Preliminary Assessment of Indoor PM2.5 Concentrations in Households on Hopi Lands

Introduction: Household reliance on biomass and solid fuels has resulted in an estimated 4.3 million pre-mature annual deaths globally. Despite the prevalent use in developing nations, recent studies suggest that low income rural populations of the United States, and other affluent countries, may experience similar exposures to HAPs due to incomplete combustion of fuels indoors.Methods: Indoor 24-hour PM2.5 concentration was measured during 2 winter heating seasons (2017 & 2018) and 1 summer non-heating season (2017) using real-time area monitors (pDR-1500) set at 1-minute logging intervals. Average 24-hour indoor PM2.5 concentration was compared across household primary heating fuel type during heating and non-heating seasons.Results: To date, 26 homes have been sampled during the heating season, of which 11 have complete follow-up data during the non-heating season. Indoor mean (SD) PM2.5 concentration in all households was 30.0 μg/m3 (120.8), and was 40.3 μg/m3 (145.8) during heating seasons and 9.9 μg/m3 (30.1) during the non-heating season. Coal-wood burning homes had indoor PM2.5 concentration of 57.9 μg/m3 (185.8) during heating (n=9) and 8.4 μg/m3 (19.3) during non-heating season (n=6). During the burning season, electrically heated (5.3 μg/m3 (5.8)) and electric-natural gas heated (9.9 μg/m3 (9.4)) homes had the lowest 24-hour concentration compared to homes that burned a combination of wood, coal & electricity (42.1 μg/m3 (156.8)), and coal, wood & natural gas (49.3 μg/m3 (111.3)) for heating.Discussion: Households that primarily burn wood and coal for heat had elevated indoor PM2.5 concentrations compared to homes heated with other fuel types. Even in homes using a combination of natural gas and electricity with wood and coal, indoor levels exceeded the EPA 24-hour ambient standard of 35 μg/m3. This project will continue to monitor indoor air quality and recruit households on the Hopi Lands.