Chengdu experiences significant air pollution, particularly during the winter months from October to March, when smog becomes a frequent issue due to the city's location in the Sichuan Basin; the surrounding mountains trap pollutants, causing them to settle for longer periods compared to coastal cities. During these peak pollution months, the Air Quality Index (AQI) often reaches levels classified as Poor or Unhealthy (100-200+), characterized by high concentrations of PM2.5 and PM10 that can cause respiratory irritation. However, air quality has shown steady improvement since 2013 due to government mitigation efforts, and the city enjoys much clearer skies and more moderate AQI levels during the spring and summer. While the city's rapid industrial growth, increasing population, and heavy construction contribute to its ranking among the more polluted global cities, the most severe "hazardous" days are becoming less frequent, and residents often utilize air purifiers and masks to manage health risks during the gray, damp winter season.