This is a presentation developed by the American Conference of Governmental Industrial Hygienists (ACGIH) for occupational health and safety professionals such as those present at APHA annual meetings. It provides an opportunity for those who are interested to learn about the development and intended use of ACGIH Chemical Substance Threshold Limit Values (TLVs) and to give feedback on TLVs and the process that creates them. TLVs are guidelines primarily for control of airborne exposures to workplace health hazards. They represent health-based scientific opinions. Economic and/or technical feasibility not taken into consideration. TLVs are primarily based on published, peer-reviewed scientific literature. This presentation will discuss

- criteria for inclusion of studies and for use of non-published material,

- the sections contained in TLV Documentation,

- general approaches to setting occupational exposure guidelines,

- sources of uncertainty,

- and TLV notations.

Participants will be given an opportunity to ask questions, express opinions and make suggestions as to how TLVs and the process of creating them could be more user friendly.