City of Westminster
"Recent changes - neither good for health nor carbon budget?"

The following chart shows how the concentration of NO2 (averaged over consecutive periods of 12-months) has changed since 2015 at some sites in the City of Westminster where air quality is now being measured continuously for reference purposes:

Source: based on London Air (Tools,  Data Downloads).  Data for 2022 provisional.

The steep reduction in NO2 pollution in the vicinity of Selfridges during 2015 and 2016 reflects the success of efforts to revise traffic flows and tighten regulations concerning emissions from buses, taxis and the like.  The decrease in concentrations along the Marylebone Road is primarily attributable to the first phase of the ULEZ.

Responses to the covid-19 pandemic explain the improvement between March 2020 and early 2021.  The subsequent trend suggests that the relaxation of those responses has been matched by vehicle users anticipating the second phase of the ULEZ.


The following chart shows data similar to the chart above -for other sites in Westminster:

Source: based on London Air (Tools,  Data Downloads).  Data for 2022 provisional.

The following chart shows PM2.5 concentrations measured in Westminster since 2015:

Source: based on London Air (Tools,  Data Downloads).  Data for 2022 provisional.

The UK government has recently consulted the public about changing the legal limit - to double the World Health Organisation guideine, by 2040.  This seems to ignore that, even in London, concentrations are already close to 10 μg/m and that that target could be achieved by 2030, especially with the right measures and the allocation of sufficient powers to the GLA.

The following chart shows PM10 concentrations measured in Westminster since 2015:

Source: based on London Air (Tools,  Data Downloads).  Data for 2022 provisional.


A number of Breathe London sensors are located at sites across Westminster.  These set out to monitor both NO2 and PM2.5, but not to reference quality (doing do so when their solar panels supply their batteries with sufficient energy).

Click here for charts deriving from Breathe London phase 2



Click here for Westminster City Council NO2 diffusion tube data


Westminster greenhouse gas emissions
less coal-fired electricity but locking in other carbon-based power;

council direct emissions c.2% of total

Source: based on UK local authority and regional greenhouse gas emissions dataset

Westminster City Council stopped sytematically monitoring concentrations of NO2 using diffusion tubes in 2010, the year by which those concentrations should have declined to less than the legal limit (40 micrograms per cubic metre).  On the recommendation of both DEFRA and the GLA, the Council has re-started.  However, November 2020 is the first month for which measurements have been published, earlier months seeming to have been spent testing diffusion tubes from at least one other supplier.

It is standard practice across local authorities in London to publish such data in Air Quality Annual Status Reports for the given calendar year - but only after approval by the GLA and DEFRA.  During recent years, approval has taken several months longer than it used to.  This tends to reflect lack of government committment, despite ever increasing evidence of the health, social and economic costs of air polution, and despite the climate emergency. The current time lag of 18 months to two years is inexcusable.

NO2 concentrations are an important, albeit weak, proxy for greenhouse gas emissions in so far as NO2 in urban areas derives predominaoty from combustion in diesel vehicles and methane ("natural" gas) for heating and cooking.  As such, local authorities should publish - on an explicitly provisional basis - their NO2 diffusion tube measurements within two months of the end of the period during which the tubes are exposed.

Click here for a map of NO2 concentrations (?in 2017) across the Oxford Street District.


The following chart derives from the public portal for four schools in Westminster

Click the chart for PM2.5 and ozone

The cold snap contributed to the December spike, the increase in NO2 since summer reflects seasonal variation.


Click here for charts deriving from and air quality audit of schools in Westminster

A summary report of the audits of air quality which the Council carried out for schools across Wesminster during 2019 and 2020 states that NO2 concentrations adjacent more than half of those schools exceeded the legal limit.  That report neither identified which those schools were nor explained why, despite having authority over most roads adjacent those schools, NO2 concentrations remain above the legal limit a decade after they should have been below it.  The Council's subsequent action includes making recommendations and offering up to 10,000 per school - but not reducing the pollution at source, for example, from traffic on roads managed by the Council.  One school has been allocated a budget of roughly 25,000 for air filters - with no apparent provision for optimising their location or monitoring their effectiveness.  This adds to the burden of the "innocent victim" and may serve to reduce pressure to addres the problem.

Deploying diffusion tubes - and publishing measured data every month - would, at minimal cost, help the Council, residents and users guage the impact of specific projects, such as during and after the costly, contentious urban greening and road works of the the Marylebone Low Emission Neighbourhood.  Concerning the latter, the Council chose not to do so - monitoring was presumably a condition of the one million UK GLA grant it received for the project.

Court rulings subsequent to cases brought by ClientEarth oblige government to ensure NO2 concentrations decline to beneath the legal limit in the shortest possible time. During September 2021, based on 16 years of evidence and research, the World Health Organisation revised its advice concerning the maximum annual average concentration of NO2 and particulate matter PM2.5 - respectively, they are now four and five times less than the legal limit.  Central government has passed the buck to local councils, obliging them to demonstrate that they are doing all they can within their power to comply. 

It would obviously be wrong to assume that local councils have sufficient power to design and implement policies which meet that legal obligation, especially in London where regional government might have much greater influence.  That said, the Council has now declared a Climate Emergency (but its more recent City Plan 2019-2040 almost completely ignores this, thereby almost inviting litigation). The Westminster Climate Emergency Action Plan seeks to achieve no more than half of the emissions reduction between business as usual and what the Tyndal Centre urges by 2040 [page 15].

Research by Imperial College [see / listen from minute  15:10] indicates that NO2 concentrations are unlikely to meet that requirement, particularly along those busy streets (and in their neighbourhood), even when the proposed Ultra Low Emission Zone is fully implemented across London.  A substantial reduction in vehicle numbers will be essential.  Indeed, until the battery charging network for electric vehicles ceases to rely on electricity generated by burning fossil fuel or biomass, those vehicles will tend to accelarate climate change.

Abbey Road and Regent's Park 


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