A randomized crossover trial of portable air cleaners to reduce PM and SARS-CoV-2 exposures at home

Abstract: Americans newly infected with SARS-CoV-2 (SC2) are directed to isolate at home with care provided byhousehold members. Isolation from others may be difficult to maintain for 2 weeks, especially in economicallychallenged households without enough space to create a private sick room and bathroom. The CDCrecommends that at-home patients and their caregivers use makeshift facemasks for care-giver protection.They do not address the possibility of virus spread via smaller particles that are not captured by improvisedfacemasks. Accumulating evidence supports the significance of patient-generated aerosols, with and withoutambient PM, in the transmission of SC2 infection, but haven't been subject to controlled study. U.S. PM2.5concentrations are linked to a 15% increase in COVID-19 deaths per ?g/m3 of PM2.5, suggesting an interactionbetween the two stressors. Thus, we plan to quantify SC2 in different PM fractions in home isolation rooms ofnewly diagnosed individuals Moreover, a common recommendation to reduce indoor aerosol exposures isfiltration, and based on our experience we plan a crossover trial of air cleaners in home isolation rooms. Wehypothesize that portable indoor particle filters will reduce both airborne PM and associated viral particleconcentrations in the air around patients. We aim to test this hypothesis by enrolling 20 individuals from ouremployee health clinics with newly diagnosed SC2 infections in a cross-over randomized trial of home aircleaners. These will be continuously operated alternately for two consecutive 24-hour cycles, one cycle with aHEPA filter, and the other with a sham filter. Size selective impactors in the isolation room will elucidateparticle sizes most associated with virus. Samplers will allow capture of PM2.5, PM coarse (10-2.5), and >PM10fractions. In both the isolation room and the main living area we will collect total inhalable particles (d<100 µm)at 10 L/min. These samples will be used in initial analyses to check if there is sufficient viral RNA in individualimpactor stages for reliable detection and quantification. Concentrations of PM and virus will be comparedbetween filtered and sham conditions .The greatest impact of our studies will be finding of a significant viralconcentration in the aerosol range (specifically, particles < 10 µm) documenting the potential for aerosolexposure to SC2. Finding substantial viral content in aerosol size fractions will have additional public healthimplications, as preventing person-to-person aerosol transmission is more challenging than preventingtransmission via larger droplets, the focus of almost all current prevention recommendations.