LONDON, May 27 (Xinhua) -- Science tests offered surprise results: air inside London classrooms is more polluted than outside, meaning that children in schools are being exposed to higher levels of damaging air pollution inside the classroom than outside.
This puts them at risk of lifelong health problems, a new research has revealed.
Scientists from the University of Cambridge and King's College London studied five primary schools and one nursery in the British capital as part of research into levels of air pollution indoors.
Primary schools and nurseries in London contain levels of fine air particles that are "consistently higher than outdoors" and breach World Health Organization (WHO) guidelines, according to the study, which was commissioned by London Mayor Sadiq Khan.
Pollution is thought to be worse inside than out due to air being less able to circulate and getting trapped.
The research showed that outdoor air pollution from diesel vehicles and other sources -- both of nitrogen dioxide and particulate pollution -- is affecting the lives of children inside schools.
Fine air particles, which weigh as little as 0.0025mg, are given out in vehicle exhaust fumes and, when breathed in, become deposited in the lungs where they enter the circulation.
Children are more vulnerable to pollution due to their less developed lungs and breathing in more air per kilogram of body weight.
The researchers wrote in the study, saying: "The exposure of children's developing lungs to air pollution can result in reduced lung function that persists through to adulthood, increasing susceptibility to respiratory and cardiovascular diseases."
"Children living or attending schools near high traffic density roads were exposed to higher levels of motor vehicle exhaust gases, and had higher incidence and prevalence of childhood asthma and wheeze," it said.
For nitrogen dioxide, which is strongly related to asthma attacks and is released from vehicle exhaust fumes, outdoor sources account for 84 percent of the variation between classrooms.
Air pollution levels in classrooms depend on factors such as building design and maintenance levels.
The schools studied were a modern suburban nursery and a primary school away from high traffic streets, a Victorian-built primary next to a busy road, two schools away from high traffic areas and a suburban modern school building close to a major road.
The findings came as the London mayor published his first audit of air pollution at 50 of the capital's schools and a series of measures to counter the impact of poor air quality.
Khan, who has launched a million-U.S. dollar fund to protect pupils from toxic air, said: "Air pollution is a national-health crisis that is putting the health of children at risk."
"As mayor, I've moved fast in London to implement the most ambitious plans to tackle air pollution of any major city in the world," he said.
"This includes cleaning up our bus and taxi fleets, bringing forward the introduction of the world's first ultra-low emission zone and introducing the toxicity charge -- T-Charge -- for the oldest polluting vehicles in central London."
"But I can't do this alone," he said. "The government must step up and act with more urgency if we are going to tackle London's filthy air once and for all."
The British Lung Foundation welcomed the mayor's fund for the most polluted schools but said that it was up to the government to take action.