Abstract
BackgroundAlthough the mechanisms of airborne particulate matter (PM) related health effects remain incompletely understood, one emerging hypothesis is that these adverse effects derive from oxidative stress, initiated by the formation of reactive oxygen species (ROS) within affected cells. Typically, ROS are formed in cells through the reduction of oxygen by biological reducing agents, with the catalytic assistance of electron transfer enzymes and redox active chemical species such as redox active organic chemicals and metals. The purpose of this study was to relate the electron transfer ability, or redox activity, of the PM samples to their content in polycyclic aromatic hydrocarbons and various inorganic species. The redox activity of the samples has been shown to correlate with the induction of the stress protein, hemeoxygenase-1.ResultsSize-fractionated (i.e. < 0.15; < 2.5 and 2.5 – 10 μm in diameter) ambient PM samples were collected from four different locations in the period from June 2003 to July 2005, and were chemically analyzed for elemental and organic carbon, ions, elements and trace metals and polycyclic aromatic hydrocarbons. The redox activity of the samples was evaluated by means of the dithiothreitol activity assay and was related to their chemical speciation by means of correlation analysis. Our analysis indicated a higher redox activity on a per PM mass basis for ultrafine (< 0.15 μm) particles compared to those of larger sizes. The PM redox activity was highly correlated with the organic carbon (OC) content of PM as well as the mass fractions of species such as polycyclic aromatic hydrocarbons (PAH), and selected metals.ConclusionThe results of this work demonstrate the utility of the dithiothreitol assay for quantitatively assessing the redox potential of airborne particulate matter from a wide range of sources. Studies to characterize the redox activity of PM from various sources throughout the Los Angeles basin are currently underway.
Highlights
The mechanisms of airborne particulate matter (PM) related health effects remain incompletely understood, one emerging hypothesis is that these adverse effects derive from oxidative stress, initiated by the formation of reactive oxygen species (ROS) within affected cells
Other studies have found associations with PM chemical constituents such as sulfate [7,8], trace elements and metals such as silicon [9], vanadium [10], iron, nickel and zinc [11], as well as elemental carbon [12,13], and polycyclic aromatic hydrocarbons (PAH) [14]. Results from these studies have been inconsistent due to the different health outcomes considered, the likelihood that health effects are induced by a combination of several physical or chemical properties of PM and the possibility of fortuitous associations, inherent in studies involving hundreds of measured organic and elemental chemical species that may be associated with the observed health effects
This is true for the quartz filters used for the EC/organic carbon (OC) analysis and it is the reason that the mass reconstruction by chemical analysis is higher than the weighted mass for three of the samples collected (Caldecott Bore 2- PM0.15, and CA-110 PM0.15 and PM2.5)
Summary
The mechanisms of airborne particulate matter (PM) related health effects remain incompletely understood, one emerging hypothesis is that these adverse effects derive from oxidative stress, initiated by the formation of reactive oxygen species (ROS) within affected cells. The purpose of this study was to relate the electron transfer ability, or redox activity, of the PM samples to their content in polycyclic aromatic hydrocarbons and various inorganic species. Epidemiological and toxicological studies have described associations between measured particulate matter (PM) mass and adverse health outcomes [1,2,3,4]. When considering plausible biological mechanisms of injury, PM mass may be a surrogate measure of other physical or chemical properties of PM that are the causal factors associated with the observed health outcomes. Results from these studies have been inconsistent due to the different health outcomes considered, the likelihood that health effects are induced by a combination of several physical or chemical properties of PM and the possibility of fortuitous associations, inherent in studies involving hundreds of measured organic and elemental chemical species that may be associated with the observed health effects
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