Abstract
BACKGROUND: There is increasing attention on the effects of residential fossil fuel combustion, particularly the use of natural gas or oil, on indoor air quality. Given the prevalent use of natural gas in Canadian homes, understanding its influence on indoor air quality is important. OBJECTIVE: This study investigated associations between indoor levels of nitrogen dioxide (NO(2)), carbon monoxide (CO), formaldehyde, and acetaldehyde with potential emission sources and other influencing factors in 344 homes in four Canadian cities. METHODS: Using mixed models and general linear models, we evaluated the associations between potential sources and pollutant concentrations, conducting both city-specific and pooled analyses for winter and summer seasons. RESULTS: Our findings indicated that gas stoves, present in 24% of the homes, were significantly associated with increased indoor NO(2) concentrations, resulting in a 191% increase in winter and a 114% increase in summer. Additionally, the presence of gas stoves was strongly associated with a 43% increase in peak hourly CO levels in winter. The presence of gas clothes dryers was significantly associated with increased indoor NO(2) levels (47% in summer and 54% in winter). Oil heating was significantly associated with a 58% increase in winter indoor NO(2) levels. Gas heating was associated with a 62% increase in winter NO(2) levels in older homes (built before 1949), with marginal significance. Aldehyde levels were primarily associated with off-gassing from building materials and household activities. Other factors associated with indoor pollutant levels included housing characteristics, occupant behaviors, indoor environmental conditions, and outdoor sources. IMPACT: This study enhances understanding of the association between fossil fuel combustion and indoor air quality in predominantly detached homes. It highlights differences in pollutant levels between homes with gas and electric cooking, which can inform advice on cooking practices to reduce emissions in homes.