Recent trends in nitrogen dioxide (NO2) levels in air (Ireland)

Date released: December 17, 2020

There is clear evidence that restrictions on movement and the prevalence of home-working relating to Covid-19 have had a dramatic impact on the concentrations of this pollutant, especially in our urban areas. During the period of ‘lockdown’ in March and April, concentrations at monitoring stations were observed to be up to 50% less when compared with previous years. The largest decreases were observed at urban traffic monitoring stations in the National Air Quality Monitoring Network.

More recent trends – second lockdown

Although concentrations have rebounded somewhat since the exiting of the second lockdown and subsequent easing of restrictions they are still well-below expected levels, especially for this time of year.
Figure 1 shows average NO2 concentrations by week for 2020 (year to date) for the Dublin urban traffic site at St. John’s Road West compared with concentrations for 2019 with a timeline of introduction of restrictions and subsequent easing of restrictions. This graph shows the fall in traffic pollution along with an emerging trend of increasing levels following easing of restrictions.

It can be observed that concentrations of NO2 at this particular monitoring site were above the EU annual legal limit value in 2019. However, concentrations in 2020 are averaging below this limit value as a result of the change in vehicle usage.

 Figure 1 in NO2 air quality bulletin

Figure 1 Average NO2 concentrations by week for 2020 (ytd) and 2019 at St. John's Road West in Dublin

The EPA will continue to monitor NO2 levels over the final weeks of the year to ascertain the impact of the easing of restrictions for the Christmas period. However, it must be noted that concentrations of air pollution are highly variable and can change quite substantially from day to day because of the variations in emissions (for example the impacts of commuter traffic, weekdays and weekend days) as well as changes in the weather conditions. This means that it is necessary to assess data for a substantial period-of-time. International guidance recommends using data averaged over a period of about a month to be able to accurately assess if there is a real change from typical levels.


  • All of our hourly air quality data is on our website (
  • Nitrogen dioxide is a pollutant that is emitted in ambient air when petrol or diesel is burned in internal combustion engines
  • Day to day variations in air pollution levels due to meteorological conditions can typically be up to 25% - 30%.
  • The European Environment Agency has developed a viewer that tracks the weekly average concentrations of nitrogen dioxide and particulate matter for member states. Users can select different pollutants, countries and cities. The viewer shows weekly averages for each city.
  • The National Ambient Air Quality Network includes roadside stations (“traffic stations”) as well as “background stations” that may be located in urban, suburban or rural areas.

With regard to Air Quality Policy, which is led by the Department of the Environment, Climate and Communications the EPA also notes:

  • In relation to improving air quality in Ireland, work is continuing on the National Clean Air Strategy, which will be the first all of government response reducing air pollution and promoting cleaner air. Emissions from the transport sector, including idling, will be considered in the context of the Strategy. Restrictions on car idling, including outside of schools, will be considered as part of this strategy.
  • In tandem with this, the Climate Action Plan includes a number of actions which will also have a significant impact on reducing emissions and improving air quality, including:
    • Putting 180,000 electric vehicles on our roads by 2025 and almost 1m by 2030
    • Ensuring the EV charging network underpins public confidence
    • Decarbonising the public transport fleet
    • Develop a 5 year cycling strategy and roll out 200km of new cycle lanes through bus connects
    • Developing a new Park and Ride Strategy, to reduce congestion and lower journey times
    • Developing a regulatory framework on low emission zones and parking pricing policies, and provide local authorities with the power to restrict access to certain parts of a city or a town to zero emission vehicles only
    • Legislating for no new fossil fuel vehicles to be sold from 2030 onwards.