The Improvement of Indoor Air and Health Effects After Air Purifier Intervention Among Susceptible Population in Industrial Area

Primary outcomes

1. Indoor air pollutants

   Time frame: One day 0 (before intervention) and day 1 (after intervention)

   The DustTrak DRX mass monitor (Model 8533, TSI, Shoreview, MN, USA) was used to measure PM1, PM2.5, PM4, PM10, and TSP continuously for 24 h, and UFPs were measured for 15 min at a time by using the P-Trak Ultrafine Particle Counter (Model 8525, TSI, Shoreview, MN, USA). The YesAir 15-channel indoor air quality monitor (Critical Environment Technologies Canada, Delta, British Columbia, Canada) was used to measure TVOC, NO2, SO2, CO, and CO2 continuously for 24 h.

   Airborne bacteria and fungi were collected using MAS-100 air sampler, which is a single-stage microbiological sampler with tryptic soy agar (Difco Laboratories, Detroit, MI, USA) and malt extract agar (Difco Laboratories, Detroit, MI, USA).

   Airborne endotoxin and mite samples were collected using 1-µm pore polytetrafluoroethylene (Teflon) membrane filters (Pall Corporation, Port Washington, NY, USA) placed in disposable plastic cassettes (37 mm; HIBLOW SPP-25 GA, Techno Takatsuki, Japan).

2. Fractional exhaled nitric oxide (FeNO)

   Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

   FeNO, considered an indicator of airway inflammation, was measured using the NIOX VERO device (Aerocrine AB, Solna, Sweden).

3. Blood pressure

   Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

   We employed the HEM-8712 device (Omron Healthcare Co. Ltd., Japan) to measure blood pressure.

4. Heavy metals

   Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

   We assessed 15 heavy metals in urine samples, including Cr, Mn, Fe, Co, Ni, As, Se, Rb, Sr, Cd, Cs, V, Cu, Zn, Mo, using an inductively coupled plasma mass spectrometer (ICP-MS, X-series II, Thermo Fisher Scientific, Germany).

5. Polycyclic aromatic hydrocarbons

   Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

   We used SCIEX 4000QTRAP Triple Quadrupole Hybrid Linear Ion Trap Mass Spectrometer to assess urinary polycyclic aromatic hydrocarbons, including 1-hydroxypyrene, 2-Hydroxyfluorene, 1-Hydroxyphenanthrene, 4-Hydroxyphenanthrene.

6. microRNA

   Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

   We evaluated miRNA, such as miR-146a-5p, miR-199a-5p, miR-21-5p, miR-222-3p, miR-155-5p, miR-29b-3p, miR-194-3p, using real time quantitative polymerase chain reaction (StepOnePlus™ Real-Time PCR System).

7. cell-free DNA

   Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

   We evaluated cell-free DNA, using real time quantitative polymerase chain reaction (StepOnePlus™ Real-Time PCR System).

8. Cytokines

   Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

   We evaluated cytokines, including IL-6, IL-8, IL-10, IL-13, IL-17A, IL-17F, IL-22, IL-25, IL-28A, IL-29, IL-31, IL-33, IL-34, and TGF-β1, using (Enzyme-linked immunosorbent assay, ELISA) assay (R & D Systems, Minneapolis, MN).

9. slow vital capacity (SVC)

   Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

   A multifunction spirometer (HI-801, Chest MI, Tokyo, Japan) was employed to assess the lung function.

10. forced expiratory volume in 1 s (FEV1)

    Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

    A multifunction spirometer (HI-801, Chest MI, Tokyo, Japan) was employed.

11. forced vital capacity (FVC)

    Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

    A multifunction spirometer (HI-801, Chest MI, Tokyo, Japan) was employed.

12. FEV1/FVC

    Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

    A multifunction spirometer (HI-801, Chest MI, Tokyo, Japan) was employed to assess the lung function.

13. peak expiratory flow (PEF)

    Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

    A multifunction spirometer (HI-801, Chest MI, Tokyo, Japan) was employed to assess the lung function.

14. maximal mid-expiratory flow (MMEF)

    Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

    A multifunction spirometer (HI-801, Chest MI, Tokyo, Japan) was employed to assess the lung function.

15. forced expiratory flow (FEF) at 25% (FEF25)

    Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

    A multifunction spirometer (HI-801, Chest MI, Tokyo, Japan) was employed to assess the lung function.

16. FEF50

    Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

    A multifunction spirometer (HI-801, Chest MI, Tokyo, Japan) was employed to assess the lung function.

17. FEF75

    Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

    A multifunction spirometer (HI-801, Chest MI, Tokyo, Japan) was employed to assess the lung function.

18. asthma control test (ACT)

    Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

    The asthma control test (ACT) served as a measure of asthma control, with high scores indicating better control of the condition.

19. Respiratory symptoms score

    Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

    The respiratory symptoms score evaluated in the questionnaire were stuffy nose, sneezing, runny nose, cough, shortness of breath, and chest tightness. The participants were asked to rate the severity of each respiratory symptom by using a 4-point scale, where 0, 1, 2, and 3 denoted no, mild, moderate, and severe symptoms, respectively.

20. COPD Assessment Test (CAT)

    Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

    The COPD Assessment Test (CAT) includes eight items (cough, sputum, breathlessness, chest tightness, confidence, activity, sleep and energy levels), rated on a 5-point scale (1 to 5).

21. modified Medical Research Council Dyspnea Scale (mMRC)

    Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

    The modified Medical Research Council Dyspnea Scale (mMRC) assessed dyspnea using a 5-grade scale (Grade 0 to Grade 4).

22. Breathlessness, Cough, and Sputum Scale (BCSS)

    Time frame: On day 0 ( before intervention), day 7 and day 13 ( after intervention)

    The Breathlessness, Cough, and Sputum Scale (BCSS) evaluated cough, sputum, and breathlessness using a 5-point scale (0 to 4).