Long and short-term exposure to atmospheric particulate matter (PM) has detrimental effects on human health. The effective mechanisms leading to PM toxicity are still not fully understood, even if it is known that physical-chemical properties, strongly influenced by sources and atmospheric processes, are known to play an important role. In this work, PM₁₀ samples were collected, at an urban background site in southern Italy, to determine cytotoxicity (using MTT test on A549 cells), genotoxicity (using the comet assay), and intracellular oxidative stress on A549 cells exposed for 24 h to aqueous extracts of PM₁₀ samples. Organic carbon (OC) and elemental carbon (EC) content of PM₁₀ and acellular determination of oxidative potential with DTT assay were performed to compare results of acellular and cellular biological assays. Cellular (OSGC_V and MTT_V) and acellular (OP^DTT_V) outcomes, normalized in volume, are well correlated (statistically significant results) with carbon content suggesting that combustion sources play an important role in determining cellular oxidative stress and cytotoxicity of PM₁₀. Even if the number of data is limited, genotoxicity results are well correlated (Pearson r > 0.95) with OSGC_V and MTT_V, and a weaker, but statistically significant correlation was observed with OP^DTT_V. OSGC_V is well correlated with the cell mortality observed with the MTT_V test and a lower, but still statistically significant correlation is observed between MTT_V and OP^DDT_V. A statistically significant correlation was found between OP^DTT_V and OSGC_V results. When the outcomes of the cellular and acellular assay are compared normalized in mass (i.e., intrinsic values), the correlations become significantly weaker suggesting that the different sources acting on the site produces particulate matter with different toxicological potential influencing differently the biological tests studied.

Exposure to atmospheric particulate matter (PM) has detrimental effects on health, but specific mechanisms of toxicity are still not fully understood. In recent years, there has been a growing evidence that oxidative stress is an important mechanism of toxicity; however, when acellular oxidative potential (OP) data are correlated with the outcomes of in vitro (or in vivo) toxicological tests there are contrasting results. In this work, an analysis of PM₁₀ health effect indicators was done, using the acellular Dithiotreitol (DTT) assay to retrieve OP^DTT, the Microtox^® test on Vibrio fischeri bacterium to assess the ecotoxicological potential, and the in vitro MTT assay on the human cell line A549 to estimate the cytotoxicological potential. The objective was to evaluate the correlation among acellular OP^DTT and the results from toxicological and ecotoxicological bioassays and how these health-related indicators are correlated with atmospheric PM₁₀ concentrations collected at an urban background site in Southern Italy. Results indicated that both bioassays showed time-dependent and dose-dependent outcomes. Some samples presented significant ecotoxic and cytotoxic response and the correlation with PM₁₀ concentration was limited suggesting that these health endpoints depend on PM₁₀ chemical composition and not only on exposure concentrations. OP^DTT showed a statistically significant correlation with PM₁₀ concentrations. MTT and Microtox outcomes were not correlated suggesting that the two toxicological indicators are sensitive to different physical-chemical properties of PM₁₀. Intrinsic oxidative potential OP^DTT_M (DTT activity normalised with PM₁₀ mass) was correlated with mortality observed with MTT test (normalized with PM₁₀ mass); however, it was not correlated with Microtox outcomes.