Oxidative Potential of Atmospheric Particulate Matter

Atmospheric particulate matter (PM) encompasses a complex mixture of solid and liquid particles suspended in the air, varying in size from coarse (PM10) to fine (PM2.5) and ultrafine fractions. The oxidative potential (OP) of PM quantifies its capacity to generate reactive oxygen species (ROS) through redox reactions catalysed by transition metals, quinones and organic compounds at the particle surface. OP provides a more nuanced metric of PM toxicity than mass concentration alone, linking chemical composition to cellular oxidative stress, inflammation and subsequent cardiopulmonary health effects. Diverse acellular assays—most notably the dithiothreitol (DTT) and ascorbic acid (AA) methods—measure the rate of antioxidant consumption as a proxy for ROS production. Spatial and seasonal variability in OP reflect source contributions, including combustion emissions, secondary organic aerosol formation and mineral dust. Global field studies demonstrate that localized chemical profiles can markedly influence intrinsic toxicity, underscoring the need for regionally adapted exposure–response functions and tailored mitigation strategies.

Research from Nature Portfolio

Recent studies have assessed how chemical heterogeneity shapes the link between PM mass, OP and biological response across multiple continents. One large-scale investigation collected PM2.5 samples from fourteen sites spanning four continents and applied five acellular OP assays alongside cytotoxicity endpoints. The findings reveal a non-linear relationship between PM mass and OP, driven by regional differences in metal and organic content, and underscore the importance of incorporating OP into concentration-response models for health burden estimation. Foundational work has also characterised source-specific toxicity scores, integrating chemical and biological metrics for particles emitted from traffic, biomass burning and secondary organic aerosol formation. These toxicity rankings highlight the elevated OP and inflammatory potential of combustion-derived fine particles, particularly diesel exhaust, guiding priorities for emission control. Further modelling of epithelial lining fluid chemistry has quantified ROS production rates induced by ambient concentrations of transition metals, quinones and secondary oxidised organics, providing a mechanistic basis for regional risk assessment in polluted megacities.

Oxidative Potential of Atmospheric Particulate Matter publication trend

The graph below shows the total number of articles in oxidative potential of atmospheric particulate matter across all publications each year (not limited to Nature Index journals).

Technical terms

Oxidative potential (OP): A measure of the ability of particulate matter to deplete antioxidants via redox reactions, serving as a proxy for its capacity to generate reactive oxygen species.

Reactive oxygen species (ROS): Highly reactive molecules produced by oxygen-based chemical reactions, implicated in oxidative stress and inflammation in biological tissues.

PM2.5: Particulate matter with an aerodynamic diameter of less than 2.5 micrometres, capable of penetrating deep into the respiratory tract.

Dithiothreitol (DTT) assay: An acellular test that quantifies OP by measuring the rate of DTT oxidation in the presence of particle extracts.

Secondary organic aerosol (SOA): Particles formed in the atmosphere from the oxidation of volatile organic compounds, contributing to the oxidative potential of ambient aerosol.

References

1. Inter-continental variability in the relationship of oxidative potential and cytotoxicity with PM2.5 mass. Nature Communications (2024).
2. Characterisation of the correlations between oxidative potential and in vitro biological effects of PM10 at three sites in the central Mediterranean. Journal of Hazardous Materials (2023).
3. Rapid transformation of wildfire emissions to harmful background aerosol. npj Climate and Atmospheric Science (2023).
4. Oxidative potential of ambient water-soluble PM2.5 in the southeastern United States: contrasts in sources and health associations between ascorbic acid (AA) and dithiothreitol (DTT) assays. Atmospheric Chemistry and Physics (2016).
5. Chemical exposure-response relationship between air pollutants and reactive oxygen species in the human respiratory tract. Scientific Reports (2016).