Guide to air quality index...!
Well,haha!i din even realise Malaysia is using API instead of PSI...i'm outdated already!So,to those who still clueless about what is API,AQI,PSI...tht's it they r all used for measure the air quality...below is some of the guide which copy from some other post on web...!
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What is API?
An air pollution index system normally includes the major air pollutants which could cause potential harm to human health should they reach unsafe levels. The r pollutants included in Malaysia's API are ozone (03), carbon monoxide (CO), nitrogen dioxide (N02), sulphur dioxide (S02) and suspended particulate matter less than 10 microns in size (PM 10).
Generally, an air pollution index system is developed in easily understood ranges of values, instead of using the actual concentrations of air pollutants, as a means for reporting the quality of air or level of air pollution. To reflect the status of the air quality and its effects on human health, the ranges of index values could then be categorised as follows: good, moderate, unhealthy, very unhealthy and hazardous. The index values may also be categorised according to episode or action criteria, such as air pollutant levels within stipulated standards, or levels signifying conditions for alert, warning, emergency and significant harm. The key reference point in these air pollution index systems is the index value of 100 (the "safe" limit), which is based on the National Air Quality Standards or Guidelines for the specific air pollutants concerned.
The Recommended Malaysian Air Quality Guidelines (RMG) which form the basis for calculating the API are presented in Table 1. These guidelines have been derived from available scientific and human health data, and basically represent "safe levels" below which no adverse health effects have been observed. The RMG are generally comparable to the corresponding air quality standards recommended by the World Health Organisation and other countries.
The averaging time, which varies from 1 to 24 hours for the different air pollutants in the RMG, represents the period of time over which measurements is monitored and reported for the assessment of human health impacts of specific air pollutants. As such, the air pollution indices are normally monitored and reported for the same averaging times as those employed for the air qualitystandards/guidelines.
As mentioned earlier, the API system closely follows the PSI system of the United States. As such, the API breakpoints; at 100 for the various air pollutants correspond to the respective RMG concentrations regarded as being "safe levels". In other words, air quality with API values exceeding 100 are considered likely to cause health effects to the general public. Further, a linear correlation is assumed from API 0 to API 100, with the breakpoint at API 50 corresponding to 50% of the RMG concentration standards for the various air pollutants.
Breakpoints at API 200, 300, 400 and 500 directly mirror those of the PSI system of the United States. Figures 1 to 5 depict the sub-index functions of the five API pollutants involved, which are used as the basis for calculating the API. The respective breakpoints; and their corresponding episode category descriptors are also indicated. The relevant equations for the calculation of API values for the various concentration segments are also presented in Figures 1 to 5. The corresponding API values calculated as a function of the air pollutant concentrations are listed in Table 3. Further, air quality in terms of human health impacts and implications are categorised as follows under the API system adopted in Malaysia:
~ API DESCRIPTOR ~
0-50 good
51-100 moderate
101-200 unhealthy
201-300 very unhealthy
>300 hazardous
Table 4 summarises additional information on general human health effects and cautionary statements within each of the API categories.
Following the requirements of the RMG from the standpoint of human health implications, the API values are reported for varying averaging time as follows: V 10 and S02 on 24-hour running averages, CO on 8-hour running averages and 3 and N02 on 1-hour running averages. The API for PM 10 (based on a 24-hour period running average), reflects specifically levels of suspended particulate matter pollution and it may not be linked directly to visibility factors, as visibility often determined by results of semi-quantitative observations over relatively shorter time periods.
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What is AQI(aka PSI)?
The Air Quality Index (AQI), formerly the Pollutant Standards Index (PSI), is a uniform system developed by U.S. EPA to enable the public to determine whether air quality levels in a particular location are good, moderate, unhealthful, or worse. The AQI is used as an information tool to advise the public-- it is often presented along with the weather report in local newspapers. The AQI describes the general health effects associated with different pollution levels, as well as whatever precautionary steps may need to be taken if air pollution levels rise into the unhealthful range.
NOTE: In June 2000, EPA updated the PSI index and renamed it Air Quality Index (AQI). The AQI includes a new health risk category (unhealthy for sensitive groups) and two additional pollutants: ozone averaged over 8 hours, and fine particulate matter (PM 2.5).
WHAT DO AQI VALUES MEAN?
The AQI measures five criteria air pollutants (particulate matter, sulfur dioxide, carbon monoxide, nitrogen dioxide, and ozone), and converts the measured pollutant concentrations in a community's air to a number on a scale of 0 to 500. The intervals on the AQI scale relate to the potential health effects of the daily concentrations of each of these five pollutants. The most important number on this scale is 100, since this number corresponds to the National Ambient Air Quality Standard established under the Clean Air Act. A AQI level in excess of 100 means that a pollutant is in the unhealthful range on a given day; a AQI level at or below 100 means that a pollutant reading is in the satisfactory range.
The following table was constructed by the EPA to identify health effects associated with different levels of air pollution, along with the cautionary statements that would be appropriate if air pollution in a community were to fall into one of the "unhealthful" categories on the AQI scale:
~AQI Descriptor~
Up to 50 Good
50 to 100 Moderate
100 to 200 Unhealthful
200 to 300 Very Unhealthful
Over 300 Hazardous
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Actually the criteria between AQI(formerly PSI-Pollutant Standard Index)and API are almost the same!Maybe just the name is different from place to place or maybe the equipment used to measure are different!OMG so long never study science...i miss Chemistry so much esp. Organic Chemistry , Redox,Electron Config.,Nuclear Chem.....haiz ! T.T
To know more about PSI go to this
LINK
