Cerium oxide nanoparticles (CeO2NPs), used in some diesel fuel additives to improve fuel combustion efficiency and exhaust filter operation, have been detected in ambient air and concerns have been raised about their potential human health impact. The majority of CeO2NP inhalation studies undertaken to date have used aerosol particles of larger sizes than the evidence suggests are emitted from vehicles using such fuel additives. Hence, the objective of this study was to investigate the effects of inhaled CeO2NP aerosols of a more environmentally relevant size, utilizing a combination of methods, including untargeted multi-omics to enable the broadest possible survey of molecular responses and synchrotron X-ray spectroscopy to investigate cerium speciation. Male Sprague–Dawley rats were exposed by nose-only inhalation to aerosolized CeO2NPs (mass concentration 1.8 mg/m3, aerosol count median diameter 40 nm) for 3 h/d for 4 d/week, for 1 or 2 weeks and sacrificed at 3 and 7 d post-exposure. Markers of inflammation changed significantly in a dose- and time-dependent manner, which, combined with results from lung histopathology and gene expression analyses suggest an inflammatory response greater than that seen in studies using micron-sized ceria aerosols. Lipidomics of lung tissue revealed changes to minor lipid species, implying specific rather than general cellular effects. Cerium speciation analysis indicated a change in Ce3+/Ce4+ ratio within lung tissue. Collectively, these results in conjunction with earlier studies emphasize the importance of aerosol particle size on toxicity determination. Furthermore, the limited effect resolution within 7 d suggested the possibility of longer-term effects.

Polycyclic aromatic hydrocarbons including Benzo[]pyrene have been recognised as important pollutant chemicals with the potential to influence the respiratory system in disease. Airway epithelial cells are an integral component of how immune responses are directed as a consequence of exposure to inhaled material. It was aim of this study to examine how such cells respond to PAH exposure and to characterise the immune response. Human primary bronchial epithelial cells (HPBECs) were exposed to Benzo[]pyrene, Benzo[]pyrene, Fluoranthene and Benzo[]fluoranthene for 24 h and a repeat exposure up to 7 days, and examined for global gene expression using RNA-Seq. In addition to increased expression of CYP1A1 and other AHR dependent changes, we identified significant increases in innate and adaptive immune signals including, IL-1A, IL-19, SERPINB2, STAT6, HLA-DMB and HLA-DRA. We also observed increased expression of HMOX1 and NQO1, genes involved in the response to oxidative stress. Immune system related gene expression was differentially induced by each compound with Benzo[]pyrene and Benzo[]fluoranthene demonstrating the most potent responses. Differential induction paralleled the level to which AHR dependent gene expression and oxidative stress markers were induced. We also observed similar levels of gene expression when cells were exposed to organic extracts from diesel exhaust particles. In conclusion, hazard characterisation of responses to PAH exposure in HPBECs highlights specific responses of both innate and adaptive immunity.

Soil microbes are important for public health. Increasing urbanisation is adversely affecting soil microbiota, which may be contributing to the global rise of immune-related diseases. Fungi are key components of urban environments that can be negatively impacted by altered land-use, land-management and climate change, and are implicated in the development and exacerbation of non-communicable diseases such as allergy, asthma and chronic inflammatory conditions. Fungal metagenomics is building knowledge on fungi within different environments (the environmental mycobiome), fungi on and within the human body (the human mycobiome), and their association with disease. Here, we demonstrate the added value of a multi-region metabarcoding approach to analyse soil mycobiomes from five urban greenspaces (lawns, parklands, bareground, young forest and old forest). While results were comparable across the three regions (ITS1, ITS2 and LSU), each identified additional fungal taxa that were unique to the region. Combining the results therefore provided a more comprehensive analysis across all fungal taxonomic ranks, identifying statistically significant differences in the fungal composition of the five soil types. Assignment of fungal taxa into ecological guilds revealed those differences of biological relevance to public health. The greatest differences were between the soil mycobiome of lawns and forests. Of most concern was the significant increase in the known human allergens Alternaria, Bipolaris, Cladosporium and Fusarium within urban lawn and parkland vs forest soils. By improving our understanding of local variations in fungal taxa across urban greenspaces, we have the potential to boost the health of local residents through improved urban planning.

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