Sunday, February 18, 2024

The Ubiquitous Journey of Propylene Oxide

While Propylene Oxide (PO) may not be as infamous as some chemicals, its widespread use in industrial and consumer applications has made it a constant presence in our environment. Industries that rely on PO include those producing polyurethane polyols, propylene glycol, and fumigants.

The global market for Propylene Oxide estimated at $14.4 billion in 2020, is projected to reach $18.8 billion by 2027. Additionally, traffic emissions contribute to ambient levels of propylene, the precursor of PO, further underscoring its ubiquitous nature.

Recent research has revealed that many chemicals, including PO, leave more significant marks on the human body than previously thought. A new study by the Environmental Working Group (EWG) found chlormequat, a lesser-known pesticide, in 80% of people tested. Chlormequat chloride, used increasingly on grain crops in North America, has been linked to reduced fertility and developmental harm at doses lower than regulatory agencies' allowable daily intake levels. The study reported a significant increase in chlormequat concentrations in urine samples collected in 2023 compared to previous years.

A recent systematic review published on MedrXiv, titled "Biological Factors Influencing Individual Responses to Propylene Oxide," sheds light on the complex interplay between environmental exposures, genetic makeup, and individual susceptibility concerning PO levels in the human body. This review highlights the growing public health significance of propylene oxide beyond occupational exposure.

The study emphasizes the importance of considering individual variability in response to PO exposure, influenced by factors such as sex, dietary preferences, genetics, and physiology. It focuses on several genes (CYPs, mEH, GSTT1, GSTM1, FMO3, ADH, ALDH, GDHt) and microbes (including opportunistic pathogens, neutral or even beneficial bacteria) that could be relevant to PO metabolism reactivation and elimination from the body.

PO, primarily encountered through inhalation in occupational settings, poses potential health risks due to its genotoxic effects on DNA. The metabolism of PO primarily occurs through glutathione conjugation and epoxide hydrolase-mediated hydration, with interspecies differences noted. Furthermore, the human microbiome's role in PO metabolism highlights the complexity of individual responses, while environmental factors and seasonal variations further modulate PO's impact.

This comprehensive review stresses the limitations in our abilities to maintain and continuously update living reviews and indexing. It also emphasizes the importance of advancing AI capabilities in literature reviews to capture nuanced, indirect evidence more effectively. While AI tools like Elicit and Perplexity show promise, challenges persist in processing longer segments of information and ensuring consistency across platforms.

Moving forward, the development of specialized AI architectures tailored for systematic reviews is imperative. By enhancing AI tools strategically, we can navigate the complexities of scientific literature more effectively, enabling better summarization and addressing unanswered questions in environmental health research. This study paves the way for targeted research and technological innovation, advocating for a multidisciplinary approach to understanding individual responses to environmental chemicals like PO.


Gabashvili, IS. Biological Factors Influencing Individual Responses to Propylene Oxide: A Systematic Review medRxiv 2024.02.15.24302622; doi:

Temkin, A.M., Evans, S., Spyropoulos, D.D. et al. A pilot study of chlormequat in food and urine from adults in the United States from 2017 to 2023. J Expo Sci Environ Epidemiol (2024).

Open-Source Project: OSF | Biological Factors that Influence Individual Responses to Environmental Epoxides DOI 10.17605/OSF.IO/W7682