LONDON, June 24 (Xinhua) -- British primary school children are being exposed to 30 percent more pollution than adults while walking along busy roads due to their closer proximity to vehicle exhaust fumes, a study claimed.

The new research by Global Action Plan, a non-governmental organization, came based on experiments across four UK cities -- Manchester, Leeds, Glasgow and London.

The researchers used thermal imaging techniques which use CO2 as a tracer gas to illustrate how children's height makes them more vulnerable to exhaust fumes including nitrogen oxide (NOx), nitrogen dioxide (NO2) and diesel particulates.

The results also revealed that for children who are driven to school, the situation is far worse. They are exposed to double the pollution inside a vehicle than those walking on busy streets.

It showed that pollution levels from petrol and diesel vehicles were 2.5 times lower for children walking along quiet roads.

Air pollution is associated with reduced lung growth in childhood, as well as increased severity of asthma and pneumonia, according to research by Professor Jonathan Grigg from Queen Mary University in London.

"Children's lungs are especially vulnerable for those at primary school and younger, as they are still developing," Grigg said.

"My research has shown that exposure of young children to higher amounts of air pollution from traffic has a major impact on their lungs. Although parents can reduce this impact by walking on less polluted roads and taking public transport, the UK government must take further steps to reduce toxic emissions from all roads."

The study said that 4.5 million children are growing up in areas with unsafe levels of particulate pollution.

The statement was echoed in a report by the UN Children's Fund (UNICEF) in the UK, which said that 30 percent of British children live in "toxic air zones."

The UNICEF report found that almost a third of under-18s live in places with unsafe level of small particulate pollution, including 1.6 million under-fives and 270,000 babies in the country.

Among the worst affected are children in Birmingham, London, Manchester, Liverpool and Bristol, according to the UN report.

The health effects of exposure to small particulate pollution are estimated to cost the British National Health Service (NHS) and social care sector in excess of 40 million pounds (53 million U.S. dollars) each year.

Public Health England research shows that even the smallest improvement in air quality could reap massive rewards for children and the UK taxpayer.

During road closures for the London Marathon, traffic-free streets saw pollution levels drop by 89 percent, research by Kings College London revealed.

Amy Gibbs, who is from UNICEF UK, said: "We already know that air pollution is harmful, but these findings force us to face a shocking reality about the acute impact on children's health."

"Worryingly, one-third of our children could be filling their lungs with toxic air that puts them at risk of serious, long-term health conditions," Gibbs said.

Lack of funding for local authorities in the UK to tackle air pollution is a crucial issue, members of parliament from the four select committees said, adding that serious concerns remained over the British government's commitment to reducing the impact of air pollution.