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Child lung health not improved by low emission zone drive

Low emission zone led to ‘modest’ improvement to air quality

Adrian O'Dowd

Thursday, 15 November 2018

The introduction of London’s low emission zone has improved air quality, but not to a level that will have benefited children’s lung health, claims an observational study* published today in The Lancet Public Health journal.

Air pollution is linked to 7 million premature deaths worldwide every year and in the UK, air pollution contributes to 40,000 deaths each year – nearly a quarter of them in London.

Across Europe, where more than half of new cars are fuelled by diesel, nitrogen oxide has become a major problem, and has been linked to asthma and impaired lung development in children.

Low emission zones (LEZ) are an increasingly common, but unevaluated, intervention designed to improve urban air quality and public health. They are now in place in 200 cities across Europe.

London introduced the world’s largest citywide low emission zone in stages during 2008 and 2012, requiring diesel vehicles entering Greater London to meet certain emission standards or pay daily charges.

A team of researchers set out to investigate the impact of London’s LEZ on air quality and children’s respiratory health.

They carried out a study including 2,164 primary school children (aged 8-9 years) attending primary schools between 2009–10 and 2013–14 in central London, following the introduction of London’s LEZ in February 2008.

Between 2009-10 and 2013-2014, children were given yearly winter health checks that included measuring the size and function of their lungs by blowing into a spirometer. Parents were also asked to complete a medical history questionnaire for their child, including questions on respiratory and allergic symptoms.

Annual average exposure concentrations of nitrogen oxides and particulate pollution (PM 10 and PM 2.5) were measured at the home and school addresses of each child over the five-year study.

The researchers also modelled pollution exposures for the three hours of 6am to 9am, 24 hours, and seven days before each child’s annual health check. This allowed them to look at the effects of both short-term and annual average exposures simultaneously.

Results showed that introduction of the LEZ had little impact in reducing levels of ultrafine particles (PM2.5) or course particulate matter (PM10) over the study period.

In contrast, levels of nitrogen dioxide at both the roadside and monitoring sites within and surrounding the study area fell by around 1 µg/m³ per year. Additionally, the proportion of children exposed to the EU annual nitrogen oxides limit fell from 99% in 2009 to 34% in 2013.

Nevertheless, average exposure levels of nitrogen dioxide over the five-year study remained high (median 40.7 µg/m³) and the researchers estimated that children’s lung capacities were reduced by around 5%.

Lead author Dr Ian Mudway of King’s College London said: “Policies such as the Low Emission Zone’s …  effectiveness needs careful and objective evaluation, not only in terms of whether they improve air quality, but more importantly, whether they deliver better health.”

Fellow author, Professor Chris Griffiths from Queen Mary University of London, said: “Until longer-term impacts are known, doctors should consider advising parents of children with clinically significant lung disease to avoid living in highly polluted areas, or to adopt personal mitigation measures to limit their exposure.”

The authors acknowledged that the study was observational, so no firm conclusions could be drawn about cause and effect.

*Mudway IS, Dundas I, Wood HE, et al. Impact of London’s low emission zone on air quality and children’s respiratory health: a sequential annual cross-sectional study. The Lancet Public Health, 14 November 2018. DOI:10.1016/S2468-2667(18)30202-0

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