Specific Aims:
Specific Aim 1: To test the effect of HEPA filtration on markers of cardiovascular risk for adults who live near urban highways. 207 participants will be enrolled in a double blind, randomized crossover trial of 30-day periods with and without filtration separated by a 30-day wash out period. The intervention will be during colder months (Oct-Mar) when ambient UFP are elevated and windows tend to be closed, thereby allowing for maximization of the exposure contrast between HEPA and sham conditions. The investigators hypothesize that the HEPA filtration intervention will be associated with indications of improved health in the primary health outcomes: blood pressure (systolic, diastolic, and pulse pressure); and hsCRP (a measure of inflammation).
Specific Aim 2: To assess whether the intervention succeeded or failed in participant homes. To determine effectiveness of the filtration intervention, the investigators will 1) measure particle pollution levels inside and outside 20% of the homes, and 2) use quantitative surveys and open-ended questions to evaluate how participants interacted with the intervention.
Specific Aim 3: To assess biomarkers that can suggest biological pathways by which filtration affects cardiovascular risk. Study participants will be measured for IL-6 (inflammation), D-dimer (coagulation), central blood pressure, and arterial stiffness (endothelial dysfunction), which constitute key steps along the presumed biological pathways. The peripheral blood plasma of all participants will also undergo metabolome analysis to provide additional evidence of biological pathways. The investigators propose this to follow on an exciting recent study that used a similar approach 24, and preliminary metabolome analysis.
Exploratory Aims: To analyze particle composition. In a subset of homes (30 homes total, 10/year), the investigators will perform detailed physical and chemical analysis of PM1 (particles \<1,000 nm) to inform future work on composition-dependent health impacts and filtration effectiveness for UFP. Also in a subset of homes, assess personal exposures for 24 participants. The scientific premise is that HEPA filtration in homes without mechanical ventilation systems can reduce UFP (and overall PM) levels leading to positive changes in biomarkers. The study design and approach are rigorous, using a double blind, randomized cross over trial. The investigators will also measure objective biomarkers of risk of cardiovascular disease. The primary innovation is that this will be the first HEPA intervention trial near highways that is large enough to rule in or out efficacy of stand-alone HEPA filters from traffic pollution
Hypotheses:
1. For Aim 1, the investigators hypothesize that the HEPA filtration intervention will be associated with statistically significant improvements of peripheral blood pressure (BP) and C-reactive protein (hsCRP).
2. The investigators hypothesize that measures collected for Aim 3 will show that UFP is associated with antioxidant pathways, in vivo generation of reactive oxygen species, and processes critical to endothelial functions, as well as indicators of early vascular aging.
