OCCUPATIONAL BIOMONITORING LEVEL (OBL) INTRODUCTION

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this will cause confusion amongst users of the BMGV such as exposure assessors. For this reason, initial efforts have already been made at the European level within the framework of the HBM4EU project to harmonize and agree upon so-called human biomonitoring guidance values for workers (HBMGVWorkers) and the general population (HBM-GVGenPop) (Apel et al., 2020). Further guidance in the occupational field may help in deriving and using health-based human biomarker values (BMGV*, BLV*, DNELbiomarker*, HBM-GVWorker etc.). In the following guidance, we use the neutral and overarching term Occupational Biomonitoring Level (OBL*) in accordance with Occupational Exposure Limits (OEL*) or Occupational Exposure Limit Values (OELV*) which are used for air monitoring.

Occupational Biomonitoring Level (OBL) introduction

OBL* values are often derived either as an equivalent to the (external) OEL* value (TLV®*, MAK*, worker-DNEL*) or based on a direct relationship between the biomarker and a related health effect. The ideal approach to setting an OBL* is to establish a direct association between biomarker level and a critical health effect. This is possible only in cases in which there are reliable research data on the correlations between biomarker levels and negative health effects. If this is not possible, then derivation of internal concentrations associated with an external dose or an external exposure limit value (OEL* value) is conducted. Routine biomonitoring surveillance will lead to more robust health effect correlation studies. Toxicokinetic knowledge together with measured/modelled data is needed to elucidate correlations between external exposure and biomarker levels. This correlation is key to establishing biomarker levels that correspond to OELs*. Establishing biomarker levels corresponding to external exposure levels is also known as forward dosimetry. Different forward dosimetry approaches have been applied to set health-based guidance values also for the general population. These may correspond to general population limit values for external exposure (TDI*, ADI*, RfD* etc) and include biomonitoring equivalents (BE*), described by (Hayes and Aylward, 2009),and the human biomonitoring values (HBMI and HBM-II values) described by the German Human Biomonitoring Commission ((German HBM Commission, 1996; 2007); (Angerer et al., 2011)). Apel et al. (2017) have built on these two approaches (for general population) and on the ANSES approach (for worker limit value setting), and have established HBM-GVs of the current European project HBM4EU* (Apel et al., 2020). Different definitions for biological assessment values, here called OBLs*, are used interchangeably as well as various terms such as biological limit values or BLV* (previously by SCOEL*, ANSES*), biological exposure indices or BEI® (USA ACGIH* committee), BAT* values (DFG in Germany, SUVA* in Switzerland). Under REACH*, Biomarker DNELs* or “DNELbiomarker*” are “Derived No Effect Levels” expressed as internal concentrations” (normally in urine or blood). DNELs are concentration levels below which a substance does not adversely affect human health (see: (ECHA* Guidance, 2012); (Boogaard et al., 2011)).

OBLs* are only derived when there are enough toxicological and kinetic data for a robust assessment see chapter 3.2. In the absence of an OBL*, alternatively a Provisional OBL (POBL*) (see chapter 3.3), a Reference OBL (ROBL*), or Technical achievable (TOBL*) can be derived (see chapter 3.4). ROBLs*, are not based on toxicological evaluation but are statistically derived values which are usually set as 95th percentile of the reference population levels (i.e., population not specifically exposed, not including populations exposed occupationally or via local industrial contamination). Once established, these can be used to distinguish highly exposed populations from those with typical background levels in the general population. Although these population reference values do not inform on health risks, but they may inform on potential occupational exposure and they need to be considered when deriving limit values for occupationally exposed populations (see chapter 3.4 and 5.5). Currently, on a global level, different approaches to derive occupational biomonitoring assessment values or kinds of OBLs* are described, but no detailed step-by-step guidance exists and only a few examples are given. A harmonized approach in deriving and applying OBLs* can lead to improved worker health and to increased availability and plausibility of biomonitoring assessment values. Because of the different functions of OBLs* every derivation which is dose dependent (OBL* & POBL*) is named in this guidance mainly health-based, because they can indicate a health risk. For the more risk based derivations for non-treshold substances we used health-risk based values. In contrast ROBL* and TOBL* are not health based and are set primary under technical considerations.

OCCUPATIONAL BIOMONITORING GUIDANCE DOCUMENT © OECD 2022