London, Oct 8 (PTI) Exposure to air pollution on the way to school can have damaging effects on childrens cognitive development and reduce their working memory, a study has found.

The study, led by researchers from the Barcelona Institute for Global Health (ISGlobal) in Spain, assessed the impact of to fine particulate matter (PM2.5) and black carbon during the walking commute to and from school.

The findings of an earlier study had shown that 20 per cent of a childs daily dose of black carbon - a pollutant directly related to traffic - is inhaled during urban commutes.

"The results of earlier toxicological and experimental studies have shown that these short exposures to very high concentrations of pollutants can have a disproportionately high impact on health," said Mar Alvarez-Pedrerol, researcher at ISGlobal.

"The detrimental effects may be particularly marked in children because of their smaller lung capacity and higher respiratory rate," said Alvarez-Pedrerol, first author of the study published in the journal Environmental Pollution.

The study was carried out in Barcelona and enrolled over 1,200 children aged from seven to 10, from 39 schools, all of whom walked to school on a daily basis.

The childrens working memory and attention capacity was assessed several times during the 12-month study.

Their exposure to air pollution over the same period was calculated on the basis of estimated levels on the shortest walking route to their school.

Statistical analysis of the findings showed that exposure to PM2.5 and black carbon was associated with a reduction in the growth of working memory - an interquartile range increase in PM 2.5 and black carbon levels was associated with a decline of 4.6 per cent and 3.9 per cent, respectively, in expected annual growth of working memory.

No significant associations were found with exposure to NO2 and none of the pollutants studied were observed to have any effect on attention capacity.

In this study, boys were much more sensitive than girls to the effects of both PM2.5 and black carbon.

However, walking or cycling to school - which builds physical activity into the childs daily routine - has health benefits that outweigh any negative impact of air pollution, said Jordi Sunyer, head of ISGlobals Child Health Programme.

"The fact that children who walk to school may be more exposed to pollution does not mean that children who commute by car or on public transport are not also exposed to high levels," said Sunyer.

"The solution is the same for everyone: reduce the use of private vehicles for the school run and create less polluted and safer home-to-school routes," said Alvarez-Pedrerol. PTI MHN MHN