Determinants of Indoor Carbonaceous Aerosols in Homes in the Northeast United States

BACKGROUND: Little is known about sources of residential exposure to carbonaceous aerosols, which include black carbon (BC), the elemental carbon core of combustion particles, and organic compounds from biomass combustion (delta carbon). OBJECTIVE: Assess the impact of residential characteristics on indoor BC and delta carbon when known sources of combustion (e.g. smoking) are minimized. METHODS: Between November 2012-December 2014, 125 subjects (129 homes) in Northeast USA were recruited and completed a residential characteristics questionnaire. Every 3-months, participants received an automated sampler to measure fine particulate matter (PM(2.5)) in their home during a weeklong period (N=371 indoor air samples) and were also questioned about indoor exposures. The samples were analyzed using a transmissometer at 880nm (reflecting BC) and at 370nm. The difference between the two wavelengths estimates delta carbon. Outdoor BC and delta carbon were measured using a central site aethalometer. RESULTS: Geometric mean indoor concentrations of BC and delta carbon (0.65μg/m³ and 0.19μg/m³, respectively), were greater than central site concentrations (0.53μg/m³ and 0.02μg/m³, respectively). Multivariable analysis showed that greater indoor concentrations of BC were associated with infrequent candle use, multi-family homes, winter season, lack of air conditioning, and central site BC. For delta carbon, greater indoor concentrations were associated with apartments, spring season, and central site concentrations.