A study published in the European Respiratory Journal found that children exposed to tree and weed pollen in urban environments are at increased risk of respiratory health problems, including asthma. Green spaces in urban environments may reduce exposure to air pollution, allow children to be active, and provide good contact with diverse microorganisms, which in turn may aid in the development of a child's immune system, but they may also contribute to the development of childhood asthma. Thankfully, trees can help mitigate this effect to some extent, thanks to their canopy.
“We found that tree canopy provides some protection against the development of asthma in children. However, this protection is lost when exposure to weed pollen increases.”
Eric Lavigne (Lead author, Adjunct Professor, Department of Epidemiology and Public Health, Faculty of Medicine, University of Ottawa)
Using the Ontario Asthma Cohort Database, the researchers analyzed eight years of data to identify childhood asthma cases from birth to age six. Of the 214,000 mother-child pairs studied, just over 13% were diagnosed with childhood asthma. The researchers measured environmental exposure using the Normalized Difference Vegetation Index (NDVI) and tree canopy estimates within a 250-metre radius of the child's postal code at the time of birth.
The startling findings suggest that the development of green spaces in urban environments increases exposure to pollen and reduces the protection offered by tree canopies.
As more attention is focused on increasing vegetation in cities, Lavigne says the public should be made aware of the impacts that urban trees have, including the impact they have on children's respiratory health, particularly in terms of pollen, which contributes to an increased risk of asthma.
“This could have implications for urban planners and public health officials working to redesign urban centres,” added Lavigne, who is also a senior epidemiologist at Health Canada. “Along with decisions about when to plan weed pollen control programs and specific trees, it will be important to consider tree species that minimize airborne allergenic pollen.”
sauce:
Journal References:
Stanescu, C., et al. (2024). Early childhood pollen exposure and increased risk of childhood asthma: a prospective cohort study of Ontario children. European Respiratory Journal. doi.org/10.1183/13993003.01568-2023.
