Designing better cloth masks: The effect of fabric and attachment-style on discomfort

Cloth masks are a tool for controlling community transmission during pandemics, as well as during other outbreak situations. However, cloth masks vary in their designs, and the consequences of this variability for their effectiveness as source control have received little attention, particularly in terms of user discomfort and problematic mask-wearing behaviors. In the present studies, common design parameters of cloth masks were systematically varied to ascertain their effect(s) on the subjective discomfort and frequency of problematic mask-wearing behaviors, which detract from the effectiveness of cloth masks as source control. The type of fabric comprising a mask (flannel or twill made of 100% cotton) and the attachment-style of a mask (i.e., ear loops or fabric ties) were varied in adults (18 to 65 years) and children (ages 6 to 11 years). For adults, ear loops were less comfortable than ties (p = .035) and were associated with greater face- (p = .005) and mask-touching (p = .001). Children, however, found flannel masks to be more breathable than twill masks (p = .007) but touched their masks more frequently when wearing a mask made of flannel than twill (p = .033). Common design parameters of cloth masks not only affect user discomfort and behavior but do so differently in adults and children. To improve the effectiveness of cloth masks as source control, the present studies highlight the importance of measuring the effect(s) of design decisions on user discomfort and behavior in different populations.</p

Protein Cross-Linking and Oligomerization through Dityrosine Formation upon Exposure to Ozone

Air pollution is a potential driver for the increasing prevalence of allergic disease, and post-translational modification by air pollutants can enhance the allergenic potential of proteins. Here, the kinetics and mechanism of protein oligomerization upon ozone (O₃) exposure were studied in coated-wall flow tube experiments at environmentally relevant O₃ concentrations, relative humidities and protein phase states (amorphous solid, semisolid, and liquid). We observed the formation of protein dimers, trimers, and higher oligomers, and attribute the cross-linking to the formation of covalent intermolecular dityrosine species. The oligomerization proceeds fast on the surface of protein films. In the bulk material, reaction rates are limited by diffusion depending on phase state and humidity. From the experimental data, we derive a chemical mechanism and rate equations for a kinetic multilayer model of surface and bulk reaction enabling the prediction of oligomer formation. Increasing levels of tropospheric O₃ in the Anthropocene may promote the formation of protein oligomers with enhanced allergenicity and may thus contribute to the increasing prevalence of allergies

Proteins and Amino Acids in Fine Particulate Matter in Rural Guangzhou, Southern China: Seasonal Cycles, Sources, and Atmospheric Processes

Water-soluble proteinaceous matter including proteins and free amino acids (FAAs) as well as some other chemical components was analyzed in fine particulate matter (PM_2.5) 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 PM_2.5, 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

Collection of Nitrogen Dioxide for Nitrogen and Oxygen Isotope DeterminationLaboratory and Environmental Chamber Evaluation

The family of atmospheric oxides of nitrogen, NOy (e.g., nitrogen oxides (NOx) + nitric acid (HNO3) + nitrous acid (HONO) + peroxyacetyl nitrate (PAN) + particulate nitrate (pNO3–) + other), have an influential role in atmospheric chemistry, climate, and the environment. The nitrogen (δ15N) and oxygen (δ18O and Δ17O) stable isotopes of NOy are novel tools for potentially tracking emission sources and quantifying oxidation chemistry. However, there is a lack of well-established methods, particularly for speciated gas-phase components of NOy, to accurately quantify δ15N, δ18O, and Δ17O. This work presents controlled laboratory experiments and complex chamber α-pinene/NOx oxidation experiments of a sampling apparatus constructed for the simultaneous capture of multiple NOy species for isotope analysis using a series of coated denuders, with a focus on nitrogen dioxide (NO2•). The laboratory tests indicate complete NO2• capture for the targeted concentration of 15 ppbv for at least 24 h collections at 10 liters per minute, with δ15N and δ18O precisions of ±1.3‰ and 1.0‰, respectively, and minimal (2.2% ± 0.1%) NO2• collection on upstream denuders utilized for the capture of HNO3 and other acidic gases. The multispecies NOy collection system showed excellent concentration correlations with online instrumentation for both HNO3 and NO2• and isotope reproducibility of ±1.7‰, ±1.8‰, and ±0.7‰ for δ15N, δ18O, and Δ17O, respectively, for replicate experiments and highly time-resolved collections. This work demonstrates a new method that can enable the simultaneous collection of HNO3 and NO2• for accurate quantification of concentration and isotopic composition