| thick smog | 1.51 | Imagine smog so thick you could cut it with a knife. | ||
| choking smog | 0.99 | Crushed cars, cleaner air, Beijing moves to clear up choking smog. | ||
| urban smog | 0.72 | Urban smog has a pulverized radiance. | ||
| heavy smog | 0.66 | Traffic restricted in Paris due to heavy smog. | ||
| worst smog | 0.39 | Last summer, for the first time, Houston overtook Los Angeles for having the worst smog. | ||
| dense smog | 0.33 | In Taipei, the capital, dense smog is a daily nightmare for millions of people. | ||
| dangerous smog | 0.26 | The dangerous smog conditions are expected to last through late Wednesday. | ||
| high smog | 0.26 | Acadia National Park, in Maine, downwind from Boston, continues to record very high smog levels. |