Hong Kong’s Air Quality Objectives
The Government has set out Hong Kong’s Air Quality Objectives (AQOs) in the Air Pollution Control Ordinance (Cap. 311), and is required to review the AQOs at least once every five years and submit a report of the review to the Advisory Council on the Environment.
Hong Kong Air Quality Objectives
| Pollutant | Averaging time | Concentration limit [i] (μg/m3) | Number of exceedances allowed |
|---|---|---|---|
|
Sulphur dioxide |
10-minute |
500 |
3 |
|
24-hour |
40 |
3 |
|
|
Respirable suspended particulates (PM10) [ii] |
24-hour |
75 |
9 |
|
Annual |
30 |
Not applicable |
|
|
Fine suspended particulates (PM2.5) [iii] |
24-hour |
37.5 |
18 |
|
Annual |
15 |
Not applicable |
|
|
Nitrogen dioxide |
1-hour |
200 |
18 |
|
24-hour |
120 |
9 |
|
|
Annual |
40 |
Not applicable |
|
|
Ozone |
8-hour |
160 |
9 |
|
Peak season |
100 |
Not applicable |
|
|
Carbon monoxide |
1-hour |
30,000 |
0 |
|
8-hour |
10,000 |
0 |
|
|
24-hour |
4,000 |
0 |
|
|
Lead |
Annual |
0.5 |
Not applicable |
Note:
Air Quality Management in Hong Kong
The overall policy objective for air quality management in Hong Kong is to achieve as soon as reasonably practicable and to maintain thereafter an acceptable level of air quality to safeguard the health and well-being of the community, and to promote the conservation and best use of air in the public interest. In this regard, we put in force an updated Hong Kong's AQOs on 11 April 2025 to further protect public health.
The prevailing AQOs are benchmarked against a combination of interim and ultimate targets under World Health Organisation's (WHO) WHO Global Air Quality Guidelines (AQGs). To continuously improve air quality, we have implemented a wide range of measures to control emissions from power plants, industrial and commercial activities, motor vehicles and marine vessels, as well as setting regional emission reduction targets for key air pollutants together with the Guangdong Provincial Government. The overall air quality of Hong Kong has been improving in recent years, with concentrations of major air pollutants continuously decreasing and remaining at low levels since Hong Kong’s return to the motherland.
The Government will review the AQOs at least once every five years to monitor the progress of air quality improvement and the effectiveness of measures. The Government’s ultimate goal, in the long run, is for Hong Kong’s air quality to fully meet the ultimate targets set out by the WHO.
Historical Air Quality Objectives and Reviews
Air Pollution Control Strategies
Related Documents
Links
Air Quality of Hong Kong
Mainland China and Overseas Air Quality Objectives/Standards
