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Background The coronavirus disease 2019 (COVID‐19) pandemic has highlighted safety concerns surrounding possible aerosol‐generating procedures, but comparative data on the smallest particles capable of transmitting this virus remain limited. We evaluated the effect of nasal endoscopy on aerosol concentration and the role of a high‐efficiency particulate air (HEPA) filter in reducing aerosol concentration. Methods Otolaryngology patients were prospectively enrolled in an outpatient, cross‐sectional study. Demographic information and clinic room characteristics were recorded. A scanning mobility particle sizer and GRIMM aerosol monitor measured aerosols 14.3 nm to 34 μm in diameter (i.e., particles smaller than those currently examined in the literature) during (1) nasal endoscopy (± debridement) and (2) no nasal endoscopy encounters. One‐way analysis of variance (ANOVA) and Student's t test were performed to compare aerosol concentrations and impact of HEPA filtration. Results Sixty‐two patients met inclusion criteria (25 nasal endoscopy without debridement; 18 nasal endoscopy with debridement; 19 no nasal endoscopy). There was no significant difference in age or gender across cohorts. Aerosol concentration in the nasal endoscopy cohort (± debridement) was not greater than the no nasal endoscopy cohort ( p = 0.36; confidence interval [95% CI], −1.76 to 0.17 μg/m 3 ; and p = 0.12; 95% CI, −0.11 to 2.14 μg/m 3 , respectively). Aerosol concentrations returned to baseline after 8.76 min without a HEPA filter versus 4.75 min with a HEPA filter ( p = 0.001; 95% CI, 1.73–6.3 min). Conclusion Using advanced instrumentation and a comparative study design, aerosol concentration was shown to be no greater during nasal endoscopy versus no endoscopy encounters. HEPA filter utilization reduced aerosol concentrations significantly faster than no HEPA filter.

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Abstract. As the changing climate expands the extent of arid and semi-arid lands, the number of, severity of, and health effects associated with dust events are likely to increase. However, regulatory measurements capable of capturing dust (PM10, particulate matter smaller than 10 µm in diameter) are sparse, sparser than measurements of PM2.5 (PM smaller than 2.5 µm in diameter). Although low-cost sensors could supplement regulatory monitors, as numerous studies have shown for PM2.5 concentrations, most of these sensors are not effective at measuring PM10 despite claims by sensor manufacturers. This study focuses on the Salt Lake Valley, adjacent to the Great Salt Lake, which recently reached historic lows exposing 1865 km2 of dry lake bed. It evaluated the field performance of the Plantower PMS5003, a common low-cost PM sensor, and the Alphasense OPC-N3, a promising candidate for low-cost measurement of PM10, against a federal equivalent method (FEM, beta attenuation) and research measurements (GRIMM aerosol spectrometer model 1.109) at three different locations. During a month-long field study that included five dust events in the Salt Lake Valley with PM10 concentrations reaching 311 µg m−3, the OPC-N3 exhibited strong correlation with FEM PM10 measurements (R2 = 0.865, RMSE = 12.4 µg m−3) and GRIMM (R2 = 0.937, RMSE = 17.7 µg m−3). The PMS exhibited poor to moderate correlations (R2 < 0.49, RMSE = 33–45 µg m−3) with reference or research monitors and severely underestimated the PM10 concentrations (slope < 0.099) for PM10. We also evaluated a PM-ratio-based correction method to improve the estimated PM10 concentration from PMSs. After applying this method, PMS PM10 concentrations correlated reasonably well with FEM measurements (R2 > 0.63) and GRIMM measurements (R2 > 0.76), and the RMSE decreased to 15–25 µg m−3. Our results suggest that it may be possible to obtain better resolved spatial estimates of PM10 concentration using a combination of PMSs (often publicly available in communities) and measurements of PM2.5 and PM10, such as those provided by FEMs, research-grade instrumentation, or the OPC-N3.