Download Best Practices in Hearing Conservation

Determining Protected
Exposures for NoiseExposed Workers
Theresa Y. Schulz, PhD.
Lt. Col. USAF (ret.)
Agenda
•
•
•
•
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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 of protection.
90% 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 dB
How much noise is
reaching the ear of
the worker ?
That is completely unknown …
(55 – 104 dB)
0 dB
0 dB
33 dB
EAR #1
EAR #2
EAR #3
How much protection?
Good Fit vs Bad Fit
90
80
Attenuation in dB
70
60
50
40
30
20
10
0
-10
Max Good Fit
NRR = 33dB
Max Poor Fit
NRR = 0dB
8000
6300
4000
3150
2000
1000
500
250
125
Frequency in Hz
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
192 users of a flanged reusable earplug ~ 27 NRR
50
NRR = 27 Multiple-Use Earplug
Attenuation in dB
40
30
20
10
0
-10
From Kevin Michael, PhD and Cindy Bloyer “Hearing Protector Attenuation Measurement on the End-User”
≠ NRR
Noise Reduction Rating
De-Rating Methods
OSHA
NIOSH
CSA
NRR ÷ 2
Earmuffs
NRR – 25%
Class
A up to 100
Formable Earplugs
NRR – 50%
B up to 95
(feasibility of
engineering
controls)
Fit
Test
All Other Earplugs
NRR – 70%
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
DESCRIPTION
Conventional
HPD
 Perform lab test with 20 subjects who fit the
protector after brief training
 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
Test
Protocol
Current NRR
Proposed NRR
A single-number estimate
of protection
A high/low range of
estimated protection
Estimates the 98th
percentile of protection
obtained by users when
properly fitted
Estimates the 80th and 20th
percentile of protection
obtained by users
ANSI S.3.19-1974
[Experimenter Fit]
10 subjects for earplugs
and earmuffs, HPDs fit by
experimenter
ANSI S12.6-2008 Method A
[Supervised Subject-Fit]
20 subjects [for earplugs] or
10 subjects [for earmuffs],
HPDs fit by subject after brief
training
Noise Reduction Rating
Current vs. Proposed NRR
Current NRR
Proposed NRR
Application
Intended for use with dBC
noise measurements.
Requires a 7 dB correction
for use with dBA noise
measurements.
Can be applied directly to
dBA noise measurements
De-Rating
Various de-rating schemes
promulgated by various
organizations [including
OSHA]
Designed to be used with
no required de-rating
Retesting
Currently, no retesting of
HPDs required
Periodic retesting of HPDs
required every 5 years
Noise Reduction Rating
Current NRR Label
80th %
20th %
Minimallytrained
Proficient
Users
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
Loudness Balance
(R.E.A.T.)
(Real-Ear Attenuation Above
Threshold)
Microphone
in Real-Ear
In-Ear Dosimetry
(M.I.R.E.)
Ear plug fit-testing methods
Audiomet
FitCheck
ric
EARfit
VeriPRO
REAT
REAT
MIRE
REAAT
Sound booth
Very Quiet
Room
Quiet Room
Anywhere
PAR
PAR
Derived PAR
PAR
Any earplug
Any earplug
Selected
modified
earplugs
Any earplug
Special
training
Special
training
Special
training
Anyone can
perform
Reducing Costs + Claims
OSHA Alliance: Best Practice Bulletin
www.hearingconservation.org
Additional Information
www.howardleight.com
Earplug fit-testing
Reducing
Costs + Claims
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)
Review of some
fit-testing
studies
Noise Reduction Rating – in the real world
Attenuation in dB
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
Published
NRR
0
-5
-10
-15
-20
Distribution of PARs
-25
12
-30
0
10
20
30
40
50
10 60
Workers
Workers
Difference in dB
5
70
80
90
100
8
6
4
2
0
-30
-25
-20
-15
-10
-5
0
5
10
Variation from Published NRR
15
20
25
30
Fit-testing Studies
Personal Factors
Gender
Age
Distribution of PARs
12
Years in Noise
Workers
10
Ear Canal Size
8
6
Familiarity
4
Model of Earplug
2
0
-30
-25
-20
-15
-10
-5
0
5
10
15
20
25
30
Program Factors
Variation from Published NRR
# Group Trainings
# Personal Trainings
REDUCINGStudies
Fit-testing
COSTS / CLAIMS
Difference on 2nd / 3rd Test
10
Variation from NRR
5
Published
NRR
0
-5
-10
-15
-20
-25
-30
Subjects
Trying a second earplug often
improves attenuation
Self-Efficacy Pilot Study
“How well can
users predict their
attenuation after a
short fit-testing
training session?”
Pilot
PilotStudy
study
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
RE=29
LE=22
LE=27
Average improvement 7.5 dB
Pilot
Study
Pre and
Post-Test
Pre- and Post-Test
How would you rate your ability to fit your earplugs?
1
2
3
4
5
Don’t know how
I do OK
Expert
Pilot
Study
Pre and
Post-Test
Post-Test Ability
Initial Ability
Expert
Expert
Pretty good
I do OK
I do OK
Don't know
how
Not good
I do OK
Pretty good
Expert Fitter
Pretty good
Pilot
Study
Pre and
Post-Test
Self-Efficacy
“How much noise do you think your
earplugs block?”
76% (13 of 17)
judged attenuation as
HIGHER post-test
Pilot
Study
Pre and
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
Pilot
Study
Pre and
Post-Test
“How well can users predict their
attenuation after a short fit-testing
training session?"
Pilot
Study
Pre and
Post-Test
Ability to Predict Noise Reduction
(Each subject estimated atten. for each ear)
Number of Ears
20
18
16
14
12
10
8
6
4
2
0
Within 5 dB
category
+/- 7.5 dB
+/- 12.5 dB
(one Category off) (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)
Risk
Reducing
Costs + Claims
RiskManagement
Management
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
In-earManagement
Reducing
Risk
dosimetry
Costs +as
Claims
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
Risk Management
Research
> Alcoa
Intalco Works
Reducing
Risk
Management
Costs
+ Claims
Mean hearing
threshold
and 4 kHz)2000 – 2007 (N = 46)
• Mean Hearing Threshold
(2k,
3k, (2,3,
4kHz):
Employees using continuous ESP starting in 2005
• Employees using continuous in-ear dosimetry starting in 2005
2000 - 2007 (N=46)
50
ESP Introduced
Mean HTL 3,4,6kHz
45
trend line
40
35
30
25
20
15
10
5
0
2000
2001
2002
2003
2004
Year of test
2005
2006
2007
Reducing
Risk
Management
Costs + Claims
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
• Retest
• Audiometric test
0
2
4
6
8
10
Months
12
14
• Notification
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 wellstocked and accessible
• Include group of workers in
selection process for
increased acceptance
• Offer wide variety to match
comfort, job requirements
Training + Motivation
Hearing Loss Due To
Noise Exposure Is …
Painless
Permanent
Progressive
… and very Preventable!