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Tree-lined streets 'reduce asthma risk'

01/05/2008

Children living in tree-lined streets may be less likely to develop asthma, a new study suggests today.

The research found that areas with a higher number of trees had lower rates of childhood asthma.

This was found to be the case even after sociodemographic characteristics, population density and proximity to pollution sources were taken into account.

US scientists studied asthma rates among four- and five-year-olds and related hospital admissions among children up to the age of 15 from 42 health service districts of New York City.

Data was then matched against city statistics on the number of trees in each area, sources of pollution, racial and ethnic make-up and population density.

On average the city had 613 street trees per square kilometre and nine per cent of young children had asthma.

For every increase in tree density (equivalent to 343 trees per square kilometre) the asthma rates in this age group fell by almost a quarter, according to the study in the Journal of Epidemiology and Community Health.

The researchers say the findings do not mean that the number of trees in any city is directly related to asthma rates.

But they added: "Trees may help prevent asthma, either by encouraging outdoor play or through an effect on local air quality."