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Air quality in parts of Cambridge worse than in Beijing this morning



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The air quality in parts of Cambridge was worse early this morning (Thursday) than in Beijing.

Sensors in Gonville Place gave it a reading of 144 on the air quality index at 7am this morning, compared to 107 in the Chinese capital. And the monitoring station by Orchard Park School to the north of the city, near the A14, placed it at 137 on the index.

Exhaust fumes are one of the factors leading to high particulate matter levels in the air
Exhaust fumes are one of the factors leading to high particulate matter levels in the air

These levels are considered unhealthy for sensitive groups, who are advised to wear a mask outdoors while such conditions last. It is recommended that windows are kept closed and outdoor exercise reduced in areas where air quality is this poor.

The air quality index (AQI) at Gonville Place had been in the range considered unhealthy for sensitive groups since 2am and the pattern was repeated on Wednesday, between midnight to 8am.

The index takes into account readings of key pollutants - PM2.5, PM10 and NO2.

At Gonville Place, the key contributor was PM2.5 - fine particulate matter that is 2.5 microns or less in diameter, or about 30 times smaller than the width of a human hair, which is tiny enough for these particles to penetrate deeply into our lungs.

Exhaust fumes, and wear on vehicle brakes and tyres, are among the many sources of PM2.5, along with construction, cooking and biomass burning, including domestic wood burning.

The particles were present at Gonville Place at 7am in a concentration of 53 micrograms per cubic metre (µg/m³).

The reading is a snapshot, and changes hour by hour as conditions alter over the course of the day - by 9am, it had declined to 18µg/m.

At Orchard Park, the reading was 50µg/m³ at 7am, declining to 29 by 9am.

Over the longer term, the World Health Organization suggests mortality is increased if there is an annual mean concentration above 10µg/m³, although the law in the UK currently requires the annual average not to exceed 25 µg/m³.

Regular exposure to high levels of PM2.5 increases the risk of lung and heart diseases, and leads to increased hospital admissions.

The government’s Committee on the Medical Effects of Air Pollution (COMEAP) estimates that exposure to PM2.5 contributes to 29,000 premature deaths in the UK every year.

The ratings on the Air Quality Index (51073528)
The ratings on the Air Quality Index (51073528)

The Greater Cambridge Partnership recently unveiled a plan for 10-minute bus services paid for by congestion or pollution charge, which could include an ultra low emissions or clean air zone.

Liberal Democrat city councillor Marcus Gehring told the Cambridge Independent this week that he wanted Cambridge to take action now.

He said: “We know that air quality, especially emissions and particulate matter, affect young people much more than the average population. So, a younger city also needs much stricter pollution measures than many other cities. And that’s why we should follow the example of Oxford city and institute a zero emission zone.

“On this occasion, Oxford has left Cambridge in the dust. You need the transport infrastructure, you need cycle parks, maybe car parks, but I think only a complete zero emissions zone will really improve the air quality quickly.

“Oxford announced it last summer and is now phasing it in this summer. The scientific knowledge on how to do it is all there. It’s just the relatively difficult governance structure that Cambridge city finds itself in that makes it slightly more complicated.”

Writing for the Cambridge Independent recently, the Labour leader of the city council, Cllr Lewis Herbert, agreed that action was needed, led by the Greater Cambridge Partnership and supported by the Combined Authority.

Cllr Lewis Herbert on East Road in Cambridge. Picture: Keith Heppell
Cllr Lewis Herbert on East Road in Cambridge. Picture: Keith Heppell

“We need cleaner air for residents along major traffic routes in and through Cambridge particularly near the hot spots. Dirty air is currently breathed in by pedestrians and cyclists young and old, many with health conditions. People travelling inhale it too. We all need cleaner air,” he said, and pointed to some work already being done, including the switch of taxis to electric or ultra-low emission vehicles, and the addition of more electric charging points by the authority. However, he acknowledged that a citywide strategy was needed.

Back at Gonville Place, PM10 particles were present at 7am in a concentration of 57.5 µg/m³, declining to 26.7µg/m³ by 9am.

These are particles of 10 microns or less in diameter, which can also come from exhaust fumes and wood-burning, along with sources such as dust from construction sites, landfill sites, agriculture and open land, and also include pollen and fragments of bacteria.

As these particles are larger than PM2.5, they are more likely to be deposited in larger airways of the upper region of the lung.

Air quality legislation demands that levels of PM10 do not exceed an annual average of 40 µg/m3, or a 24-hour average of 50 µg/m3 more than 35 times in a single year.

The final reading at Gonville Place showed nitrogen dioxide (NO2) in concentrations of 32.5 µg/m³, which is not particularly high. This highly reactive gas, which comes from vehicle emissions, power plants and off-road equipment, can irritate the airways and aggravate respiratory diseases such as asthma.

Contour plot of modelled Nitrogen Dioxide NO2 (annual mean concentrations) for October 2017. AQMA stands for Air Quality Management Area and refers to a legally determined area where legal objectives for a pollutant could potentially be breached or are being breached. Cambridge declared this area for annual mean NO2 in 2004. The attached plot (for October 2017) shows the most recent modelled concentrations of that pollutant. The units are micrograms per cubic metre. The objective level is micrograms per cubic metre and likely exceedances are shown as red through to dark red. Source: Lewis Herbert and Jo Dicks, Environmental Quality & Growth Manager, Cambridge City Council (01223 457892) (49577009)
Contour plot of modelled Nitrogen Dioxide NO2 (annual mean concentrations) for October 2017. AQMA stands for Air Quality Management Area and refers to a legally determined area where legal objectives for a pollutant could potentially be breached or are being breached. Cambridge declared this area for annual mean NO2 in 2004. The attached plot (for October 2017) shows the most recent modelled concentrations of that pollutant. The units are micrograms per cubic metre. The objective level is micrograms per cubic metre and likely exceedances are shown as red through to dark red. Source: Lewis Herbert and Jo Dicks, Environmental Quality & Growth Manager, Cambridge City Council (01223 457892) (49577009)

In the UK, the Air Quality Standards Regulations 2010 demand that the annual mean concentration of NO2 must not exceed 40 µg/m3 and the number of times the hourly mean limit goes above 200 µg/m3 in a single year must not exceed 18.

The IQAir site, which features an air quality map, forecasts improving conditions at Gonville Place in the coming days. It is due to be good for Friday to Tuesday, and moderate on Wednesday.

In a report on particulate matter in April, the government noted that urban background levels of PM2.5 and PM10 have reduced in the UK over the last couple of decades.

It notes: “Both PM and the precursor pollutants that can form it can travel large distances in the atmosphere. A small proportion of the concentrations of PM that people in the UK are exposed to come from naturally occurring sources such as pollen and sea spray (approximately 15 per cent).

“Another third is transported to the UK from other European countries. However, around half of UK concentrations of PM comes from anthropogenic sources in the UK such as domestic wood burning and tyre and brake wear from vehicles.”

Similarly, NO2 levels have come down since the turn of the century. However, there remains much to do to improve air quality.

In March, projections based on current levels showed the UK was due to miss most of its targets on reducing emissions between 2020 and 2030, specifically on PM2.5, ammonia, SOx and NOx.

A Defra spokesperson said: “Air pollution at a national level has reduced significantly since 2010 and emissions continue to improve year-on-year. However, we know there is much more to do, which is why we are delivering a £3.8 billion plan to clean up transport and tackle NO2 pollution, among other measures.”

Its Environment Bill is intended to help local authorities tackle air pollution, while its Clean Air Strategy promises action to tackle a range of pollutants.

Meanwhile, the Cambridgeshire and Peterborough Combined Authority has submitted a business case for funding to support a new Zero Emission Buses Regional Area (ZEBRA) scheme for the funding of £4.295million for new buses.

These would replace 10 per cent of the 350-strong fleet in operation on the urban and inter-urban bus networks across the Combined Authority’s area. This will require match funding from bus operators, the Combined Authority and the Greater Cambridge Partnership, with a combined value of more than £16.5million.

Read more

Lewis Hebert: We all need cleaner air, better buses and fewer cars

Buses proposed every 10 minutes in Cambridge – paid for by city congestion charge

Bid to government for £4.2m for zero emission buses for Greater Cambridge

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