| Background Information of API
Air pollutants can cause long-term health effects to us. However, air pollution levels
sometimes can become so high that they may have more immediate impacts for those with
existing heart or respiratory illnesses. The Air Pollution Index is to let you know about
the quality of the air at the moment.
The API converts air pollution data from several types of pollutants into a value
ranging from 0 to 500. Those pollutants are nitrogen dioxide, sulphur dioxide, ozone,
carbon monoxide and respirable suspended particulates. APIs for each of these five
pollutants are calculated and the highest API number is reported as the API of that
hour.
API and Air Quality
The API ranges from 0 to 500 and is divided into 5 bands according to the potential
effects on health. The potential health effects for different ranges of API values
are as follows.
| Air Pollution Index |
Air Pollution Level |
Health Implications |
| 0 - 25 |
Low |
None expected. |
| 26 - 50 |
Medium |
None expected for the general population. |
| 51 - 100 |
High |
Very few people, if any, may notice immediate health effects.
Long-term effects may, however, be observed if you are exposed to such levels
for a long time. |
| 101 - 200 |
Very High |
People with existing heart or respiratory illnesses will
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 will
experience significant aggravation of their symptoms and there will be also
widespread symptoms in the healthy population. These include eye irritation,
wheezing, coughing, phlegm and sore throat. |
Points to Note
The suggested precautionary actions are summarised below.
| Air Pollution Index |
Air Pollution Level |
Precautions |
| 0 - 25 |
Low |
No response action is required. |
| 26 - 50 |
Medium |
No response action is required. |
| 51 - 100 |
High |
No immediate response action is suggested - long-term effects may,
however, be observed if exposed at this level persistently for months
or years. |
| 101 - 200 |
Very High |
Persons with existing heart or respiratory illnesses (such as
coronary heart and cardiovascular diseases, asthma, chronic bronchitis and
chronic obstructive airways diseases) are advised to reduce
physical exertion and outdoor activities. |
| 201 - 500 |
Severe |
The general public are advised to reduce physical exertion and
outdoor activities. |
As the health effects on individuals may vary, you should seek advice
from a medical doctor if you are in doubt or feel uncomfortable.
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Air Pollution Index (API)