The scandal over Volkswagen’s cheating over exhaust emissions testing has largely disappeared from the news, but the scandal over exhaust fumes and poor air quality in our cities remains.
Traffic emissions are now the major threat to clean air. Petrol and diesel vehicles emit a wide variety of pollutants: carbon monoxide, nitrogen oxides, particulate matter, and volatile organic compounds. These have an impact on our health, causing and worsening heart and lung diseases.
Pollutants are regulated under the EU National Emission Ceilings Directive and The National Emission Ceilings Regulations 2002, which sets limits on concentrations. Eg. NO2 must not exceed 200 μg/m3 more than 18 times a year.
Defra maintains a network of pollutant monitoring stations, which measure urban and roadside air quality, and background air quality in rural areas.
The Oxford Centre Roadside station in the basement of Oxford town hall measures the concentrations of nitric oxide, nitrogen dioxides and NOx as NO2 every hour. In 2015, NO2 exceeded 200 μg/m3 twice and 150 μg/m3 23 times. In 2016, it has so far exceeded 150 μg/m3 once.