HEPA Filter Reduces Indoor Airborne Traffic Particles, Improves QoL in Children With Asthma

air filter in bedroom
Investigators found data that explored at-home high-efficiency particulate air filtration as an aid in improvement of quality of life in children with asthma.

At-home high-efficiency particulate air (HEPA) filtration reduces indoor concentrations of airborne traffic particles and is associated with improvements in quality of life (QoL) measures in children with asthma, study results published in Indoor Air suggest.

The Cincinnati Childhood Allergy and Air Pollution Study cohort was used to recruit children between the ages of 10 and 16 years with a physician diagnosis of asthma. A total of 43 children with asthma were included in the study if they lived in a home with high traffic-related airborne pollutant (TRAP) exposure.

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Patients were randomly assigned to either an at-home HEPA filter or a placebo “dummy” air purifier for a 1-month period. Following the first month, patients underwent a 1-month washout period and then crossed over to the alternate treatment for another month. The researchers compared samples of airborne particles in each child’s bedroom 48 hours before and 48 hours after the HEPA and placebo periods. In addition, asthma control (Asthma Control Questionnaire [ACQ]) and quality of life (Mini Asthma Quality of life Questionnaire [AQLQ]) measures were assessed before and after each treatment.

Significant reductions were observed in several indoor concentrations of traffic air particles from pre-HEPA to post-HEPA but not with the placebo air purifier. Using the HEPA filter in patients with impaired QoL at baseline, there were greater reductions in particulate matter <2.5 μm (8.0 μg/m3 to 4.8 μg/m3), black carbon (0.3 μg/m3 to 0.05 μg/m3), ultraviolet absorbing particulate matter (2.3 μg/m3 to 0.7 μg/m3), and fungal spores (149 μg/m3 to 132 μg/m3). Similar improvements were observed in patients with poorly controlled asthma at baseline.

There were also significant improvements in ACQ scores (1.3 to 0.9; P =.003) and AQLQ scores (4.9 to 5.5; P =.02) with the HEPA filter in patients with poorly controlled asthma and lower baseline QoL.

Study limitations included the small sample size, the lack of assessment of allergen sensitization, and the short treatment period.

The investigators wrote that their “study suggests that significant public health benefits could be derived from reducing personal TRAP exposure,” considering the high costs associated with “developing new biologic drugs for poorly controlled asthma with less consideration and evaluation of environmental inventions.”


James C, Bernstein DI, Cox J, et al. HEPA filtration improves asthma control in children exposed to traffic-related airborne particles [published online November 19, 2019]. Indoor Air. doi:10.1111/ina.12625