OECD workshop on approaches for establishing Occupational Exposure Limits Michelle Deveau Health Canada.pdf
- 1. General OEL derivation process: Summary of Results from the OECD Report OECD Online Workshop Approaches for Establishing OELs October 21, 2022
- 2. The absence of a globally harmonised approach contributes towards differences in derivation approaches and resulting OEL values In February 2021, a survey on OEL development was sent to WPHA and WPEA members Responses were received from 13 countries/regions Results related to OEL derivation are presented today Background 2 Available at https://www.oecd.org/ officialdocuments
- 3. 1. Executive Summary 2. Introduction/Background 3. Roles, responsibilities and scope for OEL development 4. Methods for development and derivations of occupational exposure limits 5. Successes and challenges of OEL programme implementation 6. Discussion 1. Similarities and differences in approaches to design and implementation 2. Potential for harmonization Report Outline 3
- 4. Roles, responsibilities, and scope Governance systems for OEL development vary around the world De novo development vs. adopting or adapting existing OELs Mandatory vs. non-binding OELs Mandatory OELs usually consider technical feasibility and socioeconomic impacts Non-binding OELs typically solely consider health-based guidelines Committees proposing OELs may include representatives from industry, worker groups, and the scientific community, in addition to government agencies 4
- 5. OEL development at a glance 5 Points of Departure selection NOAEL/LOAEL BMD/BMDL Points of Departure modification Adjust workers actual exposure (exposure frequency and duration) Use of uncertainty factors (UFs) Interspecies differences Short-term to long-term Individual sensitivity NOAEL to LOAEL Approach for genotoxic carcinogens Linear extrapolation Statistical exposure-response models Setting acceptable risk levels Methodology for deriving OELs How data is evaluated to support and develop OELs Types of data included in the data search Scientific literatures Reports made by established bodies Information from stakeholders How data quality is assessed Use tools/guidelines Develop criteria Use data assessed by other organisations How critical studies are identified Human data Animal studies Read-across and QSARs Definitions and Scope of Values Endpoints included/excluded Sensory irritation Systemic effects Specific target organ toxicity Type of OELs derived 8h time weighted averages Short-term values (15 min & ceiling) Notation developed Skin/Noise Sensitisation (skin and respiratory) CMR (carcinogenicity, mutagenicity, repro)
- 6. Methods: Definitions and scope of values Organisations typically derive their OELs for chronic effects as 8-hour TWAs Acute effects typically addressed using 15-minute short-term values, and sometimes using a value not to be exceeded at any time (ceiling limit) Endpoints typically included are sensory irritation (ocular, dermal, respiratory), systemic effects and specific target organ toxicity A variety of endpoints are considered for exclusion amongst the organizations for their OEL development, including carcinogenicity, genotoxicity, reproductive and/or developmental toxicity, and sensitisation Organisations also generally limit critical effects to endpoints that are relevant to humans and observed at the lowest exposure All organization use qualitative hazard notations Most common notation is for systemic effects due to dermal exposures Other notations also for carcinogenicity, skin and respiratory sensitisation, ototoxicity, reproductive toxicity, mutagenicity, and direct dermal toxicity 6
- 7. Methods: Data evaluation Data comes from published scientific literature, reviews, and/or reports (from other established or recognized organizations) Some organizations examine unpublished studies from trustworthy sources, and/or if provided by stakeholders, industries, or unions Organizations typically include epidemiological and experimental studies (human and/or animal data) in the data search Human data are used whenever possible, with animal studies used as necessary, and sometimes supplemented by in vitro data Evaluation of data quality and consideration of weight of evidence are performed by organisations; although approaches differ, they tend to evaluate the relevance, reliability, and adequacy of the data Read-across from chemical analogues and quantitative structure-activity relationship (QSAR) approaches used by some organisations to fill data gaps 7
- 8. Selection of POD is based on the data available Some organisations will use benchmark concentration approaches to derive a POD if possible NOAELs (and LOAELs, whenever necessary) are also used as PODs, either preferentially in some organisations, or limited to instances when benchmark approaches cannot be used Other statistical exposureresponse models might be used to derive PODs from epidemiological data Uncertainty factors considered by most of the organisations include inter/intraspecies variation, LOAEL to NOAEL extrapolation, and study duration extrapolation Approaches for carcinogenicity can vary Linear approaches for non-threshold carcinogens where acceptable or minimal risk concentrations for carcinogenicity within included organisations range from 1 in 1,000 to 1 in 1,000,000. Non-linear extrapolation is also employed by some organisations when carcinogenicity appears to result from a threshold mode of action. Methods: Calculating OELs 8
- 9. Summary Similarities were observed in the overall scientific process of evaluating health-based considerations Differences arose in the applications of specific approaches and decisions The scope of each organisations OELs can influence the policies that drive decision making 9