This study explores the intermediate uses of 53 petroleum and coal stream (PetCo) substances, focusing on 15 marker constituents with properties of concern such as carcinogenicity, mutagenicity, reprotoxicity, persistence, bioaccumulation, and endocrine disruption. It investigates the potential for these constituents to transfer during intermediate use into the new substance or product and into the environment. Five approaches are employed, including reactivity assessment, literature review, consultation data integration, supply chain interaction analysis, and upstream literature review perspective, to evaluate the likelihood of conversion and assess the potential environmental emission of these constituents. The report presents comprehensive findings that would interest Industry as well as policy stakeholders dealing with PetCo substances, substance management and environmental impact assessment.