How Trees Filter Our Air​

Created By RISC | 6 months ago

Last modified date : 6 months ago

The PM2.5 season is back. You may already be using air purifiers at home to filter out all the particles.​

But we shouldn’t overlook how trees can help us as living air filters.​

Trees help humans in many ways, as a source of oxygen, food, places to relax, and even cleaner air.​

Research shows that trees trap particles with their leaves, bark, and branches, reducing particles by 10-50% and the temperature by 0.4-3 °C. Airborne particles stick to the cuticle layer or outer epithelium of leaves, which is wrapped in epicuticular wax and covered in trichome hairs. Rain washes these particles away into the ground or drains. Photosynthesis also absorbs particles, carbon dioxide, and various toxic gases before releasing oxygen and water vapor to improve air quality.

Trees with dense canopies, lots of branches, smooth and thick leaf surfaces, and good pollution resistance are best at filtering particles. Foliage at multiple levels, such as ground cover, shrubs, and trees, will improve particle trapping efficiency.​

Here are some trees that suit different locations:​

For a shady area, plant Streblus asper, Murraya paniculata, and Ficus annulata. For an open area, plant Nyctanthes arbor-tristis, Delonix regia, Butea monosperma, Azadirachta indica, Peltophorum pterocarpum. For sidewalks, plant Casuarina equisetifolia, Schoutenia glomerata ssp., and Adenanthera pavonina. For decoration, plant Epipremnum aureum, Dracaena trifasciata, Chlorophytum comosum, or Ficus lyrata Warb.​

Trees can also inspire new ways to improve our indoor air.​

Story by Patcharin Pumjae, Intern form Department of Plant Biology, Faculty of Forestry, Kasetsart University and Thanawat Jinjaruk, Senior Researcher, Environment Division and Urban Environmental & Biodiversity Engineer, RISC