Evaluation of Employee Noise 

Exposures and Ergonomic Risks 

During Dental Procedures at a 

Veterinary Hospital

HHE Report No. 2018-0165-3374

June 2020 
Authors: Jessica F. Li, MSPH

George R. Grimes, MD, MPH

 Scott E. Brueck, MS, CIH, COHC

Jessica Ramsey, MS, CPE

Desktop Publisher: Shawna Watts

Editor: Cheryl Hamilton

Logistics: Donnie Booher, Kevin Moore

Medical Field Assistance: Jessica Rinsky

Keywords: North American Industry Classification System (NAICS) 541940 (Veterinary Services); 

Ergonomics, Noise, Hearing, Musculoskeletal, Veterinary Hospital, Veterinary Dentistry, Veterinary 

Dental Procedures, Arizona

Disclaimer

The Health Hazard Evaluation Program investigates possible health hazards in the workplace under 

the authority of the Occupational Safety and Health Act of 1970 [29 USC 669a(6)]. The Health 

Hazard Evaluation Program also provides, upon request, technical assistance to federal, state, and 

local agencies to investigate occupational health hazards and to prevent occupational disease or 

injury. Regulations guiding the Program can be found in Title 42, Code of Federal Regulations, 

Part 85; Requests for Health Hazard Evaluations [42 CFR Part 85]. 

Availability of Report

Copies of this report have been sent to the employer and employees. The state and local health 

departments and the Occupational Safety and Health Administration Regional Office have also 

received a copy. This report is not copyrighted and may be freely reproduced.

Recommended Citation

NIOSH [2020]. Evaluation of employee noise exposures and ergonomic risks during dental 

procedures at a veterinary hospital. By Li JF, Grimes GR, Brueck SE, Ramsey J. Cincinnati, OH: 

U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, 

National Institute for Occupational Safety and Health, Health Hazard Evaluation Report 

2018-1065-3374, https://www.cdc.gov/niosh/hhe/reports/pdfs/2018-0165-3374.pdf. 
Table of Contents

Main Report

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

Our Approach ................................................................................................................................................... 1

Our Key Findings.............................................................................................................................................. 2

Our Recommendations.................................................................................................................................... 3

Supporting Technical Information 

Section A: Workplace Information............................................................................................................ A-1

Employee Information ............................................................................................................................ A-1

History of Issue at Workplace................................................................................................................ A-1

Process Description ................................................................................................................................. A-2

Section B: Methods, Results, and Discussion .......................................................................................... B-1

Methods: Noise Exposure and Hearing Health................................................................................... B-1

Results: Noise Exposure and Hearing Health...................................................................................... B-2

Methods: Ergonomic Assessment and Musculoskeletal Health........................................................ B-5

Results: Ergonomic Assessment and Musculoskeletal Health........................................................... B-5

Methods: Other Health and Safety Issues............................................................................................ B-7

Results: Other Health and Safety Issues............................................................................................... B-7

Discussion ................................................................................................................................................. B-8

Limitations ............................................................................................................................................... B-12

Conclusions............................................................................................................................................. B-12

Section C: Tables.......................................................................................................................................... C-1

Section D: Occupational Exposure Limits............................................................................................... D-1

Noise ......................................................................................................................................................... D-2

Section E: References.................................................................................................................................. E-1
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1

Introduction

Request

Employees of a veterinary hospital requested a health hazard evaluation concerning noise exposures and 

ergonomic risks during dental cleanings and other dental procedures.

Workplace

Dental cleanings involved the following steps:

• Administering a sedative to calm the animal.

• Placing a breathing tube down the animal’s throat (intubating).

• Putting the animal to sleep (anesthetizing).

• Cleaning the animal’s teeth with an ultrasonic scaler.

• Polishing the animal’s teeth with a tooth polisher.

• Taking dental X-rays.

After X-rays were taken, the veterinarian determined if more dental procedures (e.g., tooth extraction) 

were needed. If so, the veterinarian performed these tasks with the veterinary technician’s assistance.

To learn more about the workplace, go to Section A in the Supporting Technical Information

Our Approach

We spent two days in the veterinary hospital in November 2018. We completed the following activities 

during our evaluation:

• Observed work processes, practices, and conditions.

• Measured employee exposures to noise during dental procedures.

• Observed ergonomic-related risk factors during dental procedures.

• Conducted confidential interviews about employee health.

To learn more about our methods, go to Section B in the Supporting Technical Information
2

Our Key Findings

Employee noise exposures during veterinary dental procedures were under the 

lowest occupational exposure limits

• Some employees used hearing protection that reduced noise at the ear more than needed.

• Employees who performed dental procedures were more likely to report ringing, roaring, or 

buzzing in their ears than employees who did not perform dental procedures.

• Few employees reported concerns of workplace noise and hearing loss.

• Some employees reported being concerned about loud noise in the kennel area.

Equipment design or placement required employees to use awkward postures 

during dental procedures

• Dental procedure tables were not height adjustable. Employees used awkward postures that 

could cause pain and discomfort in the neck, arms, and back.

• One procedure table’s design limited employees’ leg placement and movement when seated. 

• Employees were using awkward postures when accessing the laptop because of the laptop’s 

position on a cart. This could cause pain and discomfort in the neck, wrists, and back.

• Sharp table edges caused contact stress when employees leaned their arms against the edges.

• Employees did not use surgical loupes (i.e., eyeglasses with magnification) when performing 

dental procedures.

Some employees reported back pain, neck pain, hand or wrist discomfort, and 

upper extremity discomfort

• The proportion of employees reporting hand or wrist symptoms who performed dental 

procedures was 1.5 times greater than employees who did not perform dental procedures.

• Thirteen employees reported back pain. Of these, six (46%) said it was related to an activity at 

work. The most common activities associated with causing or contributing to back pain were 

repeated bending and repeated lifting of animals or equipment.

• Six employees reported neck pain. Of these, three (50%) stated that an activity at work 

contributed to the pain. All the employees who reported their neck pain being related to work 

performed dentistry, stating that repeatedly bending their necks contributed to their pain.

To learn more about our results, go to Section B in the Supporting Technical Information
3

Our Recommendations

The Occupational Safety and Health Act requires employers to provide a safe workplace.

Potential Benefits of Improving Workplace Health and Safety:

 Improved worker health and well-being  Enhanced image and reputation 

 Better workplace morale  Superior products, processes, and services

 Easier employee recruiting and retention  May increase overall cost savings

The recommendations below are based on the findings of our evaluation. For each recommendation, 

we list a series of actions you can take to address the issue at your workplace. The actions at the 

beginning of each list are preferable to the ones listed later. The list order is based on a well-accepted 

approach called the “hierarchy of controls.” The hierarchy of controls groups actions by their likely 

effectiveness in reducing or removing hazards. In most cases, the preferred approach is to eliminate 

hazardous materials or processes and install engineering controls to reduce exposure or shield 

employees. Until such controls are in place, or if they are not effective or practical, administrative 

measures and personal protective equipment might be needed. Read more about the hierarchy of 

controls at https://www.cdc.gov/niosh/topics/hierarchy/. 

We encourage the company to use a health and safety committee to discuss our 

recommendations and develop an action plan. Both employee representatives and 

management representatives should be included on the committee. Helpful guidance can be

found in Recommended Practices for Safety and Health Programs at

https://www.osha.gov/shpguidelines/index.html. 

Recommendation 1: Provide hearing protection appropriate for the noise levels in 

the workplace

Why? Properly worn hearing protection reduces employees’ noise exposure and risk of hearing loss. 

Over-protection occurs when employees use hearing protection that reduces noise at the ears more 

than is needed. When over-protected, employees may not be able to communicate effectively or hear 

warning signals and sounds (such as equipment noises) important to their work. One common sign 

that an employee is over-protected is removal of their hearing protection when communicating. 

Over-protection can also lead to less use or improper use of hearing protection.

How? At your workplace, we recommend these specific actions:

If providing earplugs for use during dental procedures, provide earplugs 

with a lower noise reduction rating.

• For employees conducting dental procedures in the procedure area, hearing protectors 

do not need to attenuate (reduce) noise levels by more than 15 decibels.
4

Train employees on proper use of hearing protection.

• More information on the proper use of soft foam earplugs may be found at 

https://www.cdc.gov/niosh/mining/content/earplug.html. 

Measure employees’ noise exposures in the kennel area to determine 

what hearing protection is required.

• Previous Health Hazard Evaluations have measured kennel employee noise exposures 

above occupational exposure limits and hearing loss among kennel employees: 

https://www.cdc.gov/niosh/hhe/reports/pdfs/2006-0212-3035.pdf and 

https://www.cdc.gov/niosh/hhe/reports/pdfs/2006-0196-3036.pdf. 

Recommendation 2: Provide equipment and workstations that are ergonomically 

designed to minimize musculoskeletal disorders in employees performing dental 

procedures

Why? Musculoskeletal disorders are conditions that involve the nerves, tendons, muscles, and 

supporting structures of the body. They can be characterized by chronic pain and limited mobility. 

A substantial body of data provides strong evidence of an association between musculoskeletal 

disorders and certain work-related factors (physical, work organizational, and psychosocial). The 

preferred method for preventing and controlling work-related musculoskeletal disorders is to design 

tasks, workstations, and tools and other equipment to match the physiological, anatomical, and 

psychological characteristics and capabilities of the employee.

How? At your workplace, we recommend these specific actions:

Provide procedure tables where the height can be adjusted.

• If fully adjustable tables are not feasible, set procedure tables at different heights for 

various sizes of employees or animals.

• Seated workstations are recommended if the job is visually demanding. 

• Seated hand-working heights should be adjustable 27′′–36′′ or fixed at 36′′.

• Seated workstation clearance should be greater than 18′′ for knee depth and greater than 

30′′ for knee width.

• Reaching distance for tools (from standing or sitting positions) should be less than 16′′. 

• Height-adjustable chairs with back support should be provided. Include a footrest, if 

needed.

• Rounded table edges are preferred to reduce contact stress with sharp table edges.
5

Provide mobile, adjustable medical computer carts.

• The top of the screen (display viewing height) when seated should be adjustable 35′′–46′′

or fixed at 46′′. 

• The top of the screen (display viewing height) when standing should be adjustable 

58′′–71′′ or fixed at 66′′. 

• The viewing distance (distance from screen) should be adjustable 18′′–30′′ or fixed 

at 23′′. 

• The standing hand-working heights should be adjustable 38′′–47′′ or fixed at 42′′. 

Provide surgical loupes to reduce neck flexion/forward tilt.

• Employees should be able to adjust the vertical angle of the loupes to reduce neck 

flexion.

Provide antifatigue mats near procedure tables.

• Mats should cover the entire area that employees move while performing their work 

task. 

• Mats should be greater than 0.5′′ thick and have an optimal compressibility of 3%–4%. 

• Mats should have beveled edges to minimize trip hazards. Place them at least 8′′ under a 

workstation to prevent uneven standing surfaces.

• Mats should be replaced when they appear worn out or are damaged.

Educate employees on musculoskeletal disorders and ergonomics.

• Include information about specific tasks that may cause or are likely to cause 

musculoskeletal disorders. 

• Teach employees how they can avoid musculoskeletal disorders (e.g., wrists should be 

kept in neutral postures, without straining, as much as possible to reduce the risk of 

musculoskeletal disorders).
6

Recommendation 3: Address other health and safety issues we identified during 

our evaluation

Why? A workplace can have multiple health hazards that cause worker illness or injury. These hazards 

can potentially cause serious health symptoms, lower morale and quality of life for your employees, 

and increase costs to your business. Although not the primary focus of our evaluation, we saw the 

following potential hazards:

• Work practices that are not in compliance with bloodborne pathogen exposure prevention

• X-rays taken in a shared space

• Trip hazards in the procedure area

• Placement of autoclave and vending machine

• Improper chemotherapy drug storage

• Latex gloves

How? At your workplace, we recommend these specific actions:

Follow the Occupational Safety and Health Administration’s bloodborne 

pathogens standard.

• Provide initial and annual bloodborne pathogens training to employees who encounter 

animal body fluids.

• Use gloves and other appropriate personal protective equipment when body fluids are 

present.

• Do not recap used needles.

• To best protect employees, the American Veterinary Medical Association recommends 

voluntary compliance with this standard. More information on the bloodborne 

pathogens standard may be found at 

https://www.osha.gov/SLTC/bloodbornepathogens/ and 

https://www.cdc.gov/niosh/topics/bbp/genres.html. 

Avoid taking X-rays outside of a radiology or imaging room.

• Ensure all other employees leave the room every time an X-ray is taken if outside of a 

radiology or imaging room.

• Do not take more than the minimum number of X-rays necessary for diagnosis.

• Conduct baseline radiation monitoring to determine if additional radiation monitoring is 

required. More information on personal radiation monitoring can be found at 

https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1096. 

• Educate employees annually on radiation safety.
7

Remove any slip, trip, and fall hazards from the floor.

• Unplug and put away equipment and power cords that are not in use.

• Install overhead electrical outlets or retractable cords.

• Find more information on slip, trip, and fall hazards in healthcare settings in the 

National Institute for Occupational Safety and Health (NIOSH) publication Slip, Trip 

and Fall Prevention for Healthcare Workers. 

Move the vending machine away from the autoclave to reduce the 

potential for contamination.

Properly label chemotherapy drugs and store them in a room that is not 

used for storing other items or doing other work.

• More information on occupational hazards associated with these drugs can be found in 

the NIOSH Alert: Preventing Occupational Exposures to Antineoplastic and Other 

Hazardous Drugs in Health Care Settings. 

Do not use latex gloves in the veterinary hospital to prevent possible 

allergic reactions.

• Remove latex gloves from the facility.

• Continue providing powder-free nitrile gloves to employees.

• More information on occupational hazards associated with latex exposure can be found 

in the NIOSH Alert: Preventing Allergic Reactions to Natural Rubber Latex in the 

Workplace. 
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Supporting Technical Information

Evaluation of Employee Noise Exposures and 

Ergonomic Risks During Dental Procedures at a 

Veterinary Hospital

HHE Report No. 2018-0165-3374

June 2020
A-1

Section A: Workplace Information

Employee Information

• Total employees: 67

• Number of employees working at time of evaluation: 36

• Length of shift: approximately 8 hours

• Median age: 29 years (range: 21–63 years)

• Median job tenure: 2.6 years (range: < 1–30 years)

• Median time in veterinary duties: 5 years (range: < 1–38 years)

• Sex: 83% female

• Job titles: veterinarians (10), veterinary technicians (21), and assistants (5) 

o Because of the similarity in tasks, in this report, “veterinary technicians” refers to the job 

titles of veterinary nurses, veterinary technicians, and certified veterinary technicians.

Employees Performing Dental Procedures

• Number of employees performing dental procedures: 19 (53%)

• Median tenure conducting dental procedures: 6 years (range: < 1–38 years)

• Median time per week conducting dental procedures: 4 hours (range: 1–16 hours)

Veterinarians primarily used electric dental drills, nonpowered hand tools, and pressurized water during 

dental procedures, while veterinary technicians used ultrasonic scalers, polishers, and nonpowered 

hand tools. Dental procedures typically lasted 30 to 90 minutes, with up to five procedures completed 

per day.

History of Issue at Workplace

Employees reported concerns to us about possible hearing loss from using noise-generating dental 

equipment including electric dental drills and ultrasonic scalers. Employees reported a recent increase in 

the use of dental radiographs (X-rays) to identify dental disease in small animal veterinary medicine. 

This led to concerns over an increased amount of dental procedures with the increased amount of 

associated noise exposure. The employee requestors also expressed concerns about ergonomic stressors 

while performing dental procedures when we spoke to them prior to the evaluation.
A-2

Process Description

Dental Cleaning

Veterinary technicians sedated and intubated the animal on a procedure table. The animal was then 

anesthetized. A veterinary technician cleaned the animal’s teeth on one side using a hand scaler and an 

ultrasonic scaler and inspected teeth for potential problems. After the teeth were cleaned, the veterinary 

technician polished the teeth with an electric tooth polisher. An air-water syringe (sprayer) was also used 

throughout the cleaning to wash out the animal’s mouth. With the help of another veterinary technician, 

the animal was turned to the other side, and the cleaning and polishing process was repeated for the 

second side.

Radiography 

Following the dental cleaning, the veterinary technicians took dental radiographs of noted problem 

areas to determine if the animal’s teeth required further treatment by the veterinarian.

Additional Dental Procedures 

When needed, the veterinarian extracted teeth. The veterinarian injected a local anesthetic and used an 

electric dental drill to loosen or break teeth to aid in tooth extraction. The length of drilling depended 

on the number of teeth requiring extraction and the size, location, and difficulty of the tooth 

extraction(s).
B-1

Section B: Methods, Results, and Discussion

Our evaluation had the following objectives:

• Assess employee noise exposures.

• Evaluate noise levels and noise frequency characteristics of dental instruments (e.g., ultrasonic 

scaler, polisher, drill).

• Determine the prevalence of employee symptoms related to work-related noise exposures.

• Determine the potential for musculoskeletal disorders among employees.

• Determine the prevalence of employee symptoms related to work-related ergonomic stressors.

Methods: Noise Exposure and Hearing Health

We evaluated employees’ noise exposures through (1) full-shift noise dosimetry measurements, 

(2) measuring area sound levels during dental procedures, and (3) observations.

We collected full-shift time-weighted average (TWA) personal noise samples:

• We collected samples from 10 employees over two days.

• We took the samples in the dental procedure area.

• We used Larson Davis SparkTM 706 RC integrating noise dosimeters.

• We placed the dosimeter microphone on the top of the employee’s shoulder at the midpoint 

between the neck and edge of the shoulder. For veterinary technicians and veterinarians, we 

placed one dosimeter microphone on each side of the employee’s shoulder to compare right and 

left ear noise exposures.

• We took noise dosimetry measurements using three different settings to compare with the 

National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit 

(REL), the Occupational Safety and Health Administration (OSHA) permissible exposure limit 

(PEL), and the OSHA action level (AL). 

We also collected instantaneous area sound levels:

• We took the samples in the dental procedure area.

• We used a Larson Davis Model 824 integrating sound level meter.

• We measured one-third octave band noise frequency levels (i.e., measurement of noise levels 

across 30 different frequencies).

• We positioned the instrument at a height of approximately 5 feet above the floor and within 

3–6 feet of the employees or the primary noise source in the area.
B-2

Hearing Health

We interviewed employees and asked about workplace noise, hearing protection, and hearing health. We 

asked them questions about hearing loss derived from the Philadelphia Hearing Scale Study [Schein et 

al. 1970]. We also asked employees if they had tinnitus by inquiring if they had ringing, roaring, or 

buzzing in their ears for five minutes or more. If employees responded yes, they were asked the 

frequency (every day, every week, every month, or less than one time per month) and if this started after 

initiating work at the facility.

We asked employees if they wore hearing protection while at work. If employees reported using hearing 

protection, we asked during which tasks they wore hearing protection and when hearing protection use 

was initiated (month and year).

Results: Noise Exposure and Hearing Health

Personal Noise Exposures

A summary of personal noise dosimetry results collected on 10 employees over two work shifts is in 

Table C1. We compared employees’ noise monitoring results with the noise exposure limits set by 

NIOSH and OSHA. These occupational noise exposure limits are meant to be the amount of noise that 

most employees can be exposed to without substantial risk of hearing loss. OSHA and NIOSH measure 

and calculate noise exposures in different ways, as described in Section D. For an 8-hour work shift, the 

NIOSH REL is 85 decibels, A-weighted (dBA). The OSHA AL is 85 dBA, and the OSHA PEL is 

90 dBA. Employers are required to keep noise exposures below the OSHA PEL; however, the NIOSH 

REL is more protective. 

Results showed that employees in all job titles we monitored had full-shift TWA noise exposures below 

the NIOSH REL. We found minimal differences between the measurement results taken near an 

employee’s right and left ears. All employees we observed performing dental procedures were 

right-handed.

We observed five dental cleanings on Day 1 and three dental cleanings on Day 2. All dental cleanings 

were performed on dogs. Following dental cleanings and X-rays, a drill was used for tooth extraction(s) 

on one dog on Day 1 and on three dogs on Day 2. Dental cleanings and procedures sometimes 

occurred at the same time on tables located approximately 5 feet from one another. The veterinary 

technicians and veterinarians performing cleanings and procedures were different on both days.

Noise from Dental Instruments

During dental cleanings, veterinary technicians typically held dental instruments 2 feet or less from their 

ears. The maximum instantaneous area sound levels we collected while employees used the ultrasonic 

scaler was 78 dBA; while they used the tooth polisher, it was 73 dBA.

Employees expressed concerns about the high frequency nature of the noise generated by the ultrasonic 

scaler. We used one-third octave band sound level measurements to identify the dominant frequencies 

of the noise generated during the use of dental instruments. One-third octave band sound level 

measurements taken during ultrasonic scaler use revealed that the highest sound levels were generally at 

frequencies above 3,150 Hertz (Hz), with dominant frequencies of 4,000 Hz; 8,000 Hz; and 16,000 Hz 
B-3

(Figure B1). There was a peak in the lower frequencies of 16 Hz and 20 Hz identified for the 66.4 dBA 

measurement; this peak is likely not associated with the ultrasonic scaler.

Figure B1. One-third octave band frequencies for the ultrasonic scaler. The dominant frequencies for 

both measurements were 4,000 Hz; 8,000 Hz; and 16,000 Hz. The 66.4 dBA measurement also had a 

dominant frequency at 16 Hz and 20 Hz. The sources of the noise at these frequencies is unknown and 

could be from other instruments or equipment in the vet hospital. 

During tooth extractions, veterinarians typically held the drill about 2 feet or less from their ears. Drill 

use was typically intermittent and shorter in duration than dental cleaning instrument use. The 

maximum instantaneous area sound level during drill use was 80 dBA. Employees also expressed 

concerns about the high frequency nature of the noise generated by the drill. One-third octave band 

sound level measurements taken during drill use revealed that the highest sound levels were generally at 

frequencies above 5,000 Hz (Figure B2).
B-4

Figure B2. One-third octave band frequencies during drill use. The dominant frequencies for drill use 

were above 5,000 Hz.

Hearing Health

Out of 36 employees, 32 (89%) reported good hearing in at least one ear, 30 (83%) reported good 

hearing in both ears, and 6 (17%) reported they had a little or a lot of trouble hearing in one or 

both ears.

Out of 36 employees, 8 (22%) reported they had ringing, roaring, or buzzing (tinnitus) in their ears that 

lasted 5 minutes or more. All eight employees performed dental procedures. Four of these employees 

noted that this occurred every day, while the other four employees reported that it occurred one time 

per month or less. Employees who performed dental procedures self-reported tinnitus in higher 

proportion than those employees who did not perform dental procedures (prevalence ratio 1.73; 

confidence interval 1.18–2.53). However, of these eight employees, only three (38%) mentioned that the 

ringing, roaring, or buzzing started after working at this facility. We did not ask about nonoccupational 

sources that could cause tinnitus, or if employees perceived their tinnitus to have worsened since 

starting work at this facility.

Personal Protective Equipment Use

The veterinary hospital provided foam insert ear plugs (labeled noise reduction rating of 32 decibels 

[dB]) to their employees. We observed most employees wore hearing protection while conducting 

dental procedures. We observed that the ear plugs were not fully inserted when used. 

Out of 36 employees, 19 (53%) reported wearing hearing protection while at work. The most common 

task during which employees reported wearing hearing protection was performing kennel work (12 of 
B-5

19 employees; 63%). These employees reported infrequently entering the kennel but reported wearing 

ear plugs when they did.

Of the 19 employees that reported wearing hearing protection while at work, 10 (53%) employees did 

so while conducting dental procedures. Three or fewer employees wore ear plugs when operating the 

compressor or performing other tasks. One veterinary technician noted difficulty hearing monitoring 

instruments when wearing hearing protection. 

Methods: Ergonomic Assessment and Musculoskeletal Health 

We observed workplace conditions and work practices to identify ergonomic risk factors. We measured 

workstation heights and tool dimensions and noted the availability of antifatigue mats and other 

personal protective equipment (PPE). We asked employees if they had hand or wrist, arm or shoulder, 

or neck or back issues over the past 12 months that could be caused by ergonomic stressors. If 

employees reported that they had these symptoms, we asked if their symptoms were related to an 

activity at work. If employees reported that it was related to an activity, we asked about specific work 

tasks performed during veterinary dental procedures and offered an open-ended response. If employees 

related symptoms to an accident, we asked them to provide an open-ended response of the nature of 

the accident. For employees who reported back pain, we asked them to specify if it was upper back 

pain, lower back pain, or both.

Results: Ergonomic Assessment and Musculoskeletal Health 

Ergonomic Assessment

We evaluated two tables where dental procedures were performed. 

Neither table could be adjusted and were at fixed heights of 38′′ 

and 39′′. One table had a curved front that allowed leg access when 

seated (Figure B3). However, taller employees did not have much 

leg access under the curved table. This limited their ability to place 

their legs under the table and led to farther reach distances. The 

other table had a sink basin and legs that restricted the employee’s 

leg placement when seated (Figure B4). When we observed 

employees using this table, we saw them working from the corner, 

standing to the side and bending at the back, or straddling this table 

to use it. Because of the way the procedure tables were designed, 

we observed that employees were not able to sit all the way back in 

the chair or use the back rest on the chair. Additionally, the tables 

had edges that could cause contact stress when forearms or wrists 

were resting on the table. 

Figure B3. Fixed-height table for 

dental procedures with curved 

front allowing leg access while 

employees are seated. Photo by 

NIOSH.
B-6

We also observed employees performing dental 

procedures bending at the neck when seated or 

bending at the back when standing to optimize 

their visual fields during procedures. The lack of 

adjustability of the tables contributed to 

employees having to bend at the neck or back. 

We did not observe employees performing dental 

procedures using magnification devices, such as 

surgical loupes.

Employees used various precision tools for dental 

procedures. The tools were approximately 3′′–4′′ 

long and 0.25′′–1′′ in diameter. Some tools were 

spring-loaded to return to an open position. For 

sterilization purposes, all the tools were metal. 

Most were contoured and had etched surfaces for 

improved grip.

The employees accessed information on a laptop placed on a rolling cart. The cart height was not 

adjustable, so when standing, the employee had to bend at the back to see the screen or to type. The 

floor was ceramic tile. No antifatigue mats were available for use on the floor around the dental 

procedure tables.

Musculoskeletal Health

Some employees reported work contributed to back pain

Of the 36 employees working during our evaluation, 13 (36%) reported back pain that lasted for one 

week or more in the past 12 months. Of these, 5 (38%) were veterinarians and 8 (62%) were veterinary 

technicians. Of these 13 employees reporting back pain, 6 (46%) performed dental procedures, and 

6 (46%) said their back pain was related to an activity at work. The most common work activities these 

employees reported were repeated bending (4 of 6, 67%) and repeated lifting of animals or equipment 

(4 of 6, 67%). Two or fewer employees reported that their back pain was related to repeated twisting or 

sitting for extended periods of time, awkward postures when handling animals, pushing or pulling of 

animals or equipment, or an accident at work. We did not note any difference in back pain reporting in 

employees performing dental procedures compared to employees who did not perform dental 

procedures.

Some employees reported work contributed to neck pain 

Of the 36 employees working during our evaluation, 6 (17%) reported neck pain, with 3 (50%) of those 

6 reporting that an activity at work contributed to the pain. Three employees reporting neck pain were 

veterinarians and three were veterinary technicians. All employees who reported that neck pain was 

associated with their work performed dental procedures and engaged in repeated bending of the neck, 

which contributed to this pain. We did not note any difference in neck pain reporting in employees 

performing dental procedures compared to employees who did not perform dental procedures.

Figure B4. Fixed-height table with sink basin under 

the top of the table. The table design does not 

allow employees to place legs under this table while 

performing dental procedures. Photo by NIOSH.
B-7

Some employees reported that work contributed to upper extremity symptoms 

We asked employees about hand and wrist symptoms that may be associated with ergonomic stressors. 

Of the 36 employees evaluated, 8 (22%) reported experiencing one or more symptoms in the past 

12 months. Of these 8 employees, 7 (88%) performing dental procedures reported hand and wrist 

symptoms. Employees performing dental procedures reported hand and wrist symptoms more 

commonly than employees who did not perform dental procedures (prevalence ratio 1.5; confidence 

interval 1.03–2.41). However, only half (50%) of the employees reporting hand and wrist symptoms 

noted that work made their symptoms worse. We did not ask about preexisting medical conditions or 

nonoccupational sources that could cause hand or wrist discomfort.

Of the 36 employees working during our evaluation, 7 (19%) reported shoulder or arm pain every day 

for a week or more in the past 12 months. We did not note any difference in shoulder or arm pain 

reporting in employees performing dental procedures compared to employees who did not perform

dental procedures. Two or fewer employees reported that their pain was related to an activity or 

accident at work.

Methods: Other Health and Safety Issues

We collected information about other health and safety issues at the veterinary hospital through 

(1) observations of workplace conditions and practices and (2) review of the OSHA 300 Log of WorkRelated Injuries and Illnesses for January 1, 2015, through December 31, 2017.

Results: Other Health and Safety Issues

We observed dental X-rays taken outside of a radiation room and in the dental procedure area. The 

dental procedure area was a crowded open area where employees worked while the X-rays were taken. 

Verbal warnings were given a few seconds prior to the taking of the X-ray. We observed that sometimes

X-rays of the same area of the animal’s mouth were taken multiple times. We observed that some 

employees wore radiation dosimeters.

We observed multiple trip hazards, including monitor carts and power cords for equipment and 

electronics not in use, laying across the floor in the dental procedure area. These trip hazards were 

worsened by and contributed to the crowded conditions in the area.

We observed several nonideal placements and positionings of equipment, likely the result of limited 

space within the veterinary hospital. The vending machine and the autoclave machine sat side-by-side in 

the same room (Figure B5). Chemotherapy drugs were stored in a small labeled refrigerator in a room 

that also served as a storage area for other items (Figure B6).
B-8

We observed that employees were not following standard bloodborne pathogen protocols, which are 

required in human medicine facilities. Specifically, we observed employees recapping used needles, 

handling bloody materials without gloves, and using glasses without splash protection (i.e., splash 

shields). Bloodborne pathogens training was not provided to employees; this training is not required by 

OSHA in animal care facilities.

The veterinary hospital had a box of latex gloves for use by employees; we did not observe any

employees using latex gloves.

The OSHA 300 Log contained five injuries in 2015, four injuries in 2016, and one injury in 2017. All 

injuries were dog or cat bites.

Discussion 

Dental radiographs are routinely recommended, even for dental prophylaxis procedures [Hale 2013; 

Holmstrom et al. 2004]. The American Animal Hospital Association guidelines recommend performing 

a complete examination in all dogs and cats that have been anesthetized, which includes radiographic 

examination [Holmstrom et al. 2004]. Radiography can identify early dental disease, which can 

subsequently result in more frequent scheduling of dental procedures and surgeries for veterinarians and 

veterinary technicians [Holmstrom et al. 2004]. During these procedures, high-speed dental equipment 

is routinely used and may result in more frequent exposure to noise and more frequent use of dental 

equipment [Koch 2018].

Hearing loss and tinnitus are common conditions in the United States [Masterson et al. 2016]. Research 

has shown that dental professionals may have higher levels of noise-induced hearing loss (NIHL) and 

tinnitus than other job series [Burk and Neitzel 2016; Gonçalves et al. 2015; Messano and Petti 2012; 

Myers et al. 2016; Willershausen et al. 2014]. However, exposure assessments of noise in dental 

environments have shown variable results, with some studies finding levels of noise above occupational 

Figure B6. Vending machine and autoclave 

machine next to each other in the same 

room. Photo by NIOSH.

Figure B5. Chemotherapy drug refrigerator 

in a room used to store other items. Photo 

by NIOSH.
B-9

exposure limits (OELs), while others have measured levels below applicable OELs [Burk and Neitzel 

2016; Choosong et al. 2011; Jadid et al. 2011; Setcos and Mahyuddin 1998]. Although there are studies 

evaluating noise exposures and health effects in the human dental environment, little has been 

published regarding noise exposures and health effects in the animal dental environment.

We found that noise from the ultrasonic scaler and drill were higher in frequency in nature, but these 

dental tools produced a relatively low level of noise. Our evaluation found that veterinarians and 

veterinary technicians at this facility did not have noise exposures above OELs. Our noise measurement 

results were consistent with our assessment of hearing loss outcomes, which revealed that employees 

infrequently reported hearing loss. Employees who performed dental work were more likely to report 

tinnitus compared to those who did not perform dental work. However, we did not ask about 

nonoccupational exposures or use of medications that could cause or contribute to tinnitus, or if the 

tinnitus worsened since initiating work at this facility. We did not measure noise exposures or noise 

sources during dental procedures or in the procedure room that would be likely to lead to hearing loss. 

However, several employees were concerned about noise levels in the kennel area, and previous 

research has shown high noise levels in kennels that could contribute to noise exposures and the 

potential for effects on hearing.

While veterinarians and veterinary technicians did not experience noise exposures above OELs, 

employees reported concerns about noise levels in the kennel area and when retrieving dogs in the 

boarding rooms. Previous research has shown that noise levels in kennels may reach levels that exceed 

the OSHA PEL of 90 dBA or the NIOSH REL of 85 dBA [NIOSH 2007a,b,c,d]. Although not 

included within the scope of this evaluation, it would be prudent to perform a noise exposure 

assessment of the kennel space to determine the extent of noise levels and if preventive measures 

should be undertaken to reduce the risk of negative hearing health outcomes. 

Despite low levels of noise, some employees used high-attenuation (high-reduction) hearing protection 

(labeled noise reduction rating of 32 dB) during dental procedures. This high level of attenuation 

(reduction) could result in overprotection, or more attenuation of noise than is needed based on the 

measured noise levels. Overprotection may interrupt communication among staff and prevent 

employees from hearing monitoring equipment (e.g., heart rate monitors) or their surroundings. One of 

the veterinary technicians noted difficulty hearing monitoring instruments when wearing hearing 

protection. We observed employees not fully inserting hearing protection into the ear canal. This could 

be a result of incomplete training on the use of hearing protection or a sign of too much hearing 

protection. If employees have too much hearing protection, provide them with hearing protectors that 

only attenuate noise levels to below hazardous levels at the ear. For employees conducting dental 

procedures in the procedure area, this would mean that hearing protectors should not attenuate noise 

levels by more than 15 dB. Flat attenuation earplugs, which reduce sound equally across all frequencies 

and maintain the clarity of music and speech, may be a good choice for these employees. Higher 

attenuation would be needed in the kennel area.

We observed employees working in awkward postures, using forceful exertions, and performing 

repetitive motions during dental procedures. These activities can lead to musculoskeletal disorders, 

which can be characterized by chronic pain and limited mobility. Evidence shows that job tasks 
B-10

requiring a combination of risk factors (highly repetitious, forceful hand or wrist exertions) increase risk 

for hand or wrist tendonitis [NIOSH 1997a]. Additionally, low back disorders are associated with workrelated lifting, forceful movements, and awkward postures such as bending and twisting [NIOSH 

1997a]. Although personal factors such as age, sex, smoking, physical activity, strength, and body 

measurements may affect an individual’s susceptibility to overexertion injuries/disorders, studies 

conducted in high-risk industries show that the risk associated with these personal factors is smaller 

than the risk associated with their occupational exposures [NIOSH 1997a]. Many of our 

recommendations are adapted from principles outlined in The Handbook of Ergonomic Design Guidelines

[Humantech 2009].

Numerous studies have shown that dental professionals (in human dentistry) may be exposed to 

ergonomic stressors and may experience neck pain, upper extremity disorders, and back pain [Aminian 

et al. 2012; De Sio et al. 2018; Gupta et al. 2013; Occhionero et al. 2014; Sakzewski and Naser-ud-Din 

2014]. A review paper authored by De Sio et al. [2018] identified that extreme forward head tilt was the 

most frequently observed incorrect posture in dental professionals. Additional research has shown that 

veterinary practitioners have ergonomic stressors associated with musculoskeletal pain [Randall et al. 

2012; White 2012]. 

Research on stressors and outcomes related specifically to veterinary dentistry is limited. One study by 

Kozak et al. [2014] concluded that veterinarians who frequently perform dental work had greater odds 

of developing musculoskeletal disorders in the neck than veterinarians who did not perform dental 

work. This association was noted for veterinarians who performed 600 or more dental procedures per 

year [Kozak et al. 2014]. Another study by Scuffham et al. [2010] found a significant difference in 

musculoskeletal discomfort for veterinarians performing over 600 dental procedures per year than 

veterinarians performing fewer than 600 dental procedures. We observed employees using forceful 

exertions and repetitive motions of the hands during veterinary dental procedures. The tools being used 

met the recommended guidelines. Specifically, they were oval or circular with the appropriate handle 

length, diameter, and nonslip surface. However, due to the procedure table design and chair use, the 

employees used awkward wrist postures to complete the dental tasks. Furthermore, employees 

performing dental procedures had a higher prevalence of self-reported hand and wrist symptoms than 

employees who did not perform dental procedures. 

We observed that employees had static and repeated forward flexion (bending) of the neck during 

dental procedures. This may be because of the small visual window during procedures, requiring 

veterinarians and veterinary technicians to get a “closer look” during dental procedures or surgery. 

None of the employees we observed performing dental procedures used surgical loupes. Properly 

selected and positioned magnification systems, such as surgical loupes, can help reduce forward neck 

flexion; loupes that are vertically adjustable allow for employees to adjust the declination angle to reduce 

their need to bend at the neck or back. Employees may use magnification over safety glasses to reduce 

the frequency of forward flexion of the neck, and the development of neck pain [Holmstrom et al. 

2004].

The American Veterinary Medical Association recommends voluntarily complying with the OSHA 

Bloodborne Pathogen standard [29 CFR 1910.1030] with regards to medical waste, or any waste that 
B-11

contains potentially infectious material [National Association of State Public Health Veterinarians 2010]. 

The OSHA Bloodborne Pathogen standard generally applies only to occupational exposures to human 

blood (or animal blood used in research that is known to be infected with human immunodeficiency 

virus or hepatitis B virus) [29 CFR 1910.1030]. In human medicine, controlling bloodborne pathogen 

risks is crucial to preventing the spread of infectious disease. In veterinary medicine, these risks are not 

as widely recognized or controlled. 

A survey using questionnaires conducted in 2005 revealed that most veterinarians in the United States 

did not engage in the proper work practices or use appropriate PPE to help reduce zoonotic disease 

transmission [Wright et al. 2008]. However, the risk of emerging zoonotic diseases increases the need 

for effective infection control practices and policies. These infection control practices may include 

disposing of used sharps in appropriately labeled sharps containers and wearing gloves and other 

appropriate PPE (e.g., apron, respiratory protection, eye protection) during procedures and when 

handling materials contaminated by animal body fluid. Limited space in the animal hospital resulted in 

the problematic placement of the autoclave next to a vending machine. This is not ideal because 

instruments entering the autoclave may be contaminated with animal body fluids, which could result in 

potential contamination of the vending machine or its contents once dispensed.

We observed X-rays being taken in the treatment room while multiple staff continued with animal care 

duties. In most cases, it is best if the veterinary diagnostic X-ray machine is installed in a separate room 

or isolated area where employees are protected from potential radiation exposure, and where operations 

of the practice will not be disrupted [Seibert 2003]. Having the machine installed in an open 

environment may be acceptable, if the room can adequately be cleared of all staff prior to taking X-rays 

[Seibert 2003]. 

Because of limited space, the chemotherapy drugs were stored in a small refrigerator in an openly 

accessible room also used for storage. Chemotherapy and other hazardous drug exposure may result in 

adverse health effects including skin rashes, infertility, miscarriage, birth defects, and possibly cancer, 

and workers may be exposed throughout the life cycle of these drugs from manufacture to disposal 

[NIOSH 2004]. Chemotherapy drugs should be stored separately from other drugs or equipment in an 

area with sufficient general exhaust ventilation, ideally at negative pressure, and near where they will be 

used or compounded [NIOSH 2004; USP 2019]. Access to this storage area should be limited to 

authorized personnel.

Crowding in the animal hospital also led to the placement of equipment and loose cords and cables on 

the floor in the dental procedures area that could potentially lead to a slip, trip, or fall. Equipment and 

cords can become caught on an employee’s foot and lead to a fall incident. Information on slip, trip, 

and fall hazards common in healthcare settings and ways to prevent them can be found in the NIOSH 

publication Slip, Trip, and Fall Prevention for Healthcare Workers [NIOSH 2010].

The veterinary hospital provided latex gloves, along with nitrile gloves, for employees to use. Latex 

glove use may cause skin irritation or skin allergy in some employees. Information on the occupational 

hazards associated with latex exposure can be found in the NIOSH Alert: Preventing Allergic Reactions 

to Natural Rubber Latex in the Workplace [NIOSH 1997b].
B-12

Limitations 

Limitations of our evaluation include the cross-sectional design of the evaluation. Cross-sectional 

studies collect information on exposures and health outcomes at the same time, so causality cannot be 

proven. Industrial hygiene sampling can only document exposures on the days of sampling in the 

locations sampled. For hearing health, we did not ask about nonoccupational exposures that could 

contribute to outcomes.

Conclusions

Although few employees complained of noise exposure during dental procedures, some were concerned 

with noise in the kennel. Employee noise exposures measured during this evaluation were under the 

lowest occupational exposure limits. We observed employees using awkward positions during dental

procedures, along with several other potential workplace hazards that were not part of our initial 

evaluation. We recommended employees wear hearing protection appropriate for the workplace that 

will not interfere with communication or job tasks. We also recommended ergonomic workstations and 

solutions for other observed workplace hazards. 
C-1

Section C: Tables

Table C1. TWA personal noise exposure results (dBA)

Day Job title Side Result using 

NIOSH REL 

criteria

Result using 

OSHA AL 

criteria

Result using 

OSHA PEL 

criteria

1 Veterinarian 1 Right* 77.8 71.9 59.3

 Left 77.5 71.5 58.4

 Certified veterinary technician Right* 76.4 69.1 57.6

 Left 77.1 70.9 57.9

 Veterinary nurse 1 Right* 76.4 69.9 53.4

 Left 70.5 60.4 42.7

 Veterinary technician Right* 70.9 60.9 43.9

 Left 63.1 46.3 38.0

 Technician assistant 1 Right 69.7 57.2 49.3

 Technician assistant 2 Right 67.7 54.2 44.1

2 Veterinarian 2 Right* 81.5 76.4 68.3

 Left 77.6 71.0 60.3

 Veterinary nurse 2 Right* 73.4 64.9 51.6

 Left 76.6 68.2 57.2

 Technician assistant 3 Right 74.7 66.5 54.7

 Veterinary nurse 3 Right* 65.3 53.1 26.3

 Left 61.9 46.9 26.9

Noise exposure limits (8-hour work shift) 85 85 90

*Dominant hand
D-1

Section D: Occupational Exposure Limits

NIOSH investigators refer to mandatory (legally enforceable) and recommended OELs for chemical, 

physical, and biological agents when evaluating workplace hazards. OELs have been developed by 

federal agencies and safety and health organizations to prevent adverse health effects from workplace 

exposures. Generally, OELs suggest levels of exposure that most employees may be exposed to for up 

to 10 hours per day, 40 hours per week, for a working lifetime, without experiencing adverse health 

effects. 

However, not all employees will be protected if their exposures are maintained below these levels. Some 

may have adverse health effects because of individual susceptibility, a preexisting medical condition, or 

a hypersensitivity (allergy). In addition, some hazardous substances act in combination with other 

exposures, with the general environment, or with medications or personal habits of the employee to 

produce adverse health effects. Most OELs address airborne exposures, but some substances can be 

absorbed directly through the skin and mucous membranes.

Most OELs are expressed as a TWA exposure. A TWA refers to the average exposure during a normal 

8- to 10-hour workday. Some chemical substances and physical agents have recommended short-term 

exposure limits (STEL) or ceiling values. Unless otherwise noted, the STEL is a 15-minute TWA 

exposure. It should not be exceeded at any time during a workday. The ceiling limit should not be 

exceeded at any time.

In the United States, OELs have been established by federal agencies, professional organizations, state 

and local governments, and other entities. Some OELs are legally enforceable limits; others are 

recommendations. 

• OSHA, an agency of the U.S. Department of Labor, publishes permissible exposure limits 

[29 CFR 1910 for general industry; 29 CFR 1926 for construction industry; and 29 CFR 1917 

for maritime industry] called PELs. These legal limits are enforceable in workplaces covered 

under the Occupational Safety and Health Act of 1970. 

• NIOSH RELs are recommendations based on a critical review of the scientific and technical 

information and the adequacy of methods to identify and control the hazard. NIOSH RELs are 

published in the NIOSH Pocket Guide to Chemical Hazards [NIOSH 2007e]. NIOSH also 

recommends risk management practices (e.g., engineering controls, safe work practices, 

employee education/training, PPE, and exposure and medical monitoring) to minimize the risk 

of exposure and adverse health effects.

• Another set of OELs commonly used and cited in the United States includes the threshold limit 

values or TLVs, which are recommended by the American Conference of Governmental 

Industrial Hygienists (ACGIH). The ACGIH TLVs are developed by committee members of

this professional organization from a review of the published, peer-reviewed literature. TLVs are 

not consensus standards. They are considered voluntary exposure guidelines for use by industrial 

hygienists and others trained in this discipline “to assist in the control of health hazards” 

[ACGIH 2020].
D-2

Outside the United States, OELs have been established by various agencies and organizations and 

include legal and recommended limits. The Institut für Arbeitsschutz der Deutschen Gesetzlichen 

Unfallversicherung (Institute for Occupational Safety and Health of the German Social Accident 

Insurance) maintains a database of international OELs from European Union member states, Canada 

(Québec), Japan, Switzerland, and the United States. The database, available at 

https://www.dguv.de/ifa/gestis/gestis-stoffdatenbank/index-2.jsp, contains international limits for 

more than 2,000 hazardous substances and is updated periodically. 

OSHA (Public Law 91-596) requires an employer to furnish employees a place of employment free 

from recognized hazards that cause or are likely to cause death or serious physical harm. This is true in 

the absence of a specific OEL. It also is important to keep in mind that OELs may not reflect current 

health-based information.

When multiple OELs exist for a substance or agent, NIOSH investigators generally encourage 

employers to use the lowest OEL when making risk assessment and risk management decisions.

Noise

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

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

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

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

average daily noise level of 85 dBA over a 40-year working lifetime have an 8% excess risk of material 

hearing impairment. This excess risk increases to 25% for an average daily noise exposure of 90 dBA 

[NIOSH 1998]. NIOSH defines material hearing impairment as an average of the hearing threshold 

levels for both ears that exceeds 25 dB at frequencies of 1,000 Hz; 2,000 Hz; 3,000 Hz; and 4,000 Hz.

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

of hearing loss. In most cases, NIHL develops slowly from repeated exposure to noise over time, but 

the progression of hearing loss is typically the greatest during the first several years of noise exposure. 

NIHL can also result from short-duration exposures to high noise levels or even from a single exposure 

to an impulse noise or a continuous noise, depending on the intensity of the noise and the individual’s 

susceptibility to NIHL [Berger et al. 2003]. Noise-exposed workers can develop substantial NIHL 

before it is clearly recognized. Even mild hearing losses can impair a person’s ability to understand 

speech and hear many important sounds. In addition, some people with NIHL also develop tinnitus. 

Tinnitus is a condition in which a person perceives sound in one or both ears, but no external sound is 

present. Persons with tinnitus often describe hearing ringing, hissing, buzzing, whistling, clicking, or 

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

from soft to loud. Currently, there is no cure for tinnitus. 

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

approximates the “equal loudness perception characteristics of human hearing for pure tones relative to 

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

hearing loss risk than using unweighted or other weighting measurements [Berger et al. 2003]. The 
D-3

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

Exposure to impulsive noise should never exceed 140 dBA.

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

below the threshold level is not integrated by the noise dosimeter during measurements. The exchange 

rate expresses how much the sound level could increase or decrease while keeping the risk of hearing 

loss the same, if the exposure duration was simultaneously decreased or increased. For example, a 3-dB 

exchange rate requires that noise exposure time be halved for each 3-dB increase in noise levels. 

NIOSH considers the REL and noise measured using the 3-dB exchange rate to more accurately relate 

noise exposures to hearing loss risk [NIOSH 1998]. Using this criterion, an employee can be exposed to

88 dBA for no more than 4 hours, 91 dBA for 2 hours, 94 dBA for 1 hour, 97 dBA for 0.5 hours, etc. 

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

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

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

a hearing loss prevention program [NIOSH 1998]. 

OSHA uses a 90-dBA threshold and a 5-dB exchange rate for the PEL measurements and an 80-dBA 

threshold and 5-dB exchange rate for the AL measurements. Using the OSHA criterion, an employee 

may be exposed to noise levels of 95 dBA for no more than 4 hours, 100 dBA for 2 hours, 105 dBA for 

1 hour, 110 dBA for 0.5 hours, etc. OSHA does not adjust the PEL for extended work shifts. However, 

the AL is adjusted to 84.1 dBA for a 9-hour shift, 83.4 dBA for a 10-hour shift, 82.7 dBA for an 

11-hour shift, and 82.1 dBA for a 12-hour work shift. OSHA requires implementation of a hearing 

conservation program when noise exposures exceed the AL [29 CFR 1910.95]. 

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

thresholds and determine whether their hearing has changed over time. Hearing testing should be done 

in a quiet location, such as an audiometric test booth where background noise does not interfere with 

accurate measurement of hearing thresholds. In workplace hearing conservation programs, hearing 

thresholds must be measured at 500 Hz; 1,000 Hz; 2,000 Hz; 3,000 Hz; 4,000 Hz; and 6,000 Hz. 

Additionally, NIOSH recommends testing at 8,000 Hz [NIOSH 1998]. The OSHA hearing 

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

changes are substantial enough to meet OSHA criteria for a standard threshold shift. OSHA defines a 

standard threshold shift as a change in hearing threshold (relative to the baseline hearing test) of an 

average of 10 dB or more at 2,000 Hz; 3,000 Hz; and 4,000 Hz in either ear [29 CFR 1910.95]. If a 

standard threshold shift occurs, the company must determine if the hearing loss also meets the 

requirements to be recorded on the OSHA Form 300 Log of Work-Related Injuries and Illnesses 

[29 CFR 1904.1]. In contrast to OSHA, NIOSH defines a significant threshold shift as a change in the 

hearing threshold level of 15 dB or more (relative to the baseline hearing test) at any test frequency in 

either ear measured twice in succession [NIOSH 1998].
E-1

Section E: References

Health Effects of Ergonomic Stressors 

Aminian O, Banafsheh Alemohammad Z, Sadeghniiat-Haghighi K [2012]. Musculoskeletal disorders in 

female dentists and pharmacists: a cross-sectional study. Acta Med Iran 50(9):635–640, 

http://acta.tums.ac.ir/index.php/acta/article/view/3964. 

De Sio S, Traversini V, Rinaldo F, Colasanti V, Buomprisco G, Perri R, Mormone F, La Torre G, 

Guerra F [2018]. Ergonomic risk and preventive measures of musculoskeletal disorders in the dentistry 

environment: an umbrella review. PeerJ 6:e4154, http://dx.doi.org/10.7717/peerj.4154. 

Gupta A, Ankola AV, Hebbal M [2013]. Dental ergonomics to combat musculoskeletal disorders: a 

review. Int J Occup Saf Ergon 19(4):561–571, http://dx.doi.org/10.1080/10803548.2013.11077005. 

Kozak A, Schedlbauer G, Peters C, Neinhaus A [2014]. Self-reported musculoskeletal disorders of the 

distal upper extremities and the neck in German veterinarians: a cross-sectional study. PLoS One 

9(2):e89362, http://dx.doi.org/10.1371/journal.pone.0089362. 

Holmstrom SE, Frost PF, Eisner ER [2004]. Veterinary dental techniques for the small animal 

practitioner. 3rd ed. Chapter 13. Philadelphia, PA: Elsevier.

Humantech [2009]. The handbook of ergonomic design guidelines. Version 2.0. Ann Arbor, MI: 

Humantech, Inc.

NIOSH [1997a]. Musculoskeletal disorders and workplace factors: a critical review of epidemiologic 

evidence for work-related musculoskeletal disorders of the neck, upper extremity, and low back. 

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. 

97-141, http://www.cdc.gov/niosh/docs/97-141/. 

Occhionero V, Korpinen L, Gobba F [2014]. Upper limb musculoskeletal disorders in healthcare 

personnel. Ergonomics 57(8):1166–1191, http://dx.doi.org/10.1080/00140139.2014.917205. 

Randall E, Hansen C, Gilkey D, Patil A, Bachand A, Rosecrance J, Douphrate D [2012]. Evaluation of 

ergonomic risk factors among veterinary ultrasonographers. Vet Radiol Ultrasoun 53(4):459–454, 

http://dx.doi.org/10.1111/j.1740-8261.2012.01942.x. 

Sakzewski L, Naser-ud-Din S [2014]. Work-related musculoskeletal disorders in dentists and 

orthodontists: a review of the literature. Work 48(1):37–45, http://dx.doi.org/10.3233/WOR-131712. 

Scuffham AM, Legg SL, Firth EC, Stevenson MA [2010]. Prevalence and risk factors associated with 

musculoskeletal discomfort in New Zealand veterinarians. Appl Ergon 41(3):444–453, 

http://dx.doi.org/10.1016/j.apergo.2009.09.009. 

White SW [2012]. Prevalence and risk factors associated with musculoskeletal discomfort in spay and 

neuter veterinarians. Animals 3(1):85–108, http://dx.doi.org/10.3390/ani3010085. 
E-2

Health Effects of Noise

Berger EH, Royster LH, Royster JD, Driscoll DP, Layne M, eds. [2003]. The noise manual. 5th rev. ed. 

Fairfax, VA: American Industrial Hygiene Association.

Burk A, Neitzel RL [2016]. An exploratory study of noise exposures in educational and private dental 

clinics. J Occup Environ Hyg 13(10):741–749, https://dx.doi.org/10.1080/15459624.2016.1177646. 

Choosong T, Kaimook W, Tantisarasart R, Sooksamear P, Chayaphum S, Kongkamol C, Srisintorn W, 

Phakthongsuk P [2011]. Noise exposure assessment in a dental school. Saf Health Work 2(4):348–354, 

http://dx.doi.org/10.5491/SHAW.2011.2.4.348. 

Gonçalves CG, Santos L, Lobato D, Ribas A, Lacerda AB, Marques J [2015]. Characterization of 

hearing thresholds from 500 to 16,000 Hz in dentists: a comparative study. Int Arch Otorhinolaryngol 

19(2):156–160, http://dx.doi.org/10.1055/s-0034-1390138. 

Jadid K, Klein U, Meinke D [2011]. Assessment of noise exposures in a pediatric dentistry residency 

clinic. Pediatr Dent 33(4):343–348, https://www.ncbi.nlm.nih.gov/pubmed/21903003. 

Koch R [2018]. Hearing health and veterinary dentistry. Letter to the editor. J Am Vet Med Assoc 

252(12):1462.

Masterson EA, Themann CL, Luckhaupt SE, Li J, Calvert GM [2016]. Hearing difficulty and tinnitus 

among U.S. workers and non-workers in 2007. Am J Ind Med 59(4):290–300, 

http://dx.doi.org/10.1002/ajim.22565.

Messano GA, Petti S [2012]. General dental practitioners and hearing impairment. J Dent 40(10):821–

828, http://dx.doi.org/10.1016/j.jdent.2012.06.006. 

NIOSH [2007a]. Kenton County Animal Shelter, Covington, Kentucky. By Achutan C, Tubbs RL. 

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

Prevention, National Institute for Occupational Safety and Health, Health Hazard Evaluation Report 

2006-0212-3035, https://www.cdc.gov/niosh/hhe/reports/pdfs/2006-0212-3035.pdf. 

NIOSH [2007b]. Liberty Veterinary Hospital, Liberty Township, Ohio. By Achutan C, Tubbs RL. 

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

Prevention, National Institute for Occupational Safety and Health, Health Hazard Evaluation Report 

2006-0196-3036, https://www.cdc.gov/niosh/hhe/reports/pdfs/2006-0196-3036.pdf. 

NIOSH [2007c]. Noise exposures and hearing loss assessments among animal shelter workers. By 

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

Control and Prevention, National Institute for Occupational Safety and Health, Health Hazard 

Evaluation Report 2007-0068-3042, https://www.cdc.gov/niosh/hhe/reports/pdfs/2007-0068-

3042.pdf. 

NIOSH [2007d]. Society for the Prevention of Cruelty to Animals, Cincinnati, Ohio. By Achutan C, 

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

Control and Prevention, National Institute for Occupational Safety and Health, Health Hazard 
E-3

Evaluation Report 2006-0222-3037, https://www.cdc.gov/niosh/hhe/reports/pdfs/2006-0222-

3037.pdf. 

Myers J, John AB, Kimball S, Fruits T [2016]. Prevalence of tinnitus and noise-induced hearing loss in 

dentists. Noise Health 18(85):347–354, https://www.ncbi.nlm.nih.gov/pubmed/27991466. 

Schein JD, Gentile A, Haase KW [1970]. Development and evaluation of an expanded hearing loss scale 

questionnaire. Vital Health Stat 2(37):1–42, https://www.ncbi.nlm.nih.gov/pubmed/5310200. 

Setcos JC, Mahyuddin A [1998]. Noise levels encountered in dental clinics and laboratory practice. Int J 

Prosthodont 11(2):150–157, https://www.ncbi.nlm.nih.gov/pubmed/9709605. 

Tak S, Davis RR, Calvert GM [2009]. Exposure to hazardous workplace noise and use of hearing 

protection devices among U.S. workers—NHANES, 1999–2004. Am J Ind Med 52(5):358–371, 

http://dx.doi.org/10.1002/ajim.20690. 

Willershausen B, Callaway A, Wolf TG, Ehlers V, Scholz L, Wolf D, Letzel S [2014]. Hearing 

assessment in dental practitioners and other academic professionals from an urban setting. Head Face 

Med 10:1, http://dx.doi.org/10.1186/1746-160X-10-1. 

Occupational Exposure Limits

ACGIH [2020]. 2020 TLVs® and BEIs®: threshold limit values for chemical substances and physical 

agents and biological exposure indices. Cincinnati, OH: American Conference of Governmental 

Industrial Hygienists.

CFR [2020]. Code of Federal Regulations. Washington, DC: U.S. Government Printing Office, Office 

of the Federal Register, https://www.ecfr.gov/cgi-bin/ECFR?page=browse. 

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, http://www.cdc.gov/niosh/docs/98-126/pdfs/98-126.pdf. 

NIOSH [2007e]. NIOSH pocket guide to chemical hazards. 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. 2005-149, 

http://www.cdc.gov/niosh/npg/. 

Tak S, Davis RR, Calvert GM [2009]. Exposure to hazardous workplace noise and use of hearing 

protection devices among US workers—NHANES, 1999–2004. Am J Ind Med 52(5):358–371, 

http://dx.doi.org/10.1002/ajim.20690. 

Other

National Association of State Public Health Veterinarians [2010]. Compendium of veterinary standard 

precautions for zoonotic disease prevention in veterinary personnel: National Association of State 

Public Health Veterinarians Veterinary Infection Control Committee 2010. J Am Vet Med Assoc 

237(2):1403–1422, http://dx.doi.org/10.2460/javma.237.12.1403. 
E-4

NIOSH [1997b]. Preventing allergic reactions to natural rubber latex in the workplace. By Biagini RE, 

Deitchman S, Esswein EJ, Fedan J, Flesch JP, Hodgins PK, Hodous TK, Hull RD, Jarvis WR, Lewis 

DM, Lipscomb JA, Lushniak BD, Pearson ML, Petsonk EL, Pinkerton L, Siegal PD, Wippel WG, 

Worthington KA. 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. 97-135, https://www.cdc.gov/niosh/docs/97-135/pdfs/97-135.pdf. 

NIOSH [2004]. Preventing occupational exposures to antineoplastic and other hazardous drugs in 

health care settings. By Burroughs GE, Connor TH, McDiarmid MA, Mead KR, Power LA, Reed LD. 

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) 2004-165, 

https://www.cdc.gov/niosh/docs/2004-165/pdfs/2004-165.pdf. 

NIOSH [2010]. Slip, trip, and fall prevention for healthcare workers. By Bell J, Collins JW, Dalsey E, 

Sublet V. Morgantown, WV: 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. 2011-123, https://www.cdc.gov/niosh/docs/2011-123/pdfs/2011-123.pdf. 

Seibert PJ [2003]. The complete veterinary practice regulatory compliance manual. Calhoun: TN, 

www.safetyvet.com. 

USP [2019]. USP general chapter <800> hazardous drugs—handling in healthcare settings. Rockville, 

MD: U.S. Pharmacopeia, https://www.usp.org/compounding/general-chapter-hazardous-drugshandling-healthcare. 

Wright JG, Jung S, Holman RC, Marano NN, McQuiston JH [2008]. Infection control practices and 

zoonotic disease risks among veterinarians in the United States. J Am Vet Med Assoc 232(12):1863–

1872, http://dx.doi.org/10.2460/javma.232.12.1863. 

Veterinary Dentistry 

American Animal Hospital Association [2019]. 2019 AAHA dental care guidelines for dogs and cats. By 

Bellows J, Berg ML, Dennis S, Harvey R, Lobprise HB, Snyder CJ, Stone AES, Van de Wetering AG. J 

Am Anim Hosp Assoc 55(2):49–69, http://dx.doi.org/10.5326/JAAHA-MS-6933. 

Hale F [2013]. Why should you do whole-mouth intra-oral dental radiographs? Can Vet J 54(9):889–

890, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3743578/. 
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