330 Page 1

Evaluation of Wildland Fire Fighter Exposures 

during Fuel Reduction Projects

HHE Report No. 2015-0028-3330

March 2019

Jessica G. Ramsey, MS, CPE

Judith Eisenberg, MD, MS

Douglas Wiegand, PhD

Scott E. Brueck, MS, CIH 

Thomas W. McDowell, PhD
Page 2 Health Hazard Evaluation Report 2015-0028-3330

Contents

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

Abbreviations ..................................... iii

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

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

Results .................................................. 7

Discussion .......................................... 18

Conclusions........................................ 22

Recommendations............................. 23

Appendix A ........................................ 26

Appendix B ........................................ 32

References.......................................... 42

Acknowledgements........................... 47

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 2015-0028-3330 Page i

We evaluated wildland fire 

fighters exposures to noise, 

vibration, carbon monoxide, and 

wood dust during fuel reduction 

activities. We found evidence 

of high noise exposures and 

hearing loss, overexposures 

to vibration and symptoms 

that could be consistent with 

hand-arm vibration syndrome, 

overexposures to wood dust 

and possible wood dust allergy 

symptoms. We also found 

occasional excursions over 

occupational exposure limits. Fire 

fighters reported a strong safety 

climate and moderate job stress.

Highlights of this Evaluation

The Health Hazard Evaluation Program received a request from a state-based wildland 

fire management program. Employer representatives were concerned about potential 

exposures to hand-transmitted vibration, wood chipper dust, noise, and carbon monoxide 

related to chain saw and wood chipper use among wildland fire fighters. The requestors 

were also concerned about safety climate and job stress issues among wildland fire fighters. 

We conducted three site visits; pre- and post-fire season visits in 2015 in which informal 

interviews were conducted focusing on general medical issues, psychosocial factors, and job 

stress. A third visit occurred in April 2016 for sampling and questionnaire administration. 

What We Did

● We measured fire fighters’ exposures to carbon

monoxide and wood dust in the air for two shifts

during a fuel reduction project.

● We measured fire fighters’ noise exposures during

training exercises and a fuel reduction project.

● We measured fire fighters’ exposures to

hand-transmitted vibration during chain saw use.

● We asked fire fighters to complete a questionnaire

covering work history and symptoms associated

with wood dust, hand-arm vibration, carbon

monoxide, and noise exposures.

● We reviewed the hearing test results for 

69 fire fighters.

● We held confidential medical interviews with 56 

fire fighters about health symptoms, safety

climate, job stress, psychosocial factors at work,

and sleep. 

What We Found

● None of the fire fighters’ full-shift exposures to carbon monoxide were above occupational

exposure limits. However, their exposures were occasionally above the National Institute

for Occupational Safety and Health ceiling limit of 200 parts per million of air.

● Fire fighters’ exposures to wood dust in the air were sometimes higher than

occupational exposure limits. Some fire fighters reported asthma-like symptoms and

rashes, which could be related to exposure to wood dust.

● Fire fighters’ noise exposures when using or working near the chain saws or wood chippers

were above noise exposure limits. Hearing test results showed that some fire fighters had 

hearing threshold shifts. Some fire fighters were unsure/unaware of their hearing tests results.
Page ii Health Hazard Evaluation Report 2015-0028-3330

● During fuel reduction activities, fire fighters were exposed to hand-transmitted 

vibration levels from chain saws above the daily exposure limit value. Over 70% of 

fire fighters reported one or more symptoms that could be consistent with hand-arm 

vibration syndrome.

● Wildland fire fighters reported a strong safety climate, moderate job stress, favorable 

perceptions of various psychosocial factors at work, and decreased sleep quality at the 

end of the fire season.

What the Employer Can Do

● Reduce chain saw use to three hours or less during a work shift to reduce daily handtransmitted vibration exposures.

● Maintain chain saws to reduce carbon monoxide exhaust, wood dust, and handtransmitted vibration exposures.

● Talk to fire fighters about job demands and how they affect job stress, burnout, and 

job satisfaction.

● Ensure fire fighters receive adequate training on the importance of good sleep habits, 

the hazards associated with fatigue at work, and strategies for managing them.

● Encourage fire fighters who develop health symptoms related to work to get evaluated by 

their healthcare provider. 

● Require fire fighters to wear both insert ear plugs and ear muffs when operating and 

feeding the chipper. Improve communication of hearing test results to fire fighters.

● Require fire fighters to wear N95 filtering facepiece respirators when using chain 

saws during fuel reduction activities until wood dust exposures are reduced. Educate 

wildland fire fighters regarding health effects that may develop if sensitization to wood 

dust occurs.

● Include fire fighters required to wear respirators in a respiratory protection program.

What Fire Fighters Can Do

● Turn off powered equipment and seek medical attention if you experience headaches, 

dizziness, drowsiness, nausea, or tightness across the chest.

● Report work-related health symptoms, strains, and pain to your supervisor. Promptly 

seek medical attention from a healthcare provider for these symptoms. Be sure to tell 

them you are a wildland fire fighter. This will help your healthcare provider check for 

other possible work-related health issues.

● Use only hearing protection provided by the agency. Keep hearing protection clean or 

replace disposable earplugs when dirty. 

● Do not have facial hair (beards) that interferes with the sealing surface of respirators.
Health Hazard Evaluation Report 2015-0028-3330 Page iii

Abbreviations

ACGIH® American Conference of Governmental Industrial Hygienists

AL Action level

ANSI American National Standards Institute

ASHA American Speech-Language-Hearing Association

AV Anti-vibration

CFR Code of Federal Regulations

CO Carbon monoxide

COHb Carboxyhemoglobin

dB Decibel

dBA Decibels, A-scale

DEAV Daily exposure action value

DELV Daily exposure limit value

HAVS Hand-arm vibration syndrome

HPD Hearing protection device

Hz Hertz

IDLH Immediately dangerous to life and health

ISO International Organization for Standardization

m/s2 Meters per second squared

mg/m3 Milligrams per cubic meter

NIHL Noise-induced hearing loss

NIOSH National Institute for Occupational Safety and Health

OEL Occupational exposure limit

OSHA Occupational Safety and Health Administration

PEL Permissible exposure limit

ppm Parts per million

REL Recommended exposure limit

rms Root-mean-square

STS Standard threshold shift

TLV® Threshold limit value

TWA Time-weighted average

VWF Vibration white finger
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Health Hazard Evaluation Report 2015-0028-3330 Page 1

Introduction

Employer representatives of a state-based wildland fire management program were concerned 

about the potential exposures to vibration, wood dust, carbon monoxide (CO), and noise along 

with safety climate and job stress among wildland fire fighters. At the time of our visits, the 

facility had five state agency fire crews: two Hotshot crews (each with 23 members); an Initial 

Attack crew (21 members); an Engines crew (6 members); and a Handcrew (20 members). 

At the time of our visits, all crews completed fuel reduction projects when not engaged in fire 

suppression. Crews from this program participated in fuel reduction projects when not engaged 

in fire suppression or training. Aside from being a good forestry management practice, these 

projects protect developed areas against wildfires by removing fuel so that, if a wildfire occurs, 

it is more easily contained and suppressed [National Park Service 2017]. While completing 

projects, fire fighters worked in groups of two to thin trees, remove underbrush, and limb trees 

using handheld chain saws. Cut material was run through a wood chipper or piled and burned 

during the winter months. Projects consisted of either a local daily commute or camping field 

project completed during four 10-hour days. Crews could set up remote field camps and were 

subject to primitive living conditions. The crews took their fire fighting equipment to these 

camps and were on call for fire assignments as they arose. 

Crew definitions and job descriptions:

● Hotshot crew: highly skilled and specialized hand crews usually used in rugged terrain 

and difficult areas

● Hand crew: wildland and prescribed burns – construct fire lines, burnout and mop-up 

activities

● Initial attack crew: initial attack on a fire

● Engines crew: fire suppression using specialized fire engines and support activities

● Swamper: assist sawyers. Clear brush, limbs, and smaller trees

● Sawyer: saw timber – specialized training in cutting taller trees and those trees that 

have partially fallen and are in hazardous configurations

For more wildland fire information and definitions, see https://www.nwcg.gov/about-thenwcg-glossary-of-wildland-fire and https://firejobs.doi.gov/index.php?action=crews.

Wildland fire fighters engage in year-round activities to prevent or minimize spread of 

wildfires in addition to their role in containing active wildfires during the traditional March 

through October fire season. One of the primary activities for wildfire prevention is removing 

or reducing the amount of available vegetation that a wildfire could use as fuel. These fuel 

reduction activities may include removal of brush near structures, performing a controlled 

burn to create a “fuel free” zone around inhabited areas as a buffer, etc. Chain saws are a 

central tool used to complete many wildland fire fighter tasks including cutting down small 

trees, removal of fallen logs blocking access trails, or stripping limbs off logs so that they can 

be safely placed into a wood chipper, etc.

Use of chain saws, wood chippers, leaf blowers, and other power tools used by wildland 
Page 2 Health Hazard Evaluation Report 2015-0028-3330

fire fighters may place them at risk for exposure to hand-transmitted vibration, wood dust, 

CO, and noise. Even fire fighters not personally operating handheld power tools and wood 

chippers may be exposed to noise, CO, and wood dust by working nearby when those tools 

are in use. Since chain saws are such an important tool, all wildland fire fighters are required 

to complete the National Wildfire Coordinating Group S-212 Wildland Fire fighter Chain 

Saws course as part of their entry level training. Some wildland fire fighters, called sawyers, 

get additional specialty training to safely bring down taller trees and trees partially fallen that 

have “hung up” in hazardous configurations. The sawyer certification system has 3 levels: 

beginner, intermediate, and advanced. The higher the certification level, the larger the trees 

and the more complex configuration of trees certified individuals are qualified to handle. 

Sawyers often use chain saws with larger blades that require larger motors, which could 

result in higher noise, hand-transmitted vibration, and CO exposures.

We visited the facility headquarters at the beginning of the fire season in May 2015 and again 

at the end of the season in October 2015. During the first visit in May 2015, we conducted 

confidential medical interviews with fire fighters that covered work organization issues and 

occupational history. At the beginning of the season, most fire fighters were engaged in 

training activities, administrative tasks, and preparing for the season. When we visited at the 

end of the season, the fire fighters were engaged in season closeout procedures, making sure 

equipment was accounted for, and other administrative tasks. During the October 2015 visit, 

we conducted follow-up interviews on work organization issues to compare to pre-season. 

We released an interim report regarding safety climate, job stress, psychosocial factors at 

work, and sleep in May 2016. Overall, wildland fire fighter employees reported a strong 

safety climate, favorable perceptions of various psychosocial factors at work, and moderate 

job stress. Employees reported decreased sleep quality at the end of the season. The interim 

report can be found in Appendix B.

We returned in April 2016 to evaluate exposures during a fuel reduction project. During this 

visit, we evaluated CO, wood dust, noise, and hand-transmitted vibration. Fire fighters also 

completed questionnaires covering work history and current tasks. We sent the agency and 

fire fighters notification letters with exposure monitoring results for CO in May 2016, for 

wood dust in June 2016, and for noise in November 2017. 

Methods

The objectives of this health hazard evaluation were:

● Evaluate fire fighters’ exposures to CO, wood dust, noise, and hand-transmitted 

vibration to identify opportunities for exposure reduction.

● Determine if fire fighters had signs and/or symptoms of CO poisoning, wood dust 

allergy, hearing loss, or hand-arm vibration syndrome (HAVS) and if so, was there a 

relationship between these conditions and duration of work and/or specific tool use.

● Determine if fire fighters reported diagnoses of CO poisoning or wood dust allergy 

since starting work at this facility.
Health Hazard Evaluation Report 2015-0028-3330 Page 3

● Assess fire fighters’ perceptions of safety climate, job stress, and psychosocial factors at 

work and screen for sleep problems.

● Evaluate fire fighters’ self-reported average sleep duration, quality of sleep, and 

frequency of unintentional sleep episodes.

Carbon Monoxide

During the April 2016 site visit, we measured CO air concentrations in the breathing zone of 

fire fighters using direct reading BW Technologies GasAlert Extreme single gas meters. The 

instruments had a detection range of 0–1,000 parts per million (ppm) and data-logged CO 

measurements every 5 seconds. A brief description of occupational exposure limits (OELs) 

and health effects for CO is provided in Appendix A.

Wood Dust

We measured wood dust in the breathing zone of fire fighters during the April 2016 site visit 

using 37-millimeter diameter tared polyvinyl chloride filters with Accucap inserts. Air sampling 

pumps were calibrated to a flow rate of 2.0 liters per minute. Samples were analyzed using 

National Institute for Occupational Safety and Health (NIOSH) Method 0600 [NIOSH 2019]. A 

brief description of OELs and health effects for wood dust is provided in Appendix A.

Noise and Hearing Conservation

We measured fire fighters’ personal noise exposures during the April 2016 site visit using 

Larson Davis SparkTM model 706RC integrating noise dosimeters. The dosimeters integrated 

noise at a 50-hertz (Hz) sampling rate (50 measurements per second) and data-logged 

5-second averaged noise levels for the duration of the measurement period. Fire fighters wore 

dosimeters on their waistband, and we attached the dosimeter microphone on their outer 

clothing in an upright position midway between the neck and the edge of their shoulder. We 

covered the microphone with a windscreen to reduce artifact noise caused by the wind or 

by accidental bumping or rubbing. At the end of the work shift, we downloaded the noise 

measurement data from the dosimeters using the PCB Piezotronics BlazeTM software. 

The dosimeters simultaneously collected noise data using three different settings to allow 

comparison of noise measurement results with three different noise exposure limits, 

the NIOSH recommended exposure limit (REL), the Occupational Safety and Health 

Administration (OSHA) permissible exposure limit (PEL), and the OSHA action level (AL). 

Noise exposure limits are meant to be the amount of noise that most fire fighters can be 

exposed to without substantial risk of hearing loss. Additional information on noise exposure 

limits and health effects is provided in Appendix A.

We used Larson Davis Model 831 integrating sound level meters and frequency analyzers to 

measure sound levels and one-third octave band noise frequency levels (i.e., measurement of 

noise levels across 30 different frequencies). For most measurements we held the instrument 

or used a tripod at a height of approximately 5 feet above ground level and within 3–6 feet of 

the fire fighters or the primary noise source.
Page 4 Health Hazard Evaluation Report 2015-0028-3330

Figure 1. Sawyer cuts slices from logs while the vibration is measured at the hand-handle interface. 

Photo by NIOSH.

We evaluated chain saw vibrations by measuring the acceleration simultaneously at both 

handles in close proximity to where the vibration entered the operator’s left and right hands 

in accordance with the International Organization for Standardization (ISO) ISO 5349-2, 

2001 [ISO 2001b] and the American National Standards Institute (ANSI) ANSI S2.70-2006 

[ANSI 2006]. To examine how the frequency weighting affected the results, the chain saw 

vibrations were evaluated based on band-limited unweighted acceleration as well as by 

frequency-weighted acceleration, as recommended by NIOSH [NIOSH 1989]. Although leaf 

blowers and other handheld power tools may produce vibrations that can be transmitted up to 

the operator, the chain saw was the only tool for which a quantitative assessment of vibration 

was conducted for this evaluation. 

Figure 2 shows accelerometers mounted on the front and rear handles of one of the chain 

saws. All chain saw vibration measurements were collected via PCB Model 356B11 

piezoelectric tri-axial accelerometers. The accelerometers were installed on mounting 

blocks and secured to the handles with hose clamps. Additional details about the vibration 

measurements and data are provided in Appendix A.

We reviewed the hearing conservation program, including hearing protection, training, and 

audiometric testing. We obtained a print-out of audiograms from 2012 to 2015 for 69 current 

fire fighters. Audiometric testing had been completed yearly by an external provider. For fire 

fighters with a baseline and at least one subsequent audiogram, we assessed whether there 

was evidence of a hearing threshold shift, on the basis of OSHA and NIOSH criteria. 

Hand-transmitted Vibration from Chain Saws

During the April 2016 visit, we measured fire fighters’ exposures to hand-transmitted 

vibration during simulated fuel reduction operations. Two chain saw operators used four 

different Stihl® professional chain saw models to cut logs into slices as shown in Figure 1. 

Both operators were right-handed. The saws were used but well-maintained. Each operator 

completed five, 20-second sawing trials with each chain saw model.
Health Hazard Evaluation Report 2015-0028-3330 Page 5

Figure 2. White arrows point to the two tri-axial accelerometers used to measure the acceleration at the 

hand-handle interface for right hand (rear handle) and the left hand (front handle). Photo by NIOSH.

Medical Assessment

Confidential Medical Interviews

We held confidential interviews with all of the fire fighters on duty to assess safety climate, 

job stress, psychosocial factors at work, and sleep during the May (pre-season; n = 56) and 

October (post-season; n = 48) 2015 visits. Details about these methods and findings can be 

found in the interim report (provided in Appendix B) from May 2016. 

Questionnaire

During the May 2016 visit, all 93 wildland fire fighters of the 5 crews based at this facility were 

invited to complete a one-time paper questionnaire. The questionnaire covered work history as both 

paid and volunteer fire fighter, current crew assignment, power tool use, and tasks. The questionnaire 

also included screening questions for hearing loss, HAVS, wood dust allergy, and CO poisoning 

since starting work at this facility. The questionnaire also reviewed participant knowledge of annual 

audiometric testing conducted by this facility as part of its hearing conservation program. 

We assessed symptoms of hearing trouble in all participants with a set of 3 screening questions 

that were modified from others tools [National Center for Health Statistics 2014]. A positive 

response to the first question “Do you have trouble hearing/understanding when people speak 

to you in a room with background noise (i.e., other talking, TV, conversation in a restaurant, 

etc.)?”, was defined as mild hearing trouble. Positive answers to either or both of the second or 

third questions was defined as moderate hearing trouble. The second hearing screening question 

was “Do you have trouble hearing/understanding when people speak to you in a quiet room?” 

and the third question was “Do people often ask you to turn down the volume on the TV?”

We also analyzed a subset of the hearing questions among returning fire fighter participants. We 

defined a returning fire fighter as one who reported their total years as a fire fighter at this facility as 

≥ 1 year. We did this subset analysis to identify hearing trouble that could possibly be related to use 

of loud power tools commonly used in wildland fire fighting over more than a single fire season. 
Page 6 Health Hazard Evaluation Report 2015-0028-3330

We assessed symptoms that could be consistent with HAVS via a panel of screening 

questions derived from the British Hand Arm Vibration Initial Screening Questionnaire. 

This questionnaire is traditionally used to determine if an employee should be referred for 

additional testing in order to confirm a diagnosis of HAVS [Health and Safety Executive 

2018]. In our evaluation, fire fighters were defined as having symptoms that could be 

consistent with HAVS if they had a positive response to one or more of the following 

screening questions. All participants were asked if in the past year they ever:

● Had tingling of the fingers lasting more than 20 minutes after using vibrating 

equipment (i.e., chain saw or other power tools)?

● Had tingling of the fingers at any other time?

● Woke at night with pain, tingling or numbness in your hand or wrist?

● Had numbness in your fingers lasting more than 20 minutes after using a power tool?

● Had one or more of your fingers go numb more than 20 minutes after using vibrating 

equipment (i.e., chain saw or other power tools)?

● Had your fingers gone white on cold exposure?

● Had your fingers go white any other time?

● Had any other problems with the muscles or joints of the hands or arms?

● Had difficulty picking up very small objects (i.e., screws or buttons) or opening tight jars?

We used two screening questions that were derived from the European Community Respiratory 

Health Survey to evaluate participants for asthma [Grassi et al. 2003]. Participants were 

classified as having “asthma-like” symptoms if they answered positively to at least one of the 

screening questions. The screening questions were “Have you had wheezing or whistling in 

your chest at any time in the last 12 months?” and “Have you been woken up with a feeling of 

tightness in your chest at any time in the last 12 months?” Participants were asked to exclude 

symptoms that were present when they had a cold during this period. Additional questions were 

asked to determine possible work and wood dust relatedness of any asthma symptoms.

Exposure to wood dust may result in a rash in allergic individuals so participants were asked 

“In the past year, have you ever had a rash that started after handling wood?” CO exposure 

was assessed by asking participants if they had ever been diagnosed with CO poisoning since 

starting work at this facility or if they had experienced CO exposure related symptoms of 

headache, nausea/vomiting, lightheadedness/dizziness, or difficulty concentration while using 

gasoline or diesel powered equipment to perform job tasks.

We used SAS Version 9.3 (SAS Institute Inc.) for our statistical analyses. We calculated 

descriptive statistics including medians, ranges, frequencies, and percentages. A two-sample 

t-test was used to compare means for variables with normal distributions while the Wilcoxon 

two-sample test was used to compare means between variables that did not appear to have 

normal distributions. We compared mean age, years as a fire fighter, and use of various tools in 

the preceding 8 weeks of the second site visit for those with and without symptoms consistent 

with HAVS. These same tests were also used to compare mean age, mean years as a fire fighter, 
Health Hazard Evaluation Report 2015-0028-3330 Page 7

and mean hours of daily use of a chain saw and wood chipper for those returning fire fighters 

with and without hearing trouble and those with and without rash. To account for potential 

hearing trouble from proximity exposures, we also did similar comparison of HAVS symptom 

reports with fire fighter mean age and years worked as a fire fighter for those participants who 

did not report personally using power tools or equipment in the previous 8 weeks. P values 

less than 0.05 were considered statistically significant. For tests with significant P values, 

prevalence ratios with their 95% confidence interval limits were reported.

Results

Carbon Monoxide

Results of personal air sampling for CO are provided in Table 1. Fire fighters’ full-shift 

time-weighted average (TWA) exposures to CO were 2.5–9.6 ppm, which were well below 

full-shift OELs. However, each of the fire fighters had brief, intermittent CO exposures above 

the NIOSH ceiling limit of 200 ppm. The total time fire fighters exceeded the NIOSH ceiling 

ranged from 0.25–2.3 minutes. No fire fighter exceeded the NIOSH ceiling for more than 

25 seconds in any single occurrence of exceedance. No exposures were above the NIOSH 

immediately dangerous to life and health (IDLH) level of 1,200 ppm.

Table 1. Full-shift TWA personal air sampling results for CO, April 2016

Employee Sample 

duration

(minutes)

Range of 

exposure

(ppm)

Total time above 

NIOSH ceiling limit

(minutes)

Concentration

(ppm)

Fire fighter 1 – day 1 473 0–249 0.25 4.7

Fire fighter 2 – day 1 467 0–220 0.33 3.0

Fire fighter 3 – day 1 464 0–712 0.83 7.2

Fire fighter 4 – day 1 464 0–428 1.5 6.2

Fire fighter 5 – day 1 469 0–467 1.3 5.3

Fire fighter 1 – day 2 601 0–384 0.92 6.5

Fire fighter 2 – day 2 583 0–403 0.50 2.5

Fire fighter 3 – day 2 595 0–450 2.1 9.6

Fire fighter 4 – day 2 583 0–466 1.8 5.0

Fire fighter 5 – day 2 588 0–568 2.3 4.9

ACGIH TLV (8-hour TWA)

NIOSH REL (10-hour TWA)

NIOSH Ceiling

OSHA PEL (8-hour TWA)

25

35

200

50

ACGIH® = American Conference of Governmental Industrial Hygienists

TLV® = Threshold limit value
Page 8 Health Hazard Evaluation Report 2015-0028-3330

Figure 3. Time-history showing real-time CO measurement results for fire fighter 5 during day 2.

Wood Dust

Personal air sampling results for wood dust are provided in Table 2. One sample (fire fighter 

2 – day 2) was lost in the brush and debris during sample collection. Fire fighters’ exposures 

to wood dust in the air were 0.87–2.0 milligrams per cubic meter (mg/m3

). Six of the nine 

samples were above the NIOSH REL and ACGIH TLV of 1.0 mg/m3

. OSHA does not have 

a PEL specific for wood dust but compares exposures to their PEL of 15 mg/m3

 (inhalable 

fraction) for particles not otherwise regulated.

Figure 3 provides a time-history showing real-time CO exposures for fire fighter 5 on day 

2. Intermittent exposures can be seen exceeding the NIOSH ceiling limits. The highest 

exposures occurred when using the chainsaw (as seen in the fire fighter in Figure 3), but we 

noted a slight decrease in exposures when fire fighters rotated to the swamping task. Fire 

fighters had no CO exposures during breaks and lunch.
Health Hazard Evaluation Report 2015-0028-3330 Page 9

Table 2. Personal air sampling for wood dust, April 2016

Employee Sample 

duration

(minutes)

Concentration

(mg/m3

)

Fire fighter 1 – day 1 473 0.87

Fire fighter 2 – day 1 442 1.2

Fire fighter 3 – day 1 464 1.1

Fire fighter 4 – day 1 464 1.8

Fire fighter 5 – day 1 466 0.97

Fire fighter 1 – day 2 597 1.7

Fire fighter 3 – day 2 596 2.0

Fire fighter 4 – day 2 593 0.89

Fire fighter 5 – day 2 589 1.2

NIOSH REL

ACGIH TLV

OSHA PEL

1.0

1.0*

15†

*Wood dust, species other than western red cedar 

†Particulates not otherwise regulated (inhalable fraction)

Noise

Full shift personal noise exposure measurement results are provided in Table 3. All five 

fire fighters’ noise exposures were above the OSHA AL and NIOSH REL on both days of 

monitoring. All fire fighters, except fire fighter 2, were also exposed to noise above the 

OSHA PEL on one or both days of monitoring. Fire fighter 2 had supervisory duties and 

spent slightly less time using the chain saw compared to other fire fighters on the crew. 

Table 3. Fire fighters full-shift TWA personal noise exposures, May 2016

Employee Measurement 

duration 

(minutes)

Results based 

on OSHA AL

criterion (dBA)

Results based 

on OSHA PEL

criterion (dBA)

Results based 

on NIOSH REL 

criterion (dBA)

Fire fighter 1 – day 1 473 89.6 88.8 95.1

Fire fighter 2 – day 1 442 86.4 85.5 91.9

Fire fighter 3 – day 1 464 92.1 91.5 97.1

Fire fighter 4 – day 1 464 94.8 94.5 99.2

Fire fighter 5 – day 1 466 90.9 90.3 95.6

Fire fighter 1 – day 2 597 92.4 91.7 97.1

Fire fighter 2 – day 2 582 87.8 86.8 92.8

Fire fighter 3 – day 2 596 95.2 94.8 99.3

Fire fighter 4 – day 2 593 94.3 93.9 98.8

Fire fighter 5 – day 2 405 93.4 92.9 98.1

Noise exposure limits (8-hour work shift) 85.0 90.0 85.0

Noise exposure limits (10-hour work shift) 83.4 90.0 84.0

dBA = decibels, A-scale
Page 10 Health Hazard Evaluation Report 2015-0028-3330

Figure 4 provides the noise exposure time-history profile for fire fighter 5 on the second day 

of noise monitoring. While actively using the chain saw, noise exposure reached 110 dBA. 

Noise exposures during swamping were slightly less, reaching up to 100 dBA. 

Figure 4. Noise exposure time-history profile for fire fighter 5 during day 2. The line across the figure 

at 85 dBA denotes the NIOSH REL. 

The range of sound levels during chain saw use was 93.5–103.8 dBA (Table 4). We did not 

find a notable difference in sound levels between the different types of chain saws used by 

fire fighters: Stihl Rollomatic® ES Model 440, Stihl Model MS362, and Stihl Model MS461. 

Sound levels were slightly higher overall when cutting larger diameter logs versus cutting 

down small oak trees and serviceberry bushes or cutting brush piles. Sound levels near fire 

fighters engaged in swamping tasks were similar, ranging 91.8–99.8 dBA. 
Health Hazard Evaluation Report 2015-0028-3330 Page 11

Table 4. Task-based sound levels during chain saw use 

Task Number of 

measurements

Sound level 

(dBA)

Operator using chain saws 

to cut small oak trees or 

serviceberry bushes

5 93.5–99.8

Using chain saws to cut 

brush piles 

5 95.6–101.2

Using chain saw to cut 

oak logs

6 98.9–103.8

Swamping – nearby chain 

saw operator was cutting 

brush piles or small 

oak trees

3 91.8–99.8

Short duration personal noise exposure measurements were near or slightly above 100 dBA

(based on NIOSH measurement criterion) when trainees operated, fed, or pulled brush to 

the chipper (Table 5). Noise exposures ranged 88–94 dBA when trainees observed and used 

chain saws for short periods. However, the instructor’s noise exposure was below 80 dBA 

when instructing or observing trainees using a chain saw.

Table 5. Task-based personal noise exposures during training session activities, May 2016

Training activity Measurement 

duration 

(minutes)

Results based 

on OSHA AL

criterion (dBA)

Results based 

on OSHA PEL 

criterion (dBA)

Results based 

on NIOSH REL 

criterion (dBA)

Operating chipper 31 97.7 97.6 100.0

Feeding chipper 32 97.8 97.7 100.4

Pulling brush to chipper 29 97.2 97.1 99.5

Instructor: teaching and 

observing trainees using 

a chain saw 

122 67.9 21.7 74.9

Trainee 1: observing and 

using a chain saw

87 85.0 84.1 93.6

Trainee 2: observing and 

using a chain saw

92 84.2 83.4 93.0

Trainee 3: observing and 

using a chain saw

40 82.8 81.0 88.2
Page 12 Health Hazard Evaluation Report 2015-0028-3330

Hearing Conservation Program

All fire fighters were included in the agency’s hearing conservation program. Baseline and 

annual audiometric testing was done by an external audiometric test contractor via a mobile 

test van, typically in the fall. Prior to audiometric testing, the audiometric test contractor 

asked fire fighters several screening “yes/no” questions regarding current and permanent 

hearing history. Testing was done at the following audiometric frequencies 500, 1000, 2000, 

3000, 4000, 6000, and 8000 Hz. After testing, the contractor provided the fire fighter a 

summary of their test results and provided the agency a summary report of overall results and 

a print-out of individual audiometric test history results. 

The safety and health director and audiometric test provider conducted hearing conservation 

training. The safety and health director also did hearing protection fit testing using the 

FitCheck SoloTM system. Fire fighters were provided with a choice of five different types of 

insert type hearing protectors: 3MTM E-A-RsoftTM, 3M E-A-RTM ClassicTM SuperFitTM 33; 

Howard LeightTM Max®, Howard Leight Max Lite®, and Howard Leight FirmFit®. One 

of the fire fighters doing fuel reduction wore self-purchased banded earplugs, instead of the 

agency-provided plugs. We observed that these plugs were very dirty.

Hand-transmitted Vibration from Chain Saws

Table 6 presents the five-trial acceleration means for each of the saw operator/saw model 

combinations. The results for the two operators were similar. The acceleration measured at 

the right hand (rear handle) was consistently higher than that for the left hand (front handle). 

The average frequency-weighted acceleration value for the right hand was 8.4 meters per 

second squared (m/s2

). Chain saw model MS 440 exhibited the highest vibration at both 

hands for both operators. 

Table 6. Unweighted and frequency-weighted acceleration 

means for each operator and chain 

saw model

Unweighted 

(m/s2

)

Weighted 

(m/s2)

Sawyer Model Left Right Left Right

Operator 1 MS362 84.1 124.1 3.6 6.4

MS440 82.8 148.2 6.0 11.0

MS460 73.1 124.1 5.2 8.6

MS461 65.0 121.6 4.8 9.3

Operator 2 MS362 83.9 110.0 4.8 6.0

MS440 93.0 138.1 7.0 10.2

MS460 68.4 98.6 5.1 7.2

MS461 63.3 112.3 4.5 8.2
Health Hazard Evaluation Report 2015-0028-3330 Page 13

Table 7 presents the estimated times that an operator could use each saw during a work shift 

before reaching the ANSI S2.70 [ANSI 2006] daily exposure action value (DEAV) or daily 

exposure limit value (DELV). Because the exposures are higher for the rear handle than 

the front handle, these time values are based on the right-hand average frequency-weighted 

acceleration. The average time to reach the DEAV for the four saws was about 45 minutes. 

The average time to reach the DELV was less than 3 hours. 

Table 7. Estimated time an operator could use each 

chain saw model during a workshift before reaching DEAV 

and DELV

Saw Time to reach DEAV 

(hours)

Time to reach DELV 

(hours)

MS362 1.3 5.2

MS440 0.4 1.8

MS461 0.8 3.2

MS461 0.7 2.6

Medical Questionnaire

In total, 89 (96%) of 93 wildland fire fighters of the 5 crews based at this facility completed 

the medical questionnaire during the May 2016 site visit. All participants were male with 

a median age of 27 years (range: 19–42 years). The median number of total years worked 

at this facility was 3.6 years (range 1 day–13.3 years). Of the 89, 59 (66%) participants 

had worked at this facility for one or more years. This subset of participants are noted 

as returning fire fighters. Most participants’ fire fighting work history consisted solely of 

wildland fire fighting. Only 9 (10%) reporting any work history of structural fire fighting, 

ranging from 11 months to 6.25 years. In addition to the basic chain saw training, 38 (43%) 

participants reported having crew roles that required sawyer certification.

Participants reported that their median workday length in the preceding 8 weeks was 10 hours 

(range: 8–16 hours) and that the median number of consecutive days worked was 4 (range 4–18 

days). Participants were asked about the tools they used during their work in the past 8 weeks. 

Table 8 below shows the frequency and duration of use of various power tools commonly used 

in wildland fire fighting. Participants responding that they had used a specific tool were then 

asked to estimate the average hours that tool was used during a typical workday. Most (91%) 

participants reported use of at least one of the following power tools in the previous 8 weeks: 

chain saw, leaf blower, wood chipper, hand-held wood boring drill, brush cutter, or pole pruner. 
Page 14 Health Hazard Evaluation Report 2015-0028-3330

Table 8. Reported tool use 

Tool Number (%) of fire 

fighters who reported 

using tool [n = 89]

Median hours tool 

used during 

workday

Chain saw 66 (74) 4.0

Wood chipper 59 (66) 4.0

Leaf blower 16 (18) 1.0

Brush cutter 6 (7) 2.0

Hand drill 4 (5) 3.7

Pole pruner 0 Not applicable

Other* 15 (17) 4.0

*Other was a write-in category for tools not mentioned. 

Responses included non-powered hand tools such as the 

pulaski, slam, and combitool.

Hearing Loss

The questionnaire covered hearing protection device (HPD) use, hearing trouble as 

documented by positive responses to screening questions, and audiometric testing. The 

majority (94%) of participants reported always using HPDs while working while 6% 

reporting using their HPDs only sometimes. All participants reported ear plugs as their only 

HPDs. No fire fighters reported using ear muffs. Sixty-seven (75%) participants reported 

receiving formal training on the proper wear of HPDs since starting work at this facility. The 

hearing trouble screening questions responses showed that 49 (55%) participants reported 

no subjective hearing trouble, as defined by answering no to all 3 screening questions. We 

identified 14 (16%) participants as having mild hearing trouble and we identified 26 (29%) 

participants as having moderate hearing trouble. 

Seventy-one (80%) participants reported having had a hearing test (also known as an 

audiogram). Of those 71, the majority (86%) stated the hearing test was done as part of the 

facility’s hearing conservation program. No participants reported having a hearing test done 

because they were having trouble hearing. Of the 70 participants who answered the question 

regarding the findings of their previous hearing test, 34 (49%) stated the test did not show 

any hearing loss, 23 (33%) reported the test showed hearing loss, and 13 (19%) responded 

that they did not know what their test showed. 

For the subset of returning fire fighters, we did not find a significant relationship between 

subjective hearing trouble by questionnaire responses and total years worked as a fire fighter 

(P = 0.61) or age (P = 0.10). In addition, we did not find a statistically significant association 

between subjective hearing trouble and mean hours of chain saw use in the past 8 weeks 

(P = 0.92) or mean hours of wood chipper use (P = 0.82). We then included those who did 

not report any personal use of those two tools in the last 8 weeks to see if those working in 

the vicinity where these tools were being used were affected by their proximity even though 

they were not personally using these tools. We did not find a relationship between subjective 

hearing trouble and chain saw use (P = 0.55). However, we found that those who reported 
Health Hazard Evaluation Report 2015-0028-3330 Page 15

using a wood chipper in the previous 8 weeks were more likely to have subjective hearing 

trouble than those who did not use a wood chipper (54% vs. 23%, P = 0.03). 

We reviewed audiometry results for the 69 fire fighters tested in 2015, the most recent year 

test results were available. Of the 69 fire fighters with audiometry results, 27 only had a 

baseline audiogram, and 42 had a baseline and at least one annual audiogram. Of the 42 

with a baseline and an annual audiogram, one had an OSHA-defined standard threshold 

shift (STS); however, nine (21%) had a NIOSH-defined significant hearing threshold shift. 

Their median age was 26 years (range: 19–57) and 94% were male. One of these 69 fire 

fighters had a material hearing impairment as defined by NIOSH [NIOSH 1998], as well 

as severe hearing loss as defined by the American Speech-Language-Hearing Association 

(ASHA) [ASHA 2018]. In addition, three fire fighters had ASHA-defined moderately severe 

hearing loss and three had ASHA-defined moderate hearing loss. Of these six fire fighters, 

four reported moderate hearing trouble on the questionnaire, one reported mild hearing 

trouble, one reported no hearing trouble, and one did not complete a questionnaire. All six 

who completed the questionnaire reported using a chain saw in the previous 8 weeks and 

five of the six reported using the wood chipper in the previous 8 weeks. As part of their 

pre-screening process for the annual audiogram, fourteen (20%) of the 69 fire fighters 

subjectively reported during pre-screening of having ringing or roaring in the ears.

Hand-arm Vibration Syndrome Symptoms

HAVS can result from working with hand-held power tools. We asked about other medical 

conditions that can result in similar symptoms of upper extremity pain, numbness, tingling, 

or weakness. The most common of these conditions among participants was hand or wrist 

tendonitis reported by 16% of respondents. One participant each reported having diabetes, 

rheumatoid arthritis, trigger finger, and ganglion cyst. One participant had a prior diagnosis 

of vibration white finger (VWF), which can occur as part of HAVS. 

Ten questions covered signs and symptoms experienced in the past year. Sixty-five (73%) of 

participants answered yes to one or more of these symptom questions that could be consistent 

with HAVS. Fifty participants (56%) answered yes to two or more of the HAVS symptoms. 

All were recommended to obtain a follow-up evaluation by their healthcare provider for 

HAVS. Almost half (49%) of the participants reported having had pain, aching, stiffness, 

burning, numbness, or tingling in their hands or wrists. Forty-two (47%) participants reported 

being awoken at night with pain, tingling, or numbness in their hands or wrists and having 

tingling in their fingers not associated with power tool use. Table 9 lists all the HAVS 

screening questions and their responses.
Page 16 Health Hazard Evaluation Report 2015-0028-3330

Table 9. Responses to HAVS screening questions

Question Number (%) of participants 

reporting symptom in the past 

year [n = 89]

Pain, aching, stiffness, burning, numbness, or tingling in your 

hands/wrists

44 (49)

Tingling of the fingers at any other time (not within 20 minutes of 

using a power tool)

42 (47)

Awoken at night with pain, tingling or numbness in your hand or wrist 42 (47)

Tingling of the fingers lasting more than 20 minutes after using 

vibrating equipment (i.e. chain saw or other power tools)

32 (36)

Numbness in your fingers lasting more than 20 minutes after 

using a power tool

26 (29)

Had one or more of your fingers go numb more than 20 minutes 

after using vibrating equipment (i.e. chain saw or other power tools)

26 (29)

Had your fingers gone white on cold exposure 19 (21)

Had difficulty picking up very small objects (i.e., screws or 

buttons) or opening tight jars

14 (16)

Had your fingers go white any other time 10 (11)

Any other problems with the muscles or joints of the hands or arms 29 (33)

Of the 44 participants who reported pain, aching, stiffness, burning, numbness or tingling in 

their hands/wrists in the past year, 26 (59%) reported having these symptoms between once 

a week and once a month. When they had the symptom(s), the duration varied between less 

than an hour (32%), between 1–24 hours (34%), 25 hours to one week (27%), and greater than 

one week (9%). The discomfort was rated as mild (61%), moderate (30%), or not painful at 

all (9%). Twenty-nine (66%) participants noted they were using a chain saw at the time of first 

onset, and 3 (7%) reported not using any tool around the time of first onset. Eleven (25%) wrote 

in that they were using non-power tools such as the Pulaski, scraper, or combitool when their 

hand/wrist symptoms started. Two participants wrote in that the symptoms began as a result 

of non-work related trauma. Of the 44 with hand/wrist symptoms, most (64%) said work tasks 

made the hand/wrist problem worse, and half reported having had this hand/wrist problem in 

the past 7 days. Despite these frequent and recent symptoms, most (93%) reported not having 

seen a healthcare provider for this hand/wrist problem in the past year. None reported missing 

any work because of it, and only one reported requiring job transfer or task restriction due to 

the hand/wrist problem. All participants who reported symptoms that could be consistent with 

HAVS were advised to seek further evaluation by their healthcare provider.

We also analyzed the data for the 59 returning fire fighters to see if there was an association 

between reported HAVS symptoms and use of various tools in the preceding 8 weeks. 

We did not find a significant association between positive responses to the HAVS referral 

screening questions and use of a chain saw (P = 0.07), wood chipper (P = 0.84), brush cutter 

(P = 0.28), or hand drill (P = 0.62) in the previous 8 weeks. However, participants reporting 

one or more symptoms that could be consistent with HAVS were more likely to report use of 

a leaf blower in the previous 8 weeks than those without symptoms (75% vs. 25%, P = 0.02). 
Health Hazard Evaluation Report 2015-0028-3330 Page 17

Wood dust, Asthma, and Carbon Monoxide

Nine (10%) participants reported an existing diagnosis of asthma. All were diagnosed by a 

healthcare provider, and none reported worsening of their asthma since starting work as a 

fire fighter at this facility. Eight of those with a preexisting asthma diagnosis reported being 

diagnosed as children with only one participant reported being diagnosed as an adult. The 

majority of participants (84%) reported never having smoked. Twelve (13%) reported being 

former smokers, and only 2 (2%) identified as current smokers.

Of 88 participants who answered the asthma screening questions, 20 (23%) participants were 

classified as having asthma-like symptoms by answering yes to one or both of the asthma screening 

questions. Their responses are shown in Table 10. Two participants answered yes to both questions.

Table 10. Responses to asthma screening questions

Screening question Number of positive 

responses to the 

screening question 

(%) [n = 88]*

Have you had wheezing or whistling in 

your chest at any time in the last 

12 months?

15 (17)

Have you been woken up with a 

feeling of tightness in your chest at 

any time in the last 12 months?

9 (10)

*One participant did not answer the asthma screening

questions

Only 5 (56%) of the 9 participants with pre-existing asthma were among the 20 captured by 

the asthma screening questions. Of these 5, only one reported having an asthma attack in the 

past year. Of the 20 participants classified as having asthma-like symptoms, 16 were never 

smokers, 3 were former smokers, and 1 was a current smoker. All participants who reported 

these symptoms were advised to seek further evaluation by their healthcare provider.

Of 88 participants who responded to the question, 25 (28%) participants reported developing 

a rash after handling wood in the last year. The rashes were reported all over the body and 

not predominantly on hands/arms. Only 7 (28%) of the 25 participants who reported a rash 

with wood dust reported seeing a healthcare provider for it. Of these seven, six reported 

being diagnosed with either poison oak, poison ivy, or poison sumac while one was given a 

non-specific dermatitis diagnosis. We also found a significant positive association between 

increasing total years as fire fighter at this facility and reporting a rash related to wood dust 

exposure (P = 0.047). 
Page 18 Health Hazard Evaluation Report 2015-0028-3330

No participant reporting being diagnosed with CO poisoning since starting work at this 

facility. However, 33 (37%) of the 89 participants reported experiencing at least one 

symptom that could be consistent with CO poisoning while operating gasoline/dieselpowered equipment on the job. The most common symptom reported was headache (43%) 

followed by feeling dizzy or lightheaded (27%), difficulty concentrating (16%), and nausea 

and/or vomiting (10%).

Discussion

In our evaluation we tested crews in a single state. Other state crews may use other 

equipment and have different levels of maintenance. Other types of wildland fire fighters, 

such as smokejumper and helitak crews were not part of this assessment so our results may 

not be applicable to these type of wildland fire fighters. In addition, our survey questions 

about symptoms that could be consistent with asthma and HAVS are non-specific. The 

questions were not meant to be diagnostic, and fire fighters reporting symptoms were advised 

to seek additional medical evaluation.

Carbon Monoxide

During our evaluation, average CO air concentrations measured on fire fighters were well 

below full-shift exposure limits. Because the work is done outdoors, air movement typically 

disperses CO from chain saw exhaust relatively quickly. However, all fire fighters had brief 

peak CO exposures exceeding the NIOSH ceiling limit. These elevated exposures were never 

more than 25 seconds in length during a single occurrence and occurred due to position of the 

fire fighter relative to prevailing wind currents, which at times would carry chain saw exhaust 

directly toward the fire fighter. CO may not diffuse when the air is still in the working 

environment [Hooper et al. 2017]. At times, fire fighters may be able to position themselves, 

relative to wind direction, so that exhaust blows away from them, but this may not always 

be possible, depending on safety considerations such as the lean of the tree they need to 

fell. We did not find differences in CO concentrations between the different chain saws, 

but researchers have measured higher levels of CO when chainsaws were running at high 

revolutions per minute [Lipoglavsek 2000]. None of the fire fighters reported CO poisoning, 

but some reported non-specific symptoms that could be consistent with CO exposures such as 

headaches and lightheadedness. Chronic exposures to low ambient CO concentrations have 

been reported to affect multiple body systems, and CO is one of the most common exposures 

encountered by fire fighters when responding to wildland fires. It is important to consider that 

wildland fire fighters may also be exposed to CO from burning materials during an actual fire 

response and when setting prescribed burns for fuel reduction projects.

Wood Dust

Air sampling results showed that fire fighters exposures to wood dust were above the 

NIOSH and ACGIH recommended OEL of 1.0 mg/m3

. These exposures were similar to 

those measured in forestry workers in central Italy using chain saws [Marchi et al. 2017]. 

During our site visit, fire fighters were primarily cutting small oak trees; however, the kinds 

of trees or bushes fire fighters cut during fuel reduction can vary by location. We observed 
Health Hazard Evaluation Report 2015-0028-3330 Page 19

that at times, depending on prevailing wind speed, direction, and fire fighter position when 

using the chain saw, wood dust would blow toward fire fighters as they were cutting trees 

or brush piles. When possible, fire fighters should position themselves so that dust blows 

away from them. However, as noted above, it may not be possible or safe for fire fighters to 

always position themselves upwind when using the chain saw to cut trees or brush. Although 

respirators are not widely used by the wildland fire fighting community as a whole, their use 

could be considered until wood dust exposures are reduced further. 

NIOSH classifies all wood dust as a potential occupational carcinogen. ACGIH classifies 

wood dust from oak and beech as confirmed human carcinogens; birch, mahogany, teak, and 

walnut as suspected human carcinogens; and considers all other woods as not classifiable 

as human carcinogens. The International Agency for the Research on Cancer has also 

determined that there sufficient evidence that wood dusts are human carcinogens associated 

with the development of cancers in the nose, paranasal sinuses, and the nasopharynx 

[International Agency for Research on Cancer 2012]. Because of the cancer risk from 

exposures to wood dust, efforts should be made to reduce exposures to as low as feasible. 

In addition, wood dust exposure has been associated with the development of asthma and 

allergic contact dermatitis [Estlander et al. 2001; Perez-Rios et al. 2010]. Many different 

tree species have been implicated in both the development of asthma and allergic contact 

dermatitis among workers exposed to wood dusts. However, individual reaction may differ 

widely depending on tree species. Our questionnaire revealed 20 fire fighters with a possible 

asthma-like symptoms, but only five of these respondents had a pre-existing history of 

asthma. Therefore, it is possible that wood dust overexposure may be contributing to these 

symptoms. Further pulmonary evaluation is needed on these fire fighters to determine if they 

show objective evidence of asthma and if so, what exposures may trigger their asthma. 

Aside from CO, wildfire smoke contains particulates of 2.5 microns in diameter, 

polyaromatic hydrocarbons, and levoglucosan, a product of combustion of cellulose. Several 

studies have shown that these products of wood combustion may decrease lung function in 

wildland fire fighters across fire seasons [Adetona et al. 2013; Gaughan et al. 2014; Hagberg 

et al. 1985; Harrison et al. 1995]. The extent to which of these specific factors may impact 

lung function may vary between individuals. It important that healthcare providers are aware 

of the multiple factors that may contribute to new onset asthma and/or decreases in lung 

function in wildland fire fighters. These factors should be included in an assessment of new 

work-related asthma symptoms. The U.S. Forest Service, the National Park Service, and 

other U.S. agencies have stood up the Wildland Fire Air Quality Response Program (https://

wildlandfiresmoke.net) that issues air quality alerts using data from incident command, the 

National Oceanic and Atmospheric Administration, and other partners to create messages for 

residents of communities surrounding actively burning wildfires and those among the likely 

smoke distribution area. These alerts can and should be used by fire fighters themselves to 

be aware of ongoing exposures from the fires that may compromise their respiratory system. 

Aside from its potential impact on the respiratory system, wildland fire fighters should also 

be aware that chronic low level CO exposure may also have deleterious effects on the heart, 

possibly resulting in chest pain and/or irregular heartbeat [EPA 2016].
Page 20 Health Hazard Evaluation Report 2015-0028-3330

Noise and Hearing Conservation

In our evaluation, fire fighters’ noise exposures were well above the NIOSH REL and OSHA

AL during fuel reduction activities. We found that noise levels and exposures during sawing

were slightly higher than during swamping and were also higher when sawing larger diameter

trees compared to brush or small diameter trees. Full-shift exposures will vary on the basis of the

amount of time spent sawing and cutting larger diameter trees, and may exceed full-shift TWA

of 100 dBA, depending on the relative ratio of each. Noise exposures that we measured during

training exercises near the chipper were at or above 100 dBA. We expect that full-shift TWA noise

exposure under typical daily use of the chipper would also be similar. At an exposure of 100 dBA,

the NIOSH REL is exceeded in 15 minutes, and the OSHAAL is exceeded in 60 minutes. NIOSH

recommends use of both ear plugs and ear muffs when noise exposures are above 100 dBA. 

Only one of the 42 fire fighters with completed baseline and annual audiograms showed an OSHAdefined STS, but nine showed a NIOSH-defined significant hearing threshold shift. NIOSH 

recommends, as good practice, that employees with annual audiograms showing a significant 

hearing threshold shift be immediately retested to verify the shift and, if verified, re-tested again 

within 30 days to confirm the shift. Because confirmation testing of audiometric results was not 

completed, some of these NIOSH threshold shifts may have not persisted. However, these results 

indicate that audiometric test results should be evaluated using NIOSH criteria, in addition to 

OSHA criteria, to identify hearing thresholds shifts. The greater sensitivity of the NIOSH criteria 

provides an opportunity for early intervention to prevent progression of hearing loss. 

Our review of audiometric test results for 69 fire fighters showed that 10% met the ASHA 

definition for moderate, moderately severe, or severe hearing loss [ASHA 2018]. In contrast, 

we identified a much higher percentage (29%) of the NIOSH questionnaire respondents as 

having moderate hearing trouble. The higher percentage of self-reported hearing trouble 

compared to those with hearing loss identified by audiogram may be partially due to 

subjectivity of self-reported responses compared to audiometric measurements. Rosso et al. 

[2011] found that the sensitivity of a hearing loss questionnaire in detecting noise-induced 

hearing loss (NIHL) was 29%.

Prior to baseline and annual audiograms, the audiometric test provider does brief medical and 

audiometric history pre-screening of each fire fighter. Fourteen (20%) of the 69 fire fighters 

subjectively reported during pre-screening of having ringing or roaring in the ears. Ringing or 

roaring in the ears in the absence of external noise is a common symptom of tinnitus, which can 

be permanent or temporary in nature. NIOSH research indicates that, among workers reporting 

exposure to loud noise, the prevalence of tinnitus was 15% [Masterson et al. 2016]. Research 

has shown that tinnitus can occur in those with normal hearing [Schaette and McAlpine 2011]. 

However, tinnitus tends to increase with age and occur more commonly in workers who also 

have hearing loss. The average age of these 14 fire fighters was 26 years (range: 21–31 years). 

Only one had ASHA-defined severe hearing loss, and another had moderately severe hearing 

loss. We did not have information on whether follow-up questions regarding occurrence, 

persistence, or extent of ringing in the ears were asked. Therefore, it is difficult to interpret the 

implications of these reported tinnitus symptoms. During future audiometric testing, additional 

evaluation should be done when fire fighters report tinnitus symptoms. 
Health Hazard Evaluation Report 2015-0028-3330 Page 21

The fire fighters’ exposures to CO could also potentially affect hearing loss. In laboratory 

animals, research has shown that CO can worsen NIHL [EU-OSHA 2009]. In addition, the 

combined exposure to noise and CO was shown to cause hearing threshold shifts where 

exposure to either alone did not cause threshold shifts. Analysis of a Quebec National Public 

Health Institute database of 1,031 workers showed that workers exposed to CO and noise 

greater than 90 dBA had worse hearing (particularly at frequencies of 3, 4, and 6 kHz) than 

workers exposed to similar noise alone [Johnson and Morata 2009]. The potential risk of 

hearing loss from combined exposure to noise and CO highlights the importance of reducing 

exposures to each and using hearing protection. 

Hand-transmitted Vibration

Prolonged exposure to hand-transmitted vibration is associated with a series of disorders 

in the vascular, sensorineural and musculoskeletal structures of human fingers-hand-arm 

system, which has been collectively called HAVS [Gemne and Taylor 1983]. Because 

blanching along with tingling and numbness in the fingers is a typical symptom of HAVS, 

VWF is also used to refer the vibration-induced disorders in the fingers and the hand. In our 

evaluation, 73% of participating fire fighters reported one or more symptom that could be 

consistent with HAVS. We also found a significant positive association between reporting 

HAVS symptoms and use of a leaf blower in the previous 8 weeks. Leaf blower use should 

also be limited to the lowest possible levels. Routine tool maintenance should include 

inspection of leaf blower blades and assessment of leaf blower motor operation, as these are 

the most common sources of increased tool vibration.

We did not find an association between symptoms that could be consistent with HAVS and 

use of a chain saw in the previous 8 weeks. Nevertheless, vibration exposure has 

been associated with the development of musculoskeletal disorders among chain saw 

operators [Bovenzi 2008; Sutinen et al. 2006]. The average frequency-weighted chain saw 

acceleration measurements in these evaluations (8.4 m/s2

) is at the upper end of the range 

(5.9–8.8 m/s2

) reported for common chain saws on the European Union market [Griffin et 

al. 2006]. Career forestry workers with vibration exposures in this range have been reported 

to show prevalence rates of VWF of up to 50% [Bovenzi 1995]. In an effort to reduce the 

vibration exposures to chain saw operators, tool manufacturers have developed anti-vibration 

(AV) chain saw models. These saws have been reported to exhibit frequency-weighted 

accelerations in the range of 1.8–2.2 m/s2

 [Sutinen et al. 2006]. However, even operators 

using these modern, AV chain saw models can still exhibit VWF prevalence rates of more 

than 10% after just a few years of forestry work [Bovenzi 2008; Sutinen et al. 2006]. This 

suggests that there are no completely safe levels of chain saw vibration exposure; chain saw

vibration exposures should be limited to the lowest possible levels. 

ANSI has established the ANSI S2.70 standard [ANSI 2006] for the measurement and 

evaluation of hand-transmitted vibration exposures. This standard prescribes a DEAV of 

A(8) = 2.5 m/s2

. According to the standard:

The DEAV represents the health risk threshold to hand-transmitted vibration. 

For the purpose of this standard, health risk thresholds defined as the dose of 
Page 22 Health Hazard Evaluation Report 2015-0028-3330

hand-transmitted vibration exposure sufficient to produce abnormal signs, symptoms, 

and laboratory findings in the vascular, bone or joint, neurological, or muscular 

systems of the hands and arms in some exposed individuals.

The standard further states that when the DEAV is exceeded, “a program to reduce worker 

exposure to hand-transmitted vibration should be initiated to reduce health risks.” The ANSI 

standard [ANSI 2006] has also established a DELV of A(8) = 5.0 m/s2

. Workers exposed to 

hand-transmitted vibration at or above the DELV “are expected to have a high health risk.” 

The standard recommends that workers not be exposed to vibrations above the DELV. The 

standard provides guidance for a program to reduce worker exposure to hand-transmitted 

vibration in Annexes B and C of the standard; guidance applicable to chain saw operators are 

presented in the recommendations section below.

It is not known if the chain saws used in these evaluations are representative of their 

respective models. Caution should be used when comparing the vibration emissions of saw 

models based on such a small sample size. Saw model comparisons based on the results of 

these limited evaluations may not be appropriate. Likewise, it is not known if the sawing 

tasks observed in these evaluations are appropriate representations of sawing tasks performed 

by fire fighters during a typical work shift. Vibration exposures during actual work shifts may 

be higher or lower than those observed in these evaluations.

It is well known that tool maintenance is a significant factor that can influence the amount of 

vibration transmitted to the operator. Proper saw maintenance and chain sharpening can help 

limit hand-transmitted vibration exposure. The saws and chains used during these evaluations 

were not new, but all units appeared to be well-maintained. However, the ages and hours 

of use logged on each tool was unknown. It could be that the levels of vibration measured 

during these evaluations reflected the age and the amount of use that had been logged on each 

particular saw and/or chain; brand new saws and chains might have yielded different results. 

However, these saws were randomly selected from the group of saws that are regularly used 

by these fire fighters. Therefore, the acceleration averages of the four saws evaluated are 

likely to be fairly typical of what would be observed during similar sawing tasks in the field.

Recent studies suggest that while some AV gloves can significantly reduce vibrations 

to the palm, AV gloves reduce chain saw vibrations to the fingers by an average of just 

4% [Welcome et al. 2016]. Some glove designs may even amplify chain saw vibrations 

transmitted to the fingers. Because thicker gloves, such as AV gloves, can increase the 

grip effort required to operate and maneuver a saw, their use could lead to fatigue or other 

ergonomic issues [Hewitt et al 2015; Wimer et al. 2010]. Increased grip strength may be a 

separate contributing risk factor for both carpal tunnel syndrome and HAVS.

Conclusions

Our evaluation found that fire fighters at this site are overexposed to CO, wood dust, noise, 

and vibration. Although average CO concentrations measured on fire fighters were low, peak 

exposures exceeded relevant OELs. Combined exposure to noise with CO exposure can 

worsen the resultant hearing loss, highlighting the importance of reducing exposures to both. 

Several fire fighters reported symptoms that could be consistent with work-related asthma. 
Health Hazard Evaluation Report 2015-0028-3330 Page 23

In total, 73% of participating fire fighters reported one or more symptoms that could be 

consistent with HAVS. On the basis of the chain saw vibration measurements during this 

evaluation, an operator could be expected to reach a hand-transmitted vibration dose at the 

ANSI S2.70 DEAV in less than two hours of saw operation during a work shift. For some 

saws, the ANSI DELV could be exceeded in that amount of time. According to the ANSI 

standard and research on occupational chain saw vibration exposures, prolonged exposures 

to hand-transmitted vibrations at the levels observed in these evaluations may put the saw 

operators at risk of developing symptoms of HAVS. 

Recommendations

On the basis of our findings, we recommend the actions listed below. We encourage the fire 

management facility to use a labor-management health and safety committee or working group to 

discuss our recommendations 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 at this facility.

Our recommendations are based on an approach known as the hierarchy of controls 

(Appendix A). This approach groups actions by their likely effectiveness in reducing or 

removing hazards. In most cases, the preferred approach is to eliminate hazardous materials 

or processes and install engineering controls to reduce exposure or shield fire fighters. Until 

such controls are in place, or if they are not effective or feasible, administrative measures and 

personal protective equipment may be needed. 

Engineering Controls

Engineering controls reduce fire fighters’ exposures by removing the hazard from the process 

or by placing a barrier between the hazard and the employee. Engineering controls protect fire 

fighters effectively without placing primary responsibility of implementation on the employee. 

1. Select chain saw models and leaf blowers that are of good ergonomic design, that have 

been shown to produce reduced hand-transmitted vibration exposures, and that are 

appropriately sized for the task.

2. Sharpen chains often and maintain the saws in accordance with the manufacturers’

specifications. Poorly-maintained saws can generate increased vibrations, noise, CO, 

and wood dust exposures.

3. Consult the manufacturer of the wood chipper to determine if it can be retrofitted with 

any noise controls. 

Administrative Controls

The term administrative controls refers to employer-dictated work practices and policies 

to reduce or prevent hazardous exposures. Their effectiveness depends on employer 

commitment and employee acceptance. Regular monitoring and reinforcement are necessary 

to ensure that policies and procedures are followed consistently.

1. When reviewing audiograms to identify hearing threshold shifts, use NIOSH threshold 

shift criteria in addition to OSHA threshold shift criteria. Also, improve notification 
Page 24 Health Hazard Evaluation Report 2015-0028-3330

letter language to increase fire fighter understanding of their test results. The letter 

should use plain language such as “Your hearing test shows your hearing was normal” 

or “Your test shows you have mild, moderate, or severe hearing loss.”

2. Assess fire fighters reporting tinnitus symptoms to determine occurrence, persistence,

and extent of symptoms and whether additional audiology follow-up is needed.

3. Limit the duration of and intensity of hand-transmitted vibration exposure. Design

the work and work schedules so that the chain saw operator’s daily hand-transmitted

vibration exposures remain below the ANSI S2.70 time- and frequency-weighted

DELV of 5.0 m/s2

.

4. Employ a rotation schedule that rotates fire fighters between tasks during a work shift

and includes extended periods of no vibration exposure. One option is for fire fighters

to work in teams of two or more; one operates the saw and the other manages the

cuttings, performs saw/chain maintenance, and so on. At prescribed intervals, such as

the emptying of a fuel tank, the team members should swap tasks. In this fashion, the

vibration exposure is distributed more evenly among the team members during the

shift which lessens the chance of overexposure.

5. Avoid awkward sawing postures and unnecessary static loads related to the weight of

the saws.

6. Provide adequate training to instruct chain saw operators on the proper use and

maintenance of the saws and chains to increase safety and to reduce exposure to handtransmitted vibration.

7. Educate fire fighters about the sources and conditions that may result in CO and wood

dust exposures, with emphasis on actions which may help reduce exposures.

8. Encourage fire fighters to report work-related health symptoms, strains, and pain to

their supervisor and promptly seek medical attention from a healthcare provider for

those symptoms.

Personal Protective Equipment 

Personal protective equipment is the least effective means for controlling hazardous 

exposures. Proper use of personal protective equipment requires a comprehensive program 

and a high level of employee involvement and commitment. The right personal protective 

equipment must be chosen for each hazard. Supporting programs such as training, changeout schedules, and medical assessment may be needed. Personal protective equipment should 

not be the sole method for controlling hazardous exposures. Rather, personal protective 
Health Hazard Evaluation Report 2015-0028-3330 Page 25

equipment should be used until effective engineering and administrative controls are in place.

1. Require fire fighters to get medically cleared, fit tested for, trained on, and then wear 

N95 filtering facepiece respirators until wood dust exposures during fuel reduction 

activities can be reduced. Ensure that fire fighters do not have beard growth that 

interferes with the sealing surface of respirators.

2. Follow the OSHA respiratory protection standard, 29 CFR 1910.134, for a 

comprehensive respiratory protection program. Utah follows the federal standard 

through their state-based program. Information from NIOSH can also help in 

developing an effective respirator program. 

See http://www.cdc.go/niosh/topics/respirators/. 

3. Require use of both ear plugs and ear muffs when operating and feeding the chipper.

4. Ensure that fire fighters only use agency provided hearing protection and keep the 

hearing protection clean or replace disposable earplugs, when necessary.

5. Provide appropriate gloves to protect the hands and to keep them warm and dry. In 

addition to protection afforded by regular work gloves, AV gloves are designed to 

reduce hand-transmitted vibration exposures. However, the effectiveness of AV gloves 

is tool-specific. Therefore, users should contact the glove supplier or manufacturer 

to determine which glove models are appropriate for use with chainsaws and other 

equipment.
Page 26 Health Hazard Evaluation Report 2015-0028-3330

Appendix A: 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 TWA exposure. A TWA refers to the average exposure during 

a normal 8- to 10-hour workday. Some chemical substances and physical agents have 

recommended short-term exposure limit or ceiling values. Unless otherwise noted, the shortterm exposure limit is a 15-minute TWA 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 OSHA 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 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.

● Another set of OELs commonly used and cited in the United States is the ACGIH

TLVs. The TLVs are developed by committee members of this professional

organization from a review of the published, peer-reviewed literature. TLVs are not

consensus standards. They 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 2019]. 
Health Hazard Evaluation Report 2015-0028-3330 Page 27

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/GESTIS/GESTIS-Internationale-Grenzwerte-für-chemischeSubstanzen-limit-values-for-chemical-agents/index-2.jsp, contains international limits for 

more than 2,000 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.

Carbon Monoxide

CO is a colorless, odorless, tasteless gas produced by incomplete burning of carbon-containing 

materials; e.g., gasoline. The initial symptoms of CO poisoning may include headache, 

dizziness, drowsiness, and nausea. These initial symptoms may advance to vomiting, loss of 

consciousness, and collapse if prolonged or high exposures are encountered. Coma or death 

may occur if high exposures continue. Exposure to CO limits the ability of the blood to carry 

oxygen to the tissues by binding with the hemoglobin to form carboxyhemoglobin (COHb) 

[ACGIH 2001; NIOSH 1972, 1977, 1979, 2010; Proctor et al. 1988]. 

The NIOSH REL for CO is 35 ppm for an 8-hour TWA exposure, with a ceiling limit of 200 

ppm, which should not be exceeded [NIOSH 2010]. The NIOSH REL is designed to protect 

workers from health effects associated with COHb levels in excess of 5% [NIOSH 1972]. 

The ACGIH recommends a TLV of 25 ppm as an 8-hour TWA, and this is designed to protect 

workers from health effects associated with COHb levels in excess of 3.5% [ACGIH 2001]. 

The OSHA PEL for CO is 50 ppm for an 8-hour TWA exposure (29 CFR 1910.1000). 
Page 28 Health Hazard Evaluation Report 2015-0028-3330

Wood Dust

Wood dust exposure may cause eye and skin irritation and respiratory effects. In industrial 

settings, certain hard woods, such as oak, maple, and walnut, have been linked to nasal 

cancer [Proctor et al. 1991]. Loggers and persons involved in initial wood processing are 

exposed to irritant chemicals found in the bark or sap in the outer part of the tree. They 

are most affected by primary irritant dermatitis, which consists of erythema and blistering 

[Proctor et al. 1991]. The adverse health effects that have been associated with exposure to 

wood dust upon which evaluation criteria are based include dermatitis, allergic respiratory 

effects, and mucosal and nonallergenic respiratory effects.

NIOSH recommends that wood dust be considered a potential occupational carcinogen and that 

exposures be reduced to the lowest feasible level, not to exceed the REL of 1 mg/m3

 for both 

soft and hard woods [NIOSH 2010]. ACGIH has a TLV of 0.5 mg/m3

 for Western Red Cedar 

and 1 mg/m3

 for all other species [ACGIH 2018]. There is currently no specific OSHA PEL for 

wood dust. The OSHA PEL for total particulate not otherwise regulated is 15.0 mg/m3

 and 

5.0 mg/m3

 for the respirable fraction, determined as 8-hour averages (29 CFR 1910.1000).

Noise

NIHL is an irreversible condition that progresses with noise exposure. It is caused by damage 

to the nerve cells of the inner ear and, unlike some other types of hearing disorders, cannot 

be treated medically [Berger et al. 2003]. More than 22 million U.S. workers are estimated 

to be exposed to workplace noise levels above 85 dBA [Tak et al. 2009]. NIOSH estimates 

that workers exposed to an average daily noise level of 85 dBA over a 40-year working 

lifetime have an 8% excess risk of material hearing impairment. This excess risk increases to 

25% for an average daily noise exposure of 90 dBA [NIOSH 1998]. NIOSH defines material 

hearing impairment as an average of the hearing threshold levels for both ears that exceeds 

25-decibel (dB) at frequencies of 1000 Hz, 2000 Hz, 3000 Hz, and 4000 Hz.

Although hearing ability commonly declines with age, exposure to excessive noise can increase 

the rate of hearing loss. In most cases, NIHL develops slowly from repeated exposure to noise 

over time, but the progression of hearing loss is typically the greatest during the first several 

years of noise exposure. NIHL can also result from short duration exposures to high noise 

levels or even from a single exposure to an impulse noise or a continuous noise, depending 

on the intensity of the noise and the individual’s susceptibility to NIHL [Berger et al. 2003]. 

Noise exposed workers can develop substantial NIHL before it is clearly recognized. Even mild 

hearing losses can impair one’s ability to understand speech and hear many important sounds. 

In addition, some people with NIHL also develop “tinnitus.” Tinnitus is a condition in which 

a person perceives hearing sound in one or both ears, but no external sound is present. Persons 

with tinnitus often describe hearing ringing, hissing, buzzing, whistling, clicking, or chirping 

like crickets. Tinnitus can be intermittent or continuous and the perceived volume can range 

from soft to loud. Currently, no cure for tinnitus exists. 

The preferred unit for reporting noise measurements is dBA. A-weighting is used because it 

approximates the “equal loudness perception characteristics of human hearing for pure tones 
Health Hazard Evaluation Report 2015-0028-3330 Page 29

relative to a reference of 40 dB at a frequency of 1,000 Hz” and is considered to provide a 

better estimation of hearing loss risk than using unweighted or other weighting measurements 

[Berger et al. 2003]. NIOSH has an REL for noise of 85 dBA, as an 8-hour TWA. The OSHA 

noise standard specifies a PEL of 90 dBA and an AL of 85 dBA, both as 8-hour TWAs. 

Exposure to impulsive noise should never exceed 140 dBA.

For noise exposure measurements, NIOSH uses an 80 dBA threshold and a 3-dB exchange 

rate. Noise below the threshold level is not integrated by the noise dosimeter during 

measurements. The exchange rate expresses how much the sound level could increase 

or decrease while keeping the risk of hearing loss the same, if the exposure duration was 

simultaneously decreased or increased. For example, a 3-dB exchange rate requires that 

noise exposure time be halved for each 3-dB increase in noise levels. NIOSH considers noise 

measured using the 3-dB exchange rate to more accurately relate noise exposures to hearing 

loss risk [NIOSH 1998]. Using this criterion, an employee can be exposed to 88 dBA for no 

more than 4 hours, 91 dBA for 2 hours, 94 dBA for 1 hour, 97 dBA for 0.5 hours, etc. For 

extended work shifts, NIOSH adjusts the REL to 84.5 dBA for a 9-hour shift, 84.0 dBA for 

a 10-hour shift, 83.6 dBA for an 11-hour shift, and 83.2 dBA for a 12-hour work shift. When 

noise exposures exceed the REL, NIOSH recommends the use of hearing protection and 

implementation of a hearing loss prevention program [NIOSH 1998]. 

OSHA uses a 90 dBA threshold and a 5-dB exchange rate for the PEL measurements and 

an 80 dBA threshold and 5-dB exchange rate for the AL measurements. Using the OSHA 

criterion, an employee may be exposed to noise levels of 95 dBA for no more than 4 hours, 

100 dBA for 2 hours, 105 dBA for 1 hour, 110 dBA for 0.5 hours, etc. OSHA does not adjust 

the PEL for extended work shifts. However, the AL is adjusted to 84.1 dBA for a 9-hour shift, 

83.4 dBA for a 10-hour shift, 82.7 dBA for an 11-hour shift, and 82.1 dBA for a 12-hour 

work shift. OSHA requires implementation of a hearing conservation program when noise 

exposures exceed the AL [29 CFR 1910.95]. 

Workers exposed to noise should have baseline and yearly hearing tests to evaluate their 

hearing thresholds and determine whether their hearing has changed over time. Hearing 

testing should be done in a quiet location, such as an audiometric test booth where 

background noise does not interfere with accurate measurement of hearing thresholds. In 

workplace hearing conservation programs, hearing thresholds must be measured at 500 Hz, 

1000 Hz, 2000 Hz, 3000 Hz, 4000 Hz, and 6000 Hz. Additionally, NIOSH recommends that 

8000 Hz should also be tested [NIOSH 1998]. The OSHA hearing conservation standard 

requires analysis of changes from baseline hearing thresholds to determine if the changes 

are substantial enough to meet OSHA criteria for a STS. OSHA defines a STS as a change in 

hearing threshold relative to the baseline hearing test of an average of 10 dB or more at 2000 

Hz, 3000 Hz, and 4000 Hz in either ear [29 CFR 1910.95]. If a STS occurs, the company 

must determine if the hearing loss also meets the requirements to be recorded on the OSHA

Form 300 Log of Work-Related Injuries and Illnesses [29 CFR 1904.1]. In contrast to OSHA, 

NIOSH defines a significant threshold shift as an increase in the hearing threshold level of 

15 dB or more, relative to the baseline audiogram, at any test frequency in either ear 

measured twice in succession [NIOSH 1998].
Page 30 Health Hazard Evaluation Report 2015-0028-3330

Vibration

Prolonged exposure to hand-transmitted vibration is associated with a series of disorders 

in the vascular, sensorineural and musculoskeletal structures of human fingers-hand-arm 

system, which has been collectively called HAVS [Gemne and Taylor 1983]. Vibration 

exposure has been associated with the development of musculoskeletal disorders among 

chain saw operators [Bovenzi 2008; Sutinen et al. 2006].

Tri-axial vibration data were collected via a portable six-channel B&K PULSE system (Brüel 

& Kjær, Input/Output Module Type 3032A). The vibration data collected from this system 

were expressed as the root-mean-square (rms) values of the accelerations in the one-third 

octave frequency bands, with center frequencies from 6.3 to 1,250 Hz. The sampling rate of 

the B&K system is 2.56 times the highest frequency sampled, or in this case, 3,200 Hz. Both 

time-history data and frequency spectrum were recorded. The vector sum, or ‘total’ values of 

the unweighted rms accelerations were computed using the following formula:

(1)

where ah is the unweighted root-sum-of-squares total value, and ahx, ahy, and ahz, are the 

unweighted rms acceleration values for the x-, y-, and z-axis, respectively. 

To determine the ISO frequency-weighted acceleration values for each axis, an Excel spreadsheet 

was used to apply the frequency-weighting factors defined in ISO 5349-1 [ISO 2001a]: 

 

(2)

where ahw is the single-axis frequency-weighted rms acceleration, wj is the weighting 

factor for the jth one-third octave band as provided in Table 2 of the standard, and ah,j is 

the acceleration measured in the jth one-third octave band. In this process, the 24 one-third 

octave frequency band rms accelerations are multiplied by their respective weighting factors, 

and the resultant weighted rms accelerations are determined for each axis. 

Next, as is done with the unweighted acceleration, the total ISO frequency-weighted values 

are computed using

 (3)

where ahv is the ISO frequency-weighted root-sum-of-squares total value, and ahwx, ahwy, and ahwz

are the ISO frequency-weighted rms acceleration values for the x-, y-, and z-axis, respectively.

Using the above-described acceleration measurements, the ISO frequency-weighted saw 

handle vibration measurements (ahv) can be used to estimate hand-transmitted vibration 
Health Hazard Evaluation Report 2015-0028-3330 Page 31

exposures associated with the sawing tasks and saws evaluated in these evaluations. 

Estimated frequency- and time-weighted daily vibration exposure values, A(8), can be 

calculated using the methods outlined in ANSI S2.70-2006 [ANSI 2006]. The standard 

equation for estimating A(8) values is

 

(4)

where A(8) is the daily vibration exposure in m/s2, ahv is the total ISO frequency-weighted 

vibration magnitude (see Equation 3 above), T is the total daily duration of the exposure (in 

hours), and T0

 is the reference duration of eight hours. Once the A(8) values are determined, 

those values can be compared with the DEAV of A(8) = 2.5 m/s2

 and the DELV of 

A(8) = 5.0 m/s2

 established in the ANSI standard [ANSI 2006].
Page 32 Health Hazard Evaluation Report 2015-0028-3330

Appendix B: Interim Report on Safety Climate, Job 

Stress, Psychosocial Factors at Work, and Sleep

May 2, 2016

HHE 2015-0028

[Requestor]

Dear [Requestor]:

This interim report is in response to the National Institute for Occupational Safety and 

Health (NIOSH) health hazard evaluation (HHE) you requested in December 2014 for 

wildland firefighter employees of in . 

The request concerned potential exposures to hand-arm vibration, wood chipper dust, noise; 

safety climate; and job stress among employees. This interim report focuses on safety climate 

and job stress. 

 hires more than 100 state employees and college interns from the Utah Valley 

University’s Fire and Rescue Academy. Their mission is to suppress wildland fires, reduce 

hazards to communities at risk of fire, and improve forest health. All crews complete 

natural resource and fire management projects when not engaged in fire suppression. While 

completing projects, crews usually set up remote field camps for up to 8 days at a time and 

are subject to primitive living conditions. The crews take their firefighting equipment to these 

camps and are on call for fire assignments as they arise [ 2015]. 

Methods

We visited headquarters at the beginning of the fire season in May 2015 and again 

at the end of the season in October 2015 to conduct confidential interviews with employees. 

At the beginning of the season, most employees were engaged in training activities, 

administrative tasks, and preparing for the season. When we visited at the end of the season, 

the employees were engaged in season closeout procedures, making sure equipment was 

accounted for, and other administrative tasks.

During our visits, NIOSH investigators held confidential interviews with employees at the 

 headquarters, with the exception of one crew ( Hotshots). We interviewed the 

 Hotshots crew in vehicles while they were completing field work during our visit at the 

beginning of the fire season in May 2015. The interviews took approximately 10 minutes to 

complete, and included scaled and open-ended questions. 

Safety Climate

The interview included a six-item measure of safety climate [Hahn and Murphy 2008], which 

included questions about the following: management commitment to safety, safety feedback, 
Health Hazard Evaluation Report 2015-0028-3330 Page 33

worker involvement in safety, and coworker behavioral norms. The items were read to 

employees, who were presented with a four-point scale and asked to indicate their level of 

agreement (1 = strongly disagree, 2 = disagree, 3 = agree, 4 = strongly agree). One method 

for scoring these items is to total the scores (possible range 6–24) [NIOSH 2010]. The total is 

interpreted as:

● Between 6 and 15 indicates a poor safety climate at work

● Between 16 and 20 indicates a fair safety climate at work

● Between 21 and 24 indicates a good safety climate at work

We also analyzed responses by calculating the percentage of employees who indicated 

agreement with the statements presented to them.

Psychosocial Factors at Work

The interview also included questions about the following work factors: job demands, 

decision latitude, perceptions of coworkers, role expectations, job security, training, and 

work-life conflict. We also asked about job satisfaction and burnout. These items were 

selected from validated measures of job stressors deemed appropriate for HHEs [Wiegand et 

al. 2012]. These items were read to employees, who were presented with a four-point scale 

and asked to indicate their level of agreement (1 = strongly disagree, 2 = disagree, 3 = agree, 

4 = strongly agree).

Job Stress

We asked employees to rate their level of job stress with the following survey item: “During 

the past week, including today, how would you rate your current job stress level on a scale 

from 0 (as low as it can be) to 10 (as high as it can be)?” Responses of 0–3 indicated low job 

stress, 4–6 indicated moderate job stress, and scores of 7 or greater indicated high job stress 

[Clark et al. 2011]. This question was followed by an open-ended question asking employees 

to describe the major sources of stress on their job.

Sleep and Fatigue

We asked employees about their average sleep duration, quality of sleep, and frequency of 

unintentional sleep (e.g., dozing off while driving a vehicle).

Results and Discussion

At the beginning of the season, we interviewed 56 firefighters (96% male) with an average 

age of 26 years (range: 19–50 years). This included 21 (38%) firefighters from the 

Hotshots, 19 (34%) from Crew, and 16 (29%) from Crew. has 

other crews that were not present for interviews. Forty-three (77%) were seasonal firefighters. 

Fourteen (25%) were rookies, 26 (46%) had 2–4 years of experience, and 16 (29%) had > 5 

years of experience working for .

At the end of the season, we interviewed 48 firefighters (96% male) with an average age of 

27 years (range: 19–36 years). This included 18 (38%) firefighters from the Hotshots, 

11 (23%) from Crew, and 19 (40%) from Crew. Again, other 
Page 34 Health Hazard Evaluation Report 2015-0028-3330

crews were not present at the time of our visit. Thirty-five (73%) were seasonal firefighters. 

Twelve (25%) were rookies, 18 (38%) had 2–4 years of experience, and 18 (38%) had > 5 

years of experience working for .

We interviewed 36 employees both at the beginning and end of the season. Others were 

interviewed either at the beginning or the end of the season. When restricting analyses to 

the 36 employees who were interviewed twice, we found that the results were similar to 

those found when analyzing the total number of employee responses at the beginning and 

end of the season. Therefore, we are presenting the results for all participants, whether they 

participated one or both times. 

Safety Climate

In terms of overall safety climate, at the beginning of the season, 12 (21%) of employees 

reported a fair safety culture at work, while 44 (79%) reported a “good” safety culture at 

work. At the end of the season, 10 (21%) of employees reported a fair safety culture at 

work, while 38 (79%) reported a “good” safety culture at work. The number of employees 

responding either “agree” or “strongly agree” with individual safety climate item are 

included in Table 1.

Table 1. Employees indicating “agree” or “strongly agree” with individual safety climate items at the 

beginning and end of the fire season

Items Beginning of Season 

Agreement 

Frequency (%)

N = 56

End of Season 

Agreement

Frequency (%)

N = 48

The health and safety of workers is a high 

priority with management where I work.

56 (100) 47 (98)

Workers and management work together to 

ensure the safest possible conditions.

55 (98) 47 (98)

New employees learn quickly that they are 

expected to follow good health and safety 

practices.

56 (100) 48 (100)

Employees are told when they do not follow 

good health and safety practices.

55 (98) 44 (92)

I feel free to report safety problems where 

I work.

55 (98) 48 (100)

There are no major shortcuts taken when 

worker health and safety are at stake.

55 (98) 43 (90)

Although the safety climate scores were similarly positive at the beginning and end of the 

season, two items had slightly less support at the end of the season: “employees are told 

when they do not follow good health and safety practices” and “there are no major shortcuts 

taken when worker health and safety are at stake.” A possible explanation for these slightly 

lower levels of agreement is that at the beginning of the season, the employees had just
Health Hazard Evaluation Report 2015-0028-3330 Page 35

completed training where feedback regarding unsafe behaviors (including taking safety 

shortcuts) may have occurred more often. The experience of live firefighting presents a more 

chaotic environment where opportunities for employee observation and feedback may not 

be as common as when in training. Crews may have different supervisors when training 

than when in the field, so differences in supervisory styles may also have an impact on the 

employees’ perceptions of safety climate at different times of the season. 

Psychosocial Factors at Work

The number of employees responding either “agree” or “strongly agree” with the 

psychosocial items are included in Table 2.

Table 2. Employees indicating “agree” or “strongly agree” with psychosocial items at the beginning 

and end of the fire season

Items Beginning of Season 

Agreement 

Frequency (%)

N = 56

End of Season 

Agreement

Frequency (%)

N = 48

My job requires working very fast. 49 (88) 47 (98)

I have enough time to get the job done. 51 (91) 37 (77)

I am free from conflicting demands that 

others make while I work.

48 (86) 33 (69)

My job requires long periods of intense 

concentration on the task.

56 (100) 47 (98)

I am often required to work for long periods 

with my body in physically awkward positions.

47 (84) 46 (96)

I have a lot of say about what happens on 

my job.

41(73) 26 (54)

My job allows me to make a lot of decisions 

on my own.

39 (70) 34 (71)

People I work with are helpful in getting the 

job done.

56 (100) 47 (98)

It is clear to me what is considered acceptable performance by my supervisor.56 (100) 47 (98)

The demands of my job interfere with my 

home and family life.

30 (54) 40 (83)

The job training I received adequately 

prepared me to do the job correctly and safely.

56 (100) 46 (96)

My job security is good. 50 (89) 40 (83)

I feel burned out at work. 18 (32) 32 (67)

Overall, I am satisfied with my job. 56 (100) 42 (88)

If I were injured or feeling pain (as a result 

of my job or otherwise), I would seek 

medical attention.

N/A 40 (83)
Page 36 Health Hazard Evaluation Report 2015-0028-3330

Employees’ responses to the psychosocial items describe their work as physically and 

mentally demanding, with limited control or “say” about what happens on their jobs. Job 

stress is thought to increase when employees are faced with high job demands and low 

decision latitude or job control [Karasek and Theorell 1990].

At the end of the season, nearly one-third of employees reported that they are given 

conflicting demands from others at work, which may indicate that supervisors and/or 

employees are not consistently in agreement with job tasks, procedures, or priorities. This 

warrants further exploration since nearly all employees reported that they know what their 

supervisor expects of them, both at the beginning and end of the season. 

At the end of the fire season, most employees reported that their work interferes with their 

home and family life. This was to be expected given the employees’ lengthy deployments 

when suppressing fires in remote locations. Work-life conflict may be greater in situations 

where communication is limited while employees are deployed. Scheduling and poor internet 

or cell phone connectivity while in remote locations may disrupt communication with 

individuals and their families, or impede other aspects of life such as paying bills, managing 

finances, or being informed about current events. 

Two-thirds of the employees interviewed at the end of the season reported that they feel 

burned out at work, compared to one-third at the beginning of the season. This difference can 

be expected given the timing of the interviews, which is discussed further below. At the end 

of the season, the firefighters have experienced cumulative strain in their jobs, having been 

active for five months. Burnout showed a significant negative correlation with job satisfaction 

(r = -0.41, p < 0.01), meaning that as burnout increased, job satisfaction decreased. 

Some employees reported that they do not have good job security, and this was reported more at 

the end of the season. Job insecurity is associated with high psychological stress, poor self-rated 

health [Ferrie et al. 2002], and negative job and organizational attitudes [Sverke et al. 2002].

Most (83%) employees reported that they would seek medical attention if they were injured 

or feeling pain as a result of their job. Some of those employees who indicated they would 

not seek medical attention in these circumstances reported that they would let the injury/pain 

heal naturally, while others expressed concerns that they would lose job security if they were 

to seek medical care and miss time at work. Maintaining top physical shape and strength 

are integral to firefighting work, so it is important that employees seek medical attention for 

any conditions (e.g., musculoskeletal) which may become chronic or worsen over time, thus 

putting them at risk for being ineligible for future firefighting work.

Job Stress

Employees were asked to rate their level of job stress on a scale from 0 (as low as it can be) 

to 10 (as high as it can be). The average job stress score was 3.9 (N = 56) at the beginning of 

the season, indicating moderate job stress overall. On the basis of individual stress scores, 

26 (46%) employees indicated low job stress, 21 (38%) indicated moderate job stress, 

and 9 (16%) indicated high job stress. 
Health Hazard Evaluation Report 2015-0028-3330 Page 37

Employees were asked an open-ended question to describe the major sources of stress in their 

jobs. Employees could report multiple stressors, and Table 3 shows job stressors that were 

reported by 5 or more individuals.

Table 3. Frequency of reported job stressors at the beginning 

of the fire season (N = 56)

Job stressor Frequency (%)

Job demands 19 (33)

Meeting management expectations 19 (33)

Beginning of season (learning curve, 

getting into a routine)

18 (32)

Responsibility for others 14 (25)

Safety concerns 13 (23)

Work-life conflict 7 (12)

Fatigue 6 (11)

The most frequently reported stressors were associated with the physically and mentally 

demanding nature of the job and a desire to perform well to meet management expectations. 

One-third of employees specifically mentioned that the beginning of the season is a stressful 

time because they have a steep learning curve with policies and procedures, and they have 

to ready themselves for the season by developing a disciplined routine of exercise, nutrition, 

and hard work.

The average job stress score was 5.4 (N = 48) at the end of the season, again indicating 

moderate, yet elevated, job stress overall. On the basis of individual stress scores, 8 (17%) 

employees indicated low job stress, 24 (50%) indicated moderate job stress, and 16 (33%) 

indicated high job stress. 

Table 4 shows the job stressors reported by 5 or more individuals when asked an 

open-ended question.

Table 4. Frequency of reported job stressors at the end of the 

fire season (N = 48)

Job stressor Frequency (%)

Job demands 13 (27)

Work-life conflict 13 (27)

Responsibility for others 8 (16) 

Time pressure 7 (14)

Meeting management expectations 5 (10)

Safety concerns 5 (10)

Fatigue 5 (10)
Page 38 Health Hazard Evaluation Report 2015-0028-3330

At the end of the season, the most frequently reported stressors were the physically and 

mentally demanding nature of the job, and work-life conflict from being away from home for 

long periods over the season.

Firefighting (which may include structural and wildland firefighting) was ranked as the 

most stressful job in the United States based on an annual study which uses criteria such 

as deadlines, travel, growth potential, compensation, competitiveness, physical demands, 

hazards, environmental conditions, and risk to one’s life or to others’ [CareerCast 2015]. 

Wildland firefighting presents complex and multifaceted stressors including unpredictability 

of fires, time pressure, working in remote locations, heightened vigilance, fear of imminent 

death of self and others, responsibility for others, and exposure to smoke, equipment fumes, 

noise, hand-arm vibration, and heat, among others.

Sleep and Fatigue

At the beginning of the season, employees reported getting an average of 7 hours (range: 

3–10 hours) of sleep in a 24-hour period. They reported unintentionally falling asleep at least 

once a day an average of 2 days (range: 0–26 days) per month. Two employees indicated that 

they had fallen asleep while driving a vehicle in the past month. Employees reported that 

they felt they did not get adequate rest an average of 6 days (range: 0–30 days) in the last 

month. Most employees (91%) indicated that their quality of sleep over the past month was 

fairly or very good.

At the end of the season, employees reported getting an average of 7 hours (range: 4–8 hours) 

of sleep in a 24-hour period. They reported unintentionally falling asleep at least once a day an 

average of 6 days (range: 0–30 days) per month. Five employees indicated that they had fallen 

asleep while driving a vehicle in the past month. Employees reported that they felt they did not 

get adequate rest an average of 10 days (range: 0–30 days) in the last month. Most employees 

(81%) indicated that their quality of sleep over the past month was fairly or very good.

Job stress is associated with fatigue. For example, Kashani et al. [2012] found that 

individuals experiencing high stress had more daytime sleepiness, greater fatigue, poorer 

sleep quality, and shorter sleep duration than those who experienced low stress. Fatigue can 

also impair job performance [Dawson and Reid 1997]. Firefighting is an inherently risky 

profession. It is important that firefighters are vigilant, clear headed, and able to react quickly 

if in a potentially dangerous situation. Coping with stress and remaining well rested are 

essential to maintaining well-being and high performance on the job.

Lourel et al. [2008] described research on three important stress-related phases of 

firefighting. The pre-operational phase occurs during training and when firefighters are 

anticipating response to a fire. During this time, firefighters tend to experience anxiety and 

are taxed with increased concentration on tasks. The operational phase is the time when 

firefighters are taking action at the scene of a fire. During this phase, firefighters experience 

increased physical and psychological distress. Finally, the post-operational phase occurs 

when a fire mission is complete and firefighters return to their normal surroundings. During 

this “decompression” phase, the stress of firefighting begins to manifest in physical soreness, 

fatigue, and self-reflection or self-criticism. This HHE focused on the pre- and post-
Health Hazard Evaluation Report 2015-0028-3330 Page 39

operational phases of firefighting, so increased job stress and fatigue at the end of the season 

are to be expected. 

Conclusion

Overall, wildland firefighter employees reported a strong safety climate, favorable 

perceptions of various psychosocial factors at work, and moderate job stress. Employees 

reported decreased sleep quality at the end of the season. We present recommendations 

below to address areas that may need further exploration or improvement on the basis of our 

interview results.

Recommendations

1. Talk to employees about job demands and how they affect job stress, burnout, and job 

satisfaction. Their input may provide insight on how to better cope with high demands 

and improve perceptions of work.

2. Identify and address potential source(s) of conflicting work demands that some 

employees report. 

3. Talk to employees about why some believe they have poor job security. If the reasons 

are unfounded, address them with all employees. management should express 

appreciation and value for employees throughout the season and when applicable, 

offer reassurance regarding job security in end-of-season performance reviews.

4. Designate someone at headquarters to serve as a liaison between deployed 

employees and their families in case communication is limited and employees are 

having difficulty reaching family members or conducting other affairs. 

5. Train employees in stress reduction exercises such as controlled breathing, 

mindfulness, and meditation, and encourage them to practice these techniques during 

deployment downtime. 

6. Encourage employees to report work-related health symptoms, strains, and pain to 

their supervisor and promptly seek medical attention from a healthcare provider if 

these symptoms are causing distress. 

7. Ensure employees receive adequate training on the importance of good sleep habits, 

the hazards associated with fatigue at work, and strategies for managing them. For 

more information on sleep, see http://www.cdc.gov/sleep.
Page 40 Health Hazard Evaluation Report 2015-0028-3330

Thank you for your cooperation with this ongoing evaluation. For the purpose of informing 

affected employees, we recommend that copies of this letter be posted by the employer in a 

place accessible to the employees. We are planning another site visit in the spring of 2016 

to assess exposure to wood chipper dust, carbon monoxide, noise, and hand/arm vibration, 

and to complete confidential medical interviews. We will be contacting you to discuss the 

details of this site visit. After we have performed this follow up evaluation, we will prepare a 

formal report combining the results and recommendations for all aspects of this health hazard 

evaluation. If you have any questions, please do not hesitate to contact me at (513) 841-4240 

or dwiegand@cdc.gov.

 Sincerely,

 Douglas Wiegand, PhD

Behavioral Scientist

Hazard Evaluations and Technical

 Assistance Branch

Division of Surveillance, Hazard

 Evaluations and Field Studies

cc: [Employee Representative]

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Page 46 Health Hazard Evaluation Report 2015-0028-3330

Keywords: North American Industry Classification System (NAICS) 115310 (Support 

Activities for Forestry), Utah, Wildland Fire Fighters, Fuel Reduction, Carbon Monoxide, 

Wood Dust, Noise, Hand-Arm Vibration, Chainsaw
Health Hazard Evaluation Report 2015-0028-3330 Page 47

The Health Hazard Evaluation Program investigates possible health hazards in the workplace

under the authority of the Occupational Safety and Health Act of 1970 (29 U.S.C. § 669(a)

(6)). The Health Hazard Evaluation Program also provides, upon request, technical assistance

to federal, state, and local agencies to investigate occupational health hazards and to prevent

occupational disease or injury. Regulations guiding the Program can be found in Title 42, Code

of Federal Regulations, Part 85; Requests for Health Hazard Evaluations (42 CFR Part 85).

Disclaimer

The recommendations in this report are made on the basis of the findings at the workplace 

evaluated and may not be applicable to other workplaces.

Mention of any company or product in this report does not constitute endorsement by 

NIOSH.

Citations to Web sites external to NIOSH do not constitute NIOSH endorsement of the 

sponsoring organizations or their programs or products. NIOSH is not responsible for the 

content of these Web sites. All Web addresses referenced in this document were accessible as 

of the publication date.

Acknowledgments

Analytical Support: Maxaam Analytics

Desktop Publisher: Shawna Watts 

Industrial Hygiene Field Assistance: Eric Glassford

Logistics: Donnie Booher, Kevin Moore

Medical Field Assistance: Xiangning Fan, Isabel Liu

Statistical Support: Charles Mueller

Availability of Report

Copies of this report have been sent to the employer and employees at the facility. The state and 

local health department and the Occupational Safety and Health Administration Regional 

Office have also received a copy. This report is not copyrighted and may be freely reproduced. 

Recommended citation for this report:

NIOSH [2019]. Evaluation of wildland fire fighter exposures during fuel reduction 

projects. By Ramsey JG, Eisenberg J, Wiegand D, Brueck SE, McDowell TW. 

Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease 

Control and Prevention, National Institute for Occupational Safety and Health, Health 

Hazard Evaluation Report 2015-0028-3330, https://www.cdc.gov/niosh/hhe/reports/

pdfs/2015-0028-3330.pdf.
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