Bangkok's Air Pollution: Causes And Concerns

Bangkok, Thailand's capital, has been suffering from hazardous air quality, with PM2.5 levels hitting 108 micrograms per cubic meter, far exceeding the World Health Organization's guidelines. The primary sources of Bangkok's air pollution are vehicular emissions, crop stubble burning, and industrial activities. In response to the crisis, the government has implemented various measures, including school closures, work-from-home directives, and free public transportation to reduce traffic and emissions. The situation has led to widespread health concerns, particularly for children, with UNICEF highlighting the devastating impact of toxic air on the region's youth.

Vehicular emissions

Bangkok has been struggling with hazardous air quality, with PM2.5 levels hitting 108 micrograms per cubic meter—nearly five times more than the threshold set by the World Health Organization for hazardous levels of air pollutants. The primary source of these harmful microparticles is vehicular emissions, which, along with smoke from crop stubble burning, have led to the Thai capital becoming the world's seventh-most polluted major city.

To address this issue, the Bangkok Metropolitan Authority has implemented several measures. These include restricting heavy vehicles and six-wheel trucks from entering certain areas, offering free public transport for a week, and urging people to work from home. By encouraging residents to use public transportation, the government aims to reduce the number of private vehicles on the roads and, consequently, decrease vehicular emissions.

The impact of these measures can be seen in the temporary improvement in air quality levels. For instance, during the period of free public transportation, the air quality index (AQI) reading dropped from 185 to 108, which is still considered unhealthy. However, experts argue that these actions are not enough, and systemic issues remain unaddressed.

Bangkok's struggle with air pollution is not unique, as other cities in Southeast Asia, such as Ho Chi Minh City and Phnom Penh, also face similar challenges. Transboundary smog, influenced by winds from China and India, further exacerbates the problem. To effectively tackle vehicular emissions and improve air quality in Bangkok, a combination of preventive strategies, consistent enforcement, and regional cooperation may be necessary.

Crop stubble burning

Bangkok, Thailand's capital, has been struggling with hazardous air quality, with the air quality index (AQI) hitting 185 in January 2025. This has forced the closure of more than 350 schools, affecting thousands of students. The Thai government has offered free public transport for a week to reduce traffic and limit the number of vehicles in the city, which are known to cause noxious exhaust fumes.

One of the leading sources of Bangkok's air pollution is farmers torching stubble to prepare land for the next crop. This "burning season" usually peaks between December and April. The practice of crop stubble burning is widespread in Thailand, with farmers burning sugarcane and rice stubble. This is done to reduce the amount of excess material, such as stalk tops, and to prepare the fields for the next crop. While this practice is common among farmers, it has severe consequences for air quality, with Bangkok and the northern city of Chiang Mai ranked among the most polluted cities in the world on some days in April.

The Thai government has been urged to ban crop stubble burning to improve air quality. Pornsil Patcharintanakul, president of the Thai Feed Mill Association (TFMA), has called for a ban on crop-burning, stating that it is a major source of dangerous PM2.5 particles, which are small enough to enter the bloodstream. The TFMA has given the government a realistic timeframe of three years to ban the practice.

To address the issue of crop stubble burning, the government could provide subsidies or harvesting machines to farmers. However, broader solutions are complex and challenging. Some potential ideas include moving away from monoculture production to agroecology practices, such as crop diversification and rotation, initiating land reform measures, and reducing the role of agriculture in the economy.

The government has taken some steps to curb pollution, such as offering free public transport and restricting heavy vehicles in the city. However, continuing to uphold the status quo will not be sufficient to reduce air pollution in Bangkok and other cities. It is clear that more comprehensive and effective measures are needed to tackle the issue of crop stubble burning and improve air quality in Bangkok.

Poor enforcement of crop burning rules

Bangkok's air pollution is caused in part by the burning of crop stubble in the colder, stagnant winter months. While the government has rules in place against burning crops, enforcement of these rules is poor, and punishments are not always handed out. This is a particular problem in the Ratchaburi province, where fields of rice, sugar cane, and corn are burnt as part of slash-and-burn farming practices. This method of clearing land is cheap and efficient for poor farmers, and they are encouraged to do so by big businesses driving up demand.

The crop-burning, combined with exhaust fumes from vehicles, has led to hazardous levels of air pollution in Bangkok. In January 2025, the city's PM2.5 levels hit 108 micrograms per cubic meter, which is nearly five times more than the threshold set by the World Health Organization for hazardous levels of air pollutants. This has resulted in the closure of schools, with children being particularly vulnerable to the health effects of air pollution. UNICEF has urged the government to strengthen its climate and environmental policies and enforce WHO-aligned air quality standards to protect children's health.

The Thai government has attempted to tackle the air pollution crisis by offering free public transport to reduce the number of private vehicles on the roads. They have also imposed work-from-home directives for civil servants. Prime Minister Paetongtarn Shinawatra has claimed that progress is being made, stating that the country has successfully reduced burned agricultural areas by 50% and that PM2.5 levels are down 30% compared to the previous year's peak.

Despite these efforts, Bangkok continues to rank as one of the most polluted cities in the world, and the problem is worsening. Experts say that government measures fall short, and more preventive action is needed to address the systemic issues contributing to air pollution. It is clear that poor enforcement of crop-burning rules is a significant factor in Bangkok's air pollution crisis, and stronger action is needed to protect the health and well-being of the city's residents, especially children.

Transboundary smog

In the case of Ontario, Canada, transboundary smog is a pressing concern, especially during the summer months. The Community Multi-Scale Air Quality model (CMAQ) developed by the U.S. Environmental Protection Agency, helps to characterise and predict the behaviour of smog-related pollutants like ozone and PM2.5. These pollutants can travel hundreds of kilometres due to winds, impacting areas far from the pollution source.

The influence of transboundary sources on Ontario's air quality varies across the province. Southwestern Ontario, near the U.S. border, and the shores of Lake Erie, Lake Huron, and Georgian Bay are particularly affected. In these regions, elevated ozone levels are predominantly attributed to transboundary sources, with the U.S. contributing up to 40%. Global background sources also play a significant role, especially on poor air quality days, contributing up to 80% of ozone concentrations.

Transboundary contributions to PM2.5 levels in Ontario are largely due to secondary PM2.5 formation. This occurs when precursor emissions, such as sulphur dioxide and nitrogen oxides, undergo complex reactions in the atmosphere. The impact of transboundary flows is more pronounced in rural areas with fewer local sources of direct emissions, where they can account for over 80% of PM2.5 concentrations.

Addressing transboundary smog requires a comprehensive understanding of the sources and dynamics of air pollutants. By utilising models like CMAQ and considering meteorological factors, regions can better predict and manage the impact of transboundary smog on their air quality. Collaborative efforts between nations are also crucial to mitigating this issue, as transboundary pollution recognises no borders and impacts the well-being of people across multiple regions.

Household air pollution

Bangkok, Thailand's bustling capital, is notorious for its poor air quality, with seasonal air pollution spiking during the dry season from February to April. While vehicle emissions, agricultural burning, and industrial activities significantly contribute to Bangkok's air pollution, household air pollution also plays a crucial role, especially in the impact on the health of children.

PM2.5 refers to microscopic particles or droplets that are 2.5 microns or less in width, which is approximately 30 times smaller than the width of a human hair. These particles can originate from various sources, including vehicle emissions, power plants, and residential solid fuel burning. Due to their minuscule size, PM2.5 particles can remain suspended in the air for extended periods and travel long distances. When inhaled, these particles can penetrate deep into the respiratory system, causing severe health issues, especially in children whose bodies and lungs are still developing.

The impact of household air pollution on children's health is profound. UNICEF's analysis highlights that air pollution is linked to nearly one in four deaths among children under five in the region. Prolonged exposure to polluted air can lead to respiratory problems, impair lung development, and increase the risk of developing chronic diseases later in life. Additionally, toxic air can compromise children's growth and cognitive development, underscoring the urgency of addressing household air pollution.

To mitigate household air pollution in Bangkok, UNICEF has advocated for implementing programmes that provide solutions such as chimney ventilation and cleaner heating systems. By improving ventilation and transitioning to cleaner energy sources for cooking and heating, households can significantly reduce indoor air pollution levels and protect the health and well-being of children.

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