Web Desk(November 30, 2017): Urban air pollution can trigger asthma. But lots of trees in cities might lower the odds of a flare-up, a new study finds.
“We wanted to clarify how urban vegetation may be related to respiratory health,” said study leader Ian Alcock.
“We know that trees remove the air pollutants which can bring on asthma attacks, but in some situations they can also cause localized buildups of particulates by preventing their dispersion by wind. And vegetation can also produce allergenic pollen which exacerbates asthma,” Alcock added.
Trees did not have the same beneficial effect in relatively unpolluted areas, according to the study. The findings suggest tree planting could help reduce the harms of air pollution and guide planning and public health policy, the researchers concluded.
“We found that on balance, urban vegetation appears to do significantly more good than harm,” Alcock said. But effects were not equal everywhere.
“Green space and gardens were associated with reductions in asthma hospitalization at lower pollutant levels, but not in the most polluted urban areas. With trees it was the other way round”. he remarked.
Perhaps, he theorized, grass pollens become more allergenic when combined with air pollutants so that the benefits of green space diminish as pollution increases.
“In contrast, trees can effectively remove pollutants from the air, and this may explain why they appear to be most beneficial where concentrations are high,” Alcock said.
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