Occupational exposure limits (OELs) are maximum acceptable air concentrations that are used as reference parameters for the protection of workers from overexposure to chemical substances by inhalation. Thus, OEL value represents repeated exposure concentrations during an entire working life which would not cause any significant adverse effects on the health of exposed persons.
For the purposes of calculation, health-based OELs are derived by dividing a toxicological point of departure (PoD) for the critical effect by various uncertainty or adjustment factors to extrapolate to the “true” no-effect level in the worker population of interest.
The point of departure (PoD) used for the OEL calculation refers to the dose or concentration extracted from the effects observed on preclinical or clinical studies which are used for extrapolation to the OEL. PoD could represent a no-effect level (e.g., a no-observed-adverseeffect level [NOAEL] or benchmark dose [BMD]) or an effect level (e.g., a lowest-observedadverse-effect-level [LOAEL]). Data from preclinical studies by repeat exposure which provides information on critical effects should be preferably selected for OEL calculation.
Furthermore, Uncertainty factors (UF) are used routinely in establishing OELs, to account for uncertainty in extrapolating from the selected PoD to a general workers population. Among the uncertainty factors generally used are the interspecies and intraspecies correction factors, the short term to long term adjustment factor, the pharmacokinetic factor (which accounts for differences on bioavailability) or the data factor which covers the lack of scientific data.
However, despite their wide application, the rationale for the use of uncertainty factors and the recommended default values differ by organization. In any case, the application of UFs is intended to result in an OEL that is protective of all adverse chemical-related effects.
OEL value, together other toxicological and pharmacological endpoints such us the substance potency, its adverse effects or the CMR (carcinogenicity, mutagenicity and reproduction toxicity) profile are used for the chemical categorization of the substance. Chemical categorization or
control banding together with the engineering and operational controls and personal protective equipment represents useful tools to assure the health and safety of workers in the pharmaceutical industry.
Thus, an accurate OEL calculation is the starting point to define the toxicity profile of a substance and to propose an integral strategy to maintain the safety of the personnel in the pharmaceutical industry.
In Dalia Global, ERT toxicologists’ are experts in OELs’s calculation. For more information…