Toxicity Decreases with the Decay of Environmentally Persistent Free Radicals in Particulate Matter from Incomplete Solid Fuel Burning

Abstract

Environmentally persistent free radicals (EPFRs) have been linked to the generation of reactive oxygen species (ROS) and adverse health effects. However, there remains a knowledge gap regarding the dynamic changes in reactivity and toxicity during the decay process of EPFRs emitted from incomplete solid fuel burning, which are identified as a primary source of EPFRs. Here, we report the decay behavior of EPFRs in particulate matter (PM) emitted from typical solid fuel burning and the associated ROS generation and cytotoxic effects. The EPFRs in freshly produced PM first undergo rapid exponential decay with lifetimes ranging from 15 to 97 h and are categorized as fast-decay EPFRs. The relative content of fast-decay EPFRs was 40.5 ± 15.3%, while the remaining portion, defined as slow-decay EPFRs, displayed an extremely slow rate of decay. ROS generation and cytotoxicity decreased by 38.8 ± 11.4% and 62.5 ± 12.6%, respectively, following the depletion of fast-decay EPFRs, which were further demonstrated to be responsible for the variations in PM reactivity and toxicity. These new findings underscore the importance of considering the decay process of EPFRs in assessments of PM toxicity.

Pollutant Emissions and Oxidative Potentials of Particles from the Indoor Burning of Biomass Pellets

“…Our finding revealed that the differences in average densities of EPFRs among different fuels were insignificant ( p > 0.05), the values in the coal and raw biomass emissions were almost equal, at 5.8 × 10 16 spins/g PM 2.5 , and that in the biomass pellet emission was 5.5 ± 3.9 × 10 16 spins/g PM 2.5 . The mass concentration of the EPFRs in the PM 2.5 from residential fuel combustion in this study was likely lower than those (10 14 to 10 18 spins/g PM 2.5 ) reported in some studies. − Besides different fuels and burning conditions, changes in EPFRs during the aging process of particles may also contribute to the observed differences among different studies …”

Residential Wood Burning and Vehicle Emissions as Major Sources of Environmentally Persistent Free Radicals in Fairbanks, Alaska

“…Our results imply that exposure to EPFRs and inhalation and respiratory deposition of PM may cause oxidative stress and adverse health effects. A very recent study has observed a positive correlation between cytotoxicity and EPFR concentration . Another recent study by Yang et al (2024) showed that PM oxidative potential in Fairbanks is comparable to that in Atlanta and Los Angeles .…”