Transcript Best Practices in Hearing Conservation
Determining Protected Exposures for Noise Exposed Workers
Theresa Y. Schulz, PhD.
Lt. Col. USAF (ret.)
Agenda
• Background • NRR • Fit-testing studies • Fitting HPDs • Motivation
Background
Noise-induced hearing loss is the most common permanent and preventable occupational injury in the world.
World Health Organization
Background Worker’s Compensation
In many countries, excessive noise is the
biggest compensable occupational hazard
. Cost of NIHL to developed countries ranges from
0.2 to 2% of its GDP
. NIHL is
on the rise
globally. (Source: WHO)
Background United States Statistics Most common
occupational injury in the United States.
22 million US workers
are exposed to hazardous noise at work on a daily basis. Approx.
8 million Americans suffer from NIHL
. (Source: NIOSH, 2009)
Background
In the United States,
76%
of noise-exposed workers need no more than
10 dB 90%
of protection. need no more than
15 dB
of protection.
Noise Reduction Rating (NRR)
Noise Reduction Rating
Noise Reduction Rating
Noise Level =
100 dB
Noise Reduction Rating =
30
How much noise is reaching the ear of the worker ?
dB
That is completely unknown …
(55 – 104 dB)
0
dB
0
dB
33
dB
EAR #
1
EAR #
2
How much protection?
EAR #
3
20 10 0 -10 50 40 30 90 80 70 60
Good Fit vs Bad Fit Frequency in Hz
Max Good Fit NRR = 33dB Max Poor Fit NRR = 0dB
Noise Reduction Rating
Noise Reduction Rating
• • A laboratory estimate of the amount of attenuation achievable by 98% of users when properly fit A population-based rating ― some users will get more attenuation, some will get less
The NRR is only a population estimate, not a predictor of individual attenuation.
Noise Reduction Rating
NVLAP-Accredited Labs
San Diego, CA Indianapolis, IN State College, PA
Noise Reduction Rating – Determining an NRR
• 10 human subjects tested in a reverberant room • Tested with ears open/occluded at nine frequencies • Each subject tested 3x • NRR calculated to be population average A test subject in the Howard Leight Acoustical Lab, San Diego, CA, accredited by the National Voluntary Laboratory Accreditation Program (NVLAP)
Noise Reduction Rating – in the real world
Real-World Attenuation ≠ NRR
192 users of a flanged reusable earplug ~ 27 NRR 50
NRR = 27 Multiple-Use Earplug
40 30 20 10 0 -10 From Kevin Michael, PhD and Cindy Bloyer “Hearing Protector Attenuation Measurement on the End-User”
Noise Reduction Rating
De-Rating Methods OSHA NIOSH CSA
NRR ÷ 2 (feasibility of engineering controls) Earmuffs
Fit
Formable Earplugs
Test
All Other Earplugs NRR – 70% Class A up to 100 B up to 95 C up to 90
Noise Reduction Rating
Noise Reduction Rating
• The EPA recently made an announcement about a proposed change to the Noise Reduction Rating [NRR] • This is the first change in hearing protector regulation in nearly 30 years
Noise Reduction Rating
Three New Labels
LABEL Conventional HPD DESCRIPTION Perform lab test with
20
subjects
who fit
protector after brief training the Estimates the range of protection achieved by 20% and 80% of users Active Noise Reduction [ANR] • Uses a Microphone-in-Real-Ear [MIRE] method to estimate protection • Measured with ANR turned OFF and ON to show the additional attenuation from the ANR Level Dependent/ Impulse Noise Reduction • Testing will occur over a range of impulse noise levels. Multiple tests to determine lower and upper ranges of impulse noise reduction • Will include two ranges to identify attenuation for passive and active modes
Noise Reduction Rating
The New System: A Range
• Represents a
range of expected protection
• Uses a new ANSI-standard (S12.6-2008) lab testing to generate the attenuation ratings • New NRR will provide an indication of how much attenuation
minimally-trained users
[the lower number] versus
highly-motivated trained users
[the higher number] can be expected to achieve • For some hearing protectors, the spread of this range may be quite significant
Noise Reduction Rating
Current vs. Proposed NRR
Rating Description of Rating Current NRR
A single-number estimate of protection Estimates the 98 th percentile of protection obtained by users when properly fitted
Proposed NRR
A high/low range of estimated protection Estimates the 80 th and 20 th percentile of protection obtained by users
Test Protocol
ANSI S12.6-2008 Method A ANSI S.3.19-1974 [Supervised Subject-Fit] [Experimenter Fit]
20 subjects [for earplugs] or 10 subjects for earplugs 10 subjects [for earmuffs], and earmuffs, HPDs fit by HPDs fit by subject after brief experimenter training
Noise Reduction Rating
Current vs. Proposed NRR
Current NRR Proposed NRR Application De-Rating Retesting
Intended for use with dBC noise measurements. Can be applied directly to Requires a 7 dB correction dBA noise measurements for use with dBA noise measurements.
Various de-rating schemes promulgated by various organizations [including OSHA] Currently, no retesting of HPDs required Designed to be used with no required de-rating Periodic retesting of HPDs required every 5 years
Noise Reduction Rating 80 th % Minimally trained 20 th % Proficient Users
Current NRR Label Mock-up of New Label
Noise Reduction Rating
How to Apply the New Label
Two-number range displays the estimated protection achievable by minimally-trained users [80%] versus proficient users [20%].
80% 20%
A wider range indicates greater variability in the fit of that HPD. Smaller ranges indicate more consistency of fit. For example, earmuffs will usually have a tighter fitting range than earplugs, and may have a smaller NRR range.
Noise Reduction Rating Will OSHA 29 CFR 1910.95 change?
• OSHA has not announced any proposed changes to the Occupational Noise Standard • OSHA will presumably respond to the revised NRR label by issuing a field directive or technical memorandum, informing its compliance officers how to deal with the new two-number NRR range
Noise Reduction Rating Will the new rating methods favor earplugs or earmuffs?
• While a well-fit foam earplug generally has greater attenuation than most earmuffs, earmuffs are inherently easier to fit for most users • There is less variability in the fit of earmuffs • Overall range of attenuation for earmuffs will usually be tighter and often higher, than earplugs • Workers should be offered a choice of earplugs, bands
and
earmuffs that meet the requirements of the work environment
Noise Reduction Rating
Earplug Fit Testing
Provides an accurate, real-world picture of hearing protector effectiveness.
Identify if hearing protection users are: • Receiving optimal protection • Require additional training • Need to try a different earplug style
Earplug Fit-testing As a problem solver:
• Derating Schemes • One-on-One Training • HPD Selection • NRR Change
Field Verification – Fit-Testing Real-Ear Attenuation at Threshold (R.E.A.T.) Loudness Balance ( Real-Ear Attenuation Above Threshold ) Microphone in Real-Ear (M.I.R.E.) In-Ear Dosimetry
Ear plug fit-testing methods Audiomet ric REAT FitCheck EARfit REAT MIRE Quiet Room Sound booth PAR Any earplug Very Quiet Room PAR Any earplug Special training required Special training required Derived PAR Selected modified earplugs Special training required VeriPRO REAAT Anywhere PAR Any earplug Anyone can perform
Reducing Costs + Claims OSHA Alliance: Best Practice Bulletin www.hearingconservation.org
Additional Information www.howardleight.com
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)
Review of some fit-testing studies
Noise Reduction Rating – in the real world
Real-World Attenuation ≠ NRR
192 users of a flanged reusable earplug ~ 27 NRR 50
NRR = 27 Multiple-Use Earplug
40 30 20 10 0 -10 From Kevin Michael, PhD and Cindy Bloyer “Hearing Protector Attenuation Measurement on the End-User” Retraining and refitting resulted in an average 14 dB improvement for this group
Fit-testing Studies Variation from Published NRR
10 5 0 -5 -10 -15 -20 -25 -30 0
Published NRR
10 20 30
Distribution of PARs
40
12
50
10
60
Workers 8 2 0 6 4 -30
70
-25 -20
80 90 100
-15 -10 -5 0 5 10 Variation from Published NRR 15 20 25 30
Fit-testing Studies Distribution of PARs 12 10 8 6 4 2 0 -30 -25 -20 -15 -10 -5 0 5 10 Variation from Published NRR 15 20 25 30 Personal Factors Gender Age Years in Noise Ear Canal Size Familiarity Model of Earplug Program Factors # Group Trainings # Personal Trainings
Difference on 2nd / 3rd Test
-10 -15 -20 -25 -30 10 5 0 -5
Subjects Trying a second earplug often improves attenuation Published NRR
Self-Efficacy Pilot Study “How well can users predict their attenuation after a short fit-testing training session?”
Subjects
• Subjects: 17 construction workers with varied HPD experience levels • Equipment: VeriPRO earplug fit-test system • HPD: Volunteers • Process: 2-4 Quick Check fits where employee sees feedback of exact PAR
Pilot Study
Results
Data show improved PARs!
Initial Final RE=19 LE=22 RE=29 LE=27 Average improvement 7.5 dB
Pre- and Post-Test
How would you rate your ability to fit your earplugs?
1 2 3
Don’t know how I do OK
4 5
Expert
Initial Ability
Expert Pretty good I do OK
Post-Test Ability
Don't know how Not good I do OK Pretty good Expert Fitter
Expert I do OK Pretty good
Self-Efficacy
“How much noise do you think your earplugs block?”
76% (13 of 17) judged attenuation as HIGHER post-test
Post-Test
Are you better able to assess the effectiveness of your earplugs after VeriPRO fit-testing?
1 2 3 4 5
No Maybe No change Improved Yes
64% (11 of 17) rated their ability
HIGHER
post-test
“How well can users predict their attenuation after a short fit-testing training session?"
Ability to Predict Noise Reduction
20 18 16 14 12 10 2 0 8 6 4 Within 5 dB category +/- 7.5 dB (one Category off) +/- 12.5 dB (2 categories off)
Risk Management
Risk Management Indicators for Hearing Loss: • Standard Threshold Shift • Temporary Threshold Shift • Recordable Hearing Loss • Dosimetry • Labeled NRR (derated?) • In-ear Dosimetry • Personal Attenuation Level (PAR)
Risk Management Lagging Indicators vs. Leading Indicators
Risk Management Indicators for Hearing Loss: • Standard Threshold Shift • Temporary Threshold Shift • Recordable Hearing Loss • Dosimetry • Labeled NRR (derated?) • In-ear Dosimetry • Personal Attenuation Level (PAR)
Fit Testing In-Ear Dosimetry
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
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
Risk Management
• •
Mean Hearing Threshold (2k, 3k, 4kHz): 2000 – 2007 (N = 46) Employees using continuous in-ear dosimetry starting in 2005
50
Employees using continuous ESP starting in 2005
ESP Introduced trend line 45 40 35 30 25 20 15 10 0 5 2000 2001 2002 2003 2004 2005 2006 2007
Year of test
Preventive Action After NIHL
In 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 In ear dosimetry “worst case” scenario … 1 Day
• Audiometric test • Retest • Notification 0 2 4 6 8 Months 10 12 14 16
Fitting Tips
Roll-Down Foam Earplugs
1. Roll
entire earplug into a crease-free cylinder
2. Pull Back
pinna by reaching over head with free hand, gently pull top of ear up and out
3. Insert
earplug well into ear canal and hold until it fully expands
Earplug Fitting
Fitting Tips
Fitting Tips
Multiple-Use Earplugs
1. Reach
While holding the stem, reach hand overhead and gently pull top of ear up and back.
2. Insert
Insert earplug so all flanges are well inside the ear canal.
3. Fit
If properly fitted, only the stem of the earplugs should be visible to someone looking at you from the front.
Fitting Tips
Visual + Acoustical Checks
1. Visual Check
The earplug should sit well inside the ear canal and not stick out.
2. Acoustical Check
Cup hands over ears and release. Earplugs should block enough noise so that covering your ears with hands should not result in a significant noise difference.
Training + Motivation
Training + Motivation
Personalize Hearing Loss
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
Demonstrate Future Risk
• • • • •
Training Materials
www.hearforever.org
www.hearingconservation.org
atl.grc.nasa.gov/HearingConserv ation/Resources/index.html
www.cdc.gov/niosh/topics/noise www.dangerousdecibels.org
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
Training + Motivation