Air Quality Index differences between American and Chinese standards

First, what is the Air quality index

Air Quality index (air quality index, or AQI) is a numerical value used to quantitatively describe the level of air quality. The AQI value range is located between 0–500.

There are many types of ambient air pollutants, such as sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), ozone (O3) and suspended particulate matter. In suspended particulate matter, the diameter is less than or equal to 10μm called PM10, and the diameter is less than or equal to 2.5μm called PM2.5. Among them, the current stage of people's health impact of the largest number of PM2.5. It is precisely because of the awareness of the serious harm of PM2.5, China issued in 2012, will be implemented on January 1, 2016, the national standard GB 3095-2012 "Environmental Air Quality Standards" (1), added to the PM2.5 monitoring requirements and set the concentration limit value.

The air quality report released daily by the Environmental Monitoring Department will contain the concentration values of various pollutants, such as SO2 concentration of 20.5μg/m3, PM10 concentration of 150.8μg/m3, PM2.5 concentration of 130.7μg/m3 and so on. However, it is difficult to determine from such a number of abstract concentration data what the current level of air quality is. So someone came up with a way to convert the different levels of pollutants into a single index, which is the air quality index.

The air quality index values in different intervals represent different air quality levels. For example, between 0–50, representing "good", 51–100, representing "medium", between 101–150, representing "unhealthy for sensitive people" ... Wait a minute. For more intuitive purposes, each interval has a fixed color value corresponding to it:

In this way, the air quality level can be intuitively judged by the AQI value of the report, or even by looking at the color.

Second, how the air quality index in China is calculated

The Air quality index is calculated based on the concentration values of various pollutants. To calculate AQI, the concentration limits of each pollutant at different air quality levels need to be determined beforehand.

The analysed by sub and aqi of pollutants can be calculated by using this formula and the specified range in the table.

When the pollutant concentration exceeds the maximum limit, the AQI value is only 500, because there is no index above it. In this case, called "Beyond" or "index", that is, the air quality index has been unable to describe the bad air quality. In the first few days of writing, Beijing's air pollution, some mobile phone applications show AQI value of more than 500, reached more than 700, this is actually not correct, at least not rigorous.

Iii. how the U.S. Air Quality index is calculated

Pollutant restriction form:

Iv. differences in air quality index between China and the United States

Chinese and American standards are the same in the above-mentioned levels, but at a lighter level, the US is more stringent. China PM2.5 is good, the United States may be moderate pollution.

Because of the difference in the setting of PM2.5 concentration limits, the calculated PM2.5 index is naturally different. For example, assuming that the PM2.5 concentration is 35μg/m3, the formula calculates that China's PM2.5 index is 50 and the US PM2.5 index is 99. If the main air pollutants at that time were PM2.5, then China's air quality index is 50, which belongs to the first grade, the United States Air Quality Index is 99, belongs to the two grade good.

China is now in a period of rapid industrial development, although the country is vigorously making haze, but it is not 35 days can be achieved. China's PM2.5 standard has just hit the road, is the most relaxed transition standard, so high quality air quality does not mean that the air is completely healthy and pollution-free, we still use the U.S. standards to strictly treat the air around, do a good job of prevention.

Air Quality Index differences between American and Chinese standards