Transcript NOISE INDUCED HEARING LOSS - Self Insurers of South Australia

NOISE INDUCED HEARING
LOSS (NIHL)
SISA PRESENTATION
DECEMBER 2007
Based on The Australian Safety and Compensation Council
(ASCC) WORK-RELATED NOISE INDUCED HEARING LOSS IN
AUSTRALIA (APRIL 2006)
BY JASON SPARNON, AUDIOLOGIST &
JAN MACHOTKA, AUDIOLOGIST
Introduction to NIHL
NIHL is defined by National Code of Practice (2004) as
hearing impairment arising from exposure to excessive
noise at work, and is also commonly known as industrial
deafness.
NIHL is entirely preventable but once acquired it is
irreversible
Most recent data (2006) suggests that the number of
NIHL represents 19% of all of all disease-related
claims made and 3.2% of the total disease and injury
related claims.
Causes of NIHL
Continuous Noise exposure
The extent of hearing loss increases with time of exposure,
and also increases with increasing the intensity of sound
levels to which an employee is exposed
Greatest amount damage occurs in the first 10-15 years
Most scientific evidence suggests that the hearing loss
does not progress once exposure to noise has discontinued
National Occupational Health and Safety Commission
(NOHSC) standard identifies a continuous exposure level of
85dB(A) over 8 hrs and a maximum peak exposure level 140
dB(C)
Causes of NIHL
Impulsive Noise
Eg Explosions and Gunfire
Very high sound level eg > 140dB (c)
Can result in asymmetrical loss
Ototoxicity
Exposure to chemicals containing ototoxins
Damage usually associated with combination of ototoxins
and noise
Eg butanol, toluene, carbon monoxide, solvent mixtures
and certain types of medications eg cancer therapy drugs
and asprins
Causes of NIHL
Compounding factors
Non-work related
Eg Congenital factors and recreational noise
Role of co-factors remains poorly understood
Eg cardiovascular disease, diabetes, and neurodegenerative
diseases
Interpreting Audiograms
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Audiograms represent the softest sound a person
can hear.
Conductive loss–outer or middle ear.
Sensorineural loss –inner ear or neural pathway.
Permanent. Often age or noise
related.
Liability usually based upon
sensorineural only
X = left ear. O = Right ear
[ or ] denotes bone conduction
Effect of NIHL
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NIHLs commonly appear as a sloping loss that is
most prominent in the higher frequencies (4k)
Effects speech perception by reducing perception
of consonant sounds (p,b,k,s,z etc) needed for
speech clarity.
Vowels usually remain intact as there is often
good residual hearing throughout the lower
frequencies.
Result = clients report that they can hear people
speaking but not understand them – the vowels
come through clearly but the important
consonants are distorted.
Progression of NIHL ( 0 – 5 years)
Normal Hearing
Mild high frequency loss
= 0%
= 4.6% (40yo), 0% (70yo)
Progression of NIHL (10 – 20 years)
Moderate high
frequency loss
Moderate to severe high
frequency loss
= 16.8% (40yo), 11.9 (70yo)
= 23.8% (40yo), 18.9 (70yo)
Progression of NIHL (25 + years)
Moderate to Profound high
frequency loss
= 67.4% (40yo), 62.5% (70yo)
Calculation of percentage hearing loss (PHL)
Procedure for determine PHL
1. Establish hearing threshold levels at defined frequencies:
500Hz, 1000hz, 1500Hz, 2000Hz, 3000Hz, 4000Hz
2. Go to look up tables (NAL Report No 118) for each of the
frequencies to determine percentage hearing loss (PLH) for
each frequency (PLH500, PLH1000…..);
3. Add up all the percentage hearing losses to give an overall
figure
4. Appropriate deductions (if any) made
5. This % hearing loss (PLH) determined is used for
compensation claims.
Calculation of percentage hearing loss (PHL)
Deductions from PHL
1. Asymmetrical hearing loss
Noise Ordinarily effects both
Ears equally.
? – shooter
- tumor
= 21.2%
= 16.8% (using L levels for R)
Calculation of percentage hearing loss (PHL)
Deductions from PHL (cont’d)
2. Non-sensorineural hearing loss
= 61.7 %
= 16.9%
Deductions from PHL (cont’d)
3. Age related hearing loss (presbyacusis)
= 23.8% (40yo),
= 18.9 (70yo)
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Other possible deductions
4. Pre-employment hearing loss and Congenital hearing loss
5. Non-work related medical conditions eg diabetes
6. Recreational noise exposure
7. Evidence suggests that noise exposure alone does
not usually produce a loss greater than 75 dBHL at
high frequencies, and 40 dBHL at lower frequencies.
Statistics of NHIL claims
Table 1. Comparison of Comparison of Workers’ Compensation
Arrangements.
Jurisdiction
Industrial deafness threshold, i.e. when a claim can be made
Comcare
5%.
Seacare
10%
VIC
10%
NSW
6% binaural loss
SA
5%
WA
10% (Above baseline hearing loss previously
assessed)
QLD
5%
TAS
5% binaural loss
NT
5% whole person impairment (percentage of loss of whole body)
ACT
A worker is not entitled to compensation if the total
hearing loss is less than 6%
Statistics of NHIL claims
Table 2. Number of Claims for NIHL
1998-99
1999-2000
2000-2001
2001-2002
Claims for NIHL
5755
5280
5185
4510
Percentage of Total
Disease Claims
24
22
21
19
Percentage of Total
Disease and Injury
Claims
3.8
3.5
3.5
3.2
Claims in SA decreased from 370 in 1999 to 190 in 2002
Although the number of NIHL claims has been reduced, it does
not mean that noise induced deafness in Australia has been
reduced
*most recent data available (2006)
Figure 1. NIHL Claims per Exposed Employees (2001/2)
1200
1000
800
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400
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Number of claims per hundred thousand employees
Statistics of NHIL claims
The highest number of claims are made by: Labourers and related workers, 33%
Tradespersons and related workers, 30% Intermediate production & transport
workers (plant or machine operators or transport drivers),25%
Statistics of NHIL claims
The average cost of workers compensation claims for NIHL in
2001/2 was calculated to be $6711.
Therefore, for Australia, the direct cost of NIHL claims for
2001/2 is calculated to be $6711 x 4510 claims i.e. just over
$30 million.
This figure does not include Hearing Aid fittings
Prevention NIHL
Noise Control and Hearing Loss Prevention
Program
Actions to reduce noise exposure eg. Noise insulation, ear
protection
Actions to monitor the health of employees eg, annual
hearing screening programs
Establishing a noise control policy and
program
noise control policy and program will enable a systematic
approach to hearing conservation in a company eg purchasing
policy on equipment noise levels, mandatory ear protection,
training programs for employees
Who is Hearing Matters
3 audiologists – Jan, Tara, Jason
Only independent clinic owned by its audiologists
NOT aligned by any hearing aid manufacturer
NOT solely a hearing aid clinic – also diagnostic clinic
Services provided by Hearing Matters
Determination of NIHL percentage and diagnostic reports.
Referrals to ENT specialists when appropriate
Hearing aid fittings and tinnitus treatment when appropriate
Noise protection equipment
Hearing Aids
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CIC: Mild – Moderate
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ITC: Moderate
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BTE: Moderate-Severe
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Open-Fit: Mild – Severe