Indoor Air Quality

Research summary

• Improving indoor air quality with portable HEPA filtration has a real but genuinely inconsistent randomized-trial evidence base, with cardiovascular benefits appearing in some trials and not others.
• In a double-blind crossover trial of 35 healthy college students in Shanghai, just 48 hours of active air purification cut indoor PM2.5 by 57% and was followed by significant drops in several inflammatory and clotting biomarkers, plus reductions in systolic blood pressure (2.7%) and diastolic blood pressure (4.8%).
• A similar crossover trial in 24 older adults in an aged-care center in China found two days of filtration significantly lowered inflammatory and coagulation biomarkers, though not oxidative-stress markers or lung function.
• However, the Beijing Indoor Air Purifier Study, using two weeks of filtration in 35 seniors including those with COPD, found air quality improved substantially but found no significant change in blood pressure, heart rate variability, or lung function -- only a reduction in one inflammatory marker (interleukin-8).
• A U.S. pilot trial in 20 cardiac rehabilitation patients found in-home air cleaners lowered personal PM2.5 exposure by 44%, and a more recent trial in older adults at a residential facility confirmed air cleaners reliably reduce bedroom PM2.5 exposure but found no significant average change in home blood pressure over 4 weeks, though it flagged that people with higher baseline blood pressure or body mass index may benefit more.
• Overall, the evidence consistently shows air filtration works as advertised at reducing indoor particulate exposure, but whether that translates into a measurable cardiovascular health benefit appears to depend on exposure duration, population, and which biomarker is measured -- this is best treated as a plausible but unproven intervention, not yet resting on any meta-analysis or mortality data.