Intervention efficacy in reducing childhood lower respiratory infections and indoor fine particulate matter among US households with wood heating stoves

Abstract

BACKGROUND AND AIM: Millions of rural United States (US) households are heated with wood stoves that can lead to high indoor concentrations of fine particulate matter (PM₂.₅). Wood stove use is associated with lower respiratory tract infection (LRTI) in children, the leading cause of childhood hospitalization in the US. In the Kids Air Quality Interventions for Reducing Respiratory Infections (KidsAIR) study, we assessed the impact of low-cost interventions on childhood LRTI and indoor PM₂.₅ in rural homes with wood stoves. METHODS: KidsAIR was a parallel three-arm (education, portable air filtration unit, control), post-only randomized trial in households from Alaska, Montana, and Navajo Nation with a wood stove and one or more children under five years of age. We tracked LRTI cases for two consecutive winter seasons and measured indoor PM₂.₅ over a six-day period during the first winter. We assessed results using two frameworks: intervention efficacy on LRTI and PM₂.₅ (intent-to-treat) and association between PM₂.₅ and LRTI (exposure-response). RESULTS:There were 61 LRTI cases from 14,636 child-weeks of follow-up among 454 children. In the intent-to-treat analysis, children in the education arm (Odds ratio: 1.0; 95% Confidence Interval [95%CI]: 0.4, 2.7) and air filtration arm (Odds ratio: 1.2; 95%CI: 0.5, 3.3) had similar odds of LRTI versus control. Geometric mean PM₂.₅ concentrations were similar to control among education arm (14% higher; 95%CI: -11, 45) and air filtration arm (13% lower; 95%CI: -32, 11) households. In the exposure-response analysis, odds of LRTI were 1.5 times higher (95%CI: 1.0, 2.1) per interquartile range increase in mean indoor PM₂.₅. CONCLUSIONS:We did not observe meaningful differences in LRTI or indoor PM₂.₅ in the air filtration or education arms versus control. The exposure-response analysis provides further evidence that biomass air pollution adversely impacts childhood LRTI. Our results highlight the need for novel, effective intervention strategies in households heated with wood stoves. KEYWORDS: Children's environmental health, Respiratory outcomes, Environmental epidemiology