The association between indoor and outdoor NO2 levels: A case study in 50 residences in an urban neighbourhood in New Zealand

• Published in: Sustainable cities and society 2020-05, Vol.56, p.102093, Article 102093
• Main Authors: Shaw, Caroline, Boulic, Mikael, Longley, Ian, Mitchell, Tamsin, Pierse, Nevil, Howden-Chapman, Philippa
• Format: Article
• Language: English
• Subjects: Housing intensification; Indoor NO2; NO2 level; Outdoor NO2; Transport; Urban development
• ISSN: 2210-6707; 2210-6715
• DOI: 10.1016/j.scs.2020.102093

•Inner-city residential intensification comes with risks of air pollution exposure (84 char with spaces).•Indoor- outdoor air pollution associations in residences are important to quantify.•We researched NO2 pollution in an inner-city suburb bisected by a busy road.•An increase in outdoor NO2 of 1 % was associated with a 5 % increase in indoor NO2.•Indoor and outdoor NO2 pollution sources need to be reduced. In the context of inner-city housing intensification, exploring the association between outdoor and indoor air quality is important to quantify any potential health risks. We undertook a cross-sectional case study on 50 residences in an inner-city neighbourhood scheduled for urban development, bisected by a busy road. We measured indoor and outdoor NO2, indoor temperature, and undertook a survey on demographic factors and household NO2 sources. We performed a linear regression to examine the association between indoor and outdoor NO2 (measured at the building facade) adjusting for potential confounders. Mean indoor and outdoor levels of NO2 were 8.4 and 12.5 μg/m3 respectively. The unadjusted model showed no significant association between indoor and outdoor NO2. In the fully-adjusted model, a 1 % increase in outdoor NO2 was associated with a 5 % increase in indoor NO2 (95 %CI: 1.2–8.8%). A weak association between indoor and outdoor NO2 was found. More intensive housing development in a transport corridor may be possible; however given the health risks of induced by air pollutants starts even at levels below WHO recommended levels, urban policy measures to reduce indoor and ambient air pollution are required.