Air Pollution Index

Main Content

The Air Pollution Index (API) compiled by the Environmental Protection Department informs you about the air pollution level in Hong Kong. Here you can learn how the API works and what it can tell you about the level of air pollution.

How the API Works

The API converts the levels of air pollutants such as nitrogen dioxide, sulphur dioxide, ozone, carbon monoxide and respirable suspended particulates measured at each air quality monitoring station into one easy to understand number ranging from 0 to 500. EPD reports both general and roadside APIs obtained from each of its general stations and roadside stations. The APIs of each station are released every hour to keep you up to date all day, every day.

What the API Reveals

The API reveals five broad levels of air pollution and how they can affect you.

Air Pollution Level	API Readings	Air Quality Status
Low	0-25	Air quality is well within acceptable standards, with no cause for concern.
Medium	26-50	Air quality is still within acceptable standards
High	51-100	Air quality is within the short term standard but is worse than the long term standard
Very High	101-200	Air quality is worse than both the short and long term standards
Severe	201-500	Air quality is significantly worse than both the short term and long term standards

If you are exposed to low to medium levels of air pollution, there is no general concern. For high level of pollution, there is no immediate concern but long-term effects are possible with persistent exposure. Very high and severe pollution levels can mildly or significantly aggravate the symptoms to people with heart or reparatory illness. Healthy people may experience irritation to the eyes, wheezing, coughing and sore throats.

More on what the API revealshttp://www.epd-asg.gov.hk/english/api_you/apitell.html

Monitoring Stations

Pollution levels are continuously measured by the Environmental Protection Department's air quality monitoring network, which includes 11 general and 3 roadside monitoring stations. The general stations are located in different parts of Hong Kong to cover various kinds of land use areas. They are usually at roof level of four to six storeys high. The roadside stations are located at street level in Causeway Bay, Mong Kok and Central. All stations are built and operated to comply with the highest international standards of accuracy.

Map showing locations of general and roadside monitoring stationshttp://www.epd-asg.gov.hk/english/current/current.html
How to determine the type of monitoring most relevant to youhttp://www.epd-asg.gov.hk/english/api_you/which.html

Data and Statistics

Data collected from the monitoring stations is recorded by the Environmental Protection Department and turned into useful information for you in the following ways.

The current API reading is available 24 hours a day, seven days a week.

Current APIhttp://www.epd-asg.gov.hk/eindex.html

An API forecast is also available to provide alerts for pollution episodes.

API forecasthttp://www.epd-asg.gov.hk/english/forecast/forecast.html

API readings of the past 24 hours are available for those who wish to enquire further.

API for the past 24 hourshttp://www.epd-asg.gov.hk/english/24api/24api.html

The pollutant concentration at each monitoring station is available for the last 24 hours.

Pollutant concentration for the past 24 hourshttp://www.epd-asg.gov.hk/english/24pollu/24pc.html

API statistical summaries have been published since 1999. The most current record is 2 months lagging behind.

Monthly API summarieshttp://www.epd-asg.gov.hk/english/apisum/apisum.html

More detailed hourly API records are also available by month back to mid-1999. From mid-1999 back to 1995, the API records are daily. The most current record is 2 months lagging behind.

Past API recordhttp://www.epd-asg.gov.hk/english/pastapi/pastapie.html

Aside from these online resources, API information is broadcast on radio and television, and printed in local newspapers. You can also call the API Hotline at (852) 2827-8541 if you would like to obtain information by telephone.

Other Information

Here provides links to the monitoring bodies of other countries so you can learn more about air pollution around the world, and what is being done about it.