1. Origin of the Threshold Limit
Value (TLV®) Committee of
the ACGIH
Elizabeth Weisburger

2. History, a Short Perspective
♣1941- Established TLV® Committee for
chemical substances
♣1967 – Established TLV® Committee for
physical agents
♣1983 – Established Biological Exposure
Indices (BEI®) Committee

3. Overview
♣TLV® – CS Committee has ~20 members
and ~3 member-candidates, who
volunteer time towards developing
scientific guidelines and publications
♣ Primary goal is to serve the scientific needs
of industrial hygienists
♣ Committee expenses (travel) are supported
by ACGIH®
♣ Time is donated by the members

4. Chemical Substances Committee
♣Membership from academia, government,
unions, industry
♣Membership represents four key
disciplines:
♣ Industrial Hygiene
♣ Toxicology
♣ Occupational Medicine
♣ Occupational Epidemiology

5. Chemical Substances TLV
Committee Subcommittees
♣HOC = Hydrogen, Oxygen, Carbon
♣D&I = Dusts and Inorganics
♣MISCO = Nitrogen, Sulfur, Phosphorous,
Halo

6. Carcinogen Designations
♣A1- - Recognized Human Carcinogen
♣A2 -- Suspect Human Carcinogen
♣A3 – Animal Carcinogen of Unknown
Relevance to Humans
♣A4 – Not classified as a Human
Carcinogen (Negative Animal Test)
♣A5 – Not Suspected as a Human
Carcinogen

7. ACGIH 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

8. ACGIH Basis of TLVs / BEIs
Scientific Literature
Published / Peer Reviewed Science (Principal Source)
Review Articles (Secondary)
Unpublished Science (Secondary)
Before Use: Owner must provide ACGIH permission
to use and cite the report, AND release the report to a
third party
Consideration of TLVs are not deferred pending
completion of on-going or planned research
Not a Review of all available literature
Emphasis on peer-reviewed literature
Emphasis on literature pertinent to the issue

9. ACGIH Core TLV Principles
♣ Focus on airborne exposures in occupational
settings
♣ Utilize the “threshold” concept
♣ Primary users are industrial hygienists
♣ Goal is toward proteciton of “nearly all” workers
♣ TECHNICAL, ECONOMIC AND ANALYTICAL
FEASIBILITY ARE NOT CONSIDERED

10. ACGIH TLV Development
♣ Prefer human over ♣ Not concerned with
animal data levels of risk
♣ Use uncertainty ♣ Look for the “worst
factors, if necessary case” health endpoint
(but no “rules”) ♣ Always select an
♣ Look for threshold of exposure level
effects ♣ Explain the reasons
♣ Consider irritation an for our
important health recommendations
endpoint

11. 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