Air Pollution Index
Encyclopedia
The Air Pollution Index (API) is a simple and generalized way to describe the air quality in mainland China
, Hong Kong
and Malaysia. It is calculated from several sets of air pollution data.
(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)
(EPD). Moreover, the EPD makes forecast on the API for the following day everyday.
The API is based on the level of 6 atmospheric pollutants, namely sulfur dioxide
(SO2), nitrogen dioxide
(NO2), suspended particulates, carbon monoxide
(CO), ozone
(O3), lead
(Pb), measured at all the monitoring stations throughout the territory.
There are 11 General Stations and 3 Roadside Stations. The former includes Central / Western
, Eastern
, Kwai Chung
, Kwun Tong
, Sha Tin
, Sham Shui Po
, Tai Po
, Tap Mun
, Tsuen Wan
, Tung Chung
, and Yuen Long
; the later Causeway Bay
, Central
, and Mong Kok
.
In Hong Kong, there are two types of API: General API and Roadside API. The EPD reports the latest APIs hourly.
The index and the air quality objectives were set in 1987; and pollutant levels are measured over varying periods, in μg
/m3. There are hourly, 24 hour and annual targets for sulfur dioxide and nitrogen dioxide, and 24 hour and annual targets for particulates.
The table below shows the official Health Implications of the respective API levels in Hong Kong.
In 1998, the Education Bureau's recommended schools to curtail outdoor activities when the index reached 200, whereas leading healthcare advocates are urging that the level be revised to 100. The World Health Organisation revised its air quality guideline levels of sulfur dioxide, nitrogen dioxide and ozone in 2006 in light of new scientific evidence. The WHO also introduced new measurement guidelines for very small particulates which are more dangerous to pulmonary function. At the '200' level, Hong Kong levels of SO2 (800μg/m3) and NO2 (1,130μg/m3) are 40 times and 5½ times WHO guidelines respectively; the equivalent for particulates (350μg/m3) is 7 times WHO guidelines.
This scale below shows the Health classifications used by the Malaysian government.
If the API exceeds 500, a state of emergency is declared in the reporting area. Usually, this means that non-essential government services are suspended, and all ports in the affected area are closed. There may also be a prohibition on private sector commercial and industrial activities in the reporting area excluding the food sector.
Mainland China
Mainland China, the Chinese mainland or simply the mainland, is a geopolitical term that refers to the area under the jurisdiction of the People's Republic of China . According to the Taipei-based Mainland Affairs Council, the term excludes the PRC Special Administrative Regions of Hong Kong and...
, Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...
and Malaysia. It is calculated from several sets of air pollution data.
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 dioxideSulfur dioxide
Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...
(SO2), nitrogen dioxide
Nitrogen dioxide
Nitrogen dioxide is the chemical compound with the formula it is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent...
(NO2), suspended particulates (PM10), carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
(CO), and ozone
Ozone
Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...
(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. |
Hong Kong
The API has been in use in Hong Kong since June 1995. It is measured and updated hourly by the Environmental Protection DepartmentEnvironmental Protection Department
Environmental Protection Department is a department of Hong Kong Government concerning the issues of environmental protection in Hong Kong.-History:...
(EPD). Moreover, the EPD makes forecast on the API for the following day everyday.
The API is based on the level of 6 atmospheric pollutants, namely sulfur dioxide
Sulfur dioxide
Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...
(SO2), nitrogen dioxide
Nitrogen dioxide
Nitrogen dioxide is the chemical compound with the formula it is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent...
(NO2), suspended particulates, carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
(CO), ozone
Ozone
Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...
(O3), lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
(Pb), measured at all the monitoring stations throughout the territory.
There are 11 General Stations and 3 Roadside Stations. The former includes Central / Western
Central and Western District
The Central and Western District located on northern part of Hong Kong Island is one of the 18 administrative districts of Hong Kong. It had a population of 261,884 in 2001...
, Eastern
Eastern District, Hong Kong
The Eastern District is one of the 18 districts of Hong Kong. It had a population of 587,690 in 2006. The district has the second highest population while its residents have the third highest median household income among 18 districts....
, Kwai Chung
Kwai Chung
Kwai Chung is a town in the New Territories of Hong Kong. Together with Tsing Yi Island, it is part of the Kwai Tsing District of Hong Kong. Kwai Chung is the site of the container port. It is also part of Tsuen Wan New Town. In 2000, it had a population of 287,000...
, Kwun Tong
Kwun Tong
Kwun Tong is an area in Kwun Tong District, situated at the eastern part of the Kowloon Peninsula, and its boundary stretches from Lion Rock in the north to Lei Yue Mun in the south, and from the winding paths of Kowloon Peak in the east to the north coast of the former Kai Tak Airport runway in...
, Sha Tin
Sha Tin
Sha Tin, also spelled Shatin, is an area around the Shing Mun River in the New Territories of Hong Kong. Administratively, it is part of the Sha Tin District.-Geography:...
, Sham Shui Po
Sham Shui Po
Sham Shui Po, or Shamshuipo, is an area of Sham Shui Po District, Hong Kong, situated in the northwestern part of the Kowloon Peninsula, north of Tai Kok Tsui, east of Cheung Sha Wan and south of Shek Kip Mei. Sham Shui Po is known for its street market for electronic devices.-History:Sham Shui Po...
, Tai Po
Tai Po
Tai Po is an area in the New Territories of Hong Kong. It refers to the vicinity of the traditional market towns in the area presently known as Tai Po Old Market or Tai Po Kau Hui and the Tai Wo Town on the other side of the Lam Tsuen River, near the old Tai Po Market Station of the...
, Tap Mun
Tap Mun
Grass Island or Tap Mun is an island in Hong Kong, located in the northeastern part of the territory. Its area is 1.69 km². Administratively, it is part of the Tai Po District. There are about 100 people living on the island.-Location:...
, Tsuen Wan
Tsuen Wan
Tsuen Wan is a bay in the Kowloon area of Hong Kong, opposite to Tsing Yi Island across Rambler Channel. The market town of Tsuen Wan emerged for the surrounding villages and fleets of fishing boats in the area. The town is around the present-day Tsuen Wan Station of the MTR...
, Tung Chung
Tung Chung
Tung Chung, meaning 'eastern stream', is an area situated on the north-western coast of Lantau Island in Hong Kong. Tung Chung, currently one of the latest generation of new towns, was formerly a rural village around Tung Chung Wan, and along the delta and lower courses of Tung Chung River and Ma...
, and Yuen Long
Yuen Long
Yuen Long , formerly Un Long, is an area and town located in the northwest of Hong Kong, on the Yuen Long Plain. To its west lie Hung Shui Kiu and Ha Tsuen, to the south Shap Pat Heung and Tai Tong, to the east Au Tau and Kam Tin, and to the north Nam Sang Wai.-Name:The Cantonese name Yuen Long 元朗...
; the later Causeway Bay
Causeway Bay
Causeway Bay is a heavily built-up area of Hong Kong, People's Republic of China, located on the Hong Kong Island, and covering parts of Wan Chai and Eastern districts. The Chinese name is also romanized as Tung Lo Wan as in Tung Lo Wan Road...
, Central
Central, Hong Kong
Central is the central business district of Hong Kong. It is located in Central and Western District, on the north shore of Hong Kong Island, across Victoria Harbour from Tsim Sha Tsui, the southernmost point of Kowloon Peninsula...
, and Mong Kok
Mong Kok
Mong Kok , less often known as Argyle , is an area in the Yau Tsim Mong District on Kowloon Peninsula, Hong Kong...
.
In Hong Kong, there are two types of API: General API and Roadside API. The EPD reports the latest APIs hourly.
The index and the air quality objectives were set in 1987; and pollutant levels are measured over varying periods, in μg
Microgram
In the metric system, a microgram is a unit of mass equal to one millionth of a gram , or 1/1000 of a milligram. It is one of the smallest units of mass commonly used...
/m3. There are hourly, 24 hour and annual targets for sulfur dioxide and nitrogen dioxide, and 24 hour and annual targets for particulates.
The table below shows the official Health Implications of the respective API levels in Hong Kong.
| API | | Air Pollution Level | Health Implications; |
|---|---|---|
| 0 - 25 | Low | Not expected. |
| 26 - 50 | Medium | Not expected for the general population. |
| 51 - 100 | High | Acute health effects are not expected but chronic effects may be observed if one is persistently exposed to such levels. |
| 100 - 200 | Very High | People with existing heart or respiratory illnesses may 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 may experience significant aggravation of their symptoms. There may also be widespread symptoms in the healthy population (e.g. eye irritation, wheezing, coughing, phlegm and sore throats). |
In 1998, the Education Bureau's recommended schools to curtail outdoor activities when the index reached 200, whereas leading healthcare advocates are urging that the level be revised to 100. The World Health Organisation revised its air quality guideline levels of sulfur dioxide, nitrogen dioxide and ozone in 2006 in light of new scientific evidence. The WHO also introduced new measurement guidelines for very small particulates which are more dangerous to pulmonary function. At the '200' level, Hong Kong levels of SO2 (800μg/m3) and NO2 (1,130μg/m3) are 40 times and 5½ times WHO guidelines respectively; the equivalent for particulates (350μg/m3) is 7 times WHO guidelines.
Malaysia
Similar to Hong Kong, the air quality in Malaysia is reported as the API or Air Pollution Index. Four of the index's pollutant components (i.e., carbon monoxide, ozone, nitrogen dioxide and sulfur dioxide) are reported in ppmv but PM10 particulate matter is reported in μg/m3.This scale below shows the Health classifications used by the Malaysian government.
- 0-50 Good
- 51-100 Moderate
- 101-200 Unhealthy
- 201-300 Very unhealthy
- 301- Hazardous
If the API exceeds 500, a state of emergency is declared in the reporting area. Usually, this means that non-essential government services are suspended, and all ports in the affected area are closed. There may also be a prohibition on private sector commercial and industrial activities in the reporting area excluding the food sector.
See also
- Air pollutionAir pollutionAir pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere....
- Air Quality IndexAir Quality IndexAir quality is defined as a measure of the condition of air relative to the requirements of one or more biotic species or to any human need or purpose. Air quality indices are numbers used by government agencies to characterize the quality of the air at a given location...
- Air Quality Health IndexAir Quality Health IndexThe Air Quality Health Index or is a scale designed to help understand the impact of air quality on health. It is a health protection tool used to make decisions to reduce short-term exposure to air pollution by adjusting activity levels during increased levels of air pollution...
- Atmospheric dispersion modelingAtmospheric dispersion modelingAtmospheric dispersion modeling is the mathematical simulation of how air pollutants disperse in the ambient atmosphere. It is performed with computer programs that solve the mathematical equations and algorithms which simulate the pollutant dispersion...
- Emission standardEmission standardEmission standards are requirements that set specific limits to the amount of pollutants that can be released into the environment. Many emissions standards focus on regulating pollutants released by automobiles and other powered vehicles but they can also regulate emissions from industry, power...
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