Indoor and Outdoor Air Quality Assessment of So2 and No2 in Suburban Schools in Imphal, Manipur

Abstract

Air quality assessments for NO2 and SO2 levels in indoor and outdoor environments were conducted in three suburban schools in Imphal. Season-wise, the highest NO2 and SO2 concentrations were observed during winter, while the lowest occurred during the monsoon. The concentration of SO2 in the indoor air was comparatively cleaner than in the outdoor air. Similarly, indoor air was found to be cleaner than outdoor air with respect to NO2. The overall concentration obtained for the entire study period for SO2 was 4.9±1.5 µg m-3, and for NO2, it was 9.2±3.0 µg m-3. The concentrations of the two gases obtained during the study were below the NAAQs and WHO permissible limits. Seasonal variation of SO2 concentrations between the pre-monsoon period and monsoon months and also between the monsoon period and winter months (at p<0.001) was significant. For NO2, seasonal variation in the concentrations between the monsoon and winter (at p<0.001) was found significant. The estimated I/O ratios for the two studied gases, which were below one, plus the positive correlation between the classroom and campus environment concentrations of NO2 (r=0.96), and SO2 (r=0.96), reflected the influence of the indoor air quality by outdoor pollution sources. Data on similar studies for the country’s northeastern region, in particular, is scanty, and that’s why it may provide valuable insights to the scientific world.