Inferred vehicular emissions at a near-road site: Impacts of COVID-19 restrictions, traffic patterns, and ambient air temperature.

Vehicles are a major source of anthropogenic emissions of carbon monoxide (CO), nitrogen oxides (NOx), and black carbon (BC). CO and NOx are known to be harmful to human health and contribute to ozone formation, while BC absorbs solar radiation that contributes to global warming and also has negative impacts on human health and visibility. Travel restrictions implemented during the COVID-19 pandemic provide researchers the opportunity to study the impact of large, on-road traffic reductions on local air quality. Traffic counts collected along Interstate-95, a major eight-lane highway in Maryland (US), reveal a 60% decrease in passenger car totals and an 8.6% (combination-unit) and 21% (single-unit) decrease in truck traffic counts in April 2020 relative to prior Aprils. The decrease in total on-road vehicles led to the near-elimination in stop-and-go traffic and a 14% increase in the mean vehicle speed during April 2020. Ambient near-road (NR) BC, CO, NOx, and carbon dioxide (CO2) measurements were used to determine vehicular emission ratios (ΔBC/ΔCO, ΔBC/ΔCO2, ΔNOx/ΔCO, ΔNOx/ΔCO2, and ΔCO/ΔCO2), with each ratio defined as the slope value of a linear regression performed on the concentrations of two pollutants within an hour. A decrease of up to a factor of two in ΔBC/ΔCO, ΔBC/ΔCO2, ΔNOx/ΔCO2, and in the fraction of on-road diesel vehicles from weekdays to weekends shows diesel vehicles to be the dominant source of BC and NOx emissions at this NR site. We estimate up to a 70% reduction in BC emissions in April 2020 compared to earlier years, and attribute much of this to lower diesel BC emissions resulting from improvements in traffic flow and fewer instances of acceleration and braking. Future efforts to reduce vehicular BC emissions should focus on improving traffic flow or turbocharger lag within diesel engines. Inferred BC emissions from the NR site also depend on ambient temperature, with an increase of 54% in ΔBC/ΔCO from -5 to 20 °C during the cold season, similar to previous studies that reported increasing BC emissions with rising temperature. The default setting of MOVES3, the current version of the mobile emission model used by the US EPA, does not adjust hot-running BC emissions for ambient temperature. Future work will focus on improving the accuracy of mobile emissions in air quality modeling by incorporating the effects of temperature and traffic flow in the system used to generate mobile emissions input for commonly used air quality models.

Acute ambient air pollution exposure and placental Doppler results in the NICHD fetal growth studies - Singleton cohort.

BACKGROUND: Increased placental vascular resistance is a proposed mechanism by which air pollution exposure during pregnancy lowers birth weight and increases pregnancy-induced hypertensive disorders. OBJECTIVE: To examine the impact of acute air pollution exposure during pregnancy on uterine and umbilical artery Doppler indicators of placental vascular resistance. METHODS: After a first ultrasound to confirm gestational age, 2562 pregnant women recruited in 12 clinics throughout the United States underwent up to five standardized ultrasounds with Doppler measurements. Exposures to 11 air pollutants were estimated for the hour of ultrasound and each of the 2 h prior to ultrasound at the clinics using the National Air Quality Forecast Capability reanalysis products. We used mixed logistic regression to study the longitudinal odds ratio (OR) of any, uni- or bi-lateral systolic and diastolic uterine artery notching compared to no notching and the longitudinal OR of abnormal end diastolic flow of the umbilical artery compared to forward flow. Uterine and umbilical artery resistance indexes were studied using linear mixed models. RESULTS: Each inter-quartile range (IQR) increase of particulate matter < 2.5 µm, nitrate, ammonium, primary organic matter (POM) and nitrogen dioxide during the hour of ultrasound was associated with a decreased risk of unilateral systolic notch and with increased resistance index of the left uterine artery. For the umbilical artery, each IQR increase in ozone was associated with decreased resistance index (b: -0.26, 95 % CI: -0.52, -0.01) and with a decreased risk of abnormal end diastolic flow (OR: 0.36, 95 % CI: 0.14, 0.94); while each IQR increase of elemental carbon and POM was associated with increased risk of abnormal end diastolic flow (OR: 1.47, 95 % CI: 1.02, 2.13 and OR: 1.67, 95 % CI: 1.17, 2.39, respectively). DISCUSSION: Our results suggest acute air pollution exposure may influence placental vascular resistance.

Expected ozone benefits of reducing nitrogen oxide (NOx) emissions from coal-fired electricity generating units in the eastern United States.

On hot summer days in the eastern United States, electricity demand rises, mainly because of increased use of air conditioning. Power plants must provide this additional energy, emitting additional pollutants when meteorological conditions are primed for poor air quality. To evaluate the impact of summertime NOx emissions from coal-fired electricity generating units (EGUs) on surface ozone formation, we performed a series of sensitivity modeling forecast scenarios utilizing EPA 2018 version 6.0 emissions (2011 base year) and CMAQ v5.0.2. Coal-fired EGU NOx emissions were adjusted to match the lowest NOx rates observed during the ozone seasons (April 1-October 31) of 2005-2012 (Scenario A), where ozone decreased by 3-4 ppb in affected areas. When compared to the highest emissions rates during the same time period (Scenario B), ozone increased ∼4-7 ppb. NOx emission rates adjusted to match the observed rates from 2011 (Scenario C) increased ozone by ∼4-5 ppb. Finally in Scenario D, the impact of additional NOx reductions was determined by assuming installation of selective catalytic reduction (SCR) controls on all units lacking postcombustion controls; this decreased ozone by an additional 2-4 ppb relative to Scenario A. Following the announcement of a stricter 8-hour ozone standard, this analysis outlines a strategy that would help bring coastal areas in the mid-Atlantic region closer to attainment, and would also provide profound benefits for upwind states where most of the regional EGU NOx originates, even if additional capital investments are not made (Scenario A). IMPLICATIONS: With the 8-hr maximum ozone National Ambient Air Quality Standard (NAAQS) decreasing from 75 to 70 ppb, modeling results indicate that use of postcombustion controls on coal-fired power plants in 2018 could help keep regions in attainment. By operating already existing nitrogen oxide (NOx) removal devices to their full potential, ozone could be significantly curtailed, achieving ozone reductions by up to 5 ppb in areas around the source of emission and immediately downwind. Ozone improvements are also significant (1-2 ppb) for areas affected by cross-state transport, especially Mid-Atlantic coast regions that had struggled to meet the 75 ppb standard.

Formaldehyde in the Tropical Western Pacific: Chemical sources and sinks, convective transport, and representation in CAM-Chem and the CCMI models.

Formaldehyde (HCHO) directly affects the atmospheric oxidative capacity through its effects on HOx. In remote marine environments, such as the Tropical Western Pacific (TWP), it is particularly important to understand the processes controlling the abundance of HCHO because model output from these regions is used to correct satellite retrievals of HCHO. Here, we have used observations from the CONTRAST field campaign, conducted during January and February 2014, to evaluate our understanding of the processes controlling the distribution of HCHO in the TWP as well as its representation in chemical transport/climate models. Observed HCHO mixing ratios varied from ~500 pptv near the surface to ~75 pptv in the upper troposphere. Recent convective transport of near surface HCHO and its precursors, acetaldehyde and possibly methyl hydroperoxide, increased upper tropospheric HCHO mixing ratios by ~33% (22 pptv); this air contained roughly 60% less NO than more aged air. Output from the CAM-Chem chemistry transport model (2014 meteorology) as well as nine chemistry climate models from the Chemistry-Climate Model Initiative (free-running meteorology) are found to uniformly underestimate HCHO columns derived from in situ observations by between 4 and 50%. This underestimate of HCHO likely results from a near factor of two underestimate of NO in most models, which strongly suggests errors in NOx emissions inventories and/or in the model chemical mechanisms. Likewise, the lack of oceanic acetaldehyde emissions and potential errors in the model acetaldehyde chemistry lead to additional underestimates in modeled HCHO of up to 75 pptv (~15%) in the lower troposphere.

Anoplasty for low anorectal malformation.

BACKGROUND: The presence of a slightly anterior, stenotic anus is a low anorectal malformation. It is a type of rectoperineal fistula. The cardinal symptoms are constipation and straining at stool. Hendren described a technically simple anoplasty for this condition in 1978. Controversy about terminology has led to a lack of clarity about this condition. METHODS: Clinical data were reviewed about the authors' patients, who had Hendren anoplasty, from 2009 to 2015. Followup data were obtained from office visits and telephone interviews with families and primary care doctors. RESULTS: Seven patients (4 boys) presented with intractable constipation. All had a stenotic anal orifice, located anterior to the center of the anal wink, within the pigmented perianal skin. In 4 of 7 cases, the lesion was not recognized at birth. Anoplasty was performed at a median age of 8months (range 6-28). Late followup information was obtained on six of the seven patients at a median of 32months (range 28-61). Four reported no or minimal laxative requirement and two reported daily laxative use but good symptom control. CONCLUSIONS: Low anorectal malformation/rectoperineal fistula may be overlooked in the newborn. When symptomatic, it may be corrected by a simple anoplasty with excellent results.

A pervasive role for biomass burning in tropical high ozone/low water structures.

Air parcels with mixing ratios of high O3 and low H2O (HOLW) are common features in the tropical western Pacific (TWP) mid-troposphere (300-700 hPa). Here, using data collected during aircraft sampling of the TWP in winter 2014, we find strong, positive correlations of O3 with multiple biomass burning tracers in these HOLW structures. Ozone levels in these structures are about a factor of three larger than background. Models, satellite data and aircraft observations are used to show fires in tropical Africa and Southeast Asia are the dominant source of high O3 and that low H2O results from large-scale descent within the tropical troposphere. Previous explanations that attribute HOLW structures to transport from the stratosphere or mid-latitude troposphere are inconsistent with our observations. This study suggest a larger role for biomass burning in the radiative forcing of climate in the remote TWP than is commonly appreciated.

The Effect of Representing Bromine from VSLS on the Simulation and Evolution of Antarctic Ozone.

We use the Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM), a contributor to both the 2010 and 2014 WMO Ozone Assessment Reports, to show that inclusion of 5 parts per trillion (ppt) of stratospheric bromine (Bry) from very short-lived substances (VSLS) is responsible for about a decade delay in ozone hole recovery. These results partially explain the significantly later recovery of Antarctic ozone noted in the 2014 report, as bromine from VSLS was not included in the 2010 Assessment. We show multiple lines of evidence that simulations that account for VSLS Bry are in better agreement with both total column BrO and the seasonal evolution of Antarctic ozone reported by the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite. In addition, the near zero ozone levels observed in the deep Antarctic lower stratospheric polar vortex are only reproduced in a simulation that includes this Bry source from VSLS.

CAMx Ozone Source Attribution in the Eastern United States using Guidance from Observations during DISCOVER-AQ Maryland.

A Comprehensive Air-Quality Model with Extensions (CAMx) version 6.10 simulation was assessed through comparison with data acquired during NASA's 2011 DISCOVER-AQ Maryland field campaign. Comparisons for the baseline simulation (CB05 chemistry, EPA 2011 National Emissions Inventory) show a model overestimate of NOy by +86.2% and an underestimate of HCHO by -28.3%. We present a new model framework (CB6r2 chemistry, MEGAN v2.1 biogenic emissions, 50% reduction in mobile NOx, enhanced representation of isoprene nitrates) that better matches observations. The new model framework attributes 31.4% more surface ozone in Maryland to electric generating units (EGUs) and 34.6% less ozone to on-road mobile sources. Surface ozone becomes more NOx-limited throughout the eastern United States compared to the baseline simulation. The baseline model therefore likely underestimates the effectiveness of anthropogenic NOx reductions as well as the current contribution of EGUs to surface ozone.

Midterm results of a novel technique to salvage autogenous dialysis access in aneurysmal arteriovenous fistulas.

PURPOSE: Over the last decade, K-DOQI guidelines have increasingly emphasized the importance of autogenous arteriovenous fistulas (AVF) for dialysis access. A complication of AVF is aneurysmal dilatation with a subset developing massive diffuse aneurysm. Treatment of massive aneurysmal AVF generally involves either ligation or resection with use of prosthetic interposition. To maintain an all-autogenous access, we developed a procedure to treat massive aneurysmal AVF in which the luminal diameter is reduced, excess length is resected, and the new reconstructed AVF is re-tunneled for continued use. The purpose of this study is to examine the midterm outcomes of this novel procedure. METHODS: Over a 4-year period, the reduction/revision procedure was performed on 19 patients with an AVF diameter of 4-7 cm. Indications for operation were thrombosis, skin breakdown, infection, bleeding, and/or poor flow. Revision was performed by resecting redundant length, reducing diameter, and then reconstructing the fistula. RESULTS: The median patient age was 47, interquartile range (IQR) 29. There were 13 men and 6 women. The median follow-up was 23 months, IQR 22. The median primary patency was 14 months, IQR 24. The median secondary patency was 16.5 months, IQR 26. Two patients died, one AVF thrombosed, and two were ligated secondary to infection. Three fistulae developed a stenosis that was treated with percutaneous angioplasty. There are no recurrent aneurysms to date. CONCLUSION: Surgical resection of excess length, reduction of luminal diameter, and reconstruction is a viable option for the treatment of complicated massive diffusely aneurysmal AVF. This technique offers the ability to maintain the benefits of an all autogenous dialysis access while conserving future dialysis sites.

Hemodialysis-related steal syndrome: predictive factors and response to treatment with the distal revascularization-interval ligation procedure.

Hand ischemia due to steal causes major disability in affected members of the hemodialysis population. Between February 2000 and March 2007, 24 patients aged 37-77 years were identified who developed hand ischemia distal to a hemodialysis access and required a distal revascularization-interval ligation (DRIL) procedure. Of the 24 patients, 22 (92%) were diabetic, 14 (58%) were women, 7 (29%) had prosthetic grafts, and 17 (71%) had fistulas, all originating from the brachial artery. Duration between the initial dialysis access and the DRIL procedures ranged 12 hours to 10 months. Conduits used were saphenous vein in 13 (54%) cases, cephalic vein in 3 (12%) cases, basilic vein in 5 (21%) cases, and prosthetic grafts in 3 (12%) cases. There were no operative deaths. Improved blood flow and relief of symptoms were observed in 23 (96%) patients. The procedure failed early in one patient who had thrombosis of a prosthetic graft. Two patients required digital amputations. At a median follow-up of 50 months, 14 (58%) patients died using the access requiring the DRIL, 2 (8%) did not require dialysis, 3 (12%) were using a new access, and 5 (21%) were still using the access that had required the DRIL. In late follow-up, only one DRIL bypass required revision and the remainder were patent. One patient developed an ischemic hand 5 years after his DRIL procedure despite a patent bypass. The development of ischemic steal requiring performance of a DRIL procedure is most likely to occur in diabetic patients with dialysis access originating from the brachial artery. The procedure is effective in ameliorating symptoms while preserving the vascular access. The high long-term mortality rate observed in this series underscores the fact that patients requiring a DRIL procedure represent a subset of dialysis patients with advanced diabetic vascular disease and a limited life expectancy. Despite the effectiveness of the DRIL procedure, efforts should be concentrated on prevention of ischemic steal in order to lessen the morbidity and expense of this condition in the dialysis population.

Financial and operational impact of a direct-from-PACU discharge pathway for laparoscopic cholecystectomy patients.

BACKGROUND: We assessed the operational and financial impact of discharging laparoscopic cholecystectomy (LC) patients directly from the postanesthetic care unit (PACU) in comparison with post-transfer discharge from a hospital bed in a busy academic hospital. METHODS: We retrospectively compared 6 months of performance (bed utilization; recovery room and hospital length of stay; complications; readmissions; hospital costs, revenue, and margin) after implementation of PACU discharges (case patients) to the corresponding 6 months in the prior year (control patients). RESULTS: After implementation, 66% of LC case patients were discharged on the day of surgery, compared with 29% in the control group (P < .05). Eighty percent of the day-of-surgery discharges were directly from the PACU. Shifting to PACU discharge saved 1 in-hospital bed transfer and 1 bed-day for each PACU discharge. Recovery room length of stay for PACU discharge patients was 26% longer than for hospital discharge patients (P = NS). Average hospital length of stay for all patients discharged on the day of surgery was 3.2 hours shorter (P < .05) for case patients (80% PACU discharge) than for control patients. There were no readmissions in the PACU discharge group and no difference in complications. While costs, revenue, and net margin for PACU discharge patients were reduced by 40% to 50% (P < .02) relative to floor discharge patients, the hospital's net margin for the combined case patient group was preserved relative to the control group. CONCLUSIONS: PACU discharge of LC patients significantly reduces bed utilization, decreases in-hospital transfers, and allows congested hospitals to better accommodate patient care needs and generate additional revenue.

Chronic traumatic and congenital diaphragmatic hernias: presentation and surgical management.

BACKGROUND: The diagnosis of chronic diaphragmatic hernias, whether due to congenital defects or trauma, may be difficult to make and may rely on clinical suspicion in the setting of persistent nondiagnostic radiographic findings. Repair is indicated to avoid catastrophic cardiopulmonary compromise and/or incarceration of abdominal organs. STUDY OBJECTIVES: To review the varied presentations and treatment of chronic diaphragmatic hernia. DESIGN: Retrospective review. SETTING: University of Washington and Harborview Medical Center, Seattle, Washington. PATIENTS: Between 1997 and 2001, nine patients presented with chronic diaphragmatic hernia (two congenital cases, seven post-traumatic cases). Four cases involved the right diaphragm. The following clinical features were noted: asymptomatic, chest radiograph showing bowel herniation (n=1); chest wall mass (n=1); asymptomatic with the chest radiograph showing marked elevation of hemidiaphragm (n=1); dyspnea with the chest radiograph showing marked elevation of hemidiaphragm (n=1); diarrhea and heartburn (n=1); generalized gastrointestinal upset (n=1); recurrent pneumonia (n=2); recurring effusions (n=4); and dyspnea on exertion (n=5). INTERVENTIONS: Diagnosis was confirmed by chest radiograph in two patients, chest computed tomography scan in one patient, barium studies in three patients and thoracoscopy in three patients. All hernias were repaired via thoracotomy, and two hernias were repaired with artificial patch. CONCLUSIONS: Patients with chronic diaphragmatic hernias present with a variety of symptoms and radiographic findings. When radiology or symptoms suggest bowel involvement, barium studies are appropriate. In other cases, chest computed tomography scans and/or thoracoscopy are useful. Repair is accomplished through the ipsilateral chest, with primary repair of the diaphragm preferred over patch repair.