biological tolerance values for working materials (Biologische Arbeitsstoff Toleranz Werte (BAT))

https://dx.doi.org/10.1351/goldbook.BT06903
The maximum permissible quantity of a chemical compound or its metabolites, or any deviation from the norm of biological parameters induced by those substances in exposed humans.
Source:
PAC, 2001, 73, 993 (Risk assessment for occupational exposure to chemicals. A review of current methodology (IUPAC Technical Report)) on page 1022