Numerous studies have shown health effects related to exposure to ambient particulate matter (PM). In most studies effects were linked to PM mass concentrations whereas evidences indicate that the PM sources and constituents are more closely linked to the induction of toxic responses. The mechanisms of PM related health effects are still incompletely understood, but a hypothesis under investigation is that many of the adverse health effect may derive from oxidative stress. Oxidative stress results when the generations of reactive oxygen species (ROS), or free radicals, exceed the available antioxidant defenses. In light of these observations the oxidative potential (OP) has been proposed as a measure of the capacity of PM to oxidize target molecules, that may potentially serve as a biologically pertinent index of PM toxicity. Among the various assays developed for measuring OP, in this study two common kinetic methods were investigated: the ascorbate assay (AA) and the dithiothreithol (DTT) assay. In both cases the reactions were monitored spectrophotometrically and the methods were compared in terms of different sensitivity to the ROS generating compounds. The results from the two assays were compared using standard solutions of different chemical species such as transition metals, quinones and PAHs. DTT assay was found more sensitive to quinones - especially 9,10-phenanthrenequinone - compare to metals. On the contrary, the AA depletion was strongly influenced by transition metals - mainly copper - even if the assay is also sensitive to quinones. PAHs and oxo-PAHs tested showed only a slightly redox activity with these two assays. The investigated assays were applied to some real samples of PM collected in the Bologna area. Regarding the DTT assay, higher PM concentrations yield greater response, whilst ascorbate depletion was not correlated to the quantity of PM on the filter. The obtained results are very relevant to understand the relative importance of metals and organics towards ROS generation from ambient particles and highlight that other parameters as well as PM mass concentration should be taken into account to evaluate aerosol’s effects on human health.
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|Titolo:||DETERMINATION OF OXIDATIVE POTENTIAL OF PARTICULATE MATTER BY SPECTROPHOTOMETRIC TECHNIQUES|
|Data di pubblicazione:||2015|
|Appare nelle tipologie:||04.3 Abstract (Riassunto) in convegno in Rivista/Volume|