Nitrogen dioxide concentration and health risk assessment at schools: Case study Tha sala District, Nakhon Si Thammarat province

A Traffic congestion around schools always problem for many schools. The biggest cause of the problem is the parent’s vehicles which they are dropping off and picking up their children from school. Other vehicle belongs to student and teacher in the school. Therefore, high air pollutant level usually found around school. Nitrogen dioxide (NO 2 ) is one of pollutant which associated with traffic density because it was emitted from internal combustion of vehicle. This gas causes inflammation of respiratory system and is a precursor of ground level ozone and particulate matter, which are associated with adverse health effects. It is also a source of acid rain which damage an ecological system. This study aims to measure concentration of NO 2 from three schools which have different traffic volume and building density in Tha sala district, Nakhon Si Thammarat Province, after that, the concentration was applied to evaluate health risk of exposure to NO 2 for residents who is living around schools including children and adult. The samples were collected by using passive samplers for 24 Hrs on the working day during February to May 2019. The results shown that the concentration of NO 2 at schools in semester start were ranged 48.6-78.1 µg/m 3 which were 1.5 time over that in semester break period. Pollutant concentration was relative with traffic volume in the area. Even though, the NO 2 level from all schools were accepted by the 24-hours standard of nitrogen dioxide in ambient air (<113 µg/m 3 ) but the toxicological risk assessment distinguished that the resident living around schools in Tha Sala district exposed to NO 2 above the recommended limits to human health