Vol.5_What is the air quality index AQI? What does it have to do with PM2.5, which we often hear?

Do you often hear the air quality indicator AQI, but don’t know what it means?
Do you often hear the air quality indicator AQI, but don’t know what it means? Or in the lower right corner of the news station, if you see green, yellow, or red air levels, what does it mean? Today’s article will introduce you to AQI and understand the air quality indicators currently used in Taiwan!

[Air quality AQI: six pollutant indicators that have an impact on the human body]
The air quality index AQI is an air quality monitoring standard implemented by the government in December 2016. The measured pollution items include six types, namely ozone (O3), fine suspended particulates (PM2.5), suspended particulates (PM10), For carbon monoxide (CO), sulfur dioxide (SO2) and nitrogen dioxide (NO2), the impact of different pollutants on human health is converted into sub-index values ​​respectively, and then the maximum value of each sub-indicator on that day is used as the measurement station for that day. Air Quality Index (AQI).
For example, if today's PM2.5 is less than 15.4, falling in the "good" green range, but the hourly average of O3 is 0.166, falling in the "unhealthy for all groups" red range, then the AQI will be the highest values, shown as unhealthy red intervals for all groups, to ensure that we do not ignore the impact of other pollutants by focusing on a single pollutant indicator.
AQI divides air quality into six levels from good green to hazardous brown. When you see orange, people with allergies need to start paying attention. If it reaches the red level, everyone should pay special attention and minimize outdoor activities. Or wear a mask when going out and other measures to prevent air pollution!
Comparison table of pollutant concentration and sub-indicators of pollution (data source: Environmental Protection Agency, Executive Yuan):

[What is the difference between AQI and the often heard PM2.5? The evolution of Taiwan’s air pollution indicators]
Before the implementation of AQI, our country actually used two indicators, PSI and PM2.5, in parallel. That is to say, we often hear "purple burst". What does this mean?
Among air pollutants, dust-like particles are called "suspended particles", and the particles with a diameter of less than or equal to 2.5 microns are PM2.5, also known as "fine suspended particles." How small is PM2.5? For example, the diameter of human hair is 60 microns, and 2.5 microns is 1/28 of the hair. Such small particles floating in the atmosphere may be toxic substances such as sulfates, nitrates, and ammonium salts, or may be attached with dioxin , heavy metals and other substances enter the body through the respiratory system and through the alveolar and arterial blood exchange. In such a situation for a long time, it will not only cause severe allergies and even asthma; in severe cases, it will also increase the chance of cardiovascular disease and lung disease. The World Health Organization (WHO) even recognizes PM2.5 as a first-level carcinogen!
PM2.5 volume comparison table:

The Environmental Protection Agency implemented two air indicators, PSI and PM2.5, from October 2014 to December 2016, dividing PM2.5 into four color intervals of green, yellow, red, and purple, and then subdivided them into ten Level, "Purple Burst" is the tenth highest level, which means PM2.5 has more than 71 micrograms per cubic meter. Everyone needs to avoid going out as much as possible, and be careful that it may cause discomfort to the eyes, throat, cardiovascular, trachea, etc.
However, PM2.5 fine suspended particulates are not the only pollutants that can cause discomfort to the human body. For example, O3 ozone can also easily irritate the eyes. It is also PM10 suspended particulates that tend to spike when sandstorms strike. Therefore, the public is already familiar with PM2. 5 effects on the human body, the government changed to implement AQI, incorporating six pollutant indicators.
Therefore, PM2.5 is also included in the current AQI, but AQI monitors multiple pollutants more comprehensively and helps us grasp a more complete air quality situation.
[What is Taiwan’s air pollution index AQI like in recent years? 】
Due to Taiwan's industrial development and geographical location, it is easily affected by the air quality of neighboring countries. In recent years, the issue of air pollution has attracted much attention from society. So what is the actual air pollution situation in Taiwan?
Judging from the 2016 annual report of the Environmental Protection Agency of the Executive Yuan, the average air quality in 2016 fell between 51-100 "fair" and 0-50 "good", reaching 101-150 "unhealthy for sensitive groups" The ratio for "unhealthy for all groups" is 15.02, which is equivalent to about 10 days in a 365-day year, while the ratio for "very unhealthy" for 201-300 is 0.04, which is equivalent to 1.5 days.

Judging from the trend, when the air quality index exceeds 100, the ratio has been declining year by year in the past four years, while the ratio between 50 and 100 has an increasing trend.

Generally speaking, Taiwan's air quality mostly falls in the good to average range, but special attention needs to be paid to the fact that Taiwan is susceptible to the influence of China's haze during the northeast monsoon, and the diffusion in leeward areas is poor, so winter and spring are our This is the season when you need to pay special attention to air pollution conditions.

The air pollution index has been integrated from the dual items of PSI and PM2.5 into a unified AQI, and is distinguished by color, so that we can see it clearly at a glance. Next time you hear AQI or see the color level, you can Know what the air condition is like that day, choose an appropriate activity space, and take protective measures!