Development of a standardized in vitro approach to evaluate microphysical, chemical, and toxicological properties of combustion-derived fine and ultrafine particles.

Ultrafine particles represent a growing concern in the public health community but their precise role in many illnesses is still unknown. This lack of knowledge is related to the experimental difficulty in linking their biological effects to their multiple properties, which are important determinants of toxicity. Our aim is to propose an interdisciplinary approach to study fine (FP) and ultrafine (UFP) particles, generated in a controlled manner using a miniCAST (Combustion Aerosol Standard) soot generator used with two different operating conditions (CAST1 and CAST3). The chemical characterization was performed by an untargeted analysis using ultra-high resolution mass spectrometry. In conjunction with this approach, subsequent analysis by gas chromatography-mass spectrometry (GC-MS) was performed to identify polycyclic aromatic hydrocarbons (PAH). CAST1 enabled the generation of FP with a predominance of small PAH molecules, and CAST3 enabled the generation of UFP, which presented higher numbers of carbon atoms corresponding to larger PAH molecules. Healthy normal human bronchial epithelial (NHBE) cells differentiated at the air-liquid interface (ALI) were directly exposed to these freshly emitted FP and UFP. Expression of MUC5AC, FOXJ1, OCLN and ZOI as well as microscopic observation confirmed the ciliated pseudostratified epithelial phenotype. Study of the mass deposition efficiency revealed a difference between the two operating conditions, probably due to the morphological differences between the two categories of particles. We demonstrated that only NHBE cells exposed to CAST3 particles induced upregulation in the gene expression of IL-8 and NQO1. This approach offers new perspectives to study FP and UFP with stable and controlled properties.

Ultrafine Particles Issued from Gasoline-Fuels and Biofuel Surrogates Combustion: A Comparative Study of the Physicochemical and In Vitro Toxicological Effects.

Gasoline emissions contain high levels of pollutants, including particulate matter (PM), which are associated with several health outcomes. Moreover, due to the depletion of fossil fuels, biofuels represent an attractive alternative, particularly second-generation biofuels (B2G) derived from lignocellulosic biomass. Unfortunately, compared to the abundant literature on diesel and gasoline emissions, relatively few studies are devoted to alternative fuels and their health effects. This study aimed to compare the adverse effects of gasoline and B2G emissions on human bronchial epithelial cells. We characterized the emissions generated by propane combustion (CAST1), gasoline Surrogate, and B2G consisting of Surrogate blended with anisole (10%) (S+10A) or ethanol (10%) (S+10E). To study the cellular effects, BEAS-2B cells were cultured at air-liquid interface for seven days and exposed to different emissions. Cell viability, oxidative stress, inflammation, and xenobiotic metabolism were measured. mRNA expression analysis was significantly modified by the Surrogate S+10A and S+10E emissions, especially CYP1A1 and CYP1B1. Inflammation markers, IL-6 and IL-8, were mainly downregulated doubtless due to the PAHs content on PM. Overall, these results demonstrated that ultrafine particles generated from biofuels Surrogates had a toxic effect at least similar to that observed with a gasoline substitute (Surrogate), involving probably different toxicity pathways.

Direct Inlet Probe Atmospheric Pressure Photo and Chemical Ionization Coupled to Ultrahigh Resolution Mass Spectrometry for the Description of Lignocellulosic Biomass.

Lignocellulosic biomass, in particular wood, is a complex mixture containing cellulose, hemicellulose, lignin, and other trace compounds. Chemical analysis of these biomasses, especially lignin components, is a challenge. Lignin is a highly reticulated polymer that is poorly soluble and usually requires chemical, enzymatic, or thermal degradation for its analysis. Here, we studied the thermal degradation of lignocellulosic biomass using a direct insertion probe (DIP). The DIP was used with two ionization sources: atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) coupled to ultrahigh-resolution mass spectrometry. Beech lignocellulosic biomass samples were used to develop the DIP-APCI/APPI methodology. Two other wood species (maple and oak) were analyzed after optimization of DIP parameters. The two ionization sources were compared at first and showed different responses toward beech samples, according to the source specificity. APPI was more specific to lignin degradation compounds, whereas APCI covered a larger variety of oxygenated compounds, e.g., fatty acids and polyphenolics compounds, in addition to lignin degradation products. The study of the thermodesorption profile gave information on the different steps of lignocellulosic biomass pyrolysis. The comparison of the three feed sample types (oak, maple, and beech), using principal component analysis (PCA) with DIP-APCI experiments, showed molecular level differences between beech wood pellets and the two other wood species (maple and oak).

Particulate inorganic salts and trace element emissions of a domestic boiler fed with five commercial brands of wood pellets.

Pellet stoves arouse a real interest from consumers because they are perceived as a renewable and carbon neutral energy. However, wood combustion can contribute significantly to air pollution, in particular through the emission of particulate matter (PM). In this article, five brands of wood pellets were burnt under optimal combustion conditions and trace element and inorganic salt emission factors (EFs) in PM were determined. Results show that a significant proportion of metals such as lead, zinc, cadmium, and copper initially present in pellets were emitted into the air during combustion with 20 ± 6%, 31 ± 12%, and 19 ± 6% of the initial content respectively for Zn, Pb, and Cd. The median emission factors for Pb, Cu, Cd, As, Zn, and Ni were respectively 188, 86, 9.3, 8.7, 2177, and 3.5 µg kg-1. The inorganic fraction of the PM emissions was dominated by K+, SO42-, and Cl- with respective EFs of 33, 28.7, and 11.2 mg kg-1. Even taking into account a consumption of 40.1 million tons by 2030 in the EU, the resulting pollution in terms of heavy metal emissions remains minimal in comparison with global emissions in the EU.