Threshold Limit Values (TLVs)

TLV® Definition

concentrations … which it is

airborne concentrations … which it is

believed that nearly all workers may be

repeatedly exposed … without adverse

health effects believed that nearly all workers may be

repeatedly exposed … without adverse

TLVs• How to apply…• Trained professionals• Guides and recommendations• Not for community air pollution• Not for proving disease

TLVs

• Why TLVs?

• OSHA Standards

• NIOSH RELS

• Other Sources

PEL

Concentrations that healthy individuals can normally tolerate for eight hours a day, five days a week without harmful effects

TLVs

• OSHA Standards. Permissible Exposure Limits (PELS)

• Established in 1970– 1910.1001 Z Tables

• Updated in 1989 but not since.

OSHA PELS

Chemical PEL TLV (2007)

• Acetylaldehyde 200 ppm 25 ppm

• Acetic Acid 10 ppm 10 ppm

• Acetone 1000 ppm 500 ppm

TLV

Dose

Res

pons

e

LD50

ED

TWA

Threshold

NIOSH RELS

Chemical RELs TLV (2007)

• Acetylaldehyde 18 ppm 25 ppm

• Acetic Acid 10 ppm 10 ppm

• Acetone 250 ppm 500 ppm

German MAKs

In the work-place environment MAK values (maximum allowable workplace concentrations) haven been fixed as time-integrated averages relatively early in order to avoid adverse health effects to workers exposed to air pollution during their working shift.

GERMAN MAKs

Acetaldehyde 5 mg/m3

Acetanilide 6 mg/m3

Acetic acid 15mg.m3

Acetic anhydride 10mg/m3

Acetone 200 mg/m3

TLVs

Data points

Extrapolation of Data

Extra

polat

ed

Activity

Activity

Given: 10 mg/kg LD50 Rats for Chemical X

Using Linear scaling: The LD50 for a 2 kg rate would be 20 mg/kg

For a 10 kg dog would be 100 mg

What would the LD50 for a 50 kg person be?.

Non-linear response

TLVs

• Basis:– Benzene: Leukemia– Beryllium: Lung Cancer– Toluene: Visual impairment, female reprod.

CH3

TLVs

• Other Chemicals based:

• Animal Studies

• Epidemiology Study– Ames Study

TLVs

Because of wide variations in individual susceptibility, exposure of an individual at, or even below, the TLV may result in annoyance, aggravation of a pre-existing condition, or occasionally even physiological damage.

TLVsSubstance [CAS No.] (Documentation No.) TWA STEL NOTATIONToluene 20 ppm - A4 BEI

2007

Time Weighted AverageNot classified as Carcinogen

TLV

TWA – Time Weighted Average

TWA = (C1T1) + (CnTn)Total Time

TLV - STELS• Short Term Exposure Limits

– 15 minutes– Never exceeded at any time– STEL Is the level one can be exposed to

without • Irritation, chronic effects or dose related toxic

effects

TLV - Ceiling

• Not exceeded during any time of exposure

• Sample to ensure they can not be exceeded.

Calculate TWAs

Activity:

TWA

• Sample 1. 100 mg/m3 100 minutes

• Sample 2. 160 mg/m3 150 minutes

• Sample 3. 200 mg/m3 150 minutes

Extended Work Hours

• Do TLVs need to be adjusted?

• Why and how?

• What type work would need it?

Extended Work Hours

• Half-Life:

• Toluene: 8 hoursD

ose

Time8 Hours

½ Dose

Extended Work Hours

Day 1 Day 2 Day 3 Day 4 Day 5

BEI

> 8 hrs

Bui

ld u

p

Purge

> BEI

Biological Exposure Indices

• BEIs To control Exposure

• Indicators

• Various fluids are monitored

• Various Times (Critical)– What are times based on?

Biomarkers

XYLENE

BEI: Methylhippuric acid in urine (Methip)Specimen collection: A post-shift urine sample (20 mL) obtained after at least two consecutive days of exposure.  

Physical Agents• Noise

• RF

• Lasers

• Vibration

• Ultraviolet Radiation

• IR

• Heat/Cold

TLV – Physical Agents

TLV Questions?