Reducing Traffic Pollution Exposure Improves Blood Pressure

Living close to major roadways is associated with elevated blood pressure (BP) amongst other adverse health effects. There is growing evidence that ultrafine particles (UFP, <100 nm in diameter), which are elevated near major roads and highways, contribute to such risks. We assessed the efficacy of high efficiency particulate arrestance (HEPA) filtration and building envelope adjustment at reducing exposure to and health effects of air pollution next to major highways.

We used a randomized three-period crossover trial design to assign 77 participants (aged 40-75 and without diagnosis of hypertension) to three two-hour exposure sessions. Sessions were conducted in one of two rooms immediately adjacent to highways. High, medium and low exposures were attained by varying the degree of air exchange and amount of HEPA filtration in the room. During high exposure sessions, the room was ventilated with outdoor air and no filtration was used. During low exposure sessions, leakage of outdoor air into the room was minimized and HEPA filtration was maximized. During medium exposure sessions, a moderate amount of HEPA filtration was used (less than half of that used in low sessions). Indoor particle number and black carbon (BC) concentrations (i.e., markers of traffic-related air pollution) were monitored continuously.

During each session participants sat quietly and wore noise-cancelling headphones, while their BP was monitored every ten minutes using an ambulatory BP monitor. We monitored pulse and oxygen saturation continuously.

Inclusion criteria

• The inclusion criterion was age 40-75 years.
• There was a preference for people who were otherwise healthy, but overweight or obese.

Exclusion criteria

• A history of a major cardiovascular outcome (including myocardial ischemia (MI), stroke, angina)
• Other serious health problems (current asthma or COPD)
• Taking anti-hypertensive medications
• Smoking or living with a smoker
• Cognitive impairment
• Working at a job with high combustion exposure (taxi/truck driver, restaurant cook)
• High combustion exposure in the preceding 24 hours (driving on the highway, cooking in a restaurant, driving a truck)
• Not speaking English or Chinese.