Approaches for the setting of occupational exposure limits(OELs) for carcinogens

Abstract

Högberg J, Järnberg J. The Nordic Expert Group for Criteria Documentation of Health Risks from Chemicals. 154. Approaches for the setting of occupational exposure limits (OELs) for carcinogens. Arbete och Hälsa 2022;56(2):1–77. This document addresses critical aspects of importance for the derivation of occupational exposure limits (OELs) for chemical carcinogens with focus on non-threshold carcinogens. The narrative is presented with a historical perspective to give a foundation for currently used approaches for cancer risk assessments for the work environment. Aspects addressed comprise scientific as well as regulatory issues. The document intends to give an overview of the area and is not a comprehensive review. A central topic referred to is mechanistic research and insights, and its implications for cancer risk assessment. In that context, the concepts mode of action (MoA) and threshold mechanism, and the distinction between genotoxic and non-genotoxic carcinogens are fundamental. Alongside scientific advancements, the approaches of hazard identification, and qualitative and quantitative risk assessment have developed over time. The key steps in a quantitative risk assessment are outlined, with special attention given to the dose-response assessment and the derivation of an OEL by the use of risk calculations or default assessment factors. The work procedures of a number of bodies performing cancer hazard identifications or quantitative risk assessments are described. Subsequently, regulatory procedures to derive OELs for non-threshold carcinogens are presented with some currently used national strategies serving as illustrations. Non-threshold carcinogens for which the European Union introduced binding OELs in 2017–2019 are presented, including the scientific bases, the cancer risk calculations and the rationales behind the finally adopted OELs. Finally, The Nordic Expert Group (NEG) derives recommendations regarding regulatory aspects in the risk assessment and OEL setting of carcinogens. NEG supports the derivation of health-based OELs for threshold carcinogens. For non-threshold carcinogens, NEG recommends the use of a risk-based approach with linear extrapolation to zero exposure (linear non-threshold, LNT) as the default. The scientific uncertainties of the risk estimates should be described. The recommendations also concern a harmonisation of defined risk levels (terminology and numerical values), and that both collective and individual risks are considered and clearly communicated. Socioeconomic aspects should be dealt with transparently and separated from the scientific health risk assessment, ideally in a separate expert group. The need for further research on cancer mechanisms and low-dose risk is stressed.