Meta-Analysis of Residential Portable Air Cleaner Use and Circulating Inflammatory Biomarkers

Introduction: Fine particulate matter air pollution (PM 2.5 ) exposure is associated with elevated circulating inflammatory biomarkers implicated in cardiovascular disease (CVD). Portable Air Cleaners (PAC)s reduce PM 2.5 exposure and may lower concentrations of inflammatory biomarkers. Methods: We performed a systematic review and meta-analysis of randomized crossover trials of in-home high efficiency particulate air (HEPA) PACs vs. sham control on changes in CRP, IL-6, and/or TNFα among adults with no smoking exposure using Medline, Embase, and Cochrane Central Register of Controlled Trials with the Ovid Platform, Inspec, Compendix, and Web of Science Core Collection. Two investigators (S.W, D.W.) independently screened and reviewed the studies. We used RevMan 5.3 to perform the meta-analysis. Results: Search results included 459 articles screened, 26 selected for full review, and 14 that met inclusion criteria, representing N=724 participants included in the meta-analysis. Ten studies reported CRP, 9 reported IL-6, and 5 reported TNFα. Based on WHO guidelines, 5 studies were in regions of extreme PM 2.5 exposure (>35 μg/m 3 ), 3 were high (10-35 μg/m 3 ), 3 were low (<10 μg/m 3 ), and 2 lacked baseline PM 2.5 . Median (± S.D.) duration of HEPA/sham use was 9 ± 6.6 days. Reductions in PM 2.5 ranged from 2.6 to 54.9 μg/m 3 (35-82%) and varied by baseline PM 2.5 , although reporting of baseline PM 2.5 was incomplete across trials. Compared to sham PAC use, active PACs were associated with a 7% lower CRP (95% CI -13%, 0%) and 12% lower IL-6 (-22%, -2%), P<0.05 for both (Figure). Subgroup analyses demonstrated consistency of effect of PACs across levels of baseline PM 2.5 . Conclusions: Our data demonstrate that PAC use is associated with significant reductions in circulating CRP and IL-6, with a magnitude of effect similar to clinical trials of statins and IL-1β inhibition. Given the role of inflammation in CVD, PACs may be useful to reduce systemic inflammation and cardiovascular risk.