In order to indicate to citizens how good or bad the air pollution is, Hong Kong's Environmental Protection Department (EPD) launched the Air Pollution Index (API) programme in 1995.
Air pollution levels are monitored in a number of districts in Hong Kong, and at specific busy roadside locations (see Figure 3). Click here for more background information on the API and for details of monitoring methods. The API index reflects the air monitoring results of a specific locality. As local weather conditions may affect the dispersion of air pollutants emitted, API predictions can be announced to warn people who are vulnerable to air pollution. Typically, API predictions are given along with the weather forecast.
The API levels are given in Table 1.6
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The API levels were established to reflect the health effects of air pollutants with respect to the concentrations of ambient RSP, sulphur dioxide (SO2), carbon monoxide (CO), ozone (O3) and nitrogen dioxide (NO2) over a 24-hour period. An API of 100 corresponds to the short-term Hong Kong Air Quality Objectives (AQO) which were established under the Air Pollution Control Ordinance.
An API level at or below 100 would mean that the levels of the named pollutants are in the satisfactory range over the 24-hour period and have posed or would 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 HKAQO for protecting long-term health effects could be violated. Therefore, chronic health effects may be observed if one is persistently exposed to API of 51 to 100 persistently for a long time.
An API level in excess of 100 means that levels of one pollutant or more are in the unhealthy range. In this case, the EPD would announce any precautionary action that needs to be taken.
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