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Air Pollution Science Wildfires

Farming & Fires: Understanding Southeast Asia’s Seasonal Smoke Haze

Picture of Dr Gabriela Adler Katz
By Dr Gabriela Adler Katz on September, 9 2020

Each year, multiple countries across Southeast Asia and the Western Pacific suffer from extremely poor air quality for months on end. This poor air quality is such a regular seasonal occurrence (roughly between June to October) that the resulting air pollution is commonly referred to as ‘Southeast Asian Haze’. But what causes this air pollution and what health dangers does it present?

What is ‘Southeast Asian Haze’?

Southeast Asia’s seasonal ‘haze’ problem stems from specific low-cost ‘slash and burn’ farming methods used by particular countries in the region. These methods typically involve the burning of trees and plants by farmers to prepare fields for cultivation.

‘Slash and burn’ works by clearing land and creating a nutrient-rich layer of ash that helps to fertilize crops. The long-term disadvantage to this method from a farming sustainability perspective is that the land remains fertile for just a few years. When the land becomes infertile, farmers have no option but to abandon the land and move to a new plot, endlessly repeating the ‘slash and burn’ process.

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A Trans-national Smoke Pollution Problem 

Long-term sustainability issues aside, ‘slash and burn’ farming methods release huge amounts of harmful chemical and particulate air pollution into the atmosphere, with trans-national consequences for air quality.

Air pollution knows no regional or national borders, and the haze which results from these farming practices can measure hundreds of kilometers across, simultaneously blanketing multiple countries across the Southeast Asia region, Malaysia, Singapore, Thailand, Philippines, and more.

The Devastating Public Health Cost of Southeast Asia’s Seasonal Haze

Southeast Asian Haze is made up of high concentrations of PM2.5 which is easily suspended in wind currents for significant periods of time. This is a huge public health problem. As PM2.5 is small enough to be inhaled by humans, short-term exposure can worsen pre-existing asthma problems and other respiratory symptoms. (17)


There is still work to be done to confirm the specific health impact of long-term exposure to Southeast Asia’s seasonal haze, but studies have shown that long-term PM2.5 exposure is associated with increased mortality from certain diseases, such as those that are cardio-pulmonary related and more recently, likelihood of dying from from COVID-19. 

Studies have also found short-term exposure to Southeast Asian Haze to be linked to, but not limited to: 

  • Significant reductions (mean 18%) in pulmonary function among children (Hashim, et al. 1998)

  • 30% increase in outpatient attendance for haze-related conditions (Emmanuel, 2000) 

  • Associations between ischemic stroke occurrence and haze exposure. (Ho, et al. 2018) 

  • Increase in carcinogenic risk due to exposure to haze (Betha, et al. 2014) 

  • Increased outpatient department visits for headaches on warm and cool days (Chang, et al. 2015)

A more comprehensive review of the research into smoke haze exposure can be found here

The societal disruption of the seasonal haze experienced across this part of the world each year is profound. In 2019, nearly 2500 schools were ordered to close across Malaysia as a result of public health concerns resulting from toxic smoke haze in the air. 

BreezoMeter’s Integrated Smoke Model Powers  Real-time Responses to Air Quality in Southeast Asia

As with all wildfire-caused air quality reporting, charting the movement of Southeast Asia’s haze in real-time will present a challenge for a number of different air quality data providers. We explore the reasons for this in detail here


Seasonal Haze


To address these challenges, BreezoMeter has incorporated a sophisticated smoke model into its air quality reporting. This information can be leveraged by city planners, public authorities and businesses looking to research and respond to the reality of Southeast Asia’s haze in a hyper-local and real-time way.  

By better educating citizens of Southeast Asia of the health impacts of haze exposure, individuals can take proactive action to protect themselves and limit their personal exposure over time.

Further, personalized and accuracy-validated air quality information provides extremely valuable context for understanding individual health risk profiles -  vital information for both insurance and healthcare providers.


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