Pollution characteristics of residential indoor nitrogen dioxide in six typical cities of China

Objective To investigate the distribution characteristics of residential indoor nitrogen dioxide (NO₂) in six typical cities of China, and to provide data support for the development of indoor environmental air quality standards and pollution prevention and control.

Methods In 2018, NO₂ was measured in the living room and bedroom of 281 households in six typical cities of China during the warm season (July to August) and the cold season (December to February in the next year). The sampling method was based on the Indoor Air Quality Standard (GB/T 18883-2002), and the modified Saltzman method was used for measurement.

Results In 2018, the median (P₂₅, P₇₅) mass concentrations were 0.026 (0.014, 0.040)mg/m³ for residential indoor NO₂ and 0.040 (0.030, 0.059) mg/m³ for outdoor NO₂ in 281 households in the six cities of China. The two independent samples non-parametric test showed that the median mass concentration of outdoor NO₂ was significantly higher than that of indoor NO₂ (z=8.76, P < 0.05), and the mass concentration of indoor NO₂ was significantly lower in the warm season than that in the cold season (z=-4.95, P < 0.05).

Conclusion There are differences in the distribution of residential indoor and outdoor NO₂ in the six typical cities of China, and indoor NO₂ distribution shows seasonal variation. Therefore, related departments should carry out extensive scientific research and take strict control measures to strengthen population health protection and control residential indoor NO₂ pollution.