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Threshold Limit Valuesfor Physical Agents
(TLV-PA) Committee
Thomas E. Bernard
Chair, TLV
-PA CommitteeUniversity of South Florida
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Updates for 2006 RF&MW: Note on Ultra-wide bandwidth
Sub-RF Magnetic Fields: Note on ContactCurrents
Sub-RF Static Fields: Note on ContactCurrents
Noise: Note on Ototoxicity
Note on carcinogenicity
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NICs for 2006
Visible and Near Infrared Radiation
Heat Stress and Strain
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Visible and Near Infrared
Radiation
Thermal Effects Hazard Function
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Overestimated Risk
The risk of thermal effects between380 and 500 nm was higher than
necessary.
The hazard function [R()] in this
range was reduced accordingly.
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Graphically Speaking
0.0010
0.0100
0.1000
1.0000
10.0000
100.0000
200 400 600 800 1000 1200Wave Length [nm]
Hazard
Functio
R(lamda) - New
R(lamda) - Old
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Heat Stress and Strain
Major Changes
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Action Limit
Action Limit!Replaces the Unacclimatized TLV
Work below the Action Limit is
presumptively low stress for any
healthy worker.
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100 200 300 400 500 600
Metabolic Rate [W]
WBGT
eff[C]
TLV for Heat Stress
TLV
Action Limit
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Accounting for Clothing
Clothing makes an environmentalcondition seem worse. It reduces both
evaporative and dry heat exchange.
Intuitively, there should be a factor that
adjusts the environmental measures to an
equivalent condition in work clothes.
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Changed and Expanded for2006
Clothing Adjustment Factors [C-WBGT]Previous 2006
Work Clothes (Baseline) 0 0
Cloth Coveralls 3.5 0Double Layer Cloth Clothing 5 3
SMS Coveralls --- 0.5
Polyolefin Coveralls --- 1
Limited-use Vapor-Barrier Coveralls --- 11
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Environment Plus Clothing
Effective WBGT (WBGTeff) =
Measured WBGT
+ Clothing Adjustment Factor (CAF)
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Heat Stress and Strain
TLV
Process Flow
(See TLV Decision Flow Chart)
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Screening
YES
YES
NO
NO
Clothing Adjustment Factors
Available?
Are Screening Criteria for Action
Limit Exceeded? Low RiskContinue Work
Monitor Conditions
YES
NOAre Screening Criteria for TLV
Exceeded?
Continue Work
Maintain Controls
Monitor Conditions
Implement General
Controls
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Table Changes for 2006
Assigned metabolic rate in each categoryhas a lower value.
!Better reflects work physiology
principles and other standards.!Means higher WBGT values.
Allocation of Work/Rest described as arange of % work in the cycle.
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Metabolic Rate by Category
Reference Metabolic Rate [W]Previous 2006
Rest (Baseline) 115 115
Light 230 180
Moderate 350 300
Heavy 465 415
Very Heavy 580 520
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Screening Action Limit
%Work L M H VH75 to 100 28.1 25.0 -- --50 to 75 28.7 26.0 24.2 --25 to 50 29.3 27.2 25.7 24.60 to 25 30.0 28.8 27.8 27.0
Note:TLVs and BEIs Book rounds
these numbers to the nearest 0.5 C-WBGT
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Screening TLV
%Work
L
M
H
VH
75 to 100 30.8 28.2 -- --50 to 75 31.2 29.0 27.6 --25 to 50 31.8 30.1 28.8 27.90 to 25 32.3 31.3 30.5 29.8Note:TLVs and BEIs Book rounds
these numbers to the nearest 0.5 C-WBGT
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Detailed Analysis
YES
YES
NO
NO
Are Data Available for
Detailed Analysis?
Action Limit Exceeded?
Continue Work
Maintain Controls
Monitor Conditions
Implement General
Controls
YES
NOTLVExceeded?
Low RiskContinue Work
Monitor Conditions
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Task Analysis
Breakdown by Location
Breakdown by Homogeneous Activities
Time Assigned for Each Location/
Activity
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Potential Error
Broad Range Over-Estimation
Metabolic Rate Categories
Light! 180 W! sitting, standing, light hand/arm work
Moderate!
300 W!walking, moderate lifting
Heavy! 415 W
! heavy materials handlingVery Heavy
! 520 W
! pick and shovel work
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Total Metabolic Rate (M) = B + P + W + D + C
ISO Estimation Method
Earlier Methods in NIOSH Criteria Document
Components of Metabolic Rate
!Basal (Base) Metabolism (B)
!Posture (P)
!Type of Work (W)
!Walking (D)
!Climbing (C)
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WBGTmeasured
+ Clothing Adjustment
WBGTeff
Clothing Adjustments toWBGT
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WBGTeff1 x t1 + + WBGTeffn x tn
t1 + + tn
TWA-WBGTeff =
M1 x t1 + + Mn x tn
t1 + + tn
TWA-M =
Over one to two hour time period.
Time-Weighted Average
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Where is the job?
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100 200 300 400 500 600
Metabolic Rate [W]
WBG
Teff[C]
TLV
Action Limit
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Job Risk Factors
Traditional!Environment
!Work Demands
!Clothing Requirements
Plus Time
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Empirical Time Limits
US Navy PHEL Charts
30
35
40
45
50
55
WBGT(C)
0 1 2 3 4 5 6
Exposure Time (h)
260 W200 W
155 W
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Rational Time Limits
ISO 7933 (2004)
PHS: Predicted Heat Strain
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Heat Strain Monitoring
When working above the TLV
orunder conditions when a detailed
analysis cannot be performed.
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Heat Strain Monitoring
YES
NO
Perform Heat Strain
(Physiological) Monitoring
Excessive Heat Strain
Based on Monitoring?
Continue Work
Maintain Controls
Monitor Conditions
Implement General
Controls
YES
NOTLVExceeded?
Implement Job-Specific
Controls
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Body Core Temperature
Acceptable Limit!Acclimatized, Healthy, Experienced: 38.5 C
!Unacclimatized and Unselected: 38 C
Oral Temperature
!No recent drinks/food, mouth closed
!Core is Oral plus 0.5 C
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Heart Rate
Sustained heart rate greater than(180 - Age)
Recovery heart rate greater than
120 bpm at one minute
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Symptoms
Sudden or severe fatigue, nausea,dizziness, or lightheadedness.
MEDICAL EMERGENCY
Disorientation, irritability, malaise,chills, unconscious.
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Patterns of Strain
No pattern of excessive strain
Pattern of excessive strain
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Under Study*Ergonomics
!Hand-Arm Vibration
!Localized Fatigue
Lasers
Nonionizing Radiation
!Light and Near Infrared
!Radiofrequency and microwave radiation
!Static Magnetic Fields
!Ultraviolet Radiation
Cold Stress*Refer to the ACGIHwebsite for the up-to-date list. This list isevergreen and can change during the year.
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Thank You
Thanks to
the Committee members
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