It is food for thought that there is a complete disproportionality between limit values for NO2 in the EU versus the USA.
In Europe, the limit value for NO2 as a yearly average is established as 40 micrograms per m3, whereas it is 100 in the USA (!)
The limit is very difficult to meet in Europe in many urban areas and near to many airports, whereas in a regulatory sense, there are no problems in the USA.
Prof. Rex Britter (Cambridge University) delivered a very interesting presentation on this subject at the 11th International conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes (July 2007).
Some of the points he made were:
- There is a marked difference in the efforts in the US and Europe regarding NO2 as a pollutant, in research funding and, consequently, in national commitment of scientific expertise.
- There is evidence that NO2 is being used as a marker for a complex mixture of traffic related pollutants.
- It is not at al clear that mitigation efforts to reduce NO2 concentrations will be transferred to reductions in the health effects on the population.