Slide 1

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations


Slide 2

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations


Slide 3

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations


Slide 4

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations


Slide 5

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations


Slide 6

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations


Slide 7

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations


Slide 8

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations


Slide 9

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations


Slide 10

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations


Slide 11

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations


Slide 12

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations


Slide 13

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations


Slide 14

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations


Slide 15

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations


Slide 16

Chemical Substances
TLV® Committee
Lisa Brosseau, ScD, CIH
Associate Professor
University of Minnesota
Chair, TLV®-CS Committee

ACGIH® Committees
• Committees consist of members, who
volunteer time toward developing
scientific guidelines and publications
– Primary goal is to serve the scientific
needs of occupational hygienists
– Committee expenses (travel) are
supported by ACGIH®
– Time is donated by the members

A Short Historical
Perspective
• 1941 TLV® Committee Created
– Committee of Technical Standards creates
Subcommittee on Threshold Limits
(becomes independent committee in 1944)

• 1946 List Published
– First published list of “Maximum Allowable
Concentrations” (MACs) for 150 chemical
substances (renamed Threshold Limit
Values in 1948)

History
• 1955 Written Documentation
– TLV® Committee begins to write
Documentation for each TLV® (207
completed by 1958)
– Published 1st edition in 1962 (257
substances)

History
• Important Additions and Changes
–
–
–
–

1961 - Skin Notation
1962 - Carcinogens Appendix
1963 - Excursion factors
1964 - Notice of Intended Changes
» 1968 - TLVs® for Physical Agents Committee

– 1972 - Cancer classifications defined
– 1980 - Operational guidelines & procedures
– 1981 - List of Substances & Issues Under Study

History
• More Changes
– 1983 - Established Biological Exposure
Indices (BEI®) Committee
– 1993 - Deleted STELS for many substances
– 1995 - CD-ROM
– 1998 - Reformatted TLV® Book to include
information on “TLV® Basis - Critical Effects”

Committee Structure
• Chair
– Recommendations from Committee & Staff; Board appoints

• Vice-Chair, Subcommittee Chairs, Members
– Recommended by Chair, appointed by Board

• Three Subcommittees, each with Chair
– Dusts & Inorganics (D&I)
– Hydrogen, Oxygen & Carbon Compounds (HOC)
– Miscellaneous Compounds (MISCO)

• Staff Support (Liaison, Clerical, Literature Searching)

Chemical Substance
Subcommittees
• Approximately 10 members on each
• Membership from academia, government,
unions, industry
• Membership represents four key
disciplines:
–
–
–
–

Industrial Hygiene
Toxicology
Occupational Medicine
Occupational Epidemiology

Other
Subcommittees
• Chemical Selection
– Recommendations to HOC, D&I, MISCO

• Membership
– Recruitment, screening, recommendations

• Notations
– Definitions, new proposals

• Communications
– Explaining our decisions

Board of
Directors

Committee
Structure

Staff
Chair of TLV®
Committee

Steering
Committee

Dust &
Inorganics
Subcommittee
(D&I)

Administrative
Subcommittees
(Membership,
Chemical Selection)

Hydrogen,
Miscellaneous
Oxygen, Carbon Compounds
Subcommittee
(HOC)

Subcommittee
(MISCO)

TLV® Development
Process
Draft
Doc.

Under
Study
List

Committee
Review
& Revision

External
Input
Committee
Review
& Revision

Committee
& Board
Approval

NIC

Adopted
Value

Committee
& Board
Approval

TLVs® Defined
• TLV® — more than just
“THE NUMBER”
• Documentation describes:
– Critical health effects
– Quality of the data relied upon and areas of
uncertainty
– Possible sensitive subgroups
– Type of TLV® (TWA, STEL, C) and reason for
selection
– Notations

Core TLV® Principles
• Focus on airborne exposures in
occupational settings
• Utilize the “threshold” concept
• Primary users are industrial hygienists
• Goal is toward protection of “nearly all”
workers

Technical, economic, and analytic
feasibility are NOT considered

The Essential Ingredients for
Developing TLVs®
Published / Peer Reviewed
Science
+
Dedicated Volunteerism
+
Professional Integrity
& Judgment

Warnings
• NOT to be used as an index of relative
toxicity
• NOT for estimating toxic potential of
continuous, uninterrupted exposures or
other extended work periods
• NOT as proof/disproof of existing disease
• NOT to evaluate or control air pollution
• NOT legal standards

Summary
• Prefer human over
animal data
• Use uncertainty factors,
if necessary (but no
“rules”)
• Look for threshold of
effects
• Consider irritation an
important health
endpoint

• Not concerned with
levels of risk
• Look for the “worst
case” health endpoint
• Always select an
exposure level
• Explain the reasons for
our recommendations