Biological Factors Influencing Individual Responses to Propylene Oxide: A Systematic Review

ObjectiveThis systematic review aims to synthesize current knowledge on Propylene Oxide (PO) in human exhaled breath, examining its presence across various biological matrices and exploring methodologies for its analysis. It seeks to elucidate the sources of PO in the human body and understand individual variability in detoxification processes. MethodsA comprehensive literature search was conducted across 12 databases and specialized repositories, spanning over 10,000 publications without language restrictions until May 16, 2024. Seventeen AI tools were employed to enhance study identification and analysis, focusing on both direct mentions and indirect evidence of PO behavior and detection in the human body. Assessment tools for risk of bias included SYRCLEs tool for animal studies, the Newcastle-Ottawa Scale for cohort and case-control studies, and the ROBINS-I tool for non-randomized studies. The selection process yielded 89 studies, encompassing a range of research types and species, supplemented by reviews, monographs, and editorials to provide a comprehensive overview. ResultsThe search revealed limited direct evidence on PO concentrations in exhaled breath, with only one reference providing concrete data (0.083 ppb to 0.3 ppb following exposures to 10-25 ppm of propylene). A study of ours, published separately, indicated significantly higher PO concentrations (hundreds of ppb or even ppm) in individuals with environmental sensitivities. Numerous references offered indirect insights into POs persistence and detection in blood and urine. The review highlights the enzymes involved in PO metabolism, the evolution of analytical methodologies, and the challenges and potential of AI tools in systematic reviews. ConclusionsThe scarcity of direct evidence on PO in exhaled breath underscores a significant gap in the literature and existing databases. Directly and indirectly relevant sources indicate variability in environmental compound concentrations in exhaled breath, influenced by genetics, health status, metabolism, and the microbiome. The review emphasizes the difficulties in synthesizing data on PO effects due to heterogeneous inputs and complex exposure scenarios. It underscores the need for advanced AI capabilities in literature reviews to capture nuanced, indirect evidence more effectively and calls for targeted research and technological innovation in environmental health sciences. Enhancing AI tools to navigate scientific literature with greater efficacy can leverage PRISMA guidelines and diverse data sources to minimize bias and enhance reliability. This approach will aid in addressing the complex interplay of biological and environmental factors in PO metabolism and toxicity, ultimately improving risk assessments and intervention strategies.