NIOSH HEALTH HAZARD EVALUATION REPORT 

HETA #2006-0212-3035 

Kenton County Animal Shelter 

Covington, Kentucky 

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, Srinivas Durgam, Judith Eisenberg, and Lynda Ewers. 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 the Kenton County 

Animal Shelter 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 April 2006, NIOSH investigators received a management request from the Kenton County Animal 

Shelter (KCAS) in Covington, Kentucky to evaluate noise exposures and potential hearing loss 

experienced by animal shelter workers at KCAS. Between April and October 2006, noise assessments 

were conducted on nine animal shelter workers, and hearing tests were performed on 10 workers. 

What NIOSH Did

 We measured personal noise exposures for 

animal shelter workers. 

 We tested hearing levels of animal shelter 

workers. 

What NIOSH Found

 Noise levels exceeded the NIOSH 

recommended exposure limit six times. The 

OSHA criteria were not exceeded. 

 Six of the ten workers who got tested have 

normal hearing. 

 Four employees showed some hearing loss.

What KCAS Managers Can Do

 Enroll employees in a hearing loss 

prevention program. 

 Require the use of hearing protectors in the 

kennel areas. 

 Maintain ear muffs by making sure they are 

clean and the head bands are not sprung. 

 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. 

What KCAS Employees Can Do 

 Wear hearing protectors when working in 

the kennel areas. 

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 #2006-0212-3035
iv 

Health Hazard Evaluation Report 2006-0212-3035 

Kenton County Animal Shelter 

Covington, Kentucky 

February 2007 

Chandran Achutan, Ph.D. 

Randy L. Tubbs, Ph.D. 

SUMMARY

On April 13, 2006, the National Institute for Occupational Safety and Health (NIOSH) received a 

management request for a health hazard evaluation (HHE) from the Kenton County Animal Shelter 

(KCAS) in Covington, Kentucky. The HHE request asked NIOSH to assess the noise levels experienced 

by the animal shelter workers from barking dogs. On April 18 and 19, 2006, NIOSH investigators 

measured noise exposure levels for animal shelter workers. NIOSH investigators returned to the facility 

on October 12, 2006, to conduct hearing tests for all animal shelter workers. 

Nine animal shelter workers contributed 18 full-shift personal dosimetry measures over 2 days. Hearing 

tests were performed on 10 workers. Six of the 18 (33%) of the personal noise dosimetry measures 

exceeded the NIOSH recommended exposure limit. The Occupational Safety and Health Administration 

(OSHA) action level and the OSHA permissible exposure limit were not exceeded. Exposures were 

highest for workers who cleaned the dog kennels in the morning. Exposures were lower for employees 

who rotated between cleaning cat cages, providing food to the animals, and staffing the front desk. 

Four of the 10 workers tested showed some degree of hearing loss. Five employees with normal hearing 

showed “notches” (frequency at which there is a dip in the audiogram followed by an increase) at 4000 

Hertz (Hz) and 6000 Hz in one or both ears. Notches occurring between 3000 to 6000 Hz may be 

indicative of the early stages of noise-induced hearing loss (NIHL). In addition, one employee with 

hearing loss had notches at 2000 Hz, 4000 Hz, and 6000 Hz. The notch at 2000 Hz is not consistent with 

NIHL. 

Some of the animal shelter workers at KCAS are exposed to excessive noise levels. Some 

of the workers have some hearing loss but it is not possible to assess whether it is related 

to noise exposure at the kennel. Recommendations are provided to reduce noise 

exposures and prevent further hearing loss. These recommendations include establishing 

a hearing loss prevention program, installing sound-absorbing materials in kennels, and 

wearing hearing protection devices when entering the kennel area. 

Keywords: NAICS 813312 (Environment, Conservation and Wildlife Organizations), noise, dose, 

animal shelter, audiometric testing, hearing loss, 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

Kenton County Animal Shelter .............................................................................................................1

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

Noise Assessment.....................................................................................................................................1

Hearing Loss Assessment .......................................................................................................................2

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

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

Conclusions..................................................................................................................................................5

Recommendations.......................................................................................................................................5

References....................................................................................................................................................6

Tables ...........................................................................................................................................................8

Figures..........................................................................................................................................................9
Health Hazard Evaluation Report No. 2006-0212-3035 Page 1 

INTRODUCTION

On April 13, 2006, the National Institute for 

Occupational Safety and Health (NIOSH) 

received a management request for a health 

hazard evaluation (HHE) from the Kenton 

County Animal Shelter (KCAS) in Covington, 

Kentucky. The HHE request asked NIOSH to 

assess employee exposure to noise from barking 

dogs. On April 18 and 19, 2006, NIOSH 

investigators measured noise exposure levels for 

all animal shelter workers. NIOSH investigators 

returned to the facility on October 12, 2006, to 

conduct hearing tests for all animal shelter 

workers. 

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 the risk of hearing loss among police 

officers assigned to their 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. 

Kenton County Animal Shelter 

Founded in 1985, the KCAS serves 19 cities in 

Kenton County, Kentucky. The shelter receives 

approximately 500 cats and dogs a month. The 

animals are initially observed for diseases and 

temperament before being put up for adoption. 

There are six full-time employees at this facility. 

Additionally, inmates from the Kenton County 

Department of Corrections work at the facility as 

part of their community service. 

Visitors to the facility and animals being brought 

in are processed in the lobby. Across from the 

lobby is a room that holds animals for 

temperament observation. A short corridor from 

the main lobby leads to the dog kennel area with 

30 cages. Along the corridor that connects the 

main lobby and the dog kennels are two rooms. 

One is the kitchen area where the animal feeding 

and drinking bowls are washed; the other is a cat 

and puppy area. Next to the main facility is a 

small building where adoptions take place. 

Animals and their potential owners are given an 

opportunity to bond in this area before the 

adoption is finalized. 

Most employees work between 8:30 a.m. and 

6:00 p.m. The facility director and the inmates 

arrive between 6:30 and 7:00 a.m. The inmates 

begin cleaning dog cages and feeding dishes. 

They also clean the bathrooms and keep other 

parts of the facility clean. The inmates leave at 

3:00 p.m. while the director stays until closing. 

The employees perform a variety of tasks 

including laundering soiled cloths, feeding cats 

and dogs, cleaning cat and puppy cages, giving 

shots to animals, taking animals from the 

kennels to the adoption area and back, cleaning 

the facility, and staffing the front desk. Prior to 

inmates from the Kenton County Department of 

Corrections working at the kennels, KCAS 

employees cleaned dog cages as well. 

METHODS

Noise Assessment 

On April 18 and 19, 2006, nine animal shelter 

workers (six employees and three inmates) 
Page 2 Health Hazard Evaluation Report No. 2006-0212-3035 

contributed 18 full-shift, personal noise 

measures. Quest® Electronics (Oconomowoc, 

Wisconsin) Model Q-300 Noise Dosimeters 

were worn by the kennel workers while they 

performed their daily activities. The noise 

dosimeters were attached to the wearer’s belt 

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 workday, 

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 for 

Windows® computer software. The dosimeters 

were calibrated before and after the 

measurement periods according to the 

manufacturer’s instructions. 

Hearing Loss Assessment 

All KCAS workers were eligible for the hearing 

tests. Workers reported to an onsite NIOSH 

mobile test facility, prior to starting their shift. 

Informed consent was obtained from each 

participant before they completed a short 

questionnaire about work history. 

A Tremetrics (Eden Prairie, Minnesota) Model 

AR 901 Hearing Booth and OSCAR 7 ElectroAcoustic Ear and Octave Monitor (Eden Prairie, 

Minnesota) provided an appropriate acoustic 

environment for testing. The booth was located 

inside the mobile test facility. The area was 

controlled for conversations and other 

extraneous noises during the tests. Hearing tests 

were collected with a Tremetrics Model HT 

Wizard Audiometer that was calibrated 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 Hertz (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 result. 

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, 

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, noise-induced hearing loss 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 
Health Hazard Evaluation Report No. 2006-0212-3035 Page 3 

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 

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 
Page 4 Health Hazard Evaluation Report No. 2006-0212-3035 

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). Hearing threshold 

levels are plotted in reverse (the highest hearing 

level up to 0 or -10 dB). 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

One third of the personal noise dosimetry 

measures (6 of 18) exceeded the NIOSH daily 

allowable dose of 100% (Table 1). The full-shift 

TWA values for the NIOSH REL ranged from 

79 to 87 dBA. The TWA values for the OSHA 

criteria ranged from 63 to 82 dBA. Exposures 

were highest for the inmates who cleaned the 

dog kennels in the morning. Most of the fulltime employees had little direct contact with 

dogs; they rotated between cleaning cat cages, 

providing food to the animals, taking dogs to the 

adoption area, and staffing the lobby. Their 

exposures were lower than those of the inmates 

and lower than those measured at two other 

animal shelters.21,22 In addition, on the second 

day of the survey, the facility closed for a staff 

meeting for a few hours in the afternoon, further 

reducing employee contact with the dogs. 

Despite the limited contact with dogs, even short 

term exposure to barking dogs can vastly affect 

the full-shift noise exposures. An employee 

accumulated 20% dose (or one fifth the daily 

allowable dose) during a 10-minute period 

trying to get a dog back into its cage. The noise 

levels during this short period ranged from 88.4 

to 100.3 dBA. Noise exposures for the KCAS 

employees were higher towards the latter part of 

the day when they took over tasks in the dog 

kennels after the inmates left the shelter (Figure 

1). Job rotation among the full-time employees 

reduced their overall noise exposures. 

Hearing tests were given to 10 KCAS animal 

shelter workers (eight employees and two 

inmates). The median hearing test results and the 

inter-quartile range (a measure of variability) are 

shown in Figure 2. The data showed a high level 

of inter-individual variability. The mean age for 

the 10 workers was 37 years (range = 25–60 

years). They had worked at KCAS from 1 month 

to 20 years. 

Four of the 10 workers showed some hearing 

loss defined as exceeding the lower fence of 25 

dB HL. Five employees with normal hearing 

showed “notches” (frequency at which there is a 
Health Hazard Evaluation Report No. 2006-0212-3035 Page 5 

dip in the audiogram followed by an increase) at 

4000 Hz and 6000 Hz in one or both ears.

Notches occurring between 3000 to 6000 Hz 

may be indicative of the early stages of NIHL.

In addition, one employee with hearing loss had 

notches at 2000 Hz, 4000 Hz, and 6000 Hz. The 

notch at 2000 Hz is not consistent with NIHL. 

Table 2 shows the relationship between hearing 

test results and notch formation. 

This evaluation cannot establish an association 

between animal shelter workers with hearing 

loss and exposure to noise at the shelter 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 KCAS 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 these materials 

are difficult to clean. 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.23 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. Such approaches, 

however, does not eliminate the direct noise path 

from the dog to the worker. Hearing protectors, 

if worn properly all of the time, offer adequate 

protection. However, as far as possible, the 

preferred ways of controlling for noise are 

engineering controls, followed by administrative 

controls. Personal protective equipment such as 

hearing protectors should be considered after all 

feasible engineering and administrative controls 

are in place. 

A noise survey should be conducted after any 

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. 

CONCLUSIONS

This evaluation showed that workers at the 

KCAS are potentially exposed to hazardous 

noise levels particularly when working with 

dogs. Four of the animal shelter workers who 

participated in this evaluation showed some 

hearing loss greater than 25 dB HL. However, 

because of the small sample size, inability to 

control for confounders, and the relative youth 

of most of the employees with respect to time 

needed to develop hearing loss, it is not possible 

to say whether the observed hearing loss is 

related to noise exposure at the shelter. 

RECOMMENDATIONS

Based on the observations and findings of this 

evaluation, the following recommendations are 

offered to better protect the hearing of the 

animal shelter workers at KCAS: 

1. Establish a hearing loss prevention 

program for KCAS animal shelter 

workers. The basic elements of the 

program should, at a minimum, meet the 

requirements of the OSHA hearing 

conservation amendment (29 CFR 

1910.95).6

 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 

dog kennels. 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. 
Page 6 Health Hazard Evaluation Report No. 2006-0212-3035 

3. Place warning signs that identify loud 

noise areas on doors, and require 

employees entering these areas to wear 

hearing protectors. 

4. Consider using sound-absorbing 

materials that are not compromised by 

water and other cleaning solutions on 

ceilings and floors of dog kennels. 

Conduct noise exposure monitoring 

after controls are in place. 

5. Consult an acoustical engineer when 

considering any future design changes to 

the facilities to determine whether noise 

exposures can be reduced. 

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an environmental problem. J Am Vet Med 

Assoc 66 (11):1065-1068. 

2. Achutan C [anticipated 2007]. Occupational 

noise levels during emergency relief operations 

in the aftermath of Hurricane Katrina. Journal of 

Occupational and Environmental Hygiene 

(accepted). 

3. Reid A, Dick F, Semple S. [2004]. Dog noise 

as a risk factor for hearing loss among police 

dog handlers. Occup Med (London) 54 (8):535-

539. 

4. NIOSH [2006]. Hazard evaluation and 

technical assistance report: Cincinnati Police 

Canine Unit, Cincinnati, OH. Cincinnati, OH: 

U.S. Department of Health and Human Services, 

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2006-0223-3029. 

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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. 

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: normal and 

damaged hearing. Chapter 4. In: Berger EH, 

Royster LH, Royster JD, Driscoll DP, & Layne 

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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. 
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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. Use of the 

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

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Disease Control and Prevention, National 

Institute for Occupational Safety and Health, 

NIOSH HETA Report No. 2006-0222-3037. 

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24. NIOSH [1996]. Preventing occupational 

hearing loss — a practical guide. Cincinnati, 

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Page 8 Health Hazard Evaluation Report No. 2006-0212-3035 

TABLES

Table 1 

Full-Shift Personal Dosimetry Results for 18 Animal Shelter Workers at KCAS 

Job Responsibilities Number of 

Measures 

Percent Dose 

 OSHA AL OSHA PEL NIOSH REL 

*Clean dog cages, wash dishes, and 

clean bathrooms 

6 15.1 – 32.5 6.3 – 24.1 63.2 – 145.4 

**Laundry, clean cat and puppy cages, 

provide shots to animals, respond to the 

public, arrange adoptions 

12 4.2 – 29.3 2.3 – 18.2 24.9 – 171.2 

 * NIOSH REL exceeded five times 

 ** NIOSH REL exceeded once 

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

 maximum allowable daily dose 

 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 

 KCAS: Kenton County Animal Shelter

Table 2 

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

among KCAS Employees 

Employee ID Hearing Loss Notch (Hertz) 

 Left Ear Right Ear Left Ear Right Ear 

A Mild to Moderate Mild to Moderate No No 

B No No 6000 6000 

C No No 4000 4000 

D No Mild 2000, 4000 6000 

E Moderate Mild No No 

F Mild Mild No No 

G No No 6000 6000 

H No No No No 

I No No 6000 No 

J No No No 6000 

 KCAS: Kenton County Animal Shelter
Health Hazard Evaluation Report No.2006-0212-3035 Page 9 

FIGURES

Figure 1 

Comparison between Noise Exposures between KCAS Worker 

who Spends Most of the Time in Dog Kennels and KCAS Worker who has Job Rotation 

65

70

75

80

85

90

95

100

6:00 8:24 10:48 13:12 15:36 18:00

Time (hh:mm)

Noise Levels [dBA]

No Job Rotation Job Rotation

 KCAS: Kenton County Animal Shelter 
Page 10 Health Hazard Evaluation Report No. 2006-0212-3035 

Figure 2 

Median Levels and Inter-Quartile Ranges for Ten KCAS Employees 

0

2

4

6

8

10

12

14

16

18

20

012345678

Frequency [kHz]

Hearing Level [dB HL]

Right Ear Left Ear

KCAS: Kenton County Animal Shelter

Frequency (kHz) Left Ear Right Ear 

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

0.5 10 14 5 15 

1 5 15 5 10 

2 0 10 1 18 

3 0 10 0 15 

4 6 21 5 20 

6 11 25 10 25 

8 6 25 6 23 
DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Centers for Disease Control and Prevention National Institute for Occupational Safety and Health 4676 Columbia Parkway Cincinnati, OH 45226-1998 OFFICIAL BUSINESS Penalty for private use $300 

Delivering on the Nation's promise: Safety and Health at work for all people through 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: http://www.cdc.gov/niosh 

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