Transcript Slide 1

Comparison of Damage Risk Criteria Using
the Albuquerque Blast Overpressure Walkup
Study Data
William J. Murphy
Amir Khan
Peter B. Shaw
Hearing Loss Prevention Section
Division of Applied Research and Technology
National Institute for Occupational Safety and Health
The results reported in this paper represent the opinions
of the authors and are not representative of the policies of the
National Institute for Occupational Safety and Health.
Blast Overpressure Studies
Outline
 Blast Overpressure Exposure Evaluations
 MilStd 1474D
 LAeq8hr Protected & Unprotected
 AHAAH Warned & Unwarned
 Statistical model for effects threshold
 Population Averaged Model
 Audiometric Failures
 Audiometric and Conditional Failures
 Dose Response Curves
Outline continued
 Exposure Assessment Comparisons
 Threshold Estimates from BOP Study
 Fitting Performance
 Damage Risk Criteria Implications
 MilStd 1474D: 177 dB Limit
 LAeq8hr: 85 dBA Limit
 AHAAH: 500 Auditory Hazard Unit (AHU)
limit
MilStd 1474D Free-Field Exposure
Mil-Std 1474D
5 meter BOP Study
174
176
178
180
182
184
186
177 dB Threshold Limit
200
190
185
180
ho
ts
100
ro
fS
175
be
50
170
190
185
Peak E
180
xposur
e
175
Level (
dB)
25
12
6
170
Nu
m
(dB
Mil-Std 1474D
)
195
Mil-Std 1474D
1 meter BOP Study
Modified muff
Mil-Std 1474D
3 meter BOP Study
Modified muff
170
175
180
185
190
190
195
177 dB Threshold Limit
175.5
176.0
176.5
177.0
177.5
178.0
180
177 dB Threshold Limit
200
200
B)
195
(d
Mil-Std 1474D
Sh
ots
100
180
er
50
100
175
of
175
fS
180
185
ho
ts
185
190
Level (d
be
185
180
Peak E
xposure
170
B)
Mil-Std 1474D
5 meter BOP Study
Modified muff
174
176
178
180
190
195
200
177 dB Threshold Limit
200
195
190
185
180
ho
ts
100
175
50
170
190
185
Peak E
180
xposure
175
Level (d
B)
25
12
6
170
Nu
m
190
er
of
S
xposure
175
Nu
mb
180
50
170
Nu
185
Peak E
25
12
6
B)
190
mb
170
ro
190
(d
Mil-Std 1474D
(dB)
Mil-Std 1474D
195
175
Level (d
B)
25
12
6
170
LAeq8hr with 85 dB Threshold
1m BOP study
Modified muff
103.5
104.0
104.5
105.0
95
100
105
110
115
85 dBA Threshold Limit
Hazardous Exposure
115
nt Level (dBA)
8 hour Equivale
110
110
105
105
o ts
100
80
100
85
80
50
ure Le
vel
2
1
be
7
6
5
4
Exposu
Nu
m
3
3
2
re Leve
LAeq8hr with 85 dB Threshold
5 meter BOP Study
Modified muff
90
95
100
105
95
100
105
110
115
85 dBA Threshold Limit
Safe Exposure
Hazardous Exposure
115
110
105
100
95
90
100
Sh
ots
Expos
4
85
80
75
50
of
5
75
er
6
25
12
6
7
6
5
4
Exposu
Nu
mb
7
mb
er
50
90
Nu
75
of
Sh
85
95
ts
90
100
fS
ho
95
3
re Leve
2
l
25
12
6
1
ro
100
nt Level (dBA)
8 hour Equivale
)
115
nt Level (dBA
8 hour Equivale
LAeq8hr with 85 dB Threshold
3 meter BOP Study
Modified muff
90
95
100
105
110
100
105
110
115
85 dBA Threshold Limit
Hazardous Exposure
l
25
12
6
1
Warned AHAAH Analysis
1 meter BOP study
Modified muff
Warned AHAAH Analysis
3 meter BOP study
Modified muff
0
2000
4000
6000
8000
500 AHU Threshold Limit
Safe Exposure
Hazardous Exposure
0
1000
2000
3000
4000
500 AHU Threshold Limit
Safe Exposure
Hazardous Exposure
8000
25
190
12
6
185
180
175
185
Peak E
170
Warned AHAAH Analysis
5 meter BOP study
Modified muff
0
1000
2000
3000
4000
AHAAH 500 ARU Threshold
Safe Exposure
Hazardous Exposure
8000
6000
4000
ts
100
fS
ho
2000
50
0
190
185
Peak E
180
xposure
175
Level (d
B)
25
12
6
170
180
xposure
Peak Exposure Level (dB)
ro
190
50
0
Nu
mb
e
0
100
2000
Nu
mb
50
Number of Shots
100
2000
4000
er
of
Sh
ots
rd Units (AHU)
4000
6000
Auditory Haza
6000
rd Units (AHU)
Auditory Haza
Auditory Hazard
Units (AHU)
8000
175
Level (d
B)
25
12
6
170
Statistical Analysis of BOP Data
 Obtained the waveforms from Data Archive from USAARLMRMC and USARL – HRED
 MILSTD 1474D – B duration (also computed A & C durations)
 LAeq8hr – Protected and Unprotected
 AHAAH model – Protected Warned and Unwarned
 Checked against Chan et al. 2001, Ahroon & Patterson 2005,
Price (2005), Jokel (2007)
 Obtained the injury data from USAARL-MRMC
 Checked the injury data against 1999 Contractor report
DAMD17-96-6007
Statistical Analysis of BOP Data
 Applied a General Estimating Equations to
evaluate the Population Averaged effects using
xtgee in Stata.
fˆ 
1

1 e
 ˆ0  ˆ1 xij

 Represents the response pattern of the population as a whole
 Makes no assumptions regarding propagation of failure
through to other exposure levels
 Tells us nothing about the chances of an individual subject
failing within the exposure.
 Tells us about the chance of having a failure in the
population.
Mil STD 1474 D
MIL STD 1474D
Audiometric Failure
Audiometric or Conditional Failure
0.6
185 dB
150
160
170
180
190
200
210
0
0.05
0
0.05
0.2
0.2
0.4
193 dB
0.4
0.6
Failure Rate
0.8
0.8
1.0
1.0
MIL STD 1474D
150
160
170
95% confidence limits
180
190
200
dB
dB
GEE population-average
95% confidence limits
GEE population-average
210
LAeq8hr Unprotected Levels
Audiometric Failure
Audiometric or Conditional Failure
0.8
0.6
115 dB
0.2
100
105
110
115
120
125
130
135
140
0
0.05
0
0.05
0.2
0.4
124 dB
0.4
0.6
Failure Rate
0.8
1.0
LAeq_8hr: Unprotected
1.0
LAeq_8hr: Unprotected
100
105
110
115
dB
95% confidence limits
120
125
130
135
dB
GEE population-average
95% confidence limits
GEE population-average
140
LAeq8hr Protected Levels
Audiometric Failure
Audiometric or Conditional Failure
0.8
0.6
101 dB
0.2
80
85
90
95
100
105
110
115
120
0
0.05
0
0.05
0.2
0.4
109 dB
0.4
0.6
Failure Rate
0.8
1.0
LAeq_8hr: Protected
1.0
LAeq_8hr: Protected
80
85
90
95
dB
95% confidence limits
100
105
110
115
dB
GEE population-average
95% confidence limits
GEE population-average
120
AHAAH Unwarned Model
Audiometric Failure
Audiometric or Conditional Failure
0.8
0.6
3053 AHU
0.2
0
5000
10000
15000
20000
25000
30000
0
0.05
0
0.05
0.2
0.4
10109 AHU
0.4
0.6
Failure Rate
0.8
1.0
AHAAH: Unwarned
1.0
AHAAH: Unwarned
0
5000
10000
AHU
95% confidence limits
15000
20000
25000
AHU
GEE population-average
95% confidence limits
GEE population-average
30000
AHAAH Warned Model
Audiometric Failure
Audiometric or Conditional Failure
0.8
0.6
718 AHU
0.2
0
1000
2000
3000
4000
5000
6000
7000
8000
0
0.05
0
0.05
0.2
0.4
2480 AHU
0.4
0.6
Failure Rate
0.8
1.0
AHAAH: Warned
1.0
AHAAH: Warned
0
1000
2000
3000
AHU
95% confidence limits
4000
5000
6000
7000
AHU
GEE population-average
95% confidence limits
GEE population-average
8000
5% Failure Thresholds L(95,95)
Damage Risk
Criterion
Audiometric
Failures
Audiometric &
Conditional Failures
AHAAH Warned
2480 AHU
718 AHU
AHAAH Unwarned
10109 AHU
3053 AHU
LAeq8hr Unprotected
124 dB
115 dB
LAeq8hr Protected
109 dB
101 dB
MilStd 1474D
193 dB
185 dB
Five Exposure Assessments Compared
Damage Risk
Criterion
Audiometric
Audiometric &
Failures
Conditional Failures
LAeq8hr Unprotected
273.73
630.26
MilStd 1474 D
282.01
636.25
AHAAH Unwarned
304.51
650.85
LAeq8hr Protected
305.80
650.05
AHAAH Warned
307.13
653.99
QIC: Lower value indicates a better fit
QIC = Quasi Likelihood under the independence model Information Criterion
Mil-Std Observations
 Mil-Std 1474D
 L(95,95) with No Presumed Auditory Failures
 Chan : L(95,95) = 193 dB
 NIOSH : L(95,95) = 193 dB
 Chan’s analysis: Presumed Auditory Failures
 Add 9 dB for threshold of L(95,95) = 186 dB
 NIOSH analysis (Auditory & Conditional Failures)
 L(95,95) = 185 dB.
 Add 8 dB for Population Average threshold for
the L(95,95) lower confidence bound.
LAeq8hr Observations
 LAeq8hr Protected versus Unprotected
 French Weapon Noise Criteria:
 LAeq8hr < 85 dB Unprotected
 Chan’s analysis without presumed failures
 LAeq8hr < 100 dB Protected (assumed 15 dB for protectors)
 Unprotected limit 124 dB without presumed failures
 NIOSH analysis without presumed failures
 14 dB HPD effect for Protection
 Unprotected limit: 124 dB Audiometric Failures
 Unprotected limit: 115 dB Aud. & Cond. Failures
 Protected limit: 101 dB Aud. & Cond. Failures
AHAAH Observations
 NIOSH Analysis L(95,95) Audiometric
failures (no presumed failures)
 Unwarned Threshold = 10109 AHU
 Warned Threshold = 2480 AHU
 NIOSH Analysis L(95,95) Audiometric and
Conditional Failures (no presumed failures)
 Unwarned Threshold = 3053 AHU
 Warned Threshold = 718 AHU
 AHAAH Model proposes a 500 AHU Limit
which is more conservative than the data
suggest
Concerns for AHAAH Model
 Predictions of Hazard at Levels 3 & 4 not
really tested in BOP study.
 Experiments can be designed to test this.
LAeq8hr with 85 dB Threshold
1m BOP study
Modified muff
0
2000
4000
6000
8000
500 AHU Threshold Limit
Safe Exposure
Hazardous Exposure
115
25
95
90
fS
ho
ts
100
85
80
75
50
7
6
12
6
180
175
5
4
Exposu
re
170
Peak Exposure Level (dB)
Mil-Std 1474D
1 meter BOP Study
Modified muff
170
175
180
185
190
190
195
177 dB Threshold Limit
200
195
190
185
180
fS
ho
ts
100
175
50
170
190
185
180
Peak E
xposure
ro
185
Nu
mb
e
190
100
B)
0
105
175
Level (d
B)
25
12
6
170
ro
nt Level (dBA)
50
Number of Shots
100
2000
110
8 hour Equivale
6000
(d
Mil-Std 1474D
Auditory Hazard
Units (AHU)
8000
4000
90
95
100
105
110
100
105
110
115
85 dBA Threshold Limit
Hazardous Exposure
Nu
mb
e
Warned AHAAH Analysis
1 meter BOP study
Modified muff
3
Level
2
25
12
6
1
Concerns for AHAAH Model
 Justification for 500 AHU as a threshold limit
 Warned limit
 718 or 2480 AHU – Population Average, L(95, 95)
 Unwarned Limit
 3053 or 10109 AHU – Population Average, L(95, 95)
 Validation of the Warned/Unwarned middle ear
 No consideration given for adaptation/fatigue
 Model turns Warned condition ON but not OFF
Questions?
William Murphy
4676 Columbia Parkway, MS C-27
Cincinnati, OH 45226-1998
[email protected]
513-533-8125