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Poor air quality is globally the largest environmental health risk. Epidemiological studies have uncovered clear relationships of gaseous pollutants and particulate matter (PM) with adverse health outcomes, including mortality by cardiovascular and respiratory diseases. Studies of health impacts by aerosols are highly multidisciplinary with a broad range of scales in space and time. We assess recent advances and future challenges regarding aerosol effects on health from molecular to global scales through epidemiological studies, field measurements, health-related properties of PM, and multiphase interactions of oxidants and PM upon respiratory deposition. Global modeling combined with epidemiological exposure-response functions indicates that ambient air pollution causes more than four million premature deaths per year. Epidemiological studies usually refer to PM mass concentrations, but some health effects may relate to specific constituents such as bioaerosols, polycyclic aromatic compounds, and transition metals. Various analytical techniques and cellular and molecular assays are applied to assess the redox activity of PM and the formation of reactive oxygen species. Multiphase chemical interactions of lung antioxidants with atmospheric pollutants are crucial to the mechanistic and molecular understanding of oxidative stress upon respiratory deposition. The role of distinct PM components in health impacts and mortality needs to be clarified by integrated research on various spatiotemporal scales for better evaluation and mitigation of aerosol effects on public health in the Anthropocene. [ABSTRACT FROM AUTHOR]

Formation of secondary organic aerosols (SOA) from biogenic volatile organic compounds (BVOC) occurs via O3- and OH-initiated reactions during the day and reactions with NO3 during the night. We explored the effect of these three oxidation conditions on the molecular composition and aqueous photochemistry of model SOA prepared from two common BVOC. A common monoterpene, α-pinene, and sesquiterpene, α-humulene, were used to form SOA in a smog chamber via BVOC + O3, BVOC + NO3, and BVOC + OH + NOx oxidation. Samples of SOA were collected on filters, water-soluble compounds from SOA were extracted in water, and the resulting aqueous solutions were photolyzed to simulate the photochemical aqueous processing of SOA. The extent of change in the molecular level composition of SOA over 4 h of photolysis (approximately equivalent to 64 h of photolysis under ambient conditions) was assessed with high-resolution electrospray ionization mass spectrometry. The analysis revealed significant differences in the molecular composition between SOA formed by the different oxidation pathways. The composition further evolved during photolysis with the most notable change corresponding to the nearly complete removal of nitrogen-containing organic compounds. Hydrolysis of SOA compounds also occurred in parallel with photolysis. The preferential loss of larger SOA compounds during photolysis and hydrolysis made the SOA compounds more volatile on average. This study suggests that aqueous processes may under certain conditions lead to a reduction in the SOA loading as opposed to an increase in SOA loading commonly assumed in the literature. [ABSTRACT FROM AUTHOR]

The neonicotinoid nitenpyram (NPM) is a multifunctional nitroenamine [(R1N)(R2N)C=CHNO2] pesticide. As a nitroalkene, it is structurally similar to other emerging contaminants such as the pharmaceuticals ranitidine and nizatidine. Because ozone is a common atmospheric oxidant, such compounds may be oxidized on contact with air to form new products that have different toxicity compared to the parent compounds. Here we show that oxidation of thin solid films of NPM by gas-phase ozone produces unexpected products, the majority of which do not contain oxygen, despite the highly oxidizing reactant. A further surprising finding is the formation of gas-phase nitrous acid (HONO), a species known to be a major photolytic source of the highly reactive hydroxyl radical in air. The results of application of a kinetic multilayer model show that reaction was not restricted to the surface layers but, at sufficiently high ozone concentrations, occurred throughout the film. The rate constant derived for the O3−NPM reaction is 1 × 10−18 cm3·s−1, and the diffusion coefficient of ozone in the thin film is 9 × 10−10 cm2·s−1. These findings highlight the unique chemistry of multifunctional nitroenamines and demonstrate that known chemical mechanisms for individual moieties in such compounds cannot be extrapolated from simple alkenes. This is critical for guiding assessments of the environmental fates and impacts of pesticides and pharmaceuticals, and for providing guidance in designing better future alternatives. [ABSTRACT FROM AUTHOR]

Water-soluble proteinaceous matter including proteins and free amino acids (FAAs) as well as some other chemical components was analyzed in fine particulate matter (PM2.5) samples collected over a period of one year in rural Guangzhou. Annual averaged protein and total FAAs concentrations were 0.79 ± 0.47 µg m-3 and 0.13 ± 0.05 µg m-3, accounting for 1.9 ± 0.7% and 0.3 ± 0.1% of PM2.5, respectively. Among FAAs, glycine was the most abundant species (19.9%), followed by valine (18.5%), methionine (16.1%), and phenylalanine (13.5%). Both proteins and FAAs exhibited distinct seasonal variations with higher concentrations in autumn and winter than those in spring and summer. Correlation analysis suggests that aerosol proteinaceous matter was mainly derived from intensive agricultural activities, biomass burning, and fugitive dust/soil resuspension. Significant correlations between proteins/FAAs and atmospheric oxidant (O3) indicate that proteins/FAAs may be involved in O3 related atmospheric processes. Our observation confirms that ambient FAAs could be degraded from proteins under the influence of O3, and the stoichiometric coefficients of the reactions were estimated for FAAs and glycine. This finding provides a possible pathway for the production of aerosol FAAs in the atmosphere, which will improve the current understanding on atmospheric processes of proteinaceous matter. [ABSTRACT FROM AUTHOR]

Emissions from biomass burning are a significant source of brown carbon (BrC) in the atmosphere. In this study, we investigate the molecular composition of freshly emitted biomass burning organic aerosol (BBOA) samples collected during test burns of sawgrass, peat, ponderosa pine, and black spruce. We demonstrate that both the BrC absorption and the chemical composition of light-absorbing compounds depend significantly on the type of biomass fuels. Common BrC chromophores in the selected BBOA samples include nitro-aromatics, polycyclic aromatic hydrocarbon derivatives, and polyphenols spanning a wide range of molecular weights, structures, and light absorption properties. A number of biofuel-specific BrC chromophores are observed, indicating that some of them may be used as source-specific markers of BrC. On average, ~50% of the light absorption in the solvent-extractable fraction of BBOA can be attributed to a limited number of strong BrC chromophores. The absorption coefficients of BBOA are affected by solar photolysis. Specifically, under typical atmospheric conditions, the 300 nm absorbance decays with a half-life of ~16 h. A "molecular corridor" analysis of the BBOA volatility distribution suggests that many BrC compounds in the fresh BBOA have low saturation mass concentration (<1 µg mâ€"3) and will be retained in the particle phase under atmospherically relevant conditions. [ABSTRACT FROM AUTHOR]