101-150 Unhealthy for sensitive groups is usually orange
151-200 Unhealthy is usually red
201-300 Very unhealthy is usually purple
301-500 Hazardous is usually maroon
The EPA's AQI 100 corresponds to 0.08 ppm ozone, and to other levels for other pollutants. Source: EPA
The AQI standards in Canada are notably more protective of health. The current health classifications used by the Meteorological Service Of Canada (MSC) are as follows:
0-25---: Good (green)
2650: Fair (yellow)
51-100: Poor (orange)
101+: Very poor (red)
In Ontario , 31 is the upper limit for good and 32 the lower limit for moderate. Zero to 15 is classified as very good, and is given the color blue.
In June 2007, the EPA proposed a slight possible tightening of the pollution standards associated with smog after an independent EPA scientific board said that the standard “needs to be substantially reduced” and that there is “no scientific justification” for retaining the current, weaker standard. http://www.lungusa.org/site/apps/nl/content3.asp?c=dvLUK9O0E&b=40404&ct=3983577
In light of the new scientific findings, one should expect adjustments in the AQI such that pollution currently denoted as "moderate" will in the future be recognized as "unhealthy."
The United States Environment Protection Agency (USEPA) developed the Pollutant Standards Index (PSI) to provide accurate, timely and easily understandable information about daily levels of air pollution.
It is no longer in use, having been replaced by the AQI, which is more sensitive. For example, particulate matter with an aerodynamic diameter less than 2.5 Micrometre s (PM2.5) is a sub index, replacing the less sensitive PM10 component of the PSI.
United Kingdom
The Met Office of the United Kingdom (UK) issues air quality forecasts wherein the level of pollution is described either as an index (ranging from 1 to 10) or as a banding (low, moderate, high or very high). These levels are based on the health effects of each pollutant.
The forecast is produced for a number of different pollutants and their typical health effects are shown in the following table.
The Air Pollution Index (API) levels for Hong Kong are related to the measured concentrations of ambient respirable suspended particulate (RSP), sulphur dioxide (SO2), carbon monoxide (CO), ozone (O3) and nitrogen dioxide (NO2) over a 24-hour period based on the potential health effects of air pollutants.
An API level at or below 100 means that the pollutant levels are in the satisfactory range over 24 hour period and pose no acute or immediate health effects. However, air pollution consistently at "High" levels (API of 51 to 100) in a year may mean that the annual Hong Kong "Air Quality Objectives" for protecting long-term health effects could be violated. Therefore, chronic health effects may be observed if one is persistently exposed to an API of 51 to 100 for a long time.
"Very High" levels (API in excess of 100) means that levels of one or more pollutant(s) is/are in the unhealthy range. The Hong Kong Environmental Protection Department provides advice to the public regarding precautionary actions to take for such levels.
The air quality in Malaysia is reported as the API or Air Pollution Index. Four of the index's pollutant components (i.e., carbon monoxide, ozone, nitrogen dioxide and sulfur dioxide) are reported in Ppmv but PM10 particulate matter is reported in μg/m³.
Unlike the American AQI, the index number can exceed 500. Above 500, a State Of Emergency is declared in the reporting area. Usually, this means that non-essential government services are suspended, and all ports in the affected area closed. There may also be a prohibition on private sector commercial and industrial activities in the reporting area excluding the food sector.
For more information on the API reading please go here http://www.doe.gov.my/index.php?option=com_content&task=view&id=188&Itemid=370&lang=en
