Urban low-emissions zones have benefits that go beyond improved air quality
Air pollution is a truly global issue. Almost every person on the planet (99% of the population) breathes air that exceeds the limits set by the World Health Organization, with those living in higher levels of deprivation facing the most significant exposure.
As I’ve written about previously, in cities, air pollution tends to be a cocktail of sulfur dioxide (SO2), nitrogen oxides (NOx), carbon dioxide (CO2), particulate matter (PM2.5 and PM10), and secondary emissions. While the chemistry of these pollutants may differ, they all share a source – road traffic. Exposure to this complex mixture of pollutants has been linked to a wide range of health effects; everything from adverse birth outcomes and asthma, to cardiovascular disease, cancer and dementia.
Taking action on emissions
The threat posed by traffic-related air pollution has prompted many cities – more than 320 in Europe alone – to take action, particularly enacting low-emissions zones which restrict, fine or ban polluting vehicles entering a specified zone. While these zones are geared towards disincentivizing high-emissions vehicles, they are generally accompanied by incentives for those affected. Scrappage schemes for older cars, grants for purchasing electric vehicles, exemptions for those with disabilities, car-share programs from population centers, and reduced (or free) public transit are all common approaches used by city managers.
On 8th April 2019, an Ultra-Low Emissions Zone (ULEZ) was established in Central London. The stated goal was to reduce traffic-related air pollution in all parts of the city, in order to improve public health. Since that date, any vehicle that does not meet specified exhaust emission standards has to pay a daily fee to drive in the zone, and these restrictions apply 24-hours a day, 7 days a week.
The scheme proved so effective at reducing the number of highly-polluting vehicles on the roads that in August 2023, the ULEZ was expanded to cover all London boroughs – an area home to 9 million people. In the first six months of the expanded ULEZ, levels of nitrogen oxides and PM2.5 in the air were found to have dropped significantly. Carbon dioxide emissions in the ULEZ are reported to have dropped by 4% over a four year period.
Think of the children
A recent paper, led by researchers at Queen Mary University of London and the University of Cambridge, has shown that the benefits go beyond improved air quality. They found that in the ULEZ, more children than ever are walking, biking and scootering to school, and they suggest that the use of active transport may have a positive effect on their overall health.*
These findings are part of the Children’s Health in London and Luton (CHILL) study; a four-year research project into the impact of reducing traffic-related air pollution on children’s health. There’s a reason for this focus. Air pollution – particularly PM2.5 – has been described as “the leading environmental health risk for children in Europe and Central Asia.” According to UNICEF, one in five of all infant deaths in the region in 2021 were linked to air pollution, and therefore, preventable.
In the CHILL paper, the authors explain why kids are so vulnerable, “Children, due to their ongoing organ development, time spent outdoors, and higher breathing rates relative to body mass, are more vulnerable to the impacts of traffic-related air pollution than adults.” Their study cohort was large; more than 3,000 students from 84 primary schools across London and Luton (a town approximately 32 miles / 51 km north-west of London, not covered by the ULEZ).
In this particular paper, the researchers focused on how children aged 6–9 years traveled to and from their primary schools in London and Luton each day. They wanted to understand what impact the ULEZ had on the number of children using active or public transport modes compared to traveling by private vehicle or taxi (labelled as ‘inactive’ modes here).
To establish the baseline information, pre-ULEZ, participants (and their parents) were asked to complete surveys that collected basic information about their household and their travel habits. The questionnaires were repeated 12 months later.
They found that of the children who had been using active transport modes during the baseline phase, just 5% of those in London ended up switching to inactive transport modes during the study. In Luton, the proportion of children who switched from active to inactive was much higher, at 21%.
More notably, over the course of the study, they found that 42% of London children who had been traveling by inactive modes before the introduction of the ULEZ switched to active modes after its introduction, with those living further from their school more likely to make the switch. In the same period, 20% of Luton children (living outside of the ULEZ) moved from inactive to active modes.
Health impact
In addition to the questionnaires, trained healthcare practitioners carried out assessments at each school, collecting data on the children’s health. While the results of this part of the study were not reported in the paper, the study’s lead scientist Dr Jenna Panter told me by email that this is still to come. As part of their NIHR-funded research, she told me they intend to “assess the impacts of the…ULEZ on lung function, respiratory infections, cognitive function, total physical activity and body mass index as well as health care use and health costs”, using the same cohort in London and Luton.
Numerous other research teams have looked into the role that low-emissions zones can play in improving public health, albeit not exclusively focused on children. A large review paper published last year in The Lancet included examples of low-emission zones in Japan and the UK, amongst others. They concluded that these zones can – and do – lead to “observable health benefits”, particularly cardiovascular disease, such as heart disease and strokes. They also found that these zones experience fewer road traffic injuries. A German study focused on hospitals found that low-emissions zones lead to “small but statistically significant population health benefits”, mainly driven by reductions in circulatory and chronic lower respiratory diseases. An analysis of the planned expansion of the Paris low-emission zone (LEZ) concluded that most equitable distribution of health benefits would be felt if the zone reached its maximum extent and applied the most stringent vehicle standards. The authors say that this would prevent hundreds of deaths as well as thousands of cases of childhood asthma across all socioeconomic groups. And in a new paper, researchers at the University of Otago showed that decarbonization of transport in general could result in improved overall population health, leading to cost savings for the healthcare system. In addition, they say such a move “might contribute to health equity for Indigenous People in Aotearoa New Zealand.”
I could go on, but you get it. Fewer polluting cars on our roads means a cleaner environment and healthier humans. Surely, we all want that?
* For more on the childhood development aspects of the CHILL paper, read this from fellow Forbes contributor, Christine Ro
