Hong Kong
The API has been in use in Hong Kong since June 1995. It is measured and updated hourly by the Environmental Protection Department (EPD). Moreover, the EPD makes forecast on the API for the following day everyday.
The API is based on the level of 6 atmospheric pollutants, namely sulfur dioxide (SO2), nitrogen dioxide (NO2), respirable suspended particulates, carbon monoxide (CO), ozone (O3), lead (Pb), measured at all the monitoring stations throughout the territory.
There are 11 General Stations and 3 Roadside Stations. The former includes Central / Western, Eastern, Kwai Chung, Kwun Tong, Sha Tin, Sham Shui Po, Tai Po, Tap Mun, Tsuen Wan, Tung Chung, and Yuen Long; the later Causeway Bay, Central, and Mong Kok.
In Hong Kong, there are two types of API: General API and Roadside API. The EPD reports the latest APIs hourly.
The index and the air quality objectives were set in 1987; and pollutant levels are measured over varying periods, in μg/m3. There are hourly, 24 hour and annual targets for sulfur dioxide and nitrogen dioxide, and 24 hour and annual targets for particulates.
The table below shows the official Health Implications of the respective API levels in Hong Kong.
| API | Air Pollution Level |
Health Implications; |
|---|---|---|
| 0 - 25 | Low | Not expected. |
| 26 - 50 | Medium | Not expected for the general population. |
| 51 - 100 | High | Acute health effects are not expected but chronic effects may be observed if one is persistently exposed to such levels. |
| 101 - 200 | Very High | People with existing heart or respiratory illnesses may notice mild aggravation of their health conditions. Generally healthy individuals may also notice some discomfort. |
| 201 - 500 | Severe | People with existing heart or respiratory illnesses may experience significant aggravation of their symptoms. There may also be widespread symptoms in the healthy population (e.g. eye irritation, wheezing, coughing, phlegm and sore throats). |
In 1998, the Education Bureau's recommended schools to curtail outdoor activities when the index reached 200, whereas leading healthcare advocates are urging that the level be revised to 100. The World Health Organisation revised its air quality guideline levels of sulfur dioxide, nitrogen dioxide and ozone in 2006 in light of new scientific evidence. The WHO also introduced new measurement guidelines for very small particulates which are more dangerous to pulmonary function. At the '200' level, Hong Kong levels of SO2 (800μg/m3) and NO2 (1,130μg/m3) are 40 times and 5½ times WHO guidelines respectively; the equivalent for particulates (350μg/m3) is 7 times WHO guidelines.
Read more about this topic: Air Pollution Index