An estimate (with uncertainty spanning perhaps an order of magnitude) of daily exposure to the human population (including sensitive subgroups) that is likely to be without appreciable risk of deleterious effects during a lifetime.
Source:
PAC, 2001, 73, 993. 'Risk assessment for occupational exposure to chemicals. A review of current methodology (IUPAC Technical Report)' on page 1023 (https://doi.org/10.1351/pac200173060993)