An interventional study of Purifying the air with a Pure Airbox device (Zonair 3D) and Using a sham air purifier (same device without filters) in Attention Impaired, Risk-Taking and Risk Behavior, sponsored by Barcelona Institute for Global Health. Completed at 1 site in Spain. Open to participants aged 13 Years to 16 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2025-06-12.
Sponsored by Barcelona Institute for Global Health · Not applicable, Interventional, and Prevention
Previous observational studies have reported an association between higher air pollution exposure and lower attention in children. With this project, the investigators aim to confirm this association in adolescents using an experimental design. In addition, the study will assess the relationship between air pollution exposure and individual preferences with respect to risk, time and social considerations. High school students in 3rd grade (ESO, 14-15 years of age) in different high schools in the Barcelona province (Spain) will be invited to participate. For each class in each high school, participating students will be randomly split into two equal-sized groups. Each group will be assigned to a different classroom where they will complete several activities during two hours, including an attention test (Flanker task) and a reduced version of the Global Preferences Survey. One of the classrooms will have an air purifier that will clean the air. The other classroom will have the same device but without the filters, so it will only re-circulate the air without cleaning it. Students will be masked to intervention allocation. The investigators hypothesize that students assigned to the clean air classroom will have better scores in the attention test, and that decision-making will also present differences in the two classrooms.
Barcelona Institute for Global Health is the lead sponsor of 24 studies on the registry; 5 are open to participants now.
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Exclusion Criteria:
Purifying the air with a Pure Airbox device (Zonair 3D). Use of air purifier (Pure Airbox, Zonair 3D) in the classroom 30 minutes before the participants enter the room and during the 2 hours of the experiment.
Other: Purifying the air with a Pure Airbox device (Zonair 3D)
Using a sham air purifier (same device without filters). Use of the same air purifier but without filters, so that it only recirculates the air without purifying it. Used for the same time period than the other arm.
Other: Using a sham air purifier (same device without filters)
Purifying the air of the classroom where the experiment is conducted using a Pure Airbox device (Zonair 3D)
Also known as: Air filtering, Air cleaning
Use the air purifier (Pure Airbox, Zonair 3D) without filters in the classroom where the experiment is conducted
Also known as: Sham air cleaner
Response Speed Consistency Throughout the Attention Network Task-Flanker Task (Post ANT)
This is a measure related to attentiveness that is calculated as hit reaction time standard error for correct responses (HRT-SE). A higher HRT-SE indicates highly variable reactions during the ANT test that is related to inattentiveness. A lower HRT-SE indicates indicates consistent reaction times and thus, a better attention performance.
Time frame: Obtained from a test administered approximately 90 minutes after entering the classroom
Combined Risk Taking Score
The "Combined risk taking score" measures how willing the person is to take risks and is calculated as 0.4729985 × "Risk preference score" + 0.5270015 × "Willingness to take risks", as defined in Falk et al (2018). The "Combined risk taking score" is a weighted average of two z-scores ("risk preference score" and "willingness to take risks" score), and therefore it can be interpreted as a z-score. The central value of "Combined risk taking score" is 0 and represents the population mean. The higher the values of the "Combined risk taking score", the more willing is the person to take risks. The "Risk preference score" is the final node in the risk tree (see the online appendix of Falk et al (2018)), which is a value between 1 and 32, ranked by the level of risk aversion, which was then transformed to a z-score. The "Willingness to take risks" refers to the answer to the question on one's willingness to take risks, with values from 0 to 10), which was then transformed to a z-score.
Time frame: Obtained from a test administered approximately 100 minutes after entering the classroom
Combined Patience Score
The "Combined patience score" measures the patience of the person and is calculated as 0.7115185 × "Time preference score" + 0.2884815 × "Self assessment of patience", as defined in Falk et al (2018). The "Combined patience score" is a weighted average of two z-scores ("time preference score" and "self assessment of patience" score), and therefore it can be interpreted as a z-score. The central value of "Combined patience score" is 0 and represents the population mean. The higher the values of the "Combined patience score" the more patience the person has. The "Time preference score" was obtained from the final node in the time tree (see the online appendix of Falk et al (2018)), which is a value between 1 and 32, ranked by the level of patience, which was then transformed to a z-score. The "Self assessment of patience" score refers to the answer to the question on the self-assessment of patience, with values from 0 to 10, which was then transformed to a z-score.
Time frame: Obtained from a test administered approximately 100 minutes after entering the classroom
Positive Reciprocity Score
The "Positive reciprocity score" measures positive reciprocity. A person with high reciprocity agrees with the statement "When someone does me a favor, I am willing to return it". The score is calculated as 0.4847038 × "Willingness to return favor" + 0.5152962 × "Size of gift", as defined in Falk et al (2018). The "Positive reciprocity score" is a weighted average of two z-scores ("willingness to return a favor" score and "size of gift" score), and therefore it can be interpreted as a z-score, with the central value of 0 representing the population mean. Higher values of the score imply more positive reciprocity. "Willingness to return favor" refers to the answer to the question on the willingness to return a favor, ranked from 0 to 10 and then transformed to a z-score. "Size of gift" refers to the answer to the question on the reported size of the gift that would return to a stranger, from a list of 7 possible values (from 0 to 30€, by 5€ steps), then transformed to a z-score.
Time frame: Obtained from a test administered approximately 100 minutes after entering the classroom
Altruism Score
The "Altruism score" measures the altruism of a person and is calculated as 0.6350048 × "Willingness to give to good causes" + 0.3649952 × "Hypothetical donation", as defined in Falk et al (2018). The "Altruism score" is a weighted average of two z-scores ("willingness to give to good causes" score and "hypothetical donation" score), and therefore it can be interpreted as a z-score, with the central value of 0 representing the population mean. Higher values of the score imply more altruism. "Willingness to give to good causes" refers to the answer to the question on the willingness to give to good causes, ranked from 0 to 10 and then transformed to a z-score. "Hypothetical donation" refers to the answer to the question on the size of the hypothetical donation one would be willing to make, transformed to a z-score.
Time frame: Obtained from a test administered approximately 100 minutes after entering the classroom
Trust Score
Answer to the question "I assume that people have only the best intentions", which is ranked from 0 to 10. Higher values imply more trust.
Time frame: Obtained from a test administered approximately 100 minutes after entering the classroom
Impulsivity (From ANT)
Number of incorrect responses (responses made in the opposite direction to the direction of the target arrow) Lower score indicates a better attention performance. Total range score: 0-38.
Time frame: Obtained from a test administered approximately 90 minutes after entering the classroom
Selective Attention (From ANT)
Number of omission errors (failure to respond) Lower score indicates a better attention performance Total range score: 0-21. Higher values represent a worse outcome
Time frame: Obtained from a test administered approximately 90 minutes after entering the classroom
Alerting Score (From ANT)
Alerting represents the ability to maintain a state of high vigilance to incoming stimuli It is calculated by subtracting the median reaction time for double cue from median reaction time for the no cue condition (calculations performed after removing the incongruent trials). A lower score indicates a better attention performance
Time frame: Obtained from a test administered approximately 90 minutes after entering the classroom
Orienting Score (From ANT)
Orienting is the ability to select information and it is calculated by subtracting the median reaction time for spatial cue from the reaction time for central cue (calculations performed after removing the incongruent trials).A lower score indicates a better attention performance
Time frame: Obtained from a test administered approximately 90 minutes after entering the classroom
Conflict Score (Executive Attention) (From ANT)
Conflict generally refers to the ability to monitor and resolve conflict among responses and in this study it is calculated as the median reaction time for each flanker condition (across cue conditions) and subtracting the congruent from the incongruent reaction times. A lower score indicates a better attention performance
Time frame: Obtained from a test administered approximately 90 minutes after entering the classroom
Self Assessment of How Good They Are in Math
Answer to the question on math skills, ranging from 0 to 10. The higher the score, the better the person feels s/he is doing in math.
Time frame: Obtained from a test administered approximately 100 minutes after entering the classroom
To recruit participants (students), the objectives and design of the study were presented during teacher training sessions opened to all science teachers from all high schools of Barcelona metropolitan area. Teachers interested in participating signed up in an online form. Teachers from 33 high schools reached out to the research team to participate.
| Milestone | Purified Air | Normal Air |
|---|---|---|
| Started | 1068 | 1055 |
| Completed | 1067 | 1054 |
| Not completed | 1 | 1 |
| Withdrew: Appointment to the doctor | 1 | 1 |
This is a measure related to attentiveness that is calculated as hit reaction time standard error for correct responses (HRT-SE). A higher HRT-SE indicates highly variable reactions during the ANT test that is related to inattentiveness. A lower HRT-SE indicates indicates consistent reaction times and thus, a better attention performance.
| ms | Purified Air | Normal Air |
|---|---|---|
| Response Speed Consistency Throughout the Attention Network Task-Flanker Task (Post ANT) | 161.3 (112.7 to 232.4) | 160.2 (112.4 to 234.7) |
The "Combined risk taking score" measures how willing the person is to take risks and is calculated as 0.4729985 × "Risk preference score" + 0.5270015 × "Willingness to take risks", as defined in Falk et al (2018). The "Combined risk taking score" is a weighted average of two z-scores ("risk preference score" and "willingness to take risks" score), and therefore it can be interpreted as a z-score. The central value of "Combined risk taking score" is 0 and represents the population mean. The higher the values of the "Combined risk taking score", the more willing is the person to take risks. The "Risk preference score" is the final node in the risk tree (see the online appendix of Falk et al (2018)), which is a value between 1 and 32, ranked by the level of risk aversion, which was then transformed to a z-score. The "Willingness to take risks" refers to the answer to the question on one's willingness to take risks, with values from 0 to 10), which was then transformed to a z-score.
| Z-score | Purified Air | Normal Air |
|---|---|---|
| Combined Risk Taking Score | -0.0210 (-0.4730 to 0.4552) | -0.0121 (-0.4580 to 0.4738) |
The "Combined patience score" measures the patience of the person and is calculated as 0.7115185 × "Time preference score" + 0.2884815 × "Self assessment of patience", as defined in Falk et al (2018). The "Combined patience score" is a weighted average of two z-scores ("time preference score" and "self assessment of patience" score), and therefore it can be interpreted as a z-score. The central value of "Combined patience score" is 0 and represents the population mean. The higher the values of the "Combined patience score" the more patience the person has. The "Time preference score" was obtained from the final node in the time tree (see the online appendix of Falk et al (2018)), which is a value between 1 and 32, ranked by the level of patience, which was then transformed to a z-score. The "Self assessment of patience" score refers to the answer to the question on the self-assessment of patience, with values from 0 to 10, which was then transformed to a z-score.
| Z-score | Purified Air | Normal Air |
|---|---|---|
| Combined Patience Score | -0.1453 (-0.6474 to 0.6330) | -0.0732 (-0.6516 to 0.6575) |
The "Positive reciprocity score" measures positive reciprocity. A person with high reciprocity agrees with the statement "When someone does me a favor, I am willing to return it". The score is calculated as 0.4847038 × "Willingness to return favor" + 0.5152962 × "Size of gift", as defined in Falk et al (2018). The "Positive reciprocity score" is a weighted average of two z-scores ("willingness to return a favor" score and "size of gift" score), and therefore it can be interpreted as a z-score, with the central value of 0 representing the population mean. Higher values of the score imply more positive reciprocity. "Willingness to return favor" refers to the answer to the question on the willingness to return a favor, ranked from 0 to 10 and then transformed to a z-score. "Size of gift" refers to the answer to the question on the reported size of the gift that would return to a stranger, from a list of 7 possible values (from 0 to 30€, by 5€ steps), then transformed to a z-score.
| Z-score | Purified Air | Normal Air |
|---|---|---|
| Positive Reciprocity Score | -0.0186 (-0.3644 to 0.5352) | -0.0359 (-0.5999 to 0.5372) |
The "Altruism score" measures the altruism of a person and is calculated as 0.6350048 × "Willingness to give to good causes" + 0.3649952 × "Hypothetical donation", as defined in Falk et al (2018). The "Altruism score" is a weighted average of two z-scores ("willingness to give to good causes" score and "hypothetical donation" score), and therefore it can be interpreted as a z-score, with the central value of 0 representing the population mean. Higher values of the score imply more altruism. "Willingness to give to good causes" refers to the answer to the question on the willingness to give to good causes, ranked from 0 to 10 and then transformed to a z-score. "Hypothetical donation" refers to the answer to the question on the size of the hypothetical donation one would be willing to make, transformed to a z-score.
| Z-score | Purified Air | Normal Air |
|---|---|---|
| Altruism Score | 0.1118 (-0.5652 to 0.6197) | 0.0597 (-0.6023 to 0.6754) |
Answer to the question "I assume that people have only the best intentions", which is ranked from 0 to 10. Higher values imply more trust.
| score on a scale | Purified Air | Normal Air |
|---|---|---|
| Trust Score | 5 (4 to 7) | 5 (4 to 7) |
Number of incorrect responses (responses made in the opposite direction to the direction of the target arrow) Lower score indicates a better attention performance. Total range score: 0-38.
| total score | Purified Air | Normal Air |
|---|---|---|
| Impulsivity (From ANT) | 2 (1 to 4) | 2 (1 to 4) |
Number of omission errors (failure to respond) Lower score indicates a better attention performance Total range score: 0-21. Higher values represent a worse outcome
| total score | Purified Air | Normal Air |
|---|---|---|
| Selective Attention (From ANT) | 0 (0 to 0) | 0 (0 to 0) |
Alerting represents the ability to maintain a state of high vigilance to incoming stimuli It is calculated by subtracting the median reaction time for double cue from median reaction time for the no cue condition (calculations performed after removing the incongruent trials). A lower score indicates a better attention performance
| ms | Purified Air | Normal Air |
|---|---|---|
| Alerting Score (From ANT) | 42 (18 to 68.5) | 44.5 (17 to 73) |
Orienting is the ability to select information and it is calculated by subtracting the median reaction time for spatial cue from the reaction time for central cue (calculations performed after removing the incongruent trials).A lower score indicates a better attention performance
| ms | Purified Air | Normal Air |
|---|---|---|
| Orienting Score (From ANT) | 12.5 (-11.5 to 39) | 13.5 (-11.5 to 37.5) |
Conflict generally refers to the ability to monitor and resolve conflict among responses and in this study it is calculated as the median reaction time for each flanker condition (across cue conditions) and subtracting the congruent from the incongruent reaction times. A lower score indicates a better attention performance
| ms | Purified Air | Normal Air |
|---|---|---|
| Conflict Score (Executive Attention) (From ANT) | 75 (57.5 to 93.5) | 75 (58 to 95.5) |
Answer to the question on math skills, ranging from 0 to 10. The higher the score, the better the person feels s/he is doing in math.
| score on a scale | Purified Air | Normal Air |
|---|---|---|
| Self Assessment of How Good They Are in Math | 6 (3 to 8) | 6 (3 to 8) |
Non-serious events are listed at a 0% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Purified Air | — | — | — |
| Normal Air | — | — | — |
Students not having completed both ANT tests or showing low accuracy were excluded from the main analysis. An ANT test was considered a low accuracy test when the number of correct responses was less than 70%. Thus, a total of 68 participants from purified air group and 60 from normal air group were excluded from analysis (analytical sample, N = 1993)
| Age, Continuous(years) | Purified Air | Normal Air | Total |
|---|---|---|---|
| Median | 14.7 (14.6 to 14.8) | 14.7 (14.6 to 14.9) | 14.7 (14.6 to 14.9) |
| Sex/Gender, Customized(Participants) | Purified Air | Normal Air | Total |
|---|---|---|---|
| Sex — Female | 514 | 483 | 997 |
| Sex — Male | 481 | 507 | 988 |
| Sex — Other | 4 | 4 | 8 |
| Race and Ethnicity Not Collected(Participants) | Purified Air | Normal Air | Total |
|---|---|---|---|
| Count of participants | — | — | 0 |
| PMA-R, Primary Mental Aptitudes - Reasoning(score) | Purified Air | Normal Air | Total |
|---|---|---|---|
| Median | 17 (12 to 20) | 16 (11 to 20) | 16 (12 to 20) |
| HRT-SE, hit reaction time standard error(ms) | Purified Air | Normal Air | Total |
|---|---|---|---|
| Median | 164.1 (114.5 to 237.3) | 158.6 (110.7 to 238.5) | 161.7 (112.6 to 237.9) |
| Impulsivity(total score) | Purified Air | Normal Air | Total |
|---|---|---|---|
| Median | 2 (1 to 3) | 2 (1 to 3) | 2 (1 to 3) |
| Selective attention(total score) | Purified Air | Normal Air | Total |
|---|---|---|---|
| Median | 0 (0 to 1) | 0 (0 to 0) | 0 (0 to 0) |
| Alerting(ms) | Purified Air | Normal Air | Total |
|---|---|---|---|
| Median | 34.5 (5 to 66) | 35.5 (10 to 64.5) | 34.5 (7.5 to 65.5) |
2 further baseline measures are reported on the registry.
Documents are hosted by the registry — open the source record to download them.
Plan to share: Yes — All collected IPD except identifying information for participants or high schools will be shared
Supporting information: Study protocol, Sap, Analytic code
This study is completed, as verified in Jun 2025. You cannot join it, but the record below documents what was studied.
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Barcelona Institute for Global Health