Environmentally persistent free radicals in PM2.5: a review

Mengxia Xu, Tao Wu, Yu Ting Tang, Tong Chen, Lavrent Khachatryan, Poornima Ramesh Iyer, Dengting Guo, Anran Chen, Miao Lyu, Jinhu Li, Jiaqi Liu, Dan Li, Yuxin Zuo, Shihan Zhang, Yiran Wang, Yining Meng, Fei Qi

Research output: Journal PublicationReview articlepeer-review

30 Citations (Scopus)


Environmentally persistent free radicals (EPFRs) are a new class of pollutants that are long-lived in fine particles (PM2.5), i.e., their 1/e lifetime ranges from days to months (or even infinite). They are capable of producing harmful reactive oxygen species such as hydroxyl radicals. The redox cycling of EPFRs is considered as an important pathway for PM2.5 to induce oxidative stress inside the humans, causing adverse health effects such as respiratory and cardiovascular diseases. Consequently, research regarding their toxicity, formation and environmental occurrences in PM2.5 has attracted increasing attentions globally during the past two decades. However, literature data in this field remain quite limited and discrete. Hence, an extensive review is urgently needed to summarize the current understanding of this topic. In this work, we systematically reviewed the analytical methods and environmental occurrences, e.g., types, concentrations, and decay behaviors, as well as possible sources of EPFRs in PM2.5. The types of pretreatment methods, g-values of common EPFRs and categories of decay processes were discussed in detail. Moreover, great efforts were made to revisit the original data of the published works of EPFRs in airborne particulate matter and provided additional useful information for comparison where possible, e.g., their mean and standard deviation of g-values, line widths (∆Hp-p), and concentrations. Finally, possible research opportunities were highlighted to further advance our knowledge of this emerging issue.

Original languageEnglish
Pages (from-to)177-197
Number of pages21
JournalWaste Disposal and Sustainable Energy
Issue number3
Publication statusPublished - Nov 2019


  • Decay
  • Environmentally persistent free radical
  • g-Value
  • Line width
  • PM
  • Source

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Waste Management and Disposal
  • Pollution


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