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Wildfires have become an important source of particulate matter (PM2.5 < 2.5-µm diameter), leading to unhealthy air quality index occurrences in the western United States. Since people mainly shelter indoors during wildfire smoke events, the infiltration of wildfire PM2.5 into indoor environments is a key determinant of human exposure and is potentially controllable with appropriate awareness, infrastructure investment, and public education. Using time-resolved observations outside and inside more than 1,400 buildings from the crowdsourced PurpleAir sensor network in California, we found that the geometric mean infiltration ratios (indoor PM2.5 of outdoor origin/outdoor PM2.5) were reduced from 0.4 during non-fire days to 0.2 during wildfire days. Even with reduced infiltration, the mean indoor concentration of PM2.5 nearly tripled during wildfire events, with a lower infiltration in newer buildings and those utilizing air conditioning or filtration.

Byline: Deep. Sengupta, Ashish. Bindra, Indu. Kapoor, Purva. Mathur, Deepak. Gupta, Maroof. Khan Background: There is scant literature comparing high tidal volume ventilation (HTV) over low tidal volume (LTV) ventilation [...]

Byline: Siddharth. Chavali, Girija. Rath, Deep. Sengupta, Surya. Dube Formal brainstem reflex testing remains one of the most important procedures in identification and evaluation of patients who meet clinical criteria [...]

Glasgow Coma Scale-Pupils (GCS-P) score has been found to be strongly related to in-hospital mortality in retrospective studies. We hypothesized that GCS-P would be better prognosticator than Glasgow Coma Scale (GCS) in patients with traumatic brain injury (TBI). In this prospective, multicentric, observational study, GCS and GCS-P scores were noted in adult TBI patients at ICU admission. Demographic variables, relevant clinical history, clinical/radiological findings and ICU complications were also noted. Extended Glasgow Outcome scale was noted at hospital discharge and at 6 months post-injury. Logistic regression analysis was carried out to estimate the odds for poor outcome adjusted for covariates. Sensitivity, specificity, area under curve (AUC) and odds ratio are reported for poor outcome at estimated cutoff point. A total of 573 patients were included in this study. The predictive power for mortality, shown by the AUC, was 0.81 [95% CI: 0.77–0.85] for GCS and 0.81 [95% CI: 0.77–0.86] for GCS-P score, both being comparable. Similarly, the predictive ability for outcome at discharge and 6 months, the AUC-ROC for both GCS and GCS-P were comparable. GCS-P is a good predictor of mortality and poor outcome. However, the predictive performance of GCS and GCS-P for in-hospital mortality and functional outcome at discharge and at 6 months remains comparable. [ABSTRACT FROM AUTHOR]

Wildfires have become an important source of particulate matter (PM2.5 < 2.5-µm diameter), leading to unhealthy air quality index occurrences in the western United States. Since people mainly shelter indoors during wildfire smoke events, the infiltration of wildfire PM2.5 into indoor environments is a key determinant of human exposure and is potentially controllable with appropriate awareness, infrastructure investment, and public education. Using time-resolved observations outside and inside more than 1,400 buildings from the crowdsourced PurpleAir sensor network in California, we found that the geometric mean infiltration ratios (indoor PM2.5 of outdoor origin/outdoor PM2.5) were reduced from 0.4 during non-fire days to 0.2 during wildfire days. Even with reduced infiltration, the mean indoor concentration of PM2.5 nearly tripled during wildfire events, with a lower infiltration in newer buildings and those utilizing air conditioning or filtration. [ABSTRACT FROM AUTHOR]

Semi-volatile organic compounds (SVOCs) emitted from open biomass-burning (BB) can contribute to chemical and physical properties of atmospheric aerosols and also may cause adverse health effects. The polar fraction of SVOCs constitutes a significant part of BB organic aerosols, and thus it is important to characterize the chemical composition and reactivity of this fraction. In this study, globally and regionally important representative fuels (Alaskan peat, Moscow peat, Pskov peat, Eucalyptus, Malaysian peat, and Malaysian agricultural peat) were burned under controlled conditions using the combustion chamber facility at the Desert Research Institute (DRI). Gas- and particulate-phase biomass-burning emissions were aged in an oxidation flow reactor (OFR) to mimic 5-7 days of atmospheric aging. Fresh and OFR-aged biomass-burning aerosols were collected on Teflon impregnated glass fiber filters (TIGF) in tandem with XAD resin media for organic compound (OC) speciation. The polar fraction extracted with dichloromethane and acetone was analyzed with gas chromatography mass spectrometry (GC-MS) for 84 polar organic compounds - including mono and dicarboxylic acids, methoxylated phenols, aromatic acids, anhydrosugars, resin acids, and sterols. For all these compounds, fuel-based emission factors (EFs) were calculated for fresh and OFR-aged samples. The carbon mass of the quantified polar compounds was found to constitute 5 % to 7 % of the total OC mass. High abundance of methoxyphenols (239 mg kg-1 for Pskov peat; 22.6 % of total GC-MS characterized mass) and resin acids (118 mg kg-1 for Pskov peat; 14.5 % of total GC-MS characterized mass) was found in peat burning emissions (smoldering combustion). Concentration of some organic compounds (e.g., tetracosanoic acid) with molecular weight (MW) above 350 g mol-1 decreased after the OFR aging, while abundances of low MW compounds (e.g., hexanoic acid) increased. This indicated a significant extent of fragmentation reactions in the OFR. Methoxyphenols decreased after OFR aging, while a significant increase (3.7 to 8.6 times) in abundance of dicarboxylic acids emission factors (EFs), especially maleic acid (10 to 60 times), was observed. EFs for fresh and ratios from fresh-to-aged BB samples reported in this study can be used to perform source apportionment and predict processes occurring during atmospheric transport. [ABSTRACT FROM AUTHOR]

Light-absorbing organic carbon aerosol – colloquially known as brown carbon (BrC) – is emitted from combustion processes and has a brownish or yellowish visual appearance, caused by enhanced light absorption at shorter visible and ultraviolet wavelengths (0.3 μm ≲ λ ≲ 0.5 μm). Recently, optical properties of atmospheric BrC aerosols have become the topic of intense research, but little is known about how BrC deposition onto snow surfaces affects the spectral snow albedo, which can alter the resulting radiative forcing and in-snow photochemistry. Wildland fires in close proximity to the cryosphere, such as peatland fires that emit large quantities of BrC, are becoming more common at high latitudes, potentially affecting nearby snow and ice surfaces. In this study, we describe the artificial deposition of BrC aerosol with known optical, chemical, and physical properties onto the snow surface and we monitor its spectral radiative impact and compare it directly to modeled values. First, using small-scale combustion of Alaskan peat, BrC aerosols were artificially deposited onto the snow surface. UV-vis absorbance and total organic carbon (TOC) concentration of snow samples were measured for samples with and without artificial BrC deposition. These measurements were used to estimate the imaginary part of the refractive index of deposited BrC aerosol with a volume mixing rule. Single particle optical properties were calculated using Mie theory, and these values were used to show that the measured spectral snow albedo of snow with deposited BrC was in general agreement with modeled spectral snow albedo using calculated BrC optical properties. The instantaneous radiative forcing by impurities present in the snow before the deposition experiments was found to increase the instantaneous radiative forcing at the surface of the natural snow at our site by 1.23 (+0.14/−0.11) W m−2 per ppm of BrC deposited. However, we estimate that deposition onto a clean snowpack without light-absorbing impurities would have resulted in a more than twice as large instantaneous radiative forcing of 2.68 (+0.27/−0.22) W m−2 per ppm of BrC deposited. [ABSTRACT FROM AUTHOR]