Pollutant Standards Index

History

The PSI is based on a scale devised by the United States Environmental Protection Agency (EPA) to provide a way for broadcasts and newspapers to report air quality on a daily basis. The PSI has been used in a number of countries including the United States and Singapore.

Since 1999, the US EPA has replaced the Pollution Standards Index (PSI) with the Air Quality Index (AQI) to incorporate new PM2.5 and ozone standards.

Prior to 1 April 2014, Singapore published the PSI and the 1-hour PM2.5 reading separately. This 3-hour PSI is unique to Singapore and was introduced in 1997 to provide additional air quality information which would better reflect a more current air quality situation. In 2016, the 3-hour PSI was phased out on the grounds that the 1-hour PM2.5 reading was a better indicator of the current air quality.

Definition of the PSI used in Singapore

The PSI considers six air pollutants: sulphur dioxide (SO2), particulate matter (PM10), fine particulate matter (PM2.5), nitrogen dioxide (NO2), carbon monoxide (CO) and ozone (O3).

The concentrations of these pollutants in the ambient air are measured via a network of air monitoring stations located around Singapore.

A sub-index value is computed for each pollutant based on the pollutant's ambient air concentration. The highest sub-index value is then taken as the PSI value. In other words, the PSI is determined by the pollutant with the most significant concentration.

During haze episodes, PM2.5 is the most significant pollutant.

The PSI is reported as a number on a scale of 0 to 500. The index figures enable the public to determine whether the air pollution levels in a particular location are good, unhealthy, hazardous or worse. The following PSI table is grouped by index values and descriptors, explaining the effects of the levels, according to Singapore's National Environment Agency (NEA).

Note: This chart reflects the guidelines used in Singapore and may differ from other countries. Health advisories are based on the US EPA's guidelines. Only the 24-hour PSI value and not the 3-hour PSI value is correlated to the health effects outlined in NEA's advisories.

Record values of the PSI

Main article: Southeast Asian haze

Singapore has been regularly hit by smoke haze from forest fires in nearby Sumatra, Indonesia, brought over by wind. These forest fires have been attributed to the slash-and-burn method favoured by several large plantation owners to clear their land, as opposed to a more expensive and inconvenient mechanical approach using excavators and bulldozers. In June 2013, severe haze hit Singapore, pushing the nation's PSI into Hazardous levels for the first time in its history. Presently, the highest 3-hour PSI reading on record in Singapore is 471 on 20 October 2015 at 11 pm (GMT+8).

Association with health outcomes

Singapore's computation of PSI and NEA's definitions of PSI ranges have been shown to correlate with a number of health outcomes including all-cause mortality. For sudden cardiac deaths, every increment of 30 units in PSI correlated with 8.15% increased risk of out-of-hospital cardiac arrest on the same day of exposure. This risk was found to remain elevated for 1–5 days after exposure. Similar short-term associations were subsequently found for acute myocardial infarction and acute ischemic stroke in analyses of national registries. In terms of healthcare utilization, both country-wide Emergency Department visits and hospital admissions were increased per unit increase in PSI.

References

See http://en.wikipedia.org/wiki/Wikipedia:Footnotes for an explanation of how to generate footnotes using the tags, and the template below.

References

1. "PSI Reading". National Environment Agency of Singapore.
2. "Frequently Asked Questions (FAQs) On Haze". National Environment Agency of Singapore.
3. (20 June 2013). "Govt says it will move towards publishing 24-hour PSI, PM2.5 data on hourly basis". TODAY.
4. "National Environment Agency - Air Pollution FAQ".
5. (10 September 2012). "Written Reply by Dr Vivian Balakrishnan, Minister for the Environment and Water Resources to Parliamentary Question on Air Quality Reporting". Ministry of the Environment & Water Resources (Singapore).
6. "What is Air Quality Index AQI". Business Standard India.
7. "Computation of the Pollutant Standards Index (PSI)". National Environment Agency of Singapore.
8. "Frequently Asked Questions (FAQs) On Haze". National Environment Agency of Singapore.
9. "PSI Readings". National Environment Agency.
10. (18 June 2013). "Singapore hit by highest haze levels in 16 years". BBC News.
11. (19 June 2013). "Haze in Singapore hits new high, PSI at 321 at 10pm". The Straits Times.
12. (20 October 2015). "PM2.5 levels hit 471 as haze situation worsens". Today.
13. (6 September 2019). "Acute Health Impacts of the Southeast Asian Transboundary Haze Problem-A Review". International Journal of Environmental Research and Public Health.
14. (November 2018). "Health impacts of the Southeast Asian haze problem – A time-stratified case crossover study of the relationship between ambient air pollution and sudden cardiac deaths in Singapore". International Journal of Cardiology.
15. (November 2018). "The Relationship Between Ambient Air Pollution and Acute Ischemic Stroke: A Time-Stratified Case-Crossover Study in a City-State With Seasonal Exposure to the Southeast Asian Haze Problem". Annals of Emergency Medicine.
16. (2019-03-19). "Time-Stratified Case Crossover Study of the Association of Outdoor Ambient Air Pollution With the Risk of Acute Myocardial Infarction in the Context of Seasonal Exposure to the Southeast Asian Haze Problem". Journal of the American Heart Association.
17. (February 2020). "Impact of Air Pollution and Trans-Boundary Haze on Nation-Wide Emergency Department Visits and Hospital Admissions in Singapore". Annals of the Academy of Medicine, Singapore.
18. and