Editing Threshold limit value (section)

{{Short description|Upper limit on the acceptable exposure concentration of a hazardous substance in the workplace}}
The '''threshold limit value''' ('''TLV''') is a level of occupational exposure to a [[hazardous substance]] where it is believed that nearly all healthy workers can repeatedly experience at or below this level of exposure without [[Adverse effect|adverse effects]]. Strictly speaking, TLV is a reserved term of the [[American Conference of Governmental Industrial Hygienists]] (ACGIH), who determines and publishes TLVs annually. TLVs issued by the ACGIH are the most widely accepted occupational exposure limits both in the United States and most other countries.<ref>{{cite book|last1=Stellman|first1=Jeanne Mager Stellman|title=Encyclopedia of Occupational Health & Safety|publisher=International Labour Organization|url=http://www.iloencyclopaedia.org/part-iv-66769/occupational-hygiene-47504/48-30-occupational-hygiene/occupational-exposure-limits}}</ref>  However, it is sometimes loosely used to refer to other similar concepts used in [[occupational safety and health|occupational health]] and [[toxicology]], such as [[acceptable daily intake]] (ADI) and [[tolerable daily intake]] (TDI). Concepts such as TLV, ADI, and TDI can be compared to the [[no-observed-adverse-effect level]] (NOAEL) in [[animal testing]], but whereas a NOAEL can be established [[experiment]]ally during a short period, TLV, ADI, and TDI apply to human beings over a lifetime and thus are harder to test empirically and are usually set at lower levels. TLVs, along with biological exposure indices (BEIs), are published annually by the ACGIH.

The TLV is an estimate based on the known [[toxicity]] in [[Human|humans]] or [[Animal|animals]] of a given chemical substance, and the reliability and accuracy of the latest sampling and [[Analytical method|analytical methods]]. TLVs do not take into account financial or technical feasibility for application in the workplace, instead solely focusing on health based recommendations to prevent adverse health effects.<ref>{{Cite web |title=Documentation and Data |url=https://www.acgih.org/science/tlv-bei-guidelines/documentation-publications-and-data/ |access-date=2024-03-30 |website=ACGIH |language=en-US}}</ref> It is also not a static value, since new research can often modify the [[risk assessment]] of substances, and new [[laboratory]] or [[instrumental analysis]] methods can improve analytical [[Detection limit|detection limits]]. 

The TLV is a recommendation by ACGIH, with only a guideline status. As such, it should not be confused with exposure limits having a regulatory status, like those published and enforced by the [[Occupational Safety and Health Administration]](OSHA). However, many OSHA exposure limits are not considered by the [[industrial hygiene]] community to be sufficiently protective levels since the toxicological basis for most limits have not been updated since the 1960s. OSHA acknowledges this and recommends supplementing regulatory standards with alternative updated and stricter standards, "even when the exposure levels are in compliance with the relevant PELs", while specifically mentioning the TLV as one such standard.<ref name=":0">{{Cite web |year=2014 |title=Permissible Exposure Limits – Annotated Tables |url=https://www.osha.gov/annotated-pels |access-date=March 30, 2024 |website=osha.gov }}</ref>