Old-fashioned suburban streets lined with trees may provide some children with protection against asthma, researchers reported today.
It is not clear why trees make such a difference to childhood health.
One possibility is that they may improve air quality, soaking up carbon dioxide and monoxide and improving oxygen levels.
But, reporting in the Journal of Epidemiology and Community Health, researchers say another possibility is that tree lined streets are more likely to have places where children can play outside.
The findings come from a study in New York City, USA, where rates of asthma among four and five year olds were analysed along with hospital admission rates of children up to the age of 15.
Some nine per cent of young children had asthma with a city with 613 roadside trees for every square kilometre.
Although tree-lined suburbs are usually linked to relative affluence, the study found that tree densities had an impact of asthma, even when the effects of wealth were taken into account.
The effect of trees was mostly seen in improved health in young children.
Researcher Dr Gina Lovasi, of Columbia University, New York, writes: “Trees may help curb asthma rates by encouraging children to play outdoors more or by improving air quality.
“New York City is also planning to plant one million extra trees by 2017, which could provide the perfect opportunity to discover exactly what impact tree density has on asthma.”
Online First J Epidemiol Commun Health 2008; doi 10.1136/jech.2007.071894
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