Hybrid tool for occupational health risk assessment and fugitive emissions control in chemical processes based on the source, path and receptor concept

Fugitive emissions are unavoidable releases that occur continuously throughout a process plant or wherever there are connections or seals between the process fluids and the external environment. The daily exposure of workers to such emissions, typically spread across an entire chemical plant, poses a serious threat to their health and safety. Previous works have focused on assessing the occupational health risks in chemical plants through indexes such as the inherent occupational health index and the integrated inherent safety index. The indexes serve as good proxy indicators for potential sources of occupational hazards (chemicals, process conditions) and process equipment. However, by considering the Source-Path-Receptor (SPR) model, the eventual health risk is also dependent on the path and receptor, where a potential leakage and exposure can occur, respectively. Typically, chemical plants are fitted with controls and mitigation measures known as protection layers (PL) to control hazards. Hence, the occupational health risks in chemical plants due to fugitive emissions require a more holistic methodology for assessment and evaluation. Therefore, a hybrid framework for assessing the occupational health risks from fugitive emissions was developed by adopting and integrating the concepts of source-path-receptor, layers of protection and hierarchy of control. The generic protection layers identified were classified according to the traditional hierarchy of controls. At the source, the protection layers identified were hazard elimination/substitution, inherently safer design, and engineering controls. Next, the maintenance and equipment reliability were identified as PL along the exposure path. Finally, at the receptor, worker-exposure was linked to management systems, procedural safety behaviour and culture. Therefore, the proposed methodology can be used for benchmarking and performance tracking of occupational health risk in a chemical plant over time, as the methodology includes the time-varying parameters of plant maintenance, management system compliance, safety behaviour and culture.