Q1) What are our sources of air pollutants?

The main sources of air pollution in Singapore are from the burning of fossils fuels for energy generation in industries, power stations and in the transportation sector. Other sources include open burning of waste materials and transboundary smoke haze.

Please also refer to FAQ on Air Quality

Q2) What are the health effects of air pollutants and what are the standards set to protect public health?

Air pollutants like sulphur dioxide, particulate matter, ozone, carbon monoxide and nitrogen dioxide when present in high concentrations can affect the normal functions of the body. The United States Environmental Protection Agency (USEPA) has set standards for ambient air quality to protect public health. NEA uses the USEPA standards to assess Singapore's ambient air quality.

Please refer to USEPA website for the USEPA ambient air quality standards.

Q3) What is NEA/MEWR doing to improve our air quality?

The following measures are adopted by NEA/MEWR to control air pollution and to improve air quality in Singapore:

• Minimising pollution at source by stipulating stringent air emission limits and fuel quality on industries and motor vehicles e.g. EURO IV emission standards for diesel vehicles.
• Stringent legislation and enforcement to control air pollution.
• Proper land use planning and judicious siting of pollutive industries away from population centres.
• Promoting cleaner energy and energy efficiency e.g. green vehicles, use of compressed natural gas (CNG), renewable energy sorce, energy efficient buildings, etc.

Please also refer to the following websites on:

Pollution Control

EPD Annual Report

Code Of Practice On Pollution Control

Q4) What is PSI?

How is the index measured?

What is the meaning of the index?

PSI stands for 'Pollutant Standards Index'. It is an index developed by the United States Environmental Protection Agency (USEPA) to provide accurate, timely and easily understandable information about daily levels of air pollution.

The ambient air in Singapore is monitored through a telemetric network of  air monitoring stations strategically located in different parts of Singapore.

The monitoring stations measure air pollutants such as sulphur dioxide, nitrogen dioxide, ozone, carbon monoxide and particulate matter called PM10 (particulate matter of 10 microns or smaller in size). These pollutants are used in the determination of the index.

The PSI value gives an indication of the air quality as shown:

Technical details on how the PSI is calculated can be found in this link: Computation of PSI

Air quality indices similar to the PSI are used in the United States, Canada, Australia, China, Hong Kong, Taiwan, Malaysia and Indonesia.

Q5) Is the PSI reading in Singapore the same as Malaysia?

The Air Pollutant Index (API) used in Malaysia is also based on the same 5 major air pollutants as the PSI but differs from the PSI in the standards used to derive the sub-indices for sulphur dioxide, nitrogen dioxide and ozone. The standards used to compute the sub-indices for PM10 and carbon monoxide are identical to those of the PSI.

Q6) How are the regions for the regional PSI defined and how is the regional PSI determined?

The delineation used to define the north, south, east, west and central regions is similar to that used for NEA's weather reporting posted at MSD website The regional PSI is based on the five major air pollutants (sulphur dioxide, nitrogen dioxide, ozone, carbon monoxide and particulate matter PM10) monitored at the monitoring stations in each of the regions.

Q7) Should residents living in regions with higher PSI be concerned?

There is no cause for concern as long as the PSI readings are less than or equal to 100 i.e. air quality is in the 'good' or 'moderate' range. When the readings exceed 100, NEA will issue health advisories which will include precautions that the public can take to avoid excessive exposure.

Q8) What are the general health effects associated with the different air quality categories?

The air quality categories based on PSI and the general health effects associated with the different categories are summarized as follows:

Q9) When are we more likely to be more affected by smoke haze?

Past smoke haze episodes occurred largely within the period of May to October. We are likely to be impacted by smoke haze when there are forest fires in the region and the prevailing Southwest Monsoon winds blow the smoke from the fires in our direction.

Q10) Since the haze problem is an annual one that has been around for some time are there any realistic ways to deal with it? Especially considering the fact that the root cause lies outside Singapore? What sort of contingency plan has NEA in place to cope with the haze? What can be done about the haze problem, which is getting more serious?

We have a haze action plan which describes the actions that will be taken by various authorities should the PSI enter the unhealthy range. This action plan is based on the general health effects for the various PSI ranges. As an example, NEA will increase the frequency of press releases on PSI readings and health advisories in order to help the public minimise the impact of haze on their health.

The public is advised to look out for NEA's PSI announcements and health advisories. (For details of the PSI Health Advisories, please see Health Advisories)

Q11) Are there any weather conditions that will intensify the effects of the haze?

There is a phenomenon known as the El Nino which tends to produce very dry weather conditions in the region. Its appearance will intensify the effects of the fires in Indonesia.

Q12) Can the haze be controlled or made less harmful to people?

The public can reduce the impact of haze on their health by following the health advisories issued by NEA.

Q13) Is forecasting of haze condition possible?

Forecasting of haze condition is not easy as much depend on the variable wind conditions.

Q14) When was the Inter-Ministry Haze Task Force set up? Which Ministries are involved?

The Inter-Ministry Haze Task Force was set up in Sep 1994. It comprises officers from MITA, MOT, MOH, MOE, SSC, MTI, EDB, MINDEF, MCYS, PA, MOM, BCA, MFA and MEWR, with NEA chairing.

Q15) Why is it that the 3-hr PSI released during the smoke haze periods is at times low when the visibility is poor?

When a 3-hr PSI reading is released during the smoke haze periods, it is for air quality for the immediate past three hours. It therefore does not correspond to what you may observe at the point when you hear the PSI announcement.

Poor visibility does not necessarily mean higher particles levels in the air . Poor visibility can be due to many reasons e.g. presence of mist, sun reflection etc.

Q16) Under what circumstances do we need to wear mask and what are the advisories on the use of mask?

When the 24-h PSI level exceeds 150 in the 'Unhealthy' range, people with existing heart or respiratory ailments or those who are more susceptible to smoke haze are advised to wear a respiratory mask when they go outdoor. People with respiratory ailments are however, advised to consult their doctors on the use of respirator masks.

Respiratory masks, such as N95 masks, are designed to keep out fine particulate matter and hence, protect the wearers from breathing in the smoke haze particles in the air. The mask should be changed when it gets soiled or distorted in shape. Surgical masks and paper masks do not provide adequate protection from the haze particles.

Respiratory masks are available in commercial pharmacies and in Singhealth/NHG polyclinics. The public is advised to consult the pharmacists in attendance for advice on the right mask to use. The instructions for using the respiratory masks are provided with the masks. The public can also seek the advice of the sales staff or pharmacists on how to use the mask.