London Plan adopts stricter air pollution policy: new guidelines for particulate matter

High levels of air pollution in London and the risk this poses to its population is no secret. In 2015 it was estimated that nearly 9,500 people die early each year due to long term exposure to air pollution in the capital. Since then, in the five years since London Mayor Sadiq Khan entered office, the picture has dramatically improved with a 94% reduction in the number of Londoners living in areas exceeding legal limits for nitrogen dioxide (NO₂). However, there is still a long way to go with 99% of London still exceeding the World Health Organisation (WHO) recommended guideline.

Re-affirming Sadiq’s commitment to make London’s air quality the best of any major world city, the latest publication of the London Plan announced the adoption of the WHO guidelines for particulate matter. For developers operating in the capital, this means the target just got stricter. And the rest of the UK may not be far behind.

What is particulate matter?

Particulate matter is made up of tiny pieces (particles) of solids or liquids that pollute the air. These suspended particles can include dust, soot, smoke, metals, nitrates, sulphates, dust water and rubber.

The particulate matter with a mean diameter of less than 10 micrometers (μm), known as PM₁₀, can irritate your eyes, nose and throat. Some of this particulate matter is fine enough to be much more dangerous: this fine particulate matter, having a mean diameter of less than 2.5 μm and known as PM_2.5. These particles are so small that when inhaled can get deep into your lungs. PM_2.5 has been linked to a range of serious health conditions as well as an increased risk of mortality.

What is the new guidance in London?

In March, the London Plan 2021 was published introducing the World Health Organisation’s guidelines for particulate matter. Previously London, like the rest of England and Wales, adhered to concentration limit values set by the Air Quality Standards Regulations and the objectives of the UK Air Quality Strategy.

The limit values and objectives in England are 40 microgrammes per cubic metre air (μg.m^-3) for PM₁₀ and 25 μg.m^-3 for PM_2.5. The WHO’s guidelines – now included in the London Plan’s policy for developments – are 20 μg.m^-3 for PM₁₀ and 10 μg.m^-3 for PM_2.5; less than half of previous values and much more difficult to meet.

The issue

Particulate matter is spread right across the UK. But the important question is, how difficult will it be for developments in London to comply with these more stringent guidelines?

We can demonstrate this using data from Defra’s Automatic, Urban and Rural Network monitoring locations.

Map 1 shows us the monitoring locations that would comply with or exceed the new guidance for PM_10. Green dots show the locations where measured concentrations were below the limit of 20 μg.m^-3. Red dots show where PM₁₀ concentrations were above the 20 μg.m^-3 limit.

The measurements are shown for 2019, the last full pre-pandemic year, and the picture is quite positive – showing that most measurements came in below the WHO guideline.

But for PM_2.5 it’s quite a different picture. For the same year, map 2 shows the areas where PM_2.5 concentrations were above or below the WHO guideline of 10 μg.m^-3. As before, red dots show where the level was exceeded. The map shows widespread exceedances for PM_2.5 and, worryingly, in London the WHO guideline was consistently breached.

The challenge for developers

To achieve planning consent for a development in London, developers will need to make sure their proposed scheme complies with the new guidelines for particulate matter. For PM_2.5, particularly, where the guideline may be breached consistently across London, this creates a mitigation challenge. And in comparison to nitrogen dioxide (NO₂), a key traffic-related pollutant, developers can expect to see their options limited.

This is because the different type of pollutants ‘behave’ differently. Levels of NO₂ can vary substantially depending on the distance from the source of emissions, e.g. at the roadside vs. 100 m from the kerb. For developments this often means levels of NO₂ might exceed legal limits at one façade - close to a busy road – but be at an acceptable level at the rear of the same development. This crucial difference often allows for ventilation systems to draw air from the unpolluted façade and circulate to the rest of the building.

But particulate matter is distributed more evenly across the UK due to its wide range of sources. This means that if concentrations exceed the guideline at one façade of a development, it’s likely it will exceed at all façades. Ultimately meaning there will often be no ‘clean’ side of the building to draw air in from. This reduces the mitigation options and may frequently require the external air to be filtered as it is drawn into the building.

The solution

Understanding this issue at the start of a project can enable appropriate mitigation to be designed in. Based on the picture of current particulate matter levels in London, developers will most likely need to invest in a system to filter and clean external air to distribute throughout the building.

This will need to be identified and factored in for planning approval but will also save time and money if identified early. Retrofitting designs later down the line could prove costly.

Air purification systems will add both capital and operational expenditure which will scale depending on the size of the development. For example, a typical one bedroom flat in London is estimated at a capital outlay upwards of £2,000 with an annual operational cost of £600.

Consulting an air quality expert can identify the best and most cost-effective solutions for your site, as well as enabling informed decisions through the collection and modelling of accurate air quality measurements.

Our air quality and planning experts are here to help. To understand how the changes might impact you, fill in the form below and a member of our team will be in touch.

How does this affect developments outside of London?

Currently making its way through parliament, the Environment Bill places a duty on the Government to set a target for PM_2.5 by October 2022. To comply with this duty, MPs have been debating whether to introduce the World Health Organisation annual-mean guideline of 10 μg.m^-3 for PM_2.5 into law across the UK. This has been rejected so far but is raised for discussion each time the bill is debated. It seems that it will just be a matter of time before this guideline is introduced in the UK.

Developers can get prepared now by understanding the change in guidelines and how it could impact future development proposals. We’re happy to help with any questions, simply use the form below and a member of our team will be in touch.