In the zone

Diesel – a costly lesson

The first attempt to lower air pollution in London was by accident. The congestion charge, which from 2003 applied to all vehicles entering central London during peak hours, was about business and pragmatics. Improved traffic flow would make London more attractive to outside investment, improve the speed of buses and cut down on journey times.

It was only later that its aims broadened to reducing pollution, when, in 2006, mayor Ken Livingstone said he would punish cars with high levels of CO₂ emissions with higher charges. “There is a growing sense of concern amongst Londoners about climate change caused by CO₂ emissions, which is the biggest single problem facing humanity, and tackling this threat requires decisive action,” he said.

The congestion charge penalised petrol-guzzling ‘Chelsea tractors’ with government policy specifically promoting diesel instead.

However, there were unforeseen consequences for air pollution. Matthew Holder, head of campaigns at the British Safety Council, explains: “In the 2000s, there was a push to get people to switch to diesel because petrol engines emit higher concentrations of carbon dioxide. As a greenhouse gas, the focus was to reduce this for the purpose of combating climate change. Unfortunately, diesel produces higher concentrations of nitrogen dioxide, which, while not a greenhouse gas, is harmful to human health.”

Indeed, the 2018 research paper Did the Congestion Charge Reduce Pollution? confirms what happened. Authors at Lancaster University found a ‘sharp increase’ in NO₂ (nitrogen dioxide) the toxic gas produced from diesel. They said this could partly be attributed to the rise in numbers of commuters choosing to go by bus and taxi – vehicles which all then ran on diesel – rather than car.

On the other hand, the charge did lead to ‘substantial reductions’ in the levels of three other main pollutants: carbon monoxide (CO), particulate matter (PM2.5) and nitrogen monoxide (NO) due to reduced traffic overall. They said the study sounded a ‘cautionary note’: “Reducing congestion and reducing the harms of air pollution may be related but are certainly not identical as our study shows.”

Low – a new goal

The Low Emission Zone (LEZ) was introduced in 2008, this time applying to a wider area covering Greater London and requiring vehicles to meet certain emissions standards (minimum Euro III PM emission standards) or pay daily charges if they did not. Third and fourth phases were introduced in January 2012 requiring larger vans and other specialist vehicles to meet the standards for PM; and heavy goods vehicles standards were tightened to Euro IV.

How did the second push fare? In November 2018, the Lancet published a study which looked at this question from two angles. First, the impact on London’s air quality, and second, the impact on children’s respiratory health.

Data was collected from London’s monitoring stations over five years between 2009–10 until 2013–14. At the same time, 2,164 children from 28 primary schools in the London boroughs of Tower Hamlets, Hackney, Greenwich and the City of London were given health assessments over the same time frame. Parents were given kits to test their children’s lung function and collect urine samples.

The findings were disappointing. NO₂ had reduced fractionally, by about 1 μg/m³ per year, but there was no change in PM10, the microscopic particles of pollution that can create respiratory and cardiovascular issues. At the same time, the doctors saw continued, reduced lung volumes in children associated with exposures to both PM10 and NO₂ over the period.

Why? Perhaps the LEZ was simply not causing air pollution to decrease at a fast enough rate to make a difference to health. In the 2016 study A Tale of Two Cities: is air pollution improving in Paris and London? Professor Gary Fuller, air pollution scientist at Kings College London, looked at trends in NO₂ and particulate matter (PM10, PM2.5) for the previous 10 years.

For NO₂, he found that London would only comply with the legal air quality limits set by the EU by up to 193 years (compared with 20 years maximum for Paris).

This was predominantly because of a ‘large variability’ in on-road performance for vehicle emissions, compared with the projections the mayor’s office had publicised, which were based on lab results. Fuller concluded that: “The responsibility [for the success of LEZ] must therefore rest with the vehicle manufacturers that have previously engineered differences between type-approval tests and real-world emissions.”

Senior air quality analyst at Kings College London, Andrew Grieve, further explains: “The reason why LEZ didn’t have such a big impact on emissions is partly because projection models use the vehicle manufacturer’s lab testing. We have now come to realise that ‘real-world’ emissions are higher than lab-tested emissions. This is why you have to measure actual emissions and not just rely on projections.”

Ultra Low Emission Zone

This brings us up to 2019. The ULEZ charge will apply to anyone driving diesel vehicles made before 2015 and petrol cars before 2006. It applies to central London and the plans are to expand it to the North and South Circular roads from 25 October 2021. Mayor of London, Sadiq Khan says this initiative will reduce some exhaust emissions by up to 45 per cent.

Khan also promises that expanding the ULEZ beyond central London will mean 100,000 Londoners no longer living in areas exceeding legal air quality limits by 2021, a reduction of nearly 80 per cent compared to without expansion.

Deputy mayor of environment & energy, Shirley Rodrigues, said it is a ‘pivotal moment’ for Londoners: “The health impact from our filthy air is shocking, especially on young children, and I look forward to seeing the results of the major new medical study looking at the impacts of ULEZ and cutting toxic emissions on children’s lung development. Our changes are already starting to improve the air across our city. In 2021, this will cut the number of schools in areas with illegal levels of air pollution by more than two thirds.”

There are aims to drastically lower the levels of the tiniest particulate matter, PM2.5 , which are said to cut nine months off the life of an average Londoner. The finding cited in a 2017 report submitted to the Greater London Authority, Potential for reducing PM2.5 concentrations in London recommended that in light of this, London should aim higher. Instead of the EU limits, London should meet the World Health Organization limits for the particle – concentration of 10μg/m³ or below – by 2030, well below half the current limit for the EU (25 μg/m³).

Andrew Grieve still has concerns: “Limit values and guidelines are important to focus minds on reducing concentrations but they’re not the end of the story. Even if we adopt the WHO PM2.5 limit, it’s not the case that below that everyone’s fine. We have to keep going beyond the limit values [because] as many studies show, there’s no safe lower limit for exposure to fine particles.”

It may be ambitious thinking, but ambition is precisely what we’re told is needed to reverse a host of environmental issues at the moment, whether air pollution or climate change. Car manufacturers, politicians and law makers must do what it takes to clean up the air. The ULEZ is only one part of a whole push to make the difference.

The British Safety Council would like to hear from employers interested in how they can reduce their outdoor workers' exposure to air pollution. Through the air quality app Canairy, we can potentially collaborate on case studies to build the evidence of what exposure-reduction interventions actually work. Get in touch to join the campaign or talk about your local issues with pollution via [email protected]