Generation of Reactive Oxygen Species Mediated by Humic-like Substances in Atmospheric Aerosols

Particulate matter (PM)-mediated reactive oxygen species (ROS) generation has been implicated in health effects posed by PM. Humic-like substances (HULIS) are an unresolved mixture of water-extracted organic compounds from atmospheric aerosol particles or isolated from fog/cloudwater samples. In thi...

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Bibliographic Details
Published in:	Environmental science & technology 2011-12, Vol.45 (24), p.10362-10368
Main Authors:	Lin, Peng, Yu, Jian Zhen
Format:	Article
Language:	eng
Subjects:	Aerosols - analysis Aerosols - chemistry Air. Soil. Water. Waste. Feeding Airborne particulates Applied sciences Atmosphere - chemistry Atmospheric aerosols Atmospheric pollution Biological and medical sciences Chelation therapy Chemical reactions Environment. Living conditions Environmental Monitoring Environmental Processes Exact sciences and technology Humic Substances - analysis Medical sciences Organic chemistry Oxidation Particulate Matter - analysis Particulate Matter - chemistry Pollutants physicochemistry study: properties, effects, reactions, transport and distribution Pollution Public health. Hygiene Public health. Hygiene-occupational medicine Reactive Oxygen Species - analysis Reactive Oxygen Species - chemistry
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Summary:	Particulate matter (PM)-mediated reactive oxygen species (ROS) generation has been implicated in health effects posed by PM. Humic-like substances (HULIS) are an unresolved mixture of water-extracted organic compounds from atmospheric aerosol particles or isolated from fog/cloudwater samples. In this study, we use a cell-free dithiothreitol (DTT) assay to measure ROS production mediated by HULIS. The HULIS samples are isolated from aerosols collected at a rural location and a suburban location in the Pearl River Delta, China. In our experiments, ROS activities by residue metal ions in the HULIS fraction are suppressed by including a strong chelating agent in the DTT assay. Under conditions of DTT consumption not exceeding 90%, the HULIS-catalyzed oxidation of DTT follows the zero-order kinetics with respect to DTT concentration, and the rate of DTT oxidation is proportional to the dose of HULIS. The ROS activity of the aerosol HULIS, on a per unit mass basis is 2% of the ROS activity by a reference quinone compound, 1,4-naphthoquinone and exceeds that of two aquatic fulvic acids. The HULIS fraction in the ambient samples tested exhibits comparable ROS activities to the organic solvent extractable fraction, which would contain compounds such as quinones, a known organic compound class capable of catalyzing generation of ROS in cells. HULIS was found to be the major redox active constituent of the water-extractable organic fraction in PM. It is plausible that HULIS contains reversible redox sites, thereby serving as electron carriers to catalyze the formation of ROS. Our work suggests that HULIS could be an active PM component in generating ROS and further work is warranted to characterize its redox properties.
ISSN:	0013-936X 1520-5851