Household dust as a reservoir for environmentally persistent free radicals: a longitudinal study

Epidemiological links between air pollution and adverse health outcomes are strong, but the mechanism(s) remain obscure. A newly recognised combustion by-product, environmentally persistent free radicals (EPFRs), may be the missing link. The objective of this study is to explore the presence of EPFRs in house dust and ascertain if EPFR concentration is stable across time and season. The ELLF cohort is a longitudinal birth cohort (n = 82) with house dust collected at multiple time points. EPFR characteristics were assessed with electron paramagnetic resonance, and oxygen-weighted concentration was estimated by an algorithm. Seasonal differences were assessed with Kruskal-Wallis rank sum and Fisher's exact tests. A mixed-effects linear regression was employed for longitudinal analysis. 83 participants returned 238 dust samples, with EPFRs measured in >95% of samples. EPFR concentration and oxygen-weighted concentration were stable across visits (p = 0.05). There was a seasonal trend, with concentration (p = <0.01), oxygen weighted concentration (p = <0.01), and g factor (p = 0.05) all significantly lower in summer months. EPFRs are consistently present in house dust and are stable across time in households. These findings suggest that exposure to EPFRs occurs in the home and may be a significant place for exposure to highly biologically reactive EPFRs.