Tlv for Physical Agents

8/3/2019 Tlv for Physical Agents

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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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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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20

22

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26

28

30

32

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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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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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30

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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

Documents

Tlv for Physical Agents