Air pollution is a chronic problem in Bangkok and many parts of Thailand. Throughout January and February, the capital has faced a particulate matter (PM) 2.5 air pollution crisis, with several districts categorized as “red” (hazardous to health) because of the tiny toxic dust particles, putting residents at risk of severe health effects.
Breathing in unhealthy levels of PM2.5 pollution over time can lead to respiratory problems, cardiovascular diseases and other serious health issues.
According to the data from Bangkok Metropolitan Administration (BMA), there were 32,502 cases of city residents falling sick due to the effects of PM 2.5 between January 1 and 28.
The number of patients seeking treatment for pollution-related illnesses from hospitals and public health centers supervised by the BMA doubled from 500 to 700 to 1,000 to 1,400 persons per day and peaked at 1,900 persons per day when the city was blanketed with unsafe levels of the harmful dust particles.
They suffered from respiratory symptoms, difficulty breathing, scratchy throat, red eyes, eye irritation, skin rashes and nose bleeds.
As the city has been grappling with increasing air pollution, the idea of innovative gardens based on studies by a group of researchers offers a promising solution for better air quality in urban environments.
Filled with a mixture of trees and plants, these layered landscaped gardens not only increase the aesthetic quality of urban areas enhancing a sense of vitality, but also serve as natural barriers that help reduce people’s exposure to harmful pollutants as well as remove fine particulate matter and reduce overall air temperature.
Trees that are excellent at removing air pollution
Trees and plants provide shade, keep the environment cool, fresh and attractive.
They also have the remarkable ability of reducing air pollution and small-sized particles of organic chemicals, acids, metals and dust emitted from fossil-fuel burning vehicles and industries as well as construction sites.
“Trees can act as a sustainable air purifying filter. They have enzymes to break down pollutants and can absorb tiny airborne dust. They can help protect us from air pollution,” says Assoc.Prof. Chairat Treesubsuntorn, a lecturer at the School of Bioresources and Technology of King Mongkut’s University of Technology Thonburi and head of the university’s Remediation Lab.
He cited a collaborative research study he carried out with academics from Chiang Mai University and Srinakharinwirot University.
Funded by government agencies including the National Research Council of Thailand (NRCT) and the Thai Health Promotion Foundation, this experiment aims to test the ability of different tree and plant species to determine whether they can help mitigate dust pollution, how they clean the air and how they respond to stress.
“Trees are generally good at reducing air pollution and improving air quality. But we find some do it better than others,” the researcher says.
The study suggests that butterfly tree (ton chong ko), teak (ton sak), Brazilian rosewood (ton kae foy) and Burmese rosewood (ton pradu) are excellent at trapping pollutant particles.
Photo: evergreen banyan trees (ton sai korea
The evergreen banyan trees (ton sai korea), water jasmine (ton moke), orange jasmine (ton kaew), and fountain plants (ton pratadcheen) were found to be especially good at absorbing toxic gases and purifying the air.
Photo: water jasmine (ton moke)
Ferns, flame violet (ton prom kamayee), and peacock plants (ton kla waew mayura) also performed well in removing airborne particles and toxins.
Trees with leaves and shrubs that have rough, rugged, waxy and hairy surfaces are markedly more effective at trapping particulate matter than others, he notes.
Innovative gardens that help purify the air
Knowledge alone is not enough. The research team then put their findings into practice.
In 2023, they turned a space in front of the NRCT’s office on Phahonyothin Road into a landscaped lush green garden in layers, filled with diverse species of trees and plants that have natural air-filtering properties.
“In this experiment, we wanted to investigate whether a good mixture of species and landscaping design would produce more effective green space,” Chairat says.
He explains that the trees and plants are arranged in three layers in the garden, with tallest plants at the back, medium-sized plants in the middle and shorter plants in the front of the garden bed.
Perennial plants that include butterfly tree, teak and Burmese rosewood form the background.
The middle ground contains shrubs including banyan trees, water jasmine, and orange jasmine. The foreground, meanwhile, includes Boston fern, Iris Lace, and flame violet, all air-purifying plants.
Photo: Orange jasmine
The results showed that creation of the innovative garden mitigated fine particulate matter on average by 15%, while temperatures behind the garden could be reduced by as much as 2-4 degrees Celsius over the duration of the study.
The amount of particulate matter removed depends on several factors that include air pollution concentration, plant species, landscaping design and weather conditions such as wind speed and direction, Chairat notes, adding that wind direction plays a big role in urban landscaping design.
“We hope that our findings will be useful for the city planners to think more carefully what species should be planted to help clean the air,” he says.
The innovative garden pilot project has been extended to cover areas in front of the Ministry of Foreign Affairs, the Ministry of Higher Education, Science, Research and Innovation and spaces on Ratchadapisek Road.
The academic urges city residents to be aware of the air pollution problem as it’s a major environmental risk to health and to work closely with the BMA officials to help improve the air quality in urban environments.
“Clean air is everyone’s business. Everyone has a responsibility to protect our atmosphere and has a part to play to ensure healthy air in the city,” Chairat says.
Teamwork is key
Urban tree advocate Oraya Sutabutr, co-founder and board member of the Big Trees Project, strongly supports the idea of innovative gardens, saying urban trees can help fight air pollution in the city.
“Big trees are essential for a healthy city. They help cool our city, purify the air we breathe, improve our health and mood and so much more. With a bigger tree, you can expect cleaner air,” she says.
Air pollution is a complex problem facing Bangkok but she believes the issues that involve the existing situation can only be improved by multiple departments and organizations as well as the public collaborating across boundaries.
“The problem is too complex to be addressed by any one state department or agency alone. Collaboration is key to success. But getting government agencies, non-profits, private businesses, academics and city residents to work together is a big challenge,” Oraya says.
But one little thing that city residents can do to help clean up the air that can contribute to urban air pollution is limiting the use of personal vehicles, a major polluter.
In Bangkok, vehicles outnumber the population of the capital.
Data from the Office of Transport and Traffic Policy and Planning reveal that the capital had over 11 million registered vehicles in 2023, with nearly half (45.8%) of the vehicles being sedans, followed by motorcycles (35.9%) and vans and pick-up trucks (12.6%). Bangkok, meanwhile, was home to 5,471,588 people.
In addition, cars still dominate city residents’ commute.
A 2022 figure from Transportation and Traffic Information Center showed that 90.21% of Bangkok commuters used their own cars to move between home and work, making it the most popular mode of transportation, while 6.51% of them used buses and 1.32% travelled around the city on Skytrain.
“Take action, drive less to lessen the impact of cars. Opt for public transportation, biking or walking, which can help reduce air pollution. Or you can use electric cars that don’t depend on fossil fuels. It can help cut the amount of pollution we are contributing to the atmosphere,” she says.
