Breathe Easier, Live Healthier: A Simple Solution for Highway Residents' Heart Health

Unveiling the Health Toll of Environmental Pollutants

Numerous investigations have consistently documented elevated levels of fine particulate matter (PM) in residential zones adjacent to busy thoroughfares, primarily stemming from vehicle exhaust, as well as tire and brake debris. Ultra-fine particles (UFPs), measuring less than 0.1 micrometers, and PM2.5, particles with an aerodynamic diameter under 2.5 micrometers, readily infiltrate homes lacking adequate ventilation and high-efficiency filtration systems. Consequently, individuals residing within 200 meters of high-volume highways face substantial exposure to excessive atmospheric contaminants.

Prior research has firmly established a correlation between exposure to particulate matter and an increased risk of cardiovascular ailments. These studies have additionally indicated that exposure to traffic-related PM elevates the likelihood of hypertension and elevated blood pressure. Furthermore, evidence shows that individuals with heightened systolic blood pressure (SBP) and diastolic blood pressure (DBP) are at a greater risk of heart attacks, strokes, and overall vascular mortality. For instance, a mere 2 mm Hg increase in SBP has been associated with a 7% rise in the risk of mortality from ischemic heart disease.

Previous scholarly work has demonstrated that minimizing PM exposure can lead to a reduction in blood pressure, thereby ultimately decreasing fatalities attributed to cardiovascular diseases or strokes. These beneficial outcomes were also observed among individuals with elevated low-density lipoprotein cholesterol levels and those who smoke.

Investigating the Impact of Home Air Filtration

The current randomized crossover study, conducted over four years from 2020 to 2024, involved recruiting participants through door-to-door outreach. Individuals were eligible if they lived within 200 meters of at least one high-traffic highway (I-93 and Rt-38) in eastern Massachusetts, USA. Recruitment primarily occurred during cooler months, a period when traffic-generated particulate matter tends to be more concentrated. All participants were over 30 years of age and proficient in either English or Spanish.

Exclusion criteria for the study included individuals who smoked or vaped, those receiving antihypertensive or anti-inflammatory medications, people with a recent history of major cardiovascular events or cancer treatments, and those with significant indoor combustion sources (excluding cooking). Additionally, individuals with occupational exposure to traffic pollution or an active COVID-19 infection were not included.

Participating households were randomly assigned to use HEPA air purifiers for one month, or identical "sham" purifiers (with filters removed) for the same duration. Following this initial month, all devices were withdrawn for a one-month "washout" period, providing no air filtration. Subsequently, households switched to the alternative type of purifier for an additional month. Austin Air's HealthMate air purifiers were utilized, featuring medical-grade HEPA filters covering 5.5 square meters, capable of removing particles smaller than 0.3 micrometers and 0.1 micrometers with efficiencies exceeding 99% and 95%, respectively. The sham filtration units were identical but lacked the active filter.

All participants completed a questionnaire at the study's outset and during three subsequent home visits. Information gathered included smoking habits, general health status, daily activities, and perceived social stress. Blood pressure readings were taken four times: at the study's commencement and at the conclusion of each filtration period.

Key Outcomes and Health Implications

The randomized crossover trial encompassed 154 participants from 108 residences, with 153 participants experiencing 30 days of HEPA filtration and 152 undergoing 30 days of sham filtration. The study population was predominantly female (59.7%), non-Hispanic White (68.2%), and Hispanic (18.7%), with a significant majority (82.9%) employed part-time or full-time. Most participants exhibited a higher socioeconomic status, holding college degrees and earning household incomes exceeding USD 85,000 annually. The average age of participants was 41.1 years, with a mean baseline brachial systolic blood pressure (SBP) and diastolic blood pressure (DBP) of 118.8/76.5 mmHg.

The HEPA filtration system demonstrated a significant reduction in PM2.5 concentration when compared to both outdoor air and indoor conditions with sham filtration. The average 24-hour PM2.5 concentrations were recorded as 3.9 μg/m³ outdoors, 5.2 μg/m³ indoors with sham filtration, and a notably lower 2.5 μg/m³ with HEPA filtration. Similarly, mean particle number count (PNC) concentrations over a 24-hour period were estimated at 10,052, 6,925, and 4,706 particles/cm³ for outdoor, indoor sham, and HEPA filtration, respectively. It was observed that both PM2.5 and PNC concentrations decreased during the overnight hours.

The majority of blood pressure measurements were taken between 6:00 a.m. and 8:00 a.m., accounting for 77.5% of all readings, ensuring consistency in measurement timing. The study revealed a statistically non-significant overall difference of 0.5 mm Hg in SBP reduction between HEPA and sham filtration for the entire cohort. However, participants who presented with elevated brachial SBP at the start of the intervention period experienced a notable SBP reduction of 2.8 mm Hg when using HEPA filtration. Conversely, these same participants showed a slight mean increase of 0.2 mm Hg in SBP during the sham filtration phase.

Sensitivity analysis further underscored the relationship between the baseline SBP threshold and the effectiveness of HEPA intervention. A greater percentage of SBP reduction was observed in individuals who commenced the intervention with elevated SBP and utilized HEPA filtration.

Future Directions and Public Health Recommendations

The current study underscores the positive impact of air purifiers on reducing blood pressure, particularly for individuals with elevated systolic blood pressure residing in areas close to major highways. No substantial benefit was observed for participants whose baseline systolic blood pressure was within the normal range. Further investigations are needed to conduct a more detailed subgroup analysis to fully ascertain additional advantages of employing air purifiers.

Given the absence of reported adverse effects, the researchers strongly advocate for the use of indoor air purifiers by vulnerable populations. This includes individuals with pre-existing cardiovascular risk factors, such as high blood pressure, and those whose homes are situated near high-traffic thoroughfares, as a proactive measure to safeguard their cardiovascular health.