Impact of urban air ultrafine particles on embryonic development and their association to transport emissions

Abstract Airborne ultrafine particles (UFP) constitute a potential risk factor for human health, being transport one of the most relevant sources, particularly in urban environments. We collected UFP from outdoor sites in Barcelona and Valencia (Spain) that were differently impacted by air pollution from road traffic, trains, ships, or planes. Zebrafish embryos were exposed to organic extracts from collection filters, and their transcriptomes were analysed by RNA deep sequencing. Functional analysis of 2,941 significantly affected transcripts revealed a strong enrichment in functions related to general embryotoxicity, like induction of degradation pathways (endocytosis, necroptosis), and inhibition of development- and cell division-related genes. This embryotoxicity-related transcriptional response was linked to samples exhibiting elevated concentrations of UFP and several inorganic and organic pollutants. It was particularly strong in airport samples, which were relatively poor on aromatic polycyclic hydrocarbons (PAHs). The functional analysis also identified a relatively small subset of genes configuring a typical dioxin-like response linked to PAH-rich emissions from harbour and traffic samples. Our findings indicate that the parameters currently used to assess air quality overlook the contribution of UFP and other non-regulated pollutants in the total airborne toxicity and, therefore, they do not adequately protect human populations.