Background: Wildfire events are increasing in prevalence in the western United States. Research has found mixed results on the degree to which exposure to wildfire smoke is associated with an increased risk of mortality. Methods: We tested for an association between exposure to wildfire smoke and non-traumatic mortality in Washington State, USA. We characterized wildfire smoke days as binary for grid cells based on daily average PM 2.5 concentrations, from June 1 through September 30, 2006-2017. Wildfire smoke days were defined as all days with assigned monitor concentration above a PM 2.5 value of 20.4 μg/m 3 , with an additional set of criteria applied to days between 9 and 20.4 μg/m 3. We employed a case-crossover study design using conditional logistic regression and time-stratified referent sampling, controlling for humidex. Results: The odds of all-ages non-traumatic mortality with same-day exposure was 1.0% (95% CI: − 1.0-4.0%) greater on wildfire smoke days compared to non-wildfire smoke days, and the previous day's exposure was associated with a 2.0% (95% CI: 0.0-5.0%) increase. When stratified by cause of mortality, odds of same-day respiratory mortality increased by 9.0% (95% CI: 0.0-18.0%), while the odds of same-day COPD mortality increased by 14.0% (95% CI: 2.0-26.0%). In subgroup analyses, we observed a 35.0% (95% CI: 9.0-67.0%) increase in the odds of same-day respiratory mortality for adults ages 45-64. Conclusions: This study suggests increased odds of mortality in the first few days following wildfire smoke exposure. It is the first to examine this relationship in Washington State and will help inform local and state risk communication efforts and decision-making during future wildfire smoke events.

A growing body of literature suggests that restrictive public health measures implemented to control COVID-19 have had negative impacts on physical activity. We examined how Stay Home orders in Houston, New York City, and Seattle impacted outdoor physical activity patterns, measured by daily bicycle and pedestrian count data. We assessed changes in activity levels between the period before and during Stay Home orders. Across all three cities, we found significant changes in bicycle and pedestrian counts from the period before to the period during Stay Home orders. The direction of change varied by location, likely due to differing local contexts and outbreak progression. These results can inform policy around the use of outdoor public infrastructure as the COVID-19 pandemic continues.

Growing evidence links traffic-related air pollution (TRAP) to adverse health effects. We designed an innovative and extensive mobile monitoring campaign to characterize TRAP exposure levels for the Adult Changes in Thought (ACT) study, a Seattle-based cohort. The campaign measured particle number concentration (PNC) to capture ultrafine particles (UFP), black carbon (BC), nitrogen dioxide (NO 2 ), fine particulate matter (PM 2.5 ), and carbon dioxide (CO 2 ) at 309 roadside sites within a large, 1200 land km 2 (463 mi 2 ) area representative of the cohort. We collected about 29 two-minute measurements at each site during all seasons, days of the week, and most times of the day over a 1-year period. Validation showed good agreement between our BC, NO 2 , and PM 2.5 measurements and monitoring agency sites (R 2 = 0.68−0.73). Universal kriging−partial least squares models of annual average pollutant concentrations had cross-validated mean square error-based R 2 (and root mean square error) values of 0.77 (1177 pt/cm 3 ) for PNC, 0.60 (102 ng/m 3 ) for BC, 0.77 (1.3 ppb) for NO 2 , 0.70 (0.3 μg/m 3 ) for PM 2.5 , and 0.51 (4.2 ppm) for CO 2 . Overall, we found that the design of this extensive campaign captured the spatial pollutant variations well and these were explained by sensible land use features, including those related to traffic.

Background Early convalescent plasma transfusion may reduce mortality in patients with non-severe coronavirus disease 2019 (COVID-19). Methods This study emulates a (hypothetical) target trial using observational data from a cohort of United States Veterans admitted to a Department of Veterans Affairs (VA) facility between May 1 and November 17, 2020 with non-severe COVID-19. The intervention was convalescent plasma initiated within 2 days of eligibility. Thirty-day mortality was compared using cumulative incidence curves, risk differences, and hazard ratios estimated from pooled logistic models with inverse probability weighting to adjust for confounding. Results Of 11,269 eligible person-trials contributed by 4,755 patients, 402 trials were assigned to the convalescent plasma group. Forty and 671 deaths occurred within the plasma and non-plasma groups, respectively. The estimated 30-day mortality risk was 6.5% (95% CI: 4.0, 9.7) in the plasma group and 6.2% (95% CI: 5.6, 7.0) in the non-plasma group. The associated risk difference was 0.30% (95% CI -2.30, 3.60) and the hazard ratio was 1.04 (95% CI 0.64,1.62). Conclusion Our target trial emulation estimated no meaningful differences in 30-day mortality between non-severe COVID-19 patients treated and untreated with convalescent plasma.