Indoor Nitrogen Dioxide Investigation and Health Risk Assessment in Primary Schools at Rayong City, Thailand

Indoor air pollution in schools adversely affects children’s health due to the inhalation of nitrogen dioxide (NO₂), which is a toxin released by motor vehicles. This research aims to measure NO₂ levels around schools in an attempt to evaluate indoor air quality within the framework of a health risk assessment. Air samples were collected in schools from indoor and outdoor locations. The results for indoor NO₂ concentrations in urban, industrial and rural areas ranged between 12.8 - 32.9, 11.7 - 36.6 and 7.0 - 17.5 µg/m³, while the values for outdoor areas ranged between 13.0 - 43.7, 15.5 - 37.6 and 10.1 - 32.6 µg/m³, respectively. The indoor NO₂ concentrations measured in urban and industrial areas were significantly higher than those in rural areas (p<0.05), while the values for urban and industrial areas were not significantly different (p>0.05). The mean of indoor and outdoor NO₂ concentrations were not significantly different (p>0.05) and these values were more significantly correlated (r = 0.526). Moreover, the values of NO₂ concentrations and meteorological factors were not significantly correlated, thereby rejecting the hypothesis that meteorological factors might have affected indoor NO₂ concentrations. These findings clearly stress the relationship that exists between NO₂ concentrations and the level of local activity, for example traffic intensity. Hazard quotient (HQ) values indicated that human health risks linked to NO₂ inhalation were of the low hazard type. It can be concluded that local activities played a significant role in the emission of NO₂ and the level of indoor air quality in classrooms.

Keywords: indoor air pollution; nitrogen dioxide; passive sampling; hazard quotient (HQ)

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                                           E-mail: susira.b@sciee.kmutnb.ac.th