Dynamic Wood Smoke Aerosol Toxicity during Oxidative Atmospheric Aging

Journal Article 1 Mention

Shunyao Wang•2023

Peter J. GallimoreCarolyn Liu-Kang

Top 2% · 98th Percentile

55 citations · Health, Toxicology and Mutagenesis

Multiphase Chemistry and Atmospheric Particles: Reactive Species, Oxidation and ImpactsRole of particulate matter in inducing airway hypersensitivityCharacterizing Emerging Sources of Organic Aerosol

TLDR

Pine smoke can become more harmful as it reacts in the air. Aged smoke showed stronger signs of causing cell stress than fresh smoke, which may matter for people living near wildfire areas.

Summary

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1 Study Aim

The authors examined whether atmospheric aging changes the toxicity of biomass burning organic aerosol (BBOA, particles made from burning plant material). They focused on oxidation by hydroxyl radicals (OH, highly reactive molecules found in air) and compared fresh and aged pine smoke. The study asks whether time in the air changes how harmful pine smoke particles may be.

2 Study Design

The researchers produced aerosol by smoldering pine wood and aged it through reactions with gas-phase OH. They assessed oxidative potential (OP, the ability to drive harmful oxidation) and reactive oxygen species (ROS, reactive oxygen-containing molecules) using two cell-free tests: dithiothreitol (DTT) and dichlorofluorescin (DCFH). Electron paramagnetic resonance (EPR, a method for detecting radicals) measured aerosol radicals. The authors also exposed cells in vitro (in laboratory tests) to fresh and aged aerosol and assessed antioxidant defenses. The team compared laboratory-made fresh and aged pine smoke using chemical tests and cell exposures.

3 Findings

The authors report that both fresh and aged particles showed activity linked to adverse health effects. The DTT and DCFH tests showed significant oxidative potential and ROS formation in aged aerosol. Electron paramagnetic resonance measurements found 50% more radicals after aging. The radical mix shifted from 85% carbon-centered in fresh aerosol to 76% oxygen-centered after aging. Both aerosols prompted prominent antioxidant defenses during cell exposure, indicating oxidative stress. The authors conclude that short-term OH aging can increase particles’ capacity to generate particle-bound ROS, making aged smoke a potentially greater exposure concern for people near wildfire regions. Smoke particles gained more harmful activity as they aged, so fresh-smoke tests may miss some exposure risks.

Abstract

Wildfires are a major source of biomass burning aerosol to the atmosphere, with their incidence and intensity expected to increase in a warmer future climate. However, the toxicity evolution of biomass burning organic aerosol (BBOA) during atmospheric aging remains poorly understood. In this study, we report a unique set of chemical and toxicological metrics of BBOA from pine wood smoldering during multiphase aging by gas-phase hydroxyl radicals (OH). Both the fresh and OH-aged BBOA show activity relevant to adverse health outcomes. The results from two acellular assays (DTT and DCFH) show significant oxidative potential (OP) and reactive oxygen species (ROS) formation in OH-aged BBOA. Also, radical concentrations in the aerosol assessed by electron paramagnetic resonance (EPR) spectroscopy increased by 50% following heterogeneous aging. This enhancement was accompanied by a transition from predominantly carbon-centered radicals (85%) in the fresh aerosol to predominantly oxygen-centered radicals (76%) following aging. Both the fresh and aged biomass burning aerosols trigger prominent antioxidant defense during the in vitro exposure, indicating the induction of oxidative stress by BBOA in the atmosphere. By connecting chemical composition and toxicity using an integrated approach, we show that short-term aging initiated by OH radicals can produce biomass burning particles with a higher particle-bound ROS generation capacity, which are therefore a more relevant exposure hazard for residents in large population centers close to wildfire regions than previously studied fresh biomass burning emissions.

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