Abstract

Results from the Dutch National Air Quality Monitoring Network (LML) show that several European air quality limit values were exceeded in the Netherlands between 2003 and 2006. This applied mainly to nitrogen dioxide, particulate matter (PM10) and ozone. The number of exceedances was especially high in 2003, partly due to weather conditions such as enduring dry episodes. Ozone concentration levels above the alert threshold (smog alert) were measured in 2003 and 2006, with concentration levels above the alert threshold occurring mostly during heat episodes. Measurements for nitrogen dioxide showed a yearly average concentration at city street locations above the European limit value at approximately half the measuring sites between 2003 and 2006. Yearly average concentrations measured at regional locations have changed relatively little in the past four years, remaining below the limit value for this entire period. Particulate matter concentrations have been relatively constant in the past few three years, after peaking in 2003. There is an EU standard for particulate matter for short- and long-term exposure of the population, which is represented by year and day average concentrations, with a maximum number of exceedances per year allowed. The year averages for the 2003 to 2006 period are less than the standard for long-term exposure. The maximum number of days showing average concentrations above the limit value was violated at several locations in 2006. Both nitrogen dioxide and particulate matter are characterized by a clear downward trend when measured over a long period of time (15 and 14 years, respectively). However, it is not possible to determine from the past seven years whether this trend is still valid.