Abstract

Objective This 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.

Methods A comprehensive literature search was conducted across 12 databases and specialized repositories, spanning over 10,000 publications without language restrictions until February 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 SYRCLE’s 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 88 studies, encompassing a range of research types and species, supplemented by reviews, monographs, and editorials to provide a comprehensive overview.

Results The 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). However, numerous references offered indirect insights into PO’s persistence and detection in the human body, particularly in blood and urine. The review highlights the enzymes involved in PO metabolism, the evolution of analytical methodologies, and the challenges and potentials of employing AI tools in systematic reviews.

Conclusions The 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 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. This study advocates for the strategic enhancement of AI tools to navigate scientific literature with greater efficacy, leveraging PRISMA guidelines and diverse data sources to minimize bias and enhance reliability.

Competing Interest Statement

The authors have declared no competing interest.

Clinical Protocols

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=397159

Funding Statement

This study did not receive any funding

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Abbreviations2-HPMAN-acetyl-S-(2-hydroxypropyl)cysteine, mercapturic acids derived from propylene oxideADHAlcohol dehydrogenaseAEGLAcute Exposure Guideline Levels developed by EPAAIArtificial IntelligenceALDHAldehyde dehydrogenaseCYPsCytochromes P450, involved in the metabolism of xenobiotics in the bodyCYP2E1Cytochrome P450 2E1, a member of the cytochrome P450 mixed-function oxidase systemEHepoxide hydrolase, also known as mEHEPAthe Environmental Protection AgencyFMOflavin-containing monooxygenase enzyme familyGSTGlutathione S-transferase familyIARCInternational Agency for Research on CancerLC50median lethal concentration in air that can kill 50% of a test populationLD50median lethal dose that can kill 50% of a test populationLOALevel of Distinct Odor AwarenessmEHmicrosomal epoxide hydrolaseMeSHMedical Subject Headings, a controlled and hierarchically-organized vocabulary produced by NLMNLMthe National Library of MedicineNPSHnonprotein sulfhydryl (SH-groups)OSFOpen Science Framework, a platform for data sharing and collaborationPPBparts per billionPPBVparts per billion by volume, specifically refers to the concentration of a substance in a gaseous mixturePPMparts per millionPPMVparts per million by volumePRISMAPreferred Reporting Items for Systematic Reviews and Meta-AnalysesPEPropylenePGPropylene GlycolPOPropylene OxideRNMrespiratory nasal mucosaRQResearch QuestionSCEsister chromatid exchangesSMRstandardized mortality ratioSSBDNA single-strand breaksTWAtime weighted averageURTupper respiratory tractUS EPAUS Environmental Protection AgencyVOSviewer“Visualization of Similarities Viewer” – a software tool developed for constructing and visualizing scientific landscapes