London's low-emission zone ineffective in improving child lung health, study says

Low-emission zones -- areas with a daily charge for vehicles that don't meet emission requirements -- were introduced in 2008 and have led to small improvements in nitrogen dioxide and nitrogen oxide levels, found in diesel emissions, according to a study published Wednesday.

But no improvements were seen in levels of particulate matter -- PM10, less than 10 micrometers in diameter -- which can cause premature death and worsening of heart and lung diseases, according to the London Air Quality Network.

Despite a reduction in some pollutants, the study found no evidence of a decline in the number of children with reduced lung capacities or asthmatic symptoms since the implementation of the zone in London.

The authors stress that more ambitious control measures are needed to improve childhood respiratory health.

"Traffic pollution harms children's health, particularly development of lungs," said Chris Griffiths, professor of primary care at Queen Mary University of London, who co-led the research.

The impact of zoning

Low emission zones restrict or penalize the entry of polluting vehicles and are often the biggest part of emissions-reducing strategies, according to the study. London's current zone requires the most polluting diesel vehicles to meet European guidelines.

In 2008, London introduced the world's largest citywide low-emission zone, encompassing 8.5 million residents. There are 200 other such zones across Europe and several in Asian cities such as Singapore and Tokyo.

Griffiths' team is the first to look at the effects of large-scale traffic emission controls on air quality improvements and at their effects on children's health, he said.

Each year from 2009 through 2013, they measured the lung capacity of 400 different primary-school children between 8 and 9 years old in four East London boroughs. All four boroughs were within London's low emission zone and are heavily polluted, exceeding European Union limits on nitrogen dioxide at the start of the study.

Average exposure concentrations of nitrogen oxides and particulate pollution (PM10 and PM2.5) were measured annually at each child's home and school addresses.

"The introduction of lower-emission zones did improve air quality but had less of an effect than expected," Griffiths said.

They hoped to see children's lung capacity grow year by year, as the zoning should reduce pollution, but the researchers found the opposite: Their lung capacity was an estimated 5% smaller than it would otherwise be.

"Although changes of this magnitude are unlikely to cause problems in healthy children, we urgently need to know whether these lung deficits will impact lung function and health in later life," Griffiths said.

At the study's start, 99% of the children were living in areas that exceeded the European Union's limits for nitrogen oxide. By 2013, 34% were living in areas that exceeded EU limits -- but many went to schools that had higher levels of pollution, next to busy roads, according to the paper.

"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," Griffiths said.

Improving child health

A reduction in lung capacity can lead to stunted lungs, which is dangerous for two reasons, Griffiths said.

First, it increases the risk of asthma and worsens the condition in those who have it. In the long term, it can also be problematic for adults, as lung size is a good predictor for life expectancy, for reasons that are not exactly clear.

With age, the lungs start to decline, and if people enter adulthood with already declining lungs, this will lower their life expectancy, he explained.

"All of the children involved in this study lost some degree of lung function from breathing toxic air," said Dr. Penny Woods, chief executive of the British Lung Foundation, who was not involved in the research. "What this means is that we urgently need to go much further to protect people right now."

Griffiths highlighted that the study would have benefited from a comparison group of children living in an area of similar poor air quality and without any zoning regulations in place. Also, a larger number of children would have helped strengthen the findings.

About 93% of children globally breathe polluted air, according to the World Health Organization, and 4.2 million deaths every year are caused by outdoor air pollution.

Some of the world's most polluted cities include Peshawar, Pakistan; Varanasi, India; Cairo, Egypt's capital; and Al Jubail in Saudi Arabia.

Is ultra the next step?

In April, Central London will be equipped with a new version of the traffic control measure: an ultra-low-emission zone in which vehicles will have to meet stricter exhaust emission standards or drivers must pay a daily charge to travel within the zone.

The measure will encompass a larger area of London, to include more than 3.6 million additional residents, by 2021. It will also require that vehicles meet updated European guidelines on gas and diesel vehicles.

"It is predicted to have much bigger impacts on health," Griffiths said, and the research team is conducting a new study on the upgraded zone's effectiveness.

Ultimately, "a big step forward" to deal with traffic pollution would be to move away from cars that use diesel or gas and switch to electric vehicles, he said. Even in that case, there would be pollution created from tires and breaks the researcher added.

The British government also encourages such vehicles through grants of up to 4,500 pounds (US $5,800) to buy environmentally friendly cars.

"It is disappointing that the low-emission zone in London has not helped to improve children's lung capacity and [the study] shows that a piecemeal approach to reducing air pollution does not work," said Samantha Walker, director of research and policy at the charity Asthma UK.

"If children's lungs don't develop properly as a result of air pollution, it can increase their likelihood of developing asthma, leaving them coughing, wheezing and at risk of a life-threatening asthma attack."

Stefan Reis, head of atmospheric chemistry and effects at the Centre for Ecology & Hydrology, added that the study "highlights a key challenge for the implementation of policy interventions to improve air quality."

"Planned measures aiming to reduce population exposure in urban areas, and in particular vulnerable groups such as children or older adults, need to be adequately assessed prior to implementation."