Air pollution from traffic in city districts near major motorways

In order to assess exposure to air pollution from traffic of subjects living near motorways, traffic related air pollutants were measured indoors and outdoors in six city districts near motorways in the West of the Netherlands. Outdoor measurements of PM10, PM2.5, black smoke and benzene were conducted at four different distances from the roadside in two of the six city districts. NO2 was measured in all city districts. Indoor concentrations of PM10 and NO2 were measured in 12 schools in the same six city districts. Reflectance of indoor PM10 filters was measured to get an impression of black smoke concentrations indoors. Outdoor concentrations of black smoke and NO2 declined with distance from the roadside. No gradient was found for PM10, PM2.5 and benzene. The gradients for NO2 and black smoke were curvilinear and more evident in periods that the city districts had been downwind from the motorway for at least 33% of the time. PM10 concentrations in schools were high compared to outdoor concentrations and were not correlated with distance of the school from the motorway, traffic intensity and percentage of time downwind. Indoor black smoke concentrations were significantly correlated with truck traffic intensity and percentage of time downwind. NO2 concentrations in classrooms were significantly correlated with car and total traffic intensity, percentage of time downwind and distance of the school from the motorway.