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How bad is the air pollution in Greater Cambridge – and what is causing it?

Air pollution is considered “the largest environmental risk to the public health, contributing to cardiovascular disease, lung cancer and respiratory diseases”, according to a new report to Cambridge City Council.

In fact, the list of risks make for sobering reading.

Traffic congestion in Cambridge. Picture: Keith Heppell
Traffic congestion in Cambridge. Picture: Keith Heppell

The report goes on: “It is recognised as a contributing factor in the onset of heart disease and cancer. Air pollution increases the chances of hospital admissions, visits to emergency departments and respiratory and cardiovascular symptoms which interfere with everyday life, especially for people who are already vulnerable.

“Bad air quality affects everyone and it has a disproportionate impact on the young and old, the sick and the poor.”

And the report, which outlines the new 2024-29 Air Quality Strategy for Cambridge and South Cambridgeshire, stresses: “It is widely accepted that there is no safe level of air pollution.”

Cambridge City Council and South Cambridgeshire District Council have jointly drafted the five-year plan, which sets out areas where they can intervene to improve air quality, such as through spatial planning, infrastructure improvements to encourage the take-up of public transport, cycling and walking, and public engagement to help communities take action.

Research by the Committee on the Medical Effects of Air Pollutants (COMEAP) concluded in 2022 that “even low concentrations of pollutants are likely to be associated with adverse effects on health”.

So while figures for Greater Cambridge show emissions of key pollutants are below nationally set ‘objectives’, there is a drive to reduce the levels of pollution significantly - and work towards the much more stringent guidelines put forward by the World Health Organisation (WHO).

What are pollution levels like now?

Air pollution in Cambridge
Air pollution in Cambridge

A Cambridge City Council air quality report for 2023 shows annual mean concentrations of NO2 emissions at automatic monitoring stations were below the 40µg/m3 national ‘objective’ between 2018 and 2022, but above the 15 µg/m3 limit recommended by WHO in 2021.

They were recorded as between 17 and 24µg/m3 in 2022, although the pandemic was still having an impact then. The 2019 figures show levels of between 25 and 32µg/m3 at five monitoring sites in the city,

Additional roadside monitoring at dozens of other sites showed one instance where NO2 emissions exceeded 30µg/m3 - at 30.7 - in 2022.

The councils are aiming to reach an interim target of 20µg/m3 by 2029.

Annual mean PM10 emissions - a measurement of particles of less than 10 micrometres in diameter - at three monitoring stations were also below the annual mean objective of 40µg/m3 for 2018 to 2022 but well above the 10 µg/m3 limit put forward by WHO. In 2022, monitoring at Gonville Place showed an annual mean of 16µg/m3, while in Montague Road it was 17 and in Parker Street it was 21.

Again, the interim target is for emissions to be below 20µg/m3 by 2029.

Annual mean PM2.5 emissions were recorded at 15µg/m3 in Gonville Place and 7µg/m3 in Newmarket Road in 2022. The government wants PM2.5 emissions to be below 10µg/m3 by 2040 but the councils have set that as an interim target to hit by 2029 as they work towards WHO’s recommended limit of 5µg/m3.

South Cambridgeshire’s figures have similarly been below nationally-set objective levels in recent years.

However, there is clearly room to reduce them further - and air quality does vary significantly from day to day, and between Cambridge and South Cambridgeshire.

What are the main causes of air pollution?

Traffic congestion in Cambridge. Picture: Keith Heppell
Traffic congestion in Cambridge. Picture: Keith Heppell

The city council report notes: “Greater Cambridge is a highly populated, diverse area with a mix of both urban and rural areas. Within the urban and more populated areas road transport is the main source of pollution. There are considerable differences in emissions between different vehicles and fuels.

“In general, diesel exhaust contains up to 30 times more particulate matter than petrol, but all vehicles even electric generate additional particulate matter from friction of brakes and tyres and through re-suspension of dust from road surfaces.

“Construction sites and non-road mobile machinery (NRMM) can also be a significant source of localised pollutants with solid fuel burning (wood and coal) a significant source of particulate matter.

“Combustion from heating (both residential and commercial), farming activities and certain industrial processes also contribute to air pollution, but these tend to be more dilute contributing to background levels of air pollution.

“Within urban areas the accumulation of pollutants from both road transport and solid fuel burning is important as emissions are often co-located with exposed pedestrians, residential properties, hospitals, schools, shops and other places where people congregate.”

Traffic is the main contributor to NO2 emissions - and in Cambridge city centre, buses are described as the “main contributor”. On outer ring roads and outskirts of the city, cars are the main contributor, while on major roads such as the A14 and M11, it is HGVs.

Estimates suggest there is 1-25 tonnes per 1km2 of NO2 mainly from road transport, with minor roads and ‘cold starts’ - when engines are started from a low temperature - contributing the most in the city.

Over the last decade, the amount of particulate (PM10 and PM2.5) emissions from industry and energy generation has declined, amid a switch to using more gas, but this has been offset by an increase in domestic burning.

It is estimated that across Cambridge 1-4 tonnes per 1km2 of PM10 are from non-industrial combustion plant, such as domestic burning, with 0.2-1 tonnes per 1km2 from road transport - namely brakes and tyre wear.

Three-quarters of PM2.5, meanwhile, comes from non-industrial combustion plant - such domestic wood burning or other burning, with the from tyre and brake wear, although PM2.5 can also be produced as a secondary particle following chemical reactions with other pollutants.

In South Cambridgeshire, the main contributor to NO2 emissions is road transport, with major roads adding up to 25 tonnes per 1km2, notably including the M11, A14 and A11. Eight other significant sources of NO2 in the district are listed in the National Atmospheric Emissions Inventory, predominantly relating to manufacturing and waste sites, and also including Cambridge Crematorium, which South Cambridgeshire District Council regulates.

The main contributor of PM10 emissions in the district is non-industrial plant, causing up to 4 tonnes per 1km2. This includes domestic burning.

Road transport - from road abrasion, and brake and tyre wear, plus exhaust emissions - contributes a smaller amount (up to 2 tonnes per 1km2) and the picture is similar for PM2.5, with domestic wood and other solid fuel burning a key contributor, while non-exhaust emissions and exhaust emissions add up to 1 tonne per 1km2 each.

The report also notes: “Not all sources of air pollution impacting Greater Cambridge originate from within the districts; this means setting timelines for achieving WHO guideline levels may not be attainable in all cases at this time.”

What can be done about it?

An electric bus fleet has been launched for the region Picture: Keith Heppell
An electric bus fleet has been launched for the region Picture: Keith Heppell

The Greater Cambridge Air Quality Strategy sets out four key areas where local authorities can take action.

It notes that regulatory policies and development control play a key role, particularly as there are many large house-building projects on the horizon.

Getting the design of developments right is key.

The strategy report notes: “Spatial planning can provide for more sustainable transport links between the home, workplace, educational, retail and leisure facilities, and identify appropriate locations for potentially polluting industrial development.

“Emissions from development may be associated with both the construction phase and from transport or combustion processes providing heat and power during the operational phase when the development is occupied / in use.”

Infrastructure improvement is the second key area. Supporting public transport, improvements to cycling and walking, providing more electric vehicle charging points, consolidation of freight and last-mile deliveries and encouraging the use of ‘suitable green infrastructure’ are all proposed, along with consideration of the ‘road hierarchy’ - which could hint at closing some roads to motor vehicles.

The air pollution monitoring station at the corner of Gonville Place and Hills Road during the busiest part of the evening . Picture: Keith Heppell.
The air pollution monitoring station at the corner of Gonville Place and Hills Road during the busiest part of the evening . Picture: Keith Heppell.

Public engagement is the third area, with the councils keen to promote better awareness on air quality and provide accessible data, while supporting campaigns such as Clean Air Day and Clear Air Night.

Parents will be encouraged not let their engines idle while dropping off or collecting their children at school, while households will be encourage to reduce the use of solid fuel stoves, open fires and outdoor burning.

The councils also aim to work with businesses to reduce their impacts, and utilise smart technologies to enable faster, more efficient journeys.

Monitoring is the final area, with the need for a robust, up-to-date network of monitors to help the councils keep track of air quality and identify any hotspots as new developments spring up.

Last month, the city council’s environment and community scrutiny committee endorsed the strategy, which is also being discussed by South Cambridgeshire district councillors.

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