Indoor PM2.5 Alpha-Radioactivity is Associated with Biomarkers of Oxidative Stress in COPD Patients

Abstract

Introduction: Radon decays into progeny that attach to indoor air pollution particles and form unattached clusters. After inhalation, we hypothesize that these serve as vectors for radioisotopes that emit radiation (including α-radioactivity) that promote oxidative damage in patients with COPD.Methods: We recruited 140 patients (97% men, mean (SD) age 72.8 (8.3)) with COPD at VA Boston 5/2013-3/2017 who ran a micro-environmental PM2.5 sampler in their home for 1 week up to 4 times a year (n=414 samples). Samples were analyzed for PM2.5 and black carbon (BC). In 2019, α-radioactivity was measured on each PM2.filter. Since 210Pb (t½=22 years), a Rn progeny, is a parent of 210Po (t½=138 days, α-radiation emitter), α-radioactivity reflects formation of 210Po from 210Pb. Based on the 210Pb decay constant and sampled air volume, α-radioactivity during sampling was estimated. Urinary concentrations of oxidative stress biomarkers, 8-hydroxy-2’-deoxyguanosine (8-OHdG) and malondialdehyde (MDA) were assessed. Mixed effects models with a random intercept for each subject were used to examine associations adjusting for age, race, season, urine collection time, BMI, creatinine, diabetes, heart disease, ambient temperature, humidity, and indoor BC and PM2.5.Results: Median (IQR) PM2.5 α-radioactivity=1.5 (0.64) mBq/m3 (equivalent to 0.056 (0.024) pCi/L); PM2.5=6.9 (5.7) µg/ m3; BC=0.58 (0.27) µg/m3. There was a positive association between natural log (α-radioactivity) and 8-OHdG [5.2% increase (95% CI: 0.9-9.7%) per IQR] and MDA [2.0% increase (95% CI: -2.6-6.8%) per IQR]. Results for 8-OHdG were similar adjusting for PM2.5 (5.4%; 95% CI: 1.1-10.0%) and BC (4.6%; 95% CI: 0.1-9.2%). Results for MDA were similar adjusting for PM2.5 (1.9%; 95% CI: -2.8-6.8%) and were reduced adjusting for BC [0.5%; 95% CI: -4.2-5.4%).Conclusions: Indoor PM2.5 α-radioactivity reflecting 210Pb was positively associated with increased DNA oxidation (8-OHdG) and lipid peroxidation (MDA) in participants with COPD.Funding: ES029637, ES019853, USEPA grant RD-835872