NIOSH HEALTH HAZARD EVALUATION REPORT:

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

TM

HETA #2000-0061-2885

United States Air Force

Seymour Johnson Air Force Base

Goldsboro, North Carolina

December 2002

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports
ii

PREFACE

The Hazard Evaluations and Technical Assistance Branch (HETAB) of the National Institute for Occupational Safety and

Health (NIOSH) conducts field investigations of possible health hazards in the workplace. These investigations are conducted

under the authority of Section 20(a)(6) of the Occupational Safety and Health (OSHA) Act of 1970, 29 U.S.C. 669(a)(6) which

authorizes the Secretary of Health and Human Services, following a written request from any employer or authorized

representative of employees, to determine whether any substance normally found in the place of employment has potentially

toxic effects in such concentrations as used or found.

HETAB also provides, upon request, technical and consultative assistance to federal, state, and local agencies; labor; industry;

and other groups or individuals to control occupational health hazards and to prevent related trauma and disease. Mention of

company names or products does not constitute endorsement by NIOSH.

ACKNOWLEDGMENTS AND AVAILABILITY OF REPORT

This report was prepared by Ann Krake, Joel McCullough, and Brad King of HETAB, Division of Surveillance, Hazard

Evaluations and Field Studies (DSHEFS). Field assistance was provided by Sergeant Douglas Fritts and Sergeant Joyce Foster.

Pre- and post-activity body weight data were provided by Dr. Amit Bhattacharya, Edward Auyang, Jessica Gordan,

Dr. Laurel Kincl, Ming Lun Lu, and Terry Mitchell, University of Cincinnati, Department of Environmental Health, College

of Medicine, Cincinnati, Ohio. Dr. Paul Jensen, Stephen Martin, Earnest Moyer, and Stephen Berardinelli, NIOSH, Division

of Respiratory Disease Studies (DRDS), Morgantown, West Virginia, provided field assistance and field notes essential to this

report. Dr. Thomas E. Bernard, University of South Florida, College of Public Health, Tampa, Florida, provided essential

guidance on the report’s content for which the authors are very grateful. Desktop publishing was performed by David Butler.

Review and preparation for printing were performed by Penny Arthur.

The authors would like to thank the USAF for the loan of the core body temperature monitors and Ms. Lindy Brounley,

formerly of HQ, Incorporated, Palmetto, Florida, for her support and guidance in the use of the CorTempTM monitoring system,

as well as HQ, Incorporated’s generous equipment loans. The authors are especially thankful for the help provided by many

of the JP-8 jet fuel study investigators including principal Major Leslie B. Smith (Ret.), and co-investigators

Major Donald Christianson, and Lieutenant Colonel Roger Gibson, USAF. Technical support and guidance were provided

by Mr. Allen Meyers, Sergeant David Villareal, Major Brian Blazicko, Sergeant Sally Perez, Sergeant Michael Lasenby, and

Major Shawn Moore, USAF.

Copies of this report have been sent to employee and management representatives at Seymour Johnson AFB. This report is

not copyrighted and may be freely reproduced. Single copies of this report will be available for three years from the date of

this report. To expedite your request, send a self-addressed mailing label with your written request to:

NIOSH Publications Office

4676 Columbia Parkway

Cincinnati, Ohio 45226

800-356-4674

After this time, copies may be purchased from the National Technical Information Service (NTIS) at 5825 Port Royal Road,

Springfield, Virginia 22161. Information regarding the NTIS stock number may be obtained from the NIOSH Publications

Office at the Cincinnati address.

For the purpose of informing affected employees, copies of this report shall

be posted by the employer in a prominent place accessible to the employees

for a period of 30 calendar days.
iii

Highlights of the NIOSH Health Hazard Evaluation

Evaluation of Heat Stress in Fuel Systems Maintenance

Personnel at Seymour Johnson Air Force Base

During May 15–19, 2000, NIOSH representatives conducted a health hazard evaluation at Seymour Johnson Air

Force Base (SJAFB), Goldsboro, North Carolina. We looked into management concerns about personnel

exposures to high temperatures while conducting fuel systems maintenance (FSM) activities.

What NIOSH Did

# We measured the temperatures outside and inside the

hangar. We also measured how much work (work

load) the employees did.

# About half of the participants were weighed before

and after their work and were tested for dehydration

(not having enough water in their bodies).

# We measured the heart rates and internal body

temperatures of the participants while they did their

work.

# We talked to the participants about their jobs and

asked them to tell us their health concerns.

What NIOSH Found

# The FSM participants were not exposed to excess

heat stress and none got sick from the heat.

# Two of twenty-three FSM participants had heart rates

that were high enough during parts of their shift that

they were more likely to get sick from the heat than

those who didn’t have high heart rates.

# Eight of ten FSM participants became at least mildly

dehydrated during their shift, and lost over 1.5% of

their body weight. Personnel who lose weight during

their shift are more likely to get sick from the heat.

# None of those affected knew they had heat strain

and/or dehydration and did not know they were in

danger of getting sick from the heat.

# SJAFB has heat stress instruction, but it does not

cover all personnel in all work situations and it does

not teach employees how to monitor themselves for

heat strain. Highlights of the NIOSH HHE

What SJAFB Managers Can Do

# Add a heat strain (physiological) monitoring program

to the base instruction for heat stress that will:

< teach personnel the reasons for and benefits of

listening to their bodies when they are heat stressed;

< train personnel in personal monitoring techniques;

< encourage employees to use the buddy system to

monitor themselves and others’ heat stress and strain

signs.

# Conduct heat strain monitoring when air- and vaporimpermeable encapsulating suits are required and/or

when dry bulb temperatures exceed 68°F.

# Take wet bulb globe temperature measurements as

close to the work area as possible, and take readings

hourly during the hottest part of the shift and hottest

months of the year.

What SJAFB Personnel Can Do

# Learn to monitor yourself and your co-workers for

heat stress and strain, and take breaks when needed

before you get sick.

# Some of the first signs of heat strain, lack of good

judgement and inability to think critically, usually are

not noticed by the person who is getting sick from the

heat. Therefore, make sure you are well-hydrated,

have eaten enough, and have slept well before you

work in the heat.

# Avoid getting sick from drinking too much water.

Eat three meals a day, and eat snacks with the water

you drink between meals.

# Report any heat-related illnesses and other concerns

to your crew leader or commanding officer.

What To Do For More Information:

We encourage you to read the full report. If you

would like a copy, either ask your health and safety

representative to make you a copy 

or call 1-513-841-4252 and ask for

 HETA Report #2000-0061-2885
iv

Health Hazard Evaluation Report 2000-0061-2885

United States Air Force, Seymour Johnson Air Force Base

Goldsboro, North Carolina

December 2002

Ann M. Krake, MS, REHS

Joel E. McCullough, MD, MPH

Bradley S. King, MPH

SUMMARY

The National Institute for Occupational Safety and Health (NIOSH) received a health hazard evaluation (HHE)

request from the management of the United States Air Force Institute for Environmental, Safety, and Occupational

Risk Analysis (AFIERA), Brooks Air Force Base (AFB), San Antonio, Texas. The request indicated that Air Force

recruits employed as aircraft fuel systems inspection and repair workers at Seymour Johnson AFB, Goldsboro,

North Carolina, were exposed to heat stress, jet fuel, and jet fuel vapors in confined spaces (aircraft fuel tanks). The

employees reported experiencing dizziness, lethargy, skin irritation, and a ‘jet-fuel taste’ during and long after

exposure to jet fuel. The requesters asked NIOSH to evaluate the heat stress aspects of the employee complaints

and make recommendations to prevent heat illness among the employees. The evaluation was part of an on-going

collaborative study of Air Force employees’ acute exposure to jet fuel (JP-8), and the other concerns were

addressed by this larger study.

Data were collected May 15–19, 2000. Individual and task-specific metabolic rates were estimated, and wet bulb

globe temperatures (WBGTs) were measured. Heat strain monitoring included core body temperature (CBT) and

heart rate measurements on 23 participants and pre- and post-shift body weight measurements on 10 participants.

The sampling results were compared to the NIOSH recommended action limits and recommended exposure limits

(RALs/RELs) and the American Conference of Governmental Industrial Hygienists (ACGIH®) Threshold Limit

Values (TLVs®). NIOSH and ACGIH assess heat stress using sliding scale limits based on environmental and

metabolic heat loads. In addition, ACGIH provides physiological heat strain limits useful for those wearing

impermeable personal protective equipment (PPE) and in situations of excess heat stress. For individuals with

normal cardiac performance, ACGIH recommends that sustained (over several minutes) heart rate should remain

below 180 beats per minute (bpm) minus age (in years), maximum CBT should remain below 100.4°F for

unselected, unacclimatized personnel (101.3°F for medically selected, acclimatized personnel), recovery heart rate

at one minute after a peak work effort should be below 110 bpm, and there should be no symptoms of sudden and

severe fatigue, nausea, dizziness, or lightheadedness.

The results of the evaluation indicated that all of the participants were acclimatized to their work environment and

that none were exposed to heat stress conditions in excess of the screening criteria. However, 2 of 23 participants

experienced heat strain signs, specifically HR in excess of the ACGIH criteria. In addition, 2 of 10 participants had

greater than 1.5% body weight loss over their shifts indicating they were at greater risk of developing a heat-related

illness. Six additional participants developed mild dehydration (body weight loss of 1.5% or less). Overall, body

weight changes ranged from -2.7% to +1.2%, with a median percent body weight change of -1.0%.
v

The evaluation results and the potential for heat strain to increase as temperatures rise during the spring and summer

indicate that FSM personnel should be included in a heat stress management program. In addition, participants were

not aware of having developed heat strain, indicating a need for a physiological self-monitoring program to be

added to the heat stress program.

During the NIOSH evaluation, health hazards from environmental conditions and overwork did not exist

for fuel cell maintenance and other workers. However, hazardous environmental conditions can exist

during spring and summer, and a few participants developed heat strain as indicated by the physiological

monitoring results (heart rate levels in excess of occupational criteria). Also, of the 10 participants who

were weighed pre-and post-shift, 6 developed mild dehydration and 2 more were dehydrated. Seymour

Johnson AFB has a heat stress instruction; however, the instruction does not include a system for

reporting heat-related illnesses or for monitoring personnel wearing water- or vapor- impermeable

clothing ensembles. Recommendations are made to implement physiological (heat strain) monitoring and

to take WBGT measurements in the immediate work areas at least hourly during the hottest parts of the

shift and the hottest months of the year.

Keywords: SIC 9711 (National Security). Heat stress, heat strain, heat-related illness, core body temperature,

metabolic rates, WBGT, wet-bulb globe temperatures, Air Force aircraft fuel cells, aircraft fuel cell maintenance,

fuel systems maintenance, FSM.
TABLE OF CONTENTS

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Acknowledgments and Availability of Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Highlights of the NIOSH HHE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv

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

Background ......................................................................... 1

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

Evaluation Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Heat Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Heat Strain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Health Effects of Exposure to Hot Environments .......................................... 6

Acclimatization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Dehydration and Fluid Replacement ................................................... 7

Hyponatremia (Water Toxicity) ....................................................... 8

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Workload and Task Assessments (Heat Stress) ............................................ 8

Physiological Monitoring (Heat Strain) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Heat Stress Management at Seymour Johnson AFB ........................................ 9

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Health Hazard Evaluation Report No. 2000-0061-2885 Page 1

INTRODUCTION

The National Institute for Occupational Safety and

Health (NIOSH) received a health hazard evaluation

(HHE) request from the management of the United

States Air Force (USAF) Institute for Environmental,

Safety, and Occupational Risk Analysis (AFIERA),

Brooks Air Force Base (AFB), San Antonio, Texas.

The request indicated that Air Force recruits

employed as aircraft fuel systems maintenance

inspection and repair (FSM) workers, at Seymour

Johnson AFB, Goldsboro, North Carolina, were

exposed to heat, jet fuel, and jet fuel vapors in

confined spaces (aircraft fuel tanks). The employees

reported experiencing dizziness, lethargy, skin

irritation, and a ‘jet-fuel taste’ in their mouths during

and long after exposure to jet fuel.

The Seymour Johnson AFB heat stress evaluation

was conducted as part of a collaborative study of Air

Force employees’ acute exposure to jet fuel (JP-8).

The JP-8 study was conducted over one year at

seven bases located throughout the southern and

southwestern U.S. and included 324 Air Force

employees. Nearly half of the participants were men

and women who routinely work with jet fuel and had

conducted tank-entry tasks at least one hour, twice

per week, on the same base for the past nine months.

The remaining participants were men and women

stationed on the same base but not routinely in

contact with jet fuel. Personnel could not participate

in the study if they had used alcohol 12 hours prior

to the start of the study; had injuries requiring

medical attention within the past 6 months; had a

history of stroke, diabetes, or seizures; were

pregnant; or were taking medications including

diet pills, anti-depressants, or hypertension drugs.

The jet fuel research team consisted of

approximately 30 researchers from six academic

institutions, two government agencies, the USAF,

and the United States Navy. Data from all seven heat

stress evaluations will be used to determine any

associations between heat stress and strain and fuel

uptake and metabolism, and will be analyzed as

possible confounders in various aspects of the risk

assessment.

During the week of May 15–19, 2000, two NIOSH

officers and other JP-8 study collaborators visited

the aircraft fuel tank maintenance shop at Seymour

Johnson AFB. The work environment was assessed

with wet bulb globe temperature (WBGT) monitors

and by calculating the estimated metabolic heat

load of each work task. The heat strain evaluation

included personal monitoring of core body

temperature (CBT), ear temperature, skin

temperature, heart rate, activity levels, and pre- and

post-activity body weights.

BACKGROUND

Seymour Johnson AFB is a Tactical Air Combat

Command installation located in Goldsboro, North

Carolina, and is home to the 4th Fighter Wing. The

base houses B-52 bombers, KC-10 and KC-135

tankers, and F-4 and F-16 fighters. The 4th Fighter

Wing is comprised of maintenance, operations,

medical, and mission support groups. Seymour

Johnson FSM employees are part of the maintenance

group under the ‘Aircraft Maintenance Squadron’

activity. Approximately 30 employees rotate among

two or three shifts depending upon the amount of

work to be completed. FSM activities mostly take

place inside metal non-air-conditioned hangars large

enough for one to three planes, but can also occur

outside on the flight line. One or two FSM crews

work on a plane at one time, and their duties include

removing any remaining jet fuel from the fuel cell,

opening the entrance to the cell (usually a small port

underneath the wing or on the fuselage), de-puddling

the cell (removing the last of the fuel from the floor

of the cell), and conducting maintenance activities.

Breaks and lunch are taken in an air-conditioned

room adjoining the hangar or outdoors.

Each crew consists of an entrant, attendant, runner,

and shop supervisor. The entrant is responsible for

going into the fuel cell, finishing the de-puddling,

locating the area to be repaired or maintained, and

removing large foam “sponges” to gain access to that

area. (The foam sponges fill each fuel cell in specific

order and are used for spark arrest in the event the

plane’s fuel tanks are damaged by gunfire.) The

attendant is an assistant and backup for the entrant
Page 2 Health Hazard Evaluation Report No. 2000-0061-2885

and usually stands just outside the porthole catching

the foam removed by the entrant. The runner takes

the foam from the attendant and arranges it in order

on the floor of the hangar on absorbent material. The

runner is also responsible for supplying parts, tools,

and other necessities to the attendant, who then

passes them on to the entrant. Crew members were

previously cross trained and were observed to

frequently rotate their activities during the study

period. The shop supervisor, usually the highest in

rank, oversees the operation and can act in any of

the other three job categories if necessary. The crew

members dress in thick 100% cotton coveralls and

may wear pants and/or a T-shirt underneath. Some

entrants and attendants also wear gloves and

impermeable aprons over their coveralls, but most

wore neither, and all of them entered the tank

wearing only cotton socks on their feet. The entrants

and some of the attendants wore supplied-air

respirators. The respirator and confined space

programs were evaluated by other members of the jet

fuel study team.

Others exposed to JP-8 work in the fuels and

fuels-transportation shops, commonly called

petroleum, oils, and lubricants shops, or POLs, and

as aircraft maintenance (avionics) specialists. POL

responsibilities include refueling aircraft and filling

and maintaining bulk fuel storage tanks, while

maintenance specialists work with the planes’

guidance and electrical systems. Work is mostly

outdoors, but much time is spent in air-conditioned

trucks driving from site to site. The uniform is the

same thick 100% cotton coveralls, and T-shirts and

pants are usually worn underneath.

Based upon averages over the past 5 years, the

Goldsboro area’s average high temperature is 72°F,

with an average low of 52°F. The average number of

days hotter than 90°F is 61, and the average number

of days colder than 32°F is 40. Average rainfall is

51 inches.1

METHODS

WBGT measurements were collected using two

RSS-214 WiBGeT® instruments (Imaging &

Sensing Technology, Horseheads, New York).

These monitors are capable of measuring

temperatures of 32°F–150°F and are accurate to

within ±0.5°F. The WBGT index accounts for air

velocity, temperature, humidity, and radiant heat

and is a useful index of the environmental

contribution to heat stress. It is a function of dry

bulb temperature (a standard measure of air

temperature taken with a thermometer), natural wet

bulb temperature (simulates the effects of

evaporative cooling), and black globe temperature

(estimates radiant [infrared] heat load). One WBGT

monitor was placed outdoors while the other was

placed in the hangar on a work table near the work

area. The monitors collected temperature data only

during the hours worked by the study participants

and therefore may not include the true high and low

temperatures of each day. Also, because no data are

available for conditions inside the fuel cell,

environmental temperatures to which the entrant was

exposed may be underestimated. Because the crew

members dress in thick 100% cotton coveralls and

may wear pants and/or T-shirt underneath, a clothing

adjustment factor of 2°F was used to adjust the

measured WBGTs during the data analysis.2

Metabolic rates for five different activities, including

entrant, attendant, runner, POL/avionics specialist,

and ‘other,’ were estimated. The ‘other’ category

includes scheduled and unscheduled breaks and all

other non-working activities, such as time spent

waiting for planes or parts to arrive, that are part of

the work shift. Metabolic rates were estimated using

the NIOSH table, “Estimated metabolic heat

production rates by task analysis” (Appendix A).

This method allows for specificity in rate estimation

because it breaks the job down into categories that

account for body position and movement, type of

work, and basal metabolism. 

Individual metabolic rates were estimated for the

participants whose weights were available. The

same NIOSH estimation method as for the activities

was used (Appendix A). The NIOSH values are

based upon a standard weight of 154 pounds (lbs), so
Health Hazard Evaluation Report No. 2000-0061-2885 Page 3

a weight correction factor must be applied when

workers weigh other than 154 lbs. The resulting

estimates are also weighted to reflect the time the

participants spent conducting each activity. Also,

participants worked an 8-hour shift, but spent about

2 hours before and 2 hours after their FSM activities

completing other components of the jet fuel study.

No heat exposure monitoring occurred during these

times. Therefore, the resulting estimates are not

“full-shift” time-weighted averages (TWAs) and may

underestimate participants’ heat stress and strain

levels. Individual results will vary depending on age,

sex, fitness level, current health status, and body

weight, and partly because of observer variability,

errors in estimating metabolic rates may vary by

±10%–15%.3

Heat strain was assessed using the CorTempTM

Wireless Core Body Temperature Monitoring

System (HQ, Inc., Palmetto, Florida). The CorTemp

Temperature Sensor, a 0.9 x 0.4 inch silicon-coated

electronic device, is swallowed and provides

continuous monitoring of CBT to within ±0.2°F.

The sensor is passed through the gastrointestinal tract

and exits the body at participants’ normal transit

time, an average of approximately 72 hours. The

sensor, intended for one-time use only, runs on a

non-rechargeable silver-oxide battery and utilizes a

temperature sensitive crystal which vibrates in direct

proportion to the temperature of the substance

surrounding it. This vibration creates an

electromagnetic flux (frequency = 262.144 kilohertz)

which continuously transmits through the

surrounding substance. A recorder, the CT2000,

receives this signal and translates it into digital

temperature information, which is then displayed

on the unit and stored to memory. The CT2000

Recorder monitors temperatures of 50°F–122°F. The

recorder operates on one standard 9-volt alkaline

battery, weighs about 7 ounces, and attaches to the

user’s belt. The participants’ CBTs were recorded at

1-minute intervals.

Heat strain was also assessed using a Mini-Mitter

Mini-Logger® Series 2000 (Mini-Mitter Company,

Inc., Bend, Oregon). Heart rate, gross motor activity,

skin temperature, and ear temperature, all of which

directly impact or are a function of the body’s

metabolic rate, were monitored at 1-minute

intervals.a

 The participants were asked to wear an

aural (ear) temperature probe, a skin temperature

probe, Polar® chest band heart rate monitor, and an

activity sensor on the dominant wrist. The MiniLogger’s ear and skin temperature readings are

accurate to within ±0.18°F and have a range of

86°F–108°F. The Polar chest band heart rate

monitor counts up to 250 beats per minute (bpm) and

is accurate to within ±1 heart beat. The activity

monitor, which works by counting the number of

movements per collection interval, is accurate to

within ±1 millisecond and counts up to 65,353

movements per interval. The recorder weighs about

4 ounces and is worn on the user's belt.

Pre- and post-shift body weights were measured on

10 of 23 participants as part of the performance and

balance measurements aspect of the jet fuel study and

were used to determine the participants’ degree of

dehydration. Participants were weighed without

socks and shoes using a self-calibrating Health o

meter®, Inc., electronic digital strain-gauge scale,

Model 842, accurate to within 0.25 lbs with a

capacity of 300 lbs.

EVALUATION CRITERIA

As a guide to the evaluation of the hazards posed by

workplace exposures, NIOSH field staff employ

environmental evaluation criteria for the assessment

of a number of chemical and physical agents. These

a The ear and skin temperature and activity

measurements are not included in this report. No

evaluation criteria exist for any of these

measurements, and ear and skin temperatures are

influenced by environmental conditions thereby

decreasing their accuracy in heat stress

assessments. Rather, these measurements will be

compared to the CBT, heart rate, and WBGT

measurements, which do have established criteria.

Air Force personnel and management

representatives will be provided with any future

analyses of these measurements.
Page 4 Health Hazard Evaluation Report No. 2000-0061-2885

criteria are intended to suggest levels of exposure to

which most workers may be exposed up to 10 hours

per day, 40 hours per week for a working lifetime

without experiencing adverse health effects. It is,

however, important to note that not all workers will

be protected from adverse health effects even though

their exposures are maintained below these levels. A

small percentage may experience adverse health

effects because of individual susceptibility, a preexisting medical condition, and/or a hypersensitivity

(allergy). In addition, some hazardous substances

may act in combination with other workplace

exposures, the general environment, or with

medications or personal habits of the worker to

produce health effects even if the occupational

exposures are controlled at the level set by the

criteria. These combined effects are often not

considered in the evaluation criteria. Also, some

substances are absorbed by direct contact with the

skin and mucous membranes, which potentially

increases the overall exposure. Finally, evaluation

criteria may change over the years as new

information on the toxic effects of an agent become

available.

The primary sources of environmental evaluation

criteria for the workplace are: (1) NIOSH

Recommended Exposure Limits (RELs),4

 (2) the

American Conference of Governmental Industrial

Hygienists’ (ACGIH®) Threshold Limit Values

(TLVs®),5

 and (3) the U.S. Department of Labor,

Occupational Safety and Health Administration

(OSHA) Permissible Exposure Limits (PELs).6

Employers are encouraged to follow the OSHA

limits, the NIOSH RELs, and the ACGIH TLVs,

whichever are the more protective criterion.

OSHA requires an employer to furnish employees a

place of employment that is free from recognized

hazards that are causing 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)]. Employers should understand that not all

hazardous agents, including heat stress, have specific

OSHA exposure limits such as PELs or short-term

exposure limits (STELs); however, even in the

absence of a PEL or STEL, an employer is still

required by OSHA to protect their employees from

these hazards.

A TWA exposure refers to the average airborne

concentration of a substance during a normal 8- to

10-hour workday. Some substances have

recommended STEL or ceiling values which are

intended to supplement the TWA where there are

recognized toxic effects from higher exposures over

the short-term.

Heat Stress

NIOSH defines heat stress exposure as the sum of the

heat generated in the body (metabolic heat) plus the

heat gained from the environment (environmental

heat) minus the heat lost from the body to the

environment, which is primarily through

evaporation. Many bodily responses to heat stress

are desirable and beneficial because they help

regulate internal temperature and, in situations of

appropriate repeated exposure, help the body adapt

(acclimate) to the work environment. However, at

some stage of heat stress, the body’s compensatory

measures cannot maintain internal body temperature

at the level required for normal functioning. As a

result, the risk of heat-induced illnesses, disorders,

and accidents substantially increases.3

 Increases in

unsafe behavior are also seen as the level of physical

work of the job increases.3

Many heat stress guidelines have been developed

to protect people against heat-related illnesses. The

objective of any heat stress index is to prevent a

person's CBT from rising excessively. The World

Health Organization concluded that “it is inadvisable

for CBT to exceed 38°C (100.4°F) or for oral

temperature to exceed 37.5°C (99.5°F) in prolonged

daily exposure to heavy work and/or heat.”7

According to NIOSH, a deep body temperature of

39°C (102.2°F) should be considered reason to

terminate exposure even when deep body

temperature is being monitored.3

 This does not

mean that a worker with a CBT exceeding those

levels will necessarily experience adverse health

effects; however, the number of unsafe acts increases

as does the risk of developing heat stress illnesses.3
Health Hazard Evaluation Report No. 2000-0061-2885 Page 5

NIOSH recommends that total heat exposure be

controlled so that unprotected healthy workers who

are medically and physically fit for their required

level of activity and are wearing, at most, longsleeved work shirts and trousers or equivalent, are

not exposed to metabolic and environmental heat

combinations exceeding the applicable NIOSH

criteria, as follows: Almost all healthy employees,

working in hot environments and exposed to

combinations of environmental and metabolic heat

less than the NIOSH Recommended Action Limits

(RALs) for non-acclimatized workers (Appendix B,

Figure 1) or the NIOSH (RELs) for acclimatized

workers (Appendix B, Figure 2), should be able to

tolerate total heat stress without substantially

increasing their risk of incurring acute adverse health

effects. Also, no employee should be exposed to

metabolic and environmental heat combinations

exceeding the applicable Ceiling Limits (C) of

Appendix B (Figures 1 and 2) without being

provided with and properly using appropriate and

adequate heat-protective clothing and equipment.3

ACGIH guidelines require the use of a decisionmaking process which provides step-by-step

situation-dependent instructions that factor in

clothing insulation values and physiological

evaluation of heat strain (see Evaluation Scheme for

Heat Stress, Appendix C). ACGIH WBGT

screening criteria (Appendix D) factor in the ability

of the body to cool itself (clothing insulation value,

humidity, wind), and, like the NIOSH criteria, can be

used to develop work/rest regimens for acclimatized

and unacclimatized employees. The ACGIH

WBGT-based heat exposure assessment was

developed for a traditional work uniform of longsleeved shirt and pants, and represents conditions

under which it is believed that nearly all adequately

hydrated, unmedicated, healthy workers, may be

repeatedly exposed without adverse health effects.

Clothing insulation values and the appropriate

WBGT adjustments, as well as descriptors of the

other decision-making process components can be

found in ACGIH’s Threshold Limit Values (TLVs®)

for Chemical Substances and Physical Agents and

Biological Exposure Indices.5

 The ACGIH TLV

for heat stress attempts to provide a framework for

the control of heat-related illnesses only. Although

accidents and injuries can increase with increasing

levels of heat stress, it’s important to note that the

TLVs are not directed toward controlling these.8

NIOSH and ACGIH criteria can only be used when

WBGT data for the immediate work area are

available and must not be used when wearing

encapsulating suits or garments that are impermeable

or highly resistant to water vapor or air movement.

Further assumptions regarding work demands

include an 8-hour work day, 5-day work week, two

15-minute breaks, and a 30-minute lunch break, with

rest area temperatures the same as, or less than, those

in work areas, and “at least some air movement.” It

must be stressed that NIOSH and ACGIH guidelines

do not establish a fine line between safe and

dangerous levels but require professional judgement

and a heat stress management program to ensure

protection in each situation.

OSHA does not have a specific heat stress standard,

however, acceptable exposure to heat stress is

enforced by the Secretary of Labor under the

General Duty Clause [section 5(a)(1)].9

 The OSHA

technical manual, Section III, Chapter 4,10 provides

investigation guidelines that approximate those

found in ACGIH’s 1992-1993 Threshold Limit

Values for Chemical Substances and Physical Agents

and Biological Exposure Indices.

Heat Strain

The body’s response to heat stress is called heat

strain.3

 Operations involving high air temperatures,

radiant heat sources, high humidity, direct physical

contact with hot objects, and strenuous physical

activities have a high potential for inducing heat

strain in employees. Heat strain is highly individual

and cannot be predicted based upon environmental

heat stress measurements. Physiological monitoring

for heat strain becomes necessary when impermeable

clothing is worn, when heat stress screening criteria

are exceeded, or when data from a detailed analysis

(such as the International Standards Organization

[ISO] required sweat rate [SRreq]) shows excess heat

stress.8
Page 6 Health Hazard Evaluation Report No. 2000-0061-2885

One indicator of physiological strain, sustained peak

heart rate, is considered by ACGIH to be the best

sign of acute, high-level exposure to heat stress.

Sustained peak heart rate, defined by ACGIH as 180

beats per minute (bpm) minus an individual’s age,

is a leading indicator that thermal regulatory

control may not be adequate and that increases in

CBTs have, or will soon, occur. Sustained peak

heart rate represents an equivalent cardiovascular

demand of about 75% of maximum aerobic capacity.

During an 8-hour work shift, although sustained

peak demands may not occur, there may still be

excessive demand placed on the cardiovascular

system. These ‘chronic’ demands can be measured

by calculating the average heart rate over the shift.

Decreases in physical job performance have been

observed when the average heart rate exceeds

115 bpm over the entire shift. This level is

equivalent to working at roughly 35% of maximum

aerobic capacity, a level sustainable for 8 hours.8

According to ACGIH, an individual’s heat stress

exposure should be discontinued when any of the

following excessive heat strain indicators occur:

< Sustained (over several minutes) heart rate is in

excess of 180 bpm minus the individual’s age in

years, (180 bpm – age) for those with normal

cardiac performance;

< Core body temperature is greater than 38.0°C

(100.4°F) for unselected, unacclimatized

personnel and greater than 38.5°C (101.3°F) for

medically fit, heat-acclimatized personnel;

< Recovery heart rate at 1 minute after a peak

work effort exceeds 110 bpm; or

< There are symptoms of sudden and severe

fatigue, nausea, dizziness, or lightheadedness.

An individual may be at greater risk of heat strain if:

< Profuse sweating is sustained over several hours;

or

< Weight loss over a shift is greater than 1.5% of

body weight; or

< 24-hour urinary sodium excretion is less than

55 millimoles.

Health Effects of Exposure to

Hot Environments

Heat disorders and health effects of individuals

exposed to hot working environments include (in

increasing order of severity) skin disorders (heat

rash, hives, etc.), heat syncope (fainting), heat

cramps, heat exhaustion, and heat stroke. Heat

syncope (fainting) results from blood flow being

directed to the skin for cooling, resulting in

decreased supply to the brain, and most often strikes

workers who stand in place for extended periods in

hot environments. Heat cramps, caused by sodium

depletion due to sweating, typically occur in the

muscles employed in strenuous work. Heat cramps

and syncope often accompany heat exhaustion, or

weakness, fatigue, confusion, nausea, and other

symptoms that generally prevent a return to work

for at least 24 hours. The dehydration, sodium loss,

and elevated CBT (above 100.4°F) of heat

exhaustion are usually due to individuals performing

strenuous work in hot conditions with inadequate

water and electrolyte intake. Heat exhaustion may

lead to heat stroke if the patient is not quickly cooled

and rehydrated.

While heat exhaustion victims continue to sweat as

their bodies struggle to stay cool, heat stroke victims

cease to sweat as their bodies fail to maintain an

appropriate core temperature. Heat stroke occurs

when hard work, hot environment, and dehydration

overload the body’s capacity to cool itself. This

thermal regulatory failure (heat stroke) is a lifethreatening emergency requiring immediate medical

attention. Signs and symptoms include irritability,

confusion, nausea, convulsions or unconsciousness,

hot dry skin, and a CBT above 106°F. Death can

result from damage to the brain, heart, liver, or

kidneys.11

Prolonged increases in CBT and chronic exposures

to high levels of heat stress are associated with

disorders such as temporary infertility (male and

female), elevated heart rate, sleep disturbance,

fatigue, and irritability. During the first trimester of

pregnancy, a sustained CBT greater than 102.2°F

may endanger the fetus.5

 In addition, one or more
Health Hazard Evaluation Report No. 2000-0061-2885 Page 7

occurrences of heat-induced illness in a person

predisposes him/her to subsequent injuries and can

result in temporary or permanent loss of that person’s

ability to tolerate heat stress.3,10

The level of heat stress at which excessive heat

strain will result is highly individual and depends

upon the heat tolerance capabilities of each

individual. Age, weight, degree of physical fitness,

degree of acclimatization, metabolism, use of

alcohol or drugs, and a variety of medical

conditions, such as hypertension and diabetes, all

affect a person’s sensitivity to heat. At greatest risk

are unacclimatized workers, people performing

physically strenuous work, those with previous heat

illnesses, the elderly, people with cardiovascular or

circulatory disorders (diabetes, atherosclerotic

vascular disease), those taking medications that

impair the body’s cooling mechanisms,b

 people who

use alcohol or are recovering from recent use, people

in poor physical condition, and those recovering

from illness. A core body temperature increase of

only 1.8°F above normal encroaches on the brain’s

ability to function.8

Acclimatization

When workers are first exposed to a hot

environment, they show signs of distress and

discomfort, experience increased CBTs and heart

rates, and may have headaches and/or nausea. On

repeated exposure there is marked adaptation to the

hot environment known as acclimatization.

Acclimatization is the process that allows the body to

begin sweating sooner and more efficiently, reduces

electrolyte concentrations in the sweat, and allows

the circulation to stabilize so that the worker can

withstand greater amounts of heat stress while

experiencing reduced heat strain symptoms.

Acclimatization begins with consecutive exposures

to working conditions for 2 hours at a time, with a

requisite rise in metabolic rate. This will cause the

body to reach 33% of optimum acclimatization by

the fourth day of exposure. Cardiovascular stability

and surface and internal body temperatures will be

lower by day 8 when the body has reached 44% of

optimum acclimatization. A decrease in sweat and

urine electrolyte concentrations are seen at 65% of

optimum (day 10); 93% of optimum is reached by

day 18 and 99% by day 21.8

The loss of acclimatization begins when the activity

under those heat stress conditions is discontinued,

and a noticeable loss occurs after four days. This

loss is usually rapidly made up so that by Tuesday

workers who were off on the weekend are as well

acclimatized as they were on the preceding Friday.

Chronic illness, the use or misuse of pharmacologic

agents, a sleep deficit, a suboptimal nutritional state,

or a disturbed water and electrolyte balance may

reduce the worker’s capacity to acclimatize.8

Dehydration and Fluid

Replacement

When working in hot environments it is often

difficult to completely replace lost fluids as the day’s

work proceeds. High sweat rates with excessive loss

of body fluids may result in dehydration and

electrolyte imbalances.12 Some studies have shown

that even small deficits have adverse effects on

performance.13 Dehydration also negates the

advantage granted by high levels of aerobic fitness

and heat acclimatization.14

Several studies have shown that dehydration

increases CBT during exercise in temperate and hot

environments; a deficit of only 1% of body weight

increases CBT during exercise. As the magnitude

of the water deficit increases, there is an

accompanying elevation in CBT when exercising in

the heat. The magnitude of this elevation ranges

b $-adrenergic receptor blockers and calciumchannel blockers, used to treat hypertension, limit

maximal cardiac output and alter normal vascular

distribution of blood flow in response to heat

exposure. Diuretics, such as caffeine, can limit

cardiac output and affect heat tolerance and

sweating, and antihistamines, phenothiazines, and

cyclic antidepressants impair sweating.3
Page 8 Health Hazard Evaluation Report No. 2000-0061-2885

from 0.2°F to 0.4°F (0.1°C–0.23°C) for every 1%

body weight loss.15 A 2% loss of body weight is

generally accepted as the threshold for thirst

stimulation.16 A 3% decrease in body weight causes

an increase in heart rate, depressed sweating

sensitivity, and a substantial decrease in physical

work capacity.17 Some investigators have reported

that a 4% to 6% water deficit has been associated

with anorexia, impatience, and headache, while a 6%

to 10% deficit is associated with vertigo, shortness

of breath, cyanosis, and spasticity. With a 12%

water deficit, an individual will be unable to swallow

and will need assistance with rehydration. Lethal

dehydration levels are estimated to occur at 15% to

25% lost body weight.18

Palatability of any fluid replacement solution is

important to ensure adequate rehydration. There is

evidence that adding sweeteners to drinks leads

to increased consumption. Glucose-electrolyte

solutions have been shown to facilitate sodium and

water absorption. Also, the glucose in these

solutions provides energy for muscular activity in

endurance events that require vigorous exercise.19

The temperature of the drink will also influence

consumption of fluids. Ideally, fluids should be

ingested at 50°F–60°F in small quantities

(5–7 ounces) and at frequent intervals (every 15–20

minutes).

Hyponatremia (Water

Toxicity)

Most individuals with acute exercise-induced heat

illness are dehydrated with normal to mildly

increased serum sodium and serum osmolality

(hypernatremia). Hyponatremia develops when

serum sodium levels drop below 135 milliequivalents

per liter (mEq/L) and is a life-threatening condition

that has been recognized as a potential health

consequence of endurance activities conducted in hot

environments. Increased water intake prior to and

during activities in hot environments is highly

emphasized to prevent dehydration and heat illness.

However, drinking too much water can lead to

decreased serum sodium concentrations (water

toxicity or hyponatremia), and has been recognized

as an increasing problem among US military

recruits.20

Hyponatremia may occur with hypo-, hyper-, or

normal hydration status.21 Symptomatic

hyponatremia can occur when blood sodium

concentrations decrease to less than 130 mEq/L and

is generally caused by hypervolemia (water

overload) secondary to extensive over-drinking.

Many people with hyponatremia have increased their

total body water by about 1 gallon to achieve such

low serum sodium values.22

Most cases of hyponatremia result from the

inability of the kidneys to excrete an appropriately

dilute urine. The most significant clinical signs of

hyponatremia involve the central nervous system,

and symptoms vary from subtle changes in one’s

ability to think, to decreases in energy levels, to

severe alterations, such as coma or seizure.

Symptoms generally parallel the rate of development

and degree of hyponatremia.23

RESULTS

Workload and Task

Assessments (Heat Stress)

Table 1 lists the WBGTs measured during the study.

Indoor WBGTs ranged from approximately 60°F

to 76°F, and outdoor WBGTs ranged from 61°F

to 91°F. Table 2 lists the estimated metabolic rates

for the five job categories which range from 138

kilocalories per hour (kcal/hr) for ‘other’ activities to

288 kcal/hr for entrant activities and are therefore

considered light to moderate workloads (see

Appendix A for calculations and Appendix D for a

description of the workload categories). Estimated

individual metabolic rates ranged from 111 kcal/hr to

281 kcal/hr (Tables 3–7). According to the criteria,

all of the participants were acclimatized to the

work environment. When compared to the NIOSH

and ACGIH screening criteria, the results indicate

that none of the maintenance crew members were

exposed to excessive heat stress conditions during

the study.
Health Hazard Evaluation Report No. 2000-0061-2885 Page 9

Physiological Monitoring

(Heat Strain)

Twenty-three participants were monitored for heat

strain including nineteen assigned to FSM activities,

two aerospace ground equipment and maintenance

technicians, one refueling mechanic, and one crew

chief not conducting FSM activities. Tables 3–7 list

the results by study day. Sampling times ranged

from 131 minutes to 264 minutes because

participants spent about 2 hours before and after their

FSM activities completing other parts of the study

and were not monitored for heat strain during these

times. Two participants (9%) working on different

days of the study experienced varying degrees of

heat strain. Both participants exceeded the HR

criterion (one for 10% and the other for 22% of

the shift) during and immediately following entry

activities. Most participants reported being hot while

working but the two individuals who developed heat

strain did not report heat strain symptoms such as

weakness, excessive fatigue, nausea, or confusion.

Body weight changes among the 10 weighed

participants ranged from -2.7% to +1.2%, with a

median percent body weight change of -1.0%. Two

participants had greater than 1.5% body weight loss

over their shifts indicating they were at greater risk of

developing a heat-related illness, but neither

individual exceeded the CBT or HR criteria during

their work activities. An additional six participants

(60%), including one with heat strain symptoms,

developed mild dehydration (body weight change of

-1.5% or less) during their activities.

Heat Stress Management at

Seymour Johnson AFB

Seymour Johnson AFB has a supplemental heat

stress policy (SGGB Operating Instruction 48-107)

based on criteria and recommendations from

ACGIH and the Air Force Manual, Personal

Protection and Attack Actions (AFMAN 32–4005).

The instruction, which provides recommended

guidance for the prevention and control of the

adverse effects of heat stress, applies only to those

individuals clothed in military uniforms or civilians

in comparable attire. Environmental monitoring and

reporting of heat stress information are required

during the period from late May to October. The

WBGT index is the basis for the instruction which

outlines WBGT notification procedures and WBGT

work/rest regimens for light, moderate, and heavy

outdoor maintenance or other outside tasks. Bioenvironmental engineering (BEE) personnel are

responsible for obtaining periodic measurements

“as deemed necessary by environmental conditions”

with a WBGT field instrument to determine the

WBGT index. A BEE representative then reports a

recommended WBGT work/rest cycle assuming

moderate work load values. Supervisors are to

implement the recommended work/rest schedule

without sacrificing the overall effectiveness of

the mission. Base public health personnel provide

guidance and conduct briefings on preventing and

controlling heat stress, but only upon request.

Preventive measures covered in the instruction

include an acclimatization schedule, adjustment of

work schedules (performing harder work during

cooler weather, etc.), and encouragement of

frequent breaks. Appropriate amounts and frequency

of water consumption are also covered. Some of

the symptoms of heat stress are discussed in the

instruction, as are some forms of treatment to be

provided by self and/or a ‘buddy.’

DISCUSSION

The study results indicate that those conducting

FSM and other activities were not exposed to heat

stress conditions in excess of the NIOSH and ACGIH

screening criteria. Despite this, eight of ten

participants weighed before and after their activities

became at least mildly dehydrated, and two

participants developed heat strain during their

activities as measured by HR levels that exceeded

ACGIH heat strain criteria.

There were several limitations to this study. Some of

the heat strain monitors failed and some employees

were not able to keep the heart rate sensors in place

during the entire monitoring period; these incidences
Page 10 Health Hazard Evaluation Report No. 2000-0061-2885

are identified in Tables 3–7. Therefore, some study

results may have been over- or underestimated.

Several aspects of the collaborative (JP-8) study may

also have influenced the physiological monitoring

results of the heat stress evaluation. Although

participants worked for 8 hours, they did not work

a ‘normal’ shift because their FSM activities

constituted 50% or less of their time during the

study. The other 50% of the shift involved

completing other components of the jet fuel study for

about 2 hours before and 2 hours after FSM work, in

an air-conditioned building, usually seated and with

lower metabolic rates than those estimated for FSM

activities. Participants were not monitored during

these times. Therefore, the results are not “full-shift”

TWAs and may underestimate the heat stress and

strain levels participants would have experienced had

they conducted FSM activities for a full 8 hours.

Also, some FSM employees, such as those taking

certain medications, and those who were ill,

pregnant, or had a history of strokes or seizures, were

excluded from participating in the JP-8 study. All of

these conditions, however, increase the risk of

developing heat strain and heat-related illnesses, and

the incidence of heat strain during the study may

have been greater if individuals with these conditions

had participated.

Finally, as temperatures in Goldsboro increase

during spring and summer, WBGTs will likely

exceed NIOSH and ACGIH screening criteria

thereby raising the potential for heat strain and

illness among personnel. Heat strain is highly

individual and cannot be predicted based upon

environmental heat stress measurements alone.

Some of the first symptoms of heat strain are

hampered judgement and inability to think critically,

symptoms which usually go unnoticed by the

affected person. The two study participants who

developed heat strain reported feeling hot and sweaty

but did not report noticing any feelings of fatigue,

nausea, weakness, or confusion, which may indicate

an individual lack of severity or lack of awareness of

their heat strain.

The Seymour Johnson AFB heat stress instruction

provides a basis and some good recommendations

for the prevention of heat-related incidents for many

of its civilian and military personnel, including a

work/rest regimen, and acclimatization and hydration

schedules. Frequent breaks are also encouraged

during the hot parts of the day. However, several

elements necessary for the control of heat stress and

strain in all potentially exposed personnel are not

included in the instruction. For example, the

WBGTs and corresponding work/rest regimens

apply only to civilian and military personnel wearing

summer work uniforms. The instruction does not

include clothing adjustment factors for various

types of work clothing. Clothing adjustment factors

are used to lower the WBGT screening criteria to

account for the wearer’s increased heat stress load.

The cloth coveralls worn by those conducting FSM

activities should have a clothing adjustment factor of

+2°F, according to the ACGIH TLV.5

 Adjustments

for other types of clothing should also be included,

except for water vapor- and air-impermeable

encapsulating ensembles (sometimes worn by study

participants and by other Seymour Johnson

personnel). For these types of clothing, the WBGT

is not the appropriate measurement of environmental

heat stress, and therefore, using a clothing

adjustment factor is not appropriate. The NIOSH

criteria document states that the adjusted air

temperature (tadb) should be measured and used

instead of the WBGT (tadb is ambient dry bulb

temperature adjusted for significant solar and long

wave radiant heat loads). When tadb exceeds 68°F,

physiological monitoring in the form of, for example,

oral temperature and/or pulse rate is required.3

 The

ACGIH TLV for heat stress states that physiological

monitoring must be performed when encapsulating

suits or garments that are impermeable or highly

resistant to water vapor or air movement or multiple

layers of clothing are worn.8

 The Seymour Johnson

AFB instruction does not include physiological

monitoring techniques.

The Seymour Johnson AFB heat stress instruction

specifies that WBGTs will be measured and

disseminated to various personnel, but does not

specify how many readings per work shift or where

they should be taken; therefore, the measurements

may not be sufficient. WBGT data for the immediate

work area should be available when using NIOSH

and ACGIH screening criteria.3,5 NIOSH further
Health Hazard Evaluation Report No. 2000-0061-2885 Page 11

recommends that environmental heat measurements

be made at least hourly at the work area during the

hottest part of the shift, during the hottest months of

the year, and whenever a heat wave occurs or is

predicted. If two sequential measurements exceed

the RAL or REL, then work conditions should be

modified by the use of engineering controls, work

practices or other measures until two sequential

measures are at or below the RAL or REL,

whichever are applicable.3

Acclimatization to the work environment and selflimitation of heat stress exposure are two important

ways to prevent heat-related illness. Allowing

employees to become used to working in the heat

significantly increases their ability to do so safely and

also decreases their risk of heat-related illnesses and

unsafe acts. Significant loss of heat acclimatization

can occur after only 4 days when exposure is

discontinued, and if there is no exposure for a week

or so, full acclimatization can require up to three

weeks of continued physical activity under heat stress

conditions.8

 A properly designed and applied heatacclimatization program is especially important for

incoming (PCS) personnel, those on swing shifts or

permanently transferred from nights to days, and

those deployed to regions hotter than those from

which they came. Self-limitation of exposure to the

heat is also vital. During the study, we noticed that

the participants did take unscheduled breaks when

needed. Allowing personnel to take unscheduled

breaks during work in hot weather is an extremely

important part of heat strain and illness prevention

efforts, and it should be emphasized at every hot

weather briefing and continue to be encouraged by

all crew leaders.

The instruction assumes a moderate work load for all

employees, which could over- or underestimate the

potential risks of heat-related illnesses depending

upon the actual work load. In addition, the

instruction does not include methods for reporting

heat stress illnesses (e.g., use of the OSHA 300

Occupational Illness Report), nor is there

information regarding investigation and followup of

heat-related incidences. Finally, the instruction

should provide for mandatory periodic

education/briefing of all potentially affected

personnel on heat stress/strain factors, not just on an

as-requested basis.

CONCLUSIONS

Environmental temperature measurements and work

load assessments showed that during the study

period, those conducting fuel cell maintenance and

other activities were not exposed to heat stress in

excess of the occupational screening criteria.

However, many participants reported feeling hot and

sweating, and a few developed heat strain signs,

including dehydration. Incidences of heat stress and

strain may have been greater if participants had

conducted FSM activities for their full 8-hour shift

and if medically excluded workers had participated.

In addition, the potential for heat stress and strain

increases as temperatures rise during the spring and

summer. Study participants were not aware of

having developed heat strain, indicating a need for

further education and training, and for a

physiological self-monitoring program.

RECOMMENDATIONS

The following recommendations are provided to

enhance the Seymour Johnson AFB heat stress

instruction in order to prevent and reduce future

incidences of heat stress and strain among personnel.

U Add personal monitoring (heat strain) education

to the Seymour Johnson AFB heat stress instruction.

Those conducting FSM and other activities may be

required to wear impermeable clothing and/or may

be exposed to temperatures or physically demanding

work rates which exceed recommended levels.

Therefore, all personnel should be instructed on

monitoring themselves and others for heat strain

signs and symptoms. Personal monitoring is used

in addition to environmental and metabolic

monitoring, and involves checking the heart rate, oral

temperature, extent of body weight loss, and/or

recovery heart rate (see Appendix E). Measurements

should be taken at appropriate intervals covering a
Page 12 Health Hazard Evaluation Report No. 2000-0061-2885

full 2-hour period during the hottest parts of the day,

and again at the end of the workday to ensure a

return to baseline.3

 Use of any of these techniques

should always include the determination of baseline

values for deciding whether individuals are fit to

continue work that day.

U Institute pre-placement and periodic medical

examinations specifically for persons applying for

and working in hot and/or physically demanding

environments. Because aerobic capacities (VO2 max

values) in the working population vary greatly,

persons being considered for jobs requiring high

metabolic demands should be specifically tested.

The examination should be performed by a health

care provider with knowledge of the health effects

associated with work in hot and physically strenuous

environments. The examinations should be

performed to assess the physical, mental, and

medical qualifications of the individuals and to

exclude those with low heat tolerance and/or

physical fitness. The health care provider should

also update the information periodically for people

working in these environments.

U Monitor environmental heat exposures using a

WBGT at or as close as possible to the area where

the worker is exposed. WBGTs in break areas and

other areas the employee may be working that differ

in temperature should also be measured and used to

calculate hourly TWA WBGTs.

U Make at least hourly WBGT measurements

during the hottest part of each shift, during the

hottest months of the year and when heat waves

occur or are predicted to occur. If two sequential

measurements exceed the applicable criteria (RAL or

REL or ACGIH TLV), then work conditions should

be modified until two more sequential WBGT

measurements are within the exposure limits.

U Whenever personnel are required to wear air- and

vapor-impermeable protective clothing, monitor the

dry bulb or adjusted dry bulb temperatures, not the

WBGT, and conduct physiological monitoring

(Appendix E).

U Establish and maintain accurate records of any

heat-related illness events and note the

environmental and work conditions at the time of the

illness. Such events may include repeated accidents,

episodes of heat-related disorders, or frequent healthrelated absences. Job-specific clustering of specific

events or illnesses should be followed up by

industrial hygiene and medical evaluations.

U Encourage personnel to take unscheduled breaks

if they report feeling weak, nauseated, confused,

irritable, and/or excessively fatigued. These heat

strain symptoms warrant immediate removal to a

cooler location, recumbent rest, and administration of

fluids. These and any other signs of overexposure to

the heat should then be reported to the BEE office for

follow-up investigation.

U Hampered judgement and the inability to think

critically, although some of the first symptoms of

heat strain, usually go unnoticed by the person

inflicted. Ensuring that crew members are wellhydrated, nourished, prepared, and not sleepdeprived or working too hard are some of the best

ways to avoid heat strain, unsafe behavior, and poor

job performance.

U Personnel should drink enough water to stay

hydrated and ideally should not lose any body

weight during their shift. Always provide cool

(50°F–60°F) water or any cool liquid (except alcohol

and caffeinated beverages) and encourage them to

drink small amounts frequently, e.g., one cup every

20 minutes. Drinking from individual containers

improves water intake over the use of drinking

fountains. Although some commercial drinks

contain salt, this is not necessary because most

people add enough salt to their diets.

U Encourage workers to eat meals during their

breaks. Minerals and electrolytes lost in sweat are

most readily replaced with a normal diet.

U Workers should be able to monitor their weight so

that they do not become dehydrated during the shift.

Scales should be provided in the break rooms so that

workers can monitor their weight during the shift and

drink more fluids if they begin to loose weight. The
Health Hazard Evaluation Report No. 2000-0061-2885 Page 13

1. Boyles R (sco@cumulus.meas.ncsu.edu)

[2002]. Climate averages for the Goldsboro,

North Carolina area. State Climate Office of

North Carolina, College of Physical and

Mathematical Sciences. Private e-mail message to

Ann Krake (amk3@cdc.gov), October 30.

2. Bernard T (tbernard@hsc.usf.edu) [2002].

Clothing adjustment factor for fuel cell

maintenance crew coveralls. Private e-mail

message to Ann Krake (amk3@cdc.gov), April 15.

3. NIOSH [1986]. Criteria for a recommended

standard: occupational exposure to hot

environments, rev. Cincinnati, OH: U.S.

Department of Health and Human Services, Public

Health Service, Centers for Disease Control,

National Institute for Occupational Safety and

Health, DHHS (NIOSH) Publication No. 86-113.

4. NIOSH [1992]. Recommendations for

occupational safety and health: compendium of

policy documents and statements. Cincinnati, OH:

U.S. Department of Health and Human Services,

Public Health Service, Centers for Disease Control

and Prevention, National Institute for

Occupational Safety and Health, DHHS (NIOSH)

Publication No. 92-100.

5. ACGIH [2002]. 2002 TLVs® and BEIs®:

threshold limit values for chemical substances and

physical agents & biological exposure indices.

Cincinnati, OH: American Conference of

Governmental Industrial Hygienists.

6. CFR [1997]. 29 CFR 1910.1000. Code of

Federal Regulations. Washington, DC: U.S.

Government Printing Office, Office of the Federal

Register.

7. WHO [1969]. Health factors involved in

working under conditions of heat stress. Geneva,

Switzerland: World Health Organization.

Technical Report Series No. 412.

8. ACGIH [2001]. Heat stress and strain:

documentation of TLVs and BEIs, 7th ed.

Cincinnati, OH: American Conference of

Governmental Industrial Hygienists.

9. OSHA [1992]. 88-348 Industrial Glass.

Occupational Safety and Health Review

Commission and Administrative Law Judge

Decisions. World Wide Web

[URL=http://www.osha-slc.gov/REVIEW_data/

D19920421.html]. April 2001.

10. OSHA [1999]. Technical manual, Section III:

chapter 4, heat stress. World Wide Web

[URL=http://www.oshaslc.gov/dts/osta/otm/otm_iii/otm_iii_4.html],

November 2001.

11. Cohen R [1990]. Injuries due to physical

hazards. In: LaDou J, ed. Occupational Medicine.

East Norwalk, CT: Appleton & Lange.

12. Bates G, Gazey C, Cena K [1996]. Factors

affecting heat illness when working in conditions

of thermal stress. J Hum Ergon 25(1):13–20.

13. Sawka MN, Neufer PD [1993]. Interaction of

water bioavailability, thermoregulation, and

exercise performance. In: Marriott BM, ed. Fluid

replacement and heat stress. Washington DC:

National Academy Press, pp. 85–95.

goal should be that the pre-shift and the post-shift

weight should be approximately same.

U Create a ‘buddy’ system so that crew members

can monitor each other for signs of heat illness. A

buddy system will help to ensure that each has had

enough water and food and is feeling ok to continue.

If a coworker appears to be disoriented or confused,

or suffers inexplicable irritability, malaise, or flu-like

symptoms, the worker should be removed for rest in

a cool location with rapidly circulating air and kept

under skilled observation. Immediate emergency

care may be necessary. If sweating stops and the

skin becomes hot and dry, immediate emergency

care with hospitalization is essential.5

REFERENCES
Page 14 Health Hazard Evaluation Report No. 2000-0061-2885

14. Ekblom B, Greenleaf JE, Hermansen L

[1970]. Temperature regulation during exercise

dehydration in man. Acta Physiol Scand

79:475–483.

15. Sawka MN, Knowlton RG, Critz JB [1979].

The thermal and circulatory responses to repeated

bouts of prolonged running. Med Sci Sports

11:177–180.

16. Szlyk PC, Sils JV, Francesconi RP [1989].

Variability in intake and dehydration in young

men during a simulated desert walk. Aviat Space

Environ Med 60:422–427.

17. Candas V, Libert JP, Brandenberger G

[1985]. Hydration during exercise: Effects on

thermal and cardiovascular adjustments. Eur J

Appl Physiol 55:113–122.

18. Adolf EF and Associates [1947]. Physiology

of man in the desert. New York, Interscience.

19. Rolls BJ, Kim S, Fedoroff IC [1990]. Effects

of drinks sweetened with sucrose or aspartame on

hunger, thirst and food intake in men. Physiol

Behav 48:19–26.

20. Gardner JW [2002]. Death by water

intoxication. Military Medicine 167(5):432–434.

21. Roetzheim R [1991]. Overhydration.

Physician Sports Med 19:32.

22. Montain SJ, Latzka WA, Sawka MN [1999].

Fluid replacement recommendations for training in

hot weather. Mil Med 164(7):502–508.

23. Devita MV, Michelis MF [1993].

Perturbations in sodium balance, hyponatremia

and hypernatremia. Clinics in Lab Med

13(1):135–148.
Health Hazard Evaluation Report No. 2000-0061-2885 Page 15

Table 1: WBGT Environmental Temperature Data%

Seymour Johnson AFB, HETA 2000-0061

Date WBGT Range

Inside hangar

Sampling Times

(Time of Highest Temp.)

WBGT Range

Outside hangar

Sampling Times

(Time of Highest Temp.)

5/15/00 59.9–65.1°F 09:00–13:08 (11:12) 61.0–74.3°F 08:31–13:08 (12:54)

5/16/00 61.2–64.8°F 09:44–13:34 (13:08) 64.8–76.8°F 08:48–13:34 (13:00)

5/17/00 63.7–67.3°F 09:54–13:38 (13:19) 63.3–77.2°F 08:33–13:38 (11:58)

5/18/00 69.4–73.6°F 09:40–13:15 (13:15) 68.0–82.9°F 08:50–13:15 (13:08)

5/19/00 71.1–76.1°F 09:48–13:12 (13:12) 78.8–91.0°F 09:41–13:12 (13:11)

%

Actual temperature results are listed. For heat stress exposure analysis, 2°F was added to the temperatures recorded inside 

 the hangar to account for the insulation value of the coveralls worn by participants.2

Table 2: Estimated Metabolic Rates for Fuel Cell Maintenance Activities 

Seymour Johnson AFB, HETA 2000-0061

Activity Estimated Metabolic Rate (kcal/hr)

Entrant 288

Attendant 246

Runner 240

POL 210

Other 138
Page 16 Health Hazard Evaluation Report No. 2000-0061-2885

Table 3: Physiological Measurement Results for 5-15-00

Seymour Johnson AFB, HETA 2000-0061

Study ID (SEY___)

Sampling period

(total activity minutes)

Estimated metabolic

rate (kcal/hour)

Heart rate in excess of

180 bpm minus age "

Average heart rate

(beats per minute)

CBT in excess of

101.3°F "

Average CBT

Change in body weight

2661 10:30–13:07

(158 min.)

*

Did not

exceed

109 bpm Did not

exceed

99.8°F *

3777 10:30–13:03

(154 min.)

*

Did not

exceed

96 bpm Did not

exceed

98.6°F *

7705 10:30–12:40

(131 min.)

*

Did not

exceed

101 bpm Did not

exceed

99.3°F *

"

 These are the main criteria used to determine heat strain. CBT is core body temperature. *

 No body weight was available for this participant, so this parameter could not be obtained.

Table 4: Physiological Measurement Results for 5-16-00

Seymour Johnson AFB, HETA 2000-0061

Study ID (SEY___)

Sampling period

(total activity minutes)

Estimated metabolic rate

(kcal/hour)

Heart rate in excess of 180

bpm minus age "Average heart rate

(beats per minute)

CBT in excess of 101.3°F "

Average CBT

Change in body weight

2487 10:05–13:03

(179 min.)

* Did not

exceed

98 bpm Did not

exceed

99.0°F *

†

3005 08:49–12:48

(240 min.)

*

Did not

exceed

68 bpm Did not

exceed

98.7°F *

†

3088 09:30–13:33

(244 min.)

281 Did not

exceed

78 bpm Did not

exceed

99.0°F -1%

3296 10:05–13:07

(183 min.)

243 Did not

exceed

102 bpm Did not

exceed

99.0°F -0.9%

6324 10:05–13:22

(198 min.)

229 Did not

exceed

99 bpm Did not

exceed

99.8°F -0.5%

"

 These are the main criteria used to determine heat strain. CBT is core body temperature. *

 No body weight was available for this participant, so this parameter could not be obtained. †

 Aerospace ground equipment and maintenance technicians.
Health Hazard Evaluation Report No. 2000-0061-2885 Page 17

Table 5: Physiological Measurement Results for 5-17-00

Seymour Johnson AFB, HETA 2000-0061

Study ID (SEY___)

Sampling period

(total activity minutes)

Estimated metabolic

rate (kcal/hour)

Heart rate in excess of 180

bpm minus age "

(percent of activity)

Average heart rate

(beats per minute)

CBT in excess of

101.3°F "

Average CBT

Change in body weight

†

2747 09:08–12:47

(220 min.)

*

Did not 

exceed

95 bpm Did not

exceed

99.2°F *

†

3073 08:34–12:57

(264 min.)

*

Did not 

exceed

97 bpm Did not

exceed

99.1°F *

3476 09:20–13:02

(223 min.)

266 Did not 

exceed

88 bpm Did not

exceed

99.2°F -1.5%

3514 09:30–13:13

(224 min.)

193 Did not 

exceed

89 bpm Did not

exceed)

99.1°F) 1.2%

3591 09:55–13:34

(220 min.)

226 12:18–13:05

(22%)

101 bpm Did not

exceed

99.2°F -1.0%

"

 These are the main criteria used to determine heat strain. CBT is core body temperature. †

 Aerospace maintenance technicians.

)

 Not all data available because of equipment failure or failure to wear equipment. *

 No body weight was available for this participant, so this parameter could not be obtained.

Table 6: Physiological Measurement Results for 5-18-00

Seymour Johnson AFB, HETA 2000-0061

Study ID (SEY___)

Sampling period

(total activity minutes)

Estimated metabolic rate

(kcal/hour)

Heart rate in excess of 180

bpm minus age "

(percent of activity)

Average heart rate

(beats per minute)

CBT in excess of

101.3°F "

Average CBT

Change in body weight

†

1686 09:30–13:13

(224 min.)

*

Did not 

exceed

120 bpm ) )*

2042 09:10–12:46

(217 min.)

*

Did not 

exceed

94 bpm Did not

exceed

99.4°F *

2139 09:12–13:05

(234 min.)

*

11:49–12:12

(10.3%)

111 bpm Did not

exceed

99.4°F *

2564 09:25–13:06

(222 min.)

111 Did not 

exceed

101 bpm Did not

exceed

100.0°F -2.2%

9811 08:58–13:00

(243 min.)

174 ) )

Did not

exceed

99.8°F -2.7%

†

 Re-fueling mechanic.

"

 These are the main criteria used to determine heat strain. CBT is core body temperature. )

 Not all data available because of equipment failure or failure to wear equipment. *

 No body weight was available for this participant, so this parameter could not be obtained.
Page 18 Health Hazard Evaluation Report No. 2000-0061-2885

Table 7: Physiological Measurement Results for 5-19-00

Seymour Johnson AFB, HETA 2000-0061

Study ID (SEY___)

Sampling period

(total activity minutes)

Estimated metabolic

rate (kcal/hour)

Heart rate in excess of

180 bpm minus age "

Average heart rate

(beats per minute)

CBT in excess of

101.3°F "

Average CBT

Change in body weight

†

1301 08:40–12:35

(236 min.)

*

Did not

exceed

109 bpm Did not

exceed

99.3°F

*

2392 09:45–13:08

(204 min.)

221 Did not

exceed

80 bpm Did not

exceed

98.7°F -1.0%

4148 09:25–13:10

(236 min.)

*

Did not

exceed

101 bpm Did not

exceed

101.1°F

*

6538 09:05–12:55

(231 min.)

*

Did not

exceed

105 bpm Did not

exceed

99.8°F

*

9220 09:05–13:09

(245 min.)

205 Did not

exceed

106 bpm Did not

exceed

100.2°F 0%

†

 Crew chief, not conducting FSM activities.

"

 These are the main criteria used to determine heat strain. CBT is core body temperature. *

 No body weight was available for this participant, so this parameter could not be obtained.
Health Hazard Evaluation Report No. 2000-0061-2885 Page 19

Appendix A: Assessment of Work 

Estimated Metabolic Heat Production Rates by Task Analysis1

A. Body Position and Movement

 Sitting

 Standing

 Walking (uphill)

kcal/min*

0.3

0.6

2.0–3.0 (add 0.8 kcal/meter rise in elevation)

B. Type of Work

Hand work:

light

heavy

Work, one arm:

light

heavy

Work, both arms:

light

heavy

Work, whole body:

light

moderate

heavy

very heavy

Average (kcal/min)

0.4

0.9

1.0

1.8

1.5

2.5

3.5

5.0

7.0

9.0

Range (kcal/min)

0.2–1.2

0.7–2.5

1.0–3.5

2.5–9.0

C. Basal Metabolism 1.0 1.0

Sum of A, B, and C equals estimated metabolic production per task

*For a standard male worker of 70 kg (154 lbs) body weight and 1.8 m2 (19.4 ft2) body surface.

 __________________________________________________________________________

1. Sample calculation for the job of ENTRANT:

Task kcal/min

A. Sitting 0.3 kcal/min

B. Light, whole body work 3.5 kcal/min

C. Basal metabolism 1.0 kcal/min

Metabolic Rate Total 4.8 kcal/min x 60 min/hour = 288 kcal/hour

D. Multiply by the weight correction factor 288 kcal/hour x 1.05‡

Total estimated metabolic rate = 302 kcal/hour>

‡

 The weight correction factor is used when an employee, plus any load they may have to carry, weigh other than

154 lbs. Calculate the factor by dividing the sum of the employee’s current body weight (BW) and the load weight

(LW) by 154 lbs or ([BW + LW] ÷ 154 lbs = weight correction factor). A correction factor for a worker who

weighs 162 lbs and who is not carrying a load is calculated as: (162 lbs + 0 lbs) ÷ 154 lbs = 1.05.

>

 Although not included in the following calculations, a correction factor specific to each employee would be

applied under normal circumstances.
Page 20 Health Hazard Evaluation Report No. 2000-0061-2885

Appendix A: Assessment of Work (continued)

Estimated Metabolic Heat Production Rates by Task Analysis1

2. Sample calculation for the job of ATTENDANT:

Task kcal/min

A. Standing 0.6 kcal/min

B. ‘Type of Work’—heavy work, both arms 2.5 kcal/min

C. Basal metabolism 1.0 kcal/min

Metabolic Rate Total 4.1 kcal/min x 60 min/hour = 246 kcal/hour

D. Multiply by the weight correction factor

 __________________________________________________________________________

3. Sample calculation for the job of RUNNER:

Task kcal/min

A. Walking—can involve some climbing 1.5 kcal/min

B. ‘Type of Work’—light work, both arms 1.5 kcal/min

C. Basal metabolism 1.0 kcal/min

Metabolic Rate Total 4.0 kcal/min x 60 min/hour = 240 kcal/hour

D. Multiply by the weight correction factor

 __________________________________________________________________________

4. Sample calculation for the job of POL:

Task kcal/min

A. Sitting and standing 0.5 kcal/min

B. Light to medium work, both arms 2.0 kcal/min

C. Basal metabolism 1.0 kcal/min

Metabolic Rate Total 3.5 kcal/min x 60 min/hour = 210 kcal/hour

D. Multiply by the weight correction factor

 __________________________________________________________________________

5. Sample calculation for the job of ‘OTHER’:

Task kcal/min

A. Sitting 0.3 kcal/min

B. Light arm movement 1.0 kcal/min

C. Basal metabolism 1.0 kcal/min

Metabolic Rate Total 2.3 kcal/min x 60 min/hour = 138 kcal/hour

D. Multiply by the weight correction factor

 __________________________________________________________________________
a The figures’ curves indicate recommended work/rest regimens for a combination of external heat (measured as wet-bulb globe temperatur

heat. The ‘C’ curve is the Ceiling Limit, indicating that workers should not be exposed to such conditions without adequate heat-protectiv

Health Hazard Evaluation Report No. 2000-0061-2885 Page 21

A

Appendix B: NIOSH Recommended Heat-Stress Alert and Heat-Stress Exposure Limits1, a

Figure 1.RecommendedHeatStressAlertLimits(UnacclimatizedWorkers) Figure 2.RecommendedHeatStressExposureLimits(Acclimatized

Workers)
Page 22 Health Hazard Evaluation Report No. 2000-0061-2885

Appendix C: ACGIH Evaluation Scheme for Heat Stressb

 NO

 YES

 NO

 YES

 NO

 YES

NO

 YES

NO

 YES

b

 From American Conference of Governmental Industrial Hygienists (ACGIH®), Documentation of Threshold Limit

Values and Biological Exposure Indices, 7th Edition. Copyright 2001. Reprinted with permission.

Heat Stress

Expected

Are screening criteria in

Table 2 exceeded?

(See Section 2)

 Implement general controls

(See Section 5)

Perform heat-strain

(physiological) monitoring

(See Section 4)

Implement job-specific

controls

(See Section 5)

Does clothing allow air or

water vapor movement?

(See Section 1)

Low risk

Are data available for

detailed analysis?

(See Section 3)

Excessive heat stress based

on detailed analysis?

(See Section 3)

Excessive heat strain

based on detailed analysis?

(See Section 4)

Continue work,

monitor conditions

Continue work,

maintain controls,

monitor conditions
c From American Conference of Governmental Industrial Hygienists (ACGIH®), Documentation

of Threshold Limit Values and Biological Exposure Indices, 7th Edition. Copyright 2001. Reprinted

with permission.

Health Hazard Evaluation Report No. 2000-0061-2885 Page 23

Appendix D: ACGIH Screening Criteria for Heat Stress Exposurec

Acclimatized (WBGT values in °F) Unacclimatized (WBGT values in °F)

Work

Demands

Light Moderate Heavy Very

Heavy

Light Moderate Heavy Very

Heavy

100% Work 85.1 81.5 78.8 81.5 77.0 72.5

75% Work;

25% Rest

86.9 83.3 81.5 84.2 79.7 76.1

50% Work;

50% Rest

88.7 85.1 83.3 81.5 86.0 82.4 79.7 77.0

25% Work;

75% Rest

90.5 87.8 86.0 85.1 87.8 84.2 82.4 79.7

Notes:

< See work demand categories table below.

< WBGT values represent thresholds near the upper limit of the metabolic rate category.

< If work and rest environments are different, hourly time-weighted averages (TWAs) should be calculated and

used. TWAs for work rates should also be used when the work demands vary within the hour.

< Values in the table assume 8-hour workdays in a 5-day workweek with conventional breaks as discussed in the

Evaluation Criteria section of this report.

< Because of the physiological strain associated with Very Heavy work among less fit workers regardless of

WBGT, criteria values are not provided for continuous work and for up to 25% rest in an hour. The screening

criteria are not recommended, and a detailed analysis and/or physiological monitoring should be used.

The following work load categories, descriptions of work, and estimated energy expenditures help to estimate a

conservative WBGT heat exposure limit for workers conducting these or similar jobs:

Work Categories Example Activities

Resting Sitting quietly; Sitting with moderate arm movements

Light

(<200 kcal/hr)

Sitting with moderate arm and leg movements; Standing with light work at

machine or bench while using mostly arms

Moderate

(200-350 kcal/hr)

Scrubbing in a standing position; Walking about with moderate lifting or

pushing; Walking on level at 3.7 mph while carrying a 6.6 pound load

Heavy

(350-500 kcal/hr)

Carpenter sawing by hand; Shoveling dry sand; Heavy assembly work on a

noncontinuous basis; Intermittent heavy lifting with pushing or pulling (e.g.

pick-and-shovel work)

Very Heavy

(>500 kcal/hr) Shoveling wet sand
Page 24 Health Hazard Evaluation Report No. 2000-0061-2885

Periodic monitoring of the heart rate, oral temperature, extent of body

weight loss, and/or recovery heart rate should always include the

Appendix E: Use of Personal Monitoring Methods to Reduce Heat-Related Illnesses1

U Heart rate: Calculate your heart rate limit by subtracting your age from 180. Your heart rate at peak

work effort should not exceed this number for more than 3 or 4 minutes. If it does, stop work immediately,

find some shade, drink, and rest until your heart rate returns to a more normal pace. Repeat as necessary.

U Oral Temperature: Use a clinical thermometer right after stopping work but before drinking anything.

Try to avoid open-mouth breathing prior to inserting the thermometer, as well. If the oral temperature

taken under the tongue exceeds 99.7°F, shorten the next work cycle by one-third and maintain the same

rest period. An oral temperature of 100.4°F (deep body temperature of 102.2°F) should be considered

reason to terminate exposure even when temperature is being monitored.

U Body Weight: Monitor hydration status on a regular basis. Thirst is a poor indicator of hydration

because significant dehydration has already taken place when the thirst sensation occurs. Workers should

be familiar with their weight when they are fully hydrated and should strive to maintain this weight.

Weight loss should not exceed 1.5% of total body weight in a work day. If it does, fluid and food intake

should increase. (Alcohol and caffeinated beverages should always be avoided when working under heat

stress conditions.) Workers should attempt to re-hydrate themselves until they achieve their baseline

weight. For this purpose, accurate scales should be made available at every work station. Body water loss

can be measured by weighing the worker at the beginning and end of each work day and by using this

equation:

 (pre-activity weight – post-activity weight) ÷ pre-activity weight × 100 = % body weight lost

U Recovery Heart Rate: Following a normal work cycle, compare a pulse rate taken at 3 minutes of

seated rest, P3, with the pulse rate taken at 1 minute of rest, P1.

 Interpret the results using the following

table:

Heart Rate Recovery Pattern P3 P1 minus P3

Excessive heat strain: š90 bpm and  ̃10 bpm

Moderate strain: š90 bpm and š10 bpm

Sufficient recovery: —90 bpm and TM10 bpm
Health Hazard Evaluation Report No. 2000-0061-2885 Page 25

1. NIOSH [1986]. Criteria for a recommended standard: occupational exposure to hot environments, rev.

Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease

Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 86-113.

REFERENCE
DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and PreventionNational Institute for Occupational Safety and Health4676 Columbia ParkwayCincinnati, OH 45226-1998OFFICIAL BUSINESSPenalty for private use $300

Delivering on the Nation's promise: Safety and Health at work for all peoplethrough research and prevention

To receive NIOSH documents or information about

occupational Safety and Health topics

contact NIOSH at:

1-800-35-NIOSH (356-4674) Fax:

1-513-533-8573 E-mail: pubstaft@cdc.gov

or visit the NIOSH web site at:

www.cdc.gov/niosh/homepage.html

S A F E R • H E A L T H I E R • P E O P L ETM