03/26/2025
By Khafayat Kadiri
Date: Wednesday, April 9, 2025
Time: 2:30 - 4 p.m.
Location: O’Leary Library, Room 512 (OLE 512)
Committee:
Chair: Serena Rajabiun, Ph.D., Public Health, Zuckerberg College of Health Sciences, UMass Lowell
David Turcotte, Sc.D., Economics, College of Fine Arts, Humanities and Social Sciences, UMass Lowell
Karyn Heavner, Ph.D., Public Health, Zuckerberg College of Health Sciences, UMass Lowell
Anila Bello, Sc.D., Public Health, Zuckerberg College of Health Sciences, UMass Lowell
Abstract:
Background: Approximately one-third (30%) of the U.S. population uses gas stoves, which are a significant source of indoor nitrogen dioxide (NO2) and particulate matter with a diameter of 2.5 microns (PM2.5). Gas stoves present a heightened health risk due to the close proximity of individuals to concentrated emissions during cooking. NO2 and PM2.5 have a significant impact on multiple health outcomes, particularly for vulnerable populations with pre-existing respiratory diseases. These pollutants can lead to acute exacerbations with an increased risk of hospitalization and death in older adults with asthma. The risk is especially pronounced in smaller, older and less-ventilated homes, which are more common among lower-income populations. Financial barriers often prevent these households from replacing gas stoves with electric alternatives or installing effective ventilation systems that exhaust outdoors, further exacerbating health disparities.
The primary objectives of this dissertation are to: 1. Identify factors influencing indoor NO2 and PM2.5 in low-income housing in Lowell, Massachusetts; 2. Evaluate the efficacy of air purifiers fitted with a HEPA and carbon filters in reducing indoor NO2 and PM2.5 emissions from gas stoves; and 3. Evaluate the impact of using air purifiers fitted with HEPA and carbon filters, as well as multi-trigger intervention, on health outcomes in of older adults with asthma.
Method: This study employed a pre- to post-test design to evaluate the impact of air purifiers fitted with HEPA and carbon filters on reducing NO2 and PM2.5. Participants were recruited between December 2020 and July 2022 in Lowell. Home visits were conducted every four months for 12 months; at each visit, we conducted environmental sampling, measuring indoor NO2, PM2.5, stove use, temperature and humidity over 5-7 consecutive days. Standardized questionnaires were used to collect data on factors influencing indoor NO2 and PM2.5 concentrations and health measures. At baseline, we compared indoor concentrations of NO2 and PM2.5 to the outdoor concentrations obtained from the nearest U.S. Environmental Protection Agency (EPA) monitoring station. Air purifiers with HEPA and carbon filters were introduced in the fourth month, and a multi-trigger intervention was introduced in the eighth month of the 12-month study timeline. Linear regression was used to evaluate the factors influencing indoor concentrations of NO2 and PM2.5 at baseline. Linear mixed models were used to predict NO2 and PM2.5 concentrations, and to estimate the changes in health outcomes resulting from the use of these interventions. Generalized linear mixed models were used to estimate the odds ratio for healthcare utilization associated with these interventions.
Results: The average age of the 71 participants who completed the study was 67 years, and 31% of them were male. At baseline in 73 homes, the average geometric mean (GM) for NO2 and PM2.5 were 21.8 (GSD = 2.1) ppb and 16.2 (GSD = 2.7) µg/m³, respectively. Indoor NO2 and PM2.5 concentrations exceeded outdoor concentrations significantly. At baseline, indoor NO2 levels were associated with season and the use of pilot light stoves. At baseline, indoor PM2.5 concentrations were associated with season and the use of air fresheners. In 69 homes, we observed a 36% (p < 0.001) reduction in indoor NO2 and a 45% (p < 0.001) reduction in indoor PM2.5 from pre-intervention to post-intervention. We observed that the increase in air purifier usage was associated with a decrease in NO2 and PM2.5 concentrations, and the increase in stove usage was associated with an increase in NO2 concentrations. In 71 participants, we observed improvements in health outcomes among older adults with asthma.
Conclusion: These findings support the development of targeted interventions to mitigate NO2 and PM2.5, as one-third of U.S. homes use gas stoves for cooking. Understanding the indoor factors that contribute to NO2 and PM2.5 will help inform policies addressing indoor air quality, gas stove emissions, and establish guidelines for the indoor environment, as current regulations primarily focus on outdoor air pollution.