《Continuous measurement of the dynamics of residential indoor and outdoor NO₂ and the contributions to human exposure》 

Website： https://doi.org/10.1016/j.envpol.2024.124881

Graphical Abstract:

Abstract:

In residential environment, NO₂ is an important air pollutant. Yet, the dynamics of indoor NO₂ and source contributions to human exposure are not well understood. Here, we conducted a continuous NO₂ measurement in and out of eight households in Guangzhou, China. Paired high time-resolution NO₂ data sets indoors (kitchen, living room) and outdoors (balcony) were obtained with NO₂ monitors. We summarized the indoor and outdoor NO₂ levels, identified temporal variation patterns, analyzed indoor-outdoor relationships, and quantified source contributions to indoor NO₂ exposure. Indoor NO₂ were overall higher than outdoor NO₂, and in most cases, the highest NO₂ levels were observed in the kitchen. NO₂ in the kitchen was characterized by multiple spikes associated with use of gas stoves, while NO₂ in the living room was also elevated but the peaks were generally smaller. The indoor-outdoor correlations were stronger in winter than in summer, and were stronger in nighttime than daytime. The sources contributing to indoor NO₂ were separated with a conceptual model. Overall, the outdoor NO₂ source contributed 73%–76% of the NO₂ in the kitchen, and 76%–85% in the living room. The source pattern was quite different: outdoor NO₂ sources were present indoors all the time; by contrast, indoor NO₂ sources were present sporadically but with a very high contribution. This has important implication to the exposure assessment that indoor NO₂ sources lead to short-term high exposure, and deserves attention regarding acute health effects.