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