Cardiovascular Effects of Exposure to Wood Smoke in Healthy Human Adults (MASKOFF)

  • End date
    Dec 3, 2022
  • participants needed
  • sponsor
    University of North Carolina, Chapel Hill
Updated on 28 February 2022
Accepts healthy volunteers


Purpose: The study is designed to investigate cardiovascular effects of young healthy human subjects exposed to wood smoke.

Participants: Approximately 80 young (18-35 years old) healthy subjects to complete.

Procedure (methods): After consenting to participate in the study, subjects will undergo exposures over consecutive days, once to filtered air alone and once to air containing 500 g/m^3 of wood smoke. Each exposure will be 2 hours long with alternating 15 min of mild exercise (cycle ergometer) and rest . The exercise level will be adjusted to achieve 12 L/min/m^2 minute ventilation. Induced sputum samples will be collected 4 hours post exposure.


Wood smoke pollution is a common problem across the world, including in the US. This wood smoke comes from people using wood to heat and cook, as well as from wildfires. The purpose of this research study is to investigate the cardiovascular effects of exposure to wood smoke in young healthy human subjects. Results from this study will also increase our understanding of how wood smoke exposure adversely affects the functioning of the human cardiovascular and respiratory systems. This understanding may be especially important for patients with cardiopulmonary diseases.

Approximately 80 people will participate in this study.

You should expect to be in this study for about a month, but your participation could possibly last for 6 months. There are 4 sessions, including a consenting session (today) which will last for about 4 hours. The two exposure-day sessions will last approximately 8-9 hours each. There will also be an approximately 3-hour follow-up visit the day after your last exposure.

Before you agree to participate in this study, you must read the consent forms in their entirety. The research and medical staff will then answer all your questions and explain all the risks involved in this study to your satisfaction.

You should have already undergone a general physical examination to ensure that you are a suitable candidate for this study. If you are a female, you will be asked about your menstrual history. For all other female participants, a pregnancy test will be performed today, and this will be repeated on the exposure day if more than 7 days since last pregnancy test.

Consenting Day We will go over the study in detail so that you will know what we will expect from you as a participant and what you should expect from us as investigators. If you agree to participate in the study, you will sign all study consent forms and receive one set of signed copies.

You will have a breathing test (spirometry). You will breathe through a filter into a plastic device. Your lung function test results should meet certain criteria (Both Forced Vital Capacity (FVC) and Forced Expiatory Volume at the 1st second (FEV1) are equal to and greater than 80% of the reference value) to allow you to participate in the study.

You will be asked to wear a face mask, also called face filtering pieces (FFP), and the efficiency of the FFP will be measured. You will complete a short survey on your previous experience of using such masks. Then you will put on a provided mask under four scenarios that simulate real world conditions. During the test, you will be asked to perform a few simple tasks such as bending over, talking, etc. A particle counter will be used to monitor the particle number behind the facemask and in the ambient air. Room air particles will consist of fine droplets made up of water and table salt (sodium chloride) that will be emitted by a particle generator. The efficiency of the facemask performance under each condition will be recorded and compared.

You will undergo a procedure for nasal epithelial lining fluid (NELF) sampling (nasal mucosa) and a procedure for induced sputum. If you are a non-producer or the quality of the induced sputum sample that you produce does not meet the study criteria (we will know the sputum quality in the next two days), we will exclude you from the study. If that happens, you will be reimbursed for the time and procedures for the consenting session. If you qualify, you will be given instructions to prepare for the exposure sessions. Then you will be scheduled for the exposure sessions.

Exposure days We will call you a few days before the exposure session to remind you of your scheduled visit. You should avoid smoke, fumes, alcohol, and strenuous exercise 24 hours prior to all visits, and abstain from pan fried or grilled meat after midnight of the exposure day.

You will be asked to eat a light breakfast and arrive at the EPA medical station by 7:30 am. Please understand that it is very important that you arrive by this time in order for the study team to process all of the samples and data. Please note that we may have to cancel your participation if you arrive late.

Prior to exposure, you will:

  • Have your vital signs checked (heart rate, respiratory rate, blood pressure, oxygen saturation level, and fill out a symptom questionnaire electronically).
  • Have your heart rhythm recorded by a Holter monitor. You will have (10) electrocardiogram (ECG) leads attached to your chest. It may be necessary to clean and shave the areas of your chest where these leads will be placed. Excessive deodorant, skin lotions, and body sprays may interfere with the function of some of these leads. Therefore, we ask you to not apply these to your chest area on the day you report to the HSF. The leads will be connected to 2 monitors (small recording devices about the size and weight of a cell phone) to obtain readings of your heart rate and rhythm. It is preferable that the electrodes will stay in place for approximately 2 days as you will have this measured several times during the study, however, you will be given the option to remove the electrodes by the end of each exposure day. You will be asked to recline quietly for 30 minutes while collecting your heart rhythm. It is important that you do not fall asleep during this 30-minute period. These measurements will allow us to determine whether wood smoke exposure causes small changes in the ability of your nervous system to regulate how your heart beats.
  • Have the diameter of an artery in your upper arm measured by an ultrasound machine (BAU). The ultrasound operator will scan your arm with a probe and then place a tourniquet on your arm, much like a cuff used to measure blood pressure. Measurement of the size of the artery will be made two times. First, you will be asked to rest quietly for 15 minutes, and then the first 90 second scan will be performed. Then the blood pressure cuff on your arm will be inflated for 5 minutes in order to temporarily stop the flow of blood. You may feel sensations similar to that when your foot "goes to sleep", such as "pins and needles" and tingling. After the pressure cuff is released, a second scan will be taken of the artery.
  • Have your retinas imaged using an ophthalmic camera before and after each exposure, and on the follow-up visit. You will be asked to place your chin on a rest in front of the camera. We will take pictures of the inside of both of your eyes. Glasses or contacts have to be removed for this test. Please bring your own contact lens container and solutions.
  • Approximately 60 ml blood drawn (about 4 tablespoons) before and after each exposure, and on the follow-up visit. We will test this blood to see if wood smoke affects the ability of your blood cells to function. A small portion of the blood sample will be used to measure the relative content of various fatty acids present in your blood. With your permission, we also store some of the blood that we obtain during the study for yet-to-be-determined tests in the future.
  • Have a breathing test (spirometry).
  • Enter the exposure chamber and be exposed to filtered air or wood smoke.

During the exposure, you will:

Undergo exposure for 2 hours to either clean filtered air or wood smoke in the chamber. You will receive clean filtered air on one day and wood smoke on the other day. You will not be given the information of the sequence of the exposure. The concentration of wood smoke that you will be exposed to in this study (approximately 500 g/m3) are below those reported for those using biomass burning for heating and food preparation, those firefighters are exposed to, and those living in the area of a forest fire or agricultural burning are exposed to. Chamber conditions will be at a comfortable temperature and relative humidity. You will do mild exercise on a stationary bicycle in the chamber every other 15 minutes alternating with resting period for a total of 1 hour of exercise per chamber exposure. The target ventilation rate will be maintained at 12 L/min/ m2 and monitored by using pneumotach and BioPac methods. A study coordinator or other trained person will be seated outside the chamber observing you at all times. During the exposure, your heart will be monitored and the amount of oxygen present in your blood will be monitored by placing a device (pulse oximeter) on your finger. If it appears you are experiencing significant discomfort, breathing or heart problems, the exposure will be terminated immediately. In addition, you may elect to terminate the exposure at any time for any reason. If you do so, you will be paid in full for that day's session but will be ineligible for further participation in the study and any payments you would have received for future participation.

Immediately following the exposure, you will repeat the pre-exposure procedures and have a low fat lunch brought by you.

  • Once you complete the above procedures, you will have about 1-2 hour waiting time before the next procedure. You can bring your personal laptop or books to use during that time. You will not be able to eat any food during this break time. We also encourage you to take a shower to get rid of the wood smoke odor at a private shower facility here at the HSF. Towel, soap and shampoo will be provided.
  • Have samples of your nasal epithelial lining fluid (NELF) collected. Study staff will give you small filter paper strips and you will insert one into each nostril. You will wear nose clips for two minutes to allow for lining fluid absorption to the paper. The paper will then be removed and collected specimen placed into sample tubes.
  • Have samples of your airway secretions collected using the induced sputum procedure. You will be asked to breathe in different saline solutions (up to 5%) to help you expectorate. We will coach you on the procedure. First, you will gargle and clear your throat, and the cough up samples from deep in your chest and spit them into a cup. Your lung function will be monitored during the procedure. Food must be avoided for 2 hours prior to this test.
  • TracMyAir: The TracMyAir App on an EPA provided smartphone will be used by study personnel each day when you visit the EPA health study facility. The App will not be installed on your phone. The study staff will ask you questions on your home building characteristics, home operating conditions, time-spent in different outdoor and indoor environments, and time-spent at different physical activity levels. The study personnel will input data for you into the App. At the end of each exposure day, the EPA smartphone with TracMyAir app will be issued to you and will continuously measure your location like a GPS travel recorder. You will return the phone on the following day. TracMyAir does not save the calculated exposures on the smartphone and the data is de-identified.
  • GPS travel recorder: will be issued to you on the day of your exposure session and returned to facility on the next day. This device continuously monitors GPS coordinates and records internally. You will carry the device at all times (24 hours) to record your location so that we can assess your exposure to air pollution during the day. The location data are not displayed and are only available to download with proper proprietary software after your session. Data will be downloaded and stored onto a secure database.
  • Be assessed and discharged by the study personnel.

Follow up visit (about 3 hours) You will return to the HSF the next morning (approximately 18 hours after your 2nd exposure) and you will repeat the pre-exposure procedures.

Condition Healthy
Treatment Filtered Air, Wood Smoke
Clinical Study IdentifierNCT04297761
SponsorUniversity of North Carolina, Chapel Hill
Last Modified on28 February 2022


Yes No Not Sure

Inclusion Criteria

Age 18-35 years old healthy male and female (BMI (body mass index) values between 19 and 30, inclusive)
Physical conditioning allowing intermittent, mild exercise for 2 hours, and ability to complete the exposure exercise regimen to induce a minute ventilation rate of 12 L/min/m^2 for 15 min without exceeding 80% of projected maximal heart rate
Normal EKG (electrocardiogram)
Normal lung function based on the National Health and Nutrition Examination Survey (NHANES) III reference values
Forced vital capacity (FVC) equal to or greater than 80 % of that predicted for age, gender, ethnicity, and height
Forced expiratory volume in one second (FEV1) equal to or greater than 80% of that predicted for age, gender, ethnicity, and height
FEV1/FVC ratio equal to or greater than 80% of predicted values
Oxygen saturation greater than 94% at the time of physical exam
Have received the last dose of a COVID-19 vaccine at least 14 days prior to participation

Exclusion Criteria

Individuals with following conditions
a history of acute or chronic cardiovascular disease, chronic respiratory disease, cancer, rheumatologic disease, neuromuscular disease, or immunodeficiency state
blood pressure readings equal to or greater than 140 systolic and equal to or greater than 90 diastolic
diabetes (previously diagnosed or with hemoglobin A1c level equal to or greater than 6.4%)
asthma or a history of asthma
bleeding/clotting disorders
Individuals with a cardiovascular disease risk score greater than 10% using the American College of Cardiology/American Heart Association (ACC/AHA) Atherosclerotic Cardiovascular Disease (ASCVD) risk calculator. (Based on the 10-year risk of heart disease or stroke using the Atherosclerotic Cardiovascular Disease algorithm published in 2013 ACC/AHA Guideline on the Assessment of Cardiovascular risk.)
Individuals who have unspecified illnesses, which in the judgment of the medical staff might increase the risk associated with wood smoke inhalation will be a basis for exclusion
Individuals who are currently taking systemic steroids or oral anticoagulants long term
Individuals who are taking prescribed medications such as -blocker medications, that may impact the results of wood smoke challenge for the duration of the study. Other medications not specifically mentioned here may be reviewed by the medical staff prior to an individual's inclusion in the study. Use of other medications will be evaluated on a case-by-case basis. There is the potential that an individual's current medication use will preclude them from participating in the study at the current time, but they may be reassessed and potentially rescheduled for participation later based on the judgement of the medical staff
Individuals who are allergic to
chemical vapors or gases
tape or electrodes on their skin
Individuals who are pregnant, attempting to become pregnant or breastfeeding
Individuals who are currently smoking (including vaping, hookah and e-cigarette) or have smoking history within 1 year of study or have an equal to or greater than a 5-pack year smoking history
Individuals living with a smoker who smokes inside the house
Individuals who are regularly exposed to high levels of vapors, dust, gases, or fumes
Individuals who do not read, speak, or understand English well enough to give informed consent
Individuals that are unable to perform the exercise required for the study
Individuals who are unwilling or unable to stop taking any current dietary supplements or vitamins for the duration of the study. Prebiotics and probiotics are acceptable
Individuals who are unwilling to avoid caffeine for 12 hours prior to all visits
Individuals who are not willing to shave their facial hair, if any, that will affect the N95 facemask sealing for the N95 facemask fit test during the consenting visit
Temporary exclusion criteria
Individuals who have recent (within 6 month) abdominal and/or eye surgery, or with any types of hernia, as well as any other contraindications for raised intra-abdominal pressure
Individuals who have had an acute respiratory illness within 4 weeks
Individuals who have active allergies
Individuals who take over-the counter pain medications (such as aspirin, Advil, Aleve) or NSAIDs, or have taken these medications within the last 48 hours
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