[enviro-vlc] USA: Tree-lined Streets Seem to Cut Asthma

[Vern Weitzel]

Subject: 	News: Tree-lined Streets Seem to Cut Asthma
Date: 	Fri, 2 May 2008 02:38:31 -0700
From: 	Yahoo Group <ashwani.vasishth at gmail.com>
Reply-To: 	envecolnews-owner at yahoogroups.com
To: 	Environmental Ecology News <envecolnews at yahoogroups.com>


http://news.bbc.co.uk/2/hi/health/7374078.stm

Thursday, 1 May 2008 01:18 UK

*Tree-lined streets 'cut asthma'

*Illustration Omitted:
   Trees in New York.  New York is currently planting more trees

Children who live in tree-lined streets have lower rates of asthma, a
New York-based study suggests.

Columbia University researchers found that asthma rates among children
aged four and five fell by 25% for every extra 343 trees per square
kilometre.

They believe more trees may aid air quality or simply encourage children
to play outside, although they say the true reason for the finding is
unclear.

The study appears in the Journal of Epidemiology and Community Health.

US rates of childhood asthma soared 50% between 1980 and 2000, with
particularly high rates in poor, urban communities.

In New York City, asthma is the leading cause of admission to hospital
among children under 15.

The researchers found the city had an average of 613 street trees per
square kilometre, and 9% of young children had asthma.

The link between numbers of trees and asthma cases held true even after
taking into account sources of pollution, levels of affluence and
population density, the researchers said.

However, once these factors were taken into account, the number of trees
in a street did not appear to have any impact on the number of children
whose asthma was so severe that they required hospital treatment.

Exposure theory

Some experts believe that children who are exposed to few microbes in
early life are at an increased risk of asthma because their immune
systems do not get the practice they need at fighting infection.

Therefore, if a tree-lined street encourages outside play, it might help
reduce the risk of asthma by maximising the odds that children will be
exposed to microbes.

However, trees are also a source of pollen, which may potentially
exacerbate asthma symptoms in vulnerable children.

Lead researcher Dr Gina Lovasi admitted the effect, if any, of trees was
far from clear.

She said: "There may be something else healthful about the areas that
had more trees.

"For example, trees could be more abundant in areas that are well
maintained in other ways."

Leanne Male, assistant director of research at the charity Asthma UK,
said: "Previous research looking at the influence of the environment on
levels of asthma has focused on negative aspects, such as pollution and
chemical exposure.

"This innovative report is the first to look specifically at the
potentially beneficial effects of trees in urban areas and raises some
interesting issues.

"However, there are a number of other factors that have not been
considered, for example whether the families involved have pets.

"Despite the need for further work, this is a positive first step into a
new area of research linking the environment and asthma."

New York City is planning to plant 1 million extra trees by 2017.

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