Determinants of Indoor NO2 and PM2.5 Concentration in Senior Housing with Gas Stoves

Nitrogen dioxide (NO₂) and particulate matter of 2.5 microns (PM_2.5) are air pollutants that impact health, especially among vulnerable populations with respiratory disease. This study identifies factors influencing indoor NO₂ and PM_2.5 in low-income households of older adults with asthma who use gas stoves in Lowell, Massachusetts. Environmental sampling was conducted in 73 homes, measuring NO₂, PM_2.5, fractional stove-use, temperature, and humidity for 5-7 days. Participants were recruited between December 2020 and July 2022. Questionnaires were used to collect data on factors influencing indoor NO₂ and PM_2.5 concentrations. Daily outdoor NO₂ and PM_2.5 concentrations were obtained from a United States Environmental Protection Agency (EPA) monitoring station. Paired <i>t</i>-tests were conducted between indoor and outdoor NO₂ and PM_2.5 concentrations, and linear regression was used to evaluate factors influencing indoor NO₂ and PM_2.5 concentrations. The average indoor concentration for NO₂ and PM_2.5 were 21.8 (GSD = 2.1) ppb and 16.2 (GSD = 2.7) µg/m³, respectively. Indoor NO₂ and PM_2.5 concentrations exceeded outdoor concentrations significantly. In multiple regression models, season and pilot light stove use significantly predicted indoor NO₂. Season and air freshener use for 6-7 days/week significantly predicted indoor PM_2.5. Season-influenced higher indoor concentrations are likely due to reduced ventilation in colder months in the Northeast U.S.