A randomized trial of air cleaners and a health coach to improve indoor air quality for inner-city children with asthma and secondhand smoke exposure

Abstract

Objective: To test an air cleaner and health coach intervention to reduce secondhand smoke exposure compared with air cleaners alone or no air cleaners in reducing particulate matter (PM), air nicotine, and urine cotinine concentrations and increasing symptom-free days in children with asthma residing with a smoker.

Design: Randomized controlled trial, with randomization embedded in study database.

Settings: The Johns Hopkins Hospital Children's Center and homes of children.

Participants: Children with asthma, residing with a smoker, randomly assigned to interventions consisting of air cleaners only (n = 41), air cleaners plus a health coach (n = 41), or delayed air cleaner (control) (n = 44).

Main outcome measures: Changes in PM, air nicotine, and urine cotinine concentrations and symptom-free days during the 6-month study.

Results: The overall follow-up rate was high (91.3%). Changes in mean fine and coarse PM (PM(2.5) and PM(2.5-10)) concentrations (baseline to 6 months) were significantly lower in both air cleaner groups compared with the control group (mean differences for PM(2.5) concentrations: control, 3.5 μg/m(3); air cleaner only, -19.9 μg/m(3); and air cleaner plus health coach, -16.1 μg/m(3); P = .003; and PM(2.5-10) concentrations: control, 2.4 μg/m(3); air cleaner only, -8.7 μg/m(3); and air cleaner plus health coach, -10.6 μg/m(3); P = .02). No differences were noted in air nicotine or urine cotinine concentrations. The health coach provided no additional reduction in PM concentrations. Symptom-free days were significantly increased [corrected] in both air cleaner groups compared with the control group (P = .03).

Conclusion: Although the use of air cleaners can result in a significant reduction in indoor PM concentrations and a significant increase in symptom-free days, it is not enough to prevent exposure to secondhand smoke.

Trial registration: ClinicalTrials.gov NCT00466024.

Figure 1.

Participant recruitment and retention flowchart.

Figure 2.

Box plots for mean differences in fine (aerodynamic diameter of <2.5 μm) and coarse (difference between particles with an aerodynamic diameter of 10 and 2.5 μm) particulate matter (PM_2.5 and PM_2.5–10, respectively) concentrations from the 6-month follow-up, minus the baseline concentrations in the control compared with both air cleaner groups. We used the Mann-Whitney test to compare the change in PM concentrations between groups. The horizontal line in the middle of each box indicates the median, while the top and bottom borders of the box mark the 75th and 25th percentiles, respectively. The whiskers above and below the box mark the maximum and minimum values or 1.5 times the interquartile range. The points beyond the whiskers are outliers.