Singapore Sustains Moderate Air Quality Amid Persistent Regional Haze Threat; Authorities Maintain Vigilance and Public Advisories.

Singapore’s air quality remained firmly within the moderate range on Sunday, September 6, marking a second consecutive day of improved conditions following a brief but significant period of unhealthy air pollution. This development offers a degree of respite for residents, yet the National Environment Agency (NEA) continues to issue daily haze advisories, emphasizing the inherent volatility of the situation due to ongoing regional fire activity and prevailing weather patterns.

As of 7pm on Sunday, the 24-hour Pollutant Standards Index (PSI) readings across Singapore registered between 72 and 87. This falls comfortably within the "moderate" band, defined as PSI readings from 51 to 100. The improvement came after a challenging period where, just a day earlier, on Saturday, September 5, air quality had also improved to moderate levels after three distinct regions – central, eastern, and western Singapore – experienced 24-hour PSI readings that had climbed into the "unhealthy" range.

The shift into the unhealthy band, specifically for the central region, occurred at 7am on Friday, September 4, when its 24-hour PSI exceeded 100, reaching 101. This marked a critical juncture, as it was the first instance of the PSI breaching the 100-mark since October 8, 2023. This significant event prompted the NEA to reactivate its comprehensive haze advisory system, commencing the issuance of daily updates that include a 24-hour PSI forecast. These advisories are crucial tools, designed to equip the public with the necessary information to plan their daily activities and events, particularly for vulnerable populations. Following the central region’s initial spike, the eastern and western parts of the island also saw their 24-hour PSI readings cross into the unhealthy threshold, underscoring the widespread nature of the haze impact.

In its daily haze situation update, issued at 6pm on Sunday, the NEA reported generally fair and windy conditions prevailing over Singapore throughout the day. While these local meteorological factors can help disperse pollutants, the underlying cause of the haze remains a persistent regional challenge. The agency highlighted the continued presence of moderate to dense smoke plumes originating from agricultural and forest fires in southern and central Sumatra, as well as West Kalimantan. These areas are notorious hotspots for land and forest fires, particularly during dry seasons, which are often exacerbated by climate phenomena like El Niño. The plumes, rich in particulate matter, are then transported across the strait by prevailing winds, primarily blowing from the southeast or south.

The ongoing dry conditions across the region play a critical role in exacerbating these fires. The NEA noted that while some showers are forecast over Kalimantan in the coming days, Singapore and its immediate surrounding region are expected to continue experiencing dry weather. This forecast carries significant implications: should the fires in the source regions persist or intensify, the risk of haze re-affecting Singapore remains high due to the consistent wind direction. Consequently, the NEA’s 24-hour PSI forecast for Singapore, spanning the 24 hours from 6pm on Sunday, projected readings in the high-moderate to low-unhealthy range. This cautious outlook serves as a stark reminder that while conditions may have temporarily improved, the threat of recurring haze remains tangible and requires sustained public vigilance.

Understanding Singapore’s Air Quality Indicators

Singapore employs a robust system for monitoring and communicating air quality, primarily through the 24-hour PSI and the one-hour PM2.5 reading. The 24-hour PSI is the primary indicator for daily air quality and forms the bedrock of the NEA’s health advisories. It is a comprehensive index calculated based on the concentrations of six key air pollutants: fine particulate matter (PM2.5), coarse particulate matter (PM10), ozone (O3), sulphur dioxide (SO2), nitrogen dioxide (NO2), and carbon monoxide (CO). By aggregating these pollutants, the PSI provides a holistic view of the overall air quality over a 24-hour period, offering a reliable basis for public health recommendations.

In contrast, the one-hour PM2.5 reading provides a more immediate snapshot of air quality. PM2.5, or fine particulate matter, refers to airborne particles with a diameter of 2.5 micrometres or less. These microscopic particles are particularly dangerous because their small size allows them to penetrate deep into the lungs and even enter the bloodstream, posing significant health risks. During haze episodes, PM2.5 is typically the dominant pollutant, making its hourly measurement a critical real-time indicator of the severity of smoke plumes. While the 24-hour PSI represents an average over a full day, offering guidance for sustained activities, the one-hour PM2.5 reflects the air quality at a single point in time, allowing individuals to make quick decisions about immediate outdoor exposure.

The PSI scale is categorized into several bands, each with specific health implications:

• 0-50 (Good): Air quality is satisfactory, and air pollution poses little or no risk.
• 51-100 (Moderate): Air quality is acceptable; however, for some pollutants, there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.
• 101-200 (Unhealthy): Members of sensitive groups may experience health effects. The general public is less likely to be affected.
• 201-300 (Very Unhealthy): Health warnings of emergency conditions. The entire population is more likely to be affected.
• Above 300 (Hazardous): Health alerts of emergency conditions. The entire population is likely to be affected.

The Perennial Haze Problem: A Regional Phenomenon

The haze affecting Singapore is a complex, transboundary environmental issue rooted in the practice of slash-and-burn agriculture and peatland fires in neighbouring Sumatra and Kalimantan, parts of Indonesia and Malaysia. This method, often employed for land clearing for palm oil plantations, pulp and paper industries, and other agricultural purposes, becomes particularly problematic during dry seasons. The region experiences distinct dry and wet seasons, and when prolonged dry spells, often exacerbated by climatic phenomena such as the El Niño Southern Oscillation (ENSO), occur, fires can quickly spread out of control, especially on highly combustible peatlands. Peat fires are notoriously difficult to extinguish, smouldering underground for weeks or even months and releasing massive amounts of smoke and greenhouse gases.

Historically, Singapore has grappled with severe haze episodes, with some of the most memorable occurring in 1997, 2013, 2015, and 2019. The 1997 haze crisis was particularly catastrophic, impacting air quality across Southeast Asia for months and causing an estimated US$9 billion in economic losses. The 2013 haze saw Singapore’s 3-hour PSI hit a record high of 401, entering the "hazardous" range, while the 2015 episode, amplified by a strong El Niño, was one of the longest and most intense in recent history. Each recurrence serves as a stark reminder of the vulnerability of urban centers like Singapore to environmental degradation in neighbouring territories.

Health and Economic Impacts

The implications of prolonged exposure to haze are far-reaching, encompassing significant health risks and substantial economic repercussions. On the health front, the fine particulate matter (PM2.5) is the primary concern. Inhalation of these particles can lead to a range of acute and chronic health issues. Short-term effects include respiratory symptoms such as coughing, sneezing, throat irritation, and shortness of breath; eye irritation; and skin allergies. Individuals with pre-existing conditions like asthma, chronic obstructive pulmonary disease (COPD), heart disease, and diabetes are particularly vulnerable, experiencing exacerbated symptoms that often necessitate medical attention or hospitalization. Children and the elderly are also at higher risk due to their developing or compromised respiratory and immune systems. Long-term exposure to high levels of PM2.5 has been linked to an increased risk of chronic respiratory diseases, cardiovascular problems, lung cancer, and even premature mortality.

Economically, haze can disrupt various sectors. Tourism, a significant contributor to Singapore’s GDP, often suffers as potential visitors reconsider travel plans to affected regions. Aviation can be impacted by reduced visibility, leading to flight delays or cancellations. Outdoor events, construction work, and other industries reliant on outdoor activities face cancellations or operational slowdowns, resulting in productivity losses. Healthcare systems bear an increased burden from haze-related illnesses, requiring more resources for treatment and emergency services. Furthermore, the sale of protective equipment like N95 masks and air purifiers, while necessary, represents an additional cost burden on households.

Singapore’s Proactive Haze Management Strategy

In response to the recurring threat of transboundary haze, Singapore has developed a comprehensive multi-pronged strategy. At the core of this strategy is the NEA, which plays a pivotal role in monitoring, forecasting, and disseminating information. The agency utilizes a network of sophisticated air quality monitoring stations across the island, providing real-time data on pollutant concentrations. This ground-level data is complemented by satellite imagery and meteorological forecasts, allowing the NEA to track fire hotspots in the region and predict the movement of smoke plumes.

When PSI levels begin to rise, particularly into the unhealthy range, the NEA activates its Haze Management Plan. This plan includes daily public advisories, detailing the current air quality, the 24-hour PSI forecast, and specific health recommendations. These recommendations are tiered according to PSI levels and target different population groups:

• Moderate (PSI 51-100): Most people can continue with normal activities. Those who are unusually sensitive may wish to reduce prolonged or strenuous outdoor physical exertion.
• Unhealthy (PSI 101-200): The general population should reduce prolonged or strenuous outdoor physical exertion. Vulnerable groups (elderly, pregnant women, children, persons with chronic heart or lung disease) should minimize outdoor physical exertion.
• Very Unhealthy (PSI 201-300): The general population should avoid prolonged or strenuous outdoor physical exertion. Vulnerable groups should avoid all outdoor physical exertion.
• Hazardous (PSI >300): The general population should avoid all outdoor activities. Vulnerable groups should remain indoors, keep windows closed, and use air purifiers if available.

Beyond advisories, the government ensures the availability of N95 masks, which are effective in filtering out PM2.5 particles, especially for vulnerable groups and lower-income households. Public education campaigns are also launched to inform residents about protective measures and the importance of monitoring air quality updates.

Regional Cooperation and Future Outlook

Recognizing that the haze is a transboundary issue requiring collective action, Singapore has actively championed regional cooperation through ASEAN. The cornerstone of these efforts is the ASEAN Agreement on Transboundary Haze Pollution (AATHP), signed in 2002. This legally binding agreement commits signatory nations to cooperate in monitoring, preventing, and mitigating transboundary haze pollution. Under the AATHP, initiatives such as the ASEAN Haze Monitoring System (AHMS) have been established, providing satellite-based fire hotspot data to member states. Sub-regional Ministerial Steering Committees on Transboundary Haze Pollution (MSC) also meet regularly to coordinate efforts, share best practices, and address the root causes of the fires.

Despite these frameworks, challenges persist. Issues such as sovereignty, enforcement of national laws against errant companies, and economic considerations often complicate effective implementation. Many of the fires are set by smallholders or companies that might find it economically difficult to adopt more sustainable land-clearing methods. Addressing the haze thus requires not only diplomatic pressure and technological solutions but also capacity building, providing alternative livelihoods, and promoting sustainable agricultural practices in the source countries.

Looking ahead, with dry conditions expected to persist over Singapore and the surrounding region, and with prevailing winds continuing to bring smoke plumes from Sumatra and Kalimantan, the NEA’s forecast of high-moderate to low-unhealthy PSI levels underscores the need for ongoing vigilance. While Singapore has robust systems in place to manage the local impact of haze, the long-term solution lies in concerted, sustained regional efforts to prevent and extinguish the fires at their source. Until then, residents are encouraged to stay informed through official NEA channels, heed health advisories, and take necessary precautions to protect themselves and their families from the evolving haze situation.