Are reactive oxygen species (ROS) a suitable metric to predict toxicity of carbonaceous aerosol particles?

Abstract

Abstract. It is being suggested that particle-bound or particle-induced reactive oxygen species (ROS), which significantly contribute to the oxidative potential (OP) of aerosol particles, are a promising metric linking aerosol compositions to toxicity and adverse health effects. However, accurate ROS quantification remains challenging due to the reactive and short-lived nature of many ROS components and the lack of appropriate analytical methods for a reliable quantification. Consequently, it remains difficult to gauge their impact on human health, especially to identify how aerosol particle sources and atmospheric processes drive particle-bound ROS formation in a real-world urban environment. In this study, using a novel online particle-bound ROS instrument (OPROSI), we comprehensively characterized and compared the formation of ROS in secondary organic aerosols (SOAs) generated from organic compounds that represent anthropogenic (naphthalene, SOANAP) and biogenic (β-pinene, SOAβPIN) precursors. The SOA mass was condensed onto soot particles (SP) under varied atmospherically relevant conditions (photochemical aging and humidity) to mimic the SOA formation from a mixing of traffic-related carbonaceous primary aerosols and volatile organic compounds (VOCs). We systematically analyzed the ability of the aqueous extracts of the two aerosol types (SOANAP-SP and SOAβPIN-SP) to induce ROS production and OP. We further investigated cytotoxicity and cellular ROS production after exposing human lung epithelial cell cultures (A549) to extracts of the two aerosols. A significant finding of this study is that more than 90 % of all ROS components in both SOA types have a short lifetime, highlighting the need to develop online instruments for a meaningful quantification of ROS. Our results also show that photochemical aging promotes particle-bound ROS production and enhances the OP of the aerosols. Compared to SOAβPIN-SP, SOANAP-SP elicited a higher acellular and cellular ROS production, a higher OP, and a lower cell viability. These consistent results between chemical-based and biological-based analyses indicate that particle-bound ROS quantification could be a feasible metric to predict aerosol particle toxicity and adverse human effects. Moreover, the cellular ROS production caused by SOA exposure not only depends on aerosol type but is also affected by exposure dose, highlighting a need to mimic the process of particle deposition onto lung cells and their interactions as realistically as possible to avoid unknown biases.

Hydrophobic soot nanoparticles as a non-cytotoxic motility activator of human spermatozoa

“…44,45 Focusing on the toxicological mechanisms of soot aerosols, their high surface oxidation and hydrophilicity facilitate the generation of reactive oxygen species (ROS), promoting morphological and chemical contact with hydrophilic biomolecules produced by the human lung cells, peripheral blood monocyte-derived macrophage cells or A549-type cells. [50][51][52][53][54][55][56][57] This is accompanied by cell swelling and membrane blebbing, 50 phagocytosis 51 or cytoplasm internalization of soot, 55 where the smaller nanoparticles 51 and those with increased concentration of environmentally persistent free radicals (EPFR) exhibit the highest nanotoxicity. 55 Nevertheless, the non-or mild cytotoxicity of the rapeseed oil soot (at one order of magnitude higher concentration compared to stove-released soot 55 ) has its scientic explanation: if appears as a functional coating, the soot is superhydrophobic and when peeled off, it is still extremely water-repellent and does not mix well with watery liquids (e.g., seminal uids) for at least 90 min, as demonstrated in Fig.…”

Pathogenic Mechanisms of Secondary Organic Aerosols

“…For example, one of the main mechanism concerns particle-bound ROS . SOA may contain ROS or constituents that will react with thiols of host molecules and have a direct effect by increasing the level of exogenous ROS like H 2 O 2 , mainly from anthropogenic sources. − Some organic compounds can produce oxygen species through redox and Fenton reactions …”

The oxidative potential of fresh and aged elemental carbon-containing airborne particles: a review

“…This agrees well with the studies where PAHs are well correlated with OP ( r = 0.93, p < 0.05); 151 n -alkanes are moderately correlated with OP in warm and cold seasons ( r = 0.67 and 0.83), 152 and organic acids are poorly correlated with OP ( r coefficient and p not shown). 153 However, despite the high correlation coefficient for PAHs, the roles of fuel type and the vehicular operational and environmental conditions introduce great uncertainties of PAH components and hence their roles in the OP remain poorly understood. The concentrations of PAHs in the exhaust of vehicle engines are much lower in low-load runs than in high-load runs because PAHs with three- and four rings are present in the gas phase in low-load runs but in the particle phase in high load runs.…”