Last Summer HS2 committed to monitoring pollution levels in Euston during the construction of HS2. In June 2016 they started to create a baseline from real data by placing monitoring tubes around the area for six months – June-December 2016.
They published their raw data results last month (February) and these are displayed below for the Regent’s Park Estate. The map shows the location of the tubes and the location of previous monitoring tubes for NO2 on the estate.
Four sites were chosen for six month data with two additional sites – Robert St by Woodhall and Varndell St by Harrington St monitored for one month – December 2016.
There is a lot of data on the map but they can be grouped into two types. One month data and five or six month data. The one month data is Autumn/Winter data either October or December and the 5/6 month data is from summer to winter with the number shown as an average. .
This graph shows the Regent’s Park Estate figures plotted over the 6 months.
For the minor roads within the estate the NO2 levels are lowest in the summer months and highest in the Winter months. For Hampstead Road the seasonal difference is lost.
Possible causes for this seasonal variation could be a general lower level of traffic during the summer holidays, higher use of home heating in winter, and a general tendency for pollutants to concentrate more during colder periods.
This is attributed both to heavier use of combustion power plants for wintertime home heating, as well as the fact that NO2 stays in the air longer in the winter. The atmospheric lifetime of NO2 is driven primarily by reactions initiated by sunlight. With less sunlight in the wintertime, reactions that break down NO2 are not easily initiated, and the NO2 is removed more slowly from the atmosphere. (US National Oceanic & Atmospheric Administration)
In the chart below the new HS2 data for Somers Town is plotted and it looks almost the same as for our estate.
The graph below of NO2 levels in an outer London Borough captures the seasonal variation over several years.
In conclusion it is clear that data readings during the Autumn and Winter months will usually be higher than during the Spring/Summer. It is important therefore to take the average over the seasons. The usual method is from June-December.