King's College London

The research, published in the journal Lancet Public Health, shows that whilst traffic pollution control measures have improved air quality in London, they still need significant strengthening to protect children’s health.

Air pollution is a leading cause of global mortality, with the World Health Organization estimating over four million deaths annually caused by outdoor air pollution. Children are especially vulnerable and at risk of lifelong breathing disorders, asthma attacks, chest infections and earlier death.

Low Emission Zones (LEZ) restrict or penalise vehicle entry into urban areas to encourage the uptake of lower emission technologies. London introduced the world’s largest city-wide LEZ in 2008, roughly contiguous with the M25 orbital motorway and encompassing around 8.5 million residents. But up until now, there has been little evidence on whether LEZs improve air quality or public health.

2,164 children aged 8-9 were enrolled into the study from 28 primary schools in the London boroughs of Tower Hamlets, Hackney, Greenwich and the City of London (all areas which fail to meet current EU nitrogen dioxide limits). The research team monitored children’s health and exposure to air pollutants over five years, covering the period when the LEZ was introduced, and found:

• Children exposed to air pollution showed significantly smaller lung volume (a loss of approximately 5 per cent in lung capacity). This was linked to annual exposures of nitrogen dioxide (NO₂) and other nitrogen oxides (NOx), both of which are in diesel emissions, and particulate matter (PM₁₀).
• Following the implementation of London’s LEZ, there were small improvements in NO₂ and NOx levels, but no improvements in PM₁₀
• Despite these improvements in air quality, there was no evidence of a reduction in the proportion of children with small lungs or asthma symptoms over this period.
• The percentage of children living at addresses exceeding the EU limit for NO₂ fell following the LEZ introduction, from 99 per cent in 2009 to 34 per cent in 2013, but they were exposed to higher levels when at school, many of which were next to busy roads.
• Significant areas of inner and outer London still remain above the EU NO₂

The researchers warn that, at the current rate of change of pollution levels, full compliance with EU limits for NO₂ for London remains distant, unless there is significant tightening of current emission controls.

In the meantime, they say clinicians should consider advising parents of children with significant lung disease to avoid living in high pollution areas, or to limit their exposures.

Dr Ian Mudway said: “There is an urgent need to improve our air quality, especially within our congested cities. Policies such as the Low Emission Zone strive to do this, but their effectiveness needs careful and objective evaluation, not only in terms of whether they improve air quality, but more importantly, whether they deliver better health. As the evidence base grows demonstrating that air pollution impacts on the health of children born and growing up in our cities, so the justification for decisive action increases.”

Professor Frank Kelly said: “These new findings linking air pollution and children’s lung growth provide further support for the introduction of the ultra Low Emission Zone in London early next year.”

Professor Chris Griffiths from Queen Mary University of London said: “Despite air quality improvements in London, this study shows that diesel-dominated air pollution in cities is damaging lung development in children, putting them at risk of lung disease in adult life and early death.

“We are raising a generation of children reaching adulthood with stunted lung capacity. This reflects a car industry that has deceived the consumer and central government which continues to fail to act decisively to ensure towns and cities cut traffic.”

The study is a collaboration across the MRC Asthma UK Centre in Allergic Mechanisms of Asthma and the Asthma UK Centre for Applied Research, and was funded by NHS Hackney, the NIHR Biomedical Research Centre at Guy's and St Thomas' NHS Foundation Trust and King's College London with donations from Him Lee and the Felicity Wilde Charitable Trust.