Portable air cleaner use and biomarkers of inflammation: A systematic review and meta-analysis

Fine particulate matter air pollution (PM_2.5) is a major contributor to cardiovascular morbidity and mortality, potentially via increased inflammation. PM_2.5 exposure increases inflammatory biomarkers linked to cardiovascular disease, including CRP, IL-6 and TNFα. Portable air cleaners (PACs) reduce individual PM_2.5 exposure but evidence is limited regarding whether PACs also reduce inflammatory biomarkers. We performed a systematic review and meta-analysis of trials evaluating the use of PACs to reduce PM_2.5 exposure and inflammatory biomarker concentrations. We identified English-language articles of randomized sham-controlled trials evaluating high efficiency particulate air filters in non-smoking, residential settings measuring serum CRP, IL-6 and TNFα before and after active versus sham filtration, and performed meta-analysis on the extracted modeled percent change in biomarker concentration across studies. Of 487 articles identified, we analyzed 14 studies enrolling 778 participants that met inclusion criteria. These studies showed PACs reduced PM_2.5 by 61.5 % on average. Of the 14 included studies, 10 reported CRP concentrations in 570 participants; these showed active PAC use was associated with 7 % lower CRP (95 % CI: -14 % to 0.0 %, p = 0.05). Nine studies of IL-6, with 379 participants, showed active PAC use was associated with 13 % lower IL-6 (95 % CI: [-23 %, -3 %], p = 0.009). Six studies, with 269 participants, reported TNF-α and demonstrated no statistical evidence of difference between active and sham PAC use. Portable air cleaners that reduce PM_2.5 exposure can decrease concentrations of inflammatory biomarkers associated with cardiovascular disease. Additional studies are needed to evaluate clinical outcomes and other biomarkers.