The concentration in air to which it is believed that most workers can be exposed daily without an adverse effect (i.e.
, effectively, the threshold between safe and dangerous concentrations). The values were established (and are revised annually) by the ACGIH
and are time-weighted concentrations (TWA
) for a 7- or 8-h workday and 40-h workweek, and thus are related to chronic effects. A short-term exposure limit (STEL
) is defined as a 15-min TWA
exposure, which should not be exceeded at any time during a workday even if the 8-h TWA
is within the TLV
PAC, 2001, 73, 993. 'Risk assessment for occupational exposure to chemicals. A review of current methodology (IUPAC Technical Report)' on page 1024 (https://doi.org/10.1351/pac200173060993)