The website AirVisual.com impressively shows the actual situation of the air pollution (PM 2,5) and wind directions worldwide. It does so in real-time, based on current measurements.
It is important to know about the air quality - in Amsterdam the situation has worsened lately (influenced by the weather conditions). According to a ranking by the world health organization WHO, Amsterdam is equally placed with cities like Rome and Berlin among European cities, if we look at particulated matter. But those levels are still relatively low if we compare cities on a worldwide scale.
A good overview of the situation is offered in this article in The Guardian, part of a very good series about air quality in our cities. From this information we can learn that the situation is worst in Iran, India, Saudi Arabia and China. In Europa these are Macedonia, Bosnia-Herzegovina and Poland, but if we include Turkey, a number of cities from this country are positioned in the top-10.