• Sulphur Dioxide
• A colourless gas when in high levels can cause humans respiratory problems.

• Carbon Monoxide
  • A toxic gas difficult to identify and is fatal at high levels. Has been known to cause headaches and impaired vision.
• Nitrogen Dioxide
  • A gas that irritates the eye, nose and throat.
• Ground-level Ozone
  • Causes respiratory problems from the mildest (cough) to the most severe (aggravated asthma).
• Violate Organic Compounds
• Particulate Matter.(i.e. PM10/2.5)
  • Made up of fine particles that can cause a range of respiratory and heart problems depending on the size of the particles.

Particulate matter is basically particles of solids or droplets of liquid. They are sometimes emitted directly from a source or are formed when pollutants in the atmosphere react with each other. These particles come in a wide range of sizes. Those that are smaller than 10 micrometers (i.e. PM10) are potentially harmful to our health for they can get into our lungs to do some serious damage. These PM10 particles actually damage human health and could cause many different respiratory effects on us. Also, these PM10 are produced from the haze with the many minute particles of dust and smog suspended in the air during the haze.

In order to measure the amount of pollutants in the air of a certain place, indexes are essential to enable environmentalists to express the degree of pollution in a way that is universally understood. With the indexes, media sources will be able to report air quality daily and enable the public to be aware of the air pollution levels. Across the globe, several types of air pollutant indexes exist. Here we will be introducing a few indexes used in SEA countries and other countries.

Singapore uses PSI to keep track of air quality. According to e-notes.com, it does so by “measuring the concentrations of pollutants in the air, in parts per million”.
The table below describes the general health effects for the various levels of air pollution.

Fig 1.1 taken from http://app.nea.gov.sg/cms/htdocs/article.asp?pid=1251with permission.

The PSI was developed by the United States Environmental Protection Agency (USEPA). It incorporates only particulate matter smaller than 10 (PM10). In 1999, US EPA changed the PSI to the AQI so that it will be more accurate in calculating PM2.5 and ozone gases rather than just PM10.

According to Wikipedia, the AQI is also an indicator of air quality at a specific place. It measures mainly the ground-level ozone and volatile organic compounds (VOCs) in the presence of sunlight”, which is brought about by mainly human activities. It is mainly used in the US and Canada. Particulates (fine particles of either solid or liquid suspended in the air) may also include sulphur dioxide and nitrogen dioxide, a gas poisonous to inhale, but is still a common air pollutant.
According to AirNow, A cross-agency U.S. Government Web site, AQI is divided into the following 6 categories, differented by colors.

Fig 2.1 modified from http://www.airnow.gov/index.cfm?action=aqibroch.aqi#2 with permission.

Let us now compare the difference between the two indexes discussed so far, the AQI and PSI.

Air Pollution Index (API) is used in Hong Kong and Malaysia. It measures the amount of the 4 main greenhouses gases (sulphur dioxide, carbon monoxide, ozone and nitrogen dioxide) in a day based on the possible health effects of air pollutants.

When level(s) of the pollutant(s) bridge(s) the healthy range, the indicator would rise to 100 or above. Advice pertaining to precautionary actions would then be disseminated to public by the Hong Kong Environmental Protection Department.

Fig 3.1 modified from http://cleanair.hk/eng/air_pollution.htm, with permission.

The Air Pollution Index is also used in Malaysia. However, the API Structure in Malaysia differs from that used in Hong Kong. Four of this index’s components are measured in parts per million by volume. They are carbon monoxide, ozone, sulphur dioxide and nitrogen dioxide. The Malaysian API can exceed 500. When it reaches this level, a state of emergency is declared in the affected area.

The table below shows the API Status indicator used in Malaysia.

API Status Indicator

Let us now compare the difference between the two indexes discussed so far, the AQI and PSI.

(Translated, it means: Indonesia's Standard Air Pollution Index or Standard Air Pollution Index)

The ISPU is used by Indonesia in calculating the haze level. It basically takes into consideration 3 major pollutants that affect air quality which are namely: ozone, sulphur dioxide and PM10. The crux of the ISPU is that it shows the air quality of major air pollutants and its potential threat to the general population’s health in one reading. Two other air quality indicators are also included, Ground Level Ozone and Toxic Air Release, but Ground level Ozone is reported separately due to changes in regulations regarding it.

Fig 4.1 generated form data gathered at http://www.theharbinger.org/xviii/000411/envision1.html

Acknowledgements

We had some difficulties in researching about ISPU and we posted a question on Yahoo! Answers. Big thanks to rynkiedink of Yahoo!Answers for providing us with the links and information. We would like to suggest that the Indonesian government be more transparent and release ISPU readings to the public (i.e. English Website [something which we could not find])

• Perhaps the government should be more transparent and release information to
  the public (i.e. English Website [something which we could not find])
  
• Through this, researchers will then be able to gain more information about the
  situation and hence, be able to conduct more research.

After researching the four pollutant indexes above, we are aware that there are other indexes in use across the globe that we have not explored. Our team then had a question in mind — why do people in all over the world have to create so many different indexes to measure air quality? We felt that if we could have one single, standardized index that would be used throughout all the countries, then it would make work easier for both the citizens and professionals (environmentalists, researchers, scientists). There would then be no more confusion between people of different nationality who want to know the air quality in each others country.

Therefore, we felt that it definitely would be excellent if the governments or rulers of all countries arrange to come together to develop and agree on a standardized air quality index to facilitate the measurement of air quality in their respective countries.