Portable HEPA air filtration effects on particulate matter, radioactivity, and chemical constituents in occupied homes.

Although in-home air cleaners are known to reduce particulate matter (PM) concentrations, their effects on PM chemical constituents and particle-bound radioactivity (PR) under real-world residential conditions remain poorly characterized. We evaluated the effects of a portable high-efficiency particulate air (HEPA) cleaner on particle mass, chemical composition, and particle-bound radioactivity in occupied homes. We collected 86 indoor samples from 19 homes in the Boston metropolitan area between June 2017 and March 2018. Measurements included size-resolved PM fractions (PM2.5, PM10-2.5, and > PM10), short-lived α activity (SLA) and long-lived α activity (LLA) associated with PM2.5, elemental composition, black carbon (BC), and a biomass-burning/cooking surrogate (DC). HEPA operation substantially reduced indoor particle concentrations, with mean decreases of 3.7, 1.0, and 0.5 µg/m3 for PM2.5, PM10-2.5, and >PM10, corresponding to removal efficiencies of approximately 60, 37, and 32%, respectively. LLA decreased by 0.68 mBq/m3, corresponding to a 63% removal efficiency (p < 0.001). SLA also decreased substantially, by 31.4 Bq/m3, or approximately 70%; however, this reduction was not statistically significant, likely because of the limited number of valid SLA measurements. Major and trace PM2.5 constituents -including sulfur, crustal elements, BC, and DC-also decreased significantly during HEPA operation. By jointly assessing PM mass, chemical composition, and particle-bound radioactivity across seasons (summer versus winter) and residential locations (family rooms versus basements), this study extends previous chamber-based and limited field investigations of air-cleaner performance. Overall, the findings indicate that portable HEPA cleaners can reduce indoor PM, chemically diverse PM2.5 constituents, and particle-bound radon decay products in occupied homes. HEPA filtration may therefore provide a practical supplemental strategy for reducing combined exposures to PM and particle-bound radioactivity. However, it does not remove gaseous radon and should not replace radon source-control or remediation measures.