The street trees & the verge gardens along busy New Canterbury Road would be working to prevent a percentage of the particulate matter & other pollutants from getting to the houses.

The street trees & the verge gardens along busy New Canterbury Road would be working to prevent a good percentage of the particulate matter & other pollutants from getting into the houses.  This is much better than no street trees or verge gardens.

A month or so ago I watched a segment on the television program ‘Trust me I am a Doctor’ about how an experiment with birch trees placed along a high traffic street impacted on air quality. See –http://bbc.in/1fjuxnm

The results were surprising, particularly because these were only small trees in pots. The experiment, developed by Professor Barbara Mahar from the University of Lancaster England consisted of twenty-four young Silver birch trees in pots lined up along the footpath beside four terrace houses. The trees were left in place for two weeks. The adjoining four other terraces were also included in the experiment.

Prior to installing the trees, the computer & television screens were cleaned in all terraces. They were then left on stand-by as these items produce static electricity & would continue to collect airborne dust & particulate matter.

At the end of the fortnight, all the computer & television screens were cleaned again. The air pollution collected on the screens was found to 50-60% lower in the four terraces that had the birch trees between them & the road, showing how vital street trees are for collecting particulate matter, dust & other pollutants from passing traffic.

Whether this percentage of protection happens with all street trees is not known, but the birch trees were chosen specifically because their leaves have hairs & ridges, which collect small particles. It may be that birch trees are found to be superior trees at collecting air pollution.

Every tree collects particulate matter & other air pollutants on their leaves, though it may be that some are better at collecting than others.   According to the article, trees with a denser canopy are not as effective at trapping air pollution as are the sparse canopy Silver birch, which allows for free airflow.  Denser canopy trees tend to collect pollution at ground level, where people are.

Rain cleans the leaves allowing the process to start again. Deciduous trees would only provide this benefit while they have leaves.

Vehicle exhaust releases very fine particles of particulate matter (PM), which is breathed into our lungs. From there it enters our cardiovascular system.   A recent government report [English] suggested that as many as 29,000 people a year die because of breathing in too much PM.”

The article lists three ways to limit exposure of particulate matter when outside –

  1. School drop off zones have high levels of particulate matter because of all the idling cars.   “So a quick drop-off, & fewer cars at the school gates is important.”
  2. To reduce your intake on particulate matter when driving, especially when stuck in heavy traffic, keep the windows & vents closed.  Also keep some space between you & the car ahead.
  3. Cyclists are advised to avoid routes with heavy traffic. Pedestrians are advised to walk as far away from the traffic as possible & also avoid walking along streets with heavy traffic. See – http://bbc.in/1tSRh1m

A 2013 study by the Laboratory of Aviation & the Environment at Massachusetts Institute of Technology found that premature death caused by air pollutants was the highest from road transportation – that is vehicle exhaust.   http://bit.ly/1k0tbtH

The humble street tree continues to demonstrate its worth.  They provide the community with many benefits, including better respiratory & heart health.   It is already known that residents in suburbs with fewer trees have poorer health, so increasing the canopy must be a priority.

I can instantly appreciate cleaner air in streets like Victoria Street in Dulwich Hill.  The air smells different.

I can instantly appreciate cleaner air in streets like Victoria Street in Dulwich Hill that have many big street trees.  The air smells different – better.

 

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