ACGIH endnote for "Exposure by all routes should be carefully controlled to levels as low as possible". WorkSafeBC considers substances with this notation to be highly toxic, and which have not been assigned an exposure limit.
OHSR 5.57 (Designated Substances) - Replace, if practicable, with another substance that reduces the risk to workers and implement an EXPOSURE CONTROL PLAN, as described in OHSR 5.54, to maintain worker exposure as low as reasonably achievable below the applicable B.C. exposure limit.
ACGIH; WorkSafeBC Guidelines G5.57 (Designated Substances)