Air Quality Objectives
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, Air Quality Objectives (AQOs) for seven widespread air pollutants were established in 1987 under the Air Pollution Control Ordinance (APCO) based on international standards as yardsticks for air quality management. These derived from scientific analyses of the relationship between pollutant concentrations in the air and the associated adverse effects of the polluted air on the health of the public. The established AQOs apply to the whole territory.
Possible ways to achieve and maintain AQOs include preventive measures through intervention in the planning stage, or enforcement of APCO and its subsidiary legislation to alleviate excessive emissions.
AQOs may be reviewed from time to time to include a wider range of air pollutants and, if necessary, to tighten the standards taking into account international developments for better protection of the health and well being of the community.
| Pollutant |
Concentration in Microgrammes per Cubic Metre (i) |
Health Effects of Pollutant at Elevated Ambient Levels |
| Averaging Time |
1hr
(ii) |
8hrs
(iii) |
24hrs
(iii) |
3mths
(iv) |
1yr
(iv) |
| Sulphur Dioxide |
800 |
-- |
350 |
-- |
80 |
Respiratory illness; reduced lung function; morbidity and mortality rates increase at higher levels. |
| Total Suspended Particulates |
-- |
-- |
260 |
-- |
80 |
Respirable fraction has effects on health. |
| Respirable Suspended Particulates (v) |
-- |
-- |
180 |
-- |
55 |
Respiratory illness; reduced lung function; cancer risk for certain particles; morbidity and mortality rates increase at higher levels. |
| Nitrogen Dioxide |
300 |
-- |
150 |
-- |
80 |
Respiratory irritation; increased susceptibility to respiratory infection; lung development impairment. |
| Carbon Monoxide |
30000 |
10000 |
-- |
-- |
-- |
Impairment of co-ordination; deleterious to pregnant women and those with heart and circulatory conditions. |
| Photochemical Oxidants (as ozone) (vi) |
240 |
-- |
-- |
-- |
-- |
Eye irritation; cough; reduced athletic performance; possible chromosome damage. |
| Lead |
-- |
-- |
-- |
1.5 |
-- |
Affects cell and body processes; likely neuro-psychological effects, particularly in children; likely effects on rates of incidence of heart attacks, strokes and hypertension. |
(i) |
|
Measured at 298K(25°C) and 101.325kPa (one atmosphere) |
|
|
|
(ii) |
|
Not to be exceeded more than three times per year. |
|
|
|
(iii) |
|
Not to be exceeded more than once per year. |
|
|
|
(iv) |
|
Arithmetic means. |
|
|
|
(v) |
|
Respirable suspended particulates means suspended particles in air with a nominal aerodynamic diameter of 10 micrometres or smaller. |
|
|
|
(vi) |
|
Photochemical oxidants are determined by measurement of ozone only. |
|
|