Singapore's Air Pollution: A Hazardous Concern?

Singapore's air quality poses a significant risk to public health. As a city-state and island, Singapore's air pollution primarily comes from traffic and industry. The country is also affected by seasonal haze from forest fires in neighbouring countries, which can cause an increase in hospital admissions due to respiratory illnesses. Singapore's National Environment Agency (NEA) uses the Pollution Standards Index (PSI) to measure air quality, which is scored based on the density of six pollutants: PM2.5, PM10, carbon monoxide, ozone, nitrogen dioxide, and sulphur dioxide. The current PSI level in Singapore is 54, which is considered moderate. While the AQI levels are currently acceptable, some pollutants may be a concern for sensitive individuals.

Singapore's air pollution sources

Singapore's air quality is impacted by a range of sources, including both local and regional factors. As a city-state and island, Singapore's primary sources of air pollution are motor vehicles and industrial activities. The country's dense urban population and significant industrial presence contribute to the local air pollution levels.

Vehicular emissions from Singapore's large number of motor vehicles are a significant source of air pollution. To address this, the country has implemented schemes such as the Vehicular Emissions Scheme (VES) and the Commercial Vehicle Emissions Scheme (CVES), which aim to encourage the adoption of cleaner passenger and commercial vehicles, respectively. Additionally, all new vehicles must meet minimum emission standards, and existing vehicles are subject to fuel quality and exhaust emission regulations.

Industrial activities also play a role in Singapore's air pollution. The country's industrial facilities are screened before being allowed to operate, and they must incorporate pollution control measures to comply with the National Environment Agency's (NEA) air emissions standards. Regular monitoring of industry emissions is conducted by the NEA to ensure adherence to prescribed emission standards.

Another factor affecting Singapore's air quality is the seasonal haze from neighbouring island states, particularly Indonesia and Malaysia. During the slash-and-burn clearing of large areas of rainforest for agriculture, huge volumes of toxic smoke are produced. This smoke can be blown towards Singapore, impacting its air quality. While routine haze events have a minimal impact, severe haze events can lead to increased hospital admissions for respiratory illnesses.

The Singapore government actively works to maintain good air quality through various measures. They employ an integrated approach to urban and industrial planning, strict enforcement programs, and regular air quality monitoring. The country's air quality targets are based on the World Health Organization's (WHO) guidelines, and Singapore has met the targets for nitrogen dioxide, carbon monoxide, sulphur dioxide, and PM2.5 as of 2020. However, PM10 and ozone levels continue to be a challenge.

PSI and AQI levels

Singapore's air quality index is the Pollution Standards Index (PSI). It is an alternative to the Air Quality Index (AQI) used in the country. The PSI is based on a scale devised by the United States Environmental Protection Agency (EPA) and is calculated based on the density of six pollutants: PM2.5, PM10, carbon monoxide, ozone (O3), nitrogen dioxide (NO2), and sulphur dioxide (SO2). The PSI scale ranges from 0 to 300+, with “Good” air quality indicated by a score of 0 and “Hazardous” air quality indicated by a score of 300 or higher. The National Environment Agency (NEA) provides 24-hour PSI readings to help residents manage their exposure to air pollution.

The PSI has been used in Singapore to monitor air quality since 1997. In 2013, a severe haze event pushed the nation's PSI into the hazardous category for the first time. The highest 3-hour PSI reading on record occurred in October 2015, with a value of 471.

While Singapore's PSI values typically fall within the “Good” to “Moderate” range, the country experiences varying levels of air pollution throughout the year. The main sources of air pollution in Singapore are motor vehicles and industry. In addition, Singapore is occasionally affected by haze from forest fires in neighbouring countries, such as Indonesia and Malaysia, which can result in higher PSI values.

The AQI, which is used in many other countries, is another way to measure air quality. The AQI includes additional parameters and is calculated differently from the PSI. Singapore's overall AQI as of April 16, 2025, was 57, which is considered "Moderate". The AQI for specific pollutants in Central, Singapore, on the same date, ranged from 1 for ozone to 57 for fine particulate matter (PM2.5).

Health impacts

Air pollution in Singapore has been shown to pose a significant risk to public health. The country's air quality is affected by local sources of pollution, such as vehicles, power stations, and industries, as well as transboundary smoke haze from forest fires in neighbouring regions. While Singapore has implemented various measures to mitigate air pollution and its health impacts, the country still experiences periods of poor air quality that can have negative consequences for its residents.

One of the main health impacts of air pollution in Singapore is an increased risk of respiratory illnesses. During haze events caused by transboundary smoke or forest fires, residents may experience symptoms such as coughing, sneezing, and eye irritation. These events can also lead to an increase in hospital admissions for respiratory illnesses, particularly for vulnerable individuals such as the elderly, children, and those with existing heart or lung conditions. The 2015 haze, exacerbated by the El Niño weather phenomenon, resulted in public health costs for respiratory, eye, and skin conditions.

The fine particulate matter (PM2.5) and ground-level ozone (O3) present in the air contribute to the adverse health outcomes associated with air pollution. These particles can lodge deep in the lungs and have been linked to various health issues, including respiratory and cardiovascular diseases. Singapore's average PM2.5 concentration in 2019 was 19 µg/m³, exceeding the World Health Organization's recommended target of 10 µg/m³. This level of PM2.5 concentration indicates that sensitive individuals may experience respiratory symptoms and should avoid outdoor activities during periods of elevated pollution levels.

The health impacts of air pollution in Singapore are not limited to physical ailments but also extend to overall mortality rates. Studies have found a link between high Pollution Standards Index (PSI) levels and an increased short-term risk of mortality. Additionally, air pollution has been associated with specific cause-specific mortalities, including ischemic heart disease, stroke, chronic obstructive pulmonary disease, type 2 diabetes mellitus, lung cancer, and lower respiratory infections.

While Singapore has made efforts to address air pollution through initiatives such as the Vehicular Emissions Scheme (VES), Commercial Vehicle Emissions Scheme (CVES), and Early Turnover Scheme (ETS), the country continues to face challenges in maintaining good air quality. The complex interactions between air pollution, climate change, and human health require a comprehensive and multipollutant approach to effectively mitigate the health impacts of air pollution in Singapore.

Haze from neighbouring countries

Singapore's air pollution is mainly caused by motor vehicles and industry. However, the country has also been affected by haze from neighbouring countries, which has resulted in an increased risk of short-term mortality and respiratory illnesses.

The 1997 Southeast Asian haze, caused by major forest fires in Indonesia, is thought to have been the most severe on record. It led to dangerous pollution across most of Southeast Asia and affected air quality as far away as Sri Lanka. During this time, Singapore experienced 14 days when the Pollution Standards Index (PSI) was in the unhealthy range. The 2013 and 2015 haze outbreaks were also particularly severe, with the 2015 haze costing Indonesia an estimated $16 billion.

The haze has impacted Singapore's tourism industry and led to increased respiratory and haze-related ailments among Singaporeans. It has also disrupted schools, with closures affecting many parts of the country, sometimes for several weeks, due to hazardous air pollution.

In response to the haze, Singapore continuously monitors and reports air pollution levels using the PSI. The country has 15 air-monitoring stations that measure air pollutants such as sulphur dioxide, oxides of nitrogen, ozone, carbon monoxide, and particulate matter. The PSI then indicates the air quality, ranging from good (PSI 0-50) to hazardous (PSI 300 and above).

Real-time air quality monitoring

Singapore's air pollution is caused primarily by motor vehicles and industry. The country also experiences seasonal haze from forest fires in neighbouring countries, which can cause an increase in hospital admissions due to respiratory illnesses.

Singapore's National Environment Agency (NEA) provides a 24-hour Pollution Standards Index (PSI) reading, which measures the density of six pollutants: PM2.5, PM10, carbon monoxide, ozone (O3), nitrogen dioxide (NO2), and sulphur dioxide (SO2). The PSI scale ranges from 0 to 300+, with "Good" to "Hazardous" ratings and a colour-coded scale from green to red.

Additionally, there are browser plugins available for Firefox and Microsoft application stores, allowing users to access real-time air quality information for Singapore on their desktop and mobile devices. Symbian device users can also install widgets specifically designed for their devices. These tools enable residents and visitors to stay informed about the air quality in Singapore and make necessary adjustments to their activities and exposure.

Frequently asked questions