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Table 2 AQI classes of China’s Ministry of Environmental Protection

From: Air quality forecasting based on cloud model granulation

Range AQI class Class description
0–50 1 Excellent, no health implications.
51–100 2 Good, few hypersensitive individuals should reduce outdoor exercise.
101–150 3 Slight pollution, slight irritations may occur, individuals with breathing or heart problems should reduce outdoor exercise.
151–200 4 Moderate pollution, slight irritations may occur, individuals with breathing or heart problems should reduce outdoor exercise.
201–300 5 Heavy pollution, healthy people will be affected significantly. People with breathing or heart problems will experience reduced endurance in activities. These individuals and elders should remain indoors and restrict activities.
300+ 6 Severe pollution, the endurance of healthy people in activities will decrease. There may be strong irritation symptoms that may cause other diseases. The old and the sick should stay indoors to avoid exercise. Healthy should avoid outdoor activities.