The Continuous Monitoring of the The Continuous Monitoring of the Actual Noise Exposure of Actual Noise Exposure of

Aluminum Smelter Workers Using Aluminum Smelter Workers Using Personal Hearing ProtectionPersonal Hearing Protection

Kevin Michael, Ph.DKevin Michael, Ph.DJ. Alton Burks, J. Alton Burks, Sc.DSc.D, doseBusters USA, , doseBusters USA,

Christine DixonChristine Dixon--Ernst, AlcoaErnst, AlcoaRonda Wilkinson, Alcoa Intalco WorksRonda Wilkinson, Alcoa Intalco Works

Why do Hearing Why do Hearing Conservation Programs Fail? Conservation Programs Fail?

We AssumeWe Assume……

1. HPDs perform according to 1. HPDs perform according to labeled rating when worn in the labeled rating when worn in the

fieldfieldQuality of fit in the field is highly Quality of fit in the field is highly variable variable –– from zero to greater than from zero to greater than the labeled ratingthe labeled ratingProtection is dependent on spectrum Protection is dependent on spectrum of noiseof noise

2. HPDs are worn for entire 2. HPDs are worn for entire exposureexposure

Overall attenuation decreases Overall attenuation decreases quickly with unprotected exposurequickly with unprotected exposure

0

5

10

15

20

25

30

35

8 6 4 2 0

Hours HPD Removed During Exposure

Effe

ctiv

e A

ttenu

atio

n (d

B)

NRR = 30NRR = 20NRR = 10

3. Limited (annual or less) 3. Limited (annual or less) noise sampling is sufficientnoise sampling is sufficient

Natl. Coal Board (GB) study over 6 Natl. Coal Board (GB) study over 6 months found:months found:

Range in daily noise exposure: 8Range in daily noise exposure: 8--40 dBA40 dBA

Range in 5Range in 5--day noise exposure: day noise exposure: 44--32 dBA32 dBA

In general, the accuracy of a In general, the accuracy of a single shift measurement was only single shift measurement was only ±±5 5 dBAdBA

I.ConventionalConventional

Hearing ProtectionHearing Protection

II.PersonalPersonal

Noise DosimetryNoise Dosimetry

III.Continuous MonitoringContinuous MonitoringMeasure and Intervene

Primary (occluded) positionPrimary (occluded) position

Secondary (unoccluded) PositionSecondary (unoccluded) Position

Actual DoseActual Dose

For the first time, Actual Dose is measuredFor the first time, Actual Dose is measuredActual dose = Actual dose = ∑∑ protected exposure + protected exposure + ∑∑ unprotected exposure unprotected exposure Actual dose is the only metric directly Actual dose is the only metric directly related to potential of NIHLrelated to potential of NIHL

RealReal--time Personal Exposure time Personal Exposure Monitoring Monitoring

No reliance on NRR or any other No reliance on NRR or any other laboratory ratinglaboratory ratingPrimary / Secondary Primary / Secondary micmic positions positions

accounts for HPD wearing timeaccounts for HPD wearing timeMeasurement under HPD accounts for Measurement under HPD accounts for

quality of HPD fittingquality of HPD fittingDaily measurement establishes noise Daily measurement establishes noise

exposure history and identifies nonexposure history and identifies non--occupational NIHLoccupational NIHL

Independent AnalysisIndependent Analysis

NIOSH Pittsburgh Research Lab validated NIOSH Pittsburgh Research Lab validated microphone measurement positions in microphone measurement positions in 2004 study2004 study–– Publication in preparationPublication in preparationNational Institute of Health (NIH) has National Institute of Health (NIH) has funded further development of technologyfunded further development of technologyTN OSHA abated noise citation at forging TN OSHA abated noise citation at forging operation based on realoperation based on real--time monitoring time monitoring of actual doseof actual dose

Field Studies

Noise dose: Ambient vs. Inside ESPUnderground Coal

050

100150200250300350400

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49

Measurement Number

Perc

ent d

ose

Ambient

Inside ESP

Noise dose: Ambient vs. Inside ESPUnderground Coal Site 2

050

100150

200250

300

1 10 19 28 37 46 55 64 73 82 91 100

109

Measurement Number

Perc

ent d

ose

AmbientUnder ESP

RealReal--time Monitoring at time Monitoring at SmelterSmelter

Dose measurements using Exposure Smart Dose measurements using Exposure Smart Protector dualProtector dual--channel noise dosimeters, channel noise dosimeters, meeting Type II ANSI S1.25meeting Type II ANSI S1.25--1991 1991 Data presented was measured from March Data presented was measured from March 2005 through May 20072005 through May 2007Use of ESP is ongoing Use of ESP is ongoing –– it is part of their it is part of their PPEPPE

RealReal--time Monitoring at time Monitoring at SmelterSmelter

Ambient noise levels up to 106 dBA Ambient noise levels up to 106 dBA depending on proximity to the crane / depending on proximity to the crane / potline operationspotline operations12 12 –– hour TWAs up to 94 dBAhour TWAs up to 94 dBAMuffMuff--type, PVC foam, polyurethane foam, type, PVC foam, polyurethane foam, reusable silicone and customreusable silicone and custom--molded molded insertinsert--type ESP HPDs type ESP HPDs

Smelter Program DataSmelter Program Data

The 150 workers in the program have The 150 workers in the program have already shown progression toward a shift, already shown progression toward a shift, therefore could be a therefore could be a ‘‘worst caseworst case’’ groupgroupData points > 50% or >100% are Data points > 50% or >100% are valuable identifiers valuable identifiers –– immediate immediate intervention is performed and documented intervention is performed and documented for every overexposurefor every overexposureThese workers had been fitThese workers had been fit--tested, and tested, and were still progressing toward a shiftwere still progressing toward a shift

Results of Intervention

Individual Worker, Daily Exposure

0

20

40

60

80

100

120

140

160

2/17/2005 5/28/2005 9/5/2005 12/14/2005 3/24/2006 7/2/2006 10/10/2006 1/18/2007 4/28/2007 8/6/2007

Date

Perc

ent d

ose,

80

dBA

Thr

esho

ld

Results of Intervention

Individual Worker, Daily Exposure

0

50

100

150

200

250

11/9/2004 2/17/2005 5/28/2005 9/5/2005 12/14/2005 3/24/2006 7/2/2006 10/10/2006 1/18/2007 4/28/2007 8/6/2007

Date

Perc

ent D

ose,

80

dBA

Thr

esho

ld

Program is Ongoing and SuccessfulProgram is Ongoing and Successful

Number of Measurements Per Month

0

500

1000

1500

2000

2500

Feb-05 May-05 Sep-05 Dec-05 Mar-06 Jul-06 Oct-06 Jan-07 Apr-07 Aug-07

Month / Year

Noise Dose, All workersNoise Dose, All workersAluminum Smelter N=43,000Aluminum Smelter N=43,000

Percentage of Dose Measurements > 50%Threshold = 80 dBA

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

Feb-05 May-05 Sep-05 Dec-05 Mar-06 Jul-06 Oct-06 Jan-07 Apr-07 Aug-07

Month / Year

Per

cent

age

/ 100

Increase in Dose / Shift DurationIncrease in Dose / Shift Duration

Average Measurement Duration

9.8

10

10.2

10.4

10.6

10.8

11

11.2

11.4

11.6

11.8

Feb-05 May-05 Sep-05 Dec-05 Mar-06 Jul-06 Oct-06 Jan-07 Apr-07 Aug-07

Month / Year

Hour

s

Protected Dose Data SummaryProtected Dose Data Summary

80 dBA threshold / 90 dBA criterion level80 dBA threshold / 90 dBA criterion level

242 of 42895 measurements > 100%242 of 42895 measurements > 100%=.56%=.56%

1937 of 42895 measurements > 50%1937 of 42895 measurements > 50%=4.5%=4.5%

Threshold Shift AnalysisThreshold Shift Analysis

Mean hearing threshold ( 3, 4, and 6 kHz ) Employees using ESP continuous monitoring in 2005 - 2006

26.0

28.0

30.0

32.0

34.0

36.0

38.0

40.0

42.0

44.0

2002 2003 2004 2005 2006

Year of test

Mea

n H

TL 3

,4,6

kHz

ESP Introducedtrend line

Analysis by Yale Med. School, 31 employees

85 / 3 85 / 3 –– Possible with RealPossible with Real--Time Monitoring Time Monitoring

To actually prevent NIHL, NIOSH To actually prevent NIHL, NIOSH recommends 85 dB criterion level, 3 dB recommends 85 dB criterion level, 3 dB exchange rate.exchange rate.Major change in accumulating doseMajor change in accumulating doseWill be built into all ESP unitsWill be built into all ESP unitsProgressive company can demonstrate Progressive company can demonstrate compliance to more protective standardcompliance to more protective standard

• Workers can make decisions based on simultaneous level and cumulative dose indicators

•• Redefine Redefine ‘‘training and motivationtraining and motivation’’•• Identify nonIdentify non--occupational NIHLoccupational NIHL•• Provide documentation for nonProvide documentation for non--

recordable lossrecordable loss

Looks like more work --- what does it get us?

NIOSH Director, Dr. John Howard, addressing NIOSH Director, Dr. John Howard, addressing Natl. Safety Congress, 11/06: Natl. Safety Congress, 11/06:

"Real"Real--time exposure assessment would time exposure assessment would empower both the employer and the worker empower both the employer and the worker to be able to correlate workplace activities to be able to correlate workplace activities directly with [hazard] exposure levels and to directly with [hazard] exposure levels and to take immediate steps to reduce exposuretake immediate steps to reduce exposure””

Real-time Monitoring: Upstream Prevention of NIHL