The Occupational Health and Safety Regulation provides that, except as otherwise determined by WorkSafeBC, an employer must ensure no worker is exposed to a substance exceeding the Threshold Limit Values (TLVs) prescribed by the American Conference of Governmental Industrial Hygienists (ACGIH).

Twice a year, the ACGIH publishes a list of substances for which they have set new or revised TLVs. When WorkSafeBC adopts the new or revised ACGIH TLVs as regulatory exposure limits for chemical substances, these exposure limits are referred to as B.C. Exposure Limits (ELs).

An EL is the maximum allowed airborne concentration for a chemical substance for which it is believed that nearly all workers may be exposed over a working lifetime and experience no adverse health effects. ELs may be set out as an 8-hour time-weighted average concentration, a 15-minute short-term exposure limit, or a ceiling limit.

When the ACGIH publishes its biannual list, WorkSafeBC identifies the substances with new or revised TLVs and adds these substances (together with their existing B.C. ELs) to the Table of Exposure Limits for Excluded Substances in Prevention Manual Item OHS Policy R5.48-1. Until our Board of Directors makes a decision on whether to adopt the changes, the existing ELs for these substances continue to be in effect in B.C.

Before bringing the new or revised ACGIH TLVs to the Board of Directors for decision, WorkSafeBC’s Exposure Limit Review Committee reviews the relevant data on health effects and the availability of validated sampling methods for these substances, and consults with stakeholders.

The ACGIH published a batch of new or revised TLVs for 2024 in June of this year. The following substances with new or revised TLVs for 2024 have been added to the Table of Exposure Limits for Excluded Substances in Prevention Manual Item OHS Policy R5.48-1:

• Acrolein
• Desflurane
• Endotoxins, Inhalable
• Imidacloprid, Inhalable
• Isopropyl ether
• Propionitrile
• Trimetacresyl phosphate, Inhalable fraction and vapour
• Trimethylolpropane, Inhalable fraction and vapour
• Triparacresyl phosphate, Inhalable fraction and vapour

All B.C. ELs can be found in the updated Table of Exposure Limits for Chemical and Biological Substances.