Tree-lined streets 'cut asthma'
- A story from BBC news:
Tree-lined streets 'cut asthma'
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
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
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
"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.
Montreal QC Canada
- ----- Original Message ----
From: Christopher Miller <christophermiller@...>
> A story from BBC news:Despite my personal defense of trees on streets in cities, there are some limitations in this study:
> Tree-lined streets 'cut asthma'
"The design of this study means that it is not possible to conclude from the findings that planting trees would prevent childhood asthma for individuals living near them."
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