Characterization and comparison of PM&amp;lt;sub&amp;gt;2.5&amp;lt;/sub&amp;gt; oxidative potential assessed by two acellular assays

Dong Gao,Armistead G Russell,James A Mulholland,Krystal J Godri Pollitt,Rodney J Weber

doi:10.5194/acp-20-5197-2020

Characterization and comparison of PM&lt;sub&gt;2.5&lt;/sub&gt; oxidative potential assessed by two acellular assays

Dong Gao, Armistead G Russell + Show 3 more

Open Access

https://doi.org/10.5194/acp-20-5197-2020

Copy DOI

Abstract

Abstract. The capability of ambient particles to generate in vivo reactive oxygen species (ROS), called oxidative potential (OP), is a potential metric for evaluating the health effects of particulate matter (PM) and is supported by several recent epidemiological investigations. Studies using various types of OP assays differ in their sensitivities to varying PM chemical components. In this study, we systematically compared two health-relevant acellular OP assays that track the depletion of antioxidants or reductant surrogates: (i) the synthetic respiratory-tract lining fluid (RTLF) assay that tracks the depletion of ascorbic acid (AA) and glutathione (GSH) and (ii) the dithiothreitol (DTT) assay that tracks the depletion of DTT. Yearlong daily samples were collected at an urban site in Atlanta, GA (Jefferson Street), during 2017, and both DTT and RTLF assays were performed to measure the OP of water-soluble PM2.5 components. PM2.5 mass and major chemical components, including metals, ions, and organic and elemental carbon were also analyzed. Correlation analysis found that OP as measured by the DTT and AA depletion (OPDTT and OPAA, respectively) were correlated with both organics and some water-soluble metal species, whereas that from the GSH depletion (OPGSH) was exclusively sensitive to water-soluble Cu. These OP assays were moderately correlated with each other due to the common contribution from metal ions. OPDTT and OPAA were moderately correlated with PM2.5 mass with Pearson's r=0.55 and 0.56, respectively, whereas OPGSH exhibited a lower correlation (r=0.24). There was little seasonal variation in the OP levels for all assays due to the weak seasonality of OP-associated species. Multivariate linear regression models were developed to predict OP measures from the particle composition data. Variability in OPDTT and OPAA were not only attributed to the concentrations of metal ions (mainly Fe and Cu) and organic compounds but also to antagonistic metal–organic and metal–metal interactions. OPGSH was sensitive to the change in water-soluble Cu and brown carbon (BrC), a proxy for ambient humic-like substances.

Highlights

Epidemiological studies have consistently reported associations between particulate matter (PM) and increased morbidity and mortality (Brunekreef and Holgate, 2002; Cohen et al, 2017; Lippmann, 2014; Norris et al, 1999; Pope et al, 2004; Samet et al, 2000; Sun et al, 2010; Thurston et al, 2017)
A comparison was made between two of the most common techniques used for the assessment of PM oxidative potential based on antioxidant depletion from a complex synthetic respiratory-tract lining fluid (RTLF) (OPAA and OPGSH) and DTT oxidation (OPDTT)
These two assays were used to quantify the watersoluble OP of ambient PM2.5 collected in urban Atlanta over a 1-year period based on daily filter samples

Summary

Introduction

Epidemiological studies have consistently reported associations between particulate matter (PM) and increased morbidity and mortality (Brunekreef and Holgate, 2002; Cohen et al, 2017; Lippmann, 2014; Norris et al, 1999; Pope et al, 2004; Samet et al, 2000; Sun et al, 2010; Thurston et al, 2017). Inhaled PM can directly introduce PM-bound reactive oxygen species (ROS) to the surface of the lung, where they react with and deplete lung-lining fluid antioxidants, or introduce redox-active PM species, which can react with biological reductants and generate ROS in vivo (Lakey et al, 2016). The latter can occur in organs beyond the lungs by particles or chemical species being translocated from the lungs throughout the body. The ability of PM to generate ROS in vivo, referred to as the oxidative potential (OP) of particles, has gained increasing attention as a possibly more integrative health-relevant measure of ambient PM toxicity than PM mass concentration, which may contain a mix of highly toxic (e.g., polycyclic aromatic hydrocarbons (PAHs), quinones, environmentally persistent free radicals, highly oxygenated organic molecules, and transition metals) to relatively benign (e.g., sulfate and ammonium nitrate) PM components (Frampton et al, 1999; Khachatryan et al, 2011; Lippmann, 2014; Tong et al, 2018, 2019)

Methods

Results

Conclusion