HETA 2000-0305-2848

City of Long Beach Police Department

Long Beach, California

Steven M. Schrader, Ph.D.

Michael Breitenstein, B.S.

Brian Lowe, Ph.D.

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

ppy py y gy 

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.

ppy py y gy 

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

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 Steven M. Schrader, Ph.D. and Michael Breitenstein of Biomonitoring and

Health Assessment Branch (BHAB) and Brian Lowe, Ph.D., Organizational Science and Human Factors

Branch (OSHFB), Division of Applied Research and Technology (DART). Field assistance was provided

by John Clark, Laboratory Technician, BHAB. Desktop publishing was performed by Nichole Herbert.

Review and preparation for printing were performed by Penny Arthur.

Copies of this report have been sent to employee and management representatives at the Long Beach Police

Department and the OSHA Regional Office. This report is not copyrighted and may be freely reproduced.

Single copies of this report will be available for a period of three years from the date of this report. To

expedite your request, include a self-addressed mailing label along 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 employerin a prominent place accessible to the employees

for a period of 30 calendar days.
iv

Health Hazard Evaluation Report 2000-0305-2848

City of Long Beach Police Department

Long Beach, California

May 2001

Steven M. Schrader, Ph.D.

Michael Breitenstein, B.S.

Brian Lowe, Ph.D.

SUMMARY

In May 2000, the National Institute for Occupational Safety and Health (NIOSH) received a request for a

health hazard evaluation (HHE) from a representative of the International Association of Machinists and

Aerospace Workers (IAM) Local 1930. The health concerns were genital numbness, sexual dysfunction,

and feet problems in the Marine Bicycle Patrol, Long Beach Police Department, Long Beach, California.

From July 10 to 22, 2000, NIOSH researchers visited the City of Long Beach, California, to evaluate the

Marine Bicycle Patrol officers and the possible health effects associated with biking. Twenty-nine biking

officers participated in at least part of the study. Five non-biking men from the Long Beach area were used

as the comparison group.

Fourteen of the fifteen (93%) bikers responding to questions on genital numbness indicated that at times they

experienced numbness in their buttocks, scrotum, testicles, or penis during or after riding their bicycles. This

numbness occurred after 10 minutes to 3 hours of riding and lasted from 5 minutes to 24 hours.

Blood hormone levels and semen quality were normal in the officers providing samples.

The male study participants were asked to wear a Rigiscan® erection monitoring device for 2 nights. The

number of sleep erections was not affected indicating the basic neurophysiology of erectile function was

intact in biking officers. However, measures of erection quality were lower in the biking officers. The

percent of the sleeping time a man had an erection was statistically reduced (p=0.0097) in the biking police

(26.2%) compared to men (42.8%) not riding bicycles. As the measured pressure between the officer and

the bicycle seat increased, the percent sleeping time the individual had an erection was decreased. Similarly,

as the average number of hours per day an officer was on his bike and the average number of days a week

the officer rode his bike increased, the percent sleeping time with an erection decreased.

This study indicates that the pressure between the biking officer and the bicycle seat is related to numbness

in the genitals and subclinical impairment of erectile function. Blood hormone levels and semen quality were

normal in the officers providing samples. Recommendations to minimize or eliminate these specific problems

reported by biking officers include minimizing pressure to the perineum from the bicycle seat nose. This can

be achieved by taking rest periods off of the bicycle saddle and enuring proper bicycle fit. The police

department is encouraged to investigate the feasibility of using bicycle seats without a nose or other extension.

Keywords: SIC 9221 (Police Protection). Bicycle, bike, seat, erectile dysfunction
TABLE OF CONTENTS

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

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

Highlights of the NIOSH Health Hazard Evaluation ........................................ iii

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

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

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

Methods ............................................................... 1

Results ....................................................................... 3

Discussion .................................................................... 3

Conclusions ................................................................... 4

Recommendations ............................................................... 4

References .................................................................... 4
Health Hazard Evaluation Report No. 2000-0305-2848 Page 1

INTRODUCTION

In May 2000, the National Institute for

Occupational Safety and Health (NIOSH)

received a request for a health hazard evaluation

(HHE) from a representative of the International

Association of Machinists and Aerospace

Workers (IAM) Local 1930. The IAM expressed

two health concerns among the Marine Bicycle

Patrol, Long Beach, California. The first concern

was numbness and pain of male genitals

associated with bicycle riding. The second was

numbness and pain of the foot while pedaling.

From July 10 to 22, 2000, NIOSH researchers

visited the City of Long Beach, California, to

evaluate these problems. Bicycle riding activities

were monitored, personal seat and foot pressure

measurements were measured, and erectile

dysfunction and semen quality were assessed.

Each study participant received a copy of their

bicycle seat pressure measurements, erectile

function measurements, hormone concentrations,

and semen analyses results, along with a letter of

explanation, in December 2000.

BACKGROUND

In 1998, the Occupational Health Clinic for the

City of Long Beach, California, reported that 15 of

23 biking policemen answered a self-administered

questionnaire indicating they had some symptoms

of genital numbness, groin pain, or impotence.

There have been scientific reports indicating that

biking may cause genital numbness and

impotence.1,2,3,4

The Marine Patrol of the Long Beach Police

Department is a bicycle unit of approximately

30 security officers who patrol the city-owned

marinas. The primary patrol is on a bicycle. The

city also employs a bicycle patrol which serves the

more traditional role of bicycling policemen in the

community. These officers have volunteered for

this duty. The city bicycle police officers are

represented by the Long Beach Police Officers

Association (POA). The POA was included in

the opening and closing conferences and biking

officers (approximately 15) represented by the

POA were asked to participate in the study.

While most participated in the pressure

measurements, only two men represented by the

POA participated in the reproductive health

assessment.

The Marine Patrol offices spent an average of six

hours per day, five days per week, riding bicycles.

The officers spend much of their time riding on

wooded piers and ramps. Most of the riding time

was slow riding, seated on the saddle. The

officers often interacted with the public or

conducted their work while seated and stationary

on the bike, often with a hand on a pole or boat for

balance. Less often, the bikers were observed in

the “high speed” pedaling to get from one area to

another quickly.

Mountain bikes were supplied by the city for each

officer. The newer bikes had full (front and rear)

suspension systems to absorb the vibrations of the

rough terrain. All of the officers had been

supplied with a split bicycle seat (Serfas®) in

response to earlier complaints of genital numbness

and sexual function problems. The officers

indicated that they have had training in bicycling

techniques. Each officer has his own bicycle and

has adjusted it to his comfort.

METHODS

All biking police officers were assigned by their

supervisor to attend one of nine presentations by

NIOSH staff describing the study. The

presentations were held at a hotel meeting room

and all officers were assigned a meeting time by

their supervisor while they were on duty. After a

15 minute presentation the NIOSH project officer

met with each officer in private to answer

questions and request informed consent.

All male officers were asked to participate in all

aspects of the study. These included bike seat

pressure measures, foot pressure measurements,

foot exam, hormonal analysis, self-administered

work/health questionnaire, self-administered

sexual function questionnaire, and Rigiscan®

Rigidity Assessment System (device to evaluate
Page 2 Health Hazard Evaluation Report No. 2000-0305-2848

erectile function). For men who were interested

in or concerned with their semen quality a “mailin” semen collection container was provided.

Female bikers were asked to participate in the

bike seat pressure measurements, foot pressure

measurements, and the foot exam.

The professional staff of a local hotel were asked

to participate as a comparison group.

A self-administered work and medical history

questionnaire was distributed to each male study

participant. The completed questionnaires were

then mailed, by the participant, to NIOSH for data

entry and analysis.

Follicle stimulating hormone (FSH), luteinizing

hormone (LH), and testosterone, were measured,

since endocrine insufficiency could affect

reproductive and sexual function. The hormones

were measured in a sample of venous blood

collected from the participant’s arm.5

A semen analysis kit was available to interested

participants if they were concerned about their

fertility. This kit contained a collection jar and

shipping container. The men produced a semen

sample by masturbation, at home, directly into the

jar. The jar was placed into the shipping container

and mailed to the contract laboratory for analysis.

The analysis consisted of sperm count, sperm

morphology (shape), and presence of white blood

cells.

Sexual function was assessed by the International

Index of Erectile Function Questionnaire

6

 and the

Rigiscan® Rigidity Assessment System.7 Again,

the questionnaire was self-administered and

returned by mail to NIOSH for data entry and

analysis. The Rigiscan® was used to assess

erectile function during the normal sleep patterns

of the participants. It is a computerized monitor

worn on the leg, with two loops connected to the

penis, one on the base the other on the tip, used to

study the penis during sleep. Men have penile

erections during their sleep, and the intent of the

study was to compare the Marine Patrol and

comparison group with respect to the number of

erections and the percent of sleep time with an

erection.8 For reliable results the participants

were asked not to ejaculate for one day before the

test, not to drink coffee, tea, caffeinated soft

drinks, or alcoholic beverages for 2 hours before

bedtime, and not to take sedatives, tranquilizers,

muscle relaxants, or sleeping pills the night of the

test - all these have been linked with impaired

sexual function.

Scientists believe that the pressure between the

biker and the bicycle seat obstructs the nerves and

blood vessels in the perineum (area between anus

and the scrotum).9,10 The pressure exerted

between the partic ipant and the bicycle seat was

measured with a pressure assessment system

(Force Sensitive Applications [FSA], Vista

Medical LTD, Winnipeg, Canada). Each bicycle

was placed into a stationary bicycle trainer

(Magturbo Ergo, Minoura), then the pressure mat

was aligned on the bike seat, and the officer

mounted his bike and pedaled in a normal riding

position and in a pursuit position. Each position

was monitored for approximately 30 seconds.

The officer dismounted his bike and the seat

pressure mat was disconnected from the FAS

computer system. A foot pressure mat was then

attached. The foot pressure mat was inserted into

the officer’s shoe. The officer again mounted his

bike and pedaled in both normal and pursuit modes

for approximately 30 seconds each. Cadence,

intensity and resistance were self selected and not

recorded The foot pressure measurements were

stored on the computer system. A brief selfadministered questionnaire about possible foot pain

and numbness, with drawings of the top and

bottom of the feet to indicate the location of these

concerns, was distributed to all study participants.

Arrangements were made with a local foot

specialist to examine the feet of these bikers. The

foot specialist was only available one day and only

8 officers were able to be examined.

Subsequently, a physical therapist with expertise in

bicycle biomechanics and foot pain examined the

pressure measurements and foot complaints.

From these data he provided recommendations for

minimizing foot pain and numbness.

A convenience sample of 5 non-biking men was

recruited from among city employees and hotel

staff to serve as a comparison group. These men
Health Hazard Evaluation Report No. 2000-0305-2848 Page 3

agreed to have the Rigiscan® and hormone

assessment.

Bikers and non-bikers participating in the erectile

function tests were paid for their time and

inconvenience. 

Statistical analyses were conducted using SAS

System for Windows (Version 8.01; Cary, North

Carolina). Analysis of variance between the

comparison group and the biking officers was

calculated using the GLM procedure. Correlations

between variables was calculated using Pearson

correlation procedures.

RESULTS

Thirty-six biking officers from the Long Beach

Police Department attended the presentation of

the study across nine different sessions. Twentyeight officers had pressure measurements taken

while riding their bikes. Seventeen officers

provided blood samples for hormone analyses.

Rigiscan® measurements were conducted on 16

biking officers. The equipment malfunctioned and

data was not recorded on 2 of these officers. Five

biking officers provided semen samples; all sperm

counts, WBC, and sperm morphologies were

normal. Nineteen biking officers answered the

Work and Medical Questionnaire and International

Index of Erectile Function Questionnaire.

Fourteen of the fifteen participants responding to

questions about numbness (93%) indicated that at

times they experience numbness in their buttocks,

scrotum, testicles, or penis during or after riding

their bicycles. The numbness usually occurred

after an average of 1 hour and 41 minutes of

riding (range 10 minutes to 3 hours) and lasted an

average of 2 hours and 35 minutes (range

5 minutes to 24 hours). 

All blood hormone values were normal.

The International Index of Erectile Function

Questionnaire did not identify any men (biking

officers or comparison group) with overt sexual

dysfunction. The Rigiscan® data did provide

information on sleep erections. The number of

sleep erections (non-biker 3.8 ± 1.3; biker 4.6 ±

1.7; p=0.38) was not affected indicating the basic

neurophysiology of erectile function was intact in

biking officers. However, measures of erection

quality were lower in the biking officers.

The percent of the sleeping time a man had an

erection was statistically reduced (p=0.0097) in

the biking police (26.2% ± 10.15%) compared to

men (42.8% ± 19.00%) not riding bicycles. The

percent sleeping time a man had an erection is

negatively correlated (r=-0.43; p=0.07) with the

pressure between the officer and the bicycle seat.

(As seat pressure increases the erection time

decreases). Similarly, the percent sleeping time a

man had an erection is correlated (negative) with

the average hours a police officer was on his bike

(r=-0.45; p=0.05) and the average number of days

a week the officer rode his bike (r=-0.58; p=0.01).

The bicycle police officers sat on the saddle such

that approximately 22% of the load (weight)

supported by the saddle was distributed on the

nose of the saddle and 78% of the weight on the

saddle was distributed on the “sit bone” portion of

the saddle. These percentages corresponded to

average pressures of 2.3 ± 1.7 and 2.9 ± 1.0

pounds per square inch (psi) on the nose and sit

bone portion of the saddle, respectively. Even

though the nose supported a lower percentage of

the load on the saddle (less than one quarter of the

weight on the saddle is distributed on the nose), its

smaller surface area acts to increase the localized

pressure on the rider in this region. Scientists

believe that pressure exerted on the nose of the

saddle is most detrimental to the nerves and blood

vessels in the perineum.1,2,3

Five of the eleven (45%) biking officers answering

the questions about foot problems indicated that

they had some foot pain and/or numbness.

Measures of foot pressure were taken with inshoe pads. Measures were compartmentalized in

six distinct zones. The foot was split into fore foot

and rear foot sectors. The fore and rear foot

sectors were then subdivided to represent distinct

pressure zones of the foot. The average regional

pressures were 14.1, 13.5, and 11.2 psi, for the

lateral, mid-line, and medial regions of the fore-
Page 4 Health Hazard Evaluation Report No. 2000-0305-2848

foot and 5.9, 6.7, and 4.1 psi for the lateral, midline, and medial regions of the hind-foot.

DISCUSSION

The significant difference observed between the

comparison group and the biking officers for the

percent of sleep time a man has an erection would

indicate that the biking offic ers have reduced

erectile function. This interpretation is limited,

however, by the self-selected nature of the

comparison group. Because this measurement is

also significantly correlated with average number

of hours the biker rides and the amount of

pressure on the bicycle, this increases the

likelihood that the subclinical erectile impairment is

related to the officer’s biking occupation. The

observed differences are probably not due to the

normal variation, because the number of sleep

erections was not affected indicating the basic

erectile function control by the brain was intact in

biking officers.

Our research team noticed that many officers

conducted much of their work unnecessarily “on

the saddle.” Many of the officers talked with the

public, rested, and made general observations

while still on the saddle. Many officers remain on

the seat with their feet on the ground or the pedals

and a hand supporting them against a pole, boat, or

anything that would support them. This increases

the amount of time that pressure is unnecessarily

applied to the nerves and blood vessels of the

perineum.

The average saddle nose pressure measured in

this study was approximately 2.3 psi. The findings

of Rogers11 as cited by Armstrong12 suggest that

ischemic tissue injury would occur at

approximately 280 minutes (< 5 hours) of

exposure to localized pressure of 2.3 psi. Some

officers exhibited average saddle nose pressures

that exceeded 4.64 psi during the seat pressure

testing. This level of pressure corresponds to a

tolerance time of less than 156 min (~ 2.5 hours).

The ball of the foot and the heel bear most of the

weight of the body while standing and walking.

The shape and placement of the bicycle pedal

moves the weight (pressure) from these

anatomical structures to the entire forefoot. The

use of a hard-sole shoe redistributes the weight

(pressure) from the entire forefoot back to the ball

of the foot. This is similar to walking and thus a

“healthier posture.” The hard sole shoe also

allows the localization of the power of pedaling

allowing optimal biking performance.

CONCLUSIONS

This study indicates that biking officers’ genital

discomfort is related to pressure exerted by their

bicycle seats. While according to the International

Index of Erectile Function Questionnaire, none of

the bikers studied were impotent, the decrement in

erectile quality and the high percent of men

complaining of genital numbness could be an

indication of a developing reproductive health

problem.

RECOMMENDATIONS

Although relevant published data are not available,

the use of a bicycle seat without a nose would

presumably result in less pressure on the perineum

and the underlying nerves and blood vessels and

thereby help to prevent these symptoms.

Although a scientific study has not been conducted

on the usefulness of their training, professional

organizations of biking police officers

(International Police Mountain Bike Association &

Law Enforcement Bicycle Association) offer

courses in bicycling techniques which may prove

to be beneficial to biking officers.

Biking officers should be encouraged to dismount

the bike when they are not riding. Other work

activities and rest breaks should not be conducted

while straddling the bike seat.

The proper adjustment of the bicycle seat and

bicycle itself is very important.13

The pressure to the foot was primarily on the fore

foot, but was not localized on the ball of the foot.

Most officers were using soft soled shoes. Biking
Health Hazard Evaluation Report No. 2000-0305-2848 Page 5

1. Solomon S, Cappa KG [1987]. Impotence

and Bicycling. Postgraduate Medicine 81:99-102.

2. Andersen KV, Bovim G [1997]. Impotence

and Nerve Entrapment in Long Distance Amateur

Cyclists. Act Neurol Scand 95:233-240.

3. Schwarzer U, Wiegand W, Bin-Saleh A,

Lotzerick H, Kahrmann G, Klotz T, Engelmann U

[1999]. Genital Numbness and Impotence Rate in

Long Distance cyclists. Abstracts of the

American Urological Association.

4. LaSalle MD, Wen C, Choi M, Salimpour P,

Adelstein A, Gholami S, Krane RJ, Goldstein I

[1999]. “You Don’t Have to Ride in the Tour de

France”: Erectile Dysfunction in 81 Consecutive

Riders. Abstracts of the American Urological

Association.

5. Schrader SM, Turner TW, Breitenstein MJ,

Simon SD [1993]. Measurement of Male

Reproductive Hormones for Field Studies. JOM

35:574-576.

6. Rosen RC, Riley A, Wagner G, Osterloh IH,

Kirkpatrick J, Mishra A [1997]. The International

Index of Erectile Function (IIEF): A

Multidimensional Scale for Assessment of Erectile

Dysfunction. Urology 49:822-830.

7. Burris AS, Banks SM, Sherins RJ [1989].

Quantitative Assessment of Nocturnal Penile

Tumescence and Rigidity in Normal Men Using a

Home Monitor. J Androl.10:492-497.

8. Levine LA, Carroll RA [1994]. Nocturnal

Penile Tumescence and Rigidity in Men without

Complaints of Erectile Dysfunction using a New

Quantitative Analysis Software. J Urology

152:1103-1107.

9. Kerstein MD, Gould SA, French-Sherry E,

Pirman C [1982]. Perineal Trauma and

Vasculogenic Impotence. J Urology 127:57.

10. Broderick GA [1999]. Bicycle Seats and

Penile Blood Flow: Does the Type of Saddle

Matter? Abstracts of the American Urological

Association.

11. Rogers J [1973]. Annual report of

Rehabilitation Engineering Center. Rancho Los

Amigos Hospital, University of Southern

California, pp. 71-73.

12. Armstrong TJ [1985]. Mechanical

considerations of skin in work. American Journal

of Industrial Medicine, 8, 463-472. 

13. Mellion MB [1991]. Common Cycling

Injuries: Management and Prevention. Sports

Medicine 11:52-70.

shoes would redistribute the pressure to ball of the

foot which should bear most of the weight. The

pedaling cadences used by the officers during

testing appeared to be much slower than the

recommended 80-100 revolutions per minute

(rpms). Increasing the pedaling cadence with a

lower pedal resistance can reduce foot

numbness.13 Officers should use the gearing of

the bikes to pedal at 80-100 rpms when practical.

REFERENCES
iii

Highlights of the NIOSH Health Hazard Evaluation

Evaluation of the City of Long Beach Police Department

NIOSH conducted a health hazard evaluation of genital numbness, sexual dysfunction, and feet problems in

the Marine Bicycle Patrol, of the Long Beach Police Department in Long Beach, California.

What NIOSH Did

# We surveyed officers about their work

conditions and their health.

# We measured the pressure between the rider

and the bicycle seat.

# We tested blood samples for reproductive

hormones.

# We measured semen quality.

# We measured erectile function.

# We measured the pressure on the foot while

pedaling.

What NIOSH Found

# 93% of the biking officers reported numbness

while riding.

# Blood hormone levels were normal in the biking

officers.

# The men who provided semen samples had

normal semen.

# Officers’ erection quality was related to the

number of hours he rode his bike and increased

pressure between the rider and the bicycle seat

was related to lower quality of the man’s

erection.

What the City of Long Beach

Police Departments Can Do

# Consider purchasing bicycle seats which do not

have a nose or other extension which may place

excessive pressure on the perineum.

# Train each officer on proper riding techniques

and proper dynamics between the rider and the

bicycle.

# Consider providing a hard-sole mountain- or

touring-style bicycling shoe.

# Consider utilizing (in-house or out-source)

bicycle fit standards for bicyclists.

What the City of Long Beach

Police Officers Can Do

# Dismount the bike when not riding.

# Don’t straddle the bike seat during rest breaks

or work activities not requiring sitting on the

bike; instead dismount the bike.

# If pain or numbness occurs, get off the bike and

walk the bike a few minutes until pain and

numbness are relieved.

# Utilize gears that allow cadences near 90 rpms.

# Utilize frequent methods of pressure relief for

feet.

# Perform regular/daily stretching excercises for

calf, hamstrings, quadriceps, and gluteals.

# Know and record basic bic ycle measurements

to ensure proper fit to the bicycle.

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 # 2000-0305-

2848

Highlights of the NIOSH Health Hazard Evaluation
For Information on Other

Occupational Safety and Health Concerns

Call NIOSH at:

1–800–35–NIOSH (356–4674)

or visit the NIOSH Web site at:

www.cdc.gov/niosh

!

Delivering on the Nation’s promise:

Safety and health at work for all people

through research and prevention