hearing conservation metrics theresa y. schulz, phd. lt. col. usaf (ret.)
TRANSCRIPT
Hearing ConservationMetrics
Theresa Y. Schulz, PhD.Lt. Col. USAF (ret.)
Topics
Leading vs Lagging Indicators
Motivating Workers
Audiometric Testing
Earplug Fit Testing
Continuous Monitoring
Indicators for Hearing Loss:• Standard Threshold Shift
• Temporary Threshold Shift
• Recordable Hearing Loss
• Dosimetry
• In-ear Dosimetry
• Personal Attenuation Level (PAR)
• Hearing Loss Compensation
Hearing Conservation Metrics
Lagging Indicators vs. Leading Indicators
Hearing Conservation Metrics
Indicators for Hearing Loss:• Standard Threshold Shift
• Temporary Threshold Shift
• Recordable Hearing Loss
• Dosimetry
• In-ear Dosimetry
• Personal Attenuation Level (PAR)
• Hearing Loss Compensation
Hearing Conservation Metrics
• Ototoxic by themselves• Synergistic effect with noise• Large differences in sensitivity• Recommend: increased frequency
of audiometric testing
Synergistic Ototoxics
• Carbon Monoxide
• Hydrogen CyanideNOISE
Hazardous Noise
Ototoxic Chemicals
Confirmed Ototoxics
Ethyl Benzene
Lead and inorganic compounds (as Pb)
Styrene
Toluene
Trichloroethylene
PossibleCarbon disulfide
n-Hexane
Xylene
Hearing Conservation Metrics
Conduct audiometric testing during the work shift
• TTS vs PTS
Hearing Conservation Metrics
Percentage of exposed workers with STS/year
Affected by: Duration of employment, Demographics
Recent analysis of large database: 1980-present: 1.5% per year• In non-noise exposed employees: roughly 1%• Current corporate policy: 1% rate per year, or
equivalent to internal non-occupationally exposed population- ?Best Practice?
Hearing Conservation Metrics
Use Early Warning Flags• Identify individuals at risk for significant loss in
future• Identify problem jobs/work areas
Hearing Conservation Metrics
Age-Corrected STS Represents Significant Hearing Loss!
Study of industrial workers: • 52% of OSHA recordable STS cases
(new definition) had compensable hearing impairment (AAOHNS criteria)!
• Median time to develop recordable STS: approx. 10 years*
Hearing Conservation Metrics
* Rabinowitz et al. Impact of OSHA rule: recording hearing loss JOEM 2003
So…..
Age-Corrected STS
is NOT
an “Early Flag”!
Hearing Conservation Metrics
Candidate “Early flags” (indicators)• 10 dB shift from baseline in avg 2,3,4KHz (not
age-corrected)• 15dB shift from baseline (at least one
frequency 1-6KHz) (Department of Defense)• 15dB shift from baseline (at least one
frequency 1-6KHz) confirmed on second test (NIOSH)
• Others:
• 7dB shift 2,3,4KHz?
• 5dB shift 2,3,4KHz?
Hearing Conservation Metrics
Compensable Hearing Impairment:
• How many workers have absolute loss of >25dB avg 500,1K,2K,3KHz?• Useful for workers comp liability as well
as need for workplace accommodation, etc.
Noise Levels- trends over time for individual departments.
Hearing Conservation Metrics
Fit Testing In-Ear Dosimetry
Hearing Conservation Metrics
How much noise is reaching the ear of the worker ?
That is completely unknown …
Noise Level = 100 dB
Noise Reduction Rating = 30 dB
(55 – 104 dB)
Earplug Fit Testing
How much protection?
0 dB 0 dB>33 dB
EAR #1EAR #2
EAR #3
Earplug Fit Testing
-10
12
5
25
0
50
0
10
00
20
00
31
50
40
00
63
00
80
00
Frequency in Hz
90
80
70
60
50
40
30
20
10
0
Att
enu
atio
n in
dB
Max Poor FitNRR = 0dB
Max Good FitNRR = 33dB
Good Fit vs Bad Fit
Earplug Fit Testing
Loudness Balance
(Real-Ear Attenuation Above Threshold)
Earplug Fit Testing
Test Sequence
Part 1:Both ears
unoccludedThis sets the baseline level for each ear, and measures any asymmetry.
Part 2:Right ear occluded
Attenuation for the right ear is measured.
Part 3:Both ears occluded
Attenuation for the left ear is measured.
Result ~ Personal Attenuation Rating (PAR)
1. Measures real-world attenuation of any earplug
2. Fulfills requirement to ‘ensure proper fitting’ of earplugs and evaluate their attenuation
3. On-screen training videos
4. Administered anywhere, quiet room not required
5. Protected exposure level and safe exposure level calculated
OSHA Alliance: Best Practice Bulletin www.hearingconservation.org
Additional Information www.hearforever.org
Hearing Conservation Metrics
From Kevin Michael, PhD and Cindy Bloyer “Hearing Protector Attenuation Measurement on the End-User”
192 users of a flanged reusable earplug ~ 27 NRR
Retraining and refitting
resulted in an average
14 dB improvement for this group
Real user
attenuatio
n
<0 to 38 dB
30
20
10
0
-10
Att
enu
atio
n i
n d
B
40
50NRR = 27 Multiple-Use Earplug
Real-World Attenuation ≠ NRR
Noise Reduction RatingHearing Conservation Metrics
Variation from Published NRR
-30
-25
-20
-15
-10
-5
0
5
10
0 10 20 30 40 50 60 70 80 90 100
Workers
Dif
fere
nce
in
dB Published
NRR
Distribution of PARs
0
2
4
6
8
10
12
Variation from Published NRR
Wor
kers
Hearing Conservation Metrics
Distribution of PARs
0
2
4
6
8
10
12
Variation from Published NRR
Wor
kers
Personal Factors Gender
Age
Years in Noise
Ear Canal Size
Familiarity
Model of Earplug
Program Factors # Group Trainings
# Personal Trainings
Hearing Conservation Metrics
Difference on 2nd / 3rd Test
-30
-25
-20
-15
-10
-5
0
5
10
Subjects
Va
ria
tio
n f
rom
NR
R Published NRR
Trying a second earplug often improves attenuation
REDUCING COSTS / CLAIMSHearing Conservation Metrics
“How well can users predict their attenuation after a short fit-testing
training session?"
Reducing Costs of Hearing LossHearing Conservation Metrics
Fitting Tips
Ability to Predict Noise Reduction
Accuracy of estimate
(75% were within one category of actual PAR)
0
10
20
30
40
50
60
70
80
90
100
Same Category One off Two off Three off Four off
28%
47%
14%
Reducing Costs of Hearing LossHearing Conservation Metrics
Personal Attenuation Rating (PAR)
0
10
20
30
40
50
60
70
80
90
0 5 9 14 19 23 28 33 37 42 >42
PAR (in dBA)
# of
Wor
kers
Before After
Hearing Conservation Metrics
0
10
20
30
40
50
60
70
<70 70-74 75-79 80-84 84-89 90+
Protected Exposure Level (PrEL)
Nu
mb
er o
f W
ork
ers Initial Final
Hearing Conservation Metrics
Protected Exposure Levels (PrEL)
0
1
2
3
4
5
6
7
8
9
< 70 71-75 76-80 81-85 86-90 >90
PrEL Range (in dB)
Nu
mb
er o
f In
div
idu
als
Initial PrEL Final PrEL
Hearing Conservation Metrics
"I know how to better fit my
earplugs now."
"I was amazed with the results
after being shown the proper way to
use earplugs.
"Learned A LOT about best
earplugs for me"
"I found a more comfortable fit. It
was very beneficial."
"Very glad I did the fitting test.
Now I know the correct way to fit my ear plugs.”
"Recently had threshold shift" "Found better
earplugs"
Field Verification – Fit-Testing
"Feel like am protected now!"
"I had no idea I was not using my
earplugs correctly."
Reducing Costs of Hearing LossHearing Conservation Metrics
Earplug fit-testing as a Problem Solver
• Training tool for noise-exposed workers
• Train-the-trainer tool
• Follow-up on significant threshold shifts in hearing
• Documentation of HPD adequacy
• Assessment of overall HCP effectiveness
• Match HPD to worker’s specific noise level
• Selection of appropriate HPDs for new hires
• Benefits per Best Practices Bulletin (OSHA Alliance)
Hearing Conservation Metrics
In-ear dosimetry measures/records worker’s actual noise dose, with and without protection
Provides real-time monitoring and alerts when worker approaches/exceeds safe limits
Only metric with direct potential to measure and prevent further progression of occupational hearing loss
Reducing Costs of Hearing LossContinuous Monitoring / In-ear-dosimetry
• Mean Hearing Threshold (2k, 3k, 4kHz): 2000 – 2007 (N = 46)
• Employees using continuous in-ear dosimetry starting in 2005
Mean hearing threshold (2,3, and 4 kHz) Employees using continuous ESP starting in 2005
2000 - 2007 (N=46)
0
5
10
15
20
25
30
35
40
45
50
2000 2001 2002 2003 2004 2005 2006 2007
Year of test
Mean
HTL
3,4,6
kHz
ESP Introduced trend line
Reducing Costs of Hearing LossHearing Conservation MetricsContinuous Monitoring / In-ear-dosimetry
In-ear dosimetry as a Problem Solver
Employees with Documented Noise-Induced Hearing Loss or Standard Threshold Shift [STS]
Employees At-Risk for NIHL
Employee Training + Sampling
Dual-Protection/Extreme Noise Exposure
Engineering Controls
Reducing Costs of Hearing Loss
In-ear monitoring as a Problem Solver
Hearing Conservation Metrics
Preventive Action After NIHLIn practice, an OSHA-recordable STS is not a preventive action
It is documentation of a hearing loss after the fact.
How soon will an employee suffering NIHL be re-fit / re-trained ?
“Best case scenario” per Hearing Conservation Amendment
0 2 4 6 8 10 12 14 16
Months
• Audiometric test • Retest • Notification
In-ear dosimetry “worst case” scenario …
1 Day
Hearing Conservation Metrics
PROS• Estimate Measure
• NRR obsolete
• Fulfills OSHA compliance
• Eliminates need for de-ratings
• Medico-legal cases
• Delineates non-occupational
• Eliminates double protection
• Provides employee feedback
• (HPD Inventory control)
CONS• Cost
• Time Investment
• Not standardized
Reducing Costs of Hearing Loss
Tools for HCP Prevention Metrics
Hearing Conservation Metrics
Training + Motivation
Common Objections to Wearing HPDs
“Hearing protectors are uncomfortable to wear.”
“I don’t need them! I am used to the noise.”
“I already lost some of my hearing, so why should I wear them?”
“I can’t hear my co-workers if I wear them.”
“I can always get fit with a hearing aid.”
“Can I hurt my eardrums if I insert an earplug to deeply.”
“My machine sounds different.”
“Won’t I get an ear infection?”
Training + Motivation
Show, Don’t Tell• Provide copy of annual audiogram
to worker• Use personal examples to
demonstrate consequences of hearing loss
• Ask questions:• What is your favorite sound?• What sound would you miss the
most if you couldn’t hear?• What sounds connect you to people
and your environment?
Training + Motivation
Personalize Hearing Loss
Training + Motivation
Training Materials• www.hearforever.org• www.hearingconservation.org• atl.grc.nasa.gov/
HearingConservation/Resources/index.html
• www.cdc.gov/niosh/topics/noise• www.dangerousdecibels.org
Demonstrate Future Risk
www.hearforever.org/honaaohn
Training + Motivation
Send Clear Message On + Off Job
HC Part of Everyday Life• Include recreational hearing
conservation in annual training
• Provide extra HPDs for home use
• Promote Hearing Conservation at company/family events
Training + Motivation
Remove Barriers to HPD Use
Make HPDs Available• Highlight “where to find HPDs” in
annual training• Make sure HPDs are well-stocked
and accessible• Include group of workers in
selection process for increased acceptance
• Offer wide variety to match comfort, job requirements
Make Hearing Conservation Part of Your
Everyday Life
www.hearforever.org/honaaohn