Measured Nitrogen dioxide concentrations in outdoor air.

Crude accidental hourly values of nitrogen dioxide (NO2) at ground level in the outdoor air measured in the National Air Monitoring Network (LML). Nitrogen dioxide is a brown gas. Exposure to nitrogen dioxide (NO2) is linked to reduced lung function, an increase in respiratory complaints and asthma attacks, and increased susceptibility to infections. The concentration of nitrogen dioxide (NO2) in the Netherlands is increasing from the north to the south. Traffic is an important source of nitrogen dioxide. Along busy roads in the Randstad and the south of the Netherlands, the legal standard (40 micrograms/m³ on average over a year) is exceeded. In addition, NO2 arises from a reaction between nitric oxide and ozone. The weather and traffic pressures have a major impact on concentration.