Particle radioactivity from radon decay products and reduced pulmonary function among chronic obstructive pulmonary disease patients

Abstract

BackgroundRadon (222Rn) decay products can attach to particles in the air, be inhaled, and potentially cause airway damage. Research questionIs short-term exposure to particle radioactivity (PR) attributable to radon decay products emitted from particulate matter ≤2.5 μm in diameter (PM2.5) associated with pulmonary function in chronic obstructive pulmonary disease (COPD) patients? Study design and methodsIn this cohort study, 142 elderly, predominantly male patients with COPD from Eastern Massachusetts each had up to 4 one-week long seasonal assessments of indoor (home) and ambient (central site) PR and PM2.5 over the course of a year (467 assessments). Ambient and indoor PR were measured as α-activity on archived PM2.5 filter samples. Ratios of indoor/ambient PR were calculated, with higher ratios representing PR from an indoor source of radon decay. We also considered a measure of outside air infiltration that could dilute the concentrations of indoor radon decay products, the indoor/ambient ratio of sulfur concentrations in PM2.5 filter samples. Spirometry pre- and post-bronchodilator (BD) forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were conducted following sampling. Generalized additive mixed models were adjusted for meteorologic variables, seasonality, and individual-level determinants of pulmonary function. We additionally adjusted for indoor PM2.5 and black carbon (BC). ResultsPR exposure metrics indicating radon decay product exposure from an indoor source were associated with a reduction in FEV1 and FVC. Patients in homes with high indoor PR (≥median) and low air infiltration (<median) compared to others had a −26.9 (95% CI: −61.4, 7.7) mL and −75.4 (95% CI: −128.6, −22.2) mL reduction in post-BD FEV1 and FVC, respectively. These associations remained similar after PM2.5 and BC adjustment. InterpretationOur findings raise concern about the harmful effects of PR exposures attributable to residential radon on pulmonary function in patients with COPD.