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Allergies and pollution

Trees also have their challenges, which requires consideration in tree selection and placement, including both health risks and other social risks.
Young man walking down the street wearing a medical mask. There is trees in the background.
© RMIT Europe and EIT Urban Mobility

Trees also have their challenges, which require consideration in tree selection and placement, including both health risks and other social risks.


Respiratory allergies represent a major public health issue in the modern world. Pollens are among the most significant causes of seasonal allergic rhinitis, with pollens of wind-pollinated trees representing an important cause (Vrinceanu et al. 2021).
The following principles can be used to identify trees that are important sources of allergies:
  • the pollen contributes to hay fever
  • the pollen is transported by wind
  • the pollen is produced in sufficiently large quantities
  • the pollen can travel for significant distances
  • the plants are widely distributed and abundant (Vrinceanu et al. 2021).
Plane trees are commonly used in urban planting because they provide shade and are tolerant of urban environments, however, they are also a source of allergens in urban areas.

Trees also produce pollution

Trees are a source of allergens in the urban environment.
However, trees emit volatile organic compounds (VOCs), which can contribute to air pollution by reacting in the atmosphere to form ozone in the presence of nitrogen oxides (NO and NO2, collectively NOx) (Cavanagh and Clemons 2006, 120).
Ozone is produced by photochemical oxidation of hydrocarbons and other volatile organic compounds (VOCs) in the presence of NOx. The significance of the contribution of VOCs produced by trees to ozone production has only been recently recognised, and the production of biogenic VOCs was suggested to be areas of the failure of ozone abatement strategies in the US (Chameides et al. 1988; Cardelino and Chameides 1990).
Biogenic VOCs can also contribute to air pollution through condensation in the atmosphere to produce particulates (Cavanagh and Clemons 2006, 125).

Your task

Are allergies commonly discussed as a problem in your city in relation to trees?
Do a quick online search and see if you find an article about allergies and trees in your city and post it in the comments below.
For example, searching “Melbourne trees allergies” brings this result on removing plane trees in Melbourne: Melbourne’s plane trees to be replaced by species resistant to climate change.
Commenting isn’t compulsory for completing the course, but it would be brilliant to hear your insights and for your fellow learners to benefit from your perspectives.

Academic references (Abstract only free to the public)

  • Cavanagh, J-A. E., and Clemons, J., (2006), ‘Do Urban Forests Enhance Air Quality?’, Australasian Journal of Environmental Management, 13, pp.120-130
  • Vrinceanu, D., Berghi, O.N., Cergan, R., Dumitru, M., Ciuluvica, R.C., Giurcaneanu, C., & Neagos, A. (2021). Urban allergy review: Allergic rhinitis and asthma with plane tree sensitization (Review). Experimental and Therapeutic Medicine, 21, 275. Urban allergy review: Allergic rhinitis and asthma with plane tree sensitization (Review)

What are the social perceptions and risks associated with trees? Let’s find out in the next step.

© RMIT Europe and EIT Urban Mobility
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