Beijing actually shows on the post.

Your comment stimulated me to dig into this deeper. The Chinese can make their air quality appear "good" simply by calling it so. The air quality data they present would if rated in the United Kingdom rate off their health scale. The respective health descriptors are:

China: Daily activities not be affected See Chinese Health Effects
United Kingdom: The effects on sensitive individuals described for 'High' levels of pollution may worsen.--> High Levels: Significant effects may be noticed by sensitive individuals and action to avoid or reduce these effects may be needed (e.g. reducing exposure by spending less time in polluted areas outdoors). Asthmatics will find that their 'reliever' inhaler is likely to reverse the effects on the lung. See UK Health Effects

One makes this comparison by applying the API for Particulate Matter (PM) in Beijing. In this example an index of 100 API for PM was reported by the Chinese. This API correlates to a PM(10) of 0.150 milligrams per cubic meter, or equivalently for the UK scale 150 micro grams per cubic meter. When one transfers this PM concentration on the United Kingdom health index scale, one can see it falls above the maximum health hazard index of 130 micro grams per cubic meter. Thus there is a discrepency of approximately 3 orders of magnitude between the criteria for clean air in China versus the United Kingdom.