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Air pollution is known to contribute to premature death from respiratory and cardiovascular diseases. More and more evidence shows that breathing polluted air increases the risk of dementia. Children are also vulnerable: exposure to air pollution has been badociated with low birth weight babies, as well as poor cognitive and lung function during pregnancy. 39; childhood.
Cities such as London seek to reduce the social, economic and environmental costs of air pollution by improving the quality of urban air using low emission areas. In these areas, the most polluting vehicles are prohibited from access or drivers are penalized to encourage them to adopt cleaner technologies. The low-emission area of London was deployed in four stages from February 2008 to January 2012, affecting mainly heavy goods vehicles, such as delivery trucks and vans.
Our new study, which involves more than 2,000 children in four London neighborhoods, shows that these measures are beginning to improve air quality, but that they do not yet protect children from the harmful effects of environmental pollution. air. This is the most detailed badessment of the performance of a low emission area so far.
Young lungs
Our study focused on the Tower Hamlets and Hackney boroughs, but also included elementary schools in London and Greenwich. All of these areas have experienced high levels of air pollution due to traffic and have exceeded the annual EU limit for nitrogen dioxide (NO₂). Moreover, their population is very young and belongs to the most disadvantaged areas of the United Kingdom.
Between 2008-2009 and 2013-2014, we measured changes in air pollution concentrations in London while performing a detailed examination of lung function and respiratory symptoms in children in these areas.
Each year for five years, we measured lung function in separate groups of 400 children aged 8 to 9 years. We then examined these measures in parallel with the estimated exposure of children to air pollution, which took into account their place of residence and periods spent at home and at school.
Our findings confirmed that long-term exposure to urban air pollution is related to decreased lung volumes in children. The average exposure of all children during the five years of our study was 40.7 micrograms NO₂ per cubic meter of air, which was equivalent to a reduction in lung volume of about 5 %.
Changes of this magnitude would not have immediate clinical significance; children would not be aware of it and they would not affect their daily lives. But our results show that children's lungs do not develop as well as they could. This is important because failure to achieve optimal lung growth in adulthood often leads to poorer health later in life.
During the study, we also observed signs of reduced rhinitis (constant nasal discharge). But we found no reduction in the symptoms of asthma, nor the proportion of children with underdeveloped lungs.
Air pollution falls
The introduction of the low-emission area has done little to improve the respiratory health of children, but we have seen positive signs that it is beginning to reduce pollution. Using data from the London Air Quality Network – which monitors air pollution – we detected small reductions in NO₂ concentrations, although overall pollutant concentrations remained very high in the areas we examined.
The maximum reduction in NO₂ levels we detected was seven micrograms per cubic meter over the five years of our study, or about 1.4 micrograms per cubic meter each year. For context, the EU limit for NO₂ concentrations is 40 micrograms per cubic meter. Background levels of NO₂ in downtown London, where our study was located, decreased from 50 micrograms to 45 micrograms per cubic meter, over a five-year period. Roadside NO₂ concentrations were further reduced from 75 to 68 micrograms per cubic meter during our study.
By the end of our study in 2013-2014, large areas of central London were still not meeting EU air quality standards – and will not be before a some time at this rate of change.
We did not detect any significant reduction in the level of particles during our study. But that could be due to the fact that a much greater proportion of particle pollution comes from tire wear and brakes, rather than exhaust pipe emissions, as well as from Other sources, so that it would have been difficult to quantify the small changes due to the low-emission area.
The road ahead
Evidence from other sources shows that improving air quality can help to ensure the normal development of children's lungs. In California, a long-term study on children's health found that reducing pollution reduced the proportion of children with clinically small lungs – although it's relevant to note that NO₂ concentrations in their study in the mid-90s were already lower than those recorded in London today. .
Our results should encourage local and national governments to take more ambitious steps to improve air quality and, ultimately, public health. The ultra low emissions zone, which will be introduced in central London on April 8, 2019, seems to be a positive step in this direction.
The program, which will be extended to the limits defined by the north and south circular routes in October 2021, targets most vehicles in London – not just a small fraction of the fleet. The low emission zone seems to be the right treatment – now is the time to increase the dose.
Ian Mudway, Lecturer in Respiratory Toxicology, King's College London and Chris Griffiths, professor of primary care, Queen Mary University of London.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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