Reducing Traffic Pollution Exposure Improves Blood Pressure

Study Overview
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Brief Summary
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This randomized trial assessed the effect of modifying building envelop and level of air filtration on blood pressure over two hour exposure sessions.

Detailed Description
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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.

Official Title
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Near Highway Pollution: From Research to Action

Conditions
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Air Pollution

Intervention / Treatment
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* Other: Air filtration and building envelop modifications


Participation Criteria
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Eligibility Criteria
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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.

Ages Eligible for Study
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Minimum Age: 40 Years
Maximum Age: 75 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Randomized cross over trial
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: High exposure<br>Ambient air was allowed freely into the room. | Other: Air filtration and building envelop modifications<br>* Air filters and closing and sealing of windows and doors was used to reduce infiltration of air pollution from outdoors in rooms next to major highways at rush hour.<br>|
| Experimental: Medium exposure<br>Limited air filtration was used to partially reduce levels of pollution in the room relative to outside. | Other: Air filtration and building envelop modifications<br>* Air filters and closing and sealing of windows and doors was used to reduce infiltration of air pollution from outdoors in rooms next to major highways at rush hour.<br>|
| Experimental: Low exposure<br>Doors and windows were closed and sealed and full filtration was used to maximally reduce pollution in the room. | Other: Air filtration and building envelop modifications<br>* Air filters and closing and sealing of windows and doors was used to reduce infiltration of air pollution from outdoors in rooms next to major highways at rush hour.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Systolic Blood Pressure (SBP) | Systolic blood pressure measured with ambulatory blood pressure monitors in mmHg. | Over 2 hour exposure period, we measured SBP after 20 minutes with the objective to assess change in SBP in a time series of measurements over that time period. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Diastolic Blood Pressure (DBP) | The unit of measurement, mmHg for the diastolic blood pressure. | Over a 2 hour exposure period with the objective to assess change in DBP measured after 10 minutes in a time series of measurements over that time period. | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Traffic-related air pollution, Air filtration, Blood pressure, Controlled exposure