Air Pollution
Conditions
Keywords
Traffic-related air pollution, Air filtration, Blood pressure, Controlled exposure
Brief summary
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
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.
Interventions
OTHERAir filtration and building envelop modifications
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.
Sponsors
National Institute of Environmental Health Sciences (NIEHS)
UConn Health
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
OTHER
Masking
SINGLE (Subject)
Masking description
Participants were not told the high, medium and low exposure context, however, some aspects of the sessions might have been apparent to them since filters were running during high, but not low exposure sessions.
Intervention model description
Randomized cross over trial
Eligibility
Sex/Gender
ALL
Age
40 Years to 75 Years
Healthy volunteers
Yes
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.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Systolic Blood Pressure (SBP) | 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. | Systolic blood pressure measured with ambulatory blood pressure monitors in mmHg. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Diastolic Blood Pressure (DBP) | 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. | The unit of measurement, mmHg for the diastolic blood pressure. |
Countries
United States
Participant flow
Pre-assignment details
Using a 3-period crossover design, 77 participants were randomized to attend. Three 2-hour-long exposure sessions separated by 1-week washout periods. None was excluded.
Participants by arm
| Arm | Count |
|---|---|
| High Exposure (First Session), Low, Medium Exposure Ambient air was allowed freely into the room. Participants first received a 2-hour-long High exposure session. After a washout period of 1 week, they then received a 2-hour-long Low exposure session. After a washout period of 1 week, they then received a 2-hour-long Medium exposure session. All sessions occurred on the same day of the week. | 30 |
| Medium Exposure(First Session), High, Low Exposure Limited air filtration was used to partially reduce levels of pollution in the room relative to outside.
Air filtration and building envelop modifications: 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.
Participants first received a 2-hour-long Medium exposure session. After a washout period of 1 week, they then received a 2-hour-long High exposure session. After a washout period of 1 week, they then received a 2-hour-long Low exposure session. All sessions occurred on the same day of the week. | 28 |
| Low Exposure (First Session), Medium, High Exposure Doors and windows were closed and sealed and full filtration was used to maximally reduce pollution in the room.
Air filtration and building envelop modifications: 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.
Participants first received a 2-hour-long Low exposure session. After a washout period of 1 week, they then received a 2-hour-long Medium exposure session. After a washout period of 1 week, they then received a 2-hour-long High exposure session. All sessions occurred on the same day of the week. | 19 |
| Total | 77 |
Baseline characteristics
| Characteristic | High Exposure (First Session), Low, Medium Exposure | Total | Low Exposure (First Session), Medium, High Exposure | Medium Exposure(First Session), High, Low Exposure |
|---|---|---|---|---|
| Age, Continuous | 59.7 years STANDARD_DEVIATION 10.5 | 59.7 years STANDARD_DEVIATION 10.5 | 59.7 years STANDARD_DEVIATION 10.5 | 63.3 years STANDARD_DEVIATION 9.6 |
| Ethnicity (NIH/OMB) Hispanic or Latino | 1 Participants | 3 Participants | 0 Participants | 2 Participants |
| Ethnicity (NIH/OMB) Not Hispanic or Latino | 29 Participants | 74 Participants | 19 Participants | 26 Participants |
| Ethnicity (NIH/OMB) Unknown or Not Reported | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) American Indian or Alaska Native | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) Asian | 23 Participants | 59 Participants | 15 Participants | 21 Participants |
| Race (NIH/OMB) Black or African American | 1 Participants | 2 Participants | 1 Participants | 0 Participants |
| Race (NIH/OMB) More than one race | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) Native Hawaiian or Other Pacific Islander | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) Unknown or Not Reported | 0 Participants | 1 Participants | 0 Participants | 1 Participants |
| Race (NIH/OMB) White | 6 Participants | 15 Participants | 3 Participants | 6 Participants |
| Region of Enrollment United States | 30 Participants | 77 Participants | 19 Participants | 28 Participants |
| Sex: Female, Male Female | 27 Participants | 61 Participants | 12 Participants | 22 Participants |
| Sex: Female, Male Male | 3 Participants | 16 Participants | 7 Participants | 6 Participants |
| Systolic Blood Pressure | 115.9 mmHg STANDARD_DEVIATION 14.4 | 118.0 mmHg STANDARD_DEVIATION 17.9 | 120.3 mmHg STANDARD_DEVIATION 23.4 | 118.6 mmHg STANDARD_DEVIATION 17.6 |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk | EG002 affected / at risk |
|---|---|---|---|
| deaths Total, all-cause mortality | 0 / 30 | 0 / 28 | 0 / 19 |
| other Total, other adverse events | 0 / 30 | 0 / 28 | 0 / 19 |
| serious Total, serious adverse events | 0 / 30 | 0 / 28 | 0 / 19 |
Outcome results
Primary
Systolic Blood Pressure (SBP)
Systolic blood pressure measured with ambulatory blood pressure monitors in mmHg.
Time frame: 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.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| High Exposure | Systolic Blood Pressure (SBP) | 122.3 mmHg | Standard Error 0.8 |
| Medium Exposure | Systolic Blood Pressure (SBP) | 120.83 mmHg | Standard Error 0.7 |
| Low Exposure | Systolic Blood Pressure (SBP) | 119.9 mmHg | Standard Error 0.8 |
Secondary
Diastolic Blood Pressure (DBP)
The unit of measurement, mmHg for the diastolic blood pressure.
Time frame: 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.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| High Exposure | Diastolic Blood Pressure (DBP) | 69.9 mmHg | Standard Error 0.5 |
| Medium Exposure | Diastolic Blood Pressure (DBP) | 70.4 mmHg | Standard Error 0.5 |
| Low Exposure | Diastolic Blood Pressure (DBP) | 71.0 mmHg | Standard Error 0.5 |