|
|
|
|
|
1.
|
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:
PSI Value | PSI Descriptor | 0 to 50 | Good | 51 - 100 | Moderate | 101 - 200 | Unhealthy | 201 - 300 | Very unhealthy | Above 300 | Hazardous |
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.
|
|
|
|
|
|
2.
|
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.
|
|
|
|
|
|
3.
|
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.
|
|
|
|
|
|
4.
|
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.
|
|
|
|
|
|
5.
|
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.
|