NIOSH HEALTH HAZARD EVALUATION REPORT 

HETA #2006-0196-3036 

Liberty Veterinary Hospital 

Liberty Township, Ohio 

February 2007 

DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Centers for Disease Control and Prevention 

National Institute for Occupational Safety and Health
ii 

PREFACE

The Hazard Evaluation 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 employers 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 Chandran Achutan and Randy L. Tubbs of HETAB, Division of 

Surveillance, Hazard Evaluations and Field Studies (DSHEFS). Field assistance was provided by Donnie 

Booher and Scott Brueck. Desktop publishing was performed by Robin Smith. Editorial assistance was 

provided by Ellen Galloway. 

Copies of this report have been sent to employee and management representatives at Liberty Veterinary 

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

The report may be viewed and printed from the following internet address: 

http://www.cdc.gov/niosh/hhe. Copies may be purchased from the National Technical Information 

Service (NTIS) at 5825 Port Royal Road, Springfield, Virginia 22161. 

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 Health Hazard Evaluation 

Highlights of the NIOSH Health Hazard Evaluation

In March 2006, NIOSH investigators received a management request from the Liberty Veterinary 

Hospital (LVH) to evaluate noise exposures experienced by kennel workers and veterinary staff at LVH 

in Liberty Township, Ohio. Between April and October 2006, noise assessments were conducted on 13 

employees and hearing tests were conducted on 14 employees. 

What NIOSH Did

 We measured personal noise exposures for 

kennel workers. 

 We tested hearing levels of LVH employees. 

What NIOSH Found

 Noise levels exceeded the NIOSH 

recommended exposure limit on ten 

occasions and exceeded the OSHA criteria 

on six. 

 Eleven of the workers have normal hearing 

patterns. 

 Three employees showed hearing loss. 

What LVH Managers Can Do

 Enroll kennel workers in a hearing 

conservation program. 

 Require the use of hearing protectors (ear 

muffs or ear plugs) in the kennels. 

 Maintain ear muffs by making sure they are 

clean and not bent, and replacing the 

cushions every 6 months or sooner if 

necessary. 

 Post signs to show areas with loud noise, 

and have hearing protectors available to 

employees entering these areas. 

 Cover the floors and ceilings with sound 

absorbing materials that are easy to clean 

and disinfect. 

 Make sure that the vacuum on laser 

equipment is functioning as designed.

What LVH Employees Can Do 

 Wear hearing protectors when working in 

the kennels. 

 Follow proper health and safety guidelines 

when treating sick animals such as wearing 

gloves and washing hands frequently. 

 Make sure that electrical appliances do not 

come into contact with water and spills are 

promptly cleaned up. 

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 #2006-0196-3036
iv 

Health Hazard Evaluation Report 2006-0196-3036 

Liberty Veterinary Hospital 

Liberty Township, Ohio 

February 2007 

Chandran Achutan, Ph.D. 

Randy L. Tubbs, Ph.D. 

SUMMARY

On March 27, 2006, the National Institute for Occupational Safety and Health (NIOSH) received a 

management request to conduct a health hazard evaluation (HHE) at Liberty Veterinary Hospital in 

Liberty Township, Ohio. The requestor was interested in knowing the noise levels at the facility from 

barking dogs in boarding kennels or at the hospital. 

Thirteen kennel workers contributed 18 full-shift personal noise dosimetry measures over two days. In 

addition, hearing tests were performed on 14 employees. Ten of the 18 full-shift personal noise dosimetry 

measures collected on kennel workers exceeded the NIOSH Recommended Exposure Limit. Six of these 

measures exceeded the Occupational Safety and Health Administration (OSHA) Action Level and one 

exceeded the OSHA Permissible Exposure Limit. For kennel workers, noise exposures during the 

morning shift were slightly higher than those during the afternoon shift workers, which is consistent with 

the activity level of the dogs. 

Three of the 14 employees showed some degree of hearing loss (> 25 decibels hearing loss). Of the three, 

one was a veterinary staff member, one was a kennel worker, and one was an office worker. Five 

employees with normal hearing showed “notches” (frequency at which there is a dip in the audiogram 

followed by an increase) in their audiograms at 6000 Hertz (Hz). Notches occurring between 3000 to 

6000 Hz may be indicative of the early stages of noise-induced hearing loss (NIHL). In addition, two 

employees with hearing loss had notches at 2000 Hz and 6000 Hz. The notch at 2000 Hz is not consistent 

with NIHL. 

Kennel workers at LVH are exposed to excessive noise levels. Some LVH employees 

have hearing loss but it is not possible to determine whether this is related to noise 

exposures in the kennel. Recommendations are provided to reduce noise exposures and 

prevent further hearing loss. These recommendations include establishing a hearing 

conservation program, installing sound-absorbing materials in kennels, and wearing 

hearing protection devices when entering the kennel area. 

Keywords: NAICS 541940 (Veterinary Services), noise, dose, notch, hearing loss, audiometric 

testing, dog 
Table of Contents 

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

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

Highlights of Health Hazard Evaluation .................................................................................................iii

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

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

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

Noise Exposures to Domestic Animal Handlers ...................................................................................1

Liberty Veterinary Hospital...................................................................................................................1

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

Noise Exposure Assessments..................................................................................................................2

Hearing Loss Assessments......................................................................................................................2

Evaluation Criteria .....................................................................................................................................2

Results and Discussion................................................................................................................................4

Noise Exposure Assessments..................................................................................................................4

Hearing Loss Assessments......................................................................................................................5

Other Observations.................................................................................................................................6

Conclusions..................................................................................................................................................6

Recommendations.......................................................................................................................................7

References....................................................................................................................................................7

Tables .........................................................................................................................................................10

Figures........................................................................................................................................................12
Health Hazard Evaluation Report No. 2006-0196-3036 Page 1 

INTRODUCTION

On March 27, 2006, the National Institute for 

Occupational Safety and Health (NIOSH) 

received a management request to conduct a 

health hazard evaluation (HHE) at Liberty 

Veterinary Hospital (LVH) in Liberty Township, 

Ohio. The requestor was interested in knowing 

the noise levels at the facility from barking dogs 

in boarding kennels or at the hospital. 

On April 4, 2006, NIOSH representatives 

briefed LVH management and employee 

representatives about NIOSH, the HHE 

program, and the scope of the NIOSH 

evaluation. This was followed by a tour of the 

facility. On April 10 and 14, 2006, NIOSH 

investigators measured noise exposure for 

employees working throughout the facility. On 

October 13, 2006, NIOSH investigators returned 

to the facility to conduct hearing tests for the 

employees. 

BACKGROUND

Noise Exposures to Domestic 

Animal Handlers

Veterinary hospital workers, animal shelter 

employees, workers at facilities that board 

animals, and police officers with canine partners 

are potentially exposed to excessive 

occupational noise levels from barking dogs. 

However, few studies have examined noise 

exposures and the potential for hearing loss 

among these workers. One study measured noise 

levels as high as 108 decibels on an A-weighted 

scale (dBA) in veterinary establishments.1

 

Another study looking at noise exposures to 

veterinary staff in an outdoor animal shelter 

showed noise exposures in excess of the NIOSH 

recommended exposure limit (REL) for 

occupational noise.2

 This evaluation was 

conducted in the aftermath of Hurricane Katrina 

in St. Bernard Parish, Louisiana, and is not 

representative of typical veterinary staff work 

activity. Two studies examined noise exposures 

and hearing loss among police officers in the 

canine unit.3,4 Both studies found that police 

officers were exposed to excessive noise from 

canines, and some officers had hearing loss. The 

design of these studies did not enable 

investigators to determine whether observed 

hearing loss was associated with occupational 

noise exposures. 

Liberty Veterinary Hospital 

Established in 1998, Liberty Veterinary Hospital 

provides medical care to small pets, primarily 

cats and dogs. The practice offers outpatient 

treatment, routine surgery such as spaying and 

neutering of animals, and boarding. The main 

work areas are an office/waiting area, hospital 

area, kennel area, and a dog grooming area. 

Pet owners check their pets in at the front office. 

The office staff members notify the kennel-area 

staff that an animal has arrived for boarding in 

the kennel or the veterinary staff that an animal 

is ready for its examination. Sometimes, office 

workers go to the kennels to collect an animal. 

The veterinary staff includes three veterinarians, 

two veterinary assistants, four veterinary 

technicians, and a laboratory assistant. They 

start work between 7:30 a.m. and 10:30 a.m. and 

end between 4:00 p.m. and 7:00 p.m. The 

veterinary assistants and technicians assist the 

veterinarians by performing initial examinations, 

dressing wounds, tracking animals as they are 

brought in and out of surgery, and restraining 

animals undergoing treatment. 

Depending on how busy the practice is, there are 

between five and seven part-time kennel 

workers. The kennel workers work the morning 

shift (7:00 a.m. to 12:45 p.m.) or the afternoon 

shift (1:15 p.m. to 7:00 p.m.) The kennel area is 

divided into a small animal area and a large 

animal area. During the NIOSH evaluation there 

were about 27 large dogs and 18 small dogs; the 

facility was at full capacity. The main 

responsibilities of the kennel workers are to feed 

and walk the animals, and to clean their cages. 

The workers prepare food for the animals in a 

kitchen adjacent to the kennels. The kennel area 

leads to an outside play area for the dogs. Most 
Page 2 Health Hazard Evaluation Report No.2006-0196-3036 

animals are taken out to play or for a walk at 

least once a day. In a grooming area next to the 

kennels, dogs are bathed in a bath tub, dried 

initially with a wet vacuum and then with a 

blower attached to their cage, and groomed. The 

clinic also has a groomer on staff. 

METHODS

Noise Exposure Assessments 

Thirteen kennel workers contributed 18 personal 

noise dosimetry measures over a 2-day period. 

Quest® Electronics Model Q-300 Noise 

Dosimeters (Oconomowoc, Wisconsin) were 

worn by the employees while they performed 

their daily activities. Samples were collected 

throughout work shifts that ranged from 2 to 8 

hours. The noise dosimeters were placed in the 

pocket of the employees’ scrubs and a small 

remote microphone was fastened to the wearer’s 

shirt at a point midway between the ear and the 

outside of the shoulder. A windscreen provided 

by the dosimeter manufacturer was placed over 

the microphone during recordings. At the end of 

the sampling period, the dosimeter was removed 

and paused to stop data collection. The 

information stored in the dosimeters was 

downloaded to a personal computer for 

interpretation with QuestSuite® Professional 

computer software. The dosimeters were 

calibrated before and after the measurement 

periods according to the manufacturer’s 

instructions. 

Real-time noise monitoring was done with a 

Quest Electronics Model 2400 Sound Level 

Meter (SLM). The instrument was set to 

measure noise levels between 70 and 140 dB, on 

an A-weighted slow-response scale. The SLM 

was calibrated before and after the measurement 

periods according to the manufacturer’s 

instructions. Real-time spectral analysis was 

done with a Larson-Davis Laboratory Model 

2800 Real-Time Analyzer and a Larson-Davis 

Laboratory Model 2559 1⁄2-inch random 

incidence response microphone (Provo, Utah). 

The analyzer allows for the analysis of noise 

into its spectral components in a real-time mode. 

The 1⁄2-inch diameter microphone has a 

frequency response range (± 2 dB) from 4 Hertz 

(Hz) to 21 kilohertz (kHz) that allows for the 

analysis of sounds in the region of concern. Onethird octave bands consisting of center 

frequencies from 25 Hz to 20 kHz were 

integrated for 5–30 seconds and stored in the 

analyzer. 

Hearing Loss Assessments 

All employees were invited to take the hearing 

tests. Workers reported to the NIOSH mobile 

test facility parked at the LVH property. Most 

employees were tested prior to starting their 

shift; others were asked to wear ear muffs until 

they had their hearing tested. Informed consent 

was obtained from each participant before they 

completed a short questionnaire about work 

history and self assessment of their hearing 

ability. 

A Tremetrics (Eden Prairie, Minnesota) Model 

AR 901 hearing booth and OSCAR 7 ElectroAcoustic Ear and Octave Monitor (Eden Prairie, 

Minnesota) provided an acoustic environment 

for hearing testing. The area was controlled for 

conversations and other extraneous noises. 

Hearing tests were administered with a 

Tremetrics Model HT Wizard Audiometer that 

had received a routine calibration check within 

the past year. Hearing tests were conducted by 

one of the investigators who has current 

certification from the Council for Accreditation 

in Occupational Hearing Conservation 

(CAOHC). The audiometer tested the pure-tone 

frequencies of 500, 1000, 2000, 3000, 4000, 

6000, and 8000 Hz in the computerized mode in 

each ear, left ear first. 

Test results for each participant were interpreted 

immediately after testing, and explained to the 

participant. In addition, each participant was 

sent a letter summarizing his or her results along 

with a copy of the audiometric test. 

EVALUATION CRITERIA

The primary sources of evaluation criteria for 

noise in the workplace are: (1) the NIOSH 

REL,5

 and (2) the U.S. Department of Labor, 
Health Hazard Evaluation Report No. 2006-0196-3036 Page 3 

Occupational Safety and Health Administration 

(OSHA) Permissible Exposure Limit (PEL).6

Employers are encouraged to follow the more 

protective NIOSH REL, although they are 

required to adhere to the OSHA limits for 

compliance purposes. 

Noise-induced hearing loss (NIHL) is an 

irreversible, sensorineural condition that 

progresses with exposure. Although hearing 

ability declines with age (presbycusis) in all 

populations, exposure to noise produces hearing 

loss greater than that resulting from the natural 

aging process. This noise-induced loss is caused 

by damage to nerve cells of the inner ear 

(cochlea) and, unlike some conductive hearing 

disorders, cannot be treated medically.7

 While 

loss of hearing may result from a single 

exposure to a very brief impulse noise or 

explosion, such traumatic losses are rare. In 

most cases, NIHL is insidious. Typically, it 

begins to develop at 4000 or 6000 Hz (the 

hearing range is 20 Hz to 20000 Hz) and spreads 

to lower and higher frequencies. Often, material 

impairment has occurred before the condition is 

clearly recognized. Such impairment is usually 

severe enough to permanently affect a person’s 

ability to hear and understand speech under 

everyday conditions. Although the primary 

frequencies of human speech range from 200 Hz 

to 2000 Hz, research has shown that the 

consonant sounds, which enable people to 

distinguish words such as “fish” from “fist,” 

have still higher frequency components.8

The dBA is the preferred unit for measuring 

sound levels to assess worker noise exposures. 

The dBA scale is weighted to approximate the 

sensory response of the human ear to sound 

frequencies near the threshold of hearing. The 

decibel unit is dimensionless, and represents the 

logarithmic relationship of the measured sound 

pressure level to an arbitrary reference sound 

pressure (20 micropascals, the normal threshold 

of human hearing at a frequency of 1000 Hz). 

Decibel units are used because of the very large 

range of sound pressure levels which are audible 

to the human ear. Because the dBA scale is 

logarithmic, increases of 3 dBA, 10 dBA, and 20 

dBA represent a doubling, tenfold increase, and 

hundred-fold increase of sound energy, 

respectively. It should be noted that noise 

exposures expressed in decibels cannot be 

averaged by taking the simple arithmetic mean. 

The OSHA standard for occupational exposure 

to noise (29 CFR 1910.95)6

 specifies a 

maximum PEL of 90 dBA for a duration of 

8 hours per day. The regulation, in calculating 

the PEL, uses a 5 dB time/intensity trading 

relationship, or exchange rate. This means that a 

person may be exposed to noise levels of 

95 dBA for no more than 4 hours, to 100 dBA 

for 2 hours, etc. Conversely, up to 16 hours 

exposure to 85 dBA is allowed by this exchange 

rate. The duration and sound level intensities can 

be combined in order to calculate a worker's 

daily noise dose according to the formula: 

Dose = 100 X (C1/T1 + C2/T2 + ... + Cn/Tn ), 

where Cn indicates the total time of exposure at a 

specific noise level and Tn indicates the 

reference duration for that level as given in 

Table G-16a of the OSHA noise regulation. 

During any 24-hour period, a worker is allowed 

up to 100% of his daily noise dose. Doses 

greater than 100% exceed the OSHA PEL. 

The OSHA regulation has an additional action 

level (AL) of 85 dBA; an employer shall 

administer a continuing, effective hearing 

conservation program when the 8-hour timeweighted average (TWA) value exceeds the AL. 

The program must include monitoring, 

employee notification, observation, audiometric 

testing, hearing protection devices (HPDs), 

training, and record keeping. All of these 

requirements are included in 29 CFR 1910.95, 

paragraphs (c) through (o). Finally, the OSHA 

noise standard states that when workers are 

exposed to noise levels in excess of the OSHA 

PEL of 90 dBA, feasible engineering or 

administrative controls shall be implemented to 

reduce the workers’ exposure levels. 

NIOSH, in its Criteria for a Recommended 

Standard, proposes exposure criteria of 85 dBA 

as a TWA for 8 hours, 5 dB less than the OSHA 

standard.9

 The criterion also uses a more 
Page 4 Health Hazard Evaluation Report No.2006-0196-3036 

conservative 3 dB time/intensity trading 

relationship in calculating exposure limits. Thus, 

a worker can be exposed to 85 dBA for 8 hours, 

but to no more than 88 dBA for 4 hours or 91 

dBA for 2 hours. The NIOSH REL for 12-hour 

exposure is 83 dBA or less. 

Audiometric evaluations of workers are 

conducted in quiet locations, preferably in a 

sound-attenuating chamber, by presenting pure 

tones of varying frequencies at threshold levels 

(i.e., the level of a sound that the person can just 

barely hear). Audiograms are displayed and 

stored as tables or charts of the hearing levels 

(HL) at specified test frequencies.10 Zero dB HL 

represents the hearing level of an average, 

young, normal hearing individual. In OSHAmandated hearing conservation programs, 

thresholds must be measured for pure-tone 

signals at the test frequencies of 500, 1000, 

2000, 3000, 4000, and 6000 Hz. Individual 

employee’s annual audiograms are compared to 

their own baseline audiogram to determine the 

amount of standard threshold shift (STS) that 

might have occurred between the two tests. 

Specifically, OSHA states that an STS has 

occurred if the average threshold values at 2000, 

3000, and 4000 Hz have increased by 10 dB or 

more in either ear when comparing the annual 

audiogram to the baseline audiogram.6

 The 

NIOSH recommended threshold shift criterion is 

a 15-dB shift at any frequency in either ear from 

500–6000 Hz measured twice in succession.9

Practically, the criterion is met by immediately 

retesting an employee who exhibits a 15-dB shift 

from baseline on an annual test. If the 15-dB 

shift persists on the second test, a confirmatory 

follow-up test should be given within 30 days of 

the initial annual examination. Both of these 

threshold shift criteria require at least two 

audiometric tests. In cases where only one 

audiogram is available, a criterion has been 

proposed for single-frequency impairment 

determinations.11 It employs a lower fence (the 

amount of hearing loss necessary before a 

hearing handicap is said to exist) of 25 dB HL. 

With this criterion, any person who has a 

hearing level of 26 dB HL or greater at any 

single frequency is classified as having some 

degree of hearing loss. The degree of loss can 

range from mild (26–40 dB HL) to profound 

(>90 dB HL). 

The audiogram profile is a plot of the hearing 

test frequencies (x-axis) versus the hearing 

threshold levels (y-axis). For many workers, the 

audiogram profile tends to slope downward 

toward the high frequencies with an 

improvement at the audiogram’s highest 

frequencies, forming a “notch.”12 A notch in an 

individual with normal hearing may indicate the 

early onset of hearing loss. Although there is no 

universal criterion to define what constitutes a 

“notch,” several mathematical models that 

attempt to identify notches are presented in the 

scientific literature.13,14,15 The relative strength 

and weaknesses of these models have also been 

reviewed.16 For this evaluation, a notch is 

defined as the frequency where the hearing level 

is preceded by an improvement of at least 10 dB 

and followed by an improvement of at least 5 

dB. The notch from occupational noise can 

occur between 3000 and 6000 Hz, depending on 

the frequency spectrum of the noise, and the 

anatomy of the individual’s ear.17,18 It is 

generally accepted that a notch at 4000 Hz 

indicates occupational hearing loss.19 On the 

other hand, some researchers have argued that 

the notch at 6000 Hz may not be a good marker 

for occupational hearing loss because it is 

widely seen in young adults and others with 

little documented occupational noise exposure.20

An individual may have notches at different 

frequencies in one or both ears.12 

RESULTS AND 

DISCUSSION

Noise Exposure Assessments 

The length of the workday at LVH may vary 

depending on the number of dogs and cats being 

boarded in the kennel, number of part-time 

workers, and the veterinarians’ surgery schedule. 

The noise exposure evaluation was conducted 

during spring break and thus represented a 

“worst-case” scenario because of the large 

number of animals being boarded. 
Health Hazard Evaluation Report No. 2006-0196-3036 Page 5 

Thirteen employees contributed 18 full-shift 

personal dosimetry measures over the 2-day 

evaluation. Ten of the 18 measures exceeded the 

NIOSH REL. Six of these measures also 

exceeded the OSHA AL while one exceeded the 

OSHA PEL (Table 1). TWA noise levels for the 

kennel workers ranged from 91 to 95 dBA as 

calculated by the NIOSH criterion. Noise 

exposures for the morning shift kennel workers 

were slightly higher than those for the afternoon 

shift workers. This is probably because the dogs 

are excitable first thing in the morning when the 

lights are turned on and the workers make their 

rounds. By the time the afternoon shift starts, the 

dogs have been fed; during the evaluation they 

were observed resting. One of the morning shift 

kennel workers who spent about 1–2 hours 

doing administrative work had a lower noise 

exposure than that of the worker who spent all 

the time in the kennel area or the kennel’s 

kitchen area. The TWA noise exposures for 

workers in the hospital area ranged from 70 to 

84 dBA as calculated by the NIOSH criterion. 

One of the veterinary assistants who stood in for 

the groomer had an exposure of 88.5 dBA 

(225% dose) for the 2 hours that she worked on 

the day of the evaluation. This job function is 

not typical for veterinary staff. 

Spot noise measurements and real time noise 

exposure profiles for employees and spectral 

noise data are presented in Table 2 and Figures 

1–7 respectively. Figure 1 shows that employees 

who primarily work in the hospital area 

(veterinarians, veterinary assistants, and 

veterinary technicians) have relatively low noise 

exposures (below 85 dBA). Their main source of 

noise exposure is the occasional barking dog in 

the hospital area, depicted in peaks in Figure 1. 

Some of these dogs are brought in for outpatient 

treatment; others are temporarily placed in cages 

pending surgery and during post-surgery 

recovery. The veterinary staff described 

potential excessive noise from surgical 

equipment. Figure 2 shows spectral noise data 

from a vacuum system used for laser surgery 

and ultrasonic dental equipment. The noise 

contributions from these sources were well 

below 70 dBA and are not a significant noise 

source. Figure 3 shows the noise exposures of a 

veterinary assistant who primarily bathed dogs 

for the 2 hours that she worked on the day of the 

assessment. The high exposures are a result of 

the barking of a couple of dogs in the grooming 

area, as well as a wet vacuum and a blower used 

to dry the dogs. The wet vacuum had noise 

levels as high as 91 dBA when measured using a 

sound level meter. Figure 4 shows spectral data 

from the blower and the wet vacuum. Kennel 

workers consistently sustained noise levels as 

high as 105 dBA, as depicted in Figure 5. One of 

the kennel workers reached 71% of the NIOSH 

REL after the first 17 minutes in the kennel. If 

similar exposures occur throughout the day, this 

worker would exceed the NIOSH REL in a short 

time. Another kennel worker exceeded the daily 

allowable dose (116%) in 8 minutes. These 

calculations, based on the more protective 

NIOSH criterion, show that administrative 

controls such as job rotation will not be effective 

for kennel workers. Noise exposures were 

slightly higher in the morning when workers 

cleaned cages, and fed and walked the dogs, 

compared to the afternoon, when some of the 

dogs napped briefly. Regardless, levels for all 

kennel workers were found to exceed the 

NIOSH REL (Table 1). Figure 6 depicts typical 

spectral noise data in the kennel area. The 

loudest noise exposures (in excess of 85 dBA) 

occurred between 400 and 2000 Hz. The 

maximum noise level was 98 dBA. The kennel 

workers power wash the kennels as frequently as 

needed. Spectral noise data taken during power 

washing (Figure 7) showed high noise levels in 

the range where NIHL can occur (2000 to 6000 

Hz). However, these data were collected with 

the dogs present, so the barking of the dogs 

added to the noise from the power washing. 

All but one of the kennel workers reported 

headaches that they attributed to occupational 

noise exposure. One kennel worker mentioned 

having ringing in the ears in the past. 

Hearing Loss Assessments 

Hearing tests were offered to all LVH 

employees. Fourteen LVH employees were 

available to take the test. Of the 14, eight 

workers were veterinary staff (veterinarians, 

veterinary technicians and assistants, and 
Page 6 Health Hazard Evaluation Report No.2006-0196-3036 

laboratory assistants), two were office workers 

(receptionist, manager) and four were kennel 

workers. Two of the veterinary staff had worked 

as kennel workers in previous jobs. The mean 

age of the 14 employees was 32 years (range = 

19–55). They had worked at LVH from 3 

months to 8 years (mean = 3 years). Nine 

employees had worked with dogs (as groomer, 

groomer’s assistants, kennel workers, veterinary 

office worker) in previous other jobs (mean = 7 

years). The median hearing test results and the 

inter-quartile ranges (a measure of variability) 

are shown in Figure 8. 

Three of the 14 employees showed some degree 

of hearing loss. Of the three, one was a 

veterinary staff member, one was a kennel 

worker, and one was an office worker. Five 

employees with normal hearing showed notches 

in their audiograms at 6000 Hz. Notches 

occurring between 3000 to 6000 Hz may be 

indicative of the early stages of NIHL. In 

addition, two employees with hearing loss had 

notches at 2000 Hz and 6000 Hz. The notch at 

2000 Hz is not consistent with NIHL. Table 3 

shows the relationship between hearing loss and 

notch formation for LVH employees. 

This evaluation cannot establish an association 

between animal shelter workers with hearing 

loss and the loudness of the dogs because (1) the 

sample size is too small to make definitive 

conclusions, (2) hearing loss typically develops 

over a relatively long period of time, and most 

of the LVH employees are relatively young, and 

(3) exposure to noise from hobbies and factors 

such as genetics and illnesses that affect hearing 

may affect the results. However, continued 

exposure to excessive noise over a working 

lifetime can potentially result in NIHL.9

 

Noise control strategies in dog kennels are 

complicated. Sound-absorbing materials such as 

spray-on foam and fibrous mineral wool, which 

are usually used in industry and other indoor 

settings to reduce noise exposures, are not 

appropriate in kennels because they are difficult 

to clean while maintaining dryness in order to 

avoid mold and mildew. One approach may be 

to use sound-absorbing material on surfaces that 

do not need to be cleaned routinely, such as 

ceilings. Acoustical ceiling tiles that are 

waterproof and washable can be installed to 

reduce noise.21 In addition, floors can be covered 

with rubber mats to absorb sound from the 

barking dogs and to reduce noise from feeding 

and drinking dishes hitting on hard (concrete and 

tile) surfaces. These approaches may offer some 

reduction in noise levels, but do not eliminate 

the direct noise path from the dog to the worker. 

A noise survey should be conducted after these 

controls are in place to determine if personal 

noise exposures to workers are reduced. If there 

are plans for building a new facility or 

expanding the current facility, an acoustical 

engineer can assist in designing dog 

confinement areas that may reduce noise 

exposures. 

Other Observations

NIOSH investigators noticed veterinary staff not 

wearing gloves when handling syringes or 

holding wounded animals near their wounds. 

Zoonotic agents such as viruses, bacteria, and 

parasites can transmit diseases from animals to 

humans.22,23 The vacuum attached to the laser 

device used for surgery was not capturing all of 

the emission produced by the procedure. A 

pungent odor and smoke plume were evident in 

the surgical suite. In the grooming area, the 

electrical blower was in close proximity to 

puddles of water. This can pose an electrical 

hazard if electrical circuits are not protected by 

ground fault interrupters, and pose a slip hazard 

if the water is not dried promptly. 

CONCLUSIONS

This evaluation showed that kennel workers at 

LVH are exposed to hazardous noise levels. 

Some of the workers who participated in this 

evaluation showed signs of hearing loss. 

However, because of the small sample size, 

inability to control for other sources of noise, 

and the relative youth of the workers with 

respect to time needed to develop hearing loss, it 

is not possible to determine whether the 
Health Hazard Evaluation Report No. 2006-0196-3036 Page 7 

observed hearing loss is related to noise 

exposure at the kennel. 

RECOMMENDATIONS

Based on the observations and findings of this 

evaluation, the following recommendations are 

offered to better protect the hearing of the 

kennel workers with LVH and to address other 

health and safety issues noted during the 

evaluation: 

1. Establish a hearing loss prevention 

program for the kennel workers. The 

basic elements of the program should, at 

a minimum, meet the requirements for a 

hearing conservation program as 

outlined in the OSHA hearing 

conservation amendment (29 CFR 

1910.95). Other sources for defining 

effective hearing conservation programs 

are also available.12,24,25

2. Wear hearing protection devices (ear 

muffs or ear plugs) when working in the 

kennel areas. Employees should be 

trained on the proper fit, selection, and 

maintenance of hearing protectors. For 

example, ear plugs should be deeply 

inserted into ear canals, and cushions on 

ear muffs should not be cracked or 

creased, and the head bands not sprung. 

3. Place warning signs that identify loud 

noise areas on doors and require anyone 

entering these areas for extended periods 

to wear hearing protectors. 

4. Consider using sound-absorbing 

materials that are easy to keep clean on 

ceilings and floors of dog kennels. 

5. Follow health and safety precautions 

recommended by the National 

Association of State Public Health 

Veterinarians such as hand washing and 

use of gloves with respect to touching 

blood, body fluids, secretions, 

excretions, mucous membranes, and 

non-intact skin.22

6. Consult an acoustical engineer when 

considering any future design changes to 

the facilities to determine whether noise 

exposures can be reduced. 

7. Contact the manufacturer of the laser 

equipment to make sure the vacuum is 

functioning as designed to effectively 

remove surgical smoke. 

8. Make sure that puddles of water are 

promptly dried and that electrical 

appliances do not come in contact with 

water. 

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as an environmental problem. J Am Vet Med 

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 2. Achutan C [anticipated 2007]. 

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relief operations in the aftermath of Hurricane 

Katrina. J Occup Environ Hyg (accepted). 

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noise as a risk factor for hearing loss among 

police dog handlers. Occup Med (London) 54 

(8):535-539. 

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technical assistance report: Cincinnati Police 

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U.S. Department of Health and Human Services, 

Public Health Service, Centers for Disease 

Control, National Institute for Occupational 

Safety and Health, NIOSH Report No. 2006-

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 5. NIOSH [1992]. Recommendations for 

occupational safety and health: compendium of 

policy documents and statements. Cincinnati, 

OH: U.S. Department of Health and Human 

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Disease Control and Prevention, National 

Institute for Occupational Safety and Health, 

DHHS (NIOSH) Publication No. 92-100. 

 6. CFR [1992]. 29 CFR 1910.95. Code of 

Federal Regulations. Washington, DC: U.S. 

Government Printing Office, Office of the 

Federal Register. 

 7. Ward WD, Royster LH, Royster JD 

[2000]. Anatomy & physiology of the ear: 
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normal and damaged hearing. In: Berger EH, 

Royster LH, Royster JD, Driscoll DP, Layne M, 

eds. The noise manual. 5th ed. Fairfax, VA: 

American Industrial Hygiene Association, pp 

101–122. 

 8. Suter AH [1978]. The ability of mildly 

hearing-impaired individuals to discriminate 

speech in noise. Washington, DC: U.S. 

Environmental Protection Agency, Joint 

EPA/USAF study, EPA 550/9–78–100, AMRL–

TR–78–4. 

 9. NIOSH [1998]. Criteria for a 

recommended standard: occupational noise 

exposure (revised criteria 1998). Cincinnati, OH: 

U.S. Department of Health and Human Services, 

Centers for Disease Control and Prevention, 

National Institute for Occupational Safety and 

Health, DHHS (NIOSH) Publication No. 98-

126. 

 10. ANSI [1996]. American national standard 

specification for audiometers. Melville, NY: 

Acoustical Society of America, American 

National Standards Institute, ANSI S3.6-1996. 

 11. Eagles EL, Hardy WG, Catlin FI [1968]. 

Human communication: The public health 

aspects of hearing, language, and speech 

disorders (NINDB monograph #7). Washington, 

D.C. Government Printing Office, USPHS 

Publication 1745. 

 12. Suter AH [2002]. Hearing conservation 

manual. 4th ed. Milwaukee, WI: Council for 

accreditation in Occupational Hearing 

Conservation. 

 13. Dobie RA, Rabinowitz PM [2002]. 

Change in audiometric configuration helps to 

determine whether a standard threshold shift is 

work-related. Spectrum 19 (Suppl 1):17. 

 14. Niskar AS, Kieszak SM, Holmes AE, 

Esteban E, Rubin C, Brody DJ [2001]. 

Estimated prevalence of noise-induced hearing 

threshold shifts among children 6 to 19 years of 

age: The Third National Health and Nutrition 

Examination Survey, 1988-1994, United States. 

Pediatrics 108(1):40-43. 

 15. Cooper JC, Owen JH [1976]. Audiologic 

profile of noise-induced hearing loss. Arch 

Otolaryngol 102:148-150. 

 16. Rabinowitz PM, Dobie RA [2003]. Use of 

the audiometric configuration to determine 

whether hearing loss is noise-induced: can 

“notch criteria” help? NHCA Spectrum 20(1):8-

11. 

 17. ACOM [1989]. Occupational noiseinduced hearing loss. ACOM Noise and Hearing 

Conservation Committee. J Occup Med 31:996. 

 18. Osguthorpe JD, Klein AJ [2001]. 

Occupational hearing conservation. Clinical 

Audiology 24(2):403-414. 

 19. Prince M, Stayner L, Smith R, Gilbert S 

[1997]. A re-examination of risk estimates from 

the NIOSH Occupational Noise and Hearing 

Survey (ONHS). J Acous Soc Am 101:950-963. 

 20. McBride DI, Williams S [2001]. 

Audiometric notch as a sign of noise induced 

hearing loss. Occup Environ Med 58:46-51. 

 21. Carter T [2006]. Ask the builder: 

acoustical ceiling tiles–sound properties. 

[http://www.askthebuilder.com/B148_Acoustica

l_Ceiling_Tiles_Sound_Properties.shtml]. Date 

accessed: January 22, 2007. 

 22. National Association of State Public 

Health Veterinarians [2006]. Compendium of 

veterinary standard precautions: zoonotic 

disease prevention in veterinary personnel. 

[http://www.nasphv.org/Documents/VeterinaryP

recautions.pdf]. Date accessed: January 29, 

2007. 

 23. Weber DJ, Rutala WA [1999]. Zoonotic 

infections. Occup Med 14:247-284. 

 24. NIOSH [1996]. Preventing occupational 

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Centers for Disease Control and Prevention, 

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110. 

 25. Royster JD, Royster LH [1990]. Hearing 

conservation programs: practical guidelines for 

success. Chelsea, MI: Lewis Publishers. 
Page 10 Health Hazard Evaluation Report No.2006-0196-3036 

TABLES

Table 1 

Full-Shift Personal Dosimetry for 18* LVH Employees 

 Number of 

Samples 

Shift** Noise Levels (Percent Dose) 

 OSHA AL OSHA PEL NIOSH REL 

Kennel Workers 6 Morning 47.0 – 118.2 44.5 – 114.8 509.3 – 1442.5 

3 Afternoon 24.2 – 74.4 22.5 – 68.7 262.5 – 797.0 

Veterinary Staff† 8 Morning 1.0 – 26.1 0.2 – 24.7 8.0 – 225.2 

1 Afternoon 1.9 1.1 15.1 

*A sample collected on a veterinary technician was voided because of equipment malfunction, and is not reported. 

**Morning shifts start between 7:00 a.m. and 10:30 a.m. and end between 12:45 p.m. and 4:00 p.m., evening shifts start at 1:15 

p.m. and end at 7:00 p.m. 

The various dose percentages are the amounts of noise accumulated during a work day, with 100% representing the maximum 

allowable daily dose. 

†Veterinary staff includes veterinarians, veterinary assistants, veterinary technicians and a lab assistant 

LVH: Liberty Veterinary Hospital 

OSHA: Occupational Safety and Health Administration 

NIOSH: National Institute for Occupational Safety and Health 

AL: Action Level 

PEL: Permissible Exposure Limit 

REL: Recommended Exposure Limit 
Health Hazard Evaluation Report No.2006-0196-3036 Page 11 

Table 2 

 Spot Area Noise Measurements (dBA) in the Laboratory, Kennel, and Grooming Areas 

Area Day 1 Day 2 

Large-dog kennel (morning) 93.7 – 107.1 100.7 – 103.9 

Large-dog kennel (afternoon) 105.8 100.0 – 112.0 

Small-dog kennel (morning) 97.2 – 105.4 92.7 

Small-dog kennel (afternoon) 102.6 86.1 – 103.0 

Laboratory < 60 60.0 – 70.0 

Grooming (blower on cage) < 78 75.9 

Grooming (wet vacuum at tub) No Exposure 90.9 

Grooming (wet vacuum and blower) No Exposure 90.3 

Ultrasonic dental No Exposure 66.6 – 67.5 

Vacuum on laser No Exposure 65.3 – 67.1 

Kennel kitchen (door closed) 69.0 – 76.0 78.0-81.4 

Kennel kitchen (door fully opened) 88.0 91.0 

Kennel kitchen (door partially open) 78.0 75.0 – 86.0 

 dBA: decibels on an A-weighted scale 

Table 3 

Relationship between Hearing Loss (> 25 decibels), and Notch Formation 

among LVH Employees 

Employee ID Hearing Loss Notch (Hertz) 

 Left Ear Right Ear Left Ear Right Ear

A No No No 6000 

B No No 6000 No 

C No No No No 

D No No No No 

E Mild No No No 

F Mild to Moderate No 6000 No 

G No No No No 

H No No 6000 6000 

I No No No 6000 

J No No No No 

K No No No No 

L No No 6000 No 

M Mild to Moderate Mild No 2000 

N No No No No 

 LVH: Liberty Veterinary Hospital 
Page 12 Health Hazard Evaluation Report No.2006-0196-3036 

FIGURES

Figure 1 

Profile of Noise Exposure for Veterinary Staff 

65

70

75

80

85

90

95

100

105

7:12 9:36 12:00 14:24 16:48 19:12

Time (hh:mm)

Noise Level (dBA)

Veterinary Technician Veterinarian Veterinary Assistant
Health Hazard Evaluation Report No.2006-0196-3036 Page 13 

Figure 2 

Spectral Noise from Laser Vacuum and Ultrasonic Dental Equipment 

0

10

20

30

40

50

60

70

31.5

63

125250500

1000200040008000

16000

Frequency [Hz]

Noise Level [dB]

vacuum on laser ultrasonic dental

Figure 3 

Profile of Noise Exposure during Bathing of Dogs 

65

70

75

80

85

90

95

100

105

110

7:55 8:24 8:52 9:21 9:50 10:19

Time (hh:mm)

Noise Level (dBA)
Page 14 Health Hazard Evaluation Report No.2006-0196-3036 

Figure 4 

Spectral Noise Data from Vacuum and Blower in the Grooming Area 

0

10

20

30

40

50

60

70

80

90

31.5

63

125250500

1000200040008000

16000

Frequency (Hz)

Noise Level [dB]

Wet vacuum Blower on cage

Figure 5 

Typical Noise Profile for a Kennel Worker 

60

65

70

75

80

85

90

95

100

105

110

6:43 7:55 9:07 10:19 11:31 12:43

Time (hh:mm)

Noise Level (dBA)
Health Hazard Evaluation Report No.2006-0196-3036 Page 15 

Figure 6 

Typical Spectral Noise Data in the Kennel Area 

0

10

20

30

40

50

60

70

80

90

100

31.5

63

125250500

1000200040008000

16000

Frequency [Hz]

Noise Level [dB]

Aisle near cage #16 Aisle near cage #20

Figure 7 

Spectral Noise Data when Power Washing Cages and with Dogs Barking Simultaneously 

0

20

40

60

80

100

120

31.5

6

3

12

5

2

5

0

5

0

0

10

0

0

2

0

0

0

4

0

0

0

8

0

0

0

16

0

0

0

Frequency [Hz]

Noise Level [dB]

Power washing dog cages
Page 16 Health Hazard Evaluation Report No.2006-0196-3036 

Figure 8 

Median Hearing Levels and Inter-Quartile Ranges for LVH Employees 

0

2

4

6

8

10

12

14

16

012345678

Frequency (kHz)

Median Hearing Level [dB]

Left Ear Right Ear

 

LVH: Liberty Veterinary Hospital 

Frequency (kHz) Left Ear Right Ear 

 25th percentile 75th percentile 25th percentile 75th percentile 

0.5 10 20 5 15 

1 5 15 5 10 

2 5 10 5 10 

3 -5 10 0 10 

4 0 15 0 10 

6 5 25 0 20 

8 0 10 0 15 
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