Mainland China
China's State Environment Protection Agency (SEPA) is responsible for measuring the level of air pollution in China. As of 28 August 2008, SEPA monitors daily pollution level in 86 of its major cities. The API level is based on the level of 5 atmospheric pollutants, namely sulfur dioxide (SO2), nitrogen dioxide (NO2), suspended particulates (PM10), carbon monoxide (CO), and ozone (O3) measured at the monitoring stations throughout each city.
API Mechanics
An individual score is assigned to the level of each pollutant and the final API is the highest of those 5 scores. The pollutants can be measured quite differently. SO2, NO2 and PM10 concentration are measured as average per day. CO and O3 are more harmful and are measured as average per hour. The final API value is calculated per day.
The scale for each pollutant is non-linear, as is the final API score. Thus an API of 100 does not mean twice the pollution of API at 50, nor does it mean twice as harmful. While an API of 50 from day 1 to 182 and API of 100 from day 183 to 365 does provide an annual average of 75, it does not mean the pollution is acceptable even if the benchmark of 100 is deemed safe. This is because the benchmark is a 24 hour target. The annual average must match against the annual target. It is entirely possible to have safe air every day of the year but still fail the annual pollution benchmark.
API and Health Implications (Daily Targets)
| API | Air Pollution Level |
Health Implications |
|---|---|---|
| 0 - 50 | Excellent | No health implications |
| 51 -100 | Good | No health implications |
| 101-150 | Slightly Polluted | Slight irritations may occur, individuals with breathing or heart problems should reduce outdoor exercise. |
| 151-200 | Lightly Polluted | Slight irritations may occur, individuals with breathing or heart problems should reduce outdoor exercise. |
| 201-250 | Moderately Polluted | Healthy people will be noticeably affected. People with breathing or heart problems will experience reduced endurance in activities. These individuals and elders should remain indoors and restrict activities. |
| 251-300 | Heavily Polluted | Healthy people will be noticeably affected. People with breathing or heart problems will experience reduced endurance in activities. These individuals and elders should remain indoors and restrict activities. |
| 300+ | Severely Polluted | Healthy people will experience reduced endurance in activities. There may be strong irritations and symptoms and may trigger other illnesses. Elders and the sick should remain indoors and avoid exercise. Healthy individuals should avoid out door activities. |
Read more about this topic: Air Pollution Index
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