Effects of Corsi-Rosenthal boxes on indoor air contaminants: non-targeted analysis using high resolution mass spectrometry.

BACKGROUND: In response to COVID-19, attention was drawn to indoor air quality and interventions to mitigate airborne COVID-19 transmission. Of developed interventions, Corsi-Rosenthal (CR) boxes, a do-it-yourself indoor air filter, may have potential co-benefits of reducing indoor air contaminant levels. OBJECTIVE: We employed non-targeted and suspect screening analysis (NTA and SSA) to detect and identify volatile and semi-volatile organic contaminants (VOCs and SVOCs) that decreased in indoor air following installation of CR boxes. METHODS: Using a natural experiment, we sampled indoor air before and during installation of CR boxes in 17 rooms inside an occupied office building. We measured VOCs and SVOCs using gas chromatography (GC) high resolution mass spectrometry (HRMS) with electron ionization (EI) and liquid chromatography (LC) HRMS in negative and positive electrospray ionization (ESI). We examined area count changes during vs. before operation of the CR boxes using linear mixed models. RESULTS: Transformed (log2) area counts of 71 features significantly decreased by 50-100% after CR boxes were installed (False Discovery Rate (FDR) p-value < 0.2). Of the significantly decreased features, four chemicals were identified with Level 1 confidence, 45 were putatively identified with Level 2-4 confidence, and 22 could not be identified (Level 5). Identified and putatively identified features (Level ≥4) that declined included disinfectants (n = 1), fragrance and/or food chemicals (n = 9), nitrogen-containing heterocyclic compounds (n = 4), organophosphate esters (n = 1), polycyclic aromatic hydrocarbons (n = 8), polychlorinated biphenyls (n = 1), pesticides/herbicides/insecticides (n = 18), per- and polyfluorinated alkyl substances (n = 2), phthalates (n = 3), and plasticizers (n = 2). IMPACT STATEMENT: We used SSA and NTA to demonstrate that do-it-yourself Corsi-Rosenthal boxes are an effective means for improving indoor air quality by reducing a wide range of volatile and semi-volatile organic contaminants.

Changes in Ultrafine Particle Concentrations near a Major Airport Following Reduced Transportation Activity during the COVID-19 Pandemic.

Mobility reductions following the COVID-19 pandemic in the United States were higher, and sustained longer, for aviation than ground transportation activity. We evaluate changes in ultrafine particle (UFP, Dp < 100 nm, a marker of fuel-combustion emissions) concentrations at a site near Logan Airport (Boston, Massachusetts) in relation to mobility reductions. Several years of particle number concentration (PNC) data prepandemic [1/2017-9/2018] and during the state-of-emergency (SOE) phase of the pandemic [4/2020-6/2021] were analyzed to assess the emissions reduction impact on PNC, controlling for season and wind direction. Mean PNC was 48% lower during the first three months of the SOE than prepandemic, consistent with 74% lower flight activity and 39% (local)-51% (highway) lower traffic volume. Traffic volume and mean PNC for all wind directions returned to prepandemic levels by 6/2021; however, when the site was downwind from Logan Airport, PNC remained lower than prepandemic levels (by 23%), consistent with lower-than-normal flight activity (44% below prepandemic levels). Our study shows the effect of pandemic-related mobility changes on PNC in a near-airport community, and it distinguishes aviation-related and ground transportation source contributions.