Intrinsic Characteristics and Biological Effects of Standard Reference Indoor Dust SRM (R) 2585 and Its Inhalable Subfractions PM10 and PM2.5

Standard Reference Material (R) (SRM (R)) 2585 can be considered as a model sample of settled indoor dust. At least 168 adsorbed chemicals were identified and quantified, generating a complex and potentially toxic mixture. Inhalable fractions PM10 and PM2.5 were isolated and compared to SRM (R) 2585 for their intrinsic properties and their respiratory toxicity using pertinent normal human bronchoepithelial (NHBE) cells. The intrinsic oxidative potential (OP) of SRM (R) 2585 and its subfractions was measured in acellular conditions, together with ROS generation and endotoxin content. For SRM (R) 2585 and PM10, cellular responses were evaluated on NHBE cells after 72 h exposure (1.1 to 110 mu g/mL). The presence of endotoxins associated with an intrinsic prooxidant potential did not lead to the induction of an inflammatory response. Interestingly, cytokine production was decreased, strongly for IL-1 beta and to a lesser extent for IL-6. Only PM10 induced an acute toxicity. In parallel, mutagenicity was evaluated from organic extracts. Mutagenic profiles indicated the concomitant presence of nitro-PAHs in addition to the previously reported PAHs. This could be of concern for long-term health effects in a context of chronic exposure.